Analysis of VOCs in complex samples. John R. Dean Northumbria University

Transcription

1 Analysis of VOCs in complex samples John R. Dean Northumbria University

2 Ethylbutanoate O O 1-Octen-3-one O Isovaleric acid (3-methylbutanoic acid) OH O O Methional 2-Phenylethanol OH S VOCs 3-Methylindole (skatole) 2-Methoxyphenol (Guaicaol) O HO N H

3 Ethylbutanoate O O Fruity, apple 1-Octen-3-one O Mushroom, metallic Isovaleric acid (3-methylbutanoic acid) Sweaty OH O O Methional S Boiled potato 2-Phenylethanol OH Wine Roses, sweet VOCs (60) 3-Methylindole (skatole) Faecal N H 2-Methoxyphenol (Guaicaol) O HO Spicy, burnt, sweet

4 Malodour on Laundry

5 Purge gas To GC Trap

6 Does malodour in washing machines cause/contribute to malodour on fabrics? What are the key malodour compounds? On laundry In the washing machine

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9 Overview of experimental Direct olfactive analysis Microbiological tests Swabs of surfaces within machines Consumer washing machines Fabrics washed in machines DHS-GC-O/MS Direct olfactive analysis Microbiological tests HS-SPME-GC-O/MS Microbiological tests HS-SPME-GC-O/MS

10 Overview of experimental Direct olfactive analysis Microbiological tests Swabs of surfaces within machines Consumer washing machines Fabrics washed in machines DHS-GC-O/MS Direct olfactive analysis Microbiological tests HS-SPME-GC-O/MS Microbiological tests HS-SPME-GC-O/MS

11 Machine Definition Malodour? Make and Model Cycle chosen 1 Brand new washing machine No Hotpoint Aquarius WF Cold wash, 800rpm, Woollen, 52 mins 2 Used Washing Machine No Miele Honeycomb Care W3622 Cold wash, 800rpm, Woollen, 39 mins 3 Consumer washing machine (Consumer 1) Yes (Grade 8) Bosch Exxcel 1400 express, maxx freedom performance Cold wash, 800rpm, Woollen (with wash plus), 50 mins 4 Consumer washing machine (Consumer 2) Yes (Grade 6) Hoover Optima OPH714D 7kg 1400 Cold wash, 800rpm, Woollen, 59 mins

12 Machine Definition Malodour? Make and Model Cycle chosen 1 Brand new washing machine No Hotpoint Aquarius WF Cold wash, 800rpm, Woollen, 52 mins 2 Used Washing Machine No Miele Honeycomb Care W3622 Cold wash, 800rpm, Woollen, 39 mins 3 Consumer washing machine (Consumer 1) Yes (Grade 8) Bosch Exxcel 1400 express, maxx freedom performance Cold wash, 800rpm, Woollen (with wash plus), 50 mins 4 Consumer washing machine (Consumer 2) Yes (Grade 6) Hoover Optima OPH714D 7kg 1400 Cold wash, 800rpm, Woollen, 59 mins Olfactive Grade Machine 1 Machine 2 Machine 3 Machine 4 Drawer Rubber seal/drum Sump Coin Trap

13 No. of colony forming units (k) Machine 1 Machine 2 Machine 3 Machine 4 Drawer <0.05 Rubber seal Sump Olfactive Grade Machine 1 Machine 2 Machine 3 Machine 4 Drawer Rubber seal/drum Sump Coin Trap

14 No. of colony forming units (k) Machine 1 Machine 2 Machine 3 Machine 4 Drawer <0.05 Rubber seal Sump Olfactive Grade Machine 1 Machine 2 Machine 3 Machine 4 Drawer Rubber seal/drum Sump Coin Trap

15 Overview of experimental Direct olfactive analysis Microbiological tests Swabs of surfaces within machines Consumer washing machines Fabrics washed in machines DHS-GC-O/MS Direct olfactive analysis Microbiological tests HS-SPME-GC-O/MS Microbiological tests HS-SPME-GC-O/MS

16 Olfactory grading (arbitrary scale) Olfactory grading of fabrics / Washing machine 3 (n = 3) Terry-towel Fleece Washing machine Time (hours)

17 DHS-GC-O/MS of rubber seal of washing machine 3

18 Examples of peak identification* peak number GC-O GC-MS 11 Floral, fragrant α-pinene 14 cheese, sulphur dimethyl trisulphide 22 burnt, fatty, long-lasting nonanal 28 sweet, floral, slightly burnt decanal * Known perfume components (e.g. Eucalyptol) and surfactants (at long retention times) were also detected

19 Overview of experimental Direct olfactive analysis Microbiological tests Swabs of surfaces within machines Consumer washing machines Fabrics washed in machines DHS-GC-O/MS Direct olfactive analysis Microbiological tests HS-SPME-GC-O/MS Microbiological tests HS-SPME-GC-O/MS

20 Microbiological identification of bacteria from washing machines and Analytical Profile Index (API) strips MALDI-TOF-MS

21 Fabrics versus washing machines 62 different microbes identified from 4 washing machines 45 different microbes identified from washed fabrics Majority of microbes were from environmental sources i.e. not pathogenic bacteria.

22 HS-SPME-GC-MS identification of VOCs from bacteria from washing machines and fabrics 10 VOCs commonly identified from bacteria from washing machines and fabrics (fleece and Terrytowel). Dimethyl disulphide; 3-methyl-1-butanol; 2,4- dithiapentane; dimethyl trisulphide; 2-tridecanone; indole; 2-phenylethanol; isovaleric acid; isobutryric acid; and, 1-undecene.

23 HS-SPME-GC-MS of Shewanella putrefaciens from washing machine Peak identifications: (1) dimethyl disulphide; (2) siloxane; (3) 2,4-dithiapentane; (4) siloxane; (5) dimethyl trisulphide; (6) unknown; (7) 2-nonanone; (8) 2-undecanone; (9) isovaleric acid NOTE: Shewanella putrefaciens is a Gram-negative bacteria found in marine environments; it has a rotting fish smell.

24 Conclusions Evidence obtained that points to a possible link that contamination of fabrics occurs from washing machines. Based on the identification of the same bacteria in WM rubber seal and on fabrics. Potential VOC markers for both high levels of bacteria and malodour in washing machines are dimethyl disulphide and dimethyl trisulphide.

25 Gas Chromatography-Ion Mobility Spectrometer

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27 Multi capillary column The MCC comprises a stainless steel tube, 20 cm x 3 mm ID, containing approximately 1200 parallel capillary tubes, 40 m ID, coated with 0.2 m film thickness of stationary phase. Stationary phases: Carbowax 20M (polyethylene glycol) and OV-5 (5% - diphenyl, 95% - dimethylpolysiloxane)

28 Working principle of the IMS IMS Drift Tube Ionisation region Electrical field Drift region Sample inlet Faraday plate Driftgas inlet Outlet BN-Shutter

29 Working principle of the IMS IMS Drift Tube Ionisation region Electrical field Drift region Sample inlet Faraday plate Driftgas inlet Outlet BN-Shutter

30 Signal Working principle of the IMS IMS Drift Tube Ionisation region Electrical field Drift region Sample inlet Faraday plate Driftgas inlet Outlet BN-Shutter Drift time / ms

31 Drift time (ms) Retention time (s)

32 Formation of Reactant Ion Peak (RIP): N 2 N 2 e - N 2 (H 2 O) m H (H 2 O) m-1 OH - N 2 H (H 2 O) m-1 H 3 O (H 2 O) m-2 Formation of monomer, dimer and trimer: RIP X H 3 O (H 2 O) m-2 XH (H 2 O) m-3 H 2 O [XH (H 2 O) m-3 XH 3 O (H 2 O) m-4 ] X XH 3 O (H 2 O) m-4 X 2 H (H 2 O) m-5 H 2 O [X 2 H (H 2 O) m-5 X 2 H 3 O (H 2 O) m-6 ] X X 2 H 3 O (H 2 O) m-6 X 3 H (H 2 O) m-7 H 2 O [X 3 H (H 2 O) m-7 etc]

33 Drift time (ms) Retention time (s)

34 Retention time (s) 2-Dimensional map of 14 VOCs methylvaleric acid dimethyl trisulfide Drift time (ms)

35 Typical operating conditions Compounds in mixture: ethylbutanoate, octanal, E-2-octanal, E-2-nonanal, (E,E)-2,4-nonadienal, (E,E)-2,4-decadienal, 1-decanol, 3-methylindole, 4- methoxybenzaldehyde, guaiacol, 2-phenylethanol, 1-dodecanol Column: Carbowax (polar) Carrier gas flow rate: 150 ml/min Drift gas flow rate: 500 ml/min Column temperature: o C IMS temperature: 45 o C RIP voltage: Positive Incubation time: 10 min Incubation temperature: 95 o C Sample in Vial: 2 ml Injection volume: 2.2 ml Measurement run time: mins Syringe temperature: 95 o C Trigger duration: 100 µs Electric field along IMS tube: 2 kv

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39 Conclusions: GC-IMS Potential for rapid screening of VOCs in samples. Potential to detect small S-, N-containing VOCs. Further work required on authentic samples

40 Acknowledgements