Beyond Static Headspace: Automated techniques to extend the limits of headspace analysis for VOCs Edward Pfannkoch Director, Technology Development Gerstel Inc.

MPS 2 Advanced Headspace Capabilities

Advanced Headspace Injection Modes with the MPS 2 Autosampler  Static Headspace (SH)  Multiple Headspace Sample Enrichment (MHSE)  MPS-Hot Injection and Trapping Mode (HIT)  Dynamic Headspace Sampling (DHS)  Full Evaporation Dynamic Headspace Sampling (FEDHS)

Static Headspace Analysis  Equilibration of the solid/liquid samples in crimped vials at a constant temperature

Static Headspace Analysis  Straightforward technique for liquids  Solid samples can present challenges  Limited sensitivity  Limited vial options  Large inj volume = broad early peaks  Distribution coefficient can bias results

Multiple Headspace Sample Enrichment (MHSE) Several samples are taken from the same vial. The analytes are cyro- focused or focused on a packed bed liner in the PTV liner during multiple sample Introductions. Benefit: Improved detection limit

CIS 4 (PTV injector)

MHSE of an Herbal Based Liqueur

MPS-HIT Mode Hot Injection and Trapping

Cooled Injection System - CIS Thermal Desorption Unit - TDU TDU tube TDU No Transfer line !

MPS-HIT Mode  New Versions of Maestro ( and up)  Headspace and SPME Injections can be made into the TDU  CIS can be cooled for trapping or heated for direct transfer to the column  For SHS, allows trapping of analytes in cold inlet while avoiding discrimination of higher boiling components  For SPME, allows trapping/refocusing of volatile analytes from the fiber which can help sharpen early eluting peaks  Allows quick change from thermal desorption to SPME or SHS without removing the TDU

SLH with CIS Hot SLH with CIS Cold HIT with CIS Cold HIT with CIS Hot Peak #1 = 1,1-DichloroethenePeak #26 = 1,2-Dichlorobenzene

Dynamic Headspace (DHS)

Dynamic Headspace Option for MPS 2

Tube Types

Parameters  Incubation temperature:  40 °C (Coffee powder)  25 °C (Shower gel)  Incubation time: 5 min  Purge flow: 20 mL/min  Extraction time:  10 min (Coffee powder, shower gel)  Trap temperature: 25 °C  Trap: TDU tube filled with Tenax-TA  TDU temperature program: 30°C; 720°C/min; 280°C (8 min)  TDU pneumatic setting: Splitless  CIS temperature program: -100°C; 12°C/s; 280°C (8 min)  CIS pneumatic setting: solvent vent (Split 10:1)

2-Methylbutanal Methylpyrazine Dimethylpyrazine Furfural 5-Methyl-2-furancarboxaldehyde 2-Methoxyphenol % Peak areas in % (DHS = 100 %) HS SPME DHS ,3-Pentadione 1-Hydroxy-2-propanone Ethyldimethylpyrazine Furfurylacetat Furfurylalcohole 100 mg coffee powder – Relative Peak Areas

SHS and DHS HS vial volume: mL Sample volume: 1-15 mL GC SHS TD-GC HS vial volume: mL Sample volume: 1-15 mL DHS SHS is equilibrium technique which is controlled by the partitioning coefficient of the solutes between two phases (headspace and sample matrix). DHS prevents the establishment of an equilibration state, causing more of the volatile dispersed in the sample matrix to leave the sample and pass into the headspace.

SHS and DHS HS vial volume: mL Sample volume: 1-15 mL GC SHS TD-GC HS vial volume: mL Sample volume: 1-15 mL DHS These techniques are generally biased toward recovering more volatile compounds or more hydrophobic compounds.

“Matrix independent headspace gas chromatographic analysis. The full evaporation technique” M. Markelov, J. P. Guzowski, Analytica Chimica Acta, 276 (1993) 235. GC FET is the headspace technique of introducing a small amount of sample (mg level) and vaporizing the analytes in the headspace vial at elevated temperatures (typically at 100 ºC), without having to rely on establishing equilibrium between two phases. 100 ℃ A few μL ～ Full Evaporation Technique (FET) FET provides more uniform recovery for a variety of compounds and sample matrix independent analysis.

Fragrance profiling by FEDHS 7) A. Hoffmann et al, GERSTEL AppNote 8/2009. In 2009, Hoffman et al demonstrate fragrance profiling of consumer products by FEDHS-GC-MS [7]. Purge gas in 80 ℃ Adsorbent packed tube 8 μL The FEDHS-GC-MS method enables quantitative extraction of fragrance compounds across a wide range of volatility, leading to results that are closer to the actual fragrance composition than those obtained with other commonly used analysis technique such as simultaneous distillation/extraction (SDE). Shower gel (MeOH blend) A. Hoffmann

8) N. Ochiai, K. Sasamoto, A. Hoffmann, K. Okanoya, in preparation. Purge gas in 80 ℃ 100 μL Adsorbent packed tube FEDHS In this study, we demonstrate uniform enrichment of a wide range of odor compounds in aqueous samples by FEDHS-GC-MS. The optimized purge condition allow complete vaporization of 100 μL of an aqueous sample, and drying it in an adsorbent packed tube, while recovering odor compounds and leaving the low volatile matrix behind.

Influence of purge volume on the water residue in the Tenax TA trap Purge volume (mL) GC-TCD response (a.u. x ) 100 μL of water is calculated to be 1.8 L of water saturated gas at 40ºC of trap temperature. The purge volume of more than 2.6 L was required to eliminate water. This might be due to re-condensation of a part of water vapor in the vent line of the DHS module at ambient temperature. Water management is very important step in FEDHS because large amount of water up to 100 μL can be condensed and accumulated in the adsorbent trap.

Recovery (%) Butyrolactone2,5-Dimethylpyrazine2-Acetyl thiazoleol Phenethyl alcohol GuaiacolIndoleNonalactoneLinaloolNonanalCitronellolDamascenone log WS 5.65 (mg/L) log WS 4.51 (mg/L) log WS 4.40 (mg/L) Phenethyl acetate log WS 4.34 (mg/L) log WS 3.86 (mg/L) log WS 3.18 (mg/L) log WS 3.08 (mg/L) log WS 2.85 (mg/L) log WS 2.83 (mg/L) log WS 2.11 (mg/L) log WS 2.04 (mg/L) log WS 1.08 (mg/L) DHS Sample: 1 mL DHS Temp: 25ºC Purge vol.: 3 L DHS Sample: 1 mL DHS Temp: 80ºC Purge vol.: 0.35 L HS-SPME Sample: 1 mL Temp: 80ºC Fiber: CAR/DVB/PDMS Incub. time: 20 min Ext. time: 30 min Comparison of recovery between conventional DHS, HS-SPME, and FEDHS for test odor compounds in water at 100 ng/mL WS > log 3.0 mg/L WS < log 3.0 (mg/L)

Recovery (%) Butyrolactone2,5-Dimethylpyrazine2-Acetyl thiazoleol Phenethyl alcohol GuaiacolIndoleNonalactoneLinaloolNonanalCitronellolDamascenone log WS 5.65 (mg/L) log WS 4.51 (mg/L) log WS 4.40 (mg/L) Phenethyl acetate log WS 4.34 (mg/L) log WS 3.86 (mg/L) log WS 3.18 (mg/L) log WS 3.08 (mg/L) log WS 2.85 (mg/L) log WS 2.83 (mg/L) log WS 2.11 (mg/L) log WS 2.04 (mg/L) log WS 1.08 (mg/L) DHS Sample: 1 mL DHS Temp: 25ºC Purge vol.: 3 L DHS Sample: 1 mL DHS Temp: 80ºC Purge vol.: 0.35 L HS-SPME Sample: 1 mL Temp: 80ºC Fiber: CAR/DVB/PDMS Incub. time: 20 min Ext. time: 30 min FEDHS Sample: 0.1 mL DHS Temp: 80ºC Purge vol.: 3 L Comparison of recovery between conventional DHS, HS-SPME, and FEDHS for test odor compounds in water at 100 ng/mL

Gerstel DHS Conditions LVFETDHS Incubation Time (min)02 Purge Volume (mL) Purge Flow (mL)5030 Sample Volume (mL) Split CISSplitless10:1 Trap Temperature: 30 deg C Incubation Temperature 80 deg C Tenax TA

FEDHS of Strawberry-Banana Juice

FEDHS of Carrot Juice

FEDHS of Cranberry Juice

FEDHS of Mango Coconut Water

SBSE of Coconut Water

SBSE of Flavored Coconut Water

Applications -Analysis of off odor compounds in apple juice by FEDHS-GC-MS - Analysis of flavor markers in vitamin drink

Apple Juice 14 2-Hexenal 15Cis 3-Hexenol 162-Hexenol 171-Hexanol 182-Acetyl furan 19Butyrolacton 20Benzaldehyde 21Methyl heptenone 22Hexyl acetate 23Cis 3-Hexenyl acetate 24Nonanal 25Dihydro methyl jasmonate * * * * * Butanal 2Ethyl acetate 2Acetic acid 31-Butanol 5Ethyl propionate 6Propyl acetate 73-Methyl butanol 82-Methyl butanol 9Ethyl butyrate 10Hexanal 11Butyl acetate 12Ethyl 2-methylbutyrate 13Furfural

Apple Juice with Off-Flavor Overlay with reference (black trace), zoom  -Decalactone  -Undecalactone * * * *

* * * * * Limonene  -Terpineol Methyl 3-(methylthio)-propanoate Ethyl 3-(methylthio)-propanoate Multi Vitamin Juice Sulfur compounds (Markers for Pineapple Juice Content)

Multi Vitamin Juice Sulfur compounds, extracted ion chromatogram (m/z 61, 74, 134, 148) Methyl 3-(methylthio)-propanoate m/z 61, 74, 134 Ethyl 3-(methylthio)-propanoate m/z 61, 74, 148

Multi Vitamin Juice Low in Pineapple Juice Content Methyl 3-(methylthio)-propanoate m/z 61, 74, 134 Ethyl 3-(methylthio)-propanoate m/z 61, 74, 148

Conclusion Using the MPS 2 autosampler with Maestro software allows automation of the following techniques that can overcome many of the limitations inherent to static headspace sampling: Multiple Headspace Sample Enrichment (MHSE) –Improves detection limit MPS-Hot Injection and Trapping Mode (HIT) –Improves peak shapes Dynamic Headspace Sampling (DHS) –Improves detection limit Full Evaporation Dynamic Headspace Sampling (FEDHS) –More uniform enrichment of analytes SBSE for analysis of nonpolar analytes at ultralow levels

Analysis Conditions DHS Incubat Temp50°C Incubat Time0 min Agi On Time10 s Agi Off Time1 s Agi Speed500 rpm Purge Volume4000 mL Purge flow100 mL/min Trap Temperature30°C Dry Volume0 mL Dry Flow0 mL/min Drying Temperature30°C Transfer Temp150°C

Analysis Conditions TDU Tube TypeCarbotrap B/X Pneumatics Modesplitless Sample Modesample remove Temperature30°C (0.1 min); 720°C/min; 280°C (3 min) Transferline Temp.320°C

Analysis Conditions CIS 4 LN2 - Cooling Liner TypeGlasswool Carrier GasHelium Pneumatics Modesolvent venting Vent Flow30 mL/min Vent Pressure51 kPa until 0.0 min Splitflow min Temperature-80°C (0.1 min); 16°C/sec; 150°C; 12°C/sec; 240°C (2 min)

Analysis Conditions GC ModelAgilent 7890 ColumnRxi-624Sil MS (Restek); 30 m x 0.25 mm x 1.4 µm Modeconstant flow, 1.0 mL/min Temperature40°C (2 min); 5°C/min; 100°C; 10°C/min; 300°C (10 min)