high temperature headspace vial septa: the difference between the

Static headspace (HS) coupled with gas chromatography (GC) has been widely used for collecting quantitative and qualitative information on the volatile components that are present in complex sample matrices.

• Volatile components released into vapor phase by heating the sample. • Agilent 7697 HS samplers extend temperature range of the sample being heated up to 300°C. • High temperature helps release a wider range of volatile components from sample matrix, thus provide more qualitative and quantitative fingerprint information.

Current widely used PTFE/Silicone based

headspace vial septa are not recommended to use for HS applications above 200°C.

• A series of siloxanes coming from the septa become observable and eventually become the predominant volatile species as baking temperature increased. • These interference peaks significantly impact the reliability and efficiency of headspace analysis at high temperature.

Agilent new High Performance septa have been

demonstrated to provide dramatically cleaner vial blank background with minimum septa contaminations observable.

• HS background at high temperature and pressure conditions were monitored and compared with market available PTFE/silicone septa. • Septum chemical compatibility with common solvents was tested.

Results and Discussion

Agilent High Performance septa provided significantly cleaner HS background under high temperature sample equilibrium condition

Introduction

Pittcon 2012, Orlando, FL Poster 2490-12P

Results and Discussion Experimental Results and Discussion

Conclusions

Results and Discussion

High Temperature Headspace Vial Septa: The Difference between the Success and Failure of High Temperature Headspace-Gas Chromatography Analyses Limian Zhao1, Jared Bushey Agilent Technologies Inc., 2850 Centerville Road, Wilmington, DE 19808 USA

Vial blank samples were equilibrated at 300°C for 30 min. By using High Performance septa, the HS blank chromatogram clearly shows significantly cleaner HS background with minimal contamination.

Agilent High Performance septa provide dramatically cleaner HS background with minimal contamination at high temperature

PTFE/Silicone HS vial septa cause significant contamination at high temperature

Vial blank samples were equilibrated at each temperature for 30 min and initially pressurized to 15 psi but then vented to 10 psi prior to injection. The chromatograms clearly show that the High Performance septa provide consistent and cleaner chromatographic backgrounds with minimal contamination across the entire temperature range examined.

Solvent compatibility test conditions

The qualification tests for the new High Performance septa on the 7697HS-GC/MS system demonstrated: • High Performance septa can provide significantly cleaner HS chromatographic background at high temperatures (up to 300°C) compared to their PTFE/silicone counterparts. However, for high temperature applications, it is not recommended for longer than one hour sample equilibrium time. • High Performance septa have displayed satisfactory chemical compatibility with common headspace solvents. • Steel crimp/screw caps reinforce the seal to the vial and prevent leak during high temperature equilibrium. • The High Performance septa fully support the feature functions of the Agilent 7697 HS sampler for high temperature applications.

To learn more about Agilent High Performance septa, visit us online at http://www.chem.agilent.com/en-US/Products/columns-supplies/generalchromatography/hp_septa The pressure listed represents the initial pressure each vial was charged

to prior to venting. All vials were vented to 10 psi before injection. Vials were equilibrated at 300°C for 30 min. By using High Performance septa, the vial blank chromatogram clearly shows chromatograms with minimal septa contamination from low to high vial initial pressure.

GC/MS Instrument conditions • Agilent 7890A GC/7697A HS samper/5975C MSD • S/SL inlet under split mode @ 250°C with 10:1 of

split ratio • Inlet liner: Direct liner 2 mm ID, deactivated

(Agilent 5181-8818) • He, constant flow @ 2.5 mL/min • DB-5MS UI, 30m x 0.25 mm, 0.25 µm (Agilent p/n

122-5532UI) • Oven profile: 40 °C (1.5 min), 15 °C/min to 325 °C

(2.5min) • MSD: Transfer line @ 250°C, Source @ 230°C,

Quad @ 150°C • Data acquisition: Scan (25 – 570 amu) HS conditions • Oven/Loop & valve/Transfer line temperature

varied from 85 °C to 300 °C for different tests • Vial equilibrate time: 30 min • Vial pressurization gas: He • Fill pressure: varied from 15 psi to 75 psi • Final loop pressure: 10 psi • Sample loop volume: 1 mL • Vial size: 20 mL Tested caps/septa • High Performance septa w/ steel crimp caps

(Agilent p/n 5190-3987) • High Performance septa w/ steel screw caps

(Agilent p/n 5190-3986) • Market available HS caps w/ PTFE/Silicone septa

GC/MS chromatogram of vial blank with PTFE/silicone headspace septa heated at 300°C shows that PTFE/silicon septa cause significant septa contamination when sample being heated at high temperature.

Agilent High Performance septa provide consistent and cleaner HS background at various temperature

Agilent High Performance septa provide consistent and cleaner HS background at various vial initial pressure

Solvent Boiling point (°C)

Oven/Loop & valve/transfer liner temperature (°C)

Volume of sample in

vial

Equilibration time (min)

Vial initialpressure

(psi)

Water 100 85/95/105 1 mL 30 15

10% acetic acid in water Assume 100 85/95/105 1 mL 30 15

TEA 88.7 73/83/93 1 mL 30 15

Toluene 111 96/106/116 1 mL 30 15

DMF 153 138/148/158 1 mL 30 15

DMSO 189 174/184/194 1 mL 30 15

DMAC 165 150/160/170 1 mL 30 15

DMI 225 150/160/170 5 µL 30 15

Agilent High Performance septa provided favorable chemical compatibility with common HS used solvents

TEA: Triethylamine DMF: N,N-dimethylformamide DMSO: Dimethyl sulfoxide DMAC: Dimethylacetamide DMI: 1,3-dimethyl-2-imidazolidinone

GC/MS chromatograms of solvent blank with PTFE/silicone septa and High Performance septa were shown to be equivalent with minimal differences, indicating High Performance septa are compatible with common headspace solvents.

2.00 4.00 6.00 8.00 10.00 12.00 14.00 16.00 18.00 20.00 22.00

0

1e+07

2e+07

3e+07

4e+07

Major septa contamination peaks identification

1. Trimethyl silanol2. Trans-(2-Chlorovinyl)

dimethylethoxysilan3. Hexamethyl cyclotrisiloxane4. Octamethyl

cyclotetrasiloxane5. Decamethyl

cyclopentasiloxane6. Dodecamethyl

cyclohexasiloxane7. Tetradecamethyl

cycloheptasiloxane8. Hexadecamethyl

cyclooctasiloxane9. Octademethyl

cyclononasiloxane10.Eicosamethyl

cyclodecasiloxane

3

4

5

6

7

8

9

102

1

2.00 4.00 6.00 8.00 10.00 12.00 14.00 16.00 18.00 20.00 22.000

1e+07

2e+07

Supplier 3 Thermaseal HS septaClaimed can be used up to 300°C

2.00 4.00 6.00 8.00 10.00 12.00 14.00 16.00 18.00 20.00 22.000

1e+07

2e+07

Supplier 2 PTFE/silicone HS septaClaimed can be used up to 200°C

2.00 4.00 6.00 8.00 10.00 12.00 14.00 16.00 18.00 20.00 22.000

1e+07

2e+07

Supplier 1 PTFE/silicon HS septaClaimed can be used up to 200°C

2.00 4.00 6.00 8.00 10.00 12.00 14.00 16.00 18.00 20.00 22.000

1e+07

2e+07

Agilent High Performance septaSupport high temperature HS analysis up to 300°C

Cyclosiloxanes

2.00 4.00 6.00 8.00 10.00 12.00 14.00 16.00 18.00 20.00 22.000

2000000

4000000

6000000

8000000

1e+07

1.2e+07

1.4e+07

1.6e+07

1.8e+07

Temperature of 85°C




2.00 4.00 6.00 8.00 10.00 12.00 14.00 16.00 18.00 20.00 22.000

100000

200000

300000

400000

500000

600000

700000

800000





Expanded to small abundance scale

2.00 4.00 6.00 8.00 10.00 12.00 14.00 16.00 18.00 20.00 22.000

2000000

4000000

6000000

8000000

1e+07

1.2e+07

1.4e+07

1.6e+07

1.8e+07

Vial initial pressure of 15 psi



2.00 4.00 6.00 8.00 10.00 12.00 14.00 16.00 18.00 20.00 22.000

100000

200000

300000

400000

500000




Expanded to small abundance scale

2.00 4.00 6.00 8.00 10.00 12.00 14.00 16.00 18.00 20.00 22.00

2.00 4.00 6.00 8.00 10.00 12.00 14.00 16.00 18.00 20.00 22.00

2.00 4.00 6.00 8.00 10.00 12.00 14.00 16.00 18.00 20.00 22.00 2.00 4.00 6.00 8.00 10.00 12.00 14.00 16.00 18.00 20.00 22.00

2.00 4.00 6.00 8.00 10.00 12.00 14.00 16.00 18.00 20.00 22.00

1e+072.00 4.00 6.00 8.00 10.00 12.00 14.00 16.00 18.00 20.00 22.00

2e+07

2.00 4.00 6.00 8.00 10.00 12.00 14.00 16.00 18.00 20.00 22.00

1e+07

2e+07

2.00 4.00 6.00 8.00 10.00 12.00 14.00 16.00 18.00 20.00 22.00

2.00 4.00 6.00 8.00 10.00 12.00 14.00 16.00 18.00 20.00 22.00

1e+07

2e+07

2.00 4.00 6.00 8.00 10.00 12.00 14.00 16.00 18.00 20.00 22.00

2.00 4.00 6.00 8.00 10.00 12.00 14.00 16.00 18.00 20.00 22.00

1e+07

2e+07

2.00 4.00 6.00 8.00 10.00 12.00 14.00 16.00 18.00 20.00 22.00

2.00 4.00 6.00 8.00 10.00 12.00 14.00 16.00 18.00 20.00 22.00

2e+07

4e+07

2.00 4.00 6.00 8.00 10.00 12.00 14.00 16.00 18.00 20.00 22.00

2.00 4.00 6.00 8.00 10.00 12.00 14.00 16.00 18.00 20.00 22.00

2e+07

4e+07

2.00 4.00 6.00 8.00 10.00 12.00 14.00 16.00 18.00 20.00 22.00

2.00 4.00 6.00 8.00 10.00 12.00 14.00 16.00 18.00 20.00 22.00

2e+07

4e+07

2.00 4.00 6.00 8.00 10.00 12.00 14.00 16.00 18.00 20.00 22.00

2.00 4.00 6.00 8.00 10.00 12.00 14.00 16.00 18.00 20.00 22.00

2e+07

4e+07

2.00 4.00 6.00 8.00 10.00 12.00 14.00 16.00 18.00 20.00 22.00

2.00 4.00 6.00 8.00 10.00 12.00 14.00 16.00 18.00 20.00 22.00

2e+07

4e+07

2.00 4.00 6.00 8.00 10.00 12.00 14.00 16.00 18.00 20.00 22.00

2.00 4.00 6.00 8.00 10.00 12.00 14.00 16.00 18.00 20.00 22.00

2e+07

4e+07

2.00 4.00 6.00 8.00 10.00 12.00 14.00 16.00 18.00 20.00 22.00

2e+07

4e+07

2.00 4.00. 6.00 8.00 10.00 12.00 14.00 16.00 18.00 20.00 22.00

2.00 4.00 6.00 8.00 10.00 12.00 14.00 16.00 18.00 20.00 22.00

2e+07

4e+07

2.00 4.00 6.00 8.00 10.00 12.00 14.00 16.00 18.00 20.00

2.00 4.00 6.00 8.00 10.00 12.00 14.00 16.00 18.00 20.00 22.00

2e+07

4e+07

2.00 4.00 6.00 8.00 10.00 12.00 14.00 16.00 18.00 20.00 22.00

2e+07

4e+07

2.00 4.00 6.00 8.00 10.00 12.00 14.00 16.00 18.00 20.00 22.00

2.00 4.00 6.00 8.00 10.00 12.00 14.00 16.00 18.00 20.00 22.00

2e+07

4e+07

2.00 4.00 6.00 8.00 10.00 12.00 14.00 16.00 18.00 20.00 22.00

2e+07

4e+07

Water

Solvent blank with PTFE/silicone septum Solvent blank with High Performance septum

10% acetic acid in water

TEA

Toluene

DMF

DMSO

DMAC

DMI

Solvent

high temperature headspace vial septa: the difference between the

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