Thermal Desorption combined with dynamic headspace: a versatile tool for miniaturized sample preparation

Thermal Desorption combined with dynamic headspace: a versatile tool for miniaturized sample preparation 4 th Stir Bar Sorptive Extraction Technical Meeting September 18-19, Paris Frank David

Tutorial lay-out Methods for the analysis of volatiles DHS principles DHS modes Examples Positioning DHS versus other methods

Sample Preparation Methods for Volatiles Static Headspace (SHS) Single equilibrium + single injection = classical SHS CTS refocusing Multiple headspace extraction (MHE) Multiple runs (= Kolb method, e.g. Monomers in polymers) Multiple sampling + trapping + single run (eg HIT-SHS, ITEX) Dynamic Headspace (DHS) Purge & Trap (P&T) Sorptive Extraction Solid Phase Micro-Extraction (SPME) New: SPME Arrow (increased volume of extraction phase) Stir Bar Sorptive Extraction (SBSE)

Static Headspace (SHS) Syringe Head Space Bottle Injector

Solid Phase Micro-Extraction (SPME) Pierce sample septum Expose fiber Extract Retract fiber Remove Pierce GC Inlet septum Expose fiber Desorb Retract fiber Remove SORPTION DESORPTION

SHS or SPME Analysis of Halides and Haloalkenes in pharmaceuticals chloromethane (1) benzyl bromide vinyl chloride (2) bromomethane vinyl bromide 4-methylbenzyl chloride (26) iodomethane 4-methylbenzyl bromide 1-chloro-2-methylpropene 1-chloropropane 4-fluorobenzyl chloride 1-bromo-2-methylpropene 1-bromopropane 4-fluorobenzyl bromide 2-chloroacrylonitrile 1-iodopropane 2-chloroethanol 4-chloro-butyl ether (28) 2-chloropropane 2-bromoethanol cis-1,2-dichloroethylene 2-bromopropane 2-iodoethanol trans-1,2-dibromoethylene 2-iodopropane 3-bromo-2-methyl-acrylonitrile 2-(2-chloroethoxy)ethanol benzyl chloride

Analysis of Halides and Haloalkenes Abundance SPME (100 µm PDMS) 15000 10000 5000 T IC : A Z 2 & 3 _ 5 0 0 n g.d \ D A T A S IM.M S ( * ) T IC : 5 0 0 _ S P M E.D \ D A T A S IM.M S ( * ) SHS 0-5000 2 1 26 28 Time--> 4.00 6.00 8.00 10.00 12.00 14.00 16.00 18.00 20.00 22.00 24.00 26.00 Conc: 0.5 ppm in API = 25 ppb in solution

HIT-SHS and HIT-SPME option on Gerstel MPS-TDU-CIS

Dynamic Headspace Continuous purging of headspace (sample) at controlled temperature for controlled time at controlled flow. Trapping of VOCs (adsorbent, sorbent, +/- cryo) Thermal desorption of trap Goal: exhaustive extraction = highest sensitivity He Tenax

DHS TDU

WHY DHS? Abundance 60 VOCs in water 1 ppb GC-MSD in scan mode 160000 Static headspace (SHS) 120000 80000 40000 160000 120000 Sensitivity!! Dynamic headspace (DHS) 80000 40000 Time, min 2.00 4.00 6.00 8.00 10.00 12.00 14.00 16.00 18.00 20.00 22.00 24.00

WHY DHS? Abundance 160000 60 VOCs in water 1 ppb GC-MSD in scan mode Solid phase microextraction (SPME) 65 µm PDMS/DVB 120000 80000 40000 160000 120000 Dynamic headspace (DHS) Sensitivity for the highly volatiles!! and for the other volatiles!! 80000 40000 2.00 4.00 6.00 8.00 10.00 12.00 14.00 16.00 18.00 20.00 22.00 Complete profile less selective 24.00 Time, min

Limonene Method comparison for fruit drink Static Headspace SPME Carbotrap/DVB/PDMS DHS C18 ester (high Mw) 14

DHS vs SPME: aldehydes/ketones in water x10 7 6.5 6 5.5 5 4.5 4 3.5 3 2.5 2 1.5 1 0.5 0 x10 6 8 7 6 5 4 + TIC Scan etalon haut.d + TIC Scan etalon haut SPME 3.D Zoom: x10 DHS-GC-MS SPME-GC-MS 3 2 1 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6 6.5 7 7.5 8 8.5 9 9.5 10 10.5 11 11.5 12 12.5 13 13.5 14 14.5 15 15.5 16 16.5 17 17.5 18 18.5 19 19.5 20 20.5 21 21.5 22 22.5 Counts vs. Acquisition Time (min) Compound TIC area in DHS-GC-MS TIC area in SPME-GC-MS Fold sensitivity increase Acetaldehyde 8495390 270432 31 Hexanal 37701720 3626013 10 2-Nonanone 122894887 24740844 5

Furaneol Furaneol 8 x10 3.5 2.5 1.5 0.5 DHS vs SPME: yoghurt aroma 1 1 5.5 5 4.5 4 3 2 1 0 8 x10 5 4.5 4 3.5 3 2.5 2 1.5 1 0.5 0 +EI TIC Scan 1g yoghurt DHS.D +EI TIC Scan 1g yoghurt -SPME.D 1g yoghurt in the vial DHS-GC-MS SPME-GC-MS 1 1 5.5 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 Counts vs. Acquisition Time (min) trans-hexenal detected @ 10.45 min by DHS and not by SPME

DHS vs SPME: beef powder 250mg powder with 1mL water in 20 ml vial x10 8 +EI TIC Scan 250mg powder+water DHS.D 6.5 1 1 6 5.5 5 4.5 4 3.5 3 2.5 2 1.5 1 0.5 0 x10 8 +EI TIC Scan 250mg powder+1ml water -SPME.D 6 5.5 5 4.5 4 3.5 3 2.5 2 1.5 1 0.5 0 DHS-GC-MS 6.5 1 1 SPME-GC-MS 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 Counts vs. Acquisition Time (min)

DHS vs SPME: Cognac XO 2 ml in 20 ml vial ethanol SPME DHS 18

DHS modes of operation Classical mode: single extraction single run Tenax or Carbotrap adsorption tube without/with dry purge FEDHS: full evaporation DHS MVM: multi-volatile method Multiple tubes & DHS sampling Desorption & trapping Single GC run Derivatization-DHS DHS Large

Same scales Complementary DHS methods for aroma compounds in food acetaldehyde DHS on strong Carbotrap at 10 C Highly volatiles EtOH DHS on Tenax TA at 70 C C18 ester (High Mw)

DHS parameters Extraction (classical DHS) Incubation (sample) temperature (as low as possible) Trap: Material Temperature (higher = less water) Time & flow (= x rinses of vial volume) example: 500 ml volume, 50 ml/min = 10 min = 25 rinses Dry purge??? (loss of volatiles) MVM? TDU: desorption temperature (time, flow) CIS: Focusing temperature (w/ packing?) Injection mode (split, splitless) Injection temperature

Full evaporation dynamic headspace (FEDHS) 100 μl of aqueous sample is dispensed into a HS vial and purged with inert gas at an elevated temperature (80ºC) using DHS. Volatile and semi-volatile analytes are transferred into the trap (Tenax). After dry purge of water, the trap is thermally desorbed for GC analysis. Higher recovery of hydrophilic compounds Purge gas In 100μL~ 80 80

FEDHS method parameters FEDHS conditions Sample volume: 50 µl Trap: Tenax Trap temperature: 40 C Incubation temperature: 80 C Purge: 2500 ml @ 100 ml/min dry purge 500 ml @ 100 ml/min TDU/CIS conditions TDU: 30 C, 60 C/min to 270 C (5 min) Transfer temperature: 280 C (splitless) CIS: -100 C, 12 C/sec to 280 C (7 min) using a Tenax liner

DHS vs FEDHS - GC-MS of coffee x10 7 + TIC Scan DHS Tenax coffee 0,5mL.D 7 6 DHS, 35 C incubation 5 4 3 2 1 0 x10 7 + TIC Scan FEDHS Tenax coffee 0,5mL.D 7 6 FEDHS, 80 C incubation 5 4 3 2 1 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 Counts vs. Acquisition Time (min)

Selectable 1 D/ 2 D analysis of allergens in cosmetics in combination with FEDHS Abundance 1 D chromatogram of a cosmetic sample (body cream) 4.8e+07 4.4e+07 4e+07 3.6e+07 Abundance 2e+07 1.6e+07 1.2e+07 matrix (glycerin) 3.2e+07 8000000 2.8e+07 4000000 2.4e+07 2e+07 10.40 10.80 11.20 11.60 12.00 Time, min 1.6e+07 1.2e+07 8000000 4000000 2.00 4.00 6.00 8.00 10.00 12.00 14.00 16.00 Time, min

Selectable 1 D/ 2 D analysis of allergens in cosmetics in combination with FEDHS Abundance 4.8e+07 1 D/ 2 D chromatogram of body cream Heart-cut 11.08 11.39 min 4e+07 3.2e+07 Co-elution of matrix + heart-cut farnesol 1 & 2 / isoeugenol / hexyl cinnamaldehyde 2.4e+07 1.6e+07 8000000 2 D Target compounds (23 25 min) 5.00 10.00 15.00 20.00 25.00 30.00 Time, min

Selectable 1 D/ 2 D analysis of allergens in cosmetics in combination with FEDHS Extracted Ion Chromatograms from 2 D part Abundance 400000 GLYCERIN ion 61 hexyl cinnamaldehyde ion 216 300000 200000 Farnesol 1 & 2 ion 69 OTHER MATRIX COMPOUND ion 69 100000 isoeugenol ion 164 22.50 23.00 23.50 24.00 24.50 25.00 Time, min

Sequential Dynamic Headspace Sampling incorporating a Multi-Volatile Method (MVM) for Aroma Analysis Developed by Nobuo Ochiai, Kikuo Sasamoto and Jun Tsunokawa @ Gerstel KK

Dynamic Headspace Method 1: Very Volatile Analytes (J. Tsunokawa, N. Ochiai, K. Sasamoto, A. Hoffmann, in preparation)

Dynamic Headspace Method 2: Volatile or Semi Volatile Analytes (J. Tsunokawa, N. Ochiai, K. Sasamoto, A. Hoffmann, in preparation)

Dynamic Headspace Method 3: Volatile, non volatile and hydrophillic analytes (J. Tsunokawa, N. Ochiai, K. Sasamoto, A. Hoffmann, in preparation)

Dynamic Headspace Method 4: TDU Multi Desorption (J. Tsunokawa, N. Ochiai, K. Sasamoto, A. Hoffmann, in preparation)

Acetaldehyde** 2,3-Butanedione* 2,3-Pentanedione* 1-Methyl pyrrole Furan 2-Methyl butanal 3-Methyl butanal** 2,3,5-Trimethylpyrazine* 4-Vinyl guaiacol * Guaiacol* 2-Methyl pyrazine 2-Acetylpyrrole + Maltol 4-Ethylguaiacol* Furaneol*, ** Pyridine Furfuryl alcohol TIC of a brewed coffee by DHS-MVM TIC m/z 117, 90 Indole O NH HO O m/z 62,47 DMS HO O m/z 151, 152 Vanillin* O Sample: Coffee 100 μl Incubation Temp.: 80 ºC Purge volume: 3000 ml Column: DB-WAX 30 m x 0.25 mm i.d., 0.25 μm thickness

Acetaldehyde Furan DMS Propanal 2-Methylfuran Butanal 2,3-Butanedion Pentanal 2,3-Pentanedion DMDS Pyrrole 2,5-Dimethylpyrazine Furfural cis-3-hexenol 1-Hexanol Guaiacol Ethyl decanoate Indole gamma-nonalactone beta-damascenone Coumarin recovery [%] Brewed Coffee Extraction 120 100 80 60 Trap 1 Trap 2 Trap 3 40 20 0

DHS-Multi-Volatile Method (DHS-MVM )* MVM option (Maestro 1.4.29.21 or later) Multiple Tube Desorption FEDHS Method BXX-X Shincarbon trap Top notes Optimized for enrichment of super VOC and top notes Method BX Shincarbon trap Top to middle note Optimized for enrichment of remaining top notes to middle notes FEDHS Tenax TA trap Middle to base note Optimized for enrichment of remaining middle notes to base notes, polar and low boiling compounds Three TDU tube are sequentially thermal desorbed and cryo-focused on CIS, and then injection into GC-MS * N. Ochiai, J. Tsunokawa, K. Sasamoto, A. Hoffmann, J. Chromatogr. A 1371 (2014) 65-73.

Comparison of BXX-X, BX, FEDHS and MVM for analysis of noodle soup stock TIC (BXX-X) TIC (BX) TIC (FEDHS) TIC (MVM) Courtesy: Gerstel KK, Japan

DHS + derivatization Example: Determination of stale-flavor compounds (aldehydes, ketones) using DHS on PFBHA impregnated PDMS tubes and GC-MS Derivatization reaction Pentafluorobenzyl hydroxylamine aldehyde or keton oxime (structural isomers syn/anti) Target solutes: octanal, nonanal, decanal, 2-octenal, 2-nonenal, 2,4-decadienal

Determination of stale-flavor compounds using DHS on PFBHA impregnated PDMS tubes and GC-MS DHS method for impregnation DHS method for DHS of beer samples These methods can be put in one sequence consisting of sequential DHS impregnation and (beer) sample analyses Impregnation + dry purge Sampling + TDU desorption

SIM chromatogram (5 ppb in beer) Abundance Method is applicable also for other aldehydes (formaldehyde, acetaldehyde, ) 40000 35000 30000 Octanal Nonanal Decanal 25000 20000 15000 2-Nonenal 10000 5000 2-Octenal * * * * 2,4-decadienal 8.00 10.00 12.00 14.00 16.00 18.00 20.00 22.00 24.00 2,6-Nonadienal Time, min

Overlaid SIM chromatograms for Beer & spike at 1 ppb Abundance Nonanal (+/-550 ppt) 6400 5600 4800 4000 3200 2400 BEER 2-Octenal (150 ppt).. 2-Nonenal (+/-75 ppt) 2,4-Decadienal.. (25 ppt).. 1600 800 SPIKED 19.00 20.00 21.00 22.00 23.00 24.00 25.00 Time, min

DHS Large option for MPS

Importance of DHS in Flavor Analysis Perception: no technique can deliver the same results as steam destillation (or SAFE) Gerstel DHS: Sensitivity Automation Reduced cross-contamination (e.g. compared to P&T) Flexibility (different modes): DHS > FEDHS > MVM Probably the closest to SDSE & SAFE: full profile 46

Volatiles & Aroma Analysis: my toolbox 1. Static headspace (SHS) 2. HS-SPME (headspace) 3. Dynamic Headspace (DHS) 4. Full evaporation DHS (FEDHS) FEDHS is only technque that has the potential to provide profiles identical to liquid injection. 5. Multi Volatile Method (MVM) Remark: more trapping = more difficult desorption and slower injection Need for additional focussing?

Quid Semi-Volatiles? Often other chromatographic conditions required/used. How much enrichment needed? Method selection 1. (micro-) Liquid-liquid extraction (in-vial extraction) 2. SBSE (immersion!!!) 3. Solid phase extraction (SPE) 4. FEDHS???