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Scientific Articles - PTR-MS Bibliography

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Found 775 results
Title [ Year(Asc)]
2015
[1637] Wood, E. C., B. W Knighton, E. C. Fortner, S. C. Herndon, T. B. Onasch, J. P. Franklin, D. R. Worsnop, T. R. Dallmann, D. R. Gentner, A. H. Goldstein, et al., "Ethylene glycol emissions from on-road vehicles.", Environ Sci Technol, vol. 49, pp. 3322–3329, Mar, 2015.
Link: http://dx.doi.org/10.1021/acs.est.5b00557
Abstract
<p>Ethylene glycol (HOCH2CH2OH), used as engine coolant for most on-road vehicles, is an intermediate volatility organic compound (IVOC) with a high Henry&#39;s law coefficient. We present measurements of ethylene glycol (EG) vapor in the Caldecott Tunnel near San Francisco, using a proton transfer reaction mass spectrometer (PTR-MS). Ethylene glycol was detected at mass-to-charge ratio 45, usually interpreted as solely coming from acetaldehyde. EG concentrations in bore 1 of the Caldecott Tunnel, which has a 4% uphill grade, were characterized by infrequent (approximately once per day) events with concentrations exceeding 10 times the average concentration, likely from vehicles with malfunctioning engine coolant systems. Limited measurements in tunnels near Houston and Boston are not conclusive regarding the presence of EG in sampled air. Previous PTR-MS measurements in urban areas may have overestimated acetaldehyde concentrations at times due to this interference by ethylene glycol. Estimates of EG emission rates from the Caldecott Tunnel data are unrealistically high, suggesting that the Caldecott data are not representative of emissions on a national or global scale. EG emissions are potentially important because they can lead to the formation of secondary organic aerosol following oxidation in the atmospheric aqueous phase.</p>
[1666] Yamada, H., S. Inomata, and H. Tanimoto, "Evaporative emissions in three-day diurnal breathing loss tests on passenger cars for the Japanese market", Atmospheric Environment, vol. 107, pp. 166–173, Apr, 2015.
Link: http://dx.doi.org/10.1016/j.atmosenv.2015.02.032
Abstract
<p>Breakthrough emissions that dominate diurnal evaporative emissions from gasoline vehicles were observed in continuous 3-day diurnal breathing loss (DBL) tests. These measurements were conducted on nine vehicles for the Japanese market. Two of these vehicles, made by US and European manufacturers, also meet regulations in their countries of origin. Four vehicles exhibited marked emissions caused by breakthrough emissions during the experimental period, all made by Japanese manufacturers. Using our experimental results, we estimate the total diurnal evaporative emissions from gasoline vehicles in Japan to be 32,792 t y&minus;1. The compositions of the breakthrough and permeation emissions were analyzed in real time using proton transfer reaction plus switchable reagent ion mass spectrometry to estimate the ozone formation potential for the evaporative emissions. The real-time measurements showed that the adsorption of hydrocarbons in a sealed housing evaporative determination unit can result in underestimation, when concentrations are only monitored before and after a DBL test. The composition analysis gave an estimated maximum incremental reactivity (MIR) 20% higher for the breakthrough emissions than for the gasoline that was tested, while the MIR for the permeation emissions was almost the same as the MIR for the fuel. Evaporative emissions from gasoline vehicles in Japan were found to contribute 4.2% to emissions from stationary sources using a mass-based estimate, or 6.1% of emissions from stationary sources using a MIR-based estimate.</p>
[1678] Colard, S., G. O'Connell, P. Sulzer, K. Breiev, X. Cahours, and S. S. Biel, "An Experimental Method to Determine the Concentration of Nicotine in Exhaled Breath and its Retention Rate Following Use of an Electronic Cigarette", J Environ Anal Chem, vol. 02, 2015.
Link: http://dx.doi.org/10.4172/2380-2391.1000161
Abstract
<p>An experimental method is presented for the first time to determine the concentration of nicotine in exhaled breath following e-cigarette use in experienced participants and the impact that vaping topography has on the retention rate of nicotine. Aerosols from e-cigarettes containing different concentrations of nicotine were first evaluated by GC-FID to determine the concentration of nicotine delivered per puff versus machine - vaping intensity. These e-cigarettes were then vaped by participants through a cigarette holder attached to a smoking topography analyzer which recorded puff volume and puff duration. This allowed the concentration of nicotine in the aerosol inhaled by the participant during each puff to be determined. A PTR-MS instrument was then used to determine the concentration of nicotine exhaled following each use of the e-cigarette. By dividing this figure by the nicotine concentration delivered enabled its retention rate to be calculated. The principal finding was over 99% of the nicotine was retained by the participants when the e-cigarette aerosol was inhaled and a reduced but still substantial quantity was retained (on average 86%) when the e-cigarette aerosol was held in the mouth only (i.e, no inhalation). In both cases, the nicotine concentrations detected in the exhaled breath were low (range 1.8 - 1786 ppb). The experimental method presented here may be used to determine the concentration of other e-cigarette aerosol constituents in exhaled breath and the retention rate of those constituents which is useful for the evaluation of e-cigarettes from a consumer and bystander perspective.</p>
[1627] Sahu, L.K.., and P. Saxena, "High time and mass resolved PTR-TOF-MS measurements of VOCs at an urban site of India during winter: Role of anthropogenic, biomass burning, biogenic and photochemical sources", Atmospheric Research, vol. 164-165, pp. 84–94, Oct, 2015.
Link: http://dx.doi.org/10.1016/j.atmosres.2015.04.021
Abstract
<p>This study is based on the high mass and time-resolved measurements of seven VOCs using a PTR-TOF-MS instrument at an urban site of India during winter 2013. Daily levels of OVOCs and aromatics were in the ranges of 3.5&ndash;37 ppbv and 0.85&ndash;23 ppbv, respectively with OVOCs accounted for up to 80% of total measured VOCs. The impact of long-range transport from the polluted Indo-Gangetic Plain and clean Thar desert was observed during the episodes of high and low VOCs, respectively. VOCs exhibited strong diurnal variations with peaks during morning and evening hours and lowest in the afternoon. Relatively elevated aromatics during evening hours coincided with the lowest-OVOCs indicating influence of fresh vehicular emissions. Emission ratios of isoprene and OVOCs with respect to benzene followed the diurnal cycles of temperature and solar flux indicating role of biogenic and photochemical processes, respectively. Correlation study of VOCs with benzene suggests major contribution from anthropogenic and also from biogenic and secondary sources to some extent. The higher emission ratios of ∆methanol/∆acetonitrile correspond to the episodes of long-range transport from biomass burning sources located in the Indo-Gangetic Plain (IGP). In addition to the pattern of emission, the diurnal and day-to-day variations of VOCs were influenced by the local meteorological conditions and depth of planetary boundary layer (PBL).</p>
[1710] Gamero-Negrón, R., J. {Sánchez Del Pulgar}, L. Cappellin, C. García, F. Gasperi, and F. Biasioli, "Immune-spaying as an alternative to surgical spaying in Iberian × Duroc females: Effect on the VOC profile of dry-cured shoulders and dry-cured loins as detected by PTR-ToF-MS.", Meat Sci, vol. 110, pp. 169–173, Dec, 2015.
Link: http://dx.doi.org/10.1016/j.meatsci.2015.07.018
Abstract
<p>Immunocastration in pigs has been proposed as a cruelty-free alternative to surgical castration. In this work the effect of immune-spaying of female pigs on the volatile compound profile of Iberian dry-cured products was evaluated. The head-space volatile compound of dry-cured shoulders and loins from surgically spayed, immune-spayed and entire Iberian &times; Duroc females was characterized by proton transfer reaction-time of flight-mass spectrometry. It was not possible to identify a significant effect of the castration modality on dry-cured shoulders, probably because of the heterogeneity of samples. Contrarily, Principal Component Analysis of dry-cured loins indicates a better homogeneity of samples and the separation of loins from surgically spayed and immune-spayed females. Some mass peaks tentatively identified as important flavor compounds in dry-cured products, 3-methylbutanal, 2,3-butanedione and 3-methylbutanoic acid, were significantly higher in the immune-spayed females. Therefore, immune-spaying seems to have a negligible effect on the volatile compound profile of dry-cured shoulders, whereas it could affect the VOC profile in the case of dry-cured loins.</p>
[1715] Sukul, P., P. Trefz, S. Kamysek, J. K. Schubert, and W. Miekisch, "Instant effects of changing body positions on compositions of exhaled breath.", J Breath Res, vol. 9, pp. 047105, Dec, 2015.
Link: http://dx.doi.org/10.1088/1752-7155/9/4/047105
Abstract
<p>Concentrations of exhaled volatile organic compounds (VOCs) may depend not only on biochemical or pathologic processes but also on physiological parameters. As breath sampling may be done in different body positions, effects of the sampling position on exhaled VOC concentrations were investigated by means of real-time mass spectrometry. Breaths from 15 healthy volunteers were analyzed in real-time by PTR-ToF-MS-8000 during paced breathing (12/min) in a continuous side-stream mode. We applied two series of body positions (setup 1: sitting, standing, supine, and sitting; setup 2: supine, left lateral, right lateral, prone, and supine). Each position was held for 2&thinsp;min. Breath VOCs were quantified in inspired and alveolar air by means of a custom-made algorithm. Parallel monitoring of hemodynamics and capnometry was performed noninvasively. In setup 1, when compared to the initial sitting position, normalized mean concentrations of isoprene, furan, and acetonitrile decreased by 24%, 26%, and 9%, respectively, during standing and increased by 63%, 36%, and 10% during lying mirroring time profiles of stroke volume and pET-CO2. In contrast, acetone and H2S concentrations remained almost constant. In setup 2, when compared to the initial supine position, mean alveolar concentrations of isoprene and furan increased significantly up to 29% and 16%, respectively, when position was changed from lying on the right side to the prone position. As cardiac output and stroke volume decreased at that time, the reasons for the observed concentrations changes have to be linked to the ventilation/perfusion ratio or compartmental distribution rather than to perfusion alone. During final postures, all VOC concentrations, hemodynamics, and pET-CO2 returned to baseline. Exhaled blood-borne VOC profiles changed due to body postures. Changes depended on cardiac stroke volume, origin, compartmental distribution and physico-chemical properties of the substances. Patients&#39; positions and cardiac output have to be controlled when concentrations of breath VOCs are to be interpreted in terms of biomarkers.</p>
[1625] Hu, L., D. B. Millet, M. Baasandorj, T. J. Griffis, P. Turner, D. Helmig, A. J. Curtis, and J. Hueber, "Isoprene emissions and impacts over an ecological transition region in the US Upper Midwest inferred from tall tower measurements", Journal of Geophysical Research: Atmospheres, Mar, 2015.
Link: http://dx.doi.org/10.1002/2014JD022732
Abstract
<p>We present one year of in-situ PTR-MS measurements of isoprene and its oxidation products MVK and MACR from a 244 m tall tower in the US Upper Midwest, located at an ecological transition between isoprene-emitting deciduous forest and predominantly non-isoprene-emitting agricultural landscapes. We find that anthropogenic interferences (or anthropogenic isoprene) contribute on average 20% of the PTR-MS m/z 69 signal during summer daytime, whereas MVK+MACR interferences (m/z 71) are minor (7%). After removing these interferences, the observed isoprene and MVK+MACR abundances show pronounced seasonal cycles, reaching summertime maxima of &gt;2500 pptv (1-hour mean). The tall tower is impacted both by nearby and more distant regional isoprene sources, with daytime enhancements of isoprene (but little MVK+MACR) under southwest winds, and enhancements of MVK+MACR (but little isoprene) at other times. We find that the GEOS-Chem atmospheric model with the MEGANv2.1 biogenic inventory can reproduce the isoprene observations to within model uncertainty given improved land cover and temperature estimates. However, a 60% low model bias in MVK+MACR cannot be resolved, even across diverse model assumptions for NOx emissions, chemistry, atmospheric mixing, dry deposition, land cover, and potential measurement interferences. This implies that, while isoprene emissions in the immediate vicinity of the tall tower are adequately captured, they are underestimated across the broader region. We show that this region experiences a strong seasonal shift between VOC-limited chemistry during the spring and fall and NOx-limited or transitional chemistry during the summer, driven by the spatiotemporal distribution of isoprene emissions. Isoprene&#39;s role in causing these chemical shifts is likely underestimated due to the underprediction of its regional emissions.</p>
[1623] Baasandorj, M.., D.. B. Millet, L.. Hu, D.. Mitroo, and B.. J. Williams, "Measuring acetic and formic acid by proton-transfer-reaction mass spectrometry: sensitivity, humidity dependence, and quantifying interferences", Atmos. Meas. Tech., vol. 8, pp. 1303–1321, 2015.
Link: http://dx.doi.org/10.5194/amt-8-1303-2015
Abstract
We present a detailed investigation of the factors governing the quantification of formic acid (FA), acetic acid (AA), and their relevant mass analogues by proton-transfer-reaction mass spectrometry (PTR-MS), assess the underlying fragmentation pathways and humidity dependencies, and present a new method for separating FA and AA from their main isobaric interferences. PTR-MS sensitivities towards glycolaldehyde, ethyl acetate, and peroxyacetic acid at m/z 61 are comparable to that for AA; when present, these species will interfere with ambient AA measurements by PTR-MS. Likewise, when it is present, dimethyl ether can interfere with FA measurements. For a reduced electric field (E/N) of 125 Townsend (Td), the PTR-MS sensitivity towards ethanol at m/z 47 is 5–20 times lower than for FA; ethanol will then only be an important interference when present in much higher abundance than FA. Sensitivity towards 2-propanol is <1% of that for AA, so that propanols will not in general represent a significant interference for AA. Hydrated product ions of AA, glycolaldehyde, and propanols occur at m/z 79, which is also commonly used to measure benzene. However, the resulting interference for benzene is only significant when E/N is low (<= 100 Td). Addition of water vapor affects the PTR-MS response to a given compound by (i) changing the yield for fragmentation reactions and (ii) increasing the importance of ligand switching reactions. In the case of AA, sensitivity to the molecular ion increases with humidity at low E/N but decreases with humidity at high E/N due to water-driven fragmentation. Sensitivity towards FA decreases with humidity throughout the full range of E/N. For glycolaldehyde and the alcohols, the sensitivity increases with humidity due to ligand switching reactions (at low E/N) and reduced fragmentation in the presence of water (at high E/N). Their role as interferences will typically be greatest at high humidity. For compounds such as AA where the humidity effect depends strongly on the collisional energy in the drift tube, simple humidity correction factors (XR) will only be relevant for a specific instrumental configuration. We recommend E/N   125 Td as an effective condition for AA and FA measurements by PTR-MS, as it optimizes between the competing E/N-dependent mechanisms controlling their sensitivities and those of the interfering species. Finally, we present the design and evaluation of an online acid trap for separating AA and FA from their interfering species at m/z 61 and 47, and we demonstrate its performance during a field deployment to St. Louis, USA, during August–September of 2013.
[1679] Hayeck, N., B. Temime-Roussel, S. Gligorovski, A. Mizzi, R. Gemayel, S. Tlili, P. Maillot, N. Pic, T. Vitrani, I. Poulet, et al., "Monitoring of organic contamination in the ambient air of microelectronic clean room by proton-transfer reaction/time-of-flight/mass spectrometry (PTR-ToF-MS)", International Journal of Mass Spectrometry, Oct, 2015.
Link: http://dx.doi.org/10.1016/j.ijms.2015.09.017
Abstract
<p>The organic contamination has been recently considered as the most important problem for the photolithography world in the semiconductor industry, especially when the photolithographic methods moved from 130 nm node to 32 nm node. One of the most common organic compounds found in photolithography areas of the clean room is Trimethylsilanol (TMS), which can adsorb on the optical lenses forming a thin molecular layer, hence causing damages. Salt crystal formation is another potential threat for the optical devices. In the clean rooms, this salt is produced by a light-induced reaction between ammonia and an acid. In the context of semiconductor industry, the involved acid is usually the acetic acid produced by hydrolysis from propylene glycol methyl ether acetate (PGMEA), a commonly used organic compound in the photolithography. Here, we present an innovative analytical method using a state-of-the-art proton-transfer reaction&ndash;time-of-flight&ndash;mass spectrometer (PTR&ndash;ToF&ndash;MS) for on-line and continuous survey of volatile organic compounds (VOCs) with an emphasis on TMS and PGMEA. The effect of relative humidity on the detection and fragmentation of these organic compounds was assessed. The new analytical method is operated in a real life clean room environment and the results were compared with those obtained with off-line measurements using automated thermal desorber&ndash;gas chromatography&ndash;mass spectrometry (ATD&ndash;GC&ndash;MS) as reference method. The contamination sources were detected and identified, which is of paramount importance for the microelectronic fabrication plant. The trapping efficiency of the chemical filters used for AMCs filtration in the photolithography zone was determined.</p>
[1655] Materic, D., M. Lanza, P. Sulzer, J. Herbig, D. Bruhn, C. Turner, N. Mason, and V. Gauci, "Monoterpene separation by coupling proton transfer reaction time-of-flight mass spectrometry with fastGC", Analytical and Bioanalytical Chemistry, Aug, 2015.
Link: http://dx.doi.org/10.1007/s00216-015-8942-5
Abstract
<p>Proton transfer reaction mass spectrometry (PTR-MS) is a well-established technique for real-time analysis of volatile organic compounds (VOCs). Although it is extremely sensitive (with sensitivities of up to 4500 cps/ppbv, limits of detection &lt;1 pptv and the response times of approximately 100 ms), the selectivity of PTR-MS is still somewhat limited, as isomers cannot be separated. Recently, selectivity-enhancing measures, such as manipulation of drift tube parameters (reduced electric field strength) and using primary ions other than H3O+, such as NO+ and O2 +, have been introduced. However, monoterpenes, which belong to the most important plant VOCs, still cannot be distinguished so more traditional technologies, such as gas chromatography mass spectrometry (GC-MS), have to be utilised. GC-MS is very time consuming (up to 1 h) and cannot be used for real-time analysis. Here, we introduce a sensitive, near-to-real-time method for plant monoterpene research&mdash;PTR-MS coupled with fastGC. We successfully separated and identified six of the most abundant monoterpenes in plant studies (α- and β-pinenes, limonene, 3-carene, camphene and myrcene) in less than 80 s, using both standards and conifer branch enclosures (Norway spruce, Scots pine and black pine). Five monoterpenes usually present in Norway spruce samples with a high abundance were separated even when the compound concentrations were diluted to 20 ppbv. Thus, fastGC-PTR-ToF-MS was shown to be an adequate one-instrument solution for plant monoterpene research.</p>
[1711] Materic, D., M. Lanza, P. Sulzer, J. Herbig, D. Bruhn, C. Turner, N. Mason, and V. Gauci, "Monoterpene separation by coupling proton transfer reaction time-of-flight mass spectrometry with fastGC.", Anal Bioanal Chem, vol. 407, pp. 7757–7763, Oct, 2015.
Link: http://dx.doi.org/10.1007/s00216-015-8942-5
Abstract
<p>Proton transfer reaction mass spectrometry (PTR-MS) is a well-established technique for real-time analysis of volatile organic compounds (VOCs). Although it is extremely sensitive (with sensitivities of up to 4500 cps/ppbv, limits of detection &lt;1 pptv and the response times of approximately 100 ms), the selectivity of PTR-MS is still somewhat limited, as isomers cannot be separated. Recently, selectivity-enhancing measures, such as manipulation of drift tube parameters (reduced electric field strength) and using primary ions other than H3O(+), such as NO(+) and O2 (+), have been introduced. However, monoterpenes, which belong to the most important plant VOCs, still cannot be distinguished so more traditional technologies, such as gas chromatography mass spectrometry (GC-MS), have to be utilised. GC-MS is very time consuming (up to 1 h) and cannot be used for real-time analysis. Here, we introduce a sensitive, near-to-real-time method for plant monoterpene research-PTR-MS coupled with fastGC. We successfully separated and identified six of the most abundant monoterpenes in plant studies (α- and β-pinenes, limonene, 3-carene, camphene and myrcene) in less than 80 s, using both standards and conifer branch enclosures (Norway spruce, Scots pine and black pine). Five monoterpenes usually present in Norway spruce samples with a high abundance were separated even when the compound concentrations were diluted to 20 ppbv. Thus, fastGC-PTR-ToF-MS was shown to be an adequate one-instrument solution for plant monoterpene research.</p>
[1825] Eichler, P., M. Müller, B. D{\textquotesingle}Anna, and A. Wisthaler, "A novel inlet system for online chemical analysis of semi-volatile submicron particulate matter", Atmospheric Measurement Techniques, vol. 8, pp. 1353–1360, mar, 2015.
Link: https://www.atmos-meas-tech.net/8/1353/2015/
Abstract
<p>We herein present a novel modular inlet system designed to be coupled to low-pressure gas analyzers for online chemical characterization of semi-volatile submicron particles. The &quot;chemical analysis of aerosol online&quot; (CHARON) inlet consists of a gas-phase denuder for stripping off gas-phase analytes, an aerodynamic lens for particle collimation combined with an inertial sampler for the particle-enriched flow and a thermodesorption unit for particle volatilization prior to chemical analysis. The denuder was measured to remove gas-phase organics with an efficiency &gt; 99.999% and to transmit particles in the 100&ndash;750 nm size range with a 75&ndash;90% efficiency. The measured average particle enrichment factor in the subsampling flow from the aerodynamic lens was 25.6, which is a factor of 3 lower than the calculated theoretical optimum. We coupled the CHARON inlet to a proton-transfer-reaction time-of-flight mass spectrometer (PTR-ToF-MS) which quantitatively detects most organic analytes and ammonia. The combined CHARON-PTR-ToF-MS setup is thus capable of measuring both the organic and the ammonium fraction in submicron particles in real time. Individual organic compounds can be detected down to levels of 10&ndash;20 ng m&minus;3. Two proof-of-principle studies were carried out for demonstrating the analytical power of this new instrumental setup: (i) oxygenated organics and their partitioning between the gas and the particulate phase were observed from the reaction of limonene with ozone and (ii) nicotine was measured in cigarette smoke particles demonstrating that selected organic target compounds can be detected in submicron particles in real time.</p>
[1664] Zannoni, N.., V.. Gros, M.. Lanza, R.. Sarda, B.. Bonsang, C.. Kalogridis, S.. Preunkert, M.. Legrand, C.. Jambert, C.. Boissard, et al., "OH reactivity and concentrations of Biogenic Volatile Organic Compounds in a Mediterranean forest of downy oak trees", Atmos. Chem. Phys. Discuss., vol. 15, pp. 22047--22095, 2015.
Link: http://dx.doi.org/10.5194/acpd-15-22047-2015
Abstract
<p>Abstract. Understanding the processes between the biosphere and the atmosphere is challenged by the difficulty to determine with enough accuracy the composition of the atmosphere. Total OH reactivity, which is defined as the total loss of the hydroxyl radical in the atmosphere, has proved to be an excellent tool to identify indirectly the important reactive species in ambient air. High levels of unknown reactivity were found in several forests worldwide and were often higher than at urban sites. Such results demonstrated the importance of OH reactivity for characterizing two of the major unknowns currently present associated to forests: the set of primary emissions from the canopy to the atmosphere and biogenic compounds oxidation pathways. Previous studies also highlighted the need to quantify OH reactivity and missing OH reactivity at more forested sites. Our study presents results of a field experiment conducted during late spring 2014 at the forest site at the Observatoire de Haute Provence, OHP, France. The forest is mainly composed of downy oak trees, a deciduous tree species characteristic of the Mediterranean region. We deployed the Comparative Reactivity Method and a set of state-of-the-art techniques such as Proton Transfer Reaction-Mass Spectrometry and Gas Chromatography to measure the total OH reactivity, the concentration of volatile organic compounds and main atmospheric constituents at the site. We sampled the air masses at two heights: 2 m, i.e. inside the canopy, and 10 m, i.e. above the canopy, where the mean canopy height is 5 m. We found that the OH reactivity at the site mainly depended on the main primary biogenic species emitted by the forest, which was isoprene and to a lesser extent by its degradation products and long lived atmospheric compounds (up to 26 % during daytime). We determined that the daytime total measured reactivity equaled the calculated reactivity obtained from the concentrations of the compounds measured at the site. Hence, no significant missing reactivity is reported in this specific site, neither inside, nor above the canopy. However, during two nights we reported a missing fraction of OH reactivity up to 50 %, possibly due to unmeasured oxidation products. Our results confirm the weak intra canopy oxidation, already suggested in a previous study focused on isoprene fluxes. They also demonstrate how helpful can be the OH reactivity as a tool to clearly characterize the suite of species present in the atmosphere. We show that our result of reactivity is among the highest reported in forests worldwide and stress the importance to quantify OH reactivity at more and diverse Mediterranean forests.</p>
[1708] Fu, H., R. Ciuraru, Y. Dupart, M. Passananti, L. Tinel, S. Rossignol, S. Perrier, J. D Donaldson, J. Chen, and C. George, "Photosensitized Production of Atmospherically Reactive Organic Compounds at the Air/Aqueous Interface.", J Am Chem Soc, vol. 137, pp. 8348–8351, Jul, 2015.
Link: http://dx.doi.org/10.1021/jacs.5b04051
Abstract
<p>We report on experiments that probe photosensitized chemistry at the air/water interface, a region that does not just connect the two phases but displays its own specific chemistry. Here, we follow reactions of octanol, a proxy for environmentally relevant soluble surfactants, initiated by an attack by triplet-state carbonyl compounds, which are themselves concentrated at the interface by the presence of this surfactant. Gas-phase products are determined using PTR-ToF-MS, and those remaining in the organic layer are determined by ATR-FTIR spectroscopy and HPLC-HRMS. We observe the photosensitized production of carboxylic acids as well as unsaturated and branched-chain oxygenated products, compounds that act as organic aerosol precursors and had been thought to be produced solely by biological activity. A mechanism that is consistent with the observations is detailed here, and the energetics of several key reactions are calculated using quantum chemical methods. The results suggest that the concentrating nature of the interface leads to its being a favorable venue for radical reactions yielding complex and functionalized products that themselves could initiate further secondary chemistry and new particle formation in the atmospheric environment.</p>
[1762] Kim, S., A. Guenther, B. Lefer, J. Flynn, R. Griffin, A. P. Rutter, L. Gong, and B. Karakurt Cevik, "Potential Role of Stabilized Criegee Radicals in Sulfuric Acid Production in a High Biogenic VOC Environment", Environmental Science & Technology, vol. 49, pp. 3383–3391, Mar, 2015.
Link: http://dx.doi.org/10.1021/es505793t
Abstract
<p>We present field observations made in June 2011 downwind of Dallas&ndash;Fort Worth, TX, and evaluate the role of stabilized Criegee radicals (sCIs) in gaseous sulfuric acid (H2SO4) production. Zero-dimensional model calculations show that sCI from biogenic volatile organic compounds composed the majority of the sCIs. The main uncertainty associated with an evaluation of H2SO4 production from the sCI reaction channel is the lack of experimentally determined reaction rates for sCIs formed from isoprene ozonolysis with SO2 along with systematic discrepancies in experimentally derived reaction rates between other sCIs and SO2 and water vapor. In general, the maximum of H2SO4 production from the sCI channel is found in the late afternoon as ozone increases toward the late afternoon. The sCI channel, however, contributes minor H2SO4 production compared with the conventional OH channel in the mid-day. Finally, the production and the loss rates of H2SO4 are compared. The application of the recommended mass accommodation coefficient causes significant overestimation of H2SO4 loss rates compared with H2SO4 production rates. However, the application of a lower experimental value for the mass accommodation coefficient provides good agreement between the loss and production rates of H2SO4. The results suggest that the recommended coefficient for the H2O surface may not be suitable for this relatively dry environment.</p>
[1714] Bergamaschi, M.., F.. Biasioli, L.. Cappellin, A.. Cecchinato, C.. Cipolat-Gotet, A.. Cornu, F.. Gasperi, B.. Martin, and G.. Bittante, "Proton transfer reaction time-of-flight mass spectrometry: A high-throughput and innovative method to study the influence of dairy system and cow characteristics on the volatile compound fingerprint of cheeses.", J Dairy Sci, vol. 98, pp. 8414–8427, Dec, 2015.
Link: http://dx.doi.org/10.3168/jds.2015-9803
Abstract
<p>The aim of this work was to study the effect of dairy system and individual cow-related factors on the volatile fingerprint of a large number of individual model cheeses analyzed by proton transfer reaction time-of-flight mass spectrometry (PTR-ToF-MS). A total of 1,075 model cheeses were produced using milk samples collected from individual Brown Swiss cows reared in 72 herds located in mountainous areas of Trento province (Italy). The herds belonged to 5 main dairy systems ranging from traditional to modern and the cows presented different daily milk yields (24.6&plusmn;7.9kg &times; d(-1)), stages of lactation (199&plusmn;138 d in milk), and parities (2.7&plusmn;1.8). The PTR-ToF-MS revealed 619 peaks, of which the 240 most intense were analyzed, and 61 of these were tentatively attributed to relevant volatile organic compounds on the basis of their fragmentation patterns and data from the literature. Principal component analysis was used to convert the multiple responses characterizing the PTR-ToF-MS spectra into 5 synthetic variables representing 62% of the total information. These principal components were related to groups of volatile compounds tentatively attributed to different peaks and used to investigate the relationship of the volatile compound profile obtained by PTR-ToF-MS to animal and farm characteristics. Lactation stage is related to 4 principal components which brought together 52.9% of the total variance and 57.9% of the area of analyzed peaks. In particular, 2 principal components were positively related to peaks tentatively attributed to aldehydes and ketones and negatively related to alcohols, esters, and acids, which displayed a linear increase during lactation. The second principal component was affected by dairy system; it was higher in the modern system in which cows received total mixed rations. The third principal component was positively related to daily milk production. In summary, we report the first application of this innovative, high-throughput technique to study the effects of dairy system and individual animal factors on volatile organic compounds of model cheeses. Individual cheesemaking procedures together with this spectrometric technique open new avenues for genetic selection of dairy species with respect to both milk and cheese quality.</p>
[1639] Romano, A., V. Capozzi, G. Spano, and F. Biasioli, "Proton transfer reaction-mass spectrometry: online and rapid determination of volatile organic compounds of microbial origin.", Appl Microbiol Biotechnol, vol. 99, pp. 3787–3795, May, 2015.
Link: http://dx.doi.org/10.1007/s00253-015-6528-y
Abstract
<p>Analytical tools for the identification and quantification of volatile organic compounds (VOCs) produced by microbial cultures have countless applications in an industrial and research context which are still not fully exploited. The various techniques for VOC analysis generally arise from the application of different scientific and technological philosophies, favoring either sample throughput or chemical information. Proton transfer reaction-mass spectrometry (PTR-MS) represents a valid compromise between the two aforementioned approaches, providing rapid and direct measurements along with highly informative analytical output. The present paper reviews the main applications of PTR-MS in the microbiological field, comprising food, environmental, and medical applications.</p>
[1626] Warneke, C.., P.. Veres, S.. M. Murphy, J.. Soltis, R.. A. Field, M.. G. Graus, A.. Koss, S.-M.. Li, R.. Li, B.. Yuan, et al., "PTR-QMS versus PTR-TOF comparison in a region with oil and natural gas extraction industry in the Uintah Basin in 2013", Atmos. Meas. Tech., vol. 8, pp. 411–420, 2015.
Link: http://dx.doi.org/10.5194/amt-8-411-2015
Abstract
Here we compare volatile organic compound (VOC) measurements using a standard proton-transfer-reaction quadrupole mass spectrometer (PTR-QMS) with a new proton-transfer-reaction time of flight mass spectrometer (PTR-TOF) during the Uintah Basin Winter Ozone Study 2013 (UBWOS2013) field experiment in an oil and gas field in the Uintah Basin, Utah. The PTR-QMS uses a quadrupole, which is a mass filter that lets one mass to charge ratio pass at a time, whereas the PTR-TOF uses a time of flight mass spectrometer, which takes full mass spectra with typical 0.1 s–1 min integrated acquisition times. The sensitivity of the PTR-QMS in units of counts per ppbv (parts per billion by volume) is about a factor of 10–35 times larger than the PTR-TOF, when only one VOC is measured. The sensitivity of the PTR-TOF is mass dependent because of the mass discrimination caused by the sampling duty cycle in the orthogonal-acceleration region of the TOF. For example, the PTR-QMS on mass 33 (methanol) is 35 times more sensitive than the PTR-TOF and for masses above 120 amu less than 10 times more. If more than 10–35 compounds are measured with PTR-QMS, the sampling time per ion decreases and the PTR-TOF has higher signals per unit measuring time for most masses. For UBWOS2013 the PTR-QMS measured 34 masses in 37 s and on that timescale the PTR-TOF is more sensitive for all masses. The high mass resolution of the TOF allows for the measurements of compounds that cannot be separately detected with the PTR-QMS, such as oxidation products from alkanes and cycloalkanes emitted by oil and gas extraction. PTR-TOF masses do not have to be preselected, allowing for identification of unanticipated compounds. The measured mixing ratios of the two instruments agreed very well (R2 ≥ 0.92 and within 20%) for all compounds and masses monitored with the PTR-QMS.
[1702] Masi, E., A. Romani, C. Pandolfi, D. Heimler, and S. Mancuso, "PTR-TOF-MS analysis of volatile compounds in olive fruits.", J Sci Food Agric, vol. 95, pp. 1428–1434, May, 2015.
Link: http://dx.doi.org/10.1002/jsfa.6837
Abstract
<p>Volatile compounds of Cellina di Nardò and Ogliarola Barese, two typical Italian olive varieties, have been characterised at different ripening stages. Proton transfer reaction-time-of-flight-mass spectrometry (PTR-TOF-MS) was used for the first time on these fruits with the aim of characterising the volatile profile and, in the case of Ogliarola, the changes which may occur during the maturation process.PTR-TOF-MS does not involve any sample pre-treatment, and allows high-resolution measurements, large spectra and small fragmentation of the volatiles. Therefore it allows both compound identification and data statistical treatments. In the present work, about 40 compounds that contribute to the discrimination between samples of the two varieties have been identified.Three groups of compounds were identified: (1) compounds that are typical of mature fruits of Ogliarola, (2) compounds that tend to decrease during the change from green to mature fruits, and (3) compounds that increase during the maturation process.</p>
[1707] Zein, A. El, C. Coeur, E. Obeid, A. Lauraguais, and T. Fagniez, "Reaction Kinetics of Catechol (1,2-Benzenediol) and Guaiacol (2-Methoxyphenol) with Ozone.", J Phys Chem A, vol. 119, pp. 6759–6765, Jul, 2015.
Link: http://dx.doi.org/10.1021/acs.jpca.5b00174
Abstract
<p>The kinetic reactions of 1,2-benzenediol (catechol) and 2-methoxyphenol (guaiacol) with ozone were studied in a simulation chamber (8 m(3)) under dark conditions. The rate coefficients were measured at 294 &plusmn; 2 K, atmospheric pressure and dry conditions (relative humidity, RH &lt; 1%), except for 1,2-benzenediol where they were also measured as a function of relative humidity (RH = 1-80%). The concentrations of organic compounds were followed by a PTR-ToF-MS for a continuous monitoring of gas-phase species. The O3 rate coefficients were obtained using both the pseudo-first-order and relative rate methods. The values (in cm(3) molecule(-1) s(-1)) determined for catechol and guaiacol under dry conditions are (13.5 &plusmn; 1.1) &times; 10(-18) and (0.40 &plusmn; 0.31) &times; 10(-18), respectively. The rate coefficient of catechol was found to be independent of RH below 20% and above 60%, whereas for RH between 20% and 60% it decreases with increasing RH. The determined rate coefficients have been used to evaluate the atmospheric lifetime of each compound with respect to O3. To our knowledge, this study represents the first determination of the ozone rate coefficient with guaiacol and is also the first kinetic investigation for the influence of the relative humidity on the oxygenated aromatic ozonolysis.</p>
[1576] Lanza, M., J. W. Acton, P. Sulzer, K. Breiev, S. Juerschik, A. Jordan, E. Hartungen, G. Hanel, L. Maerk, T. D. Maerk, et al., "Selective reagent ionisation-time of flight-mass spectrometry: a rapid technology for the novel analysis of blends of new psychoactive substances", Journal of Mass Spectrometry, vol. 50, pp. 427–431, 2015.
Link: http://dx.doi.org/10.1002/jms.3514
Abstract
In this study we demonstrate the potential of selective reagent ionisation-time of flight-mass spectrometry for the rapid and selective identification of a popular new psychoactive substance blend called ‘synthacaine’, a mixture that is supposed to imitate the sensory and intoxicating effects of cocaine. Reactions with H3O+ result in protonated parent molecules which can be tentatively assigned to benzocaine and methiopropamine. However, by comparing the product ion branching ratios obtained at two reduced electric field values (90 and 170 Td) for two reagent ions (H3O+ and NO+) to those of the pure chemicals, we show that identification is possible with a much higher level of confidence then when relying solely on the m/z of protonated parent molecules. A rapid and highly selective analytical identification of the constituents of a recreational drug is particularly crucial to medical personnel for the prompt medical treatment of overdoses, toxic effects or allergic reactions. Copyright © 2015 John Wiley & Sons, Ltd.
[1638] Lanza, M., J. W Acton, P. Sulzer, K. Breiev, S. Jürschik, A. Jordan, E. Hartungen, G. Hanel, L. Märk, T. D. Märk, et al., "Selective reagent ionisation-time of flight-mass spectrometry: a rapid technology for the novel analysis of blends of new psychoactive substances.", J Mass Spectrom, vol. 50, pp. 427–431, Feb, 2015.
Link: http://dx.doi.org/10.1002/jms.3514
Abstract
<p>In this study we demonstrate the potential of selective reagent ionisation-time of flight-mass spectrometry for the rapid and selective identification of a popular new psychoactive substance blend called &#39;synthacaine&#39;, a mixture that is supposed to imitate the sensory and intoxicating effects of cocaine. Reactions with H3O(+) result in protonated parent molecules which can be tentatively assigned to benzocaine and methiopropamine. However, by comparing the product ion branching ratios obtained at two reduced electric field values (90 and 170 Td) for two reagent ions (H3O(+) and NO(+)) to those of the pure chemicals, we show that identification is possible with a much higher level of confidence then when relying solely on the m/z of protonated parent molecules. A rapid and highly selective analytical identification of the constituents of a recreational drug is particularly crucial to medical personnel for the prompt medical treatment of overdoses, toxic effects or allergic reactions.</p>
[1732] Mancuso, S., C. Taiti, N. Bazihizina, C. Costa, P. Menesatti, L. Giagnoni, M. Arenella, P. Nannipieri, and G. Renella, "Soil volatile analysis by proton transfer reaction-time of flight mass spectrometry (PTR-TOF-{MS})", Applied Soil Ecology, vol. 86, pp. 182¬タモ191, Feb, 2015.
Link: http://dx.doi.org/10.1016/j.apsoil.2014.10.018
Abstract
<p>We analyzed the volatile organic compounds (VOCs) emitted from different soils by using the PTR-MS-TOF technique under laboratory conditions and compared them with soil chemical biochemical activities. The emitted VOCs were related to soil microbial biomass, soil respiration and some soil enzyme activities so as to evaluate if size and activity of soil microbial communities influenced the soil VOCs profiles. Our results showed that the emitted VOCs discriminated between soils with different properties and management, and differences in the VOCs emission profiles were likely related to the active metabolic pathways in the microbial communities of the three studied soil. Our results also showed that some soil enzyme activities such as β-glucosidase and arylsulfatase were possibly involved in the release of compounds fueling microbial metabolic pathways leading to the production of specific VOCs. It was concluded that the PTR-MS-TOF technique is suitable for analyze VOCs emission from soil and that studies comparing soil enzyme activities and soil volatile profiles can reveal the origin of VOCs and give further insights on microbial activity and soil functionality.</p>
[1793] Sun, K., K. Cady-Pereira, D. J. Miller, L. Tao, M. A. Zondlo, J. B. Nowak, JA. Neuman, T. Mikoviny, M. Müller, A. Wisthaler, et al., "Validation of TES ammonia observations at the single pixel scale in the San Joaquin Valley during DISCOVER-AQ", Journal of Geophysical Research: Atmospheres, vol. 120, pp. 5140–5154, 2015.
Link: http://onlinelibrary.wiley.com/doi/10.1002/2014JD022846/full
Abstract
<p>Ammonia measurements from a vehicle-based, mobile open-path sensor and those from aircraft were compared with Tropospheric Emission Spectrometer (TES) NH3 columns at the pixel scale during the NASA Deriving Information on Surface conditions from Column and Vertically Resolved Observations Relevant to Air Quality field experiment. Spatial and temporal mismatches were reduced by having the mobile laboratory sample in the same areas as the TES footprints. To examine how large heterogeneities in the NH3 surface mixing ratios may affect validation, a detailed spatial survey was performed within a single TES footprint around the overpass time. The TES total NH3 column above a single footprint showed excellent agreement with the in situ total column constructed from surface measurements with a difference of 2% (within the combined measurement uncertainties). The comparison was then extended to a TES transect of nine footprints where aircraft data (5&ndash;80&thinsp;ppbv) were available in a narrow spatiotemporal window (&lt;10&thinsp;km, &lt;1&thinsp;h). The TES total NH3 columns above the nine footprints agreed to within 6% of the in situ total columns derived from the aircraft-based measurements. Finally, to examine how TES captures surface spatial gradients at the interpixel scale, ground-based, mobile measurements were performed directly underneath a TES transect, covering nine footprints within &plusmn;1.5&thinsp;h of the overpass. The TES total columns were strongly correlated (R2&thinsp;=&thinsp;0.82) with the median NH3 mixing ratios measured at the surface. These results provide the first in situ validation of the TES total NH3 column product, and the methodology is applicable to other satellite observations of short-lived species at the pixel scale.</p>
[1651] R. del Rio, F., M.E.. OHara, A.. Holt, P.. Pemberton, T.. Shah, T.. Whitehouse, and C.A.. Mayhew, "Volatile Biomarkers in Breath Associated With Liver Cirrhosis - Comparisons of Pre- and Post-liver Transplant Breath Samples", EBioMedicine, Jul, 2015.
Link: http://dx.doi.org/10.1016/j.ebiom.2015.07.027
Abstract
Background: The burden of liver disease in the UK has risen dramatically and there is a need for improved diagnostics. Aims: To determine which breath volatiles are associated with the cirrhotic liver and hence diagnostically useful. Methods: A two-stage biomarker discovery procedure was used. Alveolar breath samples of 31 patients with cirrhosis and 30 healthy controls were mass spectrometrically analysed and compared (stage 1). 12 of these patients had their breath analysed after liver transplant (stage 2). Five patients were followed longitudinally as in-patients in the posttransplant period. Results: Seven volatileswere elevated in the breath of patients versus controls. Of these, five showed statistically significant decrease post-transplant: limonene, methanol, 2-pentanone, 2-butanone and carbon disulfide. On an individual basis limonene has the best diagnostic capability (the area under a receiver operating characteristic curve (AUROC) is 0.91), but this is improved by combining methanol, 2-pentanone and limonene (AUROC curve 0.95). Following transplant, limonene shows wash-out characteristics. Conclusions: Limonene,methanol and 2-pentanone are breathmarkers for a cirrhotic liver. This study raises the potential to investigate these volatiles asmarkers for early-stage liver disease. Bymonitoring the wash-out of limonene following transplant, graft liver function can be non-invasively assessed.

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Selected PTR-MS related Reviews

F. Biasioli, C. Yeretzian, F. Gasperi, T. D. Märk: PTR-MS monitoring of VOCs and BVOCs in food science and technology, Trends in Analytical Chemistry 30 (7) (2011).
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J. de Gouw, C. Warneke, T. Karl, G. Eerdekens, C. van der Veen, R. Fall: Measurement of Volatile Organic Compounds in the Earth's Atmosphere using Proton-Transfer-Reaction Mass Spectrometry. Mass Spectrometry Reviews, 26 (2007), 223-257.
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W. Lindinger, A. Hansel, A. Jordan: Proton-transfer-reaction mass spectrometry (PTR–MS): on-line monitoring of volatile organic compounds at pptv levels, Chem. Soc. Rev. 27 (1998), 347-375.
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Lists with PTR-MS relevant publications of the University of Innsbruck can be found here: Atmospheric and indoor air chemistry, IMR, Environmental Physics and Nano-Bio-Physics

 

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