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Found 775 results
Title [ Year(Asc)]
2014
[1529] Platt, S.M.., I.E.. Haddad, S.M.. Pieber, R.-J.. Huang, A.A.. Zardini, M.. Clairotte, R.. Suarez-Bertoa, P.. Barmet, L.. Pfaffenberger, R.. Wolf, et al., "Two-stroke scooters are a dominant source of air pollution in many cities", Nature Communications, vol. 5, May, 2014.
Link: http://dx.doi.org/10.1038/ncomms4749
Abstract
<p>Fossil fuel-powered vehicles emit significant particulate matter, for example, black carbon and primary organic aerosol, and produce secondary organic aerosol. Here we quantify secondary organic aerosol production from two-stroke scooters. Cars and trucks, particularly diesel vehicles, are thought to be the main vehicular pollution sources. This needs re-thinking, as we show that elevated particulate matter levels can be a consequence of &lsquo;asymmetric pollution&rsquo; from two-stroke scooters, vehicles that constitute a small fraction of the fleet, but can dominate urban vehicular pollution through organic aerosol and aromatic emission factors up to thousands of times higher than from other vehicle classes. Further, we demonstrate that oxidation processes producing secondary organic aerosol from vehicle exhaust also form potentially toxic &lsquo;reactive oxygen species&rsquo;.</p>
[1562] Farneti, B., N. Busatto, I. Khomenko, L. Cappellin, S. Gutierrez, F. Spinelli, R. Velasco, F. Biasioli, G. Costa, and F. Costa, "Untargeted metabolomics investigation of volatile compounds involved in the development of apple superficial scald by PTR-ToF-MS", Metabolomics, Jul, 2014.
Link: http://dx.doi.org/10.1007/s11306-014-0696-0
Abstract
<p>The superficial scald is an important physiological disorder affecting apple fruit during postharvest storage. To date, the accumulation, and further oxidation, of α-farnesene was considered as the most probable cause for the development of this physiopathy. In order to perform a more broad investigation, a PTR-ToF&ndash;MS (proton transfer reaction&mdash;time of flight&mdash;mass spectrometry) was employed to monitor the volatile organic compounds (VOCs) production along with the progression of this disorder in fruit of &ldquo;Granny Smith&rdquo;, an apple variety known to be highly susceptible to scald. The untargeted metabolite investigation was performed on both skin and pulp, as well as comparing control versus treated tissues with 1-methylcyclopropene (1-MCP), an ethylene competitor widely used to prevent the development of this phenomenon. The rapid and non-destructive analysis of the VOC array carried out by PTR-ToF&ndash;MS identified three specific groups of metabolites in the skin, among which the 6-methyl-5-hepten-2-one (MHO) resulted significantly associated with the development of the superficial scald in apple. The results proposed in this work suggest the use of this novel equipment for an on-line monitoring of the VOCs released by the apple during the postharvest storage, as well as to use MHO as a possible biochemical marker for an early detection of the superficial scald symptoms.</p>
[1600] Kreuzwieser, J., U. Scheerer, J. Kruse, T. Burzlaff, A. Honsel, S. Alfarraj, P. Georgiev, JÖRG-PETER. SCHNITZLER, A. Ghirardo, I. Kreuzer, et al., "The Venus flytrap attracts insects by the release of volatile organic compounds.", J Exp Bot, vol. 65, pp. 755–766, Feb, 2014.
Link: http://dx.doi.org/10.1093/jxb/ert455
Abstract
<p>Does Dionaea muscipula, the Venus flytrap, use a particular mechanism to attract animal prey? This question was raised by Charles Darwin 140 years ago, but it remains unanswered. This study tested the hypothesis that Dionaea releases volatile organic compounds (VOCs) to allure prey insects. For this purpose, olfactory choice bioassays were performed to elucidate if Dionaea attracts Drosophila melanogaster. The VOCs emitted by the plant were further analysed by GC-MS and proton transfer reaction-mass spectrometry (PTR-MS). The bioassays documented that Drosophila was strongly attracted by the carnivorous plant. Over 60 VOCs, including terpenes, benzenoids, and aliphatics, were emitted by Dionaea, predominantly in the light. This work further tested whether attraction of animal prey is affected by the nutritional status of the plant. For this purpose, Dionaea plants were fed with insect biomass to improve plant N status. However, although such feeding altered the VOC emission pattern by reducing terpene release, the attraction of Drosophila was not affected. From these results it is concluded that Dionaea attracts insects on the basis of food smell mimicry because the scent released has strong similarity to the bouquet of fruits and plant flowers. Such a volatile blend is emitted to attract insects searching for food to visit the deadly capture organ of the Venus flytrap.</p>
[1619] Kumar, V.., and V.. Sinha, "VOC-OHM: A new technique for rapid measurements of ambient total OH reactivity and volatile organic compounds using a single proton transfer reaction mass spectrometer", International Journal of Mass Spectrometry, vol. 374, pp. 55–63, Dec, 2014.
Link: http://dx.doi.org/10.1016/j.ijms.2014.10.012
Abstract
Measurements of total hydroxyl radical (OH) reactivity and volatile organic compounds (VOC) are necessary for improving our understanding of reactive emissions and atmospheric oxidation in air pollution and atmospheric chemistry studies. Proton transfer reaction mass spectrometers (PTR-MS) can measure ambient VOCs and the total ambient OH reactivity. However, till date this has always required deployment of two PTR-MS instruments, wherein one instrument measures ambient VOCs and the other instrument measures the total OH reactivity using the comparative reactivity method (CRM). Due to material (e.g. power, space) or financial constraints, deploying two PTR-MS instruments is not always possible and yet it is desirable to quantify both VOCs and OH reactivity. Here, we present a novel hyphenated technique christened VOC-OHM (for Volatile Organic Compounds–OH reactivity Measurement) that enables rapid ambient measurements of both VOCs and total OH reactivity using a single PTR-MS. The technique can provide more specificity for identification of compounds using a PTR-QMS through an estimate of the rate coefficient of the major isobaric contributor with the hydroxyl radical as shown in the case of m/z = 69 for isoprene and furan, which are nominal isobars but have rate coefficients that differ by one order of magnitude. It also demonstrates a new safer and portable substitute for pressurized zero air bottles that have been required thus far in CRM OH reactivity deployments. VOC–OHM successfully couples the typical VOC and CRM experimental set ups without undermining the PTR-MS's ability to measure either parameter. The design of the VOC–OHM system, its validation, optimization and results of field tests are described in detail. The VOC–OHM system measures the ambient VOCs and OH reactivity every hour for ∼20 min durations each, with an ambient data gap of ∼13 min in between. Thus rapid temporal changes in the ambient chemical composition and reactivity are easily quantified. The sampling periods and VOC speciation achieved using VOC–OHM can be customized depending on user preferences, providing more options for the majority of users possessing a single PTR-MS.
[1546] Romano, A., L. Fischer, J. Herbig, H. Campbell-Sills, J. Coulon, P. Lucas, L. Cappellin, and F. Biasioli, "Wine analysis by FastGC proton-transfer reaction-time-of-flight-mass spectrometry", International Journal of Mass Spectrometry, vol. 369, pp. 81 - 86, 2014.
Link: http://www.sciencedirect.com/science/article/pii/S1387380614002127
Abstract
<p>Abstract Proton transfer reaction-mass spectrometry (PTR-MS) has successfully been applied to a wide variety of food matrices, nevertheless the reports about the use of PTR-MS in the analysis of alcoholic beverages remain anecdotal. Indeed, due to the presence of ethanol in the sample, PTR-MS can only be employed after dilution of the headspace or at the expense of radical changes in the operational conditions. In the present research work, PTR-ToF-MS was coupled to a prototype FastGC system allowing for a rapid (90&nbsp;s) chromatographic separation of the sample headspace prior to PTR-MS analysis. The system was tested on red wine: the FastGC step allowed to rule out the effect of ethanol, eluted from the column during the first 8&nbsp;s, allowing PTR-MS analysis to be carried out without changing the ionization conditions. Eight French red wines were submitted to analysis and could be separated on the basis of the respective grape variety and region of origin. In comparison to the results obtained by direct injection, FastGC provided additional information, thanks to a less drastic dilution of the sample and due to the chromatographic separation of isomers. This was achieved without increasing duration and complexity of the analysis.</p>
2013
[1470] Biasioli, F., "10 years PTR-MS at FEM: from sensory analysis to omics", CONFERENCE SERIES, 1, 2013.
Link: http://www.ionicon.com/sites/default/files/uploads/doc/contributions_ptr_ms_Conference_6.pdf
[Park2013] Park, J-H.., A.. H. Goldstein, J.. Timkovsky, S.. Fares, R.. Weber, J.. Karlik, and R.. Holzinger, "Active atmosphere-ecosystem exchange of the vast majority of detected volatile organic compounds.", Science, vol. 341, no. 6146: Department of Environmental Science, Policy, and Management, University of California at Berkeley, Berkeley, CA 94720, USA., pp. 643–647, Aug, 2013.
Link: http://nature.berkeley.edu/ahg/pubs/Park%20et%20al%20Science%202013.pdf
Abstract
<p>Numerous volatile organic compounds (VOCs) exist in Earth&#39;s atmosphere, most of which originate from biogenic emissions. Despite VOCs&#39; critical role in tropospheric chemistry, studies for evaluating their atmosphere-ecosystem exchange (emission and deposition) have been limited to a few dominant compounds owing to a lack of appropriate measurement techniques. Using a high-mass resolution proton transfer reaction-time of flight-mass spectrometer and an absolute value eddy-covariance method, we directly measured 186 organic ions with net deposition, and 494 that have bidirectional flux. This observation of active atmosphere-ecosystem exchange of the vast majority of detected VOCs poses a challenge to current emission, air quality, and global climate models, which do not account for this extremely large range of compounds. This observation also provides new insight for understanding the atmospheric VOC budget.</p>
[1455] Schmidberger, T., and R. Huber, "Advanced off-gas measurement using proton transfer reaction mass spectrometry to predict cell culture parameters", BMC Proceedings, vol. 7, pp. P14, 2013.
Link: http://www.biomedcentral.com/1753-6561/7/S6/P14
Abstract
<p>Mass spectrometry is a well-known technology to detect O2 and CO2 in the off-gas of cell culture fermentations. In contrast to classical mass spectrometers, the proton transfer reaction mass spectrometer (PTR MS) enables the noninvasive analysis of a broad spectrum of volatile organic compounds (VOCs) in real time. The thereby applied soft ionization technology generates spectra of less fragmentation and facilitates their interpretation. This gave us the possibility to identify process relevant compounds in the bioreactor off-gas stream in addition to O2 and CO2. In our study the PTR-MS technology was applied for the first time to monitor volatile organic compounds (VOC) and to predict cell culture parameters in an industrial mammalian cell culture process.</p>
[1514] Karl, T.., P.. K. Misztal, H.. H. Jonsson, S.. Shertz, A.. H. Goldstein, and A.. B. Guenther, "Airborne Flux Measurements of BVOCs above Californian Oak Forests: Experimental Investigation of Surface and Entrainment Fluxes, OH Densities, and Damköhler Numbers", J. Atmos. Sci., vol. 70, pp. 3277–3287, Oct, 2013.
Link: http://nature.berkeley.edu/ahg/pubs/Karl et al 2013 JAS.pdf
Abstract
<p>Airborne flux measurements of isoprene were performed over the Californian oak belts surrounding the Central Valley. The authors demonstrate for the first time 1) the feasibility of airborne eddy covariance measurements of reactive biogenic volatile organic compounds; 2) the effect of chemistry on the vertical transport of reactive species, such as isoprene; and 3) the applicability of wavelet analysis to estimate regional fluxes of biogenic volatile organic compounds. These flux measurements demonstrate that instrumentation operating at slower response times (e.g., 1&ndash;5 s) can still be used to determine eddy covariance fluxes in the mixed layer above land, where typical length scales of 0.5&ndash;3 km were observed. Flux divergence of isoprene measured in the planetary boundary layer (PBL) is indicative of OH densities in the range of 4&ndash;7 &times; 106 molecules per cubic centimeter and allows extrapolation of airborne fluxes to the surface with Damköhler numbers (ratio between the mixing time scale and the chemical time scale) in the range of 0.3&ndash;0.9. Most of the isoprene is oxidized in the PBL with entrainment fluxes of about 10% compared to the corresponding surface fluxes. Entrainment velocities of 1&ndash;10 cm s&minus;1 were measured. The authors present implications for parameterizing PBL schemes of reactive species in regional and global models.</p>
[1443] Veres, P. R., P. Faber, F. Drewnick, J. Lelieveld, and J. Williams, "Anthropogenic sources of VOC in a football stadium: Assessing Human Emissions in the Atmosphere", Atmospheric Environment, 2013.
Link: http://www.sciencedirect.com/science/article/pii/S1352231013004494
Abstract
<p>Measurements of gas-phase volatile organic compounds (VOCs), aerosol composition, carbon dioxide (CO2), and ozone (O3) were made inside Coface Arena in Mainz, Germany (49&deg;59&prime;3&Prime;N, 8&deg;13&prime;27&Prime;E) during a football match on April 20 2012. The VOC measurements were performed with a proton-transfer-reaction time-of-flight mass spectrometer (PTR-TOF-MS). Observed VOCs could be classified into several distinct source categories including (1) human respiration/breath, (2) ozonolysis of skin oils, and (3) cigarette smoke/combustion. In this work, we present a detailed discussion on the scale and potential impacts of VOCs emitted as a result of these sources and their contributions on local and larger scales. Human emissions of VOCs have a negligible contribution to the global atmospheric budget (&sim;1% or less) for all those quantified in this study. However, fluxes as high as 0.02 g m&minus;2 h&minus;1 and 2 &times; 10&minus;4 g m&minus;2 h&minus;1, for ethanol and acetone respectively are observed, suggesting the potential for significant impact on local air chemistry and perhaps regional scales. This study suggests that even in outdoor environments, situations exist where VOCs emitted as a result of human presence and activity are an important component of local air chemistry.</p>
[Schmidberger2013] Schmidberger, T.., R.. Gutmann, and R.. Huber, "Application of PTR-MS in mammalian cell culture", 6th International PTR-MS Conference on Proton Transfer Reaction Mass Spectrometry and Its Applications, pp. 39, 2013.
Link: http://www.ionicon.com/sites/default/files/uploads/doc/contributions_ptr_ms_Conference_6.pdf
Abstract
Mass spectrometry is a well-known technology to detect O2 and CO2 in the off-gas of cell culture fermentations. In contrast to classical spectrometers, the proton transfer reaction mass spectrometer (PTR-MS) applies a very soft ionization strategy and therefore the spectra show less fragments and are easier to interpret. In our study we applied the PTR-MS technology to monitor volatile organic compounds (VOC) in mammalian cell culture processes. Interesting masses were identified and correlations between PTR-MS data and off-line parameters will be presented.
[Sulzer2013a] Sulzer, P., B. Agarwal, S. Juerschik, M. Lanza, A. Jordan, E. Hartungen, G. Hanel, L. Märk, T. D. Märk, R. González-Méndez, et al., "Applications of switching reagent ions in proton transfer reaction mass spectrometric instruments for the improved selectivity of explosive compounds", International Journal of Mass Spectrometry, vol. 354–355: Elsevier, 2013.
Link: http://www.sciencedirect.com/science/article/pii/S1387380613001735
Abstract
<p>Here we demonstrate the use of a switchable reagent ion proton transfer reaction mass spectrometry (SRI-PTR-MS) instrument to improve the instrument&#39;s selectivity for the detection of the explosive compounds 2,4,6 trinitrotoluene (TNT), 1,3,5 trinitrobenzene (TNB), pentaerythritol tetranitrate (PETN), and cyclotrimethylenetrinitramine (RDX). Selectivity is improved owing to the production of different product ions resulting from changes in the reagent ion-molecule chemistry. To be of use as an analytical tool for homeland security applications, it is important that the reagent ions (and hence product ions) can be rapidly changed (within seconds) from H3O+ to another dominant ion species if the technology is to be acceptable. This paper presents measurements that show how it is possible to rapidly switch the reagent ion from H3O+ to either O2+ or NO+ to enhance selectivity for the detection of the four explosives named above. That switching reagent ions can be done quickly results from the fact that the recombination energies of O2+ and NO+ are less than the ionisation potential of H2O, i.e. charge transfer cannot occur which otherwise would result in ions that can react efficiently with water (e.g. H2O+ + H2O &rarr; H3O+ + OH) leading to H3O+ becoming the dominant reagent ion. Reaction processes observed are non-dissociative charge transfer (O2+ with TNT and TNB), dissociative charge transfer (O2+ with TNT) and adduct formation (NO+ with PETN and RDX). O2+ is found to be unreactive with PETN and RDX, and under the conditions operating in the reaction region of the PTR-MS only a low signal associated with NO+&middot;TNT was observed. No NO+&middot;TNB was detected.</p>
[1497] Yang, M.., P.. D. Nightingale, R.. Beale, P.. S. Liss, B.. Blomquist, and C.. Fairall, "Atmospheric deposition of methanol over the Atlantic Ocean", Proceedings of the National Academy of Sciences, vol. 110, pp. 20034–20039, Dec, 2013.
Link: http://dx.doi.org/10.1073/pnas.1317840110
Abstract
<p>In the troposphere, methanol (CH3OH) is present ubiquitously and second in abundance among organic gases after methane. In the surface ocean, methanol represents a supply of energy and carbon for marine microbes. Here we report direct measurements of air&ndash;sea methanol transfer along a &sim;10,000-km north&ndash;south transect of the Atlantic. The flux of methanol was consistently from the atmosphere to the ocean. Constrained by the aerodynamic limit and measured rate of air&ndash;sea sensible heat exchange, methanol transfer resembles a one-way depositional process, which suggests dissolved methanol concentrations near the water surface that are lower than what were measured at &sim;5 m depth, for reasons currently unknown. We estimate the global oceanic uptake of methanol and examine the lifetimes of this compound in the lower atmosphere and upper ocean with respect to gas exchange. We also constrain the molecular diffusional resistance above the ocean surface&mdash;an important term for improving air&ndash;sea gas exchange models.</p>
[Karl2013] Karl, T., A. Hansel, L. Cappellin, L. Kaser, I. Herdlinger-Blatt, and W. Jud, "BVOC measurements based on NO+ ionization", CONFERENCE SERIES, pp. 84, 2013.
Link: http://www.ionicon.com/sites/default/files/uploads/doc/contributions_ptr_ms_Conference_6.pdf
[Kohl2013] Kohl, I., J. Herbig, J. Dunkl, A. Hansel, M. Daniaux, and M. Hubalek, "Chapter 6 - Smokers Breath as Seen by Proton-Transfer-Reaction Time-of-Flight Mass Spectrometry (PTR-TOF-MS)", Volatile Biomarkers, Boston, Elsevier, pp. 89 - 116, 2013.
Link: http://www.sciencedirect.com/science/article/pii/B9780444626134000064
Abstract
Abstract Proton-transfer-reaction time-of-flight mass spectrometry has been employed in a 12&#xa0;months breath gas analysis study to describe the breath composition of 19 cigarette smoking and 53 non-smoking women. The most prevalent constituents were acetone (1.8&#xa0;ppmv), methanol (310&#xa0;ppbv), isoprene (280&#xa0;ppbv), ethanol (130&#xa0;ppbv), acetaldehyde (90&#xa0;ppbv) and acetic acid (70&#xa0;ppbv). Smokers showed the largest signal increase in acetonitrile (ratio smoker/non-smoker 29), benzene (ratio 11), 2-methylfuran (ratio 8) and 2,5-dimethylfuran (ratio 7). Calibration gas measurements allowed the instruments performance regarding precision and accuracy of ion mass-to-charge, m/z, and concentration accuracy measurement to be assessed. The standard deviation of the concentration measurements was 14% or smaller (with the exception of ethanol) with no trend in this variation of sensitivity. The limit of detection (LOD) lay in the sub ppbv range, based on an integration time of 2&#xa0;s. The m/z accuracy was better than 0.0016 (or less than 29&#xa0;ppm of the ion mass) throughout the study. The standard deviation of the measured m/z was less than 0.0025 and the coefficient of variation was less than 29&#xa0;ppm. Keywords PTR-TOF-MS, Smokers’ breath, Breath volatile organic compounds, \{VOCs\}
[1668] Sekimoto, K., S. Inomata, H. Tanimoto, A. Fushimi, Y. Fujitani, K. Sato, and H. Yamada, "Characterization of nitromethane emission from automotive exhaust", Atmospheric Environment, vol. 81, pp. 523–531, Dec, 2013.
Link: http://dx.doi.org/10.1016/j.atmosenv.2013.09.031
Abstract
<p>We carried out time-resolved experiments using a proton-transfer-reaction mass spectrometer and a chassis dynamometer to characterize nitromethane emission from automotive exhaust. We performed experiments under both cold-start and hot-start conditions, and determined the dependence of nitromethane emission on vehicle velocity and acceleration/deceleration as well as the effect of various types of exhaust-gas treatment system. We found that nitromethane emission was much lower from a gasoline car than from diesel trucks, probably due to the reduction function of the three-way catalyst of the gasoline car. Diesel trucks without a NOx reduction catalyst using hydrocarbons produced high emissions of nitromethane, with emission factors generally increasing with increasing acceleration at low vehicle velocities.</p>
[1513] Holzinger, R.., A.. H. Goldstein, P.. L. Hayes, J.. L. Jimenez, and J.. Timkovsky, "Chemical evolution of organic aerosol in Los Angeles during the CalNex 2010 study", Atmospheric Chemistry and Physics, vol. 13, pp. 10125–10141, Oct, 2013.
Link: http://dx.doi.org/10.5194/acp-13-10125-2013
Abstract
<p>During the CalNex study (15 May to 16 June 2010) a large suite of instruments was operated at the Los Angeles area ground supersite to characterize the sources and atmospheric processing of atmospheric pollution. The thermal-desorption proton-transfer-reaction mass-spectrometer (TD-PTR-MS) was deployed to an urban area for the first time and detected 691 organic ions in aerosol samples, the mean total concentration of which was estimated as 3.3 μg m&minus;3. Based on comparison to total organic aerosol (OA) measurements, we estimate that approximately 50% of the OA mass at this site was directly measured by the TD-PTR-MS. Based on correlations with aerosol mass spectrometer (AMS) OA components, the ions were grouped to represent hydrocarbon-like OA (HOA), local OA (LOA), semi-volatile oxygenated OA (SV-OOA), and low volatility oxygenated OA (LV-OOA). Mass spectra and thermograms of the ion groups are mostly consistent with the assumed sources and/or photochemical origin of the OA components. The mass spectra of ions representing the primary components HOA and LOA included the highest m/z, consistent with their higher resistance to thermal decomposition, and they were volatilized at lower temperatures (&nbsp; 150 &deg;C). Photochemical ageing weakens C-C bond strengths (also resulting in chemical fragmentation), and produces species of lower volatility (through the addition of functional groups). Accordingly the mass spectra of ions representing the oxidized OA components (SV-OOA, and LV-OOA) lack the highest masses and they are volatilized at higher temperatures (250&ndash;300 &deg;C). Chemical parameters like mean carbon number (nC), mean carbon oxidation state (OSC), and the atomic ratios O / C and H / C of the ion groups are consistent with the expected sources and photochemical processing of the aerosol components. Our data suggest that chemical fragmentation gains importance over functionalization as photochemical age of OA increases. Surprisingly, the photochemical age of OA decreases during the daytime hours, demonstrating the importance of rapid production of new (photochemically young) SV-OOA during daytime. The PTR detects higher organic N concentrations than the AMS, the reasons for which are not well understood and cannot be explained by known artifacts related to PTR or the AMS. The median atomic N / C ratio (6.4%) of the ion group representing LV-OOA is a factor 2 higher than N / C of any other ion group. This suggests a multiphase chemical source involving ammonium ions is contributing to LV-OOA.</p>
[1590] Déléris, I., A. Saint-Eve, E. Sémon, H. Guillemin, E. Guichard, I. Souchon, and J-L. { Le Quéré}, "Comparison of direct mass spectrometry methods for the on-line analysis of volatile compounds in foods.", J Mass Spectrom, vol. 48, pp. 594–607, May, 2013.
Link: http://dx.doi.org/10.1002/jms.3199
Abstract
<p>For the on-line monitoring of flavour compound release, atmospheric pressure chemical ionization (APCI) and proton transfer reaction (PTR) combined to mass spectrometry (MS) are the most often used ionization technologies. APCI-MS was questioned for the quantification of volatiles in complex mixtures, but direct comparisons of APCI and PTR techniques applied on the same samples remain scarce. The aim of this work was to compare the potentialities of both techniques for the study of in vitro and in vivo flavour release. Aroma release from flavoured aqueous solutions (in vitro measurements in Teflon bags and glass vials) or flavoured candies (in vivo measurements on six panellists) was studied using APCI- and PTR-MS. Very similar results were obtained with both techniques. Their sensitivities, expressed as limit of detection of 2,5-dimethylpyrazine, were found equivalent at 12&thinsp;ng/l air. Analyses of Teflon bag headspace revealed a poor repeatability and important ionization competitions with both APCI- and PTR-MS, particularly between an ester and a secondary alcohol. These phenomena were attributed to dependency on moisture content, gas/liquid volume ratio, proton affinities and product ion distribution, together with inherent drawbacks of Teflon bags (adsorption, condensation of water and polar molecules). Concerning the analyses of vial headspace and in vivo analyses, similar results were obtained with both techniques, revealing no competition phenomena. This study highlighted the equivalent performances of APCI-MS and PTR-MS for in vitro and in vivo flavour release investigations and provided useful data on the problematic use of sample bags for headspace analyses.</p>
[1699] Trefz, P., M. Schmidt, P. Oertel, J. Obermeier, B. Brock, S. Kamysek, J. Dunkl, R. Zimmermann, J. K. Schubert, and W. Miekisch, "Continuous real time breath gas monitoring in the clinical environment by proton-transfer-reaction-time-of-flight-mass spectrometry.", Anal Chem, vol. 85, pp. 10321–10329, Nov, 2013.
Link: http://dx.doi.org/10.1021/ac402298v
Abstract
<p>Analysis of volatile organic compounds (VOCs) in breath holds great promise for noninvasive diagnostic applications. However, concentrations of VOCs in breath may change quickly, and actual and previous uptakes of exogenous substances, especially in the clinical environment, represent crucial issues. We therefore adapted proton-transfer-reaction-time-of-flight-mass spectrometry for real time breath analysis in the clinical environment. For reasons of medical safety, a 6 m long heated silcosteel transfer line connected to a sterile mouth piece was used for breath sampling from spontaneously breathing volunteers and mechanically ventilated patients. A time resolution of 200 ms was applied. Breath from mechanically ventilated patients was analyzed immediately after cardiac surgery. Breath from 32 members of staff was analyzed in the post anesthetic care unit (PACU). In parallel, room air was measured continuously over 7 days. Detection limits for breath-resolved real time measurements were in the high pptV/low ppbV range. Assignment of signals to alveolar or inspiratory phases was done automatically by a matlab-based algorithm. Quickly and abruptly occurring changes of patients&#39; clinical status could be monitored in terms of breath-to-breath variations of VOC (e.g. isoprene) concentrations. In the PACU, room air concentrations mirrored occupancy. Exhaled concentrations of sevoflurane strongly depended on background concentrations in all participants. In combination with an optimized inlet system, the high time and mass resolution of PTR-ToF-MS provides optimal conditions to trace quick changes of breath VOC profiles and to assess effects from the clinical environment.</p>
[1698] Righettoni, M.., A.. Schmid, A.. Amann, and S.. E. Pratsinis, "Correlations between blood glucose and breath components from portable gas sensors and PTR-TOF-MS.", J Breath Res, vol. 7, pp. 037110, Sep, 2013.
Link: http://dx.doi.org/10.1088/1752-7155/7/3/037110
Abstract
<p>Acetone is one of the most abundant volatile compounds in the human breath and might be important for monitoring diabetic patients. Here, a portable acetone sensor consisting of flame-made, nanostructured, Si-doped WO3&nbsp;sensing films was used to analyse the end tidal fraction of the breath (collected in Tedlar bags) from eight healthy volunteers after overnight fasting (morning) and after lunch (afternoon). After breath sampling, the gaseous components were also analysed by proton transfer reaction time-of-flight mass spectrometry (PTR-TOF-MS), and each person&#39;s blood glucose level was measured. The portable sensor accurately detected the presence of acetone with fast response/recovery times (&lt;12&nbsp;s) and a high signal-to-noise ratio. Statistical analysis of the relationship between the PTR-TOF-MS measurements of breath gases (e.g., acetone, isoprene, ethanol and methanol), sensor response and the blood glucose level was performed for both sampling periods. The best correlations were found after overnight fasting (morning): in particular, between blood glucose level and breath acetone (Pearson&#39;s 0.98 and Spearman&#39;s 0.93). Whereas the portable sensor response correlated best with the blood glucose (Pearson&#39;s 0.96 and Spearman&#39;s 0.81) and breath acetone (Pearson&#39;s 0.92 and Spearman&#39;s 0.69).</p>
[Pollien2013] Pollien, P., F. Viton, and B. Le Révérend, "Coupling of in-mouth physical phenomena with nosespace analysis; a new method for understanding aroma release and perception from liquids", CONFERENCE SERIES, pp. 209, 2013.
Link: http://www.ionicon.com/sites/default/files/uploads/doc/contributions_ptr_ms_Conference_6.pdf
[Juerschik2013] Juerschik, S., M. Lanza, P. Sulzer, B. Agarwal, E. Hartungen, A. Edtbauer, S. Feil, A. Jordan, G. Hanel, CA. Mayhew, et al., "Designer Drugs and Trace Explosives Detection with the Help of Very Recent Advancements in Proton-Transfer-Reaction Mass Spectrometry (PTR-MS)", CONFERENCE SERIES, pp. 182, 2013.
Link: http://www.ionicon.com/sites/default/files/uploads/doc/contributions_ptr_ms_Conference_6.pdf
[Sulzer2013] Sulzer, P., T. Kassebacher, S. Juerschik, M. Lanza, E. Hartungen, A. Jordan, A. Edtbauer, S. Feil, G. Hanel, J1. L. S Maerk, et al., "Detection of Toxic Industrial Compounds (TIC) with Proton-Transfer-Reaction Mass Spectrometry (PTR-MS) for a real-life monitoring scenario", CONFERENCE SERIES, pp. 196, 2013.
Link: http://www.ionicon.com/sites/default/files/uploads/doc/contributions_ptr_ms_Conference_6.pdf
[Wisthaler2013] Wisthaler, A., JH. Crawford, S. Haidacher, G. Hanel, E. Hartungen, A. Jordan, L. Märk, T. Mikoviny, M. Müller, P. Mutschlechner, et al., "Development of a compact PTR-ToF-MS for Suborbital Research on the Earth's Atmospheric Composition", CONFERENCE SERIES, pp. 96, 2013.
Link: http://www.ionicon.com/sites/default/files/uploads/doc/contributions_ptr_ms_Conference_6.pdf#page=97
[Oezdestan2013] Özdestan, Ö., S. M. van Ruth, M. Alewijn, A. Koot, A. Romano, L. Cappellin, and F. Biasioli, "Differentiation of specialty coffees by proton transfer reaction-mass spectrometry", Food Research International: Elsevier, 2013.
Link: http://www.sciencedirect.com/science/article/pii/S0963996913003025
Abstract
In the coffee sector a diversity of certifications is available, with the most well-known being organic and fair trade. Intrinsic markers of products may help to assure the authenticity of food products and complement administrative controls. In the present study 110 market coffees with special production traits were characterized by high sensitivity proton transfer reaction mass spectrometry (HS PTR-MS) and volatiles were tentatively identified by PTR-time of flight MS. Espresso coffees, Kopi Luwak coffee and organic coffees could be distinguished by their profiles of volatile compounds with the help of chemometrics. A PLS-DA classification model was estimated to classify the organic and regular coffees by their HS PTR-MS mass spectra. Cross validation showed correct prediction of 42 out of the 43 (98%) organic coffee samples and 63 out of the 67 (95%) regular coffee samples. Therefore, the presented strategy is a promising approach to rapid organic coffee authentication.

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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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