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 cyrofocused 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 TDU TDU tube Thermal Desorption Unit - TDU No Transfer line ! Cooled Injection System - CIS MPS-HIT Mode New Versions of Maestro (1.4.9.16 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 HIT with CIS Hot HIT with CIS Cold SLH with CIS Hot SLH with CIS Cold Peak #1 = 1,1-Dichloroethene Peak #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) Peak areas in % (DHS = 100 %) 100 mg coffee powder – Relative Peak Areas •% • 100 • 90 • 80 • 70 • • 60 50 • 40 • 30 • • 20 10 • 0 HS SPME DHS SHS and 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. TD-GC GC SHS HS vial volume: 10-20 mL Sample volume: 1-15 mL DHS HS vial volume: 10-20 mL Sample volume: 1-15 mL SHS and DHS These techniques are generally biased toward recovering more volatile compounds or more hydrophobic compounds. TD-GC GC SHS HS vial volume: 10-20 mL Sample volume: 1-15 mL DHS HS vial volume: 10-20 mL Sample volume: 1-15 mL Full Evaporation Technique (FET) FET“Matrix provides more uniform recovery for a variety of independent headspace gas chromatographic analysis. The evaporation technique” compounds andfullsample matrix independent analysis. M. Markelov, J. P. Guzowski, Analytica Chimica Acta, 276 (1993) 235. 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. GC A few μL~ 100℃ Fragrance profiling by FEDHS In 2009, Hoffman et al demonstrate fragrance profiling of consumer products by FEDHS-GC-MS [7]. Adsorbent packed tube A. Hoffmann Purge gas in Shower gel (MeOH blend) 8 μL 80 ℃ 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). 7) A. Hoffmann et al, GERSTEL AppNote 8/2009. In this study, we demonstrate uniform enrichment of a wide FEDHS 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. Adsorbent packed tube Purge gas in 100 μL 80 ℃ 8) N. Ochiai, K. Sasamoto, A. Hoffmann, K. Okanoya, in preparation. Influence of purge volume on the water residue in the Tenax TA trap Water management is very important step in FEDHS because large amount of The purge volume of more than 2.6 L was required water up to 100 μL can be condensed accumulated in the adsorbent trap. 100 μL of water is calculated to and eliminate water. This might be due to re-condensation GC-TCD response (a.u. x 1010) to be 1.8 L of water saturated gas at 40ºC of trap temperature. of a part of water vapor in the vent line of the DHS module at ambient temperature. 8 7 6 5 4 3 2 1 0 1300 1500 1700 1900 2100 2300 2500 Purge volume (mL) 2700 2900 3100 3300 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) 100 WS > log 3.0 mg/L DHS Sample: 1 mL DHS Temp: 25ºC Purge vol.: 3 L 60 40 DHS Sample: 1 mL DHS Temp: 80ºC Purge vol.: 0.35 L 20 HS-SPME Phenethyl alcohol Guaiacol Indole Nonalactone Phenethyl acetate Linalool Nonanal log WS 4.51 (mg/L) log WS 4.40 (mg/L) 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) Damascenone 2-Acetyl thiazoleol log WS 5.65 (mg/L) Citronellol 2,5-Dimethyl pyrazine 0 Butyrolactone Recovery (%) 80 log WS 1.08 (mg/L) 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 100 FEDHS Sample: 0.1 mL DHS Temp: 80ºC Purge vol.: 3 L 80 Sample: 1 mL DHS Temp: 25ºC Purge vol.: 3 L 60 40 DHS Sample: 1 mL DHS Temp: 80ºC Purge vol.: 0.35 L 20 HS-SPME Phenethyl alcohol Guaiacol Indole Nonalactone Phenethyl acetate Linalool Nonanal log WS 4.51 (mg/L) log WS 4.40 (mg/L) 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) Damascenone 2-Acetyl thiazoleol log WS 5.65 (mg/L) Citronellol 2,5-Dimethyl pyrazine 0 Butyrolactone Recovery (%) DHS log WS 1.08 (mg/L) Sample: 1 mL Temp: 80ºC Fiber: CAR/DVB/PDMS Incub. time: 20 min Ext. time: 30 min Gerstel DHS Conditions LVFET DHS Incubation Time (min) 0 2 Purge Volume (mL) 1500 300 Purge Flow (mL) 50 30 Sample Volume (mL) 50 1000 Split Ratio @ CIS Splitless 10:1 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 6200000 6000000 5800000 5600000 5400000 5200000 5000000 4800000 4600000 4400000 4200000 4000000 3800000 3600000 3400000 3200000 3000000 2800000 2600000 2400000 2200000 2000000 1800000 1600000 1400000 1200000 1000000 800000 600000 400000 200000 1 2 2 3 5 6 7 8 9 10 11 12 13 3 14 15 16 17 18 19 20 21 22 23 24 25 Butanal 17 Ethyl acetate Acetic acid 1-Butanol Ethyl propionate Propyl acetate 3-Methyl butanol 2-Methyl butanol Ethyl butyrate Hexanal Butyl acetate Ethyl 2-methylbutyrate 13 Furfural 14 2-Hexenal Cis 3-Hexenol 2-Hexenol 1-Hexanol 2-Acetyl furan Butyrolacton Benzaldehyde Methyl heptenone Hexyl acetate Cis 3-Hexenyl acetate Nonanal Dihydro methyl jasmonate * * 16 4 * 8 2 1 2.00 4.00 6.00 56 8.00 7 11 19-23 15 10.00 12.00 * * 9 10 12 14.00 18 16.00 18.00 25 24 20.00 22.00 24.00 26.00 28.00 Apple Juice with Off-Flavor Overlay with reference (black trace), zoom 4000000 3500000 * 3000000 * * 2500000 2000000 1500000 * 1000000 g-Undecalactone g-Decalactone 500000 0 17.00 18.00 19.00 20.00 21.00 22.00 23.00 24.00 25.00 26.00 27.00 28.00 29.00 Multi Vitamin Juice Sulfur compounds (Markers for Pineapple Juice Content) Limonene 9000000 8500000 8000000 Methyl 3-(methylthio)-propanoate 7500000 7000000 Ethyl 3-(methylthio)-propanoate 6500000 6000000 a-Terpineol 5500000 5000000 4500000 4000000 3500000 3000000 2500000 * * 2000000 * 1500000 * 1000000 * 500000 2.00 4.00 6.00 8.00 10.00 12.00 14.00 16.00 18.00 20.00 22.00 24.00 26.00 28.00 Multi Vitamin Juice Sulfur compounds, extracted ion chromatogram (m/z 61, 74, 134, 148) 75000 70000 65000 60000 55000 Methyl 3-(methylthio)-propanoate m/z 61, 74, 134 Ethyl 3-(methylthio)-propanoate m/z 61, 74, 148 50000 45000 40000 35000 30000 25000 20000 15000 10000 5000 0 18.00 18.50 19.00 19.50 20.00 20.50 21.00 21.50 Multi Vitamin Juice Low in Pineapple Juice Content 75000 70000 65000 60000 55000 50000 45000 40000 35000 30000 25000 Methyl 3-(methylthio)-propanoate m/z 61, 74, 134 Ethyl 3-(methylthio)-propanoate m/z 61, 74, 148 20000 15000 10000 5000 0 18.00 18.50 19.00 19.50 20.00 20.50 21.00 21.50 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) – • MPS-Hot Injection and Trapping Mode (HIT) – • Improves detection limit Full Evaporation Dynamic Headspace Sampling (FEDHS) – • Improves peak shapes Dynamic Headspace Sampling (DHS) – • Improves detection limit More uniform enrichment of analytes SBSE for analysis of nonpolar analytes at ultralow levels Analysis Conditions DHS Incubat Temp Incubat Time Agi On Time Agi Off Time Agi Speed 50°C 0 min 10 s 1s 500 rpm Purge Volume Purge flow Trap Temperature 4000 mL 100 mL/min 30°C Dry Volume Dry Flow Drying Temperature 0 mL 0 mL/min 30°C Transfer Temp 150°C Analysis Conditions TDU Tube Type Carbotrap B/X Pneumatics Mode Sample Mode splitless sample remove Temperature Transferline Temp. 30°C (0.1 min); 720°C/min; 280°C (3 min) 320°C Analysis Conditions CIS 4 LN2 - Cooling Liner Type Glasswool Carrier Gas Pneumatics Mode Vent Flow Vent Pressure Splitflow Helium solvent venting 30 mL/min 51 kPa until 0.0 min 20 mL/min @ 1.0 min Temperature -80°C (0.1 min); 16°C/sec; 150°C; 12°C/sec; 240°C (2 min) Analysis Conditions GC Model Agilent 7890 Column Rxi-624Sil MS (Restek); 30 m x 0.25 mm x 1.4 µm Mode constant flow, 1.0 mL/min Temperature 40°C (2 min); 5°C/min; 100°C; 10°C/min; 300°C (10 min)