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Agilent 7890 Series Chromatograph Troubleshooting Guide PDF

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Summary of Content for Agilent 7890 Series Chromatograph Troubleshooting Guide PDF

Agilent 7890 Series Gas Chromatograph

Troubleshooting

Agilent Technologies

Notices Agilent Technologies, Inc. 2015

No part of this manual may be reproduced in any form or by any means (including electronic storage and retrieval or translation into a foreign language) without prior agreement and written consent from Agilent Technologies, Inc. as governed by United States and international copyright laws.

Manual Part Number G3430-90053

Edition Third edition, October 2015 Second edition, December 2013 First edition, January 2013

Printed in USA

Agilent Technologies, Inc. 2850 Centerville Road Wilmington, DE 19808-1610 USA

412 800820 3278

Warranty The material contained in this document is provided as is, and is subject to being changed, without notice, in future editions. Further, to the maximum extent permitted by applicable law, Agilent disclaims all warranties, either express or implied, with regard to this manual and any information contained herein, including but not limited to the implied warranties of merchantability and fitness for a particular purpose. Agilent shall not be liable for errors or for incidental or consequential damages in connection with the furnishing, use, or performance of this document or of any information contained herein. Should Agilent and the user have a separate written agreement with warranty terms covering the material in this document that conflict with these terms, the warranty terms in the separate agreement shall control.

Safety Notices

CAUTION A CAUTION notice denotes a hazard. It calls attention to an operating procedure, practice, or the like that, if not correctly performed or adhered to, could result in damage to the product or loss of important data. Do not proceed beyond a CAUTION notice until the indicated conditions are fully understood and met.

WARNING A WARNING notice denotes a hazard. It calls attention to an operating procedure, practice, or the like that, if not correctly performed or adhered to, could result in personal injury or death. Do not proceed beyond a WARNING notice until the indicated conditions are fully understood and met.

Contents 1 Concepts and General Tasks

Agilent 7890 Series Troubleshooting

Concepts 10 How to troubleshoot using this manual 10 The [Status] key 10 Error conditions 11

Systems Configured for Enhanced Communications 12

Configurable Items to Always Keep Current 13 Inlet and detector configuration 13 Column configuration 13 Automatic Liquid Sampler configuration 14 Gas configuration 14

To View the Run Log, Maintenance Log, and Event Log 15 Run Log 15 Maintenance Log 15 Event Log 15

Information to Obtain Before Calling Agilent for Service 16

2 ALS and Detector Symptoms

Plunger Errors 18

Procedure 18

Vial Mishandled by ALS (7693A) 19

Alignment Light on 7693A/7650A Injector Tower is On 21

Vial Mishandled by ALS (7683) 22

Alignment Light on 7683B Injector Tower is On 24

Syringe Needle Bends During Injection into Inlet 25

FID Fails Leakage Current Test 26 Possible causes 26 Procedure 26

NPD Fails Leakage Current Test 27

FID Fails Baseline Test 28

To Resolve Low Sensitivity with an FID 29

FID Does Not Ignite 30

FID Ignitor Does Not Glow During Ignition Sequence 31

3

4

Corrosion in FID Collector and Ignitor Glow Plug 33

FPD Does Not Ignite 34

NPD Adjust Offset Process Fails 36

NPD Bead Will Not Ignite 37

FPD+ Temperature Will Not Become Ready 38

Blinking Not Ready Light: Detector Hardware Fault/TCD Filament Voltage 39

Shutdown (Defective) Device 40

3 Chromatographic Symptoms

Retention Times Not Repeatable 42

Peak Areas Not Repeatable 43

Contamination or Carryover 44 Isolate the source 44 Check possible causesall inlet and detector combinations 44

Larger Peaks Than Expected 47

Peaks Not Displayed/No Peaks 48

Baseline Rise During Oven Temperature Program 50

Poor Peak Resolution 51

Peak Tailing 52 NPD Peak Tailing 53

Peak Boiling Point or Molecular Weight Discrimination Poor 54 For any inlet operating in split mode with any detector 54 For any inlet operating in splitless mode with any detector 54

Sample Decomposition in Inlet/Missing Peaks 55

Peak Fronting 56

Noisy Detector, Including Wander, Drift, and Baseline Spikes 57 Noisy baseline 57 Baseline wander and drift 59 Baseline spiking 60

Microcell Electron Capture Detector (uECD) Noise and Sensitivity 63 Display signal evaluation 63 Sensitivity 65 Contamination (high baseline) 66

Agilent 7890 Series Troubleshooting

Agilent 7890 Series Troubleshooting

Low Peak Area or Height (Low Sensitivity) 67 To Resolve Low Sensitivity with an FID 68

FID Flame Goes Out During a Run and Attempts to Reignite 70

FID Baseline Output Above 20 pA 72

FID Baseline Output at Maximum (~8 Million) 73

FPD Flame Goes Out During a Run and Attempts to Reignite 74

FPD Quenching/Repeatability 75

FPD Output Too High or Too Low 76

FPD Low Peak Areas 77

FPD Large Peak Width at Half-Height 78

FPD Baseline Output High, > 20 pA 79

NPD Solvent Quenching 80

NPD Response Low 81

NPD Baseline Output > 8 million 83

NPD Adjust Offset Process Not Functioning Properly 84

NPD Low Selectivity 85

Negative Peaks Seen with TCD 86

TCD Baseline Has Dampened Sinusoidal Noise Trailing Peaks (Ringing Baseline) 87

TCD Peaks Have Negative Dip on Tail 88

4 GC Not Ready Symptoms

GC Never Becomes Ready 90

Flow Never Becomes Ready 91

Oven Temperature Never Cools Down/Cools Very Slowly 92

Oven Never Heats Up 93

Temperature Never Becomes Ready 94

Cannot Set a Flow or Pressure 95

A Gas Does Not Reach Setpoint Pressure or Flow 96

A Gas Exceeds Pressure Setpoint or Flow 97

The Inlet Pressure or Flow Fluctuates 98

Cannot Maintain a Pressure as Low as the Setpoint on a Split Inlet 99

5

6

The Measured Column Flow Does Not Equal the Displayed Flow 100

FID Does Not Ignite 101

FID Ignitor Does Not Glow During Injection Sequence 102

FID or NPD Measured Hydrogen and Makeup Gas Flows Much Less Than Setpoint 104

NPD Adjust Offset Process Fails 105

FPD Does Not Ignite 106

Valve Not Ready 108 External valves 108 Gas sampling valves 108 Multiposition valve 108

Blinking Not Ready Light: Detector Hardware Fault/TCD Filament Voltage 109

5 Shutdown Symptoms

Column Shutdowns 112

Hydrogen Shutdowns 114 Hydrogen used in inlets and auxiliary gas streams 114 Hydrogen sensor 115

Detector Air Shutdowns 116

7890B MS Shutdown 117 Clearing an MS Shutdown 118 After resolving an MS Shutdown 118

Thermal Shutdowns 119

6 GC Power On and Communication Symptoms

GC Does Not Turn On 122

PC Cannot Communicate with GC 123

GC Cannot Communicate with a Configured MS or HS 124

GC Does Not Recover After Firmware Update 125

GC Turns On, Then Stops During Startup (During Self-Test) 126

Agilent 7890 Series Troubleshooting

7 Checking for Leaks

Agilent 7890 Series Troubleshooting

Leak Check Tips 128

To Check for External Leaks 129

To Check for GC Leaks 131

Leaks in Capillary Flow Fittings 132

To Perform an Inlet Leak Check 133 To set warning limits for a leak check 135 To disable a warning limit for the inlet leak check 135

To Check for Leaks in a Split/Splitless Inlet 136 Cannot Reach Pressure Setpoint 136 Low Sensitivity or Poor Repeatability 137

To Perform a SS Pressure Decay Leak Test 138 To perform a SS inlet pressure decay test at the GC keyboard 138

To Correct Leaks in the Split Splitless Inlet 143

To Check for Leaks in a Multimode Inlet 144 Cannot Reach Pressure Setpoint 144 Low Sensitivity or Poor Repeatability 145

To Perform a MMI Pressure Decay Test 146 To Perform a Multimode Inlet Pressure Decay Test 146

To Correct Leaks in the Multimode Inlet 150

To Perform a PP Pressure Decay Leak Test 151 To Perform a PP Inlet Pressure Decay Test 151

To Correct Leaks in the Packed Column Inlet 155

To Perform a COC Pressure Decay Leak Test 156 To Perform a COC Pressure Decay Test 156

To Correct Leaks in the Cool On-Column Inlet 160

To Perform a PTV Pressure Decay Test 161 To Perform a PTV Pressure Decay Test 161

To Correct Leaks in the PTV Inlet 165

To Perform a VI Pressure Decay Test 166 To Perform a VI Pressure Decay Test 166

To Prepare the VI for a Closed System Leak Check 170

To Correct Leaks in the Volatiles Interface 171

7

8 Troubleshooting Tasks

8

To Measure a Column Flow 174 Measuring FID, TCD, uECD, and FPD column flow 174 Measuring NPD column flow 176

To Measure a Split Vent or Septum Purge Flow 178

To Measure a Detector Flow 180 Measuring FID, TCD, uECD, and FPD flows 180 Measuring NPD flows 183

To Perform the GC Self-Test 185

To Check or Monitor Split Vent Line Backpressure 186 To set a warning limit for the inlet trap check 186 To disable a warning limit for the inlet trap check 188

To Run the Inlet Trap Check 189

To Perform a SS Split Vent Restriction Test 191

To Check a Split Vent Line for Contamination 192

To Adjust the FID Lit Offset 194

To Verify That the FID Flame Is Lit 195

To Verify FID Ignitor Function During Ignition Sequence 196

To Measure FID Leakage Current 197

To Measure FID Baseline Output 198

To Isolate the Cause of FID Noise 199

To Measure NPD Leakage Current 200

To Check for a Plugged FID Jet 201

To Check for a Plugged NPD Jet 202

To Verify That the NPD Bead Is Ignited 203

To Verify That the FPD Flame Is Lit 204

To Adjust the FPD Lit Offset 205

When to Change Gas Purifiers 206

To Ignore a Devices Readiness State 207

To Use the Stopwatch 208

Agilent 7890 Series Troubleshooting

Agilent 7890 Series Gas Chromatograph Troubleshooting

1 Concepts and General Tasks Concepts 10 Systems Configured for Enhanced Communications 12 Configurable Items to Always Keep Current 13 To View the Run Log, Maintenance Log, and Event Log 15 Information to Obtain Before Calling Agilent for Service 16

9Agilent Technologies

1 Concepts and General Tasks

Concepts

10

This manual provides lists of symptoms and corresponding tasks to perform should you experience errors associated with GC hardware or chromatographic output, GC Not Ready messages, and other common issues.

Each section describes a problem and provides a bulleted list of possible causes for you to troubleshoot. These lists are not intended for use in the development of new methods. Proceed with troubleshooting under the assumption that method(s) are working properly.

This manual also includes common troubleshooting tasks as well as information needed prior to calling Agilent for service.

While this manual describes troubleshooting for 7890 Series GCs in general, when describing GC keyboard usage and firmware features, this manual assumes a 7890B GC using firmware B.02.01. Features that are specific to one GC model only (7890A or 7890B) are noted.

How to troubleshoot using this manual

Use the following steps as a general approach to troubleshooting:

1 Observe the symptoms of the problem.

2 Look up the symptoms in this manual using the Table of Contents or the Search tool. Review the list of possible causes of the symptom.

3 Check each possible cause or perform a test that narrows the list of possible causes until the symptom is resolved.

The [Status] key

Be sure to also use the [Status] and [Info] keys on the GC keypad while using this troubleshooting information. These keys will display additional useful information related to the status of the GC and its components.

Agilent 7890 Series Troubleshooting

Concepts and General Tasks 1

Error conditions

Agilent 7890 Series Troubleshooting

If a problem occurs, a status message appears. If the message indicates broken hardware, more information may be available. Press the applicable component key (for example, [Front Det], [Oven], or [Front Inlet]).

11

1 Concepts and General Tasks

Systems Configured for Enhanced Communications

12

When configured with other instruments that support enhanced communications, such as a 5977 MSD, 7000C Triple Quadrupole MS, and 7697 Headspace Sampler, the 7890B GC and configured instruments closely interact with each other. In addition to simply sending start run commands and general status information (ready or not ready), the instruments change their settings based on each others status. For example:

A GC shutdown may cause an MS to shut down or otherwise protect itself.

Venting an MS causes changes in the GC to support the venting process.

An MS shutdown may cause the GC to change its settings to protect itself and the MS.

A loss of communications between the instruments may causes changes in one or both instruments.

The GC sleep/wake cycle triggers the MS and HS sleep/wake cycle (if available).

A configured headspace sampler determines its timings based on the loaded GC method.

Because of this interaction, always check the displays on all instruments and in the data system to learn the complete system status. In general, the GC display will present configured instrument status messages as well as its own messages.

Agilent 7890 Series Troubleshooting

Concepts and General Tasks 1

Configurable Items to Always Keep Current

Agilent 7890 Series Troubleshooting

Certain configurable items in the GC must always be kept current. Failure to do so will lead to reduced sensitivity, chromatographic errors, and possible safety concerns.

If equipped with the optional G3494A or G3494B Barcode Reader accessory (7890B only), you can directly scan parts data (column, liner and ALS syringe information) into the GC without having to type it into the GC at the keypad.

Inlet and detector configuration

Be sure to configure the GC and all related components to reflect an inlet or detector change. Below are some examples of components to keep current after making changes to the inlet or detector:

Liners: The appropriateness of liner type varies depending on the GC inlet mode, for example split mode versus splitless mode, and the analysis.

FPD filters: The FPD filters require different gas flows to function properly. Configure the flow according to the FPD filter installed (phosphorus versus sulfur).

FID and NPD jets: Use the jet appropriate for the type of column installed (capillary column versus packed column).

NPD bead type: Always configure the NPD bead type. An incorrect type can lead to poor performance or premature bead failure.

Column configuration

Reconfigure the GC every time a column is trimmed or changed. Also verify that the data system reflects the correct column type, length, id, and film thickness. The GC relies on this information to calculate flows. Not updating the GC after altering a column causes incorrect flows, changed or incorrect split ratios, retention time changes, and peak shifts.

13

1 Concepts and General Tasks

Automatic Liquid Sampler configuration

14

Keep the Automatic Liquid Sampler (ALS) configuration up-to-date to ensure proper operation. ALS items to keep current include injector position, installed syringe size, and solvent and waste bottle usage.

Gas configuration

WARNING Always configure the GC appropriately when working with hydrogen. Hydrogen leaks quickly and poses a safety concern if too much of it is released into the air or into the GC oven.

Reconfigure the GC every time the gas type is changed. If the GC is configured to a gas other than what is actually being plumbed, incorrect flow rates will result.

To confirm the gas configuration:

1 Press [Config]. 2 Scroll to the appropriate detector or column item on the

display and press [Enter] to see the type of gas configured.

Agilent 7890 Series Troubleshooting

Concepts and General Tasks 1

To View the Run Log, Maintenance Log, and Event Log

Agilent 7890 Series Troubleshooting

The GC maintains internal event logs, each of which holds up to 250 entries. Use these logs to troubleshoot problems, especially when a message no longer appears on the display.

To access the logs, press [Logs] to toggle to the desired log. The display will indicate the number of entries the log contains. Scroll through the list.

Run Log

For each run, the run log records deviations from the planned method. This log is overwritten at the start of each run. The run log information can be used for Good Laboratory Practice (GLP) standards and can be uploaded to an Agilent data system. When the Run Log contains entries, the Run Log LED lights.

Maintenance Log

The maintenance log contains an entry for each time an Early Maintenance Feedback limit is reached, reset, or changed. The log records details such as the counter item, the counter value, the new counter value, and whether or not the counter was reset (indicating a part replacement). When the maintenance log is full, the GC overwrites entries, beginning with the oldest.

Event Log

The event log records events such as shutdowns, warnings, faults, and GC state changes (start run, stop run, and so forth) that occur during GC operation. When the event log is full, the GC overwrites entries, beginning with the oldest.

15

1 Concepts and General Tasks

Information to Obtain Before Calling Agilent for Service

16

Gather the following information before contacting Agilent for service:

Symptoms

Problem description

Hardware installed and parameters/configuration when the error occurred (sample, supply gas type, gas flow rates, detectors/inlets installed, and so forth)

Any messages that appear on the GC display

Results of any troubleshooting tests you have run

Instrument details. Obtain the following information:

GC serial number, which can be found on a sticker located beneath the keypad on the bottom right corner of the GC.

GC firmware revision (press [Status], then [Clear]) GC power configuration (located on a label on the back

panel of the GC to the left of the GC power cable)

Oven configuration (fast- or slow-heating)

Press the [Status] key to display previous Error, Not Ready, and Shutdown messages.

To obtain service/support contact numbers, see the Agilent Web site at www.agilent.com/chem.

Agilent 7890 Series Troubleshooting

Agilent 7890 Series Gas Chromatograph Troubleshooting

2 ALS and Detector Symptoms Plunger Errors 18 Vial Mishandled by ALS (7693A) 19 Alignment Light on 7693A/7650A Injector Tower is On 21 Vial Mishandled by ALS (7683) 22 Alignment Light on 7683B Injector Tower is On 24 Syringe Needle Bends During Injection into Inlet 25 FID Fails Leakage Current Test 26 NPD Fails Leakage Current Test 27 FID Fails Baseline Test 28 To Resolve Low Sensitivity with an FID 29 FID Does Not Ignite 30 FID Ignitor Does Not Glow During Ignition Sequence 31 Corrosion in FID Collector and Ignitor Glow Plug 33 FPD Does Not Ignite 34 NPD Adjust Offset Process Fails 36 NPD Bead Will Not Ignite 37 FPD+ Temperature Will Not Become Ready 38 Shutdown (Defective) Device 40

17Agilent Technologies

2 ALS and Detector Symptoms

Plunger Errors

18

If the ALS reports a front or back plunger error, check the following possible causes:

The syringe plunger is sticking or is not securely connected to the plunger carrier.

The plunger solenoid is binding.

The plunger carrier encoder is inoperable.

The autoinjector plunger carrier mechanism will not move.

The plunger does not move freely due to sample residue or wear. Install a new syringe, making sure to prime the syringe with solvent before installing.

Procedure

1 Remove the syringe and check it for plunger stickiness or

binding. Replace the syringe if necessary (7693A, 7650A, 7683).

2 Check the viscosity of the sample against the viscosity parameter. Reset the viscosity parameter if necessary.

3 Restart the sequence.

4 If the error occurs again, obtain Agilent service.

Agilent 7890 Series Troubleshooting

ALS and Detector Symptoms 2

Vial Mishandled by ALS (7693A)

Agilent 7890 Series Troubleshooting

Refer to your sampler operating documentation for additional information.

When you find a mishandled sample vial, do the following:

Check for folds or wrinkles in the crimp cap, especially near the neck of the sample vial.

Use Agilent-recommended sample vials.

The figure below shows the critical dimensions for sample vials and microvial inserts to be used with the 7693A ALS system. These dimensions do not make up a complete set of specifications.

Verify the transfer turret is installed if using a G4514A tray.

Check sample labels (if applicable).

Check that they are the correct size.

Verify that the labels do not interfere with the gripper.

Vials are available with a write-on spot for easy marking. If you choose to make and apply your own labels, Agilent Technologies recommends the positioning and maximum label thickness shown in the figure below.

Body Diameter (BD) = 11.7 0.2 Cap Diameter (CD) = BD 1.03 maximum All dimensions in millimeters

CD

BD

33.5 1.5 Vial plus cap height

6.25 0.25

3.7 min.

8.2 0.2

32 0.5

11.7 0.2

25 minimum body height

Maximum height of a capped vial Crimp cap sample vial

19

20

2 ALS and Detector Symptoms

All dimensions in millimeters

Overlap mismatch 1.0 max.

Label skew

26.6 max.

3.6 min.

13.4 minimum No label or tape

16.4 0.5

13.2 maximum Text areas are optional

Text

Bar code Text

12.56 Maximum width measured at overlap

Check that the tray vial racks are clean and snapped into the tray base.

Calibrate the system.

Agilent 7890 Series Troubleshooting

ALS and Detector Symptoms 2

Alignment Light on 7693A/7650A Injector Tower is On

Agilent 7890 Series Troubleshooting

If the Align Mode light is on, first verify that the turret is properly installed. Then, perform the alignment procedure as described in the 7693A Automatic Liquid Sampler Installation, Operation and Maintenance manual or the 7650A Automatic Liquid Sampler Installation, Operation and Maintenance manual.

21

2 ALS and Detector Symptoms

Vial Mishandled by ALS (7683)

22

Refer to your sampler operating documentation for additional information.

When you find a mishandled sample vial, do the following:

Check for folds or wrinkles in the crimp cap, especially near the neck of the sample vial.

Use Agilent-recommended sample vials.

The distance from the vial bottom to the top of the neck should be approximately 28.4 mm.

The bottle neck diameter should be 8.2 0.2 mm. The sampler injector and the tray use clear or amber glass sample vials with crimp caps, or Target DP screw-cap vials. Use amber glass vials for light-sensitive samples. Refer to your Agilent catalog for consumables and supplies for acceptable vial types. Incompatible sample vials cause tray and turret errors.

The figure below shows the critical dimensions for sample vials and microvial inserts to be used with the sampler. These dimensions do not make up a complete set of specifications.

5 minimum

3.7

32 0.5

6.25 0.25

8.2 0.2

11.7 0.2

34.5 maximum

Maximum height of a capped vial

Microvial insert Crimp cap sample vial

All dimensions in millimeters

Agilent 7890 Series Troubleshooting

ALS and Detector Symptoms 2

Agilent 7890 Series Troubleshooting

Verify the transfer turret is installed if using a tray and G2913A injector.

Check sample labels (if applicable).

Check that they are the correct size.

Verify that the labels do not interfere with the gripper.

Vials are available with a write-on spot for easy marking. If you choose to make and apply your own labels, Agilent Technologies recommends the positioning and maximum label thickness shown in the figure below.

Check that the tray vial racks are clean and snapped into the tray base.

If the tray cannot deliver or retrieve vials from a bar code reader:

1 Press [Config]. 2 Scroll to and select Sample tray.

3 Scroll to Grip offset and press [Mode/Type]. 4 Scroll to the desired adjustment (Up, Default, or Down) and

press [Enter]. If the sample vial touches the side of the turret hole as the

vial is raised or lowered, adjust the turret rotation.

For 7683B, adjust the gripper height as follows:

1 Press [Config]. 2 Scroll to and select Sample tray.

3 Scroll to Front injector offset and press [Mode/Type]. 4 Scroll to the desired adjustment (Clock, Counterclock, or

Default) and press [Enter].

All dimensions in millimeters

20.5 1.0

3.6 min. 5.6 0.6

Bar code

Text

No label or tape

No label or tape

0.2

0.44

23

2 ALS and Detector Symptoms

Alignment Light on 7683B Injector Tower is On

24

Refer to the 7683B Automatic Liquid Sampler Installation, Operation and Maintenance manual for additional information.

When the Align Mode light is on, the injector will not operate until the following procedure is performed:

1 When the injector is not operating, open the injector tower door.

2 Slide the syringe carriage up until it stops.

3 Remove the syringe.

4 Carefully remove the needle support assembly from the injector.

5 Use a pen to press the recessed alignment button located above the indicator lights, then close the door.

6 The injector will then go through the following steps:

a The turret rotates to verify that the needle support assembly was removed, then rotates to determine what type of turret is installed.

b The syringe carriage moves all the way down, then moves back up again and clears the turret.

c The syringe carriage steps down until it touches the turret. This sets its position relative to the turret.

d The plunger moves to calibrate six stops. Observe each of the six steps to verify the plunger loop is functioning properly. If it is missing stops, send the injector to Agilent for repair.

7 When the alignment is complete, the Ready light turns on and the sampler returns to the ready state. Install the needle support assembly and syringe.

Agilent 7890 Series Troubleshooting

ALS and Detector Symptoms 2

Syringe Needle Bends During Injection into Inlet

Agilent 7890 Series Troubleshooting

WARNING When troubleshooting the injector, keep your hands away from the syringe needle. The needle is sharp and may contain hazardous chemicals.

Refer to your ALS documentation for additional information:

7683B Automatic Liquid Sampler Installation, Operation and Maintenance

7693A Automatic Liquid Sampler Installation, Operation and Maintenance

7650A Automatic Liquid Sampler Installation, Operation and Maintenance

Check that the GC septum nut is not too tight.

Check that the syringe is installed correctly into the syringe carriage.

Check that the needle support and guide are clean. Remove any residue or septum deposits. Install a new needle support assembly (7683) or needle support foot (7693A or 7650A) if necessary.

If using the cool on-column inlet, check that the correct insert for the syringe is installed. See To Check the Needle-to-Column Size on the COC Inlet for more information.

Check that you are using the proper syringe. The combined length of the syringe barrel and needle should be approximately 126.5 mm.

Check that the sample vial dimensions meet specification. See Vial Mishandled by ALS (7693A) or Vial Mishandled by ALS (7683).

Check that the crimp cap is properly installed. Refer to your sampler documentation.

25

2 ALS and Detector Symptoms

FID Fails Leakage Current Test

26

Possible causes

A failed leakage current test usually indicates misassembly, contamination, or a damaged part.

Procedure

1 If you have just performed maintenance on the FID, first

verify that the detector was reassembled properly before troubleshooting detector problems.

2 Replace the PTFE (FID) for contamination.

3 Make sure that the interconnect spring is not damaged, bent, or dirty. The interconnect spring should be touching the bottom of the collector. If the inteconnect spring is damaged, bent, or dirty, call Agilent for service.

FID interconnect spring

Agilent 7890 Series Troubleshooting

ALS and Detector Symptoms 2

NPD Fails Leakage Current Test

Agilent 7890 Series Troubleshooting

A failed leakage current test usually indicates misassembly, contamination, or a damaged part.

If you have just performed maintenance on the NPD, first verify that the detector was reassembled properly before troubleshooting detector problems.

1 Replace the ceramic insulators. Restest.

2 Set the bead voltage to 0.0 V. Turn off the adjust offset. View the output (leakage current).

3 Remove the bead and store in a safe place.

4 Remove the three screws that secure the lid in place, then remove the lid.

5 Examine the interconnect spring. Make sure that the interconnect spring is not damaged, bent, or dirty. The interconnect spring should be touching the bottom of the collector. If the inteconnect spring is damaged, bent, or dirty, call Agilent for service.

6 If the interconnect spring is not damaged or dirty, and the detector output signal is still high, contact Agilent for service.

Correct

27

2 ALS and Detector Symptoms

FID Fails Baseline Test

28

If you have just performed maintenance on the FID, first verify that the detector was reassembled properly before troubleshooting detector problems.

If the FID fails the baseline test:

Ensure the purity and quality of the gas.

Replace dirty/expended chemical traps.

Bakeout the detector.

Agilent 7890 Series Troubleshooting

ALS and Detector Symptoms 2

To Resolve Low Sensitivity with an FID

Agilent 7890 Series Troubleshooting

See To Resolve Low Sensitivity with an FID.

29

2 ALS and Detector Symptoms

FID Does Not Ignite

30

Verify that the Lit Offset is 2.0 pA.

Ensure that the FID temperature is high enough for ignition (>150 C). Agilent recommends >300 C.

Check that the FID ignitor glows during ignition sequence. (See To Verify FID Ignitor Function During Ignition Sequence.)

Check that the air and hydrogen pressures meet Agilents recommendations (hydrogen > 35 psi [210 kPa] and air > 55 psi [380 kPa]). See the Agilent GC, GC/MS, and ALS Site Preparation Guide.

Try increasing the supply pressures to the FID flow module. This makes the flame easier to light without changing the setpoints.

Increase hydrogen flow and decrease or turn off makeup gas flow until ignition occurs, then reduce them toward the method values. Experiment for the best values.

Increasing hydrogen flow and decreasing makeup flow will help the FID ignite more easily. If it will light under these modified conditions, the cause could be a partially clogged jet, a weak ignitor, or a leak at the column fitting.

Check for a plugged or partially plugged jet. (See To Check for a Plugged FID Jet.)

Measure the FID flow rates. Actual flow rates should be within +/-10% of the setpoint. (See FID starting conditions.) The hydrogen:air ratio greatly impacts ignition. Nonoptimal flow settings can prevent flame ignition. (See To Measure a Detector Flow.)

There could be a large leak in the system if the flame still will not light. Large leaks result in measured flow rates being different from actual flow rates, causing nonideal ignition conditions. Thoroughly leak check the whole system, especially the column fitting at the FID. (See Checking for Leaks).

Check the column flow rate. (See To Measure a Column Flow.) Hydrogen flow should be greater than the sum of the column flow and makeup flow.

If the analysis permits, substitute nitrogen for helium as makeup.

Agilent 7890 Series Troubleshooting

ALS and Detector Symptoms 2

FID Ignitor Does Not Glow During Ignition Sequence

Agilent 7890 Series Troubleshooting

WARNING Keep body parts at a safe distance from the FID chimney while performing this task. If using hydrogen, the FID flame will not be visible.

1 Remove the detector top cover.

2 Turn the FID flame On. 3 Observe the ignitor plug though the FID chimney. The small

hole should glow during ignition sequence.

If the test fails, check for the following possible causes:

The ignitor may be bad; replace the ignitor. (See To Perform Maintenance on the FID Collector Assembly.)

Detector temperature is set to < 150 C. Agilent recommends operating the FID at > 300 C.

The ignitor is not making a good connection to the ground:

The ignitor must be tightly screwed into the FID castle assembly.

The three T-20 Torx screws that hold the collector assembly in place must be tight.

31

32

2 ALS and Detector Symptoms

The brass knurled nut that holds the FID castle assembly in place must be tight.

Perform FID maintenance if these parts are corroded or oxidized.

T-20 Torx screws (3)

Ignitor

Knurled nut

Agilent 7890 Series Troubleshooting

ALS and Detector Symptoms 2

Corrosion in FID Collector and Ignitor Glow Plug

Agilent 7890 Series Troubleshooting

Agilent recommends inspecting the collector and ignitor glow plug for corrosion while performing maintenance on the FID.

The FID combustion process results in condensation. This condensation, combined with chlorinated solvents or samples, causes corrosion and sensitivity loss.

To avoid corrosion, keep the detector temperature above 300 C.

33

2 ALS and Detector Symptoms

FPD Does Not Ignite

34

Check that the FPD temperature is high enough for ignition (> 150 C).

Check FPD flow rates and that they match the type of filter installed in the FPD. The hydrogen:air ratio greatly impacts ignition. Nonoptimal flow settings can prevent flame ignition.

Measure the actual detector flows. (See To Measure a Detector Flow.)

The column may be installed too high into the detector.

Check that the FPD ignitor operates. (See To Verify That the FPD Flame Is Lit.)

Table 1 FPD+ recommended flows

Sulfur mode flows, mL/min

Phosphorus mode flows, mL/min

Carrier (hydrogen, helium, nitrogen, argon)

Packed columns 10 to 60 10 to 60

Capillary columns 1 to 5 1 to 5

Detector gases

Hydrogen 60 60

Air 60 60

Carrier + makeup 60 60

Table 2 FPD recommended flows

Sulfur mode flows, mL/min

Phosphorus mode flows, mL/min

Carrier (hydrogen, helium, nitrogen, argon)

Packed columns 10 to 60 10 to 60

Capillary columns 1 to 5 1 to 5

Detector gases

Hydrogen 50 75

Air 60 100

Carrier + makeup 60 60

Agilent 7890 Series Troubleshooting

ALS and Detector Symptoms 2

Agilent 7890 Series Troubleshooting

During the ignition sequence, display the air flow rate. The air flow rate should go to 200 mL/min (7890A) or 400 mL/min (7890B) while trying to ignite to flame. If not, there is insufficient air supply pressure.

Check the column and makeup flow rates.

Ensure that condensation in the vent tube is not dripping back into the detector. The flexible plastic vent tube must run from the detector into a container, without sagging, in order to properly drain water condensate. Keep the open tube end out of the water in the container.

Check the Lit offset value. The typical Lit offset value is 2.0. If it is zero, autoignition is turned off. If it is too large, the software will not recognize that the flame is lit and will shut the detector down.

If the flame still will not light, there could be a large leak in the system. This results in measured flow rates being different from actual flow rates, causing non-ideal ignition conditions. Thoroughly leak check the whole system. (See Checking for Leaks.)

Try increasing the supply pressures to the FPD flow module. This makes the flame easier to light without changing the setpoints.

Under some operating conditions, the flame will light more easily with the vent tube removed. After lighting the flame, reinstall the vent tube.

The sulfur mode can be particularly hard to light (FPD only, not FPD+). Try changing to the phosphorus mode flows, lighting the flame, and gradually alter the flows to the sulfur values.

Check cable connections to coupling, coupling connection to glow plug, tight glow plug.

35

2 ALS and Detector Symptoms

NPD Adjust Offset Process Fails

36

Inspect the jet to see if it is clogged. (See To Check for a Plugged NPD Jet.)

Measure the actual detector flows. (See To Measure a Detector Flow.) If the hydrogen or makeup flows are zero or much lower than the displayed flow, suspect a plugged jet.

Check the condition of the bead. Replace if necessary.

Verify that the flow settings are correct. See Flows, temperatures, and bead information.

If the process still fails, there could be a large leak in the system. This causes measured flow rates to be different from actual flow rates. Thoroughly leak check the whole system, especially the detector column fitting. (See Checking for Leaks.)

Set the equilibration time to 0.0.

Agilent 7890 Series Troubleshooting

ALS and Detector Symptoms 2

NPD Bead Will Not Ignite

Agilent 7890 Series Troubleshooting

Set the equilibration time to 0.0.

Verify that the flow settings are correct and appropriate. See Flows, temperatures, and bead information.

If the process still fails, there could be a large leak in the system. This causes measured flow rates to be different from actual flow rates. Thoroughly leak check the whole system, especially the detector column/adapter fitting. (See Checking for Leaks.)

Check for fault messages. Press [Service Mode], then go to Diagnostics > Front detector or Back detector > Detector signal. You can also read the bead voltage.

Check the condition of the bead. Replace if necessary.

Inspect the jet to see if it is clogged. (See To Check for a Plugged NPD Jet.)

Measure the actual detector flows. (See To Measure a Detector Flow.) If the hydrogen or makeup flows are zero or much lower than the displayed flow, suspect a plugged jet.

37

2 ALS and Detector Symptoms

FPD+ Temperature Will Not Become Ready

38

If the FPD+ emission block temperature will not become ready:

Check the oven temperature. If the oven temperature is high (over 325 C) for a long time, set the emission block temperature to its highest value (165 C).

Check the transfer line temperature. If the transfer line is set to a very high temperature (near 400 C), set the emission block temperature to at least 150 C.

Agilent 7890 Series Troubleshooting

ALS and Detector Symptoms 2

Blinking Not Ready Light: Detector Hardware Fault/TCD Filament Voltage

Agilent 7890 Series Troubleshooting

If the TCD filament is open, the Not Ready LED blinks and the GC will not become Ready.

1 Press [Status]. If the display reads Front detector hardware fault or (Back or Aux detector hardware fault), the problem may be the TCD filament.

2 Press [Front Det] (or [Back Det] or [MS/Aux Det]). 3 For GCs with firmware B.02.02 or higher, the display will

read either TCD Open Filament for an open filament, or TCD Bridge Voltage for a shorted filament.

For GCs with earlier firmware: If the display reads Fault: TCD Filament Voltage, scroll to the Filament setpoint. If the setpoint is flashing Off, the problem is an open TCD filament.

4 Power cycle the GC.

5 Press [Front Det] (or [Back Det] or [MS/Aux Det]). 6 Scroll to the Filament and press [Off/No] to disable the TCD

filament. Contact Agilent for service.

To continue to use the GC without the TCD:

1 Turn off all TCD parameters. Save the method.

2 Reconfigure the GC to use another detector. Move the column and set other parameters as needed.

39

2 ALS and Detector Symptoms

Shutdown (Defective) Device

40

By default, the GC monitors the status of all configured devices (inlets, detectors, valve box heaters, valves, oven heater, EPC modules, and so forth) and becomes ready when all of them reach setpoint. If the GC senses a problem in one of these devices, the GC will either never become ready, or may go into a shutdown state to protect itself or prevent a safety hazard. However, there may be a time when you do not wish to have the readiness state of a device prevent a run from starting. An important example is when an inlet or detector heater is defective. Normally, this fault prevents the GC from becoming ready and starting a run. However, you can set the GC to ignore this problem so that you can use the other inlet or detector until the device is repaired.

Not all devices can be ignored. You can ignore the readiness state of inlets, detectors, the oven, or an EPC module. The readiness state of other devices and components can never be ignored, for example, injection devices such as a switching valve or automatic liquid sampler.

To ignore the status of a device:

1 Turn off the devices heater and gas flows as applicable. (Make sure that it cannot create a safety hazard.)

2 Press [Config], then select the element.

3 Scroll to Ignore Ready and press [On/Yes] to set it to True.

You can now use the GC until the device is repaired.

CAUTION Do not ignore the readiness state of a device that is being used unless you do not care if it reaches setpoint. Be sure to return a broken device to Ignore Ready = False after it is repaired. Otherwise, its state (temperature, flow, pressure, and so forth) will continue to be ignored, even if using this device in the analysis.

To consider a devices readiness, set Ignore Ready to False.

Agilent 7890 Series Troubleshooting

Agilent 7890 Series Gas Chromatograph Troubleshooting

3 Chromatographic Symptoms Retention Times Not Repeatable 42 Peak Areas Not Repeatable 43 Contamination or Carryover 44 Larger Peaks Than Expected 47 Peaks Not Displayed/No Peaks 48 Baseline Rise During Oven Temperature Program 50 Poor Peak Resolution 51 Peak Tailing 52 Peak Boiling Point or Molecular Weight Discrimination Poor 54 Sample Decomposition in Inlet/Missing Peaks 55 Peak Fronting 56 Noisy Detector, Including Wander, Drift, and Baseline Spikes 57 Microcell Electron Capture Detector (uECD) Noise and Sensitivity 63 Low Peak Area or Height (Low Sensitivity) 67 FID Flame Goes Out During a Run and Attempts to Reignite 70 FID Baseline Output Above 20 pA 72 FID Baseline Output at Maximum (~8 Million) 73 FPD Flame Goes Out During a Run and Attempts to Reignite 74 FPD Quenching/Repeatability 75 FPD Output Too High or Too Low 76 FPD Low Peak Areas 77 FPD Large Peak Width at Half-Height 78 FPD Baseline Output High, > 20 pA 79 NPD Solvent Quenching 80 NPD Response Low 81 NPD Baseline Output > 8 million 83 NPD Adjust Offset Process Not Functioning Properly 84 NPD Low Selectivity 85 Negative Peaks Seen with TCD 86 TCD Baseline Has Dampened Sinusoidal Noise Trailing Peaks (Ringing Baseline) 87 TCD Peaks Have Negative Dip on Tail 88

41Agilent Technologies

3 Chromatographic Symptoms

Retention Times Not Repeatable

42

Replace the septum.

Check for leaks in the inlet, liner (as applicable), and column connection. (See Checking for Leaks.)

To Perform an Inlet Leak Check

To Check for Leaks in a Split/Splitless Inlet

To Perform a PP Pressure Decay Leak Test

To Check for Leaks in a Multimode Inlet

To Perform a COC Pressure Decay Leak Test

To Perform a PTV Pressure Decay Test

To Perform a VI Pressure Decay Test

Check for sufficient carrier gas supply pressure. The pressure delivered to the GC must be at least 40 kPa (10 psi) greater than the maximum inlet pressure required at final oven temperature.

Run replicates of known standards to verify the problem.

Verify that you are using the correct liner type for the sample being injected. (See Selecting the correct inlet liner.)

Consider if this is the first run. (Has the GC stabilized?)

If using an FID or NPD and retention times increase (drift), check the jet for contamination or replace the jet.

To Replace an FID Jet

To Check for a Plugged FID Jet

To Maintain the NPD Collector, Ceramic Insulators, and Jet

To Check for a Plugged NPD Jet

Agilent 7890 Series Troubleshooting

Chromatographic Symptoms 3

Peak Areas Not Repeatable

Agilent 7890 Series Troubleshooting

Check the ALS syringe operation. (See the Troubleshooting section of the sampler user manual: 7693A, 7650A, 7683B.)

Replace the syringe.

Check for leaks in the inlet, liner (as applicable), and column connection. (See Checking for Leaks.)

Check sample level in vials.

Run replicates of known standards to verify the problem.

Consider if this is the first run. (Has the GC stabilized?)

For a multimode or split/splitless inlet in split mode, also check for:

An abnormal split vent restriction. See:

To Run the Inlet Trap Check

To Perform a SS Split Vent Restriction Test.

To troubleshoot small leaks in a multimode or split/splitless inlet, see To Check for Leaks in a Split/Splitless Inlet or To Check for Leaks in a Multimode Inlet.

43

3 Chromatographic Symptoms

Contamination or Carryover

44

If your output has contamination or unexpected peaks, do the following:

Isolate the source

1 Perform a solvent blank run using a new, pure source of

solvent. If the contamination disappears, the problem may be either in the sample or solvent-related.

2 Perform a blank run (remove the syringe from the injector and start a run). If the contamination disappears, the problem is in the syringe.

3 Remove the column from the detector and cap the detector fitting. Perform another blank run. If the contamination disappears, the problem is in the inlet or column. If the contamination remains, the problem is in the detector.

Check possible causesall inlet and detector combinations

Inlet, sampler, sample, gas supply Check the septum type and installation. The vial septum may

be dissolving in the sample. Be sure the vial septum is resistant enough to the solvent you are using. Also ensure the vial septum is flat. If the vial septum is not flat, the needle tends to core the septum and drop pieces into the sample, causing contamination and ghost peaks.

Perform complete inlet maintenance: Replace all consumable parts and bake out the inlet.

Check for sample carryover from previous runs. Make several no-injection blank runs and see if the ghost peaks go away or get smaller.

Check the septum purge flow. If it is too low, the septum may have collected contamination or condensate may be clogged in the purge line. For SS, MMI, PTV, and PP inlets: Set the purge flow to at least 3 mL/min to keep the septum clean. For COC inlets, set the septum purge flow to at least 15 mL/min. Measure the flow. See To Measure a Column Flow.

Check all gas trap indicators and dates.

Agilent 7890 Series Troubleshooting

Chromatographic Symptoms 3

Agilent 7890 Series Troubleshooting

Verify the gas purity. Perform replicate runs, several with a short interval between them, then several with a large interval. If the contamination peaks are larger for the runs made with the longer interval, suspect contaminated gas: the contamination has more time to deposit onto the column and liner.

Check for supply tubing and fitting contamination.

If you suspect that there is contamination in the inlet, perform the bakeout procedure (SS, MMI, PP, COC, PTV, VI).

Verify the operation of the inlets. Clean the inlet and replace the contaminated inlet parts.

To Clean the Split/Splitless Inlet

To Clean the Purged Packed Inlet

To Clean the Cool On-Column Inlet

To Clean the Septumless Head on the PTV Inlet

To Clean the Multimode Inlet

To Clean the Septum Seat in the Septum Head Assembly of the PTV Inlet

To Clean the VI

Check the solvent level in the ALS wash bottles.

Replace the ALS syringe if necessary (7693A, 7683).

Check the sample injection volume. Verify that the ALS is injecting enough sample into the inlet. Use the Solvent Vapor Volume Calculator to determine how much of the sample should be injected.

Ghost peaks are sometimes caused by contaminated sample vials. Try new or clean vials to see if ghost peaks disappear.

Some samples change with heat or ultraviolet light. Check the sample stability.

Column, method Perform column maintenance: Bake out contaminants,

remove the contaminated length of column near the inlet, and reverse and bake out the column as needed.

If you suspect that there is contamination in the column, perform the bakeout procedure.

Verify that the oven program temperature and time are sufficient for the samples being injected. Ghost peaks that are broader than adjacent sample peaks could be from a previous run.

45

46

3 Chromatographic Symptoms

Inspect the column for contamination. High molecular weight samples that contain residues may cause the syringe, the inlet liner, or the first few inches of column to become contaminated.

Install an Agilent column backflush system.

Detector, detector gas supply Check all gas trap indicators and dates.

Verify the gas purity. Perform replicate runs, several with a short interval between them, then several with a large interval. If the contamination peaks are larger for the runs made with the longer interval, suspect contaminated gas: the contamination has more time to deposit onto the column and liner.

Check for supply tubing and fitting contamination.

If you suspect that there is contamination in the detector, perform the bakeout procedure (FID, TCD, uECD).

Verify the operation of the detectors. Replace the contaminated detector parts.

To Maintain the NPD Collector, Ceramic Insulators, and Jet

Maintaining the FID

Agilent 7890 Series Troubleshooting

Chromatographic Symptoms 3

Larger Peaks Than Expected

Agilent 7890 Series Troubleshooting

Check each configured columns dimensions against the actual column dimensions. (See Configurable Items to Always Keep Current.) Refer to To configure a single column or To configure multiple columns in the Advanced User Guide for procedures on configuring columns.

Check the autosampler injection volume. In the normal injection mode, the sampler uses fast injection to deliver a representative amount of the sample. Fast injection minimizes needle fractionation. Chromatograms from manual injection or slower auto injection devices show higher levels of low molecular weight materials versus higher molecular weight materials because the volatiles boil out of the needle faster than the higher weight materials.

Check the vial caps. Loose vial caps can cause selective loss of lighter materials from a sample. The cap should not rotate easily if installed properly.

Check configured syringe size. Some syringe sizes are specified at half-capacity. If the maximum syringe volume is marked at half-height on the barrel, not at the top of the barrel, enter twice the labeled volume when configuring the syringe size.

47

3 Chromatographic Symptoms

Peaks Not Displayed/No Peaks

48

If using an autosampler:

Ensure that there is sample in the vial.

Verify that the ALS plunger carriage is secured to the syringe plunger.

Check that the syringe is installed correctly and draws sample.

Verify that the turret/tray is loaded correctly and injections are not from out-of-sequence vials.

Watch to see that the sample is pulled into the syringe.

Verify the detector in use is assigned to a signal.

Check the column for proper installation.

Ensure that the column is not plugged. (See To Measure a Column Flow.) Perform column maintenance.

Check for leaks. (See Checking for Leaks.)

Check the flow settings, then measure the actual detector flows. (See To Measure a Detector Flow.)

Some samples change with heat or ultraviolet light. Check sample stability.

Check the sample level in the vial.

If the sample is viscous, try the following:

Increase the viscosity delay time.

Dilute the sample in an appropriate low-viscosity solvent.

Turn the tower fan off.

For 7683B ALS, use the tray quadrants to warm the sample. For 7693A ALS, use the vial heater (accessory G4514A Bar Code Reader/Mixer/Heater) to warm the sample vial.

If the problem is with the detector, see Table 3.

Agilent 7890 Series Troubleshooting

Chromatographic Symptoms 3

Agilent 7890 Series Troubleshooting

Table 3 Detector troubleshooting

Detector Solution

FID, FPD Verify that the electrometer is turned on. Verify that the flame is still lit.

TCD Verify that the filament is turned on. Ensure that the reference gas is not set to zero. (The

filament will not turn on with zero reference gas flow.)

49

3 Chromatographic Symptoms

Baseline Rise During Oven Temperature Program

50

Inspect the column for bleed.

Check for leaks/oxygen in carrier gas supply. Oxygen can damage bonded phase capillary columns.

Check gas supply oxygen trap indicator or date.

Make solvent blank runs to evaluate baseline without sample.

Make no injection blank runs (remove the syringe from the injector and start a run) to evaluate baseline without solvent.

Check for contamination. (See Contamination or Carryover.)

Consider the effect of column film thickness on bleed. Try using a column with a thinner film.

Check for leaks at the column fittings. (See Checking for Leaks.)

Prepare and use a column compensation profile.

Agilent 7890 Series Troubleshooting

Chromatographic Symptoms 3

Poor Peak Resolution

Agilent 7890 Series Troubleshooting

Set column flow to optimum linear velocity.

Install and use deactivated consumable parts in the inlet (for example, a liner).

Perform column maintenance: Bake out contaminants, remove the contaminated length of column near the inlet, and reverse and bake out the column as needed.

Check column installation at both ends.

Select a higher resolution column.

51

3 Chromatographic Symptoms

Peak Tailing

52

The figure below shows an example of tailing peaks. When troubleshooting tailing peaks, consider:

Which peaks are tailing?

Are the tailing peaks active compounds, all compounds, or are there trends (such as early eluters or late eluters)?

Check the column for severe contamination.

If using a capillary column, remove 1/ 2 to 1 meter from the front of the column.

For bonded and cross-linked phases, solvent rinse the column.

Check for inlet contamination. Tailing will sometimes increase with compound retention. Clean the inlet and replace contaminated inlet parts. (See the 7890 Series Maintenance manual.)

Consider the column stationary phase (active column). This only affects active compounds. An active column usually produces tailing that increases with retention time.

Cut off 1 meter from the front of the column.

Replace the column.

Verify that the column was cut and installed properly.

Re-cut and reinstall the column into the inlet and replace the ferrules. Make a clean, square cut using a reliable tool.

Confirm the installation is leak free. If there is a leak at the column fitting, you will see more tailing for early eluting peaks. (See Checking for Leaks.)

Consider the type of adapter, liner, and inlet seal being used. One or all of these may be contaminated or active.

Use a new, deactivated liner. This only affects active compounds.

Agilent 7890 Series Troubleshooting

Chromatographic Symptoms 3

Agilent 7890 Series Troubleshooting

Clean or replace the inlet seal.

Check adapters (if installed) and liner for solid particles. If solid particles are visible, clean or replace.

For capillary splitless injection, consider compatibility between the solvent and column.

Use a different solvent. This will help in instances where there is more tailing for the early eluting peaks or those closest to the solvent front.

Use a 3 to 5 meter retention gap.

Verify that the injection technique is adequate. This is usually related to erratic plunger depression or having sample in the syringe needle.

Verify the inlet temperature.

If the temperature is too high, tailing is generally worse for early eluters. Decrease inlet temperature by 50 C.

If the temperature is too low, tailing usually increases with retention. Increase inlet temperature by 50 C.

Check for dead volume in the system. Check for correct column installation at both ends.

If peak tailing decreases with retention time, reduce dead volume in transfer line connections, fused silica unions, and so forth.

A column installed too high into a detector or inlet can create dead volume areas.

Inspect any transfer lines for cold spots. Cold spots cause tailing that usually increases with retention time.

NPD Peak Tailing

For NPD, do the following:

Verify that you are using the correct bead for the sample being run. If you are analyzing phosphorus, install a black bead. White beads can cause peak tailing when phosphorus is being analyzed.

Verify that the correct jet is installed. Use an extended jet.

Replace the ceramic insulators.

53

3 Chromatographic Symptoms

Peak Boiling Point or Molecular Weight Discrimination Poor

54

If you have trouble with peak boiling point or molecular weight discrimination (inlet discrimination), do the following:

Check the inlet for contamination. Clean and change the liner if necessary. Replace all inlet consumable parts. See the Maintenance manual.

Adjust the inlet temperature.

Run standards against a known method to determine expected performance.

For any inlet operating in split mode with any detector

Check liner type. Use a liner optimized for split analysisone

that contains glass wool or other surface area packing to allow complete sample vaporization.

Increase the inlet temperature and verify that the insulation cup is installed and contains insulation.

Check column cut and installation into the inlet. See the topic for the SS, MMI, PTV, and VI.

For any inlet operating in splitless mode with any detector

Check the inlet for leaks. (See Checking for Leaks.)

Check liner type. Use a liner optimized for splitless analysis (deactivated, large volume).

Verify that the oven starting temperature is less than the solvent boiling point.

Check column cut and installation into the inlet. See the topic for the SS, MMI, PTV, and VI.

Check that the solvent vapor volume does not exceed the liner capacity.

Check for appropriate purge delay time. (Liner volume/column flow)

Agilent 7890 Series Troubleshooting

Chromatographic Symptoms 3

Sample Decomposition in Inlet/Missing Peaks

Agilent 7890 Series Troubleshooting

Lower the inlet temperature.

Check for air or water in the carrier gas; verify gas purity and functionality of traps.

Verify that the liner is appropriate for the sample being run.

Perform complete inlet maintenance: Replace all consumable parts and bake out the inlet.

Install a deactivated liner (if liner is used).

Check for leaks at the septum, liner, and column fittings. (See Checking for Leaks.)

Install an Agilent Direct Connect liner.

Use a pulsed pressure method for quicker sample transfer to column.

Bake out the inlet. See the following:

To Bakeout Contaminants from the Split/Splitless Inlet

To Bakeout Contaminants from the Multimode Inlet

To Bakeout Contaminants from the Purged Packed Inlet

To Bakeout Contaminants from the COC Inlet

To Bakeout Contaminants from the PTV Inlet

To Bakeout Contaminants from the VI Inlet

Clean the inlet. See the following:

To Clean the Split/Splitless Inlet

To Clean the Multimode Inlet

To Clean the Purged Packed Inlet

To Clean the COC Inlet

To Clean the Septumless Head on the PTV Inlet

To Clean the Septum Seat in the Septum Head Assembly of the PTV Inlet

To Clean the VI

55

3 Chromatographic Symptoms

Peak Fronting

56

The figure below shows examples of the three types of peaks: symmetric, fronting, and overloaded.

If peak fronting or overloading occurs, try the following:

Verify that the injection volume is appropriate. Column overload is the most common cause for fronting peaks.

Decrease injection volume, dilute the sample, and/or increase the split ratio.

Change the column type or film thickness.

Ensure that the column is installed properly. If not, reinstall the column in the inlet.

Verify that the appropriate injection technique is being used. This is usually related to erratic plunger depression or having sample in the syringe needle.

If using capillary splitless injection, consider the compound solubility in the injection solvent.

Change the solvent.

Use a retention gap.

Check purity of sample solvent. For solvents with large differences in polarity or boiling points, a mixed sample solvent can cause peak fronting. Change the sample solvent.

Symmetrical Fronting Overloaded

Agilent 7890 Series Troubleshooting

Chromatographic Symptoms 3

Noisy Detector, Including Wander, Drift, and Baseline Spikes

Agilent 7890 Series Troubleshooting

Noise should be measured under normal operating conditions, with a column connected and carrier gas on. FID electrometer noise or drift (flame off), for instance, will not provide much indication of how the detector will perform in practice because major sources of noise are not included in this measurement. Noise typically has a high frequency component (electronic in origin) and lower frequency components that are referred to as wander and drift.

Wander is random in direction but at a lower frequency than the short-term electronic noise. Long-term noise (drift) is a monotonic change in signal over a period that is long compared to the wander and electronic noise (see below). Terms like short and long are relative to the width of the chromatographic peaks. In general, one should measure noise over a period of time that is about 10 times the peak width at half height (or 10 times the area/height ratio for a Gaussian peak). Measuring for longer times can over-estimate noise; shorter times may underestimate noise.

Noisy baseline

Total noise

Long-term noise (drift)

Wander

Short-term noise

A noisy baseline or high detector output can indicate leaks, contamination, or electrical problems. Some noise is inevitable with any detector, although high attenuations can mask it. Since noise limits useful detector sensitivity, it should be minimized.

For all detectors, check for leaks at the column fittings. (See Checking for Leaks.)

For the FID, see To Isolate the Cause of FID Noise.

For the TCD, verify data collection at 5 Hz.

57

58

3 Chromatographic Symptoms

If noise appears suddenly on a previously clean baseline, do the following:

Consider recent changes made to the system.

Bakeout the inlet. See the following:

To Bakeout Contaminants from the Split/Splitless Inlet

To Bakeout Contaminants from the MMI Inlet

To Bakeout Contaminants from the Purged Packed Inlet

To Bakeout Contaminants from the COC Inlet

To Bakeout Contaminants from the PTV Inlet

To Bakeout Contaminants from the VI Inlet

Bakeout can reduce septum bleed and other contaminants. New septa may contribute noise from bleed of low molecular weight material. If noise decreases when inlet temperature is lowered, this is a likely cause. Use only high quality septa and store them where they cannot become contaminated.

Verify the purity of carrier and detector gases. If a tank was replaced recently and the old one is still available and still has some gas in it, try the older tank to see if noise decreases.

If the new gas is so badly contaminated that it saturates traps, changing to the old one may show little improvement until the traps are replaced or regenerated. This problem is most common with nitrogen carrier gas. Deal with a reliable gas supplier.

For the TCD, check for ambient air pressure fluctuations at the GC. Air currents from a fan or air conditioner blowing across the GC may interfere with gas exiting the detector. This is a possible, though not very likely cause of noise since detectors are well protected. Switching off the air current source or shielding the detector exit identifies this problem. Install the TCD outlet restrictor (G1532-60070).

Loose connections in the detector or its signal path generate noise.

Verify proper reassembly after recent maintenance.

Inspect the detector for contamination.

If noise increases gradually to an unacceptable level, check the following possible causes:

Bakeout the detector (FID, TCD, uECD).

Inspect the detector for contamination. Replace parts as needed. (See the 7890 Series Maintenance manual.)

Agilent 7890 Series Troubleshooting

Chromatographic Symptoms 3

Agilent 7890 Series Troubleshooting

Inspect the column and inlet for contamination.

Inspect the FID or NPD jet for contamination.

To Check for a Plugged FID Jet

To Replace an FID Jet

To Check for a Plugged NPD Jet

To Maintain the NPD Collector, Ceramic Insulators, and Jet

Verify that the FPD photomultiplier tube (PMT) is properly installed. If it is not, light leaks and ultimately noise will result.

FIDs are susceptible to gradual buildup of deposits in the detector. In extreme cases, spiking occurs along with increased noise level.

Carbon (black) deposits may form from solvents that burn poorly (primarily chlorinated materials and aromatics). Avoid such solvents if possible. If you must use them, be prepared to clean the detector regularly.

Silicon dioxide (white) is formed when bleed from a silicone column is burned in the flame. To minimize this, use low column loadings, select phases with high temperature limits, condition columns thoroughly before use, and use the lowest possible oven temperature for the analysis.

To remove either type of deposit, disassemble the detector and scrub with a small brush. A solvent (almost anything will do) helps flush away the particles. Agilent recommends replacing dirty collector and insulator parts.

Other factors that can contribute to noise:

Column installed too high into detector.

Oven temperature exceeds column maximum recommended temperatures.

Baseline wander and drift

Baseline wander or drift can occur when a flow or temperature setting is changed. If the system has not stabilized at the new conditions before it starts a run, some baseline changes are to be expected. The following cases assume that sufficient stabilization time has elapsed since the last change in operating conditions.

59

60

3 Chromatographic Symptoms

If experiencing baseline wander, check for leaks, especially at the septum and at the column. (See Checking for Leaks.) If the leak is at the detector end of the column, retention times are stable from run to run but sensitivity is reduced. If it is at the inlet end, sensitivity is reduced and retention times are increased.

Also consider whether the oven temperature program is sufficient.

Baseline drift is most often seen during temperature programming. To correct baseline drift, do the following:

Verify that column compensation is used and the profile is current. (To compensate for bleed.)

Verify that the column is conditioned.

Check column bleed while at operating temperature.

Check the signal mode assigned to the column in the data system.

Check the column compensation profile. It may be too little (upscale drift) or too much (downscale drift).

This cause of drift is minimized by thorough column conditioning. Operating at a lower temperature reduces the drift but prolongs the analysis. Use of a chromatographically equivalent column with a higher temperature limit is also possible.

Baseline spiking

There are two types of spiking on the baseline output: cyclic and random. Spiking will not normally be noticed on the display; it will be noticed only on a plot or online trace.

Figure 1 Cyclic spiking

Cyclic spiking can be caused by the following:

An electric motor

Building heating/cooling system

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Chromatographic Symptoms 3

Agilent 7890 Series Troubleshooting

Other electronic interferences in the lab

Figure 2 Random spiking

Spikes are isolated baseline disturbances, usually appearing as sudden (and large) upscale movements. If accompanied by noise, resolve the noise problem first since spiking may disappear at the same time.

Check for a contaminated detector. In an extremely dirty FID, particles of carbon or silicon dioxide may break away and fall into the detection zone.

For a packed column, check that the packed column exit is properly sealed with glass wool. This will cause packing particles to be blown into the detector. A defective or missing glass wool plug at the exit of a packed column will do this. This may happen with any detector but the flame detector is particularly susceptible because of the narrow bore of the jet.

Check packed column installation. The bottom of the jet or the end of a transfer tube extends into the end of the column. If it touches a glass wool plug, spikes are produced.

Check for the correct jet. See the following:

Selecting an FID jet

To replace an FID jet

Selecting an NPD jet

To Maintain the NPD Collector, Ceramic Insulators, and Jet

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Check that the detector temperature is not too low. See the following:

Recommended starting conditions for new FID methods

Selecting reference and makeup flows for the TCD

Recommended starting conditions for new uECD methods

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Microcell Electron Capture Detector (uECD) Noise and Sensitivity

Agilent 7890 Series Troubleshooting

CAUTION Detector disassembly and/or cleaning procedures other than thermal should be performed only by personnel trained and licensed appropriately to handle radioactive materials. Trace amounts of radioactive 63 Ni may be removed during these other procedures, causing possible hazardous exposure to radiation.

WARNING To prevent possible hazardous contamination of the area with radioactive material, the detector exhaust vent must always be connected to a fume hood, or otherwise vented in compliance with local regulations.

Performance problems associated with the ECD include (but are not limited to) loss of sensitivity (real, or perceived), high signal background, noisy baseline, and chromatographic peaks or humps that are not characteristic of the samples being injected.

If the problems are not accompanied by an increase in the signal output, as read from the front keypad of the GC, then suspect the detector only after the other parts of the chromatographic system have been checked.

Before starting extensive troubleshooting, consider first the nature of the problem:

1 If recent changes were made in the system, such as changing carrier or detector gases, performing inlet or column maintenance, or changing the column, investigate the possibilities that contamination or leaks were introduced.

2 If the problem has been chronic and is now acute enough to interfere with analysis, suspect contamination, column degradation, or ultimately a bad ECD cell.

See also: Display signal evaluation

Sensitivity

Display signal evaluation

The first consideration is the signal value when the GC is in the idle state. The idle signal level is a function of the type and quality of the carrier and detector gases, as well as the flows

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and application. It may be different for different situations but as a general rule, the following values apply (Table 4). Figure 3 shows typical uECD life cycle stages.

Table 4 uECD signal evaluation

ECD signal Comments

<200 uECD is healthy.

200 to 400 Slightly elevated, no cause for concern at this point. Signal still in good range.

400 to 1000 System showing signs of contamination from gases, column, or samples. If the signal increases in response to increased oven temperature, suspect the column.

1000 to 2000 Suspect more severe contamination, follow the troubleshooting guidelines.

>2000 If the following procedures do not work, suspect the uECD cell.

NOTE It may take 24 hours for the uECD baseline to completely stabilize, especially if you are starting with a cold system and want to assure high-sensitivity operation. For the most accurate results, run the detector at normal operating conditions for as long as possible (at least 2 hours and up to 24 hours) before running the frequency test. If you will be injecting into an unused inlet, you must use low-bleed septa. Make sure to condition new septa before use in an inlet for several hours with 1 to 5 mL/min carrier flow.

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Agilent 7890 Series Troubleshooting

Typical ECD Life Cycle Stages:

Stage 1: New cell Background = 100 Hz. Cell meets Agilent signal-to-noise (S/N) standard. Stage 2: 6 months 1 year Background = 180 Hz. Increased response. Stage 3: 12 years Background = 350 Hz. More response, increasing noise, lower S/N. Stage 4: 24 years Background > 500 Hz. Noisy baseline, negative peaks. Thermal cleaning required. Stage 5: 410 years Background > 1000 Hz. Huge response. Very noisy, cell contaminated. Requires cell exchange.

Figure 3 Typical ECD life cycle

1 2 3 4 5

Sensitivity

If the ECD is in the good signal range and sensitivity is the issue, the problems quite likely may be in the inlet or column. Consider the following issues:

1 If using an inlet with split and splitless modes, verify that the mode has not changed and that the split valve is functioning. This can be done by verifying that there is a corresponding change in the response by making split and then splitless injection, all other method parameters remaining the same. If using split mode, verify the split flow using a flow meter.

2 Check all flow rates. See Measuring FID, TCD, uECD, and FPD flows.

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3 Confirm that complete inlet maintenance has been performed. This includes trimming and re-installing the column.

4 Verify that the injecting device is working properly. If the method uses a sampling valve, make a direct syringe injection of concentration similar to that introduced by the valve. Rule out a problem with the valve.

5 Inspect the mixing liner in the makeup gas adapter. A small piece of graphite or sample contamination will reduce sensitivity. See To Replace the uECD Fused Silica Indented Mixing Liner and Install the Makeup Gas Adapter.

Contamination (high baseline)

If the ECD has a baseline higher than expected for its age, check the following:

Rule out all other possible causes. See Sensitivity above. Also check carrier and detector gas supplies, supply gas traps, and the column.

Inspect the mixing liner in the makeup gas adapter. A small piece of graphite can contaminate results. See To Replace the uECD Fused Silica Indented Mixing Liner and Install the Makeup Gas Adapter.

If the detector baseline is > 500 Hz, regardless of detector age, bakeout the detector. Let it run for 12 days.

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Chromatographic Symptoms 3

Low Peak Area or Height (Low Sensitivity)

Agilent 7890 Series Troubleshooting

If using an inlet in split mode, check the split ratio.

Check for leaks. (See Checking for Leaks.) To troubleshoot small leaks in a multimode or split/splitless inlet, see To Check for Leaks in a Split/Splitless Inlet or To Check for Leaks in a Multimode Inlet.

Check the inlet for contamination. (See Contamination or Carryover.)

Check each column and verify that it was cut and installed properly at each end.

Verify that the column type is correct.

Perform column maintenance: Bake out contaminants, remove the contaminated length of column near the inlet, and reverse and bake out the column as needed.

Verify that the liner type is appropriate for the sample.

Verify that the detector flow settings are correct.

Measure the actual detector flows. If an actual flow does not match the GC display, check for contamination and restrictions, for example a plugged jet. See the following:

To Measure a Detector Flow

To Check for a Plugged FID Jet

To Check for a Plugged NPD Jet

Check the supply gas purity.

Check all trap indicators and dates.

Verify that the method parameters are correct.

Some samples change with heat or ultraviolet light. Check sample stability.

Check configured syringe size. Some syringe sizes are specified at half-capacity. If the maximum syringe volume is marked at half-height on the barrel, not at the top of the barrel, enter twice the labeled volume when configuring the syringe size.

If the drop in peak area or height happened gradually due to baseline rise, rather than a sudden change, check for detector contamination. Bakeout the detector (FID, TCD, uECD).

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If using an FID:

Verify that the correct jet is installed.

Check for a dirty jet.

Check for contaminated detector parts.

To Perform Maintenance on the FID Collector Assembly

To Check for a Plugged FID Jet

If using a uECD:

Replace the fused silica indented mixing liner.

Replace and reinstall column.

Clean the makeup gas adapter.

If using an NPD:

Check the detector for contamination.

Replace ceramic insulators.

Replace the bead.

If using an FPD:

Verify correct column installation.

Check that the correct filter is installed and is clean.

Check the flow rates.

Check the makeup gas type.

To Resolve Low Sensitivity with an FID

In normal use, the FID can develop deposits on the collector, insulators, jet, and so forth. To reduce contamination buildup, Agilent recommends using the detector at 300 C or higher. However, even with normal use deposits develop in the jet (usually white silica from column bleed or black, carbonaceous soot). These deposits reduce sensitivity and cause chromatographic noise and spikes. Jets require periodic cleaning or replacement. The following procedure checks for causes of low sensitivity by frequency of occurrence.

For sensitivity loss associated with noise, wander, or drift, also see Noisy Detector, Including Wander, Drift, and Baseline Spikes.

1 Check detector flow settings. See Recommended starting conditions for new FID methods.

The general rule is 1:1 flow ratio of hydrogen to (column + makeup gas).

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Chromatographic Symptoms 3

Agilent 7890 Series Troubleshooting

2 Measure the actual detector flow rates. See To Measure a Detector Flow. If the actual hydrogen, makeup, and capillary column flows are lower than the display, the jet is becoming plugged. See To Check for a Plugged FID Jet. Replace the jet.

3 Check that column is properly installed. Reinstall it. See To Install a Capillary Column in the FID. Make sure the column is installed all the way to the tip and withdrawn 12 mm (column id > 100 m).

4 Check inlet parameters that control venting, such as split ratio and splitless purge delay time. Make sure the sample is not being inadvertently vented.

5 Perform inlet maintenance (replace all consumable parts) and pressure test the inlet when completed. See the maintenance manual and Checking for Leaks.

6 Perform complete FID maintenance. Disassemble the FID and clean or replace all parts. Refer to the following:

To Perform Maintenance on the FID Collector Assembly

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3 Chromatographic Symptoms

FID Flame Goes Out During a Run and Attempts to Reignite

70

The following is an example chromatogram showing a flameout from a large solvent peak.

After a flameout, the GC will try to ignite the flame three times. The GC tries to reignite whenever the detector output falls below the Lit offset setpoint, regardless of whether or not the flame was extinguished. (In a very clean system, the baseline output may be less than 2 pA.)

If the FID flame goes out during a run, do the following:

See if an aromatic solvent peak or water extinguished the flame.

Check for a plugged jet.

Verify that the gas flow settings are correct. Verify that Lit offset is set appropriately.

If the FID flame attempts to reignite but is already lit, do the following:

Verify that the FID Lit offset setting is appropriate for the run (typically 2.0 pA).

Check to see if an aromatic peak or water extinguished the flame.

Check for a partially plugged jet. Measure actual hydrogen, air, and makeup flows at the detector. (See To Measure a Detector Flow.) Replace the jet as needed.

9

8

7

6

5

4

3

2

1 2 3 4 5min

pA

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Check that column is properly installed. Reinstall it. See To Install a Capillary Column in the FID. Make sure the column is installed all the way to the tip and withdrawn 12 mm (column id > 100 m).

Check for leaks at the detector column fitting. (See Checking for Leaks.)

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3 Chromatographic Symptoms

FID Baseline Output Above 20 pA

72

Verify the purity of the carrier and detector gas supply. See the Agilent GC, GC/MS, and ALS Site Preparation Guide.

Inspect the column for column bleed. Lower the oven temperature to ambient. If the detector output drops significantly, suspect a contaminated or bleeding column or contaminated carrier gas. Confirm column bleed by turning off column flow (with oven cool) and checking the detector output.

Check the gas supply trap indicators/dates and ensure that the traps are not expended.

Verify that the detector was reassembled properly after recent maintenance.

Inspect the detector for contamination. Bake out the detector.

Check that the FID leakage current is < 2.0 pA. (See To Measure FID Leakage Current.)

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Chromatographic Symptoms 3

FID Baseline Output at Maximum (~8 Million)

Agilent 7890 Series Troubleshooting

If the FID output seems to be stuck at a very high value (up to 8 million counts), check for a shorted collector.

1 Check if the interconnect spring has been bent. Remove the collector assembly and visually inspect the spring.

2 Disassemble the collector assembly and visually check for rust buildup on any parts. Replace parts as needed. To avoid this problem, operate the detector at >300 C.

3 Check for carbonization in the detector due to injection or aromatic or chlorinated solvents. To avoid this problem, operate the detector at >300 C. Reassemble and install the collector and operate the detector using higher air and hydrogen flows (air must be 450 mL/min, hydrogen at 35 mL/min).

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3 Chromatographic Symptoms

FPD Flame Goes Out During a Run and Attempts to Reignite

74

If the flame goes out during a run, do the following:

Check the GC system for leaks, especially at the detector column fitting. (See Checking for Leaks.)

FPD+: Verify the transfer line temperature is set 200 C.

FPD: Verify the detector temperature is set 200 C.

Ensure that condensation in the vent tube is not dripping back into the detector. The flexible plastic vent tube must run from the detector into a container, without sagging, in order to properly drain water condensate. Keep the open tube end out of the water in the container.

If the FPD flame goes out and then reignites, do the following:

Verify that the Lit offset setting is lower than the normal baseline.

Check for leaks. (See Checking for Leaks.)

Check the flow settings, then measure the actual detector flows. (See To Measure a Detector Flow.)

Certain environmental conditions, such as:

Strong electromagnetic fields

Large ambient temperature swings

Large atmospheric pressure swings

can cause an artificially low signal in the GC, incorrectly indicating that the flame has gone out. As a result, the run aborts and the GC tries to relight an already-lit flame.

You can verify that the flame is lit by holding a cold, shiny surface (such as a mirror or a wrench) over the exit tube. Condensation on the surface indicates that the flame is lit.

Reset the Lit offset to 2.0.

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Chromatographic Symptoms 3

FPD Quenching/Repeatability

Agilent 7890 Series Troubleshooting

Hydrocarbon quenching occurs when a high concentration of carbon dioxide from a hydrocarbon peak is in the flame at the same time as the sulfur species. Part of the light emitted by the sulfur species is absorbed by some CO2 species.

Self-quenching occurs at high concentrations of the heteroatom species. Some other ground state (inactivated) species reabsorbs the emitted photon, preventing it from reaching the PMT.

To resolve hydrocarbon quenching:

The column should provide good separation of the compounds, those that contain sulfur or phosphorus as well as those that do not but may absorb light.

Optimize the chromatographic separation such that hydrocarbon peaks are resolved from sulfur or phosphorus peaks.

1 Run the analysis first on a FID in order to see all the peaks (the FPD ignores hydrocarbons).

2 Run the analysis on the FPD.

3 Modify the method so that the peak of interest is separate from the rest of the peaks.

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3 Chromatographic Symptoms

FPD Output Too High or Too Low

76

Verify that the correct filter is being used. Do not use a phosphorus filter with sulfur-optimized flows or a sulfur filter with phosphorus-optimized flows.

Check the position of the column as installed in the detector.

Check the gas purity.

Verify that the flows are optimized for the filter being used. Monitor the FPD output. The table below provides examples of detector output when the filter installed in the detector and the gas flows in use do not match.

Besides having a mismatch between the filter installed and a particular set of gas flows, check the FPD signal output with the flame lit:

If the output is 0.5 to 3.0, check that the flame is ON.

If the output is 0, check if the electrometer is turned OFF or the signal cable is disconnected.

If the output < 30, the flame may be in the wrong position. Check detector flows, column flow, and column position. See the following:

To Measure a Column Flow

To Measure a Detector Flow

Outputs

Gas flows optimized for

With sulfur filter With phosphorus filter

Sulfur 30 to 50 10 to 12 (low)

Phosphorus 240 to 250 (high) 30 to 50

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Chromatographic Symptoms 3

FPD Low Peak Areas

Agilent 7890 Series Troubleshooting

Check the flow settings, then measure the actual detector flows. (See To Measure a Detector Flow.)

Perform complete inlet maintenance: Replace all consumable parts and bake out the inlet.

Perform column maintenance: Bake out contaminants, remove the contaminated length of column near the inlet, and reverse and bake out the column as needed.

Verify that the column is installed properly.

Consider the filter type (sulfur or phosphorus).

Check the system for leaks. (See Checking for Leaks.)

Verify that the method settings are appropriate.

Check the flow rates.

Check the makeup gas type.

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FPD Large Peak Width at Half-Height

78

If the FPD produces peaks that are abnormally wide at half the peak height, do the following:

Check the actual injection volume; reduce if necessary.

Verify that the liner is not reacting with the sample.

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Chromatographic Symptoms 3

FPD Baseline Output High, > 20 pA

Agilent 7890 Series Troubleshooting

Check the supply gas purity.

Check all trap indicators and dates.

Check the detector for contamination.

Check for light leaks at the photomultiplier tube (PMT); tighten the PMT if it is loose.

Perform complete inlet maintenance: Replace all consumable parts and bake out the inlet.

Perform column maintenance: Bake out contaminants as needed.

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3 Chromatographic Symptoms

NPD Solvent Quenching

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If the baseline does not recover after a solvent peak, try the following:

Turn hydrogen off/on around the solvent peak.

Use nitrogen as the makeup gas.

Set the total column flow and makeup gas to less than 10 mL/min.

Increase the air flow by 10 mL/min.

Increase the detector temperature to 325 C.

Implement an Agilent Deans switch solvent vent solution.

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Chromatographic Symptoms 3

NPD Response Low

Agilent 7890 Series Troubleshooting

Perform complete inlet maintenance: Replace all consumable parts and bake out the inlet.

Perform column maintenance: Bake out contaminants as needed. Verify correct column installation.

A large concentration of solvent has extinguished the hydrogen/air plasma. Increase the bead voltage. Run the makeup gas at a flow rate of 5 mL/min.

Verify that there is hydrogen coming from the external supply. Check that flow and pressure are turned on at the keyboard. The hydrogen flow rate should be between 1.0 and 5.5 mL/min. Measure the actual gas flow at the detector. (See To Measure a Detector Flow.)

Check for a partially plugged jet. See To Check for a Plugged FID Jet.

If the upper ceramic insulator is contaminated, a high offset (2 to 15 pA or more) will occur when the bead is off. This directly affects sensitivity. Replace the ceramic insulator.

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Verify that the bead is activated. Look through the vent hole on the detector lid to see if the bead is glowing orange. If the bead is not glowing, check the detector background signal. Reduce the bead voltage to zero to establish a reference level, and then look for a sudden sharp increase in output as the bead voltage increases, which indicates that ignition occurred. If 4 V are being supplied to the bead but it is not igniting, the bead is probably burned out. Replace the bead.

Replace the insulators/collector.

Check for liquid phase contamination (polar phases).

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Chromatographic Symptoms 3

NPD Baseline Output > 8 million

Agilent 7890 Series Troubleshooting

The collector is shorted to the detector housing. Disassemble the collector and insulators and reinstall.

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3 Chromatographic Symptoms

NPD Adjust Offset Process Not Functioning Properly

84

Inspect the jet to see if it is clogged. (See To Check for a Plugged NPD Jet.)

Measure the actual detector flows. (See To Measure a Detector Flow.) If the hydrogen or makeup flows are zero or much lower than the displayed flow, suspect a plugged jet.

Check the condition of the bead. Replace if necessary.

Verify that the flow settings are correct. See Flows, temperatures, and bead information.

If the process still fails, there could be a large leak in the system. This causes measured flow rates to be different from actual flow rates. Thoroughly leak check the whole system, especially the detector column fitting. (See Checking for Leaks.)

Set the equilibration time to 0.0.

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Chromatographic Symptoms 3

NPD Low Selectivity

Agilent 7890 Series Troubleshooting

(High hydrocarbon response relative to nitrogen or phosphorus.)

Verify that the hydrogen flow is correct (< 3 mL/min).

Inspect the bead; it may be defective or expended.

Verify correct bead voltage.

Replace the collector and insulators.

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Negative Peaks Seen with TCD

86

Verify that the correct gas type is being used.

Check for a leak in the system, especially at the detector column fitting. (See Checking for Leaks.)

Consider thermal conductivity of analytes relative to carrier.

Check the flow settings, then measure the actual detector flows. (See To Measure a Detector Flow.)

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Chromatographic Symptoms 3

TCD Baseline Has Dampened Sinusoidal Noise Trailing Peaks (Ringing Baseline)

Agilent 7890 Series Troubleshooting

Wrong data rate is selected in the data system. For TCD, the data rate should be 5 Hz.

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3 Chromatographic Symptoms

TCD Peaks Have Negative Dip on Tail

88

Check for leaks at the detector column adapter fitting. (See Checking for Leaks.)

Upgrade the detector to a passivated filament.

Agilent 7890 Series Troubleshooting

Agilent 7890 Series Gas Chromatograph Troubleshooting

4 GC Not Ready Symptoms GC Never Becomes Ready 90 Flow Never Becomes Ready 91 Oven Temperature Never Cools Down/Cools Very Slowly 92 Oven Never Heats Up 93 Temperature Never Becomes Ready 94 Cannot Set a Flow or Pressure 95 A Gas Does Not Reach Setpoint Pressure or Flow 96 A Gas Exceeds Pressure Setpoint or Flow 97 The Inlet Pressure or Flow Fluctuates 98 Cannot Maintain a Pressure as Low as the Setpoint on a Split Inlet 99 The Measured Column Flow Does Not Equal the Displayed Flow 100 FID Does Not Ignite 101 FID Ignitor Does Not Glow During Injection Sequence 102 FID or NPD Measured Hydrogen and Makeup Gas Flows Much Less Than Setpoint 104 NPD Adjust Offset Process Fails 105 FPD Does Not Ignite 106 Valve Not Ready 108 Blinking Not Ready Light: Detector Hardware Fault/TCD Filament Voltage 109

This section includes faults and symptoms that will occur when the GC is on but cannot perform analyses. This is indicated by a Not Ready warning, by fault messages, or by other symptoms.

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4 GC Not Ready Symptoms

GC Never Becomes Ready

90

Normally the GC becomes ready after flows and temperatures reach setpoint. If the GC does not become ready after a long period of time:

Press [Status] or a component key (for example, [Front inlet]) to see which setpoints or conditions are not ready.

Check for a sampler problem.

Check for a data system problem.

If performing manual injections in splitless or gas-saver mode, you may need to press [Prep Run] to prepare the inlet for the injection. Do this, for example:

To toggle the inlet purge valve before a splitless injection

To prepare for a pulsed injection

To turn off gas saver.

For more information on [Prep Run], see the Agilent 7890 GC Advanced User Guide.

Agilent 7890 Series Troubleshooting

GC Not Ready Symptoms 4

Flow Never Becomes Ready

Agilent 7890 Series Troubleshooting

If the gas flow never becomes ready, check for the following:

Check the supply gas for sufficient delivery pressure.

Check the restrictors installed in the Aux EPC module. See Restrictors in the Advanced User Guide.

Check the configured gas type. The configured gas type must match the actual gas plumbed to the GC.

Check for leaks in the gas delivery plumbing and the GC. (See Checking for Leaks.)

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4 GC Not Ready Symptoms

Oven Temperature Never Cools Down/Cools Very Slowly

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If the oven does not cool down or cools down very slowly:

WARNING The exhaust coming from the back of the GC is very hot. Keep hands and face away from the exhaust vent.

Check oven flapper operation.

1 Decrease oven temperature by at least 20 degrees.

2 Verify that the oven flaps in the back of the GC are open. Listen to verify that the fan is operating. The figure below illustrates the location of the two oven flaps.

If the flaps are not operating smoothly, contact Agilent for service.

If using cryo cooling:

Check for sufficient cryo coolant.

Check if operating limits have been exceeded.

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GC Not Ready Symptoms 4

Oven Never Heats Up

Agilent 7890 Series Troubleshooting

Press [Status] to check for errors to report to Agilent.

WARNING The exhaust coming from the back of the GC is very hot. Keep hands and face away from the exhaust vent.

Power cycle the GC.

Check oven flapper operation.

1 Increase oven temperature by at least 20 degrees.

2 Verify that the oven flaps in the back of the GC are closed. The figure below illustrates the location of the two oven flaps.

If the flap is stuck open or if the flaps are closed and the oven still does not heat, contact Agilent.

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4 GC Not Ready Symptoms

Temperature Never Becomes Ready

94

To be considered ready, a temperature must be at setpoint 1 C for 30 s. If a temperature never becomes ready, do the following:

Check for a missing insulation cup on an inlet or detector.

Check for a very large temperature difference between the oven and inlet or detector.

Check for missing insulation around the inlet or detector.

If using an inlet cryo cooling (COC, PTV, or MMI):

Check cryo coolant level.

Check if operating limits have been exceeded. If, for example, you are operating the GC in a hot room at a high oven temperature and a very low inlet temperature, an inlet may not reach its desired temperature.

Agilent 7890 Series Troubleshooting

GC Not Ready Symptoms 4

Cannot Set a Flow or Pressure

Agilent 7890 Series Troubleshooting

If you cannot set a flow or pressure using the split/splitless, MMI, PTV, VI, or cool on-column inlets, do the following:

Check the column mode.

Check that a capillary column is configured to the correct inlet.

Check the configured column dimensions.

Check that the flow is turned on.

If you cannot set a flow or pressure using the purged packed inlet, do the following:

Check the column mode.

Check that the flow is turned on.

Check the inlet mode. When using inlet flow control, you can set only flow control modes for columns. When using inlet pressure control, you can set the column for both flow and pressure modes.

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4 GC Not Ready Symptoms

A Gas Does Not Reach Setpoint Pressure or Flow

96

If an inlet does not reach its pressure setpoint, it will shut down in an amount of time determined by the type of inlet. Do the following:

Check for sufficient gas supply delivery pressure. The pressure at the supply should be at least 10 psi greater than the desired setpoint.

Check for leaks. (See Checking for Leaks.) A large leak may be present somewhere in the system. Use an electronic leak detector to find leaks, then correct them. Do not forget to check the columna broken column is a very large leak.

To troubleshoot a multimode or split/splitless inlet, see To Check for Leaks in a Multimode Inlet or To Check for Leaks in a Split/Splitless Inlet.

If using gas saver, be sure that the gas saver flow rate is high enough to maintain the highest column-head pressure used during a run.

Check for an incorrectly installed column.

Check for a defective inlet or detector pressure sensor.

If you are using a split/splitless inlet, MMI inlet, PTV inlet, or volatiles interface:

Check the split ratio. Increase the amount of split flow.

Agilent 7890 Series Troubleshooting

GC Not Ready Symptoms 4

A Gas Exceeds Pressure Setpoint or Flow

Agilent 7890 Series Troubleshooting

If a gas exceeds its pressure or flow setpoint, do the following:

If using a split/splitless inlet, MMI inlet, PTV inlet, or volatiles interface:

Decrease the split ratio.

Replace the split vent filter. See the procedure for the SS, MMI, PTV, or VI.

Check the split vent trap line for contamination or an abnormal restriction. Run the split vent restriction test in Agilent Instrument Utilities, if available, or from the GC front panel. See:

To Check or Monitor Split Vent Line Backpressure

To Run the Inlet Trap Check

To Check a Split Vent Line for Contamination

Verify that the correct liner is selected (if liner is used). See Selecting the correct MMI inlet liner or Selecting the correct SS inlet liner.

Verify the method pressure settings for the SS inlet are above the minimum viable settings available on the GC. See Table 4.

Check the gold seal for contamination (for split/splitless inlet). See To Replace the Gold Seal on the Split/Splitless Inlet.

For a split/splitless inlet, if using a liner that causes a restriction, install a high flow gold seal.

If using an FID or NPD:

Check for a plugged jet. See To Check for a Plugged FID Jet or To Check for a Plugged NPD Jet.

Valves:

Check for a misaligned rotor. Align the rotor.

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4 GC Not Ready Symptoms

The Inlet Pressure or Flow Fluctuates

98

A fluctuation in inlet pressure causes variations in the flow rate and retention times during a run. Do the following:

Check if the gas purifier or gas generator is operating at or near capacity.

Check the supply gas for sufficient delivery pressure.

Verify that the supply pressure regulator is functioning properly. Systems with long supply tubing lengths may require a step-down regulator near the GC. Also, use an additional regulator to smooth out fluctuations caused by gas generators.

Check for leaks. (See Checking for Leaks.) A large leak may be present somewhere in the system. Use an electronic leak detector to find leaks, then correct them. Do not forget to check the columna broken column is a very large leak.

Check for large restrictions in the inlet liner or split vent trap.

Verify that the correct liner is installed. Some liners have large pressure drops caused by design or tight packaging.

Check for extreme changes in room temperature during runs. Correct laboratory temperature problem or move the instrument to a more suitable location.

Check for a restriction in headspace, purge and trap, and any other external sampling devices.

Verify Auto Flow Zero feature is On. See AutoFlowZero.

Agilent 7890 Series Troubleshooting

GC Not Ready Symptoms 4

Cannot Maintain a Pressure as Low as the Setpoint on a Split Inlet

Agilent 7890 Series Troubleshooting

If the GC cannot maintain a pressure as low as the setpoint, check for the following:

Consider using a liner designed for split analysis.

Method pressure parameter (or resultant pressure from a flow setting) is too low for the carrier gas type. See Split/Splitless inlet split mode minimum operating pressures or Multimode inlet split mode minimum operating pressures and the table below.

Table 5 Approximate minimum viable inlet pressures for inlet in split mode, in psi (split/splitless, multimode)

Split vent flow (mL/min)

50100 100200 200400 400600

Helium and hydrogen carrier gases

Split liners - 5183-4647, 19251-60540 2.5 3.5 4.5 6.0

Splitless liners - 5062-3587, 5181-8818 4.0 5.5 8.0 11.0

Nitrogen carrier gas

Split liners - 19251-60540, 5183-4647 3.0 4.0

Splitless liners - 5062-3587, 5181-8818 4.0 6.0

Check for a plugged liner.

Check for contamination or restriction in the split vent line. See:

To Perform a SS Split Vent Restriction Test.

To Check or Monitor Split Vent Line Backpressure

To Run the Inlet Trap Check

To Check a Split Vent Line for Contamination

For the split/splitless inlet, replace gold seal..See To Replace the Gold Seal on the Split/Splitless Inlet.

99

4 GC Not Ready Symptoms

The Measured Column Flow Does Not Equal the Displayed Flow

100

If the actual column flow does not match the calculated flow displayed on the GC within 10%, do the following:

Verify that the measured flows are corrected to 25 C and 1 atmosphere.

Verify that the correct column dimensions are configured accurately, including the actual (trimmed) column length.

A short (<15 m) 0.58 to 0.75 mm id WCOT column is being used with a split/splitless capillary inlet. The total flow controller is set for a high flow rate, which creates some pressure in the inlet and causes column flow even with a setpoint pressure of zero. (In these situations, an actual pressure may be shown on the display, even with a zero setpoint.) With short, 530 to 750 mm columns, keep the total flow rate as low as possible (for example, 20 to 30 mL/min). Install a longer column with higher resistance (for example, 15 to 30 m).

The split vent line or trap may be partly plugged, creating an actual inlet pressure higher than the setpoint pressure. Check for a restriction in the split vent line. See To Run the Inlet Trap Check.

If using a Mass Selective Detector, verify the column outlet for the transfer line is set to MSD.

Make sure that the auto flow zero is turned on. As applicable, zero the flow and pressure sensor for the flow module. If this does not solve the problem, replace the flow module.

Agilent 7890 Series Troubleshooting

GC Not Ready Symptoms 4

FID Does Not Ignite

Agilent 7890 Series Troubleshooting

Verify that the Lit Offset is <2.0 pA.

Ensure that the FID temperature is high enough for ignition (>150 C). Agilent recommends >300 C.

Check that the FID ignitor glows during ignition sequence. (See To Verify FID Ignitor Function During Ignition Sequence.)

Check that the air and hydrogen pressures meet Agilents recommendations (hydrogen > 35 psi [210 kPa] and air > 55 psi [380 kPa]). See the Agilent GC, GC/MS, and ALS Site Preparation Guide.

Try increasing the supply pressures to the FID flow module. This makes the flame easier to light without changing the setpoints.

Increase hydrogen and air flow rates until ignition occurs, then reduce them toward the method values. Experiment for the best values.

Check for a plugged or partially plugged jet. (See To Check for a Plugged FID Jet.)

Measure the FID flow rates. Actual flow rates should be within +/-10% of the setpoint. (See FID starting conditions.) The hydrogen:air ratio greatly impacts ignition. Nonoptimal flow settings can prevent flame ignition. (See To Measure a Detector Flow.)

There could be a large leak in the system if the flame still will not light. Large leaks result in measured flow rates being different from actual flow rates, causing nonideal ignition conditions. Thoroughly leak check the whole system, especially the column fitting at the FID. (See Checking for Leaks).

Check the column flow rate. (See To Measure a Column Flow.) Hydrogen flow should be greater than the sum of the column flow and makeup flow.

If the analysis permits, substitute nitrogen for helium as makeup.

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4 GC Not Ready Symptoms

FID Ignitor Does Not Glow During Injection Sequence

102

WARNING Keep body parts at a safe distance from the FID chimney while performing this task. If using hydrogen, the FID flame will not be visible.

1 Remove the detector top cover.

2 Turn the FID flame On. 3 Observe the ignitor plug though the FID chimney. The small

hole should glow during ignition sequence.

If the test fails, check for the following possible causes:

The ignitor may be bad; replace the ignitor. (See To Perform Maintenance on the FID Collector Assembly.)

Detector temperature is set to < 150 C. Agilent recommends operating the FID at > 300 C.

The ignitor is not making a good connection to the ground:

The ignitor must be tightly screwed into the FID castle assembly.

The three T-20 Torx screws that hold the collector assembly in place must be tight.

Agilent 7890 Series Troubleshooting

GC Not Ready Symptoms 4

Agilent 7890 Series Troubleshooting

The brass knurled nut that holds the FID castle assembly in place must be tight.

Perform FID maintenance if these parts are corroded or oxidized.

T-20 Torx screws (3)

Ignitor

Knurled nut

103

4 GC Not Ready Symptoms

FID or NPD Measured Hydrogen and Makeup Gas Flows Much Less Than Setpoint

104

Check for a clogged or partially clogged jet. A clogged jet creates backpressure. Since the flow module uses pressure control, the increased backpressure simulates proper flow. The actual flow rate will drop but the GC remains functional. See:

To Check for a Plugged FID Jet

To Check for a Plugged NPD Jet

Check for a column fitting leak at the detector base.

Replace the FID or NPD jet.

Agilent 7890 Series Troubleshooting

GC Not Ready Symptoms 4

NPD Adjust Offset Process Fails

Agilent 7890 Series Troubleshooting

Inspect the jet to see if it is clogged. (See To Check for a Plugged NPD Jet.)

Measure the actual detector flows. (See To Measure a Detector Flow.) If the hydrogen or makeup flows are zero or much lower than the displayed flow, suspect a plugged jet.

Check the condition of the bead. Replace if necessary.

Verify that the flow settings are correct. See Flows, temperatures, and bead information.

If the process still fails, there could be a large leak in the system. This causes measured flow rates to be different from actual flow rates. Thoroughly leak check the whole system, especially the detector column fitting. (See Checking for Leaks.)

Set the equilibration time to 0.0.

105

4 GC Not Ready Symptoms

FPD Does Not Ignite

106

Check that the FPD temperature is high enough for ignition (> 150 C).

Check FPD flow rates and that they match the type of filter installed in the FPD. The hydrogen:air ratio greatly impacts ignition. Nonoptimal flow settings can prevent flame ignition.

Measure the actual detector flows. (See To Measure a Detector Flow.)

The column may be installed too high into the detector.

Check that the FPD ignitor operates. (See To Verify That the FPD Flame Is Lit.)

Table 6 FPD+ recommended flows

Sulfur mode flows, mL/min

Phosphorus mode flows, mL/min

Carrier (hydrogen, helium, nitrogen, argon)

Packed columns 10 to 60 10 to 60

Capillary columns 1 to 5 1 to 5

Detector gases

Hydrogen 60 60

Air 60 60

Carrier + makeup 60 60

Table 7 FPD recommended flows

Sulfur mode flows, mL/min

Phosphorus mode flows, mL/min

Carrier (hydrogen, helium, nitrogen, argon)

Packed columns 10 to 60 10 to 60

Capillary columns 1 to 5 1 to 5

Detector gases

Hydrogen 50 75

Air 60 100

Carrier + makeup 60 60

Agilent 7890 Series Troubleshooting

GC Not Ready Symptoms 4

Agilent 7890 Series Troubleshooting

During the ignition sequence, display the air flow rate. The air flow rate should go to 200 mL/min (7890A) or 400 mL/min (7890B) while trying to ignite to flame. If not, there is insufficient air supply pressure.

Check the column and makeup flow rates.

Ensure that condensation in the vent tube is not dripping back into the detector. The flexible plastic vent tube must run from the detector into a container, without sagging, in order to properly drain water condensate. Keep the open tube end out of the water in the container.

Check the Lit offset value. The typical Lit offset value is 2.0. If it is zero, autoignition is turned off. If it is too large, the software will not recognize that the flame is lit and will shut the detector down.

If the flame still will not light, there could be a large leak in the system. This results in measured flow rates being different from actual flow rates, causing non-ideal ignition conditions. Thoroughly leak check the whole system. (See Checking for Leaks.)

Try increasing the supply pressures to the FPD flow module. This makes the flame easier to light without changing the setpoints.

Under some operating conditions, the flame will light more easily with the vent tube removed. After lighting the flame, reinstall the vent tube.

The sulfur mode can be particularly hard to light (FPD only, not FPD+). Try changing to the phosphorus mode flows, lighting the flame, and gradually alter the flows to the sulfur values.

Check cable connections to coupling, coupling connection to glow plug, tight glow plug.

107

4 GC Not Ready Symptoms

Valve Not Ready

108

Troubleshooting depends on the type of valve.

External valves

External valves are valves connected to the GC through the external events or BCD connectors on the back panel

This Not Ready state means that the +24 V supply to the pneumatics valves is actually less than +16.5 V. All valves are disabled to prevent improper operation.

When full voltage is restored, the GC becomes ready.

This Not Ready state could indicate a hardware problem in the external valve or in the GC analog and power board.

Gas sampling valves

The GC is normally not ready whenever the inject time or load time has not elapsed. It becomes ready when the specified load or inject time has passed.

Multiposition valve

A multiposition valve can cause the GC to be in a not ready state for one of the following reasons:

The multiposition valve is not at the setpoint position. The GC remains not ready until the valve reaches the setpoint.

The BCD cable is missing or not plugged into the receptacle. If the cable is missing, the valve will never become ready.

The BCD setpoint is incorrect for the valve BCD output polarity. The valve will most likely shutdown with Illegal Position or Not Switching shutdown errors.

If the valve is plugged or the sample is viscous, the switching time may be too short for the valve to switch. Increase the switching time.

Agilent 7890 Series Troubleshooting

GC Not Ready Symptoms 4

Blinking Not Ready Light: Detector Hardware Fault/TCD Filament Voltage

Agilent 7890 Series Troubleshooting

If the TCD filament is open, the Not Ready LED blinks and the GC will not become Ready.

1 Press [Status]. If the display reads Front detector hardware fault or (Back or Aux detector hardware fault), the problem may be the TCD filament.

2 Press [Front Det] (or [Back Det] or [MS/Aux Det]). 3 For GCs with firmware B.02.02 or higher, the display will

read either TCD Open Filament for an open filament, or TCD Bridge Voltage for a shorted filament.

For GCs with earlier firmware: If the display reads Fault: TCD Filament Voltage, scroll to the Filament setpoint. If the setpoint is flashing Off, the problem is an open TCD filament.

4 Power cycle the GC.

5 Press [Front Det] (or [Back Det] or [MS/Aux Det]). 6 Scroll to the Filament and press [Off/No] to disable the TCD

filament. Contact Agilent for service.

To continue to use the GC without the TCD:

1 Turn off all TCD parameters. Save the method.

2 Reconfigure the GC to use another detector. Move the column and set other parameters as needed.

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110

4 GC Not Ready Symptoms

Agilent 7890 Series Troubleshooting

Agilent 7890 Series Gas Chromatograph Troubleshooting

5 Shutdown Symptoms Column Shutdowns 112 Hydrogen Shutdowns 114 Detector Air Shutdowns 116 7890B MS Shutdown 117 Thermal Shutdowns 119

111Agilent Technologies

5 Shutdown Symptoms

Column Shutdowns

112

The GC monitors inlet and auxiliary gas streams. If a carrier gas (which can include an auxiliary flow module or pneumatics control module) is unable to reach its flow or pressure setpoint, the GC assumes that a leak exists. It will warn you with a beep after 25 seconds, and it will continue to beep in intervals. After about 5 minutes, the GC will shut down components to create a safe state. The GC:

Displays Front inlet pressure shutdown.

Turns off to avoid column damage.

Opens oven flaps in the back of the oven halfway.

Flashes oven temperature setpoint Off. Turns off all flows for the column. When viewed, their

parameters flash Off. For example, the septum purge and column flows for a split/splitless inlet would turn off.

Turns off all other heaters. When viewed, their temperature parameters flash Off.

Attempts to turn on a shut-down zone fail with an error message.

Turns off the TCD filament.

Turns off the FID or FPD ignitor, and the air and fuel gas flows.

Turns off the NPD bead, and air and fuel gas flows.

7890B: Communicates with the configured MS, if present, so the MS can react to the shutdown event.

To recover from this state.

1 Fix the cause of the shutdown. Verify the carrier gas supply. The GC requires a delivered gas pressure of 70 kPa (10 psi) higher than the highest pressure used in the run. See the Agilent GC, GC/MS, and ALS Site Preparation Guide.

Check for a broken column near the inlet.

Check for leaks.

Replace the inlet septum.

Replace the inlet O-ring.

Check the supply pressure.

2 Press the key for the device that initiated the shutdown. Scroll to the pneumatic parameter that is flashing Off, then press [On] or [Off].

Agilent 7890 Series Troubleshooting

Shutdown Symptoms 5

Agilent 7890 Series Troubleshooting

For example, if the front inlet ran out of carrier gas, press [Front Inlet], scroll to the pressure or flow parameter, then press [On].

After a column shutdown, you can turn on a detector gas flow even if the keyboard is locked by a data system.

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5 Shutdown Symptoms

Hydrogen Shutdowns

114

Hydrogen gas may be used as a carrier or as fuel for some detectors. When mixed with air, hydrogen can form explosive mixtures.

Hydrogen used in inlets and auxiliary gas streams

The GC monitors inlet and auxiliary gas streams. If a stream is unable to reach its flow or pressure setpoint and if that stream is configured to use hydrogen, the GC assumes that a leak exists. It will warn you with a beep after 25 seconds, and it will continue to beep in intervals. After about 5 minutes, the GC will shut down components to create a safe state. The GC:

Displays Hydrogen Safety Shutdown.

Closes the carrier supply valve to the inlet and closes and turns off both pressure and flow controls. When viewed, these parameters will flash Off.

Opens the split vent valves in the split/splitless and PTV inlets.

Turns off the oven heater and fan and opens the oven flaps.

Turns off all heaters (including any devices connected to the auxiliary heater controls, such as valve box heaters and transfer line heaters). When viewed, these parameters will flash Off.

Turns off the TCD filament.

Turns off the FID or FPD ignitor, and the air and fuel gas flows.

Turns off the NPD bead, and air and fuel gas flows.

Sounds an alarm.

7890B: Communicates with a configured MS, if present, so the MS can react to the shutdown event.

WARNING The GC cannot detect leaks in the detector gas streams. For this reason, it is vital that the column fittings of the FID, NPD, and any other detectors that use hydrogen always be connected to a column or have a cap or plug installed and that hydrogen streams be configured so that the GC is aware of them.

Agilent 7890 Series Troubleshooting

Shutdown Symptoms 5

Agilent 7890 Series Troubleshooting

To recover from a hydrogen shutdown state:

1 Fix the cause of the shutdown:

Replace the inlet septum. See the Maintenance manual.

Replace the inlet O-ring. See the Maintenance manual.

Check for broken column.

Check the supply pressure. Make sure the gas supply meets the pressure recommendations listed in the Agilent GC, GC/MS, and ALS Site Preparation Guide.

Check the system for leaks. See Leak Check Tips.

2 Power cycle the GC.

3 After the GC powers back on, press the key for the device that initiated the shutdown. Scroll to the pneumatic parameter that is flashing Off, then press [On] or [Off]. For example, if the front inlet ran out of carrier gas, press [Front Inlet], scroll to the pressure or flow parameter, then press [On].

After a column shutdown, you can turn on a detector gas flow even if the keyboard is locked by a data system.

Hydrogen sensor

If equipped with the optional hydrogen sensor, the GC will perform a hydrogen safety shutdown if the sensor measures an uncombusted hydrogen concentration of about 1 % in the oven (about 25 % of the lower explosive limit for hydrogen).

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5 Shutdown Symptoms

Detector Air Shutdowns

116

When air is used to combust a fuel gas (hydrogen) in a detector, an insufficient air supply will cause a shutdown for the air channel. In addition, the Air and Hydrogen flows for the associated detector will be turned Off.

To recover from this state.

1 Fix the cause of the shutdown. Verify the air supply. The FID and NPD require a delivered gas pressure of 380690 kPa (55100 psi). The FPD and FPD+ require a delivered gas pressure of 690827 kPa (100120 psi). See the Agilent GC, GC/MS, and ALS Site Preparation Guide.

2 Press the key for the detector that initiated the shutdown. Scroll to each pneumatic parameter that is flashing Off, then press [On] or [Off].

Agilent 7890 Series Troubleshooting

Shutdown Symptoms 5

7890B MS Shutdown

Agilent 7890 Series Troubleshooting

If the 7890B receives a shutdown event from, or loses communications with, a configured MS, the GC reacts with changes such as:

Turning off the column oven.

Setting low pressures/flows for the MS flow path.

Turning off hydrogen carrier gas flow, if used.

Aborting a current run.

Turning off the MS transfer line heater.

Blocking all setpoint changes.

The exact changes depend on the event that triggered the shutdown. For example, the GC may react differently to a communications loss than to a failure in the MS high vacuum pump.

When troubleshooting an MSD Shutdown:

1 Check all GC, MS and data system events and logs. The GC will enter MS Shutdown if:

The GC cannot maintain carrier flow into the MS.

The MS reports a shutdown or fault.

The GC and MS lose communications with each other.

2 Check the current communications status.

5977A, 7000C, 7010:

a Press [MS/Aux Det]. b The MS Communication setting should read Connected. If

not, check the entered GC and MS IP addresses in the GC, the MS, and the PC. All GC and MS IP addresses must match in all three places.

c Check the GC and MS LAN connections. Is the LAN switch or hub operating?

5977B:

a Press [Config][MS/Aux Det]. b The Lvds communication setting should read On.

c Check the GC and MS LAN connections. Is the LAN switch or hub operating?

117

5 Shutdown Symptoms

Clearing an MS Shutdown

118

Unlike other shutdowns, you cannot clear this state by turning off a setpoint (because setpoint changes are blocked). Instead, clear this state by disabling GC to MS communications.

5977A, 7000C, 7010:

1 Press [MS/Aux Det]. 2 Scroll to MS Communication.

3 Press Off/No.

5977B:

1 Press [Config][MS/Aux Det]. 2 Scroll to Lvds communication.

3 Press Off/No.

If the GC started the shutdown, you can now troubleshoot the problem and resolve the GC fault.

After resolving an MS Shutdown

After resolving the GC or MS problem, always restore GC to MS communications.

5977A, 7000C, 7010:

1 Press [MS/Aux Det]. 2 Scroll to MS Communication.

3 Press On/Yes.

5977B:

1 Press [Config][MS/Aux Det]. 2 Scroll to Lvds communication.

3 Press On/Yes.

Agilent 7890 Series Troubleshooting

Shutdown Symptoms 5

Thermal Shutdowns

Agilent 7890 Series Troubleshooting

A thermal fault means that the oven or another heated zone is not within its allowable temperature range (lower than minimum temperature or higher than maximum temperature). Several things could cause this error:

A problem with the electrical supply to the instrument.

A malfunction of the zone control electronics.

A shorted temperature sensor.

A shorted heater.

To recover from this state:

1 Fix the cause of the shutdown:

Check for missing insulation.

2 Most thermal shutdowns can be cleared by shutting off the thermal zone.

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5 Shutdown Symptoms

Agilent 7890 Series Troubleshooting

Agilent 7890 Series Gas Chromatograph Troubleshooting

6 GC Power On and Communication Symptoms GC Does Not Turn On 122 PC Cannot Communicate with GC 123 GC Cannot Communicate with a Configured MS or HS 124 GC Does Not Recover After Firmware Update 125 GC Turns On, Then Stops During Startup (During Self-Test) 126

121Agilent Technologies

6 GC Power On and Communication Symptoms

GC Does Not Turn On

122

If the GC does not turn on:

Check the power cord.

Check the buildings power.

If the problem is at the GC, turn off the GC power. Wait 30 seconds, then turn the on the GC power.

Agilent 7890 Series Troubleshooting

GC Power On and Communication Symptoms 6

PC Cannot Communicate with GC

Agilent 7890 Series Troubleshooting

Run a ping test

The MS-DOS ping command verifies communications across a TCP/IP connection. To use it, open the command prompt window. Type ping followed by an IP address. For example, if the IP address is 10.1.1.101, enter ping 10.1.1.101. If LAN communications are working properly, you will see a successful reply. For example:

If the ping test is successful, check the software configuration.

If the problem is that a data system cannot connect to the GC, check if another PC is controlling the GC. At the GC keypad, press [Options], scroll to and select Communication, then scroll the display down. If a computer is connected to the GC, its network name will appear below the Enable DHCP line.

If the ping test is unsuccessful, do the following:

Check the LAN cabling.

Verify the IP address, subnet mask, and gateway addresses.

Make sure all network devices (hubs, switches, and so forth) are turned on, properly connected, and working.

Check for a defective LAN card in the PC.

If using a direct PC to GC setup, make sure you are using a crossover cable. If using a setup with a hub or switch (that is, connecting to a building or site LAN), make sure you are NOT using a crossover cable.

123

6 GC Power On and Communication Symptoms

GC Cannot Communicate with a Configured MS or HS

124

1 First, check that GC to MS (or GC to HS) communications are enabled.

For an MS (5977A, 7000C, 7010):

a Press [MS/Aux Det]. b Scroll to MS Communication.

For an MS (5977B):

a Press [Config][MS/Aux Det]. b Scroll to Lvds communication.

For a HS:

a Press [Front Injector] or [Back Injector] as appropriate.

b Scroll to HS Communication.

If the MS Communication/HS Communication/Lvds communication entry reads Off, press [On/Yes].

If the entry reads Connecting but does not connect, continue troubleshooting.

2 Check that the GC IP address is correctly entered and correct as needed. Go to Options > Communications.

3 5977A, 7000C, 7010: Check that the MS or HS IP address is correctly entered into the GC. Under Options > Communications, scroll to Mass Spec., Fr. Headspace, or Bk. Headspace to see the current IP address. Compare this entry with the IP address shown on the MS or HS display.

4 5977B: Check that the MS IP address is correctly entered and correct as needed. Go to [Config] > [MS/Aux Det].

5 5977A, 7000C, 7010: If using an MS, use the MS keypad to check the MS and GC IP addresses entered into the MS. They must exactly match those entered into the GC.

6 If using a HS, use the HS keypad to check the HS and GC IP addresses entered into the HS. They must exactly match those entered into the GC.

7 If the addresses are correct in both the GC and the MS or HS, ping each instrument from a computer on the same local LAN. (See PC Cannot Communicate with GC for more information about the PC ping command.)

8 If using an Agilent data system, check the GC, HS, and MS IP addresses entered into the data system software. Again, these must exactly match the values entered into each instrument.

Agilent 7890 Series Troubleshooting

GC Power On and Communication Symptoms 6

GC Does Not Recover After Firmware Update

Agilent 7890 Series Troubleshooting

If the GC starts but does not display the Power on successful message, look for any error messages. Record any messages. Then resolve the problem as follows:

1 Try power cycling the GC.

2 If the GC still does not recover, turn off the GC.

3 While pressing the [Stop] and [0] keys, turn on the GC. Continue to hold the keys until the GC reboots. You should see a display similar to the following:

MMON Version X.XX

IP = 10. 1. 1.101

If this display appears, you can now communicate to the GC. Reload the firmware.

4 If the GC does not boot up and show a display similar to the one above, or if the update fails again, contact Agilent for service.

125

6 GC Power On and Communication Symptoms

GC Turns On, Then Stops During Startup (During Self-Test)

126

If the GC turns on but the normal display does not appear:

1 Turn the GC power switch Off. Wait one minute, then turn the GC power On.

2 If the GC does not return to normal, record any messages that appear on the display. Observe the GC back panel, and look for LED indicator lights (green, yellow, or red) above the REMOTE connector and whether they are flashing or constant. (For older GCs, look through the slots in the GC right side panel where shown below.) Contact Agilent for service, and provide the display information to the Agilent support personnel. (See also Information to Obtain Before Calling Agilent for Service.)

Older GC: LEDs visible through side panel.

Agilent 7890 Series Troubleshooting

Agilent 7890 Series Gas Chromatograph Troubleshooting

7 Checking for Leaks Leak Check Tips 128 To Check for External Leaks 129 To Check for GC Leaks 131 Leaks in Capillary Flow Fittings 132 To Perform an Inlet Leak Check 133 To Check for Leaks in a Split/Splitless Inlet 136 To Perform a SS Pressure Decay Leak Test 138 To Correct Leaks in the Split Splitless Inlet 143 To Check for Leaks in a Multimode Inlet 144 To Perform a MMI Pressure Decay Test 146 To Correct Leaks in the Multimode Inlet 150 To Perform a PP Pressure Decay Leak Test 151 To Correct Leaks in the Packed Column Inlet 155 To Perform a COC Pressure Decay Leak Test 156 To Correct Leaks in the Cool On-Column Inlet 160 To Perform a PTV Pressure Decay Test 161 To Correct Leaks in the PTV Inlet 165 To Perform a VI Pressure Decay Test 166 To Prepare the VI for a Closed System Leak Check 170 To Correct Leaks in the Volatiles Interface 171

127Agilent Technologies

7 Checking for Leaks

Leak Check Tips

128

When checking for leaks, consider the system in two parts: external leak points and GC leak points.

External leak points include the gas cylinder (or gas purifier), regulator and its fittings, supply shutoff valves, and connections to the GC supply fittings.

GC leak points include inlets, detectors, column connections, valve connections, and connections between flow modules and inlets/detectors.

WARNING Hydrogen (H2) is flammable and is an explosion hazard when mixed with air in an enclosed space (for example, a flow meter). Purge flowmeters with inert gas as needed. Always measure gases individually. Always turn off detectors to prevent flame/bead autoignition.

WARNING Hazardous sample gases may be present.

1 Gather the following:

Electronic leak detector capable of detecting the gas type

7/16-in, 9/16-in, and 1/4-in wrenches for tightening Swagelok and column fittings

2 Check any potential leak points associated with any maintenance recently performed.

3 Check GC fittings and connections that undergo thermal cycling, since thermal cycling tends to loosen some fitting types. Use the electronic leak detector to determine if a fitting is leaking.

Start by checking any newly made connections first.

Remember to check connections in the gas supply lines after changing traps or supply cylinders.

Agilent 7890 Series Troubleshooting

Checking for Leaks 7

To Check for External Leaks

Agilent 7890 Series Troubleshooting

Check for leaks at these connections:

Gas supply bulkhead fittings

Gas cylinder fitting

Regulator fittings

Traps

Shut-off valves

T-fittings

Perform a pressure drop test.

1 Turn off the GC.

2 Set the regulator pressure to 415 kPa (60 psi).

129

130

7 Checking for Leaks

3 Fully turn the regulator pressure adjustment knob counterclockwise to shut the valve.

4 Wait 10 min. If there is a pressure loss greater than 7 kPa (1 psi), there is a leak in the external connections.

Agilent 7890 Series Troubleshooting

Checking for Leaks 7

To Check for GC Leaks

Agilent 7890 Series Troubleshooting

Check for leaks at these connections:

Inlet septum, septum head, liner, split vent trap, split vent trap line, and purge vent fittings

Column connections to inlets, detectors, valves, splitters, and unions

Fittings from the flow modules to the inlets, detectors, and valves

Column adapters

Agilent capillary flow fittings

First, use the GCs built-in leak test to check for leaks at the inlet column fitting, septum, liner, split vent trap line, and so forth. See To Perform an Inlet Leak Check. Correct any leaks found using this test. If the GC still shows symptoms of a leak, check the other possible leak points.

If using Agilent Instrument Utilities, you can also use it to remotely run an inlet leak check (for selected inlet types).

If the inlet passes the inlet leak check but you still suspect a leak in the inlet, you can use the Instrument Utilities software to perform a pressure decay test for most inlets. (You can also perform a manual pressure decay test on any inlet.) Any inlet that passes the inlet pressure decay test can be considered leak free.

To Perform a SS Pressure Decay Leak Test

To Perform a MMI Pressure Decay Test

To Perform a PP Pressure Decay Leak Test

To Perform a COC Pressure Decay Leak Test

To Perform a PTV Pressure Decay Test

To Perform a VI Pressure Decay Test

Use an electronic leak detector to check column connections and tubing connections. See also:

To Check for Leaks in a Split/Splitless Inlet

To Check for Leaks in a Multimode Inlet

Leaks in Capillary Flow Fittings

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7 Checking for Leaks

Leaks in Capillary Flow Fittings

132

For capillary flow fittings, a leak usually indicates that the fitting has been overtightened. Unless the fitting is obviously loose, do not tighten it further. Instead, remove the connection, trim the column end, and install it again. (See To Attach a Capillary Column Using SilTite Metal Fittings.)

Also inspect the plate and connection for a broken column tip.

Agilent 7890 Series Troubleshooting

Checking for Leaks 7

To Perform an Inlet Leak Check

Agilent 7890 Series Troubleshooting

The GC provides a real-time, built-in leak check for all inlets. This check is most useful for finding inlet leaks during and after inlet maintenance. While not as thorough or sensitive as a complete inlet pressure test, it is normally performed with the column installed and configured, and provides a quick assurance that the inlet is reasonably leak-free. Agilent recommends running the check before and during inlet maintenance, so that as you tighten any fittings you can watch the inlet stop leaking. The test is appropriate for all applications, although some may require more robust leak testing.

The inlet leak check finds leaks at the:

Inlet column fitting

Gold seal (as applicable)

Split vent trap housing (as applicable)

Septum nut and septum (as applicable)

Insert weldment nut/septum head assembly (as applicable)

To run the test:

1 At the GC keypad, press [Service Mode], scroll to Front inlet leak check or Back inlet leak check, then press [Enter].

2 The display will be similar to Figure 4:

Figure 4 Example front inlet leak check display. Example assumes a test has been previously run. (Scroll the display to see all lines.)

FRONT INLET LEAK CHECK TotalFlow 1.74 Col 1.34< Test Inlet (ON to Start) Test pressure 10.0 psi Warning if check flow OFF Fault if check flow OFF Last test results Tue Oct 20 16:07 2009 Test flow OK: 4.8 Reset the test results? (yes)

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7 Checking for Leaks

3 Verify that the Test pressure is acceptable. Typically, the default pressure of 10 psi works well. If desired, enter a different inlet pressure.

For repeatable results, use the same value for the same hardware.

Enter a higher test pressure if using a column that produces high backpressure.

4 Scroll to Test Inlet and press [On/Yes]. 5 After a moment, the test stabilizes.

The TotalFlow reading shows the total flow of carrier gas through the inlet. The Col reading shows the flow through the column.

The approximate leak rate is TotalFlow Col, in mL/min.

Consider the inlet leak free if the Col reading approximately equals the TotalFlow reading.

6 While monitoring the readings, tighten fittings, replace the septum, change the liner O-ring, and so forth as needed. If the repair stops the leak, you will see the Col reading decrease to be approximately equal to the TotalFlow reading.

NOTE If you ran the test on a leak-free inlet before performing maintenance, the leak test result after maintenance should be about the same as it was before maintenance.

7 If the test still fails:

Replace the septum

Reinstall the column into the inlet

Replace the liner and liner O-ring

Open the split vent trap and check the O-ring seating. Replace the split vent trap if needed.

If the test passes, but you still suspect an inlet leak, perform a pressure decay leak test. See:

To Perform a SS Pressure Decay Leak Test

To Perform a MMI Pressure Decay Test

To Perform a PP Pressure Decay Leak Test

To Perform a PTV Pressure Decay Test

To Perform a VI Pressure Decay Test

Agilent 7890 Series Troubleshooting

Checking for Leaks 7

To set warning limits for a leak check

Agilent 7890 Series Troubleshooting

The GC provides two alerts related to the inlet leak check:

Warning if pressure check: If the measured pressure exceeds the limit, turn on the Service Due indicator.

Fault if pressure check: If the measured pressure exceeds the limit, make the GC Not Ready.

You can determine reasonable inlet leak check results, then set the GC to either go Not Ready or set the Service Due indicator if the leak check fails. To set one or both limits:

1 When the inlet is considered leak-free, run the inlet leak check. (Assume the inlet is leak-free if the TotalFlow and Col readings are very close and you are satisfied with the GCs chromatographic results.)

2 Note the TotalFlow result.

3 Scroll to Warning if pressure check or Fault if pressure check.

4 Enter a limit using the keypad, then press [Enter]. Select a flow rate that is higher than the acceptable

TotalFlow reading. Ideally, enter a value that corresponds to known chromatographic problems.

The warning and fault limits can be different, for example, a warning at a lower limit, and a fault at a higher one.

5 If desired, repeat for Fault if pressure check.

6 The test is now set up.

7 Periodically rerun the test. When the test fails, fix any leaks.

To clear a Not Ready condition or to turn off the Service Due indicator:

1 Press [Service Mode], scroll to Front inlet leak check or Back inlet leak check, then press [Enter].

2 Scroll to Reset the test results? and press [On/Yes].

To disable a warning limit for the inlet leak check

1 Press [Service Mode], scroll to Front inlet leak check or Back inlet

leak check, then press [Enter]. 2 Scroll to the warning limit, then press [Off/No].

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7 Checking for Leaks

To Check for Leaks in a Split/Splitless Inlet

136

This procedures describes how to check for and fix leaks in the split/splitless inlet. Follow the procedures below based on the inlets symptoms.

Cannot Reach Pressure Setpoint

If the split/splitless EPC inlet does not reach its pressure setpoint, the GC will be Not Ready. Pressing [Status] indicates the front (or back) inlet pressure is not ready. The GC will shut down in approximately 5.5 minutes if the inlet cannot pressurize and control.

If you have recently performed maintenance, first check for leaks on any fittings/parts you handled.

1 Verify sufficient gas supply pressure delivered to the GC (see the GC, GC/MS, and ALS Site Preparation Guide), and verify no leaks in the gas supply (see To Check for External Leaks). The inlet requires 70 kPa (10 psi) above the highest pressure used in the method.

120 psi maximum for 0100 psi inlet

170 psi maximum for 0150 psi inlet

2 Check the total flow setting. Total flow must be high enough to maintain inlet pressure throughout the run. Wide bore columns require higher flow rates. Typically 50 mL/min is sufficient. To increase total flow:

Increase split ratio if in split mode

Increase the purge flow for splitless mode

3 Put your thumb (or a septum) over the split vent exhaust. If the inlet pressure begins to rise to the setpoint, call Agilent for service. If the pressure remains low, continue with the next step.

4 Perform the inlet run leak check. See To Perform an Inlet Leak Check. The total flow provides an indication of the magnitude of the leak. Monitor the total flow while checking/tightening fittings:

Septum nut

Column

Split vent trap/O-rings

Liner/O-rings

Gold seal

Agilent 7890 Series Troubleshooting

Checking for Leaks 7

Agilent 7890 Series Troubleshooting

Split vent line connection to the inlet body

Flow block fittings on the flow manifold

Alternately, use an electronic leak detector to check these fittings/connections.

If these checks do not resolve the problem, contact Agilent for service.

Low Sensitivity or Poor Repeatability

A small leak in the split/splitless EPC inlet can cause low sensitivity or poor repeatability. Check for and isolate a small leak as described below.

If you have recently performed maintenance, first check for leaks on any fittings/parts you handled.

1 Perform the inlet pressure decay test. See To Perform a SS Pressure Decay Leak Test. If the test passes, consider the inlet leak-free and check other possible causes for the low sensitivity or poor repeatability.

2 If the pressure decay test fails, perform the inlet leak check. See To Perform an Inlet Leak Check. Monitor the total flow while checking/tightening fittings:

Septum nut

Column

Split vent trap

Liner/O-ring

Gold seal

Split vent line connection to the inlet body

Flow block fittings on the flow manifold

3 If the inlet (prep run) leak check did not resolve the problem, the leak may be too small to detect using that test. Use an electronic leak detector to check the fittings/connections.

If these checks do not resolve the problem, contact Agilent for service.

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7 Checking for Leaks

To Perform a SS Pressure Decay Leak Test

138

Use the Agilent Instrument Utilities Split/Splitless Inlet Pressure Decay Test to determine if the inlet is leaking. Open the software, select the GC, and run the test for the inlet. See To Perform an Inlet Leak Check and To Perform a SS Split Vent Restriction Test.

If the Instrument Utilities software is not available, see the procedure below.

If the test fails:

See To Check for Leaks in a Split/Splitless Inlet.

Check the plugged column fitting and septum purge cap.

To perform a SS inlet pressure decay test at the GC keyboard

The pressure decay test checks for leaks from the inlet flow module up to the column fitting.

After performing maintenance, first check for leaks in externally accessible areas. See To Check for External Leaks.

If a leak is known to exist, check the externally accessible inlet fittings first, especially any connection that has seen recent maintenance, such as the septum nut, column adapter, column connection, and so forth.

The pressure decay leak test described below requires removing the column and capping the inlet column fitting. This test can/cannot find the following types of leaks:

Agilent 7890 Series Troubleshooting

Checking for Leaks 7

Agilent 7890 Series Troubleshooting

1 Gather the following (see Consumables and parts for the split/splitless inlet):

No-hole ferrule

1/4-inch wrench

Heat-resistant gloves (if the inlet is hot)

Column nut

New septum

O-ring

ECD/TCD Detector plug (part no. 5060-9055)

2 Load the inlet maintenance method and wait for the GC to become ready.

3 Remove the column, if installed.

4 Plug the column fitting with a column nut and a no-hole ferrule.

5 Remove the old septum and replace it with a new one. See To change the septum on the split/splitless inlet.

6 Inspect the O-ring and replace it if it is hard and brittle or cracked. See To change the liner and O-ring on the split/splitless inlet.

7 Set the inlet to Split Mode.

The test can find leaks at the: The test cannot find leaks at the:

septum column fitting

septum nut gas supply bulkhead fittings to the flow module

liner O-ring seal tubing and connections in a transfer line connected to the inlet

gold seal/washer and reducing nut internal leaks in an EPC module (septum purge valve)

inlet body

flow manifold split vent valve

flow manifold septum purge valve

split vent tubing and trap

septum purge tubing

seals within the tubing between the inlet flow module and the inlet body

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7 Checking for Leaks

8 Configure the column as Inlet: Unspecified.

9 Set the inlet temperature to 70 C.

10 Set the Total flow to 60 mL/min.

11 Enter a pressure setpoint of 25 psi (172 kPa). Make sure that the pressure supplied to the GC is at least 10 psi (70 kPa) higher than the inlet pressure.

12 If pressure cannot be achieved, there is either a large leak or the supply pressure is too low.

13 Set the Septum purge flow to 3.0 mL/min.

14 Allow the inlet temperature to stabilize. Temperature changes can invalidate the test.

15 Cap the septum purge fitting with the ECD/TCD detector plug.

Back inlet purge vent

Front inlet purge vent

Back inlet split vent

Front inlet split vent

Agilent 7890 Series Troubleshooting

Checking for Leaks 7

Agilent 7890 Series Troubleshooting

Front purge vent shown plugged

16 From the keypad, press [Service Mode]. Select Diagnostics > Front or Back Inlet > Pneumatics Control > Septum Purge control.

17 Scroll to the Constant duty cycle and enter 50. Wait 10 seconds.

18 Press [Front Inlet] or [Back Inlet]. Scroll to Pressure and press Off/No.

19 Quickly turn off the carrier gas supply at its source, if possible. The goal is to prevent any residual pressure from the supply lines from leaking into the closed system and causing a pressure rise and masking leaks. (Such leaks in through the EPC module typically do not impact runs.) If the setup does not include shutoff valves at the GC, or if changing the source pressure is not practical, skip this step. If there is a relatively large volume in the supply tubing leading up to the GC, consider whether or not there could have been a leak into the system when evaluating the test results.

20 Monitor the pressure for 10 minutes. Use the timer by pressing [Time] and [Enter].

For GCs with no device installed in the carrier flow path:

A pressure drop of less than 0.5 psig (0.05 psi/min or less; 3.4 kPa or 0.34 kPa/min) is acceptable.

If the pressure drops much faster than the acceptable rate, see To Correct Leaks in the Split Splitless Inlet. Retest.

For a GC with a 7697A Headspace Sampler:

A pressure drop of less than 1.7 psig (0.17 psi/min or less; 11.7 kPa or 1.17 kPa/min) is acceptable. If the 7697A passes all its leak tests (restriction, pressure decay, and cross port), and if the GC inlet pressure decay test passes without the 7697A installed, check the 7697A carrier flow path. See the Headspace Sampler documentation.

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For a GC with a G1888 Headspace Sampler:

A pressure drop of less than 2 psig in 5 minutes (0.4 psi/min or less; 13.8 kPa or 2.76 kPa/min) is acceptable when using a 1 cc sample loop.

For all GCs:

Note that liner size impacts pressure drop. An inlet with a smaller volume liner does not tolerate as large a leak rate as an inlet with a larger volume liner.

21 After the inlet passes the test, restore the GC to operating condition.

Restore source pressures.

Remove any caps/plugs.

Reinstall the column.

Restore the correct column configuration.

Load the operating method.

Agilent 7890 Series Troubleshooting

Checking for Leaks 7

To Correct Leaks in the Split Splitless Inlet

Agilent 7890 Series Troubleshooting

If the inlet fails a pressure decay test, check the following:

Check the caps/plugs used in the testmake sure each is correctly installed and tight.

If you performed the leak test after performing maintenance, check for proper installation of the part(s) handled during the maintenance.

Check the tightness of the septum nut.

Check the septum. Replace if old or damaged.

Check the insert assembly installation.

Check the liner and liner O-ring. See To change the liner and O-ring on the split/splitless inlet.

If you changed the gold seal, verify correct installation. See To replace the gold seal on the split/splitless inlet.

Make sure the inlet temperature remained constant during the test.

If these items do not resolve the problem, contact Agilent for service.

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7 Checking for Leaks

To Check for Leaks in a Multimode Inlet

144

This procedures describes how to check for and fix leaks in the Multimode inlet. Follow the procedures below based on the inlets symptoms.

Cannot Reach Pressure Setpoint

If the Multimode EPC inlet does not reach its pressure setpoint, the GC will be Not Ready. Pressing [Status] indicates the front (or back) inlet pressure is not ready. The GC will shut down in approximately 5.5 minutes if the inlet cannot pressurize and control.

If you have recently performed maintenance, first check for leaks on any fittings/parts you handled.

1 Verify sufficient gas supply pressure delivered to the GC (see the GC, GC/MS, and ALS Site Preparation Guide), and verify no leaks in the gas supply (see To Check for External Leaks). The inlet requires 70 kPa (10 psi) above the highest pressure used in the method.

120 psi maximum for 0100 psi inlet

170 psi maximum for 0150 psi inlet

2 Check the total flow setting. Total flow must be high enough to maintain inlet pressure throughout the run. Wide bore columns require higher flow rates. Typically 50 mL/min is sufficient. To increase total flow:

Increase split ratio if in split mode

Increase the purge flow for splitless mode

3 Put your thumb (or a septum) over the split vent exhaust. If the inlet pressure begins to rise to the setpoint, call Agilent for service. If the pressure remains low, continue with the next step.

4 Perform the inlet leak check. See To Perform an Inlet Leak Check. The total flow provides an indication of the magnitude of the leak. Monitor the total flow while checking/tightening fittings:

Septum nut

Column

Split vent trap/O-rings

Liner/O-rings

Split vent line connection to the inlet body

Agilent 7890 Series Troubleshooting

Checking for Leaks 7

Agilent 7890 Series Troubleshooting

Flow block fittings on the flow manifold

Alternately, use an electronic leak detector to check these fittings/connections.

If these checks do not resolve the problem, contact Agilent for service.

Low Sensitivity or Poor Repeatability

A small leak in the Multimode EPC inlet can cause low sensitivity or poor repeatability. Check for and isolate a small leak as described below.

If you have recently performed maintenance, first check for leaks on any fittings/parts you handled.

1 Perform the inlet pressure decay test. If the test passes, consider the inlet leak-free and check other possible causes for the low sensitivity or poor repeatability.

2 If the pressure decay test fails, set the inlet to split mode. Set a column flow of 3 mL/min, a septum purge flow of 3 mL/min, and a purge flow of 50 mL/min. Press [Prep Run]. Monitor the inlet total flow. If the total flow is much greater than 6 mL/min, check/tighten the following fittings:

Septum nut

Column

Split vent trap

Liner/O-ring

Split vent line connection to the inlet body

Flow block fittings on the flow manifold

If the problem continues, the leak may be small.

3 Use an electronic leak detector to check the fittings/connections.

If these checks do not resolve the problem, contact Agilent for service.

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7 Checking for Leaks

To Perform a MMI Pressure Decay Test

146

Use the Agilent Instrument Utilities Multimode Inlet Pressure Decay Test to determine if the inlet is leaking. Open the software, select the GC, and run the test for the inlet.

If the Instrument Utilities software is not available, see the procedure below.

If the test fails:

Check the plugged column fitting and septum purge cap.

Check the septum head. Tighten if needed.

Replace the septum if necessary.

Inspect and re-install the liner if it is leaking.

Tighten the split vent trap if needed, or install a new cartridge and O-rings.

Tighten the split vent line connection to the inlet.

To Perform a Multimode Inlet Pressure Decay Test

The pressure decay test checks for leaks from the inlet flow module up to the column fitting.

After performing maintenance, first check for leaks in externally accessible areas. See To Check for External Leaks.

If a leak is known to exist, check the externally accessible inlet fittings first, especially any connection that has seen recent maintenance, such as the septum nut, column adapter, column connection, and so forth.

The pressure decay leak test described below requires removing the column and capping the inlet column fitting. This test can/cannot find the following types of leaks:

Agilent 7890 Series Troubleshooting

Checking for Leaks 7

Agilent 7890 Series Troubleshooting

1 Gather the following (see Consumables and parts for the Multimode inlet):

No-hole ferrule

1/4-inch wrench

Heat-resistant gloves (if the inlet is hot)

Column nut

New septum

O-ring

ECD/TCD Detector plug (part no. 5060-9055)

2 Load the inlet maintenance method and wait for the GC to become ready.

3 Remove the column, if installed.

4 Plug the column fitting with a column nut and a no-hole ferrule.

5 Remove the old septum and replace it with a new one. See To change the septum on the multimode inlet.

6 Inspect the O-ring and replace it if it is hard and brittle or cracked. See To change the liner and O-ring on the Multimode inlet.

7 Set the inlet to Split Mode.

8 Configure the column as Inlet: Unspecified.

9 Set the inlet temperature to 70 C.

The test can find leaks at the: The test cannot find leaks at the:

septum column fitting

septum nut gas supply bulkhead fittings to the flow module

liner O-ring seal tubing and connections in a transfer line connected to the inlet

inlet body

flow manifold split vent valve

flow manifold septum purge valve

split vent tubing and trap

septum purge tubing

seals within the tubing between the inlet flow module and the inlet body

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7 Checking for Leaks

10 Set the Total flow to 60 mL/min.

11 Enter a pressure setpoint of 25 psi (172 kPa). Make sure that the pressure supplied to the GC is at least 10 psi (70 kPa) higher than the inlet pressure.

12 If pressure cannot be achieved, there is either a large leak or the supply pressure is too low.

13 Set the Septum purge flow to 3.0 mL/min.

14 Allow the inlet temperature to stabilize. Temperature changes can invalidate the test.

15 Cap the septum purge fitting with the ECD/TCD detector plug.

Back inlet purge vent

Front inlet purge vent

Back inlet split vent

Front inlet split vent

Front purge vent shown plugged

Agilent 7890 Series Troubleshooting

Checking for Leaks 7

Agilent 7890 Series Troubleshooting

16 From the keypad, press [Service Mode]. Select Diagnostics > Front or Back Inlet > Pneumatics Control > Septum Purge control.

17 Scroll to the Constant duty cycle and enter 50. Wait 10 seconds.

18 Press [Front or Back Inlet]. Scroll to Pressure and press Off/No.

19 Quickly turn off the carrier gas supply at its source, if possible. The goal is to prevent any residual pressure from the supply lines from leaking into the closed system and causing a pressure rise and masking leaks. (Such leaks in through the EPC module typically do not impact runs.) If the setup does not include shutoff valves at the GC, or if changing the source pressure is not practical, skip this step. If there is a relatively large volume in the supply tubing leading up to the GC, consider whether or not there could have been a leak into the system when evaluating the test results.

20 Monitor the pressure for 10 minutes. Use the timer by pressing [Time] and [Enter].

A pressure drop of less than 0.5 psig (0.05 psi/min or less; 3.4 kPa or 0.34 kPa/min) is acceptable.

If the pressure drops much faster than the acceptable rate, see To Correct Leaks in the Multimode Inlet. Retest.

Note that liner size impacts pressure drop. An inlet with a smaller volume liner does not tolerate as large a leak rate as an inlet with a larger volume liner.

21 After the inlet passes the test, restore the GC to operating condition.

Remove any caps/plugs.

Reinstall the column.

Restore the correct column configuration.

Load the operating method.

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7 Checking for Leaks

To Correct Leaks in the Multimode Inlet

150

If the inlet fails a pressure decay test, check the following:

Check the caps/plugs used in the testmake sure each is correctly installed and tight.

If you performed the leak test after performing maintenance, check for proper installation of the part(s) handled during the maintenance.

Check the tightness of the septum nut. See To change the septum on the Multimode inlet.

Check the septum. Replace if old or damaged.

Check the insert assembly installation.

Check the liner and liner O-ring. See To change the liner and O-ring on the Multimode inlet.

Make sure the inlet temperature remained constant during the test.

If these items do not resolve the problem, contact Agilent for service.

Agilent 7890 Series Troubleshooting

Checking for Leaks 7

To Perform a PP Pressure Decay Leak Test

Agilent 7890 Series Troubleshooting

Use the Agilent Instrument Utilities Purged/Packed Inlet Pressure Decay Test to determine if the inlet is leaking. Open the software, select the GC, and run the test for the inlet.

If the Instrument Utilities software is not available, see the procedure below.

If the test fails:

Tighten the septum nut/Merlin cap.

Replace the septum or Merlin Microseal.

Tighten the top insert weldment. Replace the liner.

Replace the O-ring and tighten the column adapter connection. Re-install if needed.

Check the plugged column fitting and the septum purge cap.

To Perform a PP Inlet Pressure Decay Test

The pressure decay test checks for leaks from the inlet flow module up to the column fitting.

After performing maintenance, first check for leaks in externally accessible areas. See To Check for External Leaks.

If a leak is known to exist, check the externally accessible inlet fittings first, especially any connection that has seen recent maintenance, such as the septum nut, column adapter, column connection, and so forth.

The pressure decay leak test described below requires removing the column and capping the inlet column fitting. This test can/cannot find the following types of leaks:

The test can find leaks at the: The test cannot find leaks at the:

septum column fitting

septum nut gas supply bulkhead fittings to the flow module

glass insert O-ring seal

adapter and ferrule

inlet body

top insert weldment

151

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7 Checking for Leaks

1 Gather the following (see Consumables and parts for the purged packed inlet):

No-hole ferrule

1/4-inch wrench

7/16-inch wrench

Heat-resistant gloves (if the inlet is hot)

9/16-inch wrench

1/8- and 1/4-inch Swagelok caps

ECD/TCD Detector plug (part no. 5060-9055)

2 Load the inlet maintenance method and wait for the GC to become ready.

3 Set the total flow to 40 mL/min and purge the inlet for about 1 minute.

4 Remove the column, if installed.

5 Plug the column fitting.

If the capillary column adapter is installed, use a column nut and a no-hole ferrule

If a 1/8-inch packed column adapter is installed, use a 1/8-inch Swagelok cap (5180-4121).

If a 1/4-inch packed column adapter is installed, use a 1/4-inch Swagelok cap (5180-4120)

6 Remove the old septum and replace it with a new one. See To change the septum on the purged packed inlet.

7 Inspect the O-ring and replace it if it is hard and brittle or cracked. See To change the O-ring on the purged packed inlet.

8 If unsure of the quality of the adapter ferrule, replace it. See To change the glass insert on a PP inlet.

9 Configure, but do not install, a capillary column to put the inlet in pressure control mode.

10 Set the inlet temperature to 100 C.

11 Enter a pressure setpoint of 25 psi (172 kPa). Make sure that the pressure supplied to the GC is at least 10 psi (70 kPa) higher than the inlet pressure.

seals within the tubing between the inlet flow module and the inlet body

The test can find leaks at the: The test cannot find leaks at the:

Agilent 7890 Series Troubleshooting

Checking for Leaks 7

Agilent 7890 Series Troubleshooting

12 If pressure cannot be achieved, there is either a large leak or the supply pressure is too low.

13 Set the Septum purge flow to 3.0 mL/min.

14 Allow the inlet temperature to stabilize. Temperature changes can invalidate the test.

15 Cap the septum purge fitting with the ECD/TCD detector plug.

Back inlet purge vent

Front inlet purge vent

Back inlet split vent

Front inlet split vent

Front purge vent shown plugged

16 From the keypad, press [Service Mode]. Select Diagnostics > Front or Back Inlet > Pneumatics Control > Septum Purge control.

17 Scroll to the Constant duty cycle and enter 50. Wait 10 seconds.

18 Press [Front or Back Inlet]. Scroll to Pressure and press Off/No.

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7 Checking for Leaks

19 Quickly turn off the carrier gas supply at its source, if possible. The goal is to prevent any residual pressure from the supply lines from leaking into the closed system and causing a pressure rise and masking leaks. (Such leaks in through the EPC module typically do not impact runs.) If the setup does not include shutoff valves at the GC, or if changing the source pressure is not practical, skip this step. If there is a relatively large volume in the supply tubing leading up to the GC, consider whether or not there could have been a leak into the system when evaluating the test results.

20 Monitor the pressure for 10 minutes. Use the timer by pressing [Time] and [Enter].

A pressure drop of less than 0.7 psig (0.07 psi/min or less; 4.8 kPa or 0.48 kPa/min) is acceptable.

If the pressure drops much faster than the acceptable rate, see To Correct Leaks in the Packed Column Inlet. Retest.

21 After the inlet passes the test, restore the GC to operating condition.

Remove any caps/plugs.

Restore source pressures.

Reinstall the column.

Restore the correct column configuration.

Load the operating method.

Agilent 7890 Series Troubleshooting

Checking for Leaks 7

To Correct Leaks in the Packed Column Inlet

Agilent 7890 Series Troubleshooting

If the inlet fails a pressure decay test, check the following:

Check the caps/plugs used in the testmake sure each is correctly installed and tight.

If you performed the leak test after performing maintenance, check for proper installation of the part(s) handled during the maintenance.

Check the tightness of the septum nut. See To change the septum on the purged packed inlet. See To change the septum on the purged packed inlet.

Check the septum. Replace if old or damaged.

Check that the top insert weldment is installed tightly.

Replace the O-ring. See To change the O-ring on the purged packed inlet. Also check the glass insert. See To change the glass insert on a PP inlet.

Replace the ferrule seal on the adapter.

Make sure the inlet temperature remained constant during the test.

If these items do not resolve the problem, contact Agilent for service.

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7 Checking for Leaks

To Perform a COC Pressure Decay Leak Test

156

Use the Agilent Instrument Utilities Cool On-Column Inlet Pressure Decay Test to determine if the inlet is leaking. Open the software, select the GC, and run the test for the inlet.

If the Instrument Utilities software is not available, see the procedure below.

If the test fails:

Use an electronic leak detector to check the connections to the flow module. Tighten connections or replace O-rings as needed.

Check the flow module for leaks.

Use an electronic leak detector to check the tubing between the inlet body and the flow module for leaks.

Check the plugged column fitting and the septum purge cap.

Tighten the septum nut.

Replace the septum if necessary.

To Perform a COC Pressure Decay Test

The pressure decay test checks for leaks from the inlet flow module up to the column fitting.

After performing maintenance, first check for leaks in externally accessible areas. See To Check for External Leaks.

If a leak is known to exist, check the externally accessible inlet fittings first, especially any connection that has seen recent maintenance, such as the septum nut, column adapter, column connection, and so forth. See To Check for External Leaks.

The pressure decay leak test described below requires removing the column and capping the inlet column fitting. This test can/cannot find the following types of leaks:

Agilent 7890 Series Troubleshooting

Checking for Leaks 7

Agilent 7890 Series Troubleshooting

1 Gather the following (see Consumables and parts for the COC inlet):

No-hole ferrule

1/4-inch wrench

Heat-resistant gloves (if the inlet is hot)

Column nut

New septum

ECD/TCD Detector plug (part no. 5060-9055)

2 Load the inlet maintenance method and wait for the GC to become ready.

3 Remove the column, if installed.

4 Plug the column fitting with a column nut and no-hole ferrule.

5 Remove the old septum and replace it with a new one. See To change a septum on the COC inlet.

6 Enter a pressure setpoint of 25 psi (172 kPa). Make sure that the pressure supplied to the GC is at least 10 psi (70 kPa) higher than the inlet pressure.

7 Wait 5 minutes for the pressure to equilibrate. If pressure cannot be achieved, there is either a large leak or the supply pressure is too low.

8 Set the Septum purge flow to 3.0 mL/min.

9 Allow the inlet temperature to stabilize. Temperature changes can invalidate the test.

The test can find leaks at the: The test cannot find leaks at the:

septum column fitting

septum nut or cooling tower gas supply bulkhead fittings to the flow module

seals within the tubing between the inlet flow module and the inlet body

inlet body

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7 Checking for Leaks

10 Cap the septum purge fitting with the ECD/TCD detector plug.

Back inlet purge vent

Front inlet purge vent

Back inlet split vent

Front inlet split vent

Front purge vent shown plugged

11 From the keypad, press [Service Mode]. Select Diagnostics > Front or Back Inlet > Pneumatics Control > Septum Purge control.

12 Scroll to the Constant duty cycle and enter 50. Wait 10 seconds.

13 Press [Front or Back Inlet]. Scroll to Pressure and press Off/No.

14 Quickly turn off the carrier gas supply at its source, if possible. The goal is to prevent any residual pressure from the supply lines from leaking into the closed system and causing a pressure rise and masking leaks. (Such leaks in through the EPC module typically do not impact runs.) If the setup does not include shutoff valves at the GC, or if

Agilent 7890 Series Troubleshooting

Checking for Leaks 7

Agilent 7890 Series Troubleshooting

changing the source pressure is not practical, skip this step. If there is a relatively large volume in the supply tubing leading up to the GC, consider whether or not there could have been a leak into the system when evaluating the test results.

15 Monitor the pressure for 10 minutes. Use the timer by pressing [Time] and [Enter].

A pressure drop of less than 1.0 psig (0.1 psi/min or less; 6.9 kPa or 0.69 kPa/min) is acceptable.

If the pressure drops much faster than the acceptable rate, see To Correct Leaks in the Cool On-Column Inlet. Retest.

16 After the inlet passes the test, restore the GC to operating condition.

Restore source pressures.

Remove any caps/plugs.

Reinstall the column.

Restore the correct column configuration.

Load the operating method.

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7 Checking for Leaks

To Correct Leaks in the Cool On-Column Inlet

160

If the inlet fails a pressure decay test, check the following:

Check the caps/plugs used in the testmake sure each is correctly installed and tight.

If you performed the leak test after performing maintenance, check for proper installation of the part(s) handled during the maintenance.

Check the tightness of the septum nut or cooling tower assembly. See To change a septum nut or cooling tower and septum on a COC inlet.

Check the septum. Replace if old or damaged.

Make sure the inlet temperature remained constant during the test.

If these items do not resolve the problem, contact Agilent for service.

Agilent 7890 Series Troubleshooting

Checking for Leaks 7

To Perform a PTV Pressure Decay Test

Agilent 7890 Series Troubleshooting

See the procedure below.

If the test fails:

Check the plugged column fitting and septum purge cap.

Check the septum head. Tighten if needed.

Replace the septum if necessary.

If using a septumless head, tighten. Rebuild as needed.

Inspect and re-install the liner if it is leaking.

Replace the inlet adapter if it is leaking.

Tighten the split vent trap if needed, or install a new cartridge and O-rings.

Tighten the split vent line connection to the inlet.

To Perform a PTV Pressure Decay Test

The pressure decay test checks for leaks from the inlet flow module up to the column fitting.

After performing maintenance, first check for leaks in externally accessible areas. See To Check for External Leaks.

If a leak is known to exist, check the externally accessible inlet fittings first, especially any connection that has seen recent maintenance, such as the septum nut, column adapter, column connection, and so forth.

The pressure decay leak test described below requires removing the column and capping the inlet column fitting. This test can/cannot find the following types of leaks:

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7 Checking for Leaks

1 Gather the following (see Consumables and parts for the PTV inlet):

No-hole ferrule

1/4-inch wrench

Heat-resistant gloves (if the inlet is hot)

Column nut

New septum

New Graphpak 3D ferrule and liner

ECD/TCD Detector plug (part no. 5060-9055)

2 Load the inlet maintenance method and wait for the GC to become ready.

3 Remove the column, if installed.

4 Plug the column fitting with a column nut and a no-hole ferrule.

5 If using the septum head, and the quality of the septum (or Microseal) and GRAPHPACK-3D ferrule on the glass liner are unknown, replace them now. See To change the septum on the PTV inlet and To change the liner on the PTV inlet.

6 Set the inlet to Split Mode.

7 Configure the column as 0 length.

8 Set the inlet temperature to 100 C.

The test can find leaks at the: The test cannot find leaks at the:

septum column fitting

septum nut gas supply bulkhead fittings to the flow module

liner O-ring seal tubing and connections in a transfer line connected to the inlet

gold seal/washer and reducing nut

inlet body

flow manifold split vent valve

flow manifold septum purge valve

split vent tubing and trap

septum purge tubing

seals within the tubing between the inlet flow module and the inlet body

Agilent 7890 Series Troubleshooting

Checking for Leaks 7

Agilent 7890 Series Troubleshooting

9 Set the Total flow to 60 mL/min.

10 Enter a pressure setpoint of 25 psi (172 kPa). Make sure that the pressure supplied to the GC is at least 10 psi (70 kPa) higher than the inlet pressure.

11 If pressure cannot be achieved, there is either a large leak or the supply pressure is too low.

12 Set the Septum purge flow to 3.0 mL/min.

13 Allow the inlet temperature to stabilize. Temperature changes can invalidate the test.

14 Cap the septum purge fitting with the ECD/TCD detector plug.

Back inlet purge vent

Front inlet purge vent

Back inlet split vent

Front inlet split vent

Front purge vent shown plugged

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7 Checking for Leaks

15 From the keypad, press [Service Mode]. Select Diagnostics > Front or Back Inlet > Pneumatics Control > Septum Purge control.

16 Scroll to the Constant duty cycle and enter 50. Wait 10 seconds.

17 Press [Front or Back Inlet]. Scroll to Pressure and press Off/No.

18 Quickly turn off the carrier gas supply at its source, if possible. The goal is to prevent any residual pressure from the supply lines from leaking into the closed system and causing a pressure rise and masking leaks. (Such leaks in through the EPC module typically do not impact runs.) If the setup does not include shutoff valves at the GC, or if changing the source pressure is not practical, skip this step. If there is a relatively large volume in the supply tubing leading up to the GC, consider whether or not there could have been a leak into the system when evaluating the test results.

19 Monitor the pressure for 10 minutes. Use the timer by pressing [Time] and [Enter].

A pressure drop of less than 0.5 psig (0.05 psi/min or less; 3.4 kPa or 0.34 kPa/min) is acceptable.

If the pressure drops much faster than the acceptable rate, see To Correct Leaks in the PTV Inlet. Retest.

Note that liner size impacts pressure drop. An inlet with a smaller volume liner does not tolerate as large a leak rate as an inlet with a larger volume liner.

20 After the inlet passes the test, restore the GC to operating condition.

Restore source pressures.

Remove any caps/plugs.

Reinstall the column.

Restore the correct column configuration.

Load the operating method.

Agilent 7890 Series Troubleshooting

Checking for Leaks 7

To Correct Leaks in the PTV Inlet

Agilent 7890 Series Troubleshooting

If the inlet fails a pressure decay test, check the following:

Check the caps/plugs used in the testmake sure each is correctly installed and tight.

If you performed the leak test after performing maintenance, check for proper installation of the part(s) handled during the maintenance.

If using a septum head, check the tightness of the septum nut. See To change the septum on the PTV inlet.

If using a septum head, check the septum. Replace if old or damaged.

Check that the septumless- or septum- head assembly is installed tightly.

Replace the liner and Graphpak 3D ferrule. See To change the liner on the PTV inlet.

Check the Graphpak adapter seal against the inlet body. Replace the silver seal and reinstall the adapter if needed. See To replace the inlet adapter for the PTV inlet.

If using the septumless head, check for leaks around the guide cap. Replace the PTFE ferrule in the guide cap. See To replace the PTFE ferrule on a PTV inlet.

Check for leaks at the split vent trap. Tighten as necessary. Replace the split vent trap filter and O-rings. See To replace the filter in the PTV inlet split vent line.

Make sure the inlet temperature remained constant during the test.

If these items not resolve the problem, contact Agilent for service.

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7 Checking for Leaks

To Perform a VI Pressure Decay Test

166

See the procedure below.

For information on running the pressure decay test for the VI, refer to your GC user documentation.

If the test fails:

Check the plugged column fitting and septum purge cap.

Tighten the pneumatic connections to the volatiles interface. Install new seals as needed.

Tighten the split vent trap if needed, or install a new cartridge and O-rings.

Tighten the split vent trap if needed, or install a new cartridge and O-rings.

Use an electronic leak detector to check the tubing from the interface to the flow module.

Use an electronic leak detector to check the flow module for leaks.

To Perform a VI Pressure Decay Test

The pressure decay test checks for leaks from the inlet flow module up to the column fitting.

Initially test the VI with a sampling system installed. If the system fails the leak test, then isolate the VI from the sampler as described in To Prepare the VI for a Closed System Leak Check on page 170.

After performing maintenance, first check for leaks in externally accessible areas. See To Check for External Leaks.

If a leak is known to exist, check the externally accessible inlet fittings first, especially any connection that has seen recent maintenance, such as the column connection, split vent line, and so forth.

The pressure decay leak test described below requires removing the column and capping the inlet column fitting. This test can/cannot find the following types of leaks:

Agilent 7890 Series Troubleshooting

Checking for Leaks 7

Agilent 7890 Series Troubleshooting

1 Gather the following (see Consumables and parts for the VI):

No-hole ferrule

1/4-inch wrench

Heat-resistant gloves (if the inlet is hot)

Long column nut

ECD/TCD Detector plug (part no. 5060-9055)

2 Load the inlet maintenance method and wait for the GC to become ready.

3 Remove the column, if installed.

4 Plug the column fitting with a column nut and a no-hole ferrule.

5 Set the inlet to Split Mode.

6 Configure the column as 0 length.

7 Set the inlet temperature to 100 C.

8 Set the Total flow to 60 mL/min.

9 Enter a pressure setpoint of 25 psi (172 kPa). Make sure that the pressure supplied to the GC is at least 10 psi (70 kPa) higher than the inlet pressure.

10 If pressure cannot be achieved, there is either a large leak or the supply pressure is too low.

11 Set the Septum purge flow to 3.0 mL/min.

12 Allow the inlet temperature to stabilize. Temperature changes can invalidate the test.

The test can find leaks at the: The test cannot find leaks at the:

sampler connection column fitting

pressure sensing line connection to the interface

gas supply bulkhead fittings to the flow module

split vent line connection to the interface

tubing and connections in a transfer line connected to the inlet

the connected samplers entire sample flow path

flow manifold split vent valve

flow manifold septum purge valve

split vent tubing and trap

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7 Checking for Leaks

13 Cap the septum purge fitting with the ECD/TCD detector plug.

Back inlet purge vent

Front inlet purge vent

Back inlet split vent

Front inlet split vent

Front purge vent shown plugged

14 From the keypad, press [Service Mode]. Select Diagnostics > Front or Back Inlet > Pneumatics Control > Septum Purge control.

15 Scroll to the Constant duty cycle and enter 50. Wait 10 seconds.

16 Press [Front or Back Inlet]. Scroll to Pressure and press Off/No.

17 Quickly turn off the carrier gas supply at its source, if possible. The goal is to prevent any residual pressure from the supply lines from leaking into the closed system and causing a pressure rise and masking leaks. (Such leaks in through the EPC module typically do not impact runs.) If the setup does not include shutoff valves at the GC, or if

Agilent 7890 Series Troubleshooting

Checking for Leaks 7

Agilent 7890 Series Troubleshooting

changing the source pressure is not practical, skip this step. If there is a relatively large volume in the supply tubing leading up to the GC, consider whether or not there could have been a leak into the system when evaluating the test results.

18 Monitor the pressure for 1015 minutes. Use the timer by pressing [Time] and [Enter].

The pressure should drop approximately 1 psi (6.9 kPa) during the first 1 to 2 minutes. After an initial pressure drop of about 1 psi, the pressure should not drop more than 0.03 psi/min (0.21 kPa/min).

If the pressure drop is 0.03 psi/min or less, you can consider the interface-gas sampler system leak-free.

If the pressure drops faster than the acceptable rate, you must check the interface and sampler systems separately to determine the source of the leak. See To Prepare the VI for a Closed System Leak Check to create a closed flow system, then return to this section and complete steps 10 to 16.

If you find a leak in the interface, refer to To Correct Leaks in the Volatiles Interface.

If the interface is leak-free, pressure check the sampling device. See the operating manual for your sampler for instructions.

19 After the VI passes the test, restore the GC to operating condition.

Restore source pressures.

Remove any caps/plugs.

If needed, reconnect the sampling device.

Reinstall the column.

Restore the correct column configuration.

Load the operating method.

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7 Checking for Leaks

To Prepare the VI for a Closed System Leak Check

170

To leak check the interface independently of the gas sampling device, you must disconnect the sampler from the interface to isolate the interface flow system from the sampler.

WARNING Be careful! The oven and/or inlet may be hot enough to cause burns. If either is hot, wear heat-resistant gloves to protect your hands.

1 Gather the following:

1/16-inch nut for transfer line

Ferrule for transfer line

Heat-resistant gloves (if the inlet is hot)

2 Disconnect the transfer line from the interface.

3 Disconnect the carrier line from the sampler.

4 Prepare the end of the carrier line using a 1/16-inch male nut and ferrule.

5 Connect the carrier line to the interface where you removed the transfer line and tighten the nut finger tight. Tighten an additional 1/4 to 1/2 turn with the 1/4-inch wrench.

6 Return to To Perform a VI Pressure Decay Test and repeat steps 9 to 16.

Agilent 7890 Series Troubleshooting

Checking for Leaks 7

To Correct Leaks in the Volatiles Interface

Agilent 7890 Series Troubleshooting

If the inlet fails a pressure decay test, check the following:

The caps and plugs used in the testmake sure each is correctly installed and tight.

If you performed the leak test after performing maintenance, check for proper installation of the part(s) handled during the maintenance.

The split vent and pressure sensing connections at the interface.

The sampler connection to the interface.

The sampler.

If these items do not resolve the problem, contact Agilent for service.

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7 Checking for Leaks

Agilent 7890 Series Troubleshooting

Agilent 7890 Series Gas Chromatograph Troubleshooting

8 Troubleshooting Tasks To Measure a Column Flow 174 To Measure a Split Vent or Septum Purge Flow 178 To Measure a Detector Flow 180 To Perform the GC Self-Test 185 To Check or Monitor Split Vent Line Backpressure 186 To Run the Inlet Trap Check 189 To Perform a SS Split Vent Restriction Test 191 To Check a Split Vent Line for Contamination 192 To Adjust the FID Lit Offset 194 To Verify That the FID Flame Is Lit 195 To Verify FID Ignitor Function During Ignition Sequence 196 To Measure FID Leakage Current 197 To Measure FID Baseline Output 198 To Isolate the Cause of FID Noise 199 To Measure NPD Leakage Current 200 To Check for a Plugged FID Jet 201 To Check for a Plugged NPD Jet 202 To Verify That the NPD Bead Is Ignited 203 To Verify That the FPD Flame Is Lit 204 To Adjust the FPD Lit Offset 205 When to Change Gas Purifiers 206 To Ignore a Devices Readiness State 207 To Use the Stopwatch 208

173Agilent Technologies

8 Troubleshooting Tasks

To Measure a Column Flow

Measuring FID, TCD, uECD, and FPD column flow

174

The following procedure can be used to measure column flow with an FID, TCD, uECD, and FPD.

WARNING Hydrogen (H2) is flammable and is an explosion hazard when mixed with air in an enclosed space (for example, a flow meter). Purge flowmeters with inert gas as needed. Always measure gases individually. Always turn off detectors to prevent flame/bead autoignition.

WARNING Be careful! The detector may be hot enough to cause burns. If the detector is hot, wear heat-resistant gloves to protect your hands.

1 Gather the following:

Appropriate flowmeter adapter tube (can be found in the GC ship kit)

Electronic flowmeter calibrated for the gas and flow rates of concern

2 Turn off the detector.

3 Turn off the detector flows.

4 Connect the appropriate adapter to the detector exhaust.

NOTE Flowmeter tube diameters vary by model; modify the adapter to the flowmeter tubing as needed.

A 1/8-in rubber adapter tube attaches directly to a uECD or TCD exhaust vent.

A separate adapter (19301-60660) is supplied for the FID. Insert the adapter into the detector exhaust vent as far as possible. You will feel resistance as the adapter O-ring is forced into the detector exhaust vent. Twist and push the adapter during insertion to ensure a good seal.

Agilent 7890 Series Troubleshooting

Troubleshooting Tasks 8

Agilent 7890 Series Troubleshooting

For the FPD, remove the plastic tubing from the FPD exhaust and connect the flowmeter directly to the FPD vent tube. If necessary, use a 1/4-inch tube adapter between the detector exhaust and the flowmeter tubing.

5 Connect the flowmeter to the flowmeter adapter to measure flow rates.

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8 Troubleshooting Tasks

Measuring NPD column flow

176

1 Gather the following:

NPD flowmeter adapter tool (G1534-60640)

Flow-measuring insert (19301-60660)

Electronic flowmeter calibrated for the gas and flow rates of concern

2 Set the bead voltage to 0.0 V.

3 Cool the NPD to 100 C.

WARNING Be careful! The detector may be hot enough to cause burns. If the detector is hot, wear heat-resistant gloves to protect your hands.

4 Remove the bead and store it carefully until reinstallation.

5 Insert the NPD flowmeter adapter tool into the NPD collector.

Agilent 7890 Series Troubleshooting

Troubleshooting Tasks 8

Agilent 7890 Series Troubleshooting

6 Attach the flow-measuring insert to the NPD flowmeter adapter tool.

7 Place the flowmeter tubing over the flow-measuring insert to begin measuring flows.

177

8 Troubleshooting Tasks

To Measure a Split Vent or Septum Purge Flow

178

Note that the GC reports flows calibrated to 25 C and 1 atmosphere. Correct flowmeter results accordingly.

WARNING Hydrogen (H2) is flammable and is an explosion hazard when mixed with air in an enclosed space (for example, a flow meter). Purge flowmeters with inert gas as needed. Always measure gases individually. Always turn off detectors to prevent flame/bead autoignition.

Septum purge and split vent flows exit through the pneumatic module at the top rear of the GC. See the figure below.

Back inlet purge vent

Front inlet purge vent

Back inlet split vent

Front inlet split vent

To measure split vent or septum purge flows, attach the flowmeter to the appropriate tube. Remove the GC pneumatics cover to access the back inlet exhausts.

Agilent 7890 Series Troubleshooting

Troubleshooting Tasks 8

Agilent 7890 Series Troubleshooting

The split vent has a 1/8-in Swagelok threaded fitting. Create and use a 1/8-in tube adapter (as shown below) to convert the 1/8-in threaded fitting into a 1/8-in tube. This prevents the rubber flowmeter tubing from leaking around the threads, which will result in leakage and thus an incorrect flow reading.

The septum purge is a 1/8-in tube. Use the red rubber adapter shown to measure flows.

179

8 Troubleshooting Tasks

To Measure a Detector Flow

180

Detectors, especially detectors with flame, require precise flow measurements to function properly. Incorrect flows are caused by:

Restrictions in the supply line, which will cause a Not Ready message on the GC display (all detectors)

A leaking column or column adapter fitting (all detectors)

A plugged jet (FID, NPD).

A leak in the burner chamber, window seal, or ignitor seal (FPD)

A pressure sensor that needs to be zeroed. (See To Zero the EPC Module Pressure Sensor.)

An EPC valve that is not operating correctly.

To isolate the problem, compare the flow of one channel of gas against the actual flow rate.

Measuring FID, TCD, uECD, and FPD flows

WARNING Hydrogen (H2) is flammable and is an explosion hazard when mixed with air in an enclosed space (for example, a flow meter). Purge flowmeters with inert gas as needed. Always measure gases individually. Always turn off detectors to prevent flame/bead autoignition.

1 Gather the following:

Appropriate flowmeter adapter tube (can be found in the GC ship kit)

Electronic flowmeter calibrated for the gas and flow rates of concern

CAUTION To avoid damaging the column, cool the oven before turning off the column flow.

2 Set the oven temperature to ambient (35 C).

3 Turn off the column flow and pressure.

4 Shut off all detector gases.

Agilent 7890 Series Troubleshooting

Troubleshooting Tasks 8

Agilent 7890 Series Troubleshooting

5 Turn off (where applicable): the FID flame, FPD flame, and TCD filament.

6 Cool the detector.

7 Connect the appropriate adapter to the detector exhaust.

NOTE Flowmeter tube diameters vary by model; modify the adapter to the flowmeter tubing as needed.

A rubber adapter tube attaches directly to a uECD, or TCD exhaust vent.

A separate adapter (19301-60660) is supplied for the FID. Insert the adapter into the detector exhaust vent as far as possible. You will feel resistance as the adapter O-ring is forced into the detector exhaust vent. Twist and push the adapter during insertion to ensure a good seal.

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8 Troubleshooting Tasks

For the FPD, remove the plastic tubing from the FPD exhaust and connect the flowmeter directly to the FPD vent tube. If necessary, use a 1/4-inch tube adapter between the detector exhaust and the flowmeter tubing.

8 Connect the flowmeter to the flowmeter adapter.

9 Measure the actual flow rate of each gas one at a time.

Agilent 7890 Series Troubleshooting

Troubleshooting Tasks 8

Measuring NPD flows

Agilent 7890 Series Troubleshooting

1 Gather the following:

NPD flowmeter adapter tool (G1534-60640)

Flow-measuring insert (19301-60660)

Electronic flowmeter calibrated for the gas and flow rates of concern

2 Set the bead voltage to 0.0 V.

3 Cool the NPD to 100 C.

WARNING Be careful! The detector may be hot enough to cause burns. If the detector is hot, wear heat-resistant gloves to protect your hands.

4 Remove the bead and store it carefully until reinstallation.

5 Insert the NPD flowmeter adapter tool into the NPD collector.

183

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8 Troubleshooting Tasks

6 Attach the flow-measuring insert to the NPD flowmeter adapter tool.

7 Place the flowmeter tubing over the flow-measuring insert to begin measuring flows.

Agilent 7890 Series Troubleshooting

Troubleshooting Tasks 8

To Perform the GC Self-Test

Agilent 7890 Series Troubleshooting

1 Turn the GC off.

2 Wait 1 min, then turn the GC back on. If the main GC status screen appears, the GC has passed the self-test.

185

8 Troubleshooting Tasks

To Check or Monitor Split Vent Line Backpressure

186

Agilent provides a built-in test that measures backpressure in the split vent trap and line for the split/splitless, multimode, PTV, and VI inlets. The test measures the pressure developed in the split vent flow path at a given, user-selected flow rate. This flow rate can be your method Split flow setpoint, or the default 400 mL/min used by Agilent to compare typical values.

By running the test on a clean system, you can establish a baseline for expected backpressure in the split vent line. Then, you can re-run the test periodically to determine whether or not the trap needs to be replaced before it impacts your chromatography.

The pressure measured by the test depends on:

The liner installed

The flow rate used

Therefore, the actual measured value will vary between different setups and from GC to GC.

The test checks for:

Liner restriction

Contamination on the gold seal (split/splitless inlet only)

Restrictions in the split vent line, such as condensed sample contamination in the split vent line and trap

The test can also provide a measure of suitability for the installed hardware. Run the test using your methods setpoints and hardware. If the measured test pressure is close to the desired column head pressure, this means that even a minor amount of restriction in the split vent line can cause the GC to become not ready. You may wish to install a different liner or adjust the method. (For splitless liners, first try reinstalling the liner. Splitless liners create more backpressure than split liners, and so minor variations in orientation can make a difference at low head pressures.)

To set a warning limit for the inlet trap check

To use the inlet trap check to monitor the split vent trap:

1 If the existing split vent trap has been used for many sample injections, replace it. Make sure that the GC is clean:

Replace inlet hardware if needed.

Agilent 7890 Series Troubleshooting

Troubleshooting Tasks 8

Agilent 7890 Series Troubleshooting

Check that the split vent line is free from contamination or restrictions.

2 Run the inlet trap check. See To Run the Inlet Trap Check.

3 Note the pressure. This reading is the backpressure you can expect from a clean system with the installed liner.

4 Determine a practical split vent backpressure limit.

Use the GC normally. Periodically rerun the inlet trap check. You will need to change the split vent trap when either:

You see chromatographic issues related to a restriction in the split vent, typically poor split mode area repeatability, or

The reported test pressure approaches or exceeds the method column head pressure setpoint.

Run the inlet trap check and note the pressure. Change the split vent trap.

5 Set a warning limit and behavior, if desired.

Now that you know when the trap needs to be changed, you can set one or two limits in the test. Use these limits to set the service due indicator, or to force the GC to go Not ready. The two limits are:

Warning if pressure check: If the measured pressure exceeds the limit, turn on the service due indicator.

Fault if pressure check: If the measured pressure exceeds the limit, make the GC Not Ready.

To set a warning limit:

a Press [Service Mode], scroll to Front inlet trap check or to Back inlet trap check, then press [Enter].

b Scroll to the desired limit.

c Enter a limit using the keypad, then press [Enter].

(To disable a warning, select it then press [Off/No].)

The test is now set up.

6 Periodically rerun the test. When the test fails, replace the split vent trap.

To clear a Not Ready condition or to turn off the Service Due indicator:

1 Press [Service Mode], scroll to Front inlet trap check or to Back inlet trap check, then press [Enter].

2 Scroll to Reset the test results? and press [On/Yes].

187

8 Troubleshooting Tasks

To disable a warning limit for the inlet trap check

188

1 Press [Service Mode], scroll to Front inlet trap check or Back inlet trap check, then press [Enter].

2 Scroll to the warning, then press [Off/No].

Agilent 7890 Series Troubleshooting

Troubleshooting Tasks 8

To Run the Inlet Trap Check

Agilent 7890 Series Troubleshooting

From the GC keypad:

1 Press [Service Mode], scroll to Front inlet trap check or Back inlet trap check, then press [Enter]. The display will be similar to Figure 5:

Figure 5 Example front inlet trap check display. Example assumes a test has been previously run. Scroll to see all lines of the display.

2 Scroll to Test flow rate and enter a flow rate. A typical flow rate for this test is 400 mL/min for helium and hydrogen carrier gas, or 150 ml/min for nitrogen carrier gas, but you may find other values more appropriate for your setup.

3 Scroll to Test Inlet and press [On/Yes] to start the test.

4 Wait while the pressure stabilizes. When stable, the Test Inlet line of the display changes to Test pressure OK x.xx, where x.xx is the current pressure.

If the inlet cannot achieve the test setpoint, check for a leak (at the inlet, split vent trap, or split vent line) or low supply gas pressure.

5 Note the resulting Inlet Pressure. If the measured pressure exceeds any limits you have set up, the GC will respond accordingly. See To Check or Monitor Split Vent Line Backpressure.

Typical pressures for a clean split flow path are:

12 psi (714 kPa) at 400 mL/min for a split liner

310 psi (2169 kPa) at 400 mL/min for a splitless liner

FRONT INLET TRAP CHECK Inlet Pressure 5.471 psi< Test Inlet (ON to Start) Test flow rate 400mL/min Warning if pressure check OFF Fault if pressure check OFF Last test results Tue Oct 20 16:07 2009 Test pressure OK: 4.8 Reset the test results? (yes)

189

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8 Troubleshooting Tasks

If the pressure for a splitless liner seems abnormally high for a clean system, try reinstalling the liner.

If pressure on a clean system is within these ranges, but is near the operating pressure for the method, consider a change in hardware or the method. See also Cannot Maintain a Pressure as Low as the Setpoint on a Split Inlet.

6 Press [Off/No] to stop the test.

NOTE The most recent test results display at the bottom of the display. Scroll down to see them.

To clear a Not Ready condition or Service Due indicator, scroll to Reset the test results? and press [On/Yes].

Agilent 7890 Series Troubleshooting

Troubleshooting Tasks 8

To Perform a SS Split Vent Restriction Test

Agilent 7890 Series Troubleshooting

Use the Agilent Instrument Utilities Split Vent Restriction Test to determine if there is an abnormal restriction in the split vent flow path. Open the software, select the GC, and run the test for the inlet. (Alternately, see To Run the Inlet Trap Check.)

If the test fails:

Consider whether the setup exceeds the minimum viable pressures obtainable by the GC. See also Table 4.

Consider the liner used. Agilent recommends a low pressure-drop liner for split analyses, part number 5183-4647.

Replace the split vent trap filter.

Inspect and replace the gold seal. If not using the low pressure drop liner, consider installing a high-flow gold seal, 5182-9652.

Check for contamination in the split vent line. See To Check a Split Vent Line for Contamination.

If the problem remains, contact Agilent for service.

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8 Troubleshooting Tasks

To Check a Split Vent Line for Contamination

192

This procedure applies to the multimode and split/splitless inlets.

WARNING Be careful! The oven, inlet, and/or detector may be hot enough to cause burns. If the oven, inlet, or detector is hot, wear heat-resistant gloves to protect your hands.

1 Gather the following:

7/16-inch wrench

Wrench, hex for changing septum

Heat-resistant gloves if the inlet is hot

Cleaning brushes

2 Load the inlet maintenance method and wait for the GC to become ready.

3 Loosen the 1/8-inch Swagelok nut that seals the copper split vent line to the injection port.

4 Inspect the 1/8-inch copper split line for condensed sample. Flush or replace the copper split vent line.

5 Remove the septum head.

6 Check the split tube fitting in the shell weldment for blockage. Clean the split tube with a brush and suitable solvent.

7 Reassemble the split/splitless inlet and run the split vent restriction test to test for restrictions in the split vent flow path. If the inlet still fails, suspect flow module contamination or defects.

Agilent 7890 Series Troubleshooting

Troubleshooting Tasks 8

Agilent 7890 Series Troubleshooting

8 Check for leaks. Run the pressure decay test. See To Perform a SS Pressure Decay Leak Test or To Perform a MMI Pressure Decay Leak Test.

193

8 Troubleshooting Tasks

To Adjust the FID Lit Offset

194

To adjust the FID Lit offset: 1 Press [Config]. 2 Scroll to Front detector or Back detector (wherever the detector

is installed) and press [Enter]. 3 Scroll to Lit offset. With the Lit offset line highlighted, enter the

new parameter for the detector and press [Enter]. 4 Lit offset should be < 2.0 pA or lower than the normal FID

output when lit.

Agilent 7890 Series Troubleshooting

Troubleshooting Tasks 8

To Verify That the FID Flame Is Lit

Agilent 7890 Series Troubleshooting

To verify that the FID flame is lit, hold a mirror or other reflective surface over the collector exhaust. Steady condensation indicates that the flame is lit.

Typically the FID output will be between 5.0 and 20.0 pA when lit and < 2.0 pA when not lit.

If the flame does not light, do the following:

Verify that the detector temperature is above 150 C. Agilent recommends operating the FID 300 C.

Verify correct detector flows.

Inspect the jet for contamination.

Verify that the jet is installed correctly.

Check the column connections for leaks.

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8 Troubleshooting Tasks

To Verify FID Ignitor Function During Ignition Sequence

196

WARNING Keep body parts at a safe distance from the FID chimney while performing this task. If using hydrogen, the FID flame will not be visible.

1 Remove the detector top cover.

2 Turn the FID flame On. 3 Observe the ignitor plug though the FID chimney. The small

hole should glow during ignition sequence.

Agilent 7890 Series Troubleshooting

Troubleshooting Tasks 8

To Measure FID Leakage Current

Agilent 7890 Series Troubleshooting

1 Load the analytical method.

Make sure flows are acceptable for ignition.

Heat the detector to operating temperature or to 300 C.

2 Turn off the FID flame.

3 Press [Front Det] or [Back Det], then scroll to Output. 4 Verify that the output is stable and < 1.0 pA.

If the output is unstable or > 1.0 pA, turn off the GC and check for proper assembly of the upper FID parts and for contamination. If the contamination is confined to the detector, bakeout the FID.

5 Turn on the flame.

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8 Troubleshooting Tasks

To Measure FID Baseline Output

198

1 With the column installed, load your checkout method.

2 Set the oven temperature to 35 C.

3 Press [Front Det] or [Back Det], then scroll to Output. 4 When the flame is lit and the GC is ready, verify that the

output is stable and < 20 pA (this may take some time).

5 If the output is not stable or > 20 pA, the system or gas may be contaminated. If this contamination is isolated to the detector, bakeout the FID.

Agilent 7890 Series Troubleshooting

Troubleshooting Tasks 8

To Isolate the Cause of FID Noise

Agilent 7890 Series Troubleshooting

FID noise is the result of mechanical, electrical and chemical factors. FID noise can be a subjective parameter. Often FID baseline noise is perceived based on history of a given detector or comparison with another detector in the lab. For proper diagnosis of noise it is important to evaluate the detector noise under documented conditions against a known standard. Find more detailed information about noise in Noisy Detector, Including Wander, Drift, and Baseline Spikes.

Before troubleshooting the detector, perform a noise test using your Agilent data system. If the detector fails the noise test, then troubleshoot the cause as described below.

To isolate the cause of FID noise:

1 If the noise test fails, remove the column and re-evaluate detector noise with the FID capped and re-ignited, using only H2/air and makeup detector gases. If it passes, suspect contaminated column/carrier gas.

2 If the noise failed with no column installed, repeat the noise test with only H2 and air - set makeup flow to "Off". If it passes, suspect contaminated makeup gas.

3 If the noise test still fails, see To Measure FID Leakage Current. If the leakage test fails, replace or clean the collector and PTFE insulators, the interconnect with spring, and/or the entire FID electrometer assembly. If the leakage test fails, replace or clean the collector and PTFE insulators, the interconnect with spring, and/or the entire FID electrometer assembly.

4 If the leakage current test is OK, suspect a contaminated jet or contaminated H2 or Air detector gas supplies (gases, tubing, traps), especially if the background of the detector when lit is >20 pA.

199

8 Troubleshooting Tasks

To Measure NPD Leakage Current

200

1 Load the analytical method.

2 Set the NPD Adjust Offset to Off and the Bead Voltage to 0.00 V.

Leave the NPD at operating temperature.

Leave flows on or off.

3 Press [Front Det] or [Back Det], then scroll to Output. 4 Verify that the output (leakage current) is stable and

< 1.0 pA.

5 The output should slowly drop toward 0.0 pA, and should stabilize in the tenths of a picoamp. Current > 2.0pA indicates a problem.

If the current is > 2.0pA, do the following:

Inspect the jet for contamination.

Check the column or column adapter fitting for leaks.

Ensure that the metal sealing ring is not crushed or misaligned. See To Maintain the NPD Collector, Ceramic Insulators, and Jet

Agilent 7890 Series Troubleshooting

Troubleshooting Tasks 8

To Check for a Plugged FID Jet

Agilent 7890 Series Troubleshooting

The most common cause of FID ignition problems is a plugged or partially plugged jet. If the jet is not completely plugged and the flame still ignites, a secondary symptom will be lengthening peak retention times. Jet plugging is most common with thick-film/high bleed or packed columns and high temperature applications. It is best to operate the column oven within the temperature limits of the column and also to operate the FID at least 20 C hotter than the maximum oven temperature in the GC method. If the FID jet is becoming plugged, actual H2, Makeup and Capillary carrier flows will be lower than the values indicated by the GC.

To check for a plugged FID jet:

1 Leave the column installed in the FID. If already removed, cap off the detector column fitting in the oven. (Leaving the column installed will determine if the column is installed too high in the jet, plugging the orifice.)

2 Set the makeup flow to Off. Confirm a reading on the GC display of 0.0 mL/min for actual makeup flow. If not 0.0 follow the procedure To Zero the EPC Module Pressure Sensor.

3 Set the hydrogen flow to 75 mL/minute (increase the H2 supply pressure as needed to achieve this flow rate setting.)

4 Monitor the makeup flow Actual reading

If the makeup flow is indicating a value in excess of 1.0 mL/min, this indicates that the jet is plugged or partially plugged; pressure is backing up from the H2 channel into the makeup channel of the EPC system, resulting in a false flow indication on the makeup channel.

Alternately, remove the jet from the housing and hold it up to a light source. Check the holes in the jet for contamination. If plugged, replace the jet.

201

8 Troubleshooting Tasks

To Check for a Plugged NPD Jet

202

The detector EPC module controls flow by maintaining a calibrated gas pressure against a fixed restriction. A plugged jet will cause inaccurate flow readings.

To check for a plugged NPD jet, measure the actual hydrogen and makeup flows. (See Measuring NPD flows.) If the flows are lower than the displayed values, replace the jet.

Agilent 7890 Series Troubleshooting

Troubleshooting Tasks 8

To Verify That the NPD Bead Is Ignited

Agilent 7890 Series Troubleshooting

WARNING Hot exhaust! Detector exhaust is hot and can cause burns.

To verify that the bead is ignited, look through the vent hole on the detector lid to see if the bead is glowing orange.

The NPD output is selected by the operator as part of the adjust offset process and generally is between 5.0 and 50.0 pA.

203

8 Troubleshooting Tasks

To Verify That the FPD Flame Is Lit

204

To verify that the FPD flame is lit:

1 Remove the rubber drip tube from the detector vent.

2 Hold a mirror or shiny surface near the aluminum exhaust tube. Steady condensation means that the flame is lit.

Agilent 7890 Series Troubleshooting

Troubleshooting Tasks 8

To Adjust the FPD Lit Offset

Agilent 7890 Series Troubleshooting

To adjust the FPD Lit offset: 1 Press [Config]. 2 Scroll to Front detector or Back detector (wherever the detector

is installed) and press [Enter]. 3 Scroll to Lit offset. With the Lit offset line highlighted, enter the

new parameter for the FPD (typical value is 2.0 pA), and press [Enter].

205

8 Troubleshooting Tasks

When to Change Gas Purifiers

206

Agilent highly recommends using purifying traps in the gas lines to prevent impurities from entering and contaminating the GC system or damaging the column. Some traps are single-purpose for the removal of oxygen, moisture, or hydrocarbons, while combination traps remove all those contaminants.

The best way to know when it is time to change a trap is to use an indicating trap, which should be placed after a high capacity trap. Agilent recommends using glass indicating traps such the Gas Clean Filter system, whose clear tubes display a distinct color change in response to contamination. This color change tells the analyst it is time to change traps.

If no indicating traps are used, it is best to follow the manufacturers recommendation for replacement frequency. Typically, the manufacturer will state how many gas cylinders can be purified with a given trap. If desired, it is possible to estimate when to replace the trap by performing a rough calculation. For example: you have a standard K size cylinder with He at 99.995% purity that contains 7,800 L of He. Assuming a worst case scenario in which the remaining 0.005% is all oxygen, you should have 39 mL, or about 56 mg of O2 in the tank. Agilents OT3 oxygen trap, for example, has a capacity of 600 mg O2. Therefore, you need to replace the OT3 trap every 10 cylinders. This is just a rough estimate, and it is prudent to change traps too early rather than too late.

Agilent 7890 Series Troubleshooting

Troubleshooting Tasks 8

To Ignore a Devices Readiness State

Agilent 7890 Series Troubleshooting

By default, the GC monitors the status of all configured devices (inlets, detectors, valve box heaters, valves, oven heater, EPC modules, and so forth) and becomes ready when all of them reach setpoint. If the GC senses a problem in one of these devices, the GC will either never become ready, or may go into a shutdown state to protect itself or prevent a safety hazard. However, there may be a time when you do not wish to have the readiness state of a device prevent a run from starting. An important example is when an inlet or detector heater is defective. Normally, this fault prevents the GC from becoming ready and starting a run. However, you can set the GC to ignore this problem so that you can use the other inlet or detector until the device is repaired.

Not all devices can be ignored. You can ignore the readiness state of inlets, detectors, the oven, or an EPC module. The readiness state of other devices and components can never be ignored, for example, injection devices such as a switching valve or automatic liquid sampler.

To ignore the status of a device:

1 Turn off the devices heater and gas flows as applicable. (Make sure that it cannot create a safety hazard.)

2 Press [Config], then select the element.

3 Scroll to Ignore Ready and press [On/Yes] to set it to True.

You can now use the GC until the device is repaired.

CAUTION Do not ignore the readiness state of a device that is being used unless you do not care if it reaches setpoint. Be sure to return a broken device to Ignore Ready = False after it is repaired. Otherwise, its state (temperature, flow, pressure, and so forth) will continue to be ignored, even if using this device in the analysis.

To consider a devices readiness, set Ignore Ready to False.

207

Agilent Technologies

To Use the Stopwatch

In the stopwatch mode, both the time (to 0.1 second) and reciprocal time (to 0.01 min1) are displayed. Use the stopwatch when measuring flows with a bubble flowmeter.

1 Press [Time] and scroll to the time = line.

2 Press [Enter] to start the stopwatch.

3 Press [Enter] again to stop.

4 Press [Clear] to set to zero.

You can access other functions while the stopwatch is running. Press [Time] again to view the st

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