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Scientific Articles - PTR-MS Bibliography

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Found 767 results
Title [ Year(Asc)]
2014
[1610] Tres, A., S. P. Heenan, and S. { van Ruth}, "Authentication of dried distilled grain with solubles (DDGS) by fatty acid and volatile profiling.", Lebenson Wiss Technol, vol. 59, pp. 215–221, Nov, 2014.
Link: http://dx.doi.org/10.1016/j.lwt.2014.05.044
Abstract
<p>Demand for ethanol substituted fuels from the utilisation of cereal based biofuel has resulted in an over production of dried distillers grains with solubles (DDGS) that are now readily available on the animal feed market. With this rapid emerging availability comes potential variability in the nutritional value of DDGS and possible risks of feed contaminants. Subsequently, the authentication and traceability of alternative animal feed sources is of high priority. In this study and as part of the EU research project &quot;Quality and Safety of Feeds and Food for Europe (QSAFFE FP7-KBBE-2010-4) an attempt was made to classify the geographical origin of cereal grains used in the production of DDGS material. DDGS material of wheat and corn origin were obtained from Europe, China, and the USA. Fatty acid profiles and volatile fingerprints were assessed by gas chromatography flame ionisation (GC-FID) and rapid proton transfer reaction mass spectrometry (PTR-MS) respectively. Chemometric analysis of fatty acid profiles and volatile fingerprints allowed for promising classifications of cereals used in DDGS material by geographical and botanical origin and enabled visual representation of the data. This objective analytical approach could be adapted for routine verification of cereal grains used in the production of DDGS material.</p>
[1608] Papurello, D., A. Lanzini, P. Leone, M. Santarelli, and S. Silvestri, "Biogas from the organic fraction of municipal solid waste: dealing with contaminants for a solid oxide fuel cell energy generator.", Waste Manag, vol. 34, pp. 2047–2056, Nov, 2014.
Link: http://dx.doi.org/10.1016/j.wasman.2014.06.017
Abstract
<p>The present work investigates electricity production using a high efficiency electrochemical generator that employs as fuel a biogas from the dry anaerobic digestion of the organic fraction of municipal solid waste (OFMSW). The as-produced biogas contains several contaminants (sulfur, halogen, organic silicon and aromatic compounds) that can be harmful for the fuel cell: these were monitored via an innovative mass spectrometry technique that enables for in-line and real-time quantification. A cleaning trap with activated carbons for the removal of sulfur and other VOCs contained in the biogas was also tested and monitored by observing the different breakthrough times of studied contaminants. The electrochemical generator was a commercial Ni anode-supported planar Solid Oxide Fuel Cell (SOFC), tested for more than 300 h with a simulated biogas mixture (CH4 60 vol.%, CO2 40 vol.%), directly fed to the anode electrode. Air was added to promote the direct internal conversion of CH4 to H2 and CO via partial oxidation (POx). The initial breakthrough of H2S from the cleaning section was also simulated and tested by adding &sim;1 ppm(v) of sulfur in the anode feed; a full recovery of the fuel cell performance after 24h of sulfur exposure (&sim;1 ppm(v)) was observed upon its removal, indicating the reliable time of anode exposure to sulfur in case of exhausted guard bed.</p>
[1515] Park, J.-H.., S.. Fares, R.. Weber, and A.. H. Goldstein, "Biogenic volatile organic compound emissions during BEARPEX 2009 measured by eddy covariance and flux-gradient similarity methods", Atmospheric Chemistry and Physics, vol. 14, pp. 231–244, Jan, 2014.
Link: http://nature.berkeley.edu/ahg/pubs/Park et al-acp-14-231-2014.pdf
Abstract
<p>The Biosphere Effects on AeRosols and Photochemistry EXperiment (BEARPEX) took place in Blodgett Forest, a Ponderosa pine forest in the Sierra Nevada of California, USA, during summer 2009. We deployed a proton transfer reaction&ndash;quadrupole mass spectrometer (PTR-QMS) to measure fluxes and concentrations of biogenic volatile organic compounds (BVOCs). Eighteen ion species, including the major BVOC expected at the site, were measured sequentially at 5 heights to observe their vertical gradient from the forest floor to above the canopy. Fluxes of the 3 dominant BVOCs methanol, 2-Methyl-3-butene-2-ol (MBO), and monoterpenes were measured above the canopy by the disjunct eddy covariance (EC) method. Canopy-scale fluxes were also determined by the flux&ndash;gradient similarity method (K-theory). A universal K (Kuniv) was determined as the mean of individual K&#39;s calculated from the measured fluxes divided by vertical gradients for methanol, MBO, and monoterpenes. This Kuniv was then multiplied by the gradients of each observed ion species to compute their fluxes. The flux&ndash;gradient similarity method showed very good agreement with the disjunct EC method. Fluxes are presented for all measured species and compared to historical measurements from the same site, and used to test emission algorithms used to model fluxes at the regional scale. MBO was the dominant emission observed, followed by methanol, monoterpenes, acetone, and acetaldehyde. The flux&ndash;gradient similarity method is shown to be tenable, and we recommend its use, especially in experimental conditions when fast measurement of BVOC species is not available.</p>
[1566] Stockwell, C.. E., P.. R. Veres, J.. Williams, and R.. J. Yokelson, "Characterization of biomass burning smoke from cooking fires, peat, crop residue and other fuels with high resolution proton-transfer-reaction time-of-flight mass spectrometry", Atmospheric Chemistry and Physics Discussions, vol. 14, pp. 22163–22216, 2014.
Link: http://dx.doi.org/10.5194/acpd-14-22163-2014
Abstract
<p>We deployed a high-resolution proton-transfer-reaction time-of-flight mass spectrom-eter (PTR-TOF-MS) to measure biomass burning emissions from peat, crop-residue, cooking fires, and many other fire types during the fourth Fire Lab at Missoula Experi-ment (FLAME-4) laboratory campaign. A combination of gas standards calibrations and 5 composition sensitive, mass dependent calibration curves were applied to quantify gas-phase non-methane organic compounds (NMOCs) observed in the complex mixture of fire emissions. We used several approaches to assign best identities to most major &quot;exact masses&quot; including many high molecular mass species. Using these methods ap-proximately 80&ndash;96 % of the total NMOC mass detected by PTR-TOF-MS and FTIR was 10 positively or tentatively identified for major fuel types. We report data for many rarely measured or previously unmeasured emissions in several compound classes including aromatic hydrocarbons, phenolic compounds, and furans; many of which are suspected secondary organic aerosol precursors. A large set of new emission factors (EFs) for a range of globally significant biomass fuels is presented. Measurements show that 15 oxygenated NMOCs accounted for the largest fraction of emissions of all compound classes. In a brief study of various traditional and advanced cooking methods, the EFs for these emissions groups were greatest for open 3-stone cooking in comparison to their more advanced counterparts. Several little-studied nitrogen-containing organic compounds were detected from many fuel types that together accounted for 0.1&ndash;8.7 % 20 of the fuel nitrogen and some may play a role in new particle formation.</p>
[1465] Sinha, V., V. Kumar, and C. Sarkar, "Chemical composition of pre-monsoon air in the Indo-Gangetic Plain measured using a new PTR-MS and air quality facility: high surface ozone and strong influence of biomass burning", Atmos. Chem. Phys., vol. 14, pp. 5921-5941, 2014.
Link: http://www.atmos-chem-phys.net/14/5921/2014/acp-14-5921-2014.html
Abstract
<p>One seventh of the world population lives in the Indo&ndash;Gangetic Plain (IGP) and the fertile region sustains agricultural food crop production for much of South Asia. Yet it remains one of the most under-studied regions of the world in terms of atmospheric composition and chemistry. In particular, the emissions and chemistry of volatile organic compounds (VOCs) that form surface ozone and secondary organic aerosol through photochemical reactions involving nitrogen oxides is not well understood. In this study, ambient levels of VOCs such as methanol, acetone, acetaldehyde, acetonitrile and isoprene were measured for the first time in the IGP. A new atmospheric chemistry facility that combines India&#39;s first high sensitivity proton transfer reaction mass spectrometer, an ambient air quality station and meteorological station, was used to quantify in-situ levels of several VOCs and air pollutants in May 2012 at a suburban site in Mohali (N. W. IGP). Westerly winds arriving at high wind speeds (5&ndash;20 m s&minus;1) in the pre-monsoon season at the site, were conducive for chemical characterization of regional emission signatures. Average levels of VOCs and air pollutants in May 2012 ranged from 1.2&ndash;1.7 nmol mol&minus;1 for aromatic VOCs, 5.9&ndash;37.4 nmol mol&minus;1 for the oxygenated VOCs, 1.4 nmol mol&minus;1 for acetonitrile, 1.9 nmol mol&minus;1 for isoprene, 567 nmol mol&minus;1 for carbon monoxide, 57.8 nmol mol&minus;1 for ozone, 11.5 nmol mol&minus;1 for nitrogen oxides, 7.3 nmol mol&minus;1 for sulphur dioxide, 104 μg m&minus;3 for PM2.5 and 276 μg m&minus;3 for PM10. By analyzing the one minute in-situ data with meteorological parameters and applying chemical tracers (e.g. acetonitrile for biomass burning) and inter-VOC correlations, we were able to constrain major emission source activities on both temporal and diel scales. Wheat residue burning activity caused massive increases (&gt; 3 times of baseline values) for all the measured VOCs and primary pollutants. Other forms of biomass burning at night were also a significant source for oxygenated VOCs and isoprene (r2 with acetonitrile &ge; 0.5 for night-time data), which is remarkable in terms of atmospheric chemistry implications. Surface ozone exceeded the 8 h national ambient air quality limit of 100 μg O3 m&minus;3 on a daily basis, except for 17 May 2012, when a severe dust storm event (PM2.5 &gt; 800 μg m&minus;3; PM10 &gt; 2700 μg m&minus;3) characterized by long range transport from the west impacted the site. The novel dataset and results point to occurrence of high primary emissions of reactive VOCs. They also highlight the urgent need for establishing more comprehensive observational facilities in the IGP to constrain the spatial and seasonal variability of atmospheric chemical constituents. Such efforts will enable mechanistic level understanding of the in-situ chemical processes controlling formation of surface ozone, a necessary step for effective ozone mitigation and improvement of the regional air quality.</p>
[1605] Taiti, C., C. Costa, P. Menesatti, D. Comparini, N. Bazihizina, E. Azzarello, E. Masi, and S. Mancuso, "Class-modeling approach to PTR-TOFMS data: a peppers case study.", J Sci Food Agric, May, 2014.
Link: http://dx.doi.org/10.1002/jsfa.6761
Abstract
<p>Proton transfer reaction-mass spectrometry (PTR-MS), in its recently developed implementation based on time-of-flight mass spectrometry (PTR-TOFMS), was used to rapidly determine the volatile compounds present in fruits of Capsicum spp.We analyzed the volatile organic compounds emission profile of freshly cut chili peppers belonging to three species and 33 different cultivars. PTR-TOFMS data, analyzed with appropriate and advanced multivariate class-modeling approaches, perfectly discriminated among the three species (100% correct classification in validation set). VIP (variable importance in projection) scores were used to select the 15 most important volatile compounds in discriminating the species. The best candidates for Capsicum spp. were compounds with measured m/z of 63.027, 101.096 and 107.050, which were, respectively, tentatively identified as dimethyl sulfide, hexanal and benzaldehyde.Based on the promising results, the possibility of introducing multivariate class-modeling techniques, different from the classification approaches, in the field of volatile compounds analyses is discussed. &copy; 2014 Society of Chemical Industry.</p>
[1544] Mueller, M.., T.. Mikoviny, S.. Feil, S.. Haidacher, G.. Hanel, E.. Hartungen, A.. Jordan, L.. Maerk, P.. Mutschlechner, R.. Schottkowsky, et al., "A compact PTR-ToF-MS instrument for airborne measurements of VOCs at high spatio-temporal resolution", Atmospheric Measurement Techniques Discussions, vol. 7, pp. 5533–5558, 2014.
Link: http://www.atmos-meas-tech-discuss.net/7/5533/2014/
Abstract
<p><span style="color: rgb(0, 0, 0); font-family: Verdana, Arial, Helvetica; font-size: 12px; line-height: 20px; background-color: rgb(255, 255, 255);">Herein, we report on the development of a compact proton-transfer-reaction time-of-flight mass spectrometer for airborne measurements of volatile organic compounds (VOCs). The new instrument resolves isobaric ions with a mass resolving power (</span><i style="color: rgb(0, 0, 0); font-family: Verdana, Arial, Helvetica; font-size: 12px; line-height: 20px; background-color: rgb(255, 255, 255);">m</i><span style="color: rgb(0, 0, 0); font-family: Verdana, Arial, Helvetica; font-size: 12px; line-height: 20px; background-color: rgb(255, 255, 255);">/Δ</span><i style="color: rgb(0, 0, 0); font-family: Verdana, Arial, Helvetica; font-size: 12px; line-height: 20px; background-color: rgb(255, 255, 255);">m</i><span style="color: rgb(0, 0, 0); font-family: Verdana, Arial, Helvetica; font-size: 12px; line-height: 20px; background-color: rgb(255, 255, 255);">) of ~ 1000, provides accurate&nbsp;</span><i style="color: rgb(0, 0, 0); font-family: Verdana, Arial, Helvetica; font-size: 12px; line-height: 20px; background-color: rgb(255, 255, 255);">m/z</i><span style="color: rgb(0, 0, 0); font-family: Verdana, Arial, Helvetica; font-size: 12px; line-height: 20px; background-color: rgb(255, 255, 255);">&nbsp;measurements (Δ</span><i style="color: rgb(0, 0, 0); font-family: Verdana, Arial, Helvetica; font-size: 12px; line-height: 20px; background-color: rgb(255, 255, 255);">m</i><span style="color: rgb(0, 0, 0); font-family: Verdana, Arial, Helvetica; font-size: 12px; line-height: 20px; background-color: rgb(255, 255, 255);">&nbsp;&lt; 3 mDa), records full mass spectra at 1 Hz and thus overcomes some of the major analytical deficiencies of quadrupole-MS based airborne instruments. 1 Hz detection limits for biogenic VOCs (isoprene, α-pinene), aromatic VOCs (benzene, toluene, xylenes) and ketones (acetone, methyl ethyl ketone) range from 0.05 to 0.12 ppbV, making the instrument well-suited for fast measurements in the continental boundary layer. The instrument detects and quantifies VOCs in locally confined plumes (&lt; 1km) which improves our capability of characterizing emission sources and atmospheric processing within plumes. A deployment during the NASA 2013 DISCOVER-AQ mission generated high vertical and horizontal resolution in situ data of VOCs and ammonia for validation of satellite retrievals and chemistry transport models.</span></p>
[1790] Müller, M., T. Mikoviny, S. Feil, S. Haidacher, G. Hanel, E. Hartungen, A. Jordan, L. Märk, P. Mutschlechner, R. Schottkowsky, et al., "A compact PTR-ToF-MS instrument for airborne measurements of volatile organic compounds at high spatiotemporal resolution", Atmospheric Measurement Techniques, vol. 7, pp. 3763–3772, 2014.
Link: http://www.atmos-meas-tech.net/7/3763/2014/
Abstract
<p>Herein, we report on the development of a compact proton-transfer-reaction time-of-flight mass spectrometer (PTR-ToF-MS) for airborne measurements of volatile organic compounds (VOCs). The new instrument resolves isobaric ions with a mass resolving power (m/Δm) of &nbsp;1000, provides accurate m/z measurements (Δm &lt; 3 mDa), records full mass spectra at 1 Hz and thus overcomes some of the major analytical deficiencies of quadrupole-MS-based airborne instruments. 1 Hz detection limits for biogenic VOCs (isoprene, α total monoterpenes), aromatic VOCs (benzene, toluene, xylenes) and ketones (acetone, methyl ethyl ketone) range from 0.05 to 0.12 ppbV, making the instrument well-suited for fast measurements of abundant VOCs in the continental boundary layer. The instrument detects and quantifies VOCs in locally confined plumes (&lt; 1 km), which improves our capability of characterizing emission sources and atmospheric processing within plumes. A deployment during the NASA 2013 DISCOVER-AQ mission generated high vertical- and horizontal-resolution in situ data of VOCs and ammonia for the validation of satellite retrievals and chemistry transport models.</p>
[1701] Maja, M. M., A. Kasurinen, P. Yli-Pirilä, J. Joutsensaari, T. Klemola, T. Holopainen, and J. K. Holopainen, "Contrasting responses of silver birch VOC emissions to short- and long-term herbivory.", Tree Physiol, vol. 34, pp. 241–252, Mar, 2014.
Link: http://dx.doi.org/10.1093/treephys/tpt127
Abstract
<p>There is a need to incorporate the effects of herbivore damage into future models of plant volatile organic compound (VOC) emissions at leaf or canopy levels. Short-term (a few seconds to 48 h) changes in shoot VOC emissions of silver birch (Betula pendula Roth) in response to feeding by geometrid moths (Erannis defoliaria Hübner) were monitored online by proton transfer reaction time-of-flight mass spectrometry (PTR-TOF-MS). In addition, two separate field experiments were established to study the effects of long-term foliage herbivory (FH, 30-32 days of feeding by geometrids Agriopis aurantiaria (Clerck) and E. defoliaria in two consecutive years) and bark herbivory (BH, 21 days of feeding by the pine weevil (Hylobius abietis L.) in the first year) on shoot and rhizosphere VOC emissions of three silver birch genotypes (gt14, gt15 and Hausjärvi provenance). Online monitoring of VOCs emitted from foliage damaged by geometrid larvae showed rapid bursts of green leaf volatiles (GLVs) immediately after feeding activity, whereas terpenoid emissions had a tendency to gradually increase during the monitoring period. Long-term FH caused transient increases in total monoterpene (MT) emissions from gt14 and sesquiterpene (SQT) emissions from Hausjärvi provenance, mainly in the last experimental season. In the BH experiment, genotype effects were detected, with gt14 trees having significantly higher total MT emissions compared with other genotypes. Only MTs were detected in the rhizosphere samples of both field experiments, but their emission rates were unaffected by genotype or herbivory. The results suggest that silver birch shows a rapid VOC emission response to short-term foliage herbivory, whereas the response to long-term foliage herbivory and bark herbivory is less pronounced and variable at different time points.</p>
[1549] Karl, T., L. Kaser, and A. Turnipseed, "Eddy covariance measurements of isoprene and 232-MBO based on NO+ time-of-flight mass spectrometry", International Journal of Mass Spectrometry, vol. 365-366, pp. 15 - 19, 2014.
Link: http://www.sciencedirect.com/science/article/pii/S1387380613004272
Abstract
<div>Isoprene and 2-methyl-3-buten-2-ol (232-MBO) are the dominant</div> <div>biogenic \{VOCs\} released throughout the US, thus requiring simultaneous</div> <div>measurements. Recent measurements suggest the presence of isoprene</div> <div>in 232-MBO dominated ecosystems, however analytical difficulties</div> <div>make it problematic to detect both species independently. Based on</div> <div>a new chemical ionization scheme we use eddy covariance measurements</div> <div>to selectively measure fluxes of both species without analytical</div> <div>interference at the Manitou Experimental Forest (MEF) in Colorado.</div> <div>Our measurements show a concentration ratio between isoprene and</div> <div>232 \{MBO\} of 0.24 (ppbv/ppbv), and a flux ratio of 0.10 ([ppbv m/s]/[ppbv m/s]).</div> <div>Daytime average emission factors of isoprene and 232 \{MBO\} were</div> <div>1.4 +/- 0.3 and 16.0 +/- &nbsp;3.0 mg/m^2/h respectively.</div> <div>Both compounds exhibit light and temperature dependent fluxes. These</div> <div>findings suggest that isoprene is both locally produced and transported</div> <div>to the measurement site dominated by ponderosa pine. This makes it</div> <div>difficult to use \{MVK\} and \{MAC\} as tracers for estimating the</div> <div>photochemical age of isoprene chemistry at this site. Further our</div> <div>measurements suggest that isoprene can contribute to about 15% of</div> <div>the \{OH\} reactivity relative to 232 MBO.</div>
[1528] Zardini, A. A., S. M. Platt, M. Clairotte, I. El Haddad, B. Temime, N. Marchand, I. Jezek, L. Drinovec, G. Mocnik, J. G. Slowik, et al., "Effects of alkylate fuel on exhaust emissions and secondary aerosol formation of a 2- stroke and a 4-stroke scooter", Atmospheric Environment, Mar, 2014.
Link: http://dx.doi.org/10.1016/j.atmosenv.2014.03.024
Abstract
<p>Regulated and unregulated emissions from a 2-stroke and a 4-stroke scooter were characterized during a legislative driving cycle in a certified laboratory. Scooter exhaust was analyzed at the tailpipe, in a dilution tunnel, and partly collected in a mobile smog chamber for photochemical ageing. We present evidence that the photochemically aged exhaust from a 2-stroke and a 4-stroke scooter produces considerable amounts of secondary organic aerosol: from 1.5 to 22.0 mg/km, and from 5.5 to 6.6 mg/km, respectively. Tests were repeated after replacing the standard petrol and synthetic lube oil with an alkylate fuel (with low content of aromatic compounds) and ultra-clean lube oil (low ash forming potential). We observed emission reduction (with some exceptions) for several gaseous and particulate phase species, in particular for carbon monoxide (from 8% up to 38% and from 31% to 50%, for the 2-stroke and the 4-stroke scooters, respectively), particulate mass (from 32% up to 75% for the 2-stroke scooter), aromatic compounds (89% and 97% for the 2-stroke and the 4-stroke scooter, respectively), and secondary organic aerosol (from 87% to 100% and 99% for the 2-stroke and the 4-stroke scooters, respectively). We attribute the organic aerosol reduction to the absence of aromatics in the alkylate fuel.</p>
[1601] Liu, D., M. Marie Løkke, A. Leegaard Riis, K. Mortensen, and A. Feilberg, "Evaluation of clay aggregate biotrickling filters for treatment of gaseous emissions from intensive pig production.", J Environ Manage, vol. 136, pp. 1–8, Apr, 2014.
Link: http://dx.doi.org/10.1016/j.jenvman.2014.01.023
Abstract
<p>Treatment of ventilation air from livestock production by biological airfiltration has emerged as a cost-effective technology for reduction of emissions of odorants and ammonia. Volatile sulfur compounds from livestock production include H2S and methanethiol, which have been identified as potentially important odorants that are not removed sufficiently by biological air filters. Light-expanded clay aggregates (Leca(&reg;)) is a biotrickling filter material that contains iron oxides, which can oxidize H2S and methanethiol, and thus potentially may help to remove these two compounds in biological air filters. This study used on-line PTR-MS measurements to investigate the performances of two Leca(&reg;) biotrickling filters (abraded Leca(&reg;) filter and untreated Leca(&reg;) filter) for removal of odorants and ammonia emitted from an experimental pig house. The results indicated that the abraded Leca(&reg;) filter had a similar or slightly better capability for removing odorants than the untreated Leca(&reg;) filter. This may be due to the enlargement of the surface area by the friction process. The volatile sulfur compounds, however, were not removed efficiently by either of the two Leca(&reg;) filters. Kinetic analysis of a ventilation controlled experiment during the first period indicated that Grau second-order kinetics could be applied to analyze the removal of sulfur compounds and other odorants, whereas the Stover-Kincannon model could only be applied to analyze the removal of odorants other than sulfur compounds, partly due to the limitation of mass transfer of these compounds in the biotrickling filters. In the last measurement period, a production of dimethyl disulfide and dimethyltrisulfide coinciding with strongly enhanced removal of methanethiol was observed for the untreated filter. This was assumed to be enhanced by an incidence of low local air velocity in the filter and indicated involvement of iron-catalyzed reactions in the removal of sulfur compounds.</p>
[1526] Gloess, A. N., A. Vietri, F. Wieland, S. Smrke, B. Schönbächler, J. A. Sanchez Lopez, S. Petrozzi, S. Bongers, T. Koziorowski, and C. Yeretzian, "Evidence of different flavour formation dynamics by roasting coffee from different origins: On-line analysis with PTR-ToF-{MS}", International Journal of Mass Spectrometry, Feb, 2014.
Link: http://www.sciencedirect.com/science/article/pii/S1387380614000657
Abstract
<p>Coffees from different origins were roasted to different roast degrees and along varying time temperature roasting profiles. The formation of volatile organic compounds (VOCs) during roasting was analyzed on-line by proton-transfer-reaction time-of-flight mass-spectrometry (PTR-ToF-MS). Coffee samples were Coffea arabica from Colombia, Guatemala (Antigua La Ceiba), Ethiopia (Yirga Cheffe, Djimmah) and Coffea canephora var. robusta from Indonesia (Malangsari). The roasting profiles ranged from high temperature short time (HTST) to low temperature long time (LTLT) roasting, and from medium to dark roast degree. The release dynamics of the on-line monitored VOCs differed for the different coffees and showed a strong modulation with the time&ndash;temperature roasting profile. While for Guatemalan coffee the formation of VOCs started relatively early in the roasting process, the VOC formation started much later in the case of Yirga Cheffe and Malangsari. Off-line analysis of the coffee brew augmented the measurements. These included headspace solid phase micro extraction gas chromatography mass spectrometry (HS SPME GC/MS), content of total solids, chlorogenic acids, caffeine, total polyphenols (Folin Ciocalteu), organic acids (ion chromatography), titratable acidity and pH. Some general trends, irrespective of the coffee origin, were observed, such as an increase in pH when going from an HTST to an LTLT profile or from a medium to dark roast degree. Furthermore, a decrease of total headspace intensity was observed from an HTST to an LTLT roasting profile. In general, the changes of the time temperature roasting profiles and/or the roast degree influenced the intensity of the respective coffee constituents as well as their relative composition differently for different coffee origins.</p>
[1607] Borduas, N., G. { da Silva}, J. G. Murphy, and J. P. D. Abbatt, "Experimental and Theoretical Understanding of the Gas Phase Oxidation of Atmospheric Amides with OH Radicals: Kinetics, Products, and Mechanisms.", J Phys Chem A, Jul, 2014.
Link: http://dx.doi.org/10.1021/jp503759f
Abstract
<p>Atmospheric amides have primary and secondary sources and are present in ambient air at low pptv levels. To better assess the fate of amides in the atmosphere, the room temperature (298 &plusmn; 3 K) rate coefficients of five different amides with OH radicals were determined in a 1 m(3) smog chamber using online proton-transfer-reaction mass spectrometry (PTR-MS). Formamide, the simplest amide, has a rate coefficient of (4.44 &plusmn; 0.46) &times; 10(-12) cm(3) molec(-1) s(-1) against OH, translating to an atmospheric lifetime of &sim;1 day. N-methylformamide, N-methylacetamide and propanamide, alkyl versions of formamide, have rate coefficients of (10.1 &plusmn; 0.6) &times; 10(-12), (5.42 &plusmn; 0.19) &times; 10(-12), and (1.78 &plusmn; 0.43) &times; 10(-12) cm(3) molec(-1) s(-1), respectively. Acetamide was also investigated, but due to its slow oxidation kinetics, we report a range of (0.4-1.1) &times; 10(-12) cm(3) molec(-1) s(-1) for its rate coefficient with OH radicals. Oxidation products were monitored and quantified and their time traces were fitted using a simple kinetic box model. To further probe the mechanism, ab initio calculations are used to identify the initial radical products of the amide reactions with OH. Our results indicate that N-H abstractions are negligible in all cases, in contrast to what is predicted by structure-activity relationships. Instead, the reactions proceed via C-H abstraction from alkyl groups and from formyl C(O)-H bonds when available. The latter process leads to radicals that can readily react with O2 to form isocyanates, explaining the detection of toxic compounds such as isocyanic acid (HNCO) and methyl isocyanate (CH3NCO). These contaminants of significant interest are primary oxidation products in the photochemical oxidation of formamide and N-methylformamide, respectively.</p>
[1611] Granato, D., A. Koot, and S. M. { van Ruth}, "Geographical provenancing of purple grape juices from different farming systems by proton transfer reaction mass spectrometry using supervised statistical techniques.", J Sci Food Agric, Nov, 2014.
Link: http://dx.doi.org/10.1002/jsfa.7001
Abstract
<p>Organic, biodynamic and conventional purple grape juices (PGJ; n = 79) produced in Brazil and Europe were characterized by volatile organic compounds (m/z 20-160) measured by proton transfer reaction mass spectrometry (PTR-MS), and classification models were built using supervised statistical techniques.k-Nearest neighbours and soft independent modelling of class analogy (SIMCA) models discriminated adequately the Brazilian from European PGJ (overall efficiency of 81% and 87%, respectively). Partial least squares discriminant analysis (PLSDA) classified 100% European and 96% Brazilian PGJ. Similarly, when samples were grouped as either conventional or organic/biodynamic, the PLSDA model classified 81% conventional and 83% organic/biodynamic juices. Intraregional PLSDA models (juices produced in the same region&nbsp;-&nbsp;either Europe or Brazil) were developed and were deemed accurate in discriminating Brazilian organic from conventional PGJ (81% efficiency), as well as European conventional from organic/biodynamic PGJ (94% efficiency).PGJ from Brazil and Europe, as well as conventional and organic/biodynamic PGJ, were distinguished with high efficiency, but no statistical model was able to differentiate organic and biodynamic grape juices. These data support the hypothesis that no clear distinction between organic and biodynamic grape juices can be made with respect to volatile organic compounds. &copy; 2014 Society of Chemical Industry.</p>
[1642] W Acton, J., M. Lanza, B. Agarwal, S. Jürschik, P. Sulzer, K. Breiev, A. Jordan, E. Hartungen, G. Hanel, L. Märk, et al., "Headspace analysis of new psychoactive substances using a Selective Reagent Ionisation-Time of Flight-Mass Spectrometer.", Int J Mass Spectrom, vol. 360, pp. 28–38, Mar, 2014.
Link: http://dx.doi.org/10.1016/j.ijms.2013.12.009
Abstract
<p>The rapid expansion in the number and use of new psychoactive substances presents a significant analytical challenge because highly sensitive instrumentation capable of detecting a broad range of chemical compounds in real-time with a low rate of false positives is required. A Selective Reagent Ionisation-Time of Flight-Mass Spectrometry (SRI-ToF-MS) instrument is capable of meeting all of these requirements. With its high mass resolution (up to m/Δm of 8000), the application of variations in reduced electric field strength (E/N) and use of different reagent ions, the ambiguity of a nominal (monoisotopic) m/z is reduced and hence the identification of chemicals in a complex chemical environment with a high level of confidence is enabled. In this study we report the use of a SRI-ToF-MS instrument to investigate the reactions of H3O(+), O2 (+), NO(+) and Kr(+) with 10 readily available (at the time of purchase) new psychoactive substances, namely 4-fluoroamphetamine, methiopropamine, ethcathinone, 4-methylethcathinone, N-ethylbuphedrone, ethylphenidate, 5-MeO-DALT, dimethocaine, 5-(2-aminopropyl)benzofuran and nitracaine. In particular, the dependence of product ion branching ratios on the reduced electric field strength for all reagent ions was investigated and is reported here. The results reported represent a significant amount of new data which will be of use for the development of drug detection techniques suitable for real world scenarios.</p>
[1599] Blasioli, S., E. Biondi, D. Samudrala, F. Spinelli, A. Cellini, A. Bertaccini, S. M. Cristescu, and I. Braschi, "Identification of volatile markers in potato brown rot and ring rot by combined GC-MS and PTR-MS techniques: study on in vitro and in vivo samples.", J Agric Food Chem, vol. 62, pp. 337–347, Jan, 2014.
Link: http://dx.doi.org/10.1021/jf403436t
Abstract
<p>Ralstonia solanacearum (Rs) and Clavibacter michiganensis subsp. sepedonicus (Cms) are the bacterial causal agents of potato brown and ring rot, respectively, and are included in the A2 list of quarantine pathogens in Europe. Identification by GC-MS analysis of volatile organic compounds from Rs or Cms cultured on different nutrient media was performed. GC-MS and PTR-MS analysis were carried out also on unwounded potato tubers infected with the same pathogens. Infected tubers were produced by experimental inoculations of the plants. In in vitro experiments, Rs or Cms emitted volatile compounds, part of which were specific disease markers of potato (2-propanol and 3-methylbutanoic acid), mainly originating from bacterial metabolism (i.e., amino acid degradation, carbohydrate and fatty acid oxidation). In potato tubers, pathogen metabolism modified the volatile compound pattern emitted from healthy samples. Both bacteria seem to accelerate metabolic processes ongoing in potatoes and, in the case of Rs, disease markers (1-hepten-3-ol, 3,6-dimethyl-3-octanone, 3-ethyl-3-methylpentane, 1-chloroctane, and benzothiazole) were identified.</p>
[Papurello2014] Papurello, D., E. Schuhfried, A. Lanzini, A. Romano, L. Cappellin, T. D. Märk, S. Silvestri, and F. Biasioli, "Influence of co-vapors on biogas filtration for fuel cells monitored with PTR-MS (Proton Transfer Reaction-Mass Spectrometry)", Fuel processing technology, vol. 118: Elsevier, pp. 133–140, 2014.
Link: http://www.sciencedirect.com/science/article/pii/S0378382013002725
[1705] Sánchez-López, J. A., R. Zimmermann, and C. Yeretzian, "Insight into the time-resolved extraction of aroma compounds during espresso coffee preparation: online monitoring by PTR-ToF-MS.", Anal Chem, vol. 86, pp. 11696–11704, Dec, 2014.
Link: http://dx.doi.org/10.1021/ac502992k
Abstract
<p>Using proton-transfer-reaction time-of-flight mass-spectrometry (PTR-ToF-MS), we investigated the extraction dynamic of 95 ion traces in real time (time resolution = 1 s) during espresso coffee preparation. Fifty-two of these ions were tentatively identified. This was achieved by online sampling of the volatile organic compounds (VOCs) in close vicinity to the coffee flow, at the exit of the extraction hose of the espresso machine (single serve capsules). Ten replicates of six different single serve coffee types were extracted to a final weight between 20-120 g, according to the recommended cup size of the respective coffee capsule (Ristretto, Espresso, and Lungo), and analyzed. The results revealed considerable differences in the extraction kinetics between compounds, which led to a fast evolution of the volatile profiles in the extract flow and consequently to an evolution of the final aroma balance in the cup. Besides exploring the time-resolved extraction dynamics of VOCs, the dynamic data also allowed the coffees types (capsules) to be distinguished from one another. Both hierarchical cluster analysis (HCA) and principal component analysis (PCA) showed full separation between the coffees types. The methodology developed provides a fast and simple means of studying the extraction dynamics of VOCs and differentiating between different coffee types.</p>
[1603] Beauchamp, J., M. Scheibe, T. Hummel, and A. Buettner, "Intranasal odorant concentrations in relation to sniff behavior.", Chem Biodivers, vol. 11, pp. 619–638, Apr, 2014.
Link: http://dx.doi.org/10.1002/cbdv.201300320
Abstract
<p>Knowledge on how odorants are transported through the nasal cavity to the olfactory epithelium is limited. One facet of this is how the sniffing behavior affects the abundance of odorants transferred to the olfactory cleft and in turn influences odor perception. A novel system that couples an online mass spectrometer with an odorant pulse delivery olfactometer was employed to characterize intranasal odorant concentrations of butane-2,3-dione (or butanedione, commonly known as diacetyl) at the interior naris and the olfactory cleft. Volunteers (n=12) were asked to perform different modes of sniffing in relation to the sniff intensity that were categorized as &#39;normal&#39;, &#39;rapid&#39; and &#39;forced&#39;. The highest concentrations of butanedione at both positions in the nose were observed during normal sniffing, with the lowest concentrations correlating with periods of forced sniffs. This corresponded to the panelists&#39; ratings that normal sniffing elicited the highest odor intensities. These feasibility assessments pave the way for more in-depth analyses with a variety of odorants of different chemical classes at various intranasal positions, to investigate the passage and uptake of odorants within the nasal cavity.</p>
[1604] Riva, M., R. M. Healy, P-M. Flaud, E. Perraudin, J. C. Wenger, and E. Villenave, "Kinetics of the gas-phase reactions of chlorine atoms with naphthalene, acenaphthene, and acenaphthylene.", J Phys Chem A, vol. 118, pp. 3535–3540, May, 2014.
Link: http://dx.doi.org/10.1021/jp5009434
Abstract
<p>Reactions of polycyclic aromatic hydrocarbons (PAHs) with chlorine atoms may occur in specific areas such as coastal regions and the marine boundary layer. In this work, rate constants for the gas-phase reactions of naphthalene, acenaphthene, and acenaphthylene with chlorine atoms have been measured using the relative rate technique. Experiments were performed at room temperature (293 &plusmn; 2 K) and atmospheric pressure in an atmospheric simulation chamber using a proton-transfer reaction mass spectrometer (PTR-MS) to monitor the concentrations of PAHs and the reference compounds (acetone, methanol, 1,3,5-trimethylbenzene, and isoprene) as a function of time. The rate constants obtained in this work were (in units of cm(3) molecule(-1) s(-1)) (4.22 &plusmn; 0.46) &times; 10(-12), (3.01 &plusmn; 0.82) &times; 10(-10), and (4.69 &plusmn; 0.82) &times; 10(-10) for naphthalene, acenaphthene, and acenaphthylene, respectively. These are the first measurements of the rate constants for gas-phase reactions of Cl atoms with acenaphthene and acenaphthylene. The rate constant determined in this study for the reaction of naphthalene with Cl atoms is not in agreement with the only other previously reported value in the literature. The results are used to assess the potential role of chlorine atom reactions in the atmospheric oxidation of PAHs.</p>
[1564] Smith, D., P. Spanel, J. Herbig, and J. Beauchamp, "Mass spectrometry for real-time quantitative breath analysis", Journal of Breath Research, vol. 8, pp. 027101, Mar, 2014.
Link: http://dx.doi.org/10.1088/1752-7155/8/2/027101
Abstract
<p>Breath analysis research is being successfully pursued using a variety of analytical methods, prominent amongst which are gas chromatography with mass spectrometry, GC-MS, ion mobility spectrometry, IMS, and the fast flow and flow-drift tube techniques called selected ion flow tube mass spectrometry, SIFT-MS, and proton transfer reaction mass spectrometry, PTR-MS. In this paper the case is made for real-time breath analysis by obviating sample collection into bags or onto traps that can suffer from partial degradation of breath metabolites or the introduction of impurities. Real-time analysis of a broad range of volatile chemical compounds can be best achieved using SIFT-MS and PTR-MS, which are sufficiently sensitive and rapid to allow the simultaneous analyses of several trace gas metabolites in single breath exhalations. The basic principles and the ion chemistry that underpin these two analytical techniques are briefly described and the differences between them, including their respective strengths and weaknesses, are revealed, especially with reference to the analysis of the complex matrix that is exhaled breath. A recent innovation is described that combines time-of-flight mass spectrometry with the proton transfer flow-drift tube reactor, PTR-TOFMS, which provides greater resolution in the analytical mass spectrometer and allows separation of protonated isobaric molecules. Examples are presented of some recent data that well illustrate the quality and real-time feature of SIFT-MS and PTR-MS for the analysis of exhaled breath for physiological/biochemical/pharmacokinetics studies and for the identification and quantification of biomarkers relating to specific disease states.</p>
[1602] Smith, D., P. Spanel, J. Herbig, and J. Beauchamp, "Mass spectrometry for real-time quantitative breath analysis.", J Breath Res, vol. 8, pp. 027101, Jun, 2014.
Link: http://dx.doi.org/10.1088/1752-7155/8/2/027101
Abstract
<p>Breath analysis research is being successfully pursued using a variety of analytical methods, prominent amongst which are gas chromatography with mass spectrometry, GC-MS, ion mobility spectrometry, IMS, and the fast flow and flow-drift tube techniques called selected ion flow tube mass spectrometry, SIFT-MS, and proton transfer reaction mass spectrometry, PTR-MS. In this paper the case is made for real-time breath analysis by obviating sample collection into bags or onto traps that can suffer from partial degradation of breath metabolites or the introduction of impurities. Real-time analysis of a broad range of volatile chemical compounds can be best achieved using SIFT-MS and PTR-MS, which are sufficiently sensitive and rapid to allow the simultaneous analyses of several trace gas metabolites in single breath exhalations. The basic principles and the ion chemistry that underpin these two analytical techniques are briefly described and the differences between them, including their respective strengths and weaknesses, are revealed, especially with reference to the analysis of the complex matrix that is exhaled breath. A recent innovation is described that combines time-of-flight mass spectrometry with the proton transfer flow-drift tube reactor, PTR-TOFMS, which provides greater resolution in the analytical mass spectrometer and allows separation of protonated isobaric molecules. Examples are presented of some recent data that well illustrate the quality and real-time feature of SIFT-MS and PTR-MS for the analysis of exhaled breath for physiological/biochemical/pharmacokinetics studies and for the identification and quantification of biomarkers relating to specific disease states.</p>
[1596] Tanimoto, H., S. Kameyama, T. Iwata, S. Inomata, and Y. Omori, "Measurement of air-sea exchange of dimethyl sulfide and acetone by PTR-MS coupled with gradient flux technique.", Environ Sci Technol, vol. 48, pp. 526–533, Jan, 2014.
Link: http://dx.doi.org/10.1021/es4032562
Abstract
<p>We developed a new method for in situ measurement of air-sea fluxes of multiple volatile organic compounds (VOCs) by combining proton transfer reaction-mass spectrometry (PTR-MS) and gradient flux (GF) technique. The PTR-MS/GF system was first deployed to determine the air-sea flux of VOCs in the open ocean of the western Pacific, in addition to carbon dioxide and water vapor. Each profiling at seven heights from the ocean surface up to 14 m took 7 min. In total, 34 vertical profiles of VOCs in the marine atmosphere just above the ocean surface were obtained. The vertical gradient observed was significant for dimethyl sulfide (DMS) and acetone with the best-fit curves on quasi-logarithmic relationship. The mean fluxes of DMS and acetone were 5.5 &plusmn; 1.5 and 2.7 &plusmn; 1.3 μmol/m(2)/day, respectively. These fluxes are in general in accordance with those reported by previous expeditions.</p>
[1563] Silcock, P.., M.. Alothman, E.. Zardin, S.. Heenan, C.. Siefarth, P.J.. Bremer, and J.. Beauchamp, "Microbially induced changes in the volatile constituents of fresh chilled pasteurised milk during storage", Food Packaging and Shelf Life, vol. 2, pp. 81¬タモ90, Dec, 2014.
Link: http://dx.doi.org/10.1016/j.fpsl.2014.08.002
Abstract
<p>Off-odours caused by volatile organic compounds (VOCs) are often the first indicators consumers have of milk spoilage. In this study the VOCs associated with three types (trim, 0.25&ndash;0.40% fat; lite, 1.40&ndash;1.50% fat; and full-cream, 3.18&ndash;3.28% fat) of fresh chilled pasteurised milk (FCPM), held for up to 17 days at 4.5 &plusmn; 0.5 &deg;C, were measured using proton-transfer-reaction mass spectrometry (PTR-MS). The chemical identification of VOCs in the headspace of the milk was supported by SPME&ndash;GC&ndash;MS analysis. Bacterial numbers (aerobic plate count at 25 &deg;C) in the milk were also estimated. Replicate sets of milk types treated with sodium azide (NaN3) to inhibit microbial activity were investigated. The relationship between microbial numbers and VOCs was not linear; rather the concentrations of VOCs only started to change after a threshold number of bacteria ranging from 106&ndash;108 CFU mL&minus;1 was reached. This combined approach provided new insights on the effect of microbial growth on FCPM shelf-life.</p>

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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.
Link

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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