Agilent 8697 Headspace Sampler Operation Manual PDF

Agilent 8697 Headspace Sampler

Operation

Notices Agilent Technologies, Inc. 2021

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

Manual Part Number G4511-90004

Edition First edition, February 2021

Printed in USA or China

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 warran- ties, 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 fit- ness 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 con- trol.

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.

3 Operation

Contents

1 Introduction

Introduction 7

Headspace Techniques 8

Static Headspace Sampling Using a Valve and Loop 9

The Agilent 8697 Headspace Sampler 12

About This Manual 13

Getting Familiar with the Headspace Sampler 14 Status indicator LED 15 Park button and indicator 15

2 The Operation Workflow

Routine Operation Workflow 17

Method Development Workflow 18

3 Consumables

Consumables for Headspace Analysis 21

4 Sample Vials

Sample Vial Types 25

Sample Vial Septa and Caps 26

Vial Labels 27 Supported barcodes 28

Filling Sample Vials 29

Cap a Sample Vial 30 Cap a sample vial using a manual crimper 30 Verify proper crimping 32

Park or Unpark the Tray 33

Install a Vial Rack 34

Load a Sample into the Tray 35

5 HS Method Parameters

HS Method Parameters 37 Local user interface 37 Browser interface 39

Operation 4

Method Parameter Summary 40

Determine the GC Cycle Time 42 Determine the GC cycle time 42 Validate the GC cycle time 43

6 HS Sequences

What Is a HS Sequence? 45

Sequences, Extraction Modes, and Vial Punctures 46

Sequences and Throughput 47

Priority Samples 48

Method Sequence Actions 49 Types of sequence issues handled 49 Available actions 49 When using an MS 50

Browser Interface and Data System Sequence Actions 51

Stop, Abort, or Pause a Running Sequence 52

Vial Status 53

7 Settings

Headspace Settings 55 Settings > Configuration > Headspace 55 Settings > Calibration > Headspace 56 Settings > Service Mode > Headspace 58 Settings > Scheduler: Resource Conservation 59

8 How the 8697 Headspace Sampler Works

How the HS Processes a Sample Vial 61

How the HS Equilibrates a Vial 62

How the HS Pressurizes a Vial 63 Flow to pressure 63 Pressure 63 Constant Volume 63 Dynamic leak check 64

How the HS Fills the Sample Loop (Extracts a Sample) 65 Default loop fill mode 65 Custom loop fill mode 65

5 Operation

Types of HS Extractions and Injections 66 Standard extraction 67 Multiple headspace extractions 68 Concentrated headspace extractions 68 Venting residual vial pressure 68

How the HS Reduces Carryover 69

9 Method Development

Overview 71

Consider the Sample and Matrix 72 Theory of headspace analysis 72 Impact of K and phase ratio 73

Consider the GC Inlet 75

Load a Similar Method 76

Edit the New Method 77 Temperatures 77 Times 77 Vial and Loop 78 Fill Modes 78 Venting and Purging 80 Other parameters 81

Developing and Improving the Method 82 Using parameter increment 82 Vial size 83 Vial shaking 84 Sample loop size 84 Pressurizing the vial 84 Filling the sample loop 85 Extraction mode 87

Optimizing Throughput 88

Setting Up for a New Method 89

Perform Blank Runs 90

10 Early Maintenance Feedback

HS Early Maintenance Feedback 93

Operation 6

1 Introduction Introduction 7

Headspace Techniques 8

Static Headspace Sampling Using a Valve and Loop 9

About This Manual 13

Getting Familiar with the Headspace Sampler 14

This chapter introduces the Agilent 8697 Headspace Sampler instrument, identifying major components and general headspace sampling techniques.

1 Introduction Introduction

7 Operation

Introduction Headspace analysis is a technique for analyzing volatile organic compounds using gas chromatography. Headspace analysis samples the ambient volume above a sample matrix, where the volatile compounds exist in gaseous form at predictable levels.

Headspace analysis is useful for situations where:

The analyte of interest is volatile at temperatures below 300 C.

The sample matrix is a solid, paste, or a liquid that is not easy to inject into a GC inlet.

Sample preparation to allow easy liquid injection is currently difficult.

Headspace analysis provides several advantages over traditional injections:

Simpler sample preparation. The sample does not need to be processed into an injectable liquid.

Directly analyze a wide range of sample matrices (liquids, solids, and pastes).

Columns last longer, with less maintenance. The headspace volume above the sample matrix is cleaner than the matrix. By injecting fewer contaminants, the analytical column lasts longer and requires less maintenance (trimming, bakeout, guard column replacement, and so forth).

High precision.

1 Introduction Headspace Techniques

Operation 8

Headspace Techniques At this time, there are three main techniques for performing headspace analysis.

Dynamic headspace sampling: This technique, typically part of a purge and trap system, uses a continuous flow of carrier gas to purge any volatile components from the sample matrix. These analytes are usually trapped in an adsorbant. After a specified time, the trap is heated, releasing the adsorbed compounds, which are swept into the GC inlet.

Static headspace sampling: This technique uses a closed sample container and a sampling system. After placing the sample matrix into the sealed sampling vial, the sample matrix is heated for a specified time, during which the vial can also be agitated (shaken) to help drive volatile compounds from the matrix and into the headspace volume. After a specified time, the vial is punctured, pressurized, and an amount of the headspace vapors are withdrawn and injected into the GC inlet.

Solid Phase Micro Extraction: In this technique, a probe with an adsorbant is placed into a vial that contains the sample matrix. The analytes of interest adsorb into the sample probe. Use of different adsorbants provides flexibility for analyzing different compounds of interest (while ignoring others). After a specified time, the probe is heated to drive off the analytes, which are swept onto the GC column.

1 Introduction Static Headspace Sampling Using a Valve and Loop

9 Operation

Static Headspace Sampling Using a Valve and Loop

There are two main static sampling headspace techniques, pressure-transfer and valve and loop. (A third technique, performing the injection manually using a gas-tight syringe, does not provide easily reproducible results.)

The valve and loop system, as used in the 8697, also heats and agitates the vial for a specified time. However, the Agilent system uses a sample loop of known volume to collect the sample. The sampling steps for the valve and loop system are:

1 Introduction Static Headspace Sampling Using a Valve and Loop

Operation 10

1 A needle probe punctures the vial.

2 The sampler pressurizes the vial with gas. See Figure 1.

Figure 1. Valve and loop system sampling and injection stages

1

2

3 4

5

6

Sample probe

Carrier gas Vent

1

2

3 4

5

6

6 port valve

Transfer line Sample loop

Sample probe

Carrier gas Vial pressurization gas

1

2

3 4

5

6

Sample probe

Carrier gas Vent

Vial pressurization

Sample loop filling

Injection

1 Introduction Static Headspace Sampling Using a Valve and Loop

11 Operation

3 After equilibration at pressure, the pressurized vial gases vent through the sample loop, filling the loop with sample. Note that the vial vents to atmospheric pressure in this case, not to a high column head pressure. Also, the 8697 can control the flow of gas into the sample loop so that the sampling ends before the vial completely depressurizes.

4 After the sample loop equilibrates, the valve switches and the sample loop becomes part of the flow path into the GC inlet. The carrier gas sweeps the known sample amount into the GC inlet for analysis.

1 Introduction The Agilent 8697 Headspace Sampler

Operation 12

The Agilent 8697 Headspace Sampler The Agilent 8697 Headspace Sampler (HS) is a valve and loop headspace sampling system with a 48-vial capacity. The HS uses a 12 vial oven for equilibrating samples at temperature. Since the longest hold time in headspace analysis is typically the equilibration time, using a multi-vial oven allows the HS to increase throughput by equilibrating multiple vials at once.

The 8697 HS is controlled through the GC touchscreen, browser interface, or data system connection. It extends the existing GC settings to include the HS method parameters, configuration settings, early maintenance feedback tracking, log entries, current status displays, and so forth. The 8697 HS is an integrated GC component.

To distinguish between GC and HS status entries, the touchscreen and the browser interface status displays will prepend Headspace to distinguish the HS entries from the GC entries. So, the touchscreen might display 8697 HS oven temperature as Headspace Oven Temperature, and the GC oven temperature will have no prefix or annotation. For example, see the figure below.

Figure 2. Example Headspace Status items

1 Introduction About This Manual

13 Operation

About This Manual This manual describes the concepts and tasks needed for routine headspace sampler operation, as well as the information needed to perform more advanced tasks and method development.

1 Introduction Getting Familiar with the Headspace Sampler

Operation 14

Getting Familiar with the Headspace Sampler

Figure 3. Front view

Figure 4. Back view

Tray gantry

Transfer line Tray

Vial racks

On/Standby switch

Status indicator

Park button

Communications connection

Power plug

Voltage label

Carrier gas connection

Tray connections

Vial pressurization gas connection

Vent connection

1 Introduction Status indicator LED

15 Operation

Status indicator LED The HS includes a status indicator on the front panel to allow you to quickly determine its general status and readiness. The status indicator changes color depending on the current state of the HS.

Green: Indicates that HS is ready for operation.

Yellow: Indicates that the HS is not ready for operation. Power is on and available, but not all parameters have reached operating setpoints. A warning or other message may exist. Check the GC touchscreen for additional information.

Red: Indicates a fault or other serious condition. A fault or other message may exist. Check the GC touchscreen for additional information. The HS cannot be used until the fault condition is resolved.

In addition to the indicator LED, detailed status information appears on the touch screen of the connected GC, and through the GCs browser interface.

Park button and indicator The HS park button also includes an indicator light. When lit, the tray is in the park position, and the HS is not ready. To park or unpark the tray, press the Park button. See Park or Unpark the Tray on page 33.

Operation 16

2 The Operation Workflow Routine Operation Workflow 17

Method Development Workflow 18

This section describes the basic work flow for using the headspace sampler.

2 The Operation Workflow Routine Operation Workflow

17 Operation

Routine Operation Workflow Figure 5 summarizes the normal operating workflow for headspace analysis. This workflow assumes that the headspace sampler is set up and that the methods and samples are known.

Figure 5. Routine headspace analysis workflow

Start Up the Head- space Sampler.

Load Method.

Prepare Samples.

Create Sequence.

Start.

2 The Operation Workflow Method Development Workflow

Operation 18

Method Development Workflow Figure 6 summarizes the workflow for developing methods. For details about method development, see Method Development on page 70.

Figure 6. Workflow for method development

Start Up the Head- space Sampler.

Configure.

Create Method.

Prepare Samples.

Load Samples.

Create Sequence.

Start.

Evaluate.

If Needed, Refine Method.

Re-evaluate.

If needed, consid- er MHE/MHC.

If Needed, Optimize.

2 The Operation Workflow Method Development Workflow

19 Operation

Operation 20

3 Consumables Consumables for Headspace Analysis 21

This section lists commonly-used parts, such as vials and sample loops, needed for routine operation of the Agilent 8697 Headspace Sampler. Procedures for replacing these parts can be found in this manual or in the Maintenance manual.

3 Consumables Consumables for Headspace Analysis

21 Operation

Consumables for Headspace Analysis The following tables list common supplies for the headspace sampler and headspace analysis. For the latest parts available, visit the Agilent website at www.agilent.com/chem.

Table 1 Headspace sampler parts and standards

Description Part number

Leak test kit. Includes: No hole ferrule 11 mm low bleed septa, 5/pk Leak test vial 1/8-in. nylon tube fitting plug 1/16-in. stainless steel ZDV plug (6 port valve cap)

G4556-67010

Transfer line septa (9 mm) 5183-4801

Tray vial rack, 8697 (2 racks) G4511-68940

Tray vial rack labels G4556-90500

Replacement Gas Clean Filter, carrier gas (used for vial pressurization gas)

CP17973

Universal/external split vent trap with 3 cartridges, 1/8-inch Swagelok fitting

RDT-1020

Column cutting wafer, ceramic 5181-8836

Sample probe, deactivated G4556-63825

6-port valve, replacement rotor, WT series, 300 psi, 350 C 1535-4952

Sample loop retainer clip, 1 each: 1 ea. used with 0.025, 0.05, and 0.10 mL sample loops 2 ea. used with 0.5 and 1.0 mL sample loops 1 ea. used with 3.0 mL sample loops

G4556-20177

Sample loop retainer clip, 1 each: 1 ea. used with 0.025, 0.05, and 0.10 mL sample loops

G4556-20178

Inlet Liner for use with HS Transfer Line Accessory

Ultra Inert straight 2.0 mm liner 5190-6168

Standards

GC headspace evaluation standard, 1 x 1 mL 8500-4328

Headspace OQ/PV sample 5182-9733

3 Consumables Consumables for Headspace Analysis

Operation 22

Table 2 Headspace sampler transfer line parts

Description Part number

Transfer line components

Ferrule, polyimide, graphite, 5/pk

0.53 mm, 1/32 in. for tubing OD 0.50 x 0.80 mm 0100-2595

0.4 mm id, for columns up to 250 m od 5190-1437

Septum nut, transfer line, for split/splitless and multimode inlets G3452-60845

Blanking nut, 1/16-inch stainless steel 01080-83202

Nut and reducing union for 6 port valve and transfer line connection, 1/16-inch to 1/32-inch

0100-2594

Transfer lines

Deactivated fused silica, 250 m 5 m 160-2255-5

Deactivated fused silica, 320 m 5 m 160-2325-5

Deactivated fused silica, 450 m 5 m 160-2455-5

Deactivated fused silica, 530 m 5 m 160-2535-5

ProSteel deactivated stainless steel, 5 m length 160-4535-5

Sleeve for ProSteel tubing, 5 m length 4177-0607

Parts for connection to volatiles interface

Ferrule, 0.4 mm VG cond .25 col lng 10/pk 5062-3508

Ferrule, 0.5 mm VG cond .32 col lng 10/pk 5062-3506

Ferrule, 0.8 mm VG cond .53 col lng 10/pk 5062-3538

Table 3 Headspace sampler sample loops

Description Part number

Sample loops, inert

0.025 mL G4556-80101

0.05 mL G4556-80102

0.1 mL G4556-80103

0.5 mL G4556-80105

1.0 mL G4556-80106

1.0 mL, Certified G4556-80126

2.0 mL G4556-80107

3.0 mL G4556-80108

3.0 mL, Certified G4556-80128

5.0 mL G4556-80109

3 Consumables Consumables for Headspace Analysis

23 Operation

Table 4 Headspace vials and caps

Description Part number

Certified flat bottom vials

Certified flat bottom headspace vials, 20 mL, 100/pk 5182-0837

Certified flat bottom headspace vials, 10 mL, 100/pk 5182-0838

20 mm Headspace caps, with septa

Certified headspace Al crimp cap, PTFE/Si septum, 20 mm,100/pk 5183-4477

Headspace vial kits

Vial kit 20 mL Headspace crimp top, flat bottom vials, silver aluminum one-piece crimp caps with safety feature, PTFE/white silicone septa, 100/pk

5182-0840

Cappers and decappers

A-Line electronic crimper for 20mm caps 5191-5615

A-Line electronic decapper for 20mm cap 5191-5613

Ergonomic manual crimper for 20 mm caps 5040-4669

Ergonomic manual decapper for 20 mm caps 5040-4671

Operation 24

4 Sample Vials Sample Vial Types 25

Sample Vial Septa and Caps 26

Vial Labels 27

Filling Sample Vials 29

Cap a Sample Vial 30

Park or Unpark the Tray 33

Install a Vial Rack 34

Load a Sample into the Tray 35

This section discusses sample vial selection, sample preparation, and vial handling with the Agilent 8697 Headspace Sampler.

4 Sample Vials Sample Vial Types

25 Operation

Sample Vial Types The headspace sampler accepts 10-mL, 20-mL, or 22-mL sample vials. Set the vial size in the method. The vial size can change with each new method used in a sequence, but not within a method. Using a different vial size than expected by the method causes a run-time exception.

The headspace sampler uses clear or amber glass sample vials with crimp caps, or screw-cap vials. Use amber glass vials for light-sensitive samples. Both types are available with either flat or rounded bottoms. Refer to your Agilent catalog for consumables and supplies for acceptable vial types, or visit the Agilent website at www.agilent.com/chem. Incompatible sample vials can cause gripper errors.

Vials must conform to the specifications shown in Figure 7.

Figure 7. Supported vial dimensions

Avoid reusing vials. Using vials more than once increases their chance of breaking.

22.40 to 23.10 mm

47.0 mm minimum 79.0 mm maximum

18.0 mm maximum

5.0 mm maximum

4 Sample Vials Sample Vial Septa and Caps

Operation 26

Sample Vial Septa and Caps There are different types of septa used with crimp caps and screw-on caps, each with different resealing characteristics and different resistance to solvents.

Vial caps come with or without an internal safety feature that allows the vial to vent if the internal vial pressure exceeds about 310 kPa (45 psi).

In general, do not use crimp caps or septa more than once for headspace analysis.

Refer also to the Agilent website at www.agilent.com for acceptable vial types.

Septum material Compatible with Incompatible with Resealability Maximum temperature*

PTFE/butyl rubber PTFE resistance until punctured, then septa or liner will have compatibility of rubber (ACN, acetone, DMF, alcohols, diethylamine, DMSO, phenols)

Chlorinated solvents, aromatics, hydrocarbons, carbon disulfide

Good < 125 C

PTFE/silicone rubber PTFE resistance until punctured, then septa will have compatibility of silicone (alcohol, acetone, ether, DMF, DMSO)

ACN, THF, benzene chloroform, pyridine, toluene, hexane, heptane

Average < 180 C

High performance < 300 C

* Approximate. Refer to manufacturers recommendations.

4 Sample Vials Vial Labels

27 Operation

Vial Labels

CAUTION Make sure that any label and ink can withstand the oven heat without degrading.

If using labels, the label needs to conform to the dimensions below. If also using the optional barcode reader (G4527A), the barcode labels must conform to the general dimensions for labels, plus the placement requirements shown.

Figure 8. Vial label and barcode specifications (20 mL vial shown)

CAUTION Correct sample vial dimensions are critical for proper gripper operation. Vials and labels that do not meet these specifications may cause sampler errors. Service calls and repairs found to be due to vials and labels that do not meet these specifications are not covered under warranty or the service contract.

To confirm label placement, place a labeled vial into the barcode reader. Go to Diagnostics > Headspace > Manual Actions > Read Barcode. The barcode reader will attempt to read a barcode from the vial.

In addition, barcode labels must:

Be heat resistant (to avoid degradation or charring when heated)

Use a matte or other non-glossy finish. Glossy barcode labels can reflect ambient room light, and interfere with the reader.

Bar code

Text

Text

15

10

5mL

1 mm skew maximum

23.5 mm maximum, including label

4.0 mm high minimum

No label 17.5 mm minimum

17.0 mm minimum

25 mm maximum

4 Sample Vials Supported barcodes

Operation 28

Supported barcodes The barcode reader can read any of the following symbologies:

Code 3 of 9

Code 128

Matrix 2 of 5

Standard 2 of 5

Interleaved 2 of 5

UPC-A

EAN/JAN 13

EAN/JAN 8

UPC-E

4 Sample Vials Filling Sample Vials

29 Operation

Filling Sample Vials In general, fill sample vials about half way. Although sample amounts can vary depending on the analysis, do not fill vials more than the amount shown in Figure 9. Filling the vial correctly ensures that the sampling probe will not contact the matrix during sampling. If you need more sample, use a larger vial or optimize the method to improve results. See Method Development on page 70 for more information.

Figure 9. Vial fill limits

17 mm

75% of height maximum

50% of height typical

20-mL and 22-mL vials 10-mL vials

50% of height maximum

4 Sample Vials Cap a Sample Vial

Operation 30

Cap a Sample Vial The vial must be sealed properly to ensure that the headspace gases do not escape prematurely. For crimp top vials, use a crimper designed for headspace vials with 20-mm caps to seal the vials. Screw caps and screw top vials are also available. See Consumables for Headspace Analysis on page 21.

Cap a sample vial using a manual crimper 1 Before beginning, clean the inside surfaces of the crimper jaws.

2 If using separate septa and caps, place a septum in a vial cap with the PTFE side facing the vial. Take care not to contaminate the septum.

3 Place the cap upside down on a table.

4 Place the sample in the vial. (Most vials should not be more than 50% full, but some vials can reach 75% full. See Filling Sample Vials.)

5 Place the septum and cap assembly over the vial opening.

6 Lift the vial into the crimper.

7 With slow and steady pressure, squeeze the crimper handles to seal the vial. (Squeeze the handle until it reaches the adjustment screw.)

4 Sample Vials Cap a sample vial using a manual crimper

31 Operation

Figure 10 shows proper and improper vial caps.

Figure 10. Acceptable and unacceptable vial caps

Check each vial for proper crimping:

Be sure there are no folds or wrinkles on the part of the cap that wraps under the neck of the vial. To remove folds or wrinkles, turn the vial about 10 and crimp it again. Adjust the crimper for a looser crimp by turning the adjusting screw clockwise.

The cap should be finger-tight. If the cap is loose, adjust the crimper for a tighter crimp by turning the adjusting screw counterclockwise. Crimp the cap again. If the cap is too tight, the septum will distort and the vial may leak.

Be sure that each cap has a flat septum centered over the top of the vial.

Centered

No folds or wrinkles

Acceptable Unacceptable

Off-center

Folds and wrinkles

Too loose Cap turns easily Little or no cap

deformation Will leak

Optimal Cap does not turn easily

Some cap deformation

No leaks

Slightly overtight Cap cannot turn Cap deformed in

middle Septum may be

distorted May not leak but not

optimal

Overtightened Cap cannot turn Cap deformed in

middle and sides are crushed

Septum may extrude or buckle

May not leak but not optimal

4 Sample Vials Verify proper crimping

Operation 32

If the septum is not flat, remove the cap, turn the crimper adjusting screw clockwise, and try again.

If the cap is not centered, remove the cap and make sure the new cap is flat on the top of the vial before you squeeze the crimper.

Note that overcrimping puts additional stress on both the cap and the vial.

Verify proper crimping The best way to determine if the crimp tool is adjusted properly, and that the vials are properly capped, is to use the instruments built-in test.

1 First, create a capped vial as described in Cap a sample vial using a manual crimper. Inspect it to be sure it looks acceptable. The vial should look like the optimal vial in Figure 10. If not, adjust the crimper and create more test vials it until you have a vial that looks optimal.

2 Make 4 more vials, for a total of 5 which appear to be acceptable.

3 On the GC touchscreen or in the browser interface, go to Diagnostics > Diagnostic Tests, then select User Vial Leak Test from the Headspace category.

4 Start the test.

5 Follow the prompts to load the vials and run the test. If the vials pass, then record the setting used for the vials, and use this setting for making sample vials. If the vials fail the leak test, then adjust the crimper, make more test vials, and repeat the test.

If you change capping tools or experience leaks with a new batch of vials, septa, or caps, re-run this test.

4 Sample Vials Park or Unpark the Tray

33 Operation

Park or Unpark the Tray Parking the tray moves the tray gantry to a safe position. When parked, you can load vials into the racks, or install and remove racks from the HS.

Press the park button to park the tray. The park button lights to indicate that the tray is parked.

Press the park button again to unpark the tray and ready it for use.

Figure 11. Park button location

You cannot start a sequence if the tray is parked.

Parking the tray during a sequence pauses the sequence. Current vials continue to process, but no new vials are started, and no vials leave the oven.

8897 Headspace Sampler

Park button

l r

4 Sample Vials Install a Vial Rack

Operation 34

Install a Vial Rack 1 Press the tray park button to park the tray (move the gantry to a rest position for easy

access to the vial rack area). See Figure 11 on page 33.

CAUTION When loading a tray rack with sample vials, avoid excessive tray motion. If the sample coats the septum or coats the vial more than typical, this may change results.

2 While holding up the front end of the rack, slide the rack back and under the mounting clip on the HS top. Then, lower the front of the rack in place.

When installed correctly, a white LED on the front of the tray rack lights.

3 Press the tray park button to prepare the tray for use.

4 Sample Vials Load a Sample into the Tray

35 Operation

Load a Sample into the Tray 1 Press the park button to park the tray (move the gantry to a rest position for easy access

to the vial racks).

2 Place the capped sample vials into the tray as desired. See Figure 12.

Figure 12. Tray vial positions

3 Press the park button to prepare the tray for use.

Vial racks

Operation 36

5 HS Method Parameters HS Method Parameters 37

Method Parameter Summary 40

Determine the GC Cycle Time 42

This chapter describes the method settings available for the HS. Make all method settings using the GC touch screen, browser interface, or in the data system. To learn about HS method development, see Method Development on page 70.

5 HS Method Parameters HS Method Parameters

37 Operation

HS Method Parameters The 8697 HS adds its method settings and parameters into the method for the GC. Access them like any other GC method setting, using the GC touchscreen, browser interface, or data system.

The HS adds:

Temperatures for the vial, sample loop, and transfer line

Times for equilibration and injection, plus the GC cycle time (used for sample overlap and throughput calculations)

Vial settings for vial size, filling, shaking, and venting after the injection

Most HS method parameters are accessed through the Methods tab on the GC touchscreen or in the browser interface. A few settings are located in different places, however, between the touchscreen and the browser interface. Settings for gas types, the transfer line dimensions, standby vial flow, and barcode symbologies are found under Settings for the touchscreen, but are found in Method > Configuration for the browser interface.

See also Settings > Configuration > Headspace on page 55. Note that while you set the barcode type in the method or as a configuration setting, the decisions on whether to use barcodes and how to handle barcode problems are made only through a data system. The browser interface does not support barcodes in sequences.

Local user interface

Figure 13. Headspace method parameters shown in the GC local user interface

5 HS Method Parameters Local user interface

Operation 38

Settings for transfer line type, sample loop volume, gas type, and similar infrequently changed settings can be found on the touchscreen at Settings > Configuration > Headspace.

Figure 14. Headspace method parameters shown in the GC local user interface (8890 GC)

5 HS Method Parameters Browser interface

39 Operation

Browser interface

Figure 15. Headspace method parameters shown in the browser interface (8890 GC)

When using the browser interface, note that the method also includes the settings for headspace configuration, such as vial pressurization gas type.

Figure 16. Headspace method configuration parameters shown in the browser interface (8890 GC)

5 HS Method Parameters Method Parameter Summary

Operation 40

Method Parameter Summary This section lists method parameters, along with a brief description of each one. For detailed descriptions of the fill modes, see Method Development on page 70.

Table 5 Common method parameters

Path Parameter Description

Method

Temperatures Oven Oven temperature for vial equilibration.

Loop Temperature of the sample loop and valve.

Transfer Line Temperature of the transfer line (isothermal).

Times Vial Equilibration Time for the vial to equilibrate in the oven.

Injection Duration Amount of time to sweep the sample loop vapors into the GC inlet.

GC Cycle Time for the GC to complete its run, including the time to cool down and become ready at the end of the run.

Vial and Loop Vial Size (mL) Select the sample vial size for all vials using this method.

Shake Value Set the level of shaking for the sample during equilibration in the oven. Higher values provide more vigorous shaking. The browser interface will also list the frequency and acceleration associated with the selected shaking level.

Vial Fill Mode Vial Fill Mode Select how to pressurize the vial. See also Pressurizing the vial on page 84.

Pressure Pressure Equilibration Time Time to allow for the pressure in the vial to stabilize after initial vial pressurization.

Fill Pressure Target sample vial final pressure.

Flow to Pressure Pressure Equilibration Time Time to allow for the pressure in the vial to stabilize after initial vial pressurization.

Fill Pressure Target sample vial final pressure.

Fill Flow Flow rate used to pressurize the vial. Default: 50 mL/min.

Constant Volume Pressure Equilibration Time Time to allow for the pressure in the vial to stabilize after initial vial pressurization.

Fill volume, mL Specific volume of gas with which to pressurize the vial.

Loop Fill Mode

Loop Ramp Rate How quickly to fill the sample loop.

Final Loop Pressure Final target pressure for the filled sample loop.

Loop Equilibration Time set for the sample loop to stabilize after pressurization.

5 HS Method Parameters Method Parameter Summary

41 Operation

Extraction Mode Extraction mode Set the type of extraction for the method, Single, Multiple, or Concentrated. See also Extraction mode on page 87.

Number of extractions Concentrated Extractions Mode only: Enter the number of extractions to concentrate before starting a GC run.

Venting and Purging

Vent vial pressure after the last extraction

After the last extraction, and while the sample transfers to the GC, vent residual vial pressure to atmosphere. (Multiple or Concentrated extractions only.)

Vent vial pressure between extractions

Vent vial between concentrating extractions. (Multiple or Concentrated extractions only.)

Purge Flow Mode

Purge Flow Purge sample probe and loop with vial pressurization gas after removing the vial from the probe.

Purge Time Length of time to purge the sample probe and loop.

Miscellaneous

Dynamic Leak Checking Leak Test Mode Turn On to check the sample vial for leaks after the vial pressurization. The time spent on the dynamic leak test is equal to the Pressure Equilibration Time + .02 minutes.

Acceptable Leak Rate The leak rate considered acceptable for the application. Default is 0.5 mL/min.

Sequence Actions Set how the HS should handle unexpected sequence issues, such as a missing vial or vial size mismatch.

Vial Missing The HS could not find the sample vial in the expected location.

Wrong Vial Size The HS determined that the vial being handled by the tray is not the size specified in the method. This could indicate the wrong sample is being processed, or that the wrong method was specified in the sequence.

Leak Detected The sample vial failed the dynamic leak check.

System Not Ready The HS has processed the sample, made the extraction, and is ready to transfer the sample to the GC inlet, but the GC is not ready to start a run.

Method development Access parameters to use when developing methods See Using parameter increment on page 82.

Method > Configuration > Headspace (Browser Interface). See Settings > Configuration > Headspace on page 55.

Table 5 Common method parameters (continued)

Path Parameter Description

5 HS Method Parameters Determine the GC Cycle Time

Operation 42

Determine the GC Cycle Time The GC cycle time is the time needed for the GC to perform the run, then return to a state ready for the next injection. The GC cycle time is the GC run time plus any additional time needed for any post-run program, plus any time needed for GC components to cool and return to their starting conditions, plus any other time needed for the GC and system to return to a ready state.

The HS uses the GC cycle time to calculate throughput and timing. An accurate GC cycle time is crucial to optimizing throughput and for correctly processing samples.

If the GC cycle time is too long, this can cause:

Lowered throughput. Vials wait longer than needed before processing.

If the GC cycle time is too short, this can cause:

Sequence faults. Vials may be processed too early and may sit too long while waiting for the GC to become Ready.

It is better to enter a longer time than needed than to enter too short a time and possibly reduce sample quality.

Determine the GC cycle time To determine the GC cycle time:

1 Perform a sequence of five runs that use the HS method and empty vials (capped and sealed but containing nothing). At first, estimate the GC cycle time as the GC oven program time, plus any other known post-run time, plus 10 minutes. This value should be too long.

2 Set the sequence action for System Not Ready to Skip or to Abort.

3 Run the sequence.

4 After the sequence completes, examine the data system logs. Look in the Activity Log (for OpenLab CDS) or in the Sequence Log (for OpenLab CDS Chemstation Edition) or in the Logbook (for MassHunter) to find the calculated cycle time. There will be 4 cycle times reported. If using the browser interface, examine the sequence log.

5 A good GC cycle time is the average of the cycle times, plus 0.2 to 0.5 minutes.

You can also estimate the GC cycle time without making a run. By adding the GC oven program duration and the duration of any post-run programs, you can get close to the true cycle time. However, temperature programming and cryogenic operation can make estimation more difficult. Add extra time to account for zone cool down (for example, oven or inlet cool down).

When using an MS, also include any extra time required for any other factors that might impact readiness.

Also consider time for data processing. While in most cases data processing is not a problem, a very busy data system may need extra time between samples.

5 HS Method Parameters Validate the GC cycle time

43 Operation

Validate the GC cycle time Rerun the sequence of three or four blank vials. There should now be no added wait time between consecutive vials. The HS should be able to start an injection when it is ready, without waiting for the GC to become ready.

Operation 44

6 HS Sequences What Is a HS Sequence? 45

Sequences, Extraction Modes, and Vial Punctures 46

Sequences and Throughput 47

Priority Samples 48

Method Sequence Actions 49

Browser Interface and Data System Sequence Actions 51

Stop, Abort, or Pause a Running Sequence 52

Vial Status 53

Sequences of samples are created and run using the GCs browser interface or an Agilent data system. This chapter describes the special considerations for headspace sequences when using those systems to run samples, and it also describes the sequence-related features provided by the 8697 HS that help optimize throughput.

For information about using the browser interface or data system to create sequences and run samples, please refer to their online help systems.

6 HS Sequences What Is a HS Sequence?

45 Operation

What Is a HS Sequence? A sequence for the 8697 Headspace Sampler is an ordered series of sample vials to prepare and inject, including the method needed to prepare each vial.

All sample processing occurs in a sequence. To run a sample, there must be a sequence defined.

A sequence can skip vial locations.

A sequence can run a vial more than once.

A sequence does not require any particular vial order. Running vials 1, 23, 5, 2, 3, and 40 is valid.

6 HS Sequences Sequences, Extraction Modes, and Vial Punctures

Operation 46

Sequences, Extraction Modes, and Vial Punctures In the sequence you can specify the same vial in as many entry lines as desired. How the HS sampler processes the vial depends on the method Extraction mode and the sequence:

Extraction Mode is Single.

If a vial appears more than once in a sequence, or if the number of injections is greater than one, the vial is completely reprocessed for each entry or injection.

Extraction Mode is Multiple.

If the number of injections per vial is greater than one, the HS will puncture the vial once, then make the extractions and injections. The HS will not perform multiple vial punctures and will not perform multiple equilibrations.

When more than one consecutive entry exists for a vial, and the entries use the same method, the HS will puncture the vial once, then make the extractions and injections. The HS will not perform multiple vial punctures.

Extraction mode is Concentrated.

When more than one consecutive entry exists for a vial in a sequence, or if the number of injections is greater than one, the HS performs only one equilibration and one vial puncture.

See also Sequences and Throughput.

6 HS Sequences Sequences and Throughput

47 Operation

Sequences and Throughput The HS optimizes throughput by checking the methods for the vials specified in the current sequence. When consecutive vials share the same method, the HS will examine the timing parameters for the samples, then calculate the best times to place each vial into the oven. This approach maximizes the number of vials equilibrating at a time.

Vials using different methods will not be handled until the preceding samples leave the oven.

For more information, see Optimizing Throughput on page 88.

6 HS Sequences Priority Samples

Operation 48

Priority Samples A priority sample is a vial that you want to run as soon as possible, before some of the other vials in the currently-running sequence.

The browser interface and Agilent data system each provide a way to pause and then edit a running sequence to insert a new sample into it. Place the new sample into any unused tray location. Then, pause and edit the sequence to include the new vial. Refer to the browser interface and data system helps for instructions on editing a running sequence.

Note any samples that have begun processing cannot be edited. The HS will continue to process all vials that it already started before it will start processing a new vial. If the new sample uses the same method, it may be placed into the oven concurrently with the other samples are being processed. If it uses different method conditions it might not start until all prior samples have been moved from the oven.

6 HS Sequences Method Sequence Actions

49 Operation

Method Sequence Actions When the HS encounters certain problems during a sequence, it has the ability to skip a vial, continue anyway, pause the sequence, abort everything, or wait until the system becomes ready. The settings to control HS behaviors during sequence execution are called sequence actions. These sequence actions are part of the method, and therefore can change from sample to sample during sequence execution. Use sequence actions to specify what the HS should do when it encounters issues such as a vial size mismatch, missing vial, and similar issues. Sequence Actions provide the flexibility to handle relatively minor issues with the level of attention appropriate for your workflow. You can completely halt sequence processing for some issues, while permitting the sequence to continue for other issues. The GC always logs the issue and the action taken.

Types of sequence issues handled Sequence Actions provides logical sequence control for the issues listed below. The possible actions are described in Available actions.

Vial Missing: Control the HS behavior whenever it cannot find a sample vial, for example, if the HS cannot find a vial in the tray. A misplaced vial, a hardware problem, or a problem in the sequence, for example, can cause a missing vial issue.

Wrong Vial Size: Control the HS behavior when the HS finds a sample vial, but the size of the vial does not match the size of the vial as defined in the method. A size mismatch can change the analysis results or indicate a misplaced vial, for example. To determine vial size, the HS measures the vial height when the vial is in the gripper. (This means that the HS cannot distinguish between 20 mL and 22 mL vials.)

Leak Detected: Control the HS behavior if the sample vial fails the dynamic leak test. (Only meaningful when dynamic leak checking is enabled.)

System Not Ready: Control the HS behavior when the HS is ready to begin filling the sample loop but the GC is not ready to start a run. When the HS becomes Ready, it checks if the GC is Ready. If the GC is ready, the HS begins filling the sample loop for the injection cycle. If the GC is not ready, the HS follows the specified action. A GC not ready, could indicate a low GC cycle time parameter in the method, normal variances in GC timing, or a GC problem. Note that some data systems may not collect data if the GC is not Ready before the run starts. (In this case, do not use Continue as the sequence action.)

Available actions The actions available for each issue depend on the nature of the sequence issue. (For example, you cannot continue to process a missing vial, but you can skip the vial or abort the sequence.)

Continue: Continue processing the current sample vial and the sequence.

Skip: Skip the current sample vial, then continue processing with the next sample vial in the sequence. The current sample vial is immediately returned to the tray, if appropriate. The system skips all injections for that vial.

6 HS Sequences When using an MS

Operation 50

Pause: Pause the sequence. Any vials in the oven will continue to be processed, including the current vial, if applicable. No other vials will be moved into the vial oven.

To recover from a pause: Place missing vial or correct size vial on the shutter. Remove

incorrect vial from the tray, if present. Touch on the GC touchscreen.

Abort: Abort the sequence. The HS stops all vial processing, for the current sample vial and all other sample vials. The HS returns all sample vials to the tray, beginning with the sample vial which had the problem. To recover, check the logs to determine which sample vial had the problem. Resolve the problem, then create a new sequence and restart.

Wait for Ready: The HS waits until the GC becomes ready. This setting can increase vial equilibration times for vials in the oven. The HS reports the actual equilibration times in its logs. Note that once the HS begins to fill the sample loop, the HS will start an injection whether or not the GC is ready. Also, if something prevents the GC from becoming ready, the HS waits.

NOTE Abort stops only the HS. The GC and data system may complete processing for any previously-injected sample.

Note that sequence actions do not override other potential problems, such as a hardware fault, that can interrupt a sequence.

When using an MS If using an MS, select either Abort, Skip, or Wait for Ready for the System Not Ready sequence action. The MS data system will not acquire data unless the entire system is ready when the start command occurs. Using Continue can cause lost data. You must include any extra time required for MS solvent delay and other factors in the GC Cycle time parameter.

6 HS Sequences Browser Interface and Data System Sequence Actions

51 Operation

Browser Interface and Data System Sequence Actions

The browser interface and Agilent data systems can provide additional features that can be used to handle unexpected events. These features appear as part of the sequence settings, and vary depending on the data system. For example, the browser interface and many data system provide a setting for handling missing vials in the sequence. In the event of a conflict between the sequence setting and a setting in the HS method, the HS will use the value set in the HS method for the specific issues listed in Types of sequence issues handled on page 49.

The data systems may also provide ways to handle barcode reader errors. Refer to the data systems help for more information.

6 HS Sequences Stop, Abort, or Pause a Running Sequence

Operation 52

Stop, Abort, or Pause a Running Sequence You can interact with a running sequence from either the GC touchscreen stop button or the computer that is running the sequence via the browser interface or a data system.

On the GC touchscreen, press stop ( ). The GC display prompts to stop the run, stop the sequence, or cancel (do nothing).

Stop the run: Immediately end the current run and move on to the next run in the sequence. The remainder of the sequence finishes normally.

Stop the sequence: Immediately end the current run and abort the sequence. All vials in the oven are returned to the tray through the cooling station and the system returns to an idle state.

The browser interface and a data system provide three options for interacting with a running sequence:

Pause sequence: The HS finishes any samples that have already begun processing, but then waits for further instructions. No new vials will enter the oven. When resumed, the sequence finishes normally.

Using pause allows the sequence to be edited. During editing, the list of samples that have not yet begun processing can be changed as needed to insert a new sample or to make any other changes. Upon resume, the HS begins processing at whatever is now the next sample in the sequence.

Stop the run: Immediately end the current run and move on to the next run in the sequence. The remainder of the sequence finishes normally.

Stop the sequence: Immediately end the current run and abort the sequence. All vials in the oven are returned to the tray through the cooling station and the system returns to an idle state.

Refer to the help for the GC browser interface and the data system for more details on their sequence features.

6 HS Sequences Vial Status

53 Operation

Vial Status Use the GC touchscreen or browser interface status tray to show current status information for the a running sequence. The GC will display:

Oven temperature

Loop temperature

Transfer line temperature

Vial flow

Vial pressure

External carrier pressure

Vial status. This includes real time monitoring of vial state: equilibrating, pressurizing, extracting, injecting, returning to tray.

Operation 54

7 Settings Headspace Settings 55

Settings > Configuration > Headspace 55

Settings > Calibration > Headspace 56

Settings > Service Mode > Headspace 58

Settings > Scheduler: Resource Conservation 59

This section describes the settings and features available from the GC under Settings.

7 Settings Headspace Settings

55 Operation

Headspace Settings The HS settings available from the Settings tab apply generally, regardless of the current method. If you make hardware changes, always check these settings and update as needed, for example, after changing the vial pressurization gas type, the transfer line, or the sample loop.

Settings > Configuration > Headspace The table below lists the HS configuration settings.

The barcode reader can read barcodes of the following types (symbologies):

3 of 9

Code 128

Matrix 2 of 5

Standard 2 of 5

Interleaved 2 of 5

UPC A

EAN/JAN 13

EAN/JAN 8

UPC E

Setting Description

Inlet Select the inlet connected to the transfer line. (Setting available for GCs with more than one inlet.)

Gas Type Vial pressurization gas type.

Loop Volume Internal volume of the installed sample loop.

Transfer Line Type Select the type of transfer line installed, fused silica or DB-ProSteel.

Transfer Line Diameter Internal diameter of the transfer line (um).

Standby Vial Flow Normally leave enabled. The standby Vial Flow purges the sample loop and sample probe between extractions and during idle time. I using the GC resource conservation features, this flow can be reduced to conserve vial pressurization gas. Default: 20 mL/min.

Clear Oven at Startup When enabled, when first turned on the HS will check the vial oven for vials and return all vials found to the tray.

Enable barcode checksum Available if a barcode reader is present. Certain barcodes can include a checksum value for use in validating whether the barcode is read correctly. Enable this setting when the barcode includes a checksum.

Symbology Available if a barcode reader is present. Select All to let the barcode reader check all available symbologies, or select the specific symbology used on the vial labels. See the full list of supported symbologies below.

7 Settings Settings > Calibration > Headspace

Operation 56

Settings > Calibration > Headspace The HS provides a calibration routine for the tray to ensure optimal handling of vials, and a calibration for the gas flow and pressure sensors.

Calibrate the tray and grippers

The tray may require periodic calibration to maintain optimum performance. This calibration ensures the gripper and gantry motions continue to move samples smoothly, without dropped vials. Calibrate the tray after HS installation, after replacing the gripper pads, or when recommended during automated troubleshooting.

1 Before beginning, empty the vial oven and tray of any vials.

2 Verify that the movable calibration post and the leak text vial are located in their dedicated locations.

3 Go to Settings > Calibration > Headspace and select Start Calibration on the tray calibration settings page.

4 Follow the instructions.

To reset the tray to its factory calibration, Go to Settings > Calibration > Headspace and under the Tray section select Start Factory Calibration.

Calibrate the grippers

The grippers will automatically be calibrated periodically by the HS. The gripper calibration requires the leak test vial and the movable calibration post.

Leak test vial

Movable calibration post

7 Settings Settings > Calibration > Headspace

57 Operation

Calibrate the vial pressurization EPC

The EPC gas control modules contain flow and/or pressure sensors that are calibrated at the factory. Sensitivity (slope of the curve) is quite stable, but zero offset requires periodic updating.

Change the calibration settings or manually calibrate the vial pressurization gas EPC sensors from the GC touchscreen or browser interface:

1 Select Settings > Calibration > Headspace and scroll down to the EPC calibration settings.

2 Select On next to the desired sensor to zero it.

3 For the flow sensor: Verify that the gas is connected and flowing (turned on).

4 For the pressure sensor: Disconnect the gas supply line at the back of the HS. Turning it off is not adequate; the valve may leak a little bit.

5 Reconnect any gas line disconnected in the previous step and restore operating flows.

To reset an EPC sensor to its factory calibration, Go to Settings > Calibration > Headspace and under the EPC section select Reset for that sensor.

Calibrate the aux pressure sensor

The EPC gas control modules contain flow and/or pressure sensors that are calibrated at the factory. Sensitivity (slope of the curve) is quite stable, but zero offset requires periodic updating.

Change the calibration settings or manually calibrate the aux pressure sensor from the GC touchscreen or browser interface:

1 Select Settings > Calibration > Headspace and scroll down to the EPC calibration settings.

2 Select On next to the desired sensor to zero it.

3 For the aux pressure sensor: Disconnect the gas supply line at the back of the HS. Turning it off is not adequate; the valve may leak a little bit.

4 Reconnect any gas line disconnected in the previous step and restore operating flows.

To reset this EPC sensor to its factory calibration, Go to Settings > Calibration > Headspace and under the EPC section select Reset for that sensor.

Leak Rate Calibration Procedure

Though extremely rare, the expansion of some solvents being heated to temperatures above their boiling point can create a dynamic pressure change that is difficult to accurately quantify on the time scale of the typical HS dynamic leak test. Rather than compromising sample throughput by elongating the pressure equilibration time method parameter, the preferred way to account for the solvent expansion is to calibrate the reported leak rate associated with a given set of conditions.

If a minimum of three vials have been analyzed and report a consistent dynamic leak test leak rate, perform the Leak Rate Calibration Procedure below.

7 Settings Settings > Service Mode > Headspace

Operation 58

1 Verify that your system is leak free.

Go to Diagnostics > Diagnostic Tests and select the Leak and Restriction Test. Run the test using the leak test vial (part number G4511-20180) and an Agilent advanced green septum (part number 5183-4759). Make sure that your instrument temperatures are the same as the analytical method setpoints.

The procedure begins with the system leak test to ensure that no leaks are detected when the system is void of solvent.

2 Calibrate the leak rate. a If the Leak and Restriction test passes, use your desired analytical method to analyze

six vials containing the solvent used during analytical runs. b Record the leak rate for each of the six vials, then calculate their average and standard

deviation. Set the pass/fail leak rate entered into the HS method for the analysis in question at the average leak rate plus three times the standard deviation.

Table 6 displays an example where you should change the analytical methods method leak rate limit to 1.840 mL/min.

Settings > Service Mode > Headspace The headspace service mode lists current, actual values for various configuration, thermal, pneumatic, electronic, and other settings and sensors.

It is also possible to perform a Factory Reset. Normally, do not perform a factory reset unless absolutely necessary. A factory reset erases all custom settings stored in the HS, from flow calibrations to the instrument serial number.

A factory reset will:.

Clear the maintenance and event logs.

Clear the firmware update history.

Table 6 Example of calculating the method leak rate limit

Vial Leak rate (mL/min)

1 1.403

2 1.352

3 1.621

4 1.458

5 1.541

6 1.623

Average 1.500

Std dev 0.114

3 * Std dev 0.341

Avg + (3 * Std dev) 1.840

7 Settings Settings > Scheduler: Resource Conservation

59 Operation

Clear the current HS configuration and calibrations.

Clear EMF tracking data and settings.

Log the factory reset.

Reboot the HS.

Settings > Scheduler: Resource Conservation The HS uses the GCs resource conservation features, and the GC features for Sleep and Wake methods are extended to include HS method parameters. Because the HS adds many new parameters to the method, some of these can be used to conserve gases and power. Most HS settings, however, are not relevant to sleep methods because they are only used while preparing samples. Consider the following HS parameters when setting a sleep method:

Standby Vial Flow: Reduce if desired. Agilent does not recommend turning this flow off, since this flow protects the sample loop and sample probe from atmospheric contamination.

Oven, sample loop, and vial oven temperatures can be reduced during periods of inactivity.

Operation 60

8 How the 8697 Headspace Sampler Works How the HS Processes a Sample Vial 61

How the HS Equilibrates a Vial 62

How the HS Pressurizes a Vial 63

How the HS Fills the Sample Loop (Extracts a Sample) 65

Types of HS Extractions and Injections 66

How the HS Reduces Carryover 69

This chapter provides more advanced theory behind the 8697 headspace sampler. This information is intended for use by method developers.

8 How the 8697 Headspace Sampler Works How the HS Processes a Sample Vial

61 Operation

How the HS Processes a Sample Vial Figure 17 shows the workflow for a vial processed by the HS.

Figure 17. 8697 HS vial process flow

Prepare sample.

Cap sample in vial.

Place vial in tray.

Lift vial and move to shutter.

Equilibrate (tempera- ture and shaking)

Lift vial onto sample probe.

Pressurize vial.

Perform dynamic leak test.

Remove vial from probe.

Lower vial into carousel.

User tasks

Open shutter, lower vial into oven, close

shutter.

Move vial to cooling station.

Return vial to tray.

Return vial to shutter.

Perform extractions and injections: If Single: -Fill sample loop. -Start run, vent vial (optional)

If Concentrated: -Fill sample loop, inject, repeat (pressurize, test, fill loop, inject). -Start run, vent vial (optional)

If Multiple extractions: -Fill sample loop. -Start run, vent vial (optional) -Repeat.

8 How the 8697 Headspace Sampler Works How the HS Equilibrates a Vial

Operation 62

How the HS Equilibrates a Vial The 8697 HS with tray has a vial oven that can equilibrate up to 12 vials at temperatures up to 300 C. In addition, the oven can shake the vials at 9 different acceleration levels. As long as sequence vials share the same method, the HS determines when consecutive samples can be loaded into the oven to increase throughput, then automatically loads them. The HS optimizes for throughput regardless of extraction mode, loop fill mode, and so forth.

8 How the 8697 Headspace Sampler Works How the HS Pressurizes a Vial

63 Operation

How the HS Pressurizes a Vial The HS provides several techniques for pressurizing the sample vial. In addition to simply heating the vial, which may generate enough internal pressure on its own, the HS can provide additional gas to help with extraction. This gas comes from the Vial Pressure fitting on the HS back panel, and can be different from the carrier gas used to move the sample onto the column. While the default vial pressurization method is often sufficient, the alternative techniques may be useful in some applications. See Figure 18 below.

Figure 18. Pressurizing the vial

Flow to pressure This is the default vial fill mode. In this mode, the HS maintains a specified flow rate of carrier gas into the vial until the pressure inside the vial reaches the fill pressure setpoint. The HS maintains this pressure for the hold time. At the end of the hold time, the sample loop fill begins.

Pressure In this mode, the HS fills the vial as rapidly as possible to the target fill pressure setpoint, then maintains this pressure for the specified hold time. At the end of the hold time, the sample loop fill begins.

Constant Volume In this mode, the HS pressurizes the sample vial with a specified volume of carrier gas, then maintains the resultant pressure for the specified hold time. This mode is useful if you need to calculate the exact molar amounts of sample and carrier gas in the vial or sample loop.

1

2

3 4

5

6

6 port valveTransfer line

Sample loop

Sample probe

Carrier gas Vial pressurization

gas

8 How the 8697 Headspace Sampler Works Dynamic leak check

Operation 64

Dynamic leak check By default, the HS performs a leak check after the vial pressurization. While on the probe, the HS can determine if the vial is leaking. If the HS must continually add gas to maintain the desired pressure in the vial, then the vial is leaking. The HS logs the leak test results, and provides a sequence action to allow you to handle (for example, skip or abort) a leaking sample vial.

The time spent on dynamic leak test is equal to Pressure Equilibration Time + .02 minutes.

8 How the 8697 Headspace Sampler Works How the HS Fills the Sample Loop (Extracts a Sample)

65 Operation

How the HS Fills the Sample Loop (Extracts a Sample)

After the vial is pressurized and has stabilized, the HS will perform the specified extractions. The six port valve switches, allowing the pressurized sample to vent through the sample loop. After the specified conditions are met, the loop is considered filled. See Figure 19 below.

Figure 19. Filling the sample loop

The HS provides two modes for filling the sample loop, Default and Custom.

Default loop fill mode In this case, the HS depressurizes the sample vial into the sample loop at a specified rate until the sample vial pressure drops a known amount. The HS calculates the final loop pressure and equilibration time based on current HS configuration and method data.

Custom loop fill mode In this case, you can specify the loop fill rate, final loop pressure, and equilibration time.

1

2

3 4

5

6

Sample probe

Carrier gas Vent

Transfer line

8 How the 8697 Headspace Sampler Works Types of HS Extractions and Injections

Operation 66

Types of HS Extractions and Injections The 8697 HS can extract and inject sample once or multiple times per vial. The HS provides a selection for extraction type as an advanced function. Figure 20 shows the basic flow paths during an injection cycle, where the sample loop is flushed into the GC.

Figure 20. HS injection cycle

Note that the vial pressurization gas flow is always controlled by the HS. The carrier gas flow is always controlled by the GC inlet EPC module.

1

2

3 4

5

6

Sample probe

Carrier gas Vent

Transfer line

8 How the 8697 Headspace Sampler Works Standard extraction

67 Operation

Refer to Figure 21 for a diagram of the flow paths within the HS sampler.

Figure 21. HS sampler flows

Standard extraction In this mode, the HS performs one extraction and one injection per vial puncture. After the vial equilibrates, the HS checks system readiness. If the system is ready, or if the readiness sequence action is continue, the HS punctures the vial. The HS pressurizes the vial and extracts the sample from it according to the method parameters. See Figure 18 and Figure 19. After any sample loop equilibration, the HS six port valve switches to the inject position, the HS injects the sample, and the HS sends a Start command to the GC. At the same time, the HS

SV1

PV1

PV2

PS

PS

FS

Flow control module

1

2

3 4

5

6

Six port valve

Transfer line

Vent Carrier gas

Vial pressurization gas

Sample loop

PS - Pressure sensor FS - Flow sensor SV - Switching valve PV - Proportional valve

8 How the 8697 Headspace Sampler Works Multiple headspace extractions

Operation 68

vents residual pressure from the vial (optional). After the inject time elapses, the six port valve returns to its original position. The sample vial is removed from the probe and returned to the carousel or tray.

Multiple headspace extractions In this mode, the HS performs multiple extractions and injections using one vial puncture. See Figure 19 and Figure 20. After the vial equilibrates, the HS checks system readiness. If the system is ready, or if the readiness sequence action is continue, the HS punctures the vial. The HS pressurizes the vial and extracts the sample from it according to the method parameters. The sample loop vent closes. The vial remains on the probe. After any sample loop equilibration, the HS six port valve switches to the inject position, the HS injects the sample, and the HS sends a Start command to the GC. At the same time, the HS vents residual pressure from the vial (optional). After the inject time elapses, the six port valve returns to its original position. The vial remains on the probe. When the GC Cycle time elapses, the HS again checks the readiness of the system. If the system is ready, or if the readiness sequence action is continue, the HS performs the next pressurization, extraction, injection, and start run. The process repeats until all extractions and injections have been performed.

After the final extraction and injection, the sample vial is removed from the probe and returned to the carousel or tray.

Concentrated headspace extractions Use this mode to concentrate sample in the GC. Typically this mode requires a sample concentrating trap of some kind. (The trap could be an optional external device or an inlet such as the Agilent Multimode inlet.) See Figure 20 and Figure 21.

After the vial equilibrates, the HS checks system readiness. If the system is ready, or if the readiness sequence action is continue, the HS punctures the vial. The HS pressurizes the vial and extracts the sample from it according to the method parameters. The vial remains on the probe. After any sample loop equilibration, the HS six port valve switches to the inject position, and the HS injects the sample into the GC. The HS does not send a Start command to the GC. After the inject time elapses, the six port valve returns to its original position. The vial remains on the probe. The vial can be vented (while the injection occurs) or remain pressurized. The HS repeats the pressurization, extraction, injection, and optional vial venting for each of the extractions specified in the method. During the final concentrating injection, the HS sends the start signal to the GC. The HS vents the vial (optional), removes it from the probe, and returns it to the tray or carousel.

Venting residual vial pressure Regardless of the type of extraction performed, the HS can vent residual pressure from the used sample vial out of the Vent port on the HS back panel. This venting prevents a pressurized vial with potentially noxious contents from being left in the sample tray or in your lab. This venting occurs during the injection time for each current sequence entry. You can disable this feature.

When performing concentrated extractions, you have an additional parameter available: you can vent the vial between concentrating extractions as well as during the final injection.

8 How the 8697 Headspace Sampler Works How the HS Reduces Carryover

69 Operation

How the HS Reduces Carryover The 8697 HS provides two special features to reduce carryover.

After each vial, the HS purges the sample loop and sample probe with a high flow of vial pressurization gas, as defined in the method. This is called the Purge flow, and you control both the flow rate and purge time.

Between each sequence, the HS purges the sample loop and sample probe with a continuous, low flow of vial pressurization gas. This is called the Standby flow. You can control the flow rate.

Operation 70

9 Method Development Overview 71

Consider the Sample and Matrix 72

Consider the GC Inlet 75

Load a Similar Method 76

Edit the New Method 77

Developing and Improving the Method 82

Optimizing Throughput 88

Setting Up for a New Method 89

Perform Blank Runs 90

This chapter provides details and information about method parameters. This information is intended to help a method developer improve a methods performance using the features of the 8697 headspace sampler.

9 Method Development Overview

71 Operation

Overview Figure 22 shows the typical workflow for developing a headspace sampler method.

Figure 22. Workflow for method development

This chapter describes techniques to create and refine a method, using the available method parameters and method features of the 8697 HS. It describes all the method parameters available, and discusses how various parameters impact an analysis.

Start Up the Head- space Sampler.

Configure.

Create Method.

Prepare Samples.

Load Samples.

Create Sequence.

Start.

Evaluate.

If Needed, Refine Method.

Re-evaluate.

If needed, consid- er MHE/MHC.

If Needed, Optimize.

9 Method Development Consider the Sample and Matrix

Operation 72

Consider the Sample and Matrix The first step in developing the method is to understand the sample and matrix.

Theory of headspace analysis The equations describing headspace theory derive from three physical laws associated with vapor pressure, partial pressures, and the relationship between vapor pressure of an analyte above a solution and the concentration of that analyte in the solution.

Daltons law of partial pressures states that the total pressure of a mixture of ideas gases is equal to the sum of the partial pressures of each gas in the mixture.

Henrys law for dilute solutions states that at a constant temperature, the amount of a given gas dissolved in a given type and volume of fluid is directly proportional to the partial pressure of that gas in equilibrium with that fluid.

Raoults law states that the partial pressure of a solute in the headspace volume is proportional to the mole fraction of the solute in solution.

The concentration of sample analyte in the headspace volume is given by mass balance:

where:

CG is the concentration of analyte in the headspace

CO is the concentration of analyte in the original sample

VG is the volume of gas in the sample vial

VL is the volume of sample

K is the partition coefficient (or distribution coefficient), CL/CG at equilibrium VG/VL

COVL = CGVG + CLVL

9 Method Development Impact of K and phase ratio

73 Operation

Rearranging provides:

where:

K is the partition coefficient (or distribution coefficient), CL/CG at equilibrium

VG/VL is also called the phase ratio

The equation shows two important points:

For consistent results, the ratio VG/VL must remain constant. This means that the sample amount and vial size need to be kept the same.

Minimizing the partition coefficient, K, provides higher concentration of sample vapor in the headspace volume.

A smaller VG/VL ratio yields a greater concentration of volatile of interest in the headspace volume

Impact of K and phase ratio The concentration of analyte in the headspace volume depends on many factors, including: sample amount, original concentration of analyte in the sample, available headspace volume, temperature, and total pressure in the vial. Some factors are manipulated in the sample and in the matrix, while others can be controlled using the headspace sampler.

Controlling K

When optimizing a headspace analysis, first consider the partition coefficient of the solvent. The table below lists the K values for several common solvents at 25 C.

At higher temperatures, K will decrease. At 40 C, the K value for ethanol in water is ~1350. At 80 C, the K value lowers to ~330.

As can be seen from the table, K also depends on both the analyte and the matrix. Note the change in K for the ethanol-water system compared to the similar system saturated with Na2SO4.

CG = CO

K + VG VL

Analyte Solvent K (25 C)

Toluene Decane ~3000

Toluene Water ~4

Ethanol Decane ~60

Ethanol Water ~5000

Ethanol Water, saturated with Na2SO4 ~300

9 Method Development Impact of K and phase ratio

Operation 74

Therefore, to improve the concentration of analyte in the headspace volume, heat the sample. If needed, consider changing the solvent (if possible), or consider addition of an inorganic salt to lower the solvent K value.

The other factor to manipulate to increase sensitivity is the phase ratio, VG/VL. Recall the vapor phase concentration equation:

Where K is small, reducing the phase ratio will produce a higher concentration of analyte in the headspace volume. The 8697 can use a variety of sample vials. Select a sample vial and sample amount to create a higher concentration of analyte.

Where K is large, reducing the phase ratio results in less gain.

Controlling the phase ratio

Another factor to manipulate to increase sensitivity is the phase ratio, VG/VL. Recall the vapor phase concentration equation:

Where K is small, reducing the phase ratio will produce a higher concentration of analyte in the headspace volume. The 8697 can use a variety of sample vials. Select a sample vial and sample amount to create a higher concentration of analyte.

Where K is large, reducing the phase ratio results in less gain.

CG = CO

K + VG VL

CG = CO

K + VG VL

9 Method Development Consider the GC Inlet

75 Operation

Consider the GC Inlet Normally, the choice of inlet is determined by the available GC. However, note that for inlet types where the analytical column runs directly into the headspace sampler six port valve, the analytical column is not in the GC oven for its entire length. Peak shapes can change.

With any inlet type, the HS supports only split inlet modes without modification. Splitless inlet modes are supported, but require updated firmware (PID constants) for the inlet EPC module.

9 Method Development Load a Similar Method

Operation 76

Load a Similar Method When starting a new method, begin with a method for a similar sample type.

If using an Agilent data system, the software provides a new method wizard and conversion wizards. The new method wizard provides safe starting temperatures and other parameters for both liquid and solid matrices, using a list of solvent types (including custom values). The wizard also considers the analyte boiling points.

9 Method Development Edit the New Method

77 Operation

Edit the New Method After loading a similar method, edit it as needed for the new sample. This section describes the primary settings, and the following sections describe the extraction modes and other settings.

Temperatures Go to Method > Headspace, scroll to the temperature settings, and enter the desired values for the vial oven, sample loop, and transfer line temperatures.

Times Go to Method > Headspace, scroll to the time settings, and enter desired values for the timing parameters used by the HS.

The HS uses these parameters when determining throughput. The most important value to a sequence of samples is the GC Cycle time. If too short, samples will be prepared before the GC or GC/MS is Ready. Depending on the sequence action settings, this can cause aborted samples or unexpected results. If the GC cycle time is too long, throughput may be reduced, but at least the HS maintains sample processing in accordance with the method.

In addition, there are other timings that the HS considers when loading vials into the oven. Among these are:

Table 7 Temperature parameters

Parameter Comments

Oven Start with an oven temperature 15 C below the solvent boiling point.

Loop Start with this temperature equal to the oven temperature. To prevent condensation of sample, the sample loop and valve should never be lower than the oven temperature.

Transfer Line Start with a temperature 15 C higher than the oven temperature. To prevent condensation of sample, the transfer line should never be lower than the sample loop and valve temperature.

Table 8 Time parameters

Parameter Comments

GC Cycle The total time required for the GC (or GC/MS) system to return to a ready state after a run. See To Determine the GC Cycle Time in the Operation guide.

Vial Equilibration The time the vial spends equilibrating at temperature in the oven, including any shaking. In general, start with a value of at least 15 minutes if an estimated time is unknown.

Injection Duration The time allotted to sweep the sample from the sample loop, through the transfer line, and into the GC. The default inject time is 0.50 minutes.

9 Method Development Vial and Loop

Operation 78

A 30 second wait time for all heated zones to stabilize at temperature

Fixed wait times for actions such as tray moves, carousel moves, and lifter moves

Fixed wait times for valve switches

Other internal processing times

The HS considers all of these timings, as well as the sequence of method setpoints, to determine the most efficient schedule for processing the sample vials.

Vial and Loop Go to Method > Headspace, then scroll to the vial and loop settings.

Fill Modes Go to Method > Headspace, then scroll to the fill mode settings. Note that the settings available depend on the fill mode.

Table 9 Vial and loop parameters

Parameter Comments

Vial Size Select the vial size, 10 mL, 20 mL, or 22 mL.

Shake Value Shaking is available in 9 levels. See Vial shaking. Enter the value (1 through 9) directly, or enter 0 to disable. The browser interface will show the frequency (shakes/minute) and acceleration of the vial at each level.

Table 10 Fill mode parameters

Parameter Comments

Vial Fill Mode Default: Flow to Pressure The HS determines how to fill the sample loop.) See Pressurizing the vial for more information.

Vial Fill Pressure Target sample vial pressure for sampling. The vial pressure must be high enough to transfer the sample through the

sample loop. For some samples, the pressure developed during equilibration is sufficient for

headspace sampling. Do not exceed any vial pressure limit. Avoid setting a value below the pressure developed during equilibration. See Pressurizing the vial for more information.

Vial Fill Flow Avoid a high flow rate if the change in vial pressure between the natural internal pressure after equilibration and the target pressure is small. See Pressurizing the vial for more information.

Fill Volume Used only when the Fill mode is set to Constant Volume. The specific volume of gas with which to pressurize the vial.

Pressure Equilibration Time The time allotted for the vial to equilibrate at pressure during vial pressurization. The default time is 0.50 minutes.

9 Method Development Fill Modes

79 Operation

Loop Fill Mode If using Default, the HS picks reasonable values for the other loop parameters. If using Custom, the other loop parameters become enabled for editing. See Filling the sample loop for more information.

Loop Ramp Rate If in Custom mode, avoid a high fill rate when the difference between vial pressure and loop pressure is small. Default value: 20 psi/min.

Final Loop Pressure If in Custom mode, set the final sample loop pressure. If in Default mode, the final pressure is displayed. See Filling the sample loop for more information.

Loop Equilibration If in Custom mode, default value: 0.05 minutes.

Table 10 Fill mode parameters (continued)

Parameter Comments

9 Method Development Venting and Purging

Operation 80

Venting and Purging Between sample vials, the HS will purge the sample probe, sample loop, and vent. See Figure 23. The default purge flow is 100 mL/min for 0.5 minutes.

Figure 23. Flow paths during purge time

To set the venting and purging parameters, go to Method > Headspace, then scroll to the Venting and Purging settings. These parameters apply only when using an extraction mode other than single. For single extractions, the vial pressure is always vented during the injection cycle.

SV1

PV2

Flow control module

1

2

3 4

5

6

6 port valve

Transfer line

Vent Carrier gas

Vial pressurization gas PS - Pressure sensor FS - Flow sensor SV - Switching valve PV - Proportional valve

PV1

PS

FS

PS

Sample loop

9 Method Development Other parameters

81 Operation

If experiencing carryover, try increasing the purge flow or purge time to sweep any residual sample vapors from the system.

Note that typically, the HS purges the sample probe (including sample loop) and vent for the first half of the purge time, then closes the vent valve to purge just the sample probe (and sample loop). If the purge time is 0.1 to 0.2 minutes, the first 0.1 minutes purges the vent and sample probe, and the remaining time purges only the probe. If the purge time is less than 0.1 minutes, then the HS purges both the sample probe and vent for the entire time.

Other parameters In addition to the parameters described above, the remaining headspace sampler method parameters are discussed in the following sections:

Extraction mode

Dynamic leak check

Method Parameter Summary

Method Sequence Actions

Using parameter increment

If using the optional barcode reader, set the types of barcodes used from the touchscreen under Settings. See Settings > Configuration > Headspace on page 55. On the browser interface, these settings appear under Method > Configuration > Headspace.

Table 11 Venting and purging parameters

Parameter Comments

Vent vial pressure after the last extraction

During an injection cycle that starts a GC run, vent residual vial pressure. The vial is re-pressurized for the next extraction.

Vent vial pressure between extractions

Select to vent the vial pressure between each extraction. The vial is re-pressurized for the next extraction.

Purge Flow Mode Default: The HS purges the sample loop, vent, and sample probe with a 100 mL/min flow of vial pressurization gas for 1 minute. Custom: Enter the purge flow rate and time. Off: Not recommended. The HS does not purge between samples.

Purge Flow The time allotted for the vial to equilibrate at pressure during vial pressurization. The default inject time is 0.50 minutes.

Purge Time The time alloted for the sample probe, loop, and vent to purge.

9 Method Development Developing and Improving the Method

Operation 82

Developing and Improving the Method This section discusses how to improve a method by using various 8697 HS features. It provides useful tips and background information that will help you develop methods using the HS. It is not a general discussion of headspace chromatography, but rather a collection of information to help you use the 8697 HS to best advantage.

Using parameter increment The goal of the initial method is to safely get resultsany results. Once you have determined that a method safely extracts sufficient sample that can be analyzed by the GC (or GC/MS), then next step is typically to empirically determine the equilibration temperature, time, and shaking level that provide the best optimization for your needs.

To do this, use the parameter increment feature of the HS. The parameter increment feature will increase oven temperature, vial equilibration time, or vial shaking level by a set amount in consecutive runs.

To use parameter increment:

1 Open a connection to the GC using the browser interface.

2 Go to the Method tab and load the desired method.

3 Scroll to Miscellaneous (Method Development).

4 Enable Would you like to increment a method setting over subsequent runs?.

5 Select Temperature, Vial shaking, or Vial equilibration hold time.

6 Enter the appropriate parameters. See Oven temperature, Vial equilibration time, or Vial shaking level below for details.

7 Save the method.

8 Determine the number of sample vials needed. The parameter will increment until it exceeds the specified upper limit. (For an example,

see Table 12.) Divide the range by the increment and round up.

9 Prepare the sample vials and load them into the tray (or carousel).

10 Create a sequence to run each vial using the parameter increment method.

11 Start the sequence. The HS will start the sequence, running one vial at a time, and will increment the

selected parameters with each ieteration until it would exceed the specified upper limit on any one parameter.

View the current method parameters using the status display. As the HS increments the method parameter for each new vial, the new value is displayed as the setpoint temperature, time, or shaking level.

Oven temperature

When incrementing oven temperature, consider the following:

9 Method Development Vial size

83 Operation

Higher temperatures generally improve peak areas.

Do not exceed the solvent (or analyte) boiling point.

Incrementing temperature can increase throughput.

All thermal zones increment at the same rate. If a heated zone reaches (or would exceed) its maximum temperature, it will hold at its maximum temperature for any remaining vials. For example, consider a starting oven temperature of 175 C, a transfer line temperature of 200 C, and a sample loop temperature of 190 C. If incrementing 10 C, on the fifth run, sample loop temperature should be 230 C while the oven would be at 215 C. Since the maximum temperature of the sample loop would be exceeded, instead the temperature holds at 225 C for the fifth and sixth runs. See the example in Table 12 below.

Vials in this case are run in series. There is no overlap since the oven temperature differs for each vial.

Do not enter a series that exceeds the number of available vials in the tray.

Vial equilibration time

When incrementing vial equilibration time, consider the following:

Increment equilibration time if increasing temperature might introduce more solvent than analyte, or would degrade the sample.

Vials in this case can be overlapped.

Do not enter a series that exceeds the number of available vials in the tray.

Vial shaking level

When incrementing vial shaking time, consider the following:

Vials in this case must be run in series, since the shaking level differs for each vial.

Shaking helps the most with high-K analytes, larger amounts of liquid sample, and more viscous liquid samples.

Vial size The HS determines the vial size using the gripper or when loading the vial onto the sampling probe.

Table 12 Example temperatures, in C, during parameter increment of 10C per step

Oven Transfer line Sample loop

175 200 190

185 210 200

195 220 210

205 230 220

215 240 225

225 250 225

9 Method Development Vial shaking

Operation 84

Vial shaking The HS can shake vials in the oven at 9 levels. Enter 0 to disable shaking, or enter 1 through 9, with 9 being the highest shaking.

Higher shaking levels can increase area counts at a given oven temperature.

Sample loop size Always configure the correct sample loop size. The HS controls certain operational parameters, such as sample loop filling, based on the configured sample loop volume.

Larger loops can help when performing trace analysis at the limits of detection.

Smaller loops may help peak fidelity when connecting directly to the GC column.

Pressurizing the vial As described in Static Headspace Sampling Using a Valve and Loop on page 9, the HS pressurizes the vial, then vents the vial to atmosphere through the sampling loop. The HS can control the rate of gas transfer through the loop, as well as the initial head pressure within the vial and the residual pressure left in the vial when sampling ends.

For more repeatable results, make sure the vial contains sufficient pressure to sweep the sample loop more than once. If the vial develops less than 70 kPa (10 psi) pressure during thermal equilibration, consider adding additional gas to increase that pressure. If the vial pressure is low, it can cause repeatability issues or low peak areas (due to insufficient sample reaching the sample loop).

The HS can pressurize the vial using 3 different modes. Use a vial pressurization mode appropriate for the sample.

Set a target vial pressure higher than the pressure developed during thermal equilibration. (Otherwise, you will accidentally vent sample!)

Flow to pressure

This is the default vial pressurization mode, and is suitable for most analyses. The HS uses a fixed flow rate to pressurize the vial to a specified level. This provides less shock to the vial.

Avoid a high flow rate if the change in vial pressure is small.

Custom sample loop fill options are available when using this mode.

Pressure

In this mode, the HS pressurizes the vial to the target level as rapidly as possible. This mode duplicates the process used on earlier Agilent headspace samplers (G1888 and 7694). Custom sample loop fill options are available when using this mode.

Constant Volume

In this mode, the vial develops its natural internal pressure. The HS sampler then inserts a fixed volume of gas into the vial. In this case, the actual final vial pressure is not known, since it depends on the initial pressure and the compressibility of the added volume of gas.

9 Method Development Filling the sample loop

85 Operation

Because the internal vial pressure is unknown, this mode precludes using advanced sample loop fill options. The HS will determine the best settings for filling the sample loop.

This mode is useful when the exact molar amounts are important.

When using this mode, it is possible to develop insufficient vial pressure. If the final vial pressure after sampling would be < 1 psi (about 7 kPa), the HS will stop sampling when the sample loop/vial pressure reaches 1 psi.

Filling the sample loop The HS provides two modes for filling the sample loop: Default and Custom. In the Custom mode, you can control the amount of vial pressure used to fill the loop by setting the final residual sample loop (vial) pressure and the ramp rate for filling the sample loop.

Regardless of the mode, you should develop or add sufficient vial pressure before filling the sample loop. Filling the loop relies on the pressure differential between the vial and the loop (which is vented to atmosphere). See Figure 24. With a very low initial vial pressure, for example 7 kPa (1 psi), you will rely more on diffusion than on gas flow for transferring the sample to the loop. Results will suffer.

Figure 24. Sample loop filling

1

2

3 4

5

6

Sample probe

Carrier gas Vent

1

2

3 4

5

6

6 port valve

Transfer line Sample loop

Sample probe

Carrier gas Vial pressurization gasVial pressurization

Sample loop filling

9 Method Development Filling the sample loop

Operation 86

For good, repeatable sample transfer to the loop, develop or add sufficient vial pressure.

If starting from a low initial vial pressure (< 70 kPa/10 psi), try increasing the vial pressure. If the results or repeatability improves, there was insufficient pressure to fill the sample loop.

Default

This mode should be sufficient for many analyses. Based on the initial vial pressure (which is known except when using the Constant Volume vial pressurization mode), the HS calculates an optimum flow rate and final vial pressure for filling the sample loop. The HS will fill the sample loop from the vial, adjusting the flow rate, until the sample loop is swept at least once with sample.

If the initial vial pressure is low, the HS will make adjustments.

The final vial pressure cannot be < 1 psi (6.9 kPa) at NTP.

When using the constant volume vial fill mode, it is possible to develop insufficient vial pressure. If the vial pressure at the start of sampling would result in a final sample loop/vial pressure < 1 psi (~7 kPa), the HS will stop sampling when the sample loop/vial pressure reaches 1 psi.

How the HS calculates the default sample loop fill parameter: The HS takes vial size and atmospheric conditions into account when calculating the default sample loop volume.

NTP pressure displayed on the instrument is Absolute Pressure - 1 standard atmosphere.

Custom

In this mode, you can set the rate at which the loop fills, the final sample loop pressure, and a time for the loop to equilibrate after filling. Refer to Figure 24 as needed.

Loop Ramp Rate: The rate of pressure decay from the vial and through the loop. If you suspect excess sample is being lost during loop fill, lower the flow rate.

Final Loop Pressure: Since the sample loop and vial are connected, this is also the final vial pressure. The HS cannot pull vacuum on a vial.

In general, set a value > 7 kPa (1 psi).

The final pressure should provide enough pressure drop from the initial value to make sure the sample loop is filled.

If set to 0, the HS will control the sample loop fill until the sample loop (and vial) pressure reaches 1 psi (about 6.9 kPa). Then then vent valve will open completely. The HS does not control the sampling system at this point. When the pressure reaches 0 relative to atmospheric, the vent valve closes. Using this setting may not provide repeatable results.

If set to a value between 0 and 1 psi (6.89 kPa), a warning appears. The HS will attempt to control the venting to this value, but there may be a loss in repeatability or sample.

Loop Equilibration: Set a time for the sample loop to stabilize after filling.

Vial Size Absolute Pressure Ramp Rate

10 mL Final Pressure - 2/3 initial pressure 40 psi/min

20 mL Final Pressure - 5/6 initial pressure 20 psi/min

9 Method Development Extraction mode

87 Operation

Possible issues If using a small sample loop, and peaks areas are small, you may be oversweeping the

loop. If the difference between the initial and final vial pressures is too great given the sample conditions and loop size, too much sample may be flowing through the loop to vent. Try reducing the vial pressure or lowering the difference between the initial and final pressures (which reduces the amount of time the headspace volume sweeps the sample loop).

If using a large sample loop, and peak areas are small, you may not be sweeping enough sample into the loop. Try increasing the vial pressure or setting a lower loop final pressure (which increases the length of time the headspace volume sweeps into the sample loop).

Extraction mode There are three (3) extraction modes available, Single, Multiple, and Concentrated. See Sequences, Extraction Modes, and Vial Punctures on page 46 for detailed descriptions of HS behavior for each mode.

Single extraction

In this mode, the HS equilibrates the vial, punctures it once, fills the sample loop (one extraction), then starts a run while injecting the sample onto the GC.

If a vial appears more than once in a sequence, it is completely reprocessed (whether in standalone mode, or if using an Agilent data system).

Multiple extractions

Two typical uses for multiple extraction mode are kinetic studies and calibration.

Note that the vial is punctured only once during the extractions.

Concentrated extractions

This mode can be useful for trace analysis, where the sample can accumulate in the GC inlet or other trap before being swept onto the GC column. This mode requires the use of a multimode inlet or other type of trap.

9 Method Development Optimizing Throughput

Operation 88

Optimizing Throughput The HS automatically manages its timings to maximize the throughput of samples submitted to it for processing. Upon starting a sequence, it compares the methods used for each vial, then determines how and when to place each vial in the oven to minimize any downtime between GC runs. Its analysis depends on:

The HS timing parameters (wait times, equilibration times, and so forth)

The accuracy of the entered GC cycle time

The number of contiguous samples in the sequence that use the same method

The differences in the HS parameters between each method

Any differences between the actual GC run time and the entered values for HS parameters such as carrier gas flow or pressure programs

HS throughput analysis does not consider other GC settings, such as GC oven temperature or inlet temperature changes. The HS cannot account for MS solvent wait time or other external events that occur after the GC run completes. You must include these types of timing issues in the GC Cycle parameter if any becomes important. For example, suppose you temperature program the inlet. The inlet must cool down before the next run. This will take some amount of time, during which the GC is Not Ready and the HS may have samples in the oven. If the cool down takes too long, the samples would remain in the HS oven too long and trigger the System Not Ready sequence action. In this case you may need to consider increasing the GC Cycle.

Practices that may increase throughput:

Group samples that use similar HS oven temperature and shaking.

Arrange samples to avoid heating, then cooling the HS oven. Analyze samples in order of increasing HS oven temperature.

Practices that may reduce throughput:

Entering consecutive lines in the sequence that change HS oven or shaking parameters.

Entering consecutive sequence lines that require HS oven cooling, then heating, then cooling.

9 Method Development Setting Up for a New Method

89 Operation

Setting Up for a New Method While the HS can run sequences that include many methods, all methods used during a single HS sequence must have the following in common:

Same sample loop size

Same gas types

All other parameters, including vial size, can vary between samples in the sequence.

Any sample which requires a different sample loop size or gas type cannot be run at the same time as samples for that other method. Install the necessary hardware and reconfigure the HS.

9 Method Development Perform Blank Runs

Operation 90

Perform Blank Runs Always perform several blank runs after developing a method. Use the blanks to check for carryover. If carryover is found, resolve it. See the Troubleshooting manual.

9 Method Development Perform Blank Runs

91 Operation

Operation 92

10 Early Maintenance Feedback HS Early Maintenance Feedback 93

This chapter discusses the Early Maintenance Feedback features of the headspace sampler.

www.agilent.com Agilent Technologies, Inc. 2021 First edition, February 2021

G4511-90004

HS Early Maintenance Feedback The HS adds several counters to the GCs EMF features, found on the touchscreen or borwser interface at the Maintenance > Headspace. Table 13 below lists the consumable items tracked by the HS, as well as the type of event the HS uses to track the consumable item. For example, the HS tracks transfer line usage by counting injection cycles.

Before beginning a sequence, the GC checks the HS EMF counters for available service life. If running the sequence will cause one of the EMF counters to trigger a service warning, the GC will display a warning message but will not prevent the sequence from running.

Set, reset, or disable HS EMFs just like any other EMF on the GC. Refer to the GC help for more information on using EMFs.

Table 13 8697 Counters

Item Counter </