scholarly journals Effects of modular ion-funnel technology onto analysis of breath VOCs by means of real-time mass spectrometry

2020 ◽  
Vol 412 (26) ◽  
pp. 7131-7140
Author(s):  
Giovanni Pugliese ◽  
Felix Piel ◽  
Phillip Trefz ◽  
Philipp Sulzer ◽  
Jochen K. Schubert ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Real Time ◽  
Human Subjects ◽  
Proton Transfer Reaction ◽  
Mass Analyzer ◽  
Real Time Monitoring ◽  
Healthy Human ◽  
Flight Mass Spectrometry ◽  
Ion Funnel ◽  
Tof Ms

Abstract Proton transfer reaction time-of-flight mass spectrometry (PTR-ToF-MS) is a powerful tool for real-time monitoring of trace concentrations of volatile organic compounds (VOCs). The sensitivity of PTR-ToF-MS also depends on the ability to effectively focus and transmit ions from the relatively high-pressure drift tube (DT) to the low-pressure mass analyzer. In the present study, a modular ion-funnel (IF) is placed adjacent to the DT of a PTR-ToF-MS instrument to improve the ion-focusing. IF consists of a series of electrodes with gradually decreasing orifice diameters. Radio frequency (RF) voltage and direct current (DC) electric field are then applied to the electrodes to get the ions focused. We investigated the effect of the RF voltage and DC field on the sensitivity of a pattern of VOCs including hydrocarbons, alcohols, aldehydes, ketones, and aromatic compounds. In a proof-of-concept study, the instrument operating both as normal DT (DC-mode) and at optimal IF conditions (RF-mode) was applied for the breath analysis of 21 healthy human subjects. For the range of investigated VOCs, an improvement of one order of magnitude in sensitivity was observed in RF-mode compared with DC-mode. Limits of detection could be improved by a factor of 2–4 in RF-mode compared with DC-mode. Operating the instrument in RF-mode allowed the detection of more compounds in the exhaled air compared with DC-mode. Incorporation of the IF considerably improved the performance of PTR-ToF-MS allowing the real-time monitoring of a larger number of potential breath biomarkers.

scholarly journals Challenges associated with the sampling and analysis of organosulfur compounds in air using real-time PTR-ToF-MS and off-line GC-FID

2015 ◽  
Vol 8 (12) ◽  
pp. 13157-13197
Author(s):  
V. Perraud ◽  
S. Meinardi ◽  
D. R. Blake ◽  
B. J. Finlayson-Pitts
Keyword(s):  
Real Time ◽  
Dimethyl Sulfide ◽  
Dimethyl Disulfide ◽  
Proton Transfer Reaction ◽  
Organosulfur Compounds ◽  
Negative Effects ◽  
Flight Mass Spectrometry ◽  
Sampling Systems ◽  
Animal Metabolism ◽  
Tof Ms

Abstract. Organosulfur compounds (OSC) are naturally emitted via various processes involving phytoplankton and algae in marine regions, from animal metabolism and from biomass decomposition inland. These compounds are malodorant and reactive. Their oxidation to methanesulfonic and sulfuric acids leads to the formation and growth of atmospheric particles, which are known to have negative effects on visibility, climate and human health. In order to predict particle formation events, accurate measurements of the OSC precursors are essential. Here, two different approaches, proton-transfer reaction time-of-flight mass spectrometry (PTR-ToF-MS) and canister sampling coupled with GC-FID are compared for both laboratory standards [dimethyl sulfide (DMS), dimethyl disulfide (DMDS), dimethyl trisulfide (DMTS) and methanethiol (MTO)] and for a complex sample. Results show that both techniques produce accurate quantification of DMS. While PTR-ToF-MS provides real-time measurements of all four OSCs individually, significant fragmentation of DMDS and DMTS occurs, which can complicate their identification in complex mixtures. Canister sampling coupled with GC-FID provides excellent sensitivity for DMS, DMDS and DMTS. However, MTO was observed to react on metal surfaces to produce DMDS and, in the presence of hydrogen sulfide, even DMTS. Avoiding metal in sampling systems seems to be necessary for measuring all but dimethyl sulfide in air.

Smokers Breath as Seen by Proton-Transfer-Reaction Time-of-Flight Mass Spectrometry (PTR-TOF-MS)

2013 ◽  
pp. 89-116 ◽  
Author(s):  
Ingrid Kohl ◽  
Jens Herbig ◽  
Jürgen Dunkl ◽  
Armin Hansel ◽  
Martin Daniaux ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Reaction Time ◽  
Proton Transfer ◽  
Transfer Reaction ◽  
Time Of Flight ◽  
Proton Transfer Reaction ◽  
Flight Mass Spectrometry ◽  
Tof Ms

scholarly journals Challenges associated with the sampling and analysis of organosulfur compounds in air using real-time PTR-ToF-MS and offline GC-FID

2016 ◽  
Vol 9 (3) ◽  
pp. 1325-1340 ◽  
Author(s):  
Véronique Perraud ◽  
Simone Meinardi ◽  
Donald R. Blake ◽  
Barbara J. Finlayson-Pitts
Keyword(s):  
Real Time ◽  
Dimethyl Sulfide ◽  
Dimethyl Disulfide ◽  
Proton Transfer Reaction ◽  
Organosulfur Compounds ◽  
Flame Ionization ◽  
Flight Mass Spectrometry ◽  
Animal Metabolism ◽  
Negative Impacts ◽  
Tof Ms

Abstract. Organosulfur compounds (OSCs) are naturally emitted via various processes involving phytoplankton and algae in marine regions, from animal metabolism, and from biomass decomposition inland. These compounds are malodorant and reactive. Their oxidation to methanesulfonic and sulfuric acids leads to the formation and growth of atmospheric particles, which are known to influence clouds and climate, atmospheric chemical processes. In addition, particles in air have been linked to negative impacts on visibility and human health. Accurate measurements of the OSC precursors are thus essential to reduce uncertainties in their sources and contributions to particle formation in air. Two different approaches, proton-transfer reaction time-of-flight mass spectrometry (PTR-ToF-MS) and canister sampling coupled to gas chromatography with flame ionization detector (GC-FID), are compared for both laboratory standards (dimethyl sulfide, DMS; dimethyl disulfide, DMDS; dimethyl trisulfide, DMTS; and methanethiol, MTO) and for a complex sample. Results show that both techniques produce accurate quantification of DMS. While PTR-ToF-MS provides real-time measurements of all four OSCs individually, significant fragmentation of DMDS and DMTS occurs, which can complicate their identification in complex mixtures. Canister sampling coupled with GC-FID provides excellent sensitivity for DMS, DMDS, and DMTS. However, MTO was observed to react on metal surfaces to produce DMDS and, in the presence of hydrogen sulfide, even DMTS. Avoiding metal in sampling systems seems to be necessary for measuring all but dimethyl sulfide in air.

scholarly journals Field measurements of methylglyoxal using proton transfer reaction time-of-flight mass spectrometry and comparison to the DNPH–HPLC–UV method

2018 ◽  
Vol 11 (10) ◽  
pp. 5729-5740 ◽  
Author(s):  
Vincent Michoud ◽  
Stéphane Sauvage ◽  
Thierry Léonardis ◽  
Isabelle Fronval ◽  
Alexandre Kukui ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Reaction Time ◽  
Proton Transfer ◽  
Transfer Reaction ◽  
Time Of Flight ◽  
Field Measurements ◽  
Proton Transfer Reaction ◽  
Atmospheric Measurements ◽  
Flight Mass Spectrometry ◽  
Tof Ms

Abstract. Methylglyoxal (MGLY) is an important atmospheric α-dicarbonyl species for which photolysis acts as a significant source of peroxy radicals, contributing to the oxidizing capacity of the atmosphere and, as such, the formation of secondary pollutants such as organic aerosols and ozone. However, despite its importance, only a few techniques exhibit time resolutions and detection limits that are suitable for atmospheric measurements. This study presents the first field measurements of MGLY by proton transfer reaction time-of-flight mass spectrometry (PTR-ToF-MS) performed during the ChArMEx SOP2 field campaign. This campaign took place at a Mediterranean site characterized by intense biogenic emissions and low levels of anthropogenic trace gases. Concomitant measurements of MGLY were performed using the 2,4-dinitrophenylhydrazine (DNPH) derivatization technique and high performance liquid chromatography (HPLC) with UV detection. PTR-ToF-MS and DNPH–HPLC measurements were compared to determine whether these techniques can perform reliable measurements of MGLY. Ambient time series revealed levels of MGLY ranging from 28 to 365 pptv, with a clear diurnal cycle due to elevated concentrations of primary biogenic species during the daytime, and its oxidation led to large production rates of MGLY. A scatter plot of the PTR-ToF-MS and DNPH–HPLC measurements indicates a reasonable correlation (R2=0.48) but a slope significantly lower than unity (0.58±0.05) and a significant intercept of 88.3±8.0 pptv. A careful investigation of the differences between the two techniques suggests that this disagreement is not due to spectrometric interferences from H3O+(H2O)3 or methyl ethyl ketone (or butanal) detected at m∕z 73.050 and m∕z 73.065, respectively, which are close to the MGLY m∕z of 73.029. The differences are more likely due to uncorrected sampling artifacts such as overestimated collection efficiency or loss of MGLY into the sampling line for the DNPH–HPLC technique or unknown isobaric interfering compounds such as acrylic acid and propanediol for the PTR-ToF-MS. Calculations of MGLY loss rates with respect to OH oxidation and direct photolysis indicate similar contributions for these two loss pathways.

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