Modeling-based determination of physiological parameters of systemic VOCs by breath gas analysis, part 2

In a recent paper we presented a simple two compartment model which describes the influence of inhaled concentrations on exhaled breath concentrations for volatile organic compounds (VOCs) with small Henry constants. In this paper we extend this investigation concerning the influence of inhaled concentrations on exhaled breath concentrations for VOCs with higher Henry constants. To this end we extend our model with an additional compartment which takes into account the influence of the upper airways on exhaled breath VOC concentrations

A selected ion flow tube study of the reactions of gas-phase cations with PSCl3

A selected ion flow tube was used to investigate the positive ion chemistry of thiophosphoryl chloride, PSCl$_3$. Rate coefficients and ion product branching ratios have been determined at room temperature for reactions with nineteen cations ; H$_3$O$^+$, CF$_3^+$, CF$^+$, NO$^+$, NO$_2^+$, SF$_2^+$, SF$^+$, CF$_2^+$, O$_2^+$, H$_2$O$^+$, N$_2$O$^+$, O$^+$, CO$_2^+$, CO$^+$, N$^+$, N$_2^+$, Ar$^+$, F$^+$ and Ne$^+$ (in order of increasing recombination energy). Complementary data described in the previous paper have been obtained for this molecule via the observation of threshold photoelectron photoion coincidences. For ions whose recombination energies are in the range 10-22 eV, comparisons are made between the product ion branching rations of PSCl$_3$ from photoionisation and from ion-molecule reactions. In most instances, the data from the two experiments are well correlated, suggesting that long-range charge transfer is the dominant mechanism for these ion-molecule reactions ; the agreement is particularly good for the atomic ions Ar$^+$, F$^+$ and Ne$^+$. Some reactions (e.g. O$_2^+$ + PSCl$_3$), however, exhibit significant differences; short-range charge transfer must then be occurring following the formation of an ion-molecule complex. For ions whose recombination energies are less than 10 eV (i.e. H$_3$O$^+$, CF$_3^+$, CF$^+$ and NO$^+$), reactions can only occur via a chemical process in which bonds are broken and formed, because the recombination energy of the cation is less than the ionisation energy of PSCl$_3$

Revealing the Ion Chemistry Occurring in High Kinetic Energy-Ion Mobility Spectrometry: A Proof of Principle Study

Here, we present proof of principle studies to demonstrate how the product ions associated with the ion mobility peaks obtained from a High Kinetic Energy-Ion Mobility Spectrometer (HiKE-IMS) measurement of a volatile can be identified using a Proton Transfer Reaction/Selective Reagent Ion-Time-of-Flight-Mass Spectrometer (PTR/SRI-ToF-MS) when operating both instruments at the same reduced electric field value and similar humidities. This identification of product ions improves our understanding of the ion chemistry occurring in the ion source region of a HiKE-IMS. The combination of the two analytical techniques is needed, because in the HiKE-IMS three reagent ions (NO+, H3O+ and O2+•) are present at the same time in high concentrations in the reaction region of the instrument for reduced electric fields of 100 Td and above. This means that even with a mass spectrometer coupled to the HiKE-IMS, the assignment of the product ions to a given reagent ion to a high level of confidence can be challenging. In this paper, we demonstrate an alternative approach using PTR/SRI-ToF-MS that allows separate investigations of the reactions of the reagent ions NO+, H3O+ and O2+•. In this study, we apply this approach to four nitrile containing organic compounds, namely acetonitrile, 2-furonitrile, benzonitrile and acrylonitrile. Both the HiKE-IMS and the PTR/SRI-ToF-MS instruments were operated at a commonly used reduced electric field strength of 120 Td and with gas flows at the same humidities

High Kinetic Energy Ion Mobility Spectrometry- Mass Spectrometry investigations of four inhalation anaesthetics : isoflurane, enflurane, sevoflurane and desflurane

Here we report the first High Kinetic Energy-Ion Mobility Spectrometry-Mass Spectrometric (HiKE-IMSMS) investigations involving four fluranes; isoflurane, enflurane, sevoflurane and desflurane. Unlike standard (atmospheric pressure) IMS, HiKEIMS can detect these compounds in positive ion mode. This is because its low-pressure environment (similar to 14 mbar) and the associated short ion drift times in the HiKEIMS ensure the reagent ions O-2+(center dot) and H3O+ are present in the reaction region, and these can react with the fluranes by dissociative charge and proton transfer, respectively. However, their ion intensities are very dependent on the value of the reduced electric field (E/N) applied and the humidity of the air in the reaction region of the HiKE-IMS. In this paper we explore the potential use of HiKE-IMS for air quality control and breath analysis of fluranes. To help in the interpretation of the ion mobility spectra, and hence the ion-flurane chemistry occurring in reaction region, a HiKE-IMS was coupled to a Time-of-Flight Mass Spectrometer so that the m/z values of both the reagent and product ions that are contained within the various ion mobility peaks observed could be identified with a high level of confidence. The dependencies of the intensities of these ions as functions of E/N (30-115 Td) and humidity in the reaction region are reported. A number of product ions have been observed only under low humidity conditions (H2O volume-mixing ratio 100 ppm(v)), including CHF(2+)and CHFCl (+) for isoflurane and enflurane, CHF2(+), CF3(+) and C3H2F5O+ for desflurane, and CH3O+, CHF2+, C3H3F4O+, C4H3F6O+ and C4H3F6O+(H2O) for sevoflurane. It is interesting to note that CH3O+, CHF2+, CHFCl+ and CF3+ have shorter drift times than that measured for O-2(+center dot) This is explained by resonant charge transfer reaction processes occurring in the drift region: O-2(+center dot) + O-2 ? O-2+(center dot).O O-2 + O-2 +(center dot) (c) 2022 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).Peer reviewe

High kinetic energy-ion mobility spectrometry-mass spectrometry investigations of several volatiles and their fully deuterated analogues

The first High Kinetic Energy-Ion Mobility Spectrometry-Mass Spectrometry (HiKE-IMS-MS) studies involving six volatiles (acetone, acetonitrile, methanol, ethanol, 2-propanol, and 1-butanol) and their fully deuterated analogues are reported. The goal is to further our understanding of the ion-molecule chemistry occurring in the HiKE-IMS. This is needed for its full analytical potential to be reached. Product ions are identified as a function of the reduced electric field (30-115 Td) and the influence of sample air humidity in the reaction region on deuterium/hydrogen (D/H) exchange reactions is discussed. Reagent ions include H3O+(H2O)(m), (n = 0, 1, 2 or 3), NO+(H2O)(n) (m = 0 or 1) and O-2(+center dot). Reactions with H3O+(H2O)(m), lead to protonated monomers (through either proton transfer or ligand switching). Reactions with NO+ involve association with acetone and acetonitrile, hydride anion abstraction from ethanol, 2-propanol, and 1-butanol, and hydroxide abstraction from 2-propanol and 1-butanol. With the exception of acetonitrile, O-2(+center dot) predominantly reacts with the volatiles via dissociative charge transfer. A number of sequential secondary ion-volatile processes occur leading to the formation of dimer and trimer-containing ion species, whose intensities depend on a volatile's concentration and the reduced electric field in the reaction region. Deuterium/hydrogen (D/H) exchange does not occur for product ions from acetone-d(6) and acetonitrile-d(3), owing to their inert methyl functional groups. For the deuterated alcohols, rapid D/H-exchange reaction at the hydroxy group is observed, the amount of which increased with the increasing humidity of the sample air and/or lowering of the reduced electric field.Peer reviewe

A portable sensor system for the detection of human volatile compounds against transnational crime

Human smuggling accounts for a significant part of transnational organized crime, creating a growing threat to national and international security and putting at risk the health and lives of the people being smuggled. Early detection and interception of human beings hidden in containers or trucks are therefore of considerable importance, especially at key transportation hubs, such as at international borders and harbors. The major challenge is to provide fast inspection procedures without needing to open sealed trucks and containers. The detection of trace key volatile organic compounds, which includes aldehydes and ketones, emitted by humans can be used to rapidly determine human presence, requiring only several ml of air to be taken from inside a container. In this paper, we describe a prototype portable device for the rapid detection of hidden or entrapped people, employing a combined ion mobility spectrometer and sensor array system for obtaining a volatile signature of human presence. The detection limits of this combined analytical device are sufficiently low for use in sensing ketones and aldehydes being emitted by humans in closed containers. For easy handling by security personnel, a classification algorithm is applied that provides a simple YES or NO decision. With a training dataset of more than 1000 measurements, the algorithm achieved an area under curve of 0.9 for untrained scenarios. The field measurements show that two people need to stay in a car for between 20 and 30 minutes in order for the emitted trace volatile organic compounds to reach concentrations high enough for reliable detection with our analytical device

The peppermint breath test benchmark for PTR-MS and SIFT-MS

18openInternationalInternational coauthor/editorA major challenge for breath research is the lack of standardization in sampling and analysis. To address this, a test that utilizes a standardized intervention and a defined study protocol has been proposed to explore disparities in breath research across different analytical platforms and to provide benchmark values for comparison. Specifically, the Peppermint Experiment involves the targeted analysis in exhaled breath of volatile constituents of peppermint oil after ingestion of the encapsulated oil. Data from the Peppermint Experiment performed by proton transfer reaction mass spectrometry (PTR-MS) and selected ion flow tube mass spectrometry (SIFT-MS) are presented and discussed herein, including the product ions associated with the key peppermint volatiles, namely limonene, α- and β-pinene, 1,8-cineole, menthol, menthone and menthofuran. The breath washout profiles of these compounds from 65 individuals were collected, comprising datasets from five PTR-MS and two SIFT-MS instruments. The washout profiles of these volatiles were evaluated by comparing the log-fold change over time of the product ion intensities associated with each volatile. Benchmark values were calculated from the lower 95% confidence interval of the linear time-to-washout regression analysis for all datasets combined. Benchmark washout values from PTR-MS analysis were 353 min for the sum of monoterpenes and 1,8-cineole (identical product ions), 173 min for menthol, 330 min for menthofuran, and 218 min for menthone; from SIFT-MS analysis values were 228 min for the sum of monoterpenes, 281 min for the sum of monoterpenes and 1,8-cineole, and 370 min for menthone plus 1,8-cineole. Large inter- and intra-dataset variations were observed, whereby the latter suggests that biological variability plays a key role in how the compounds are absorbed, metabolized and excreted from the body via breath. This variability seems large compared to the influence of sampling and analytical procedures, but further investigations are recommended to clarify the effects of these factors.openHenderson, Ben; Slingers, Gitte; Pedrotti, Michele; Pugliese, Giovanni; Malásková, Michaela; Bryant, Luke; Lomonaco, Tommaso; Ghimenti, Silvia; Moreno, Sergi; Cordell, Rebecca; Harren, Frans J M; Schubert, Jochen; Mayhew, Chris A; Wilde, Michael; Di Francesco, Fabio; Koppen, Gudrun; Beauchamp, Jonathan D; Cristescu, Simona MHenderson, B.; Slingers, G.; Pedrotti, M.; Pugliese, G.; Malásková, M.; Bryant, L.; Lomonaco, T.; Ghimenti, S.; Moreno, S.; Cordell, R.; Harren, F.J.M.; Schubert, J.; Mayhew, C.A.; Wilde, M.; Di Francesco, F.; Koppen, G.; Beauchamp, J.D.; Cristescu, S.M