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Scientific Articles - PTR-MS Bibliography

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Found 89 results
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2017
[1834] Yuan, B., A. R. Koss, C. Warneke, M. Coggon, K. Sekimoto, and J. A. de Gouw, "Proton-Transfer-Reaction Mass Spectrometry: Applications in Atmospheric Sciences", Chemical Reviews, oct, 2017.
Abstract
<p>Proton-transfer-reaction mass spectrometry (PTR-MS) has been widely used to study the emissions, distributions, and chemical evolution of volatile organic compounds (VOCs) in the atmosphere. The applications of PTR-MS have greatly promoted understanding of VOC sources and their roles in air-quality issues. In the past two decades, many new mass spectrometric techniques have been applied in PTR-MS instruments, and the performance of PTR-MS has improved significantly. This Review summarizes these developments and recent applications of PTR-MS in the atmospheric sciences. We discuss the latest instrument development and characterization work on PTR-MS instruments, including the use of time-of-flight mass analyzers and new types of ion guiding interfaces. Here we review what has been learned about the specificity of different product ion signals for important atmospheric VOCs. We present some of the recent highlights of VOC research using PTR-MS including new observations in urban air, biomass-burning plumes, forested regions, oil and natural gas production regions, agricultural facilities, the marine environment, laboratory studies, and indoor air. Finally, we will summarize some further instrument developments that are aimed at improving the sensitivity and specificity of PTR-MS and extending its use to other applications in atmospheric sciences, e.g., aerosol measurements and OH reactivity measurements.</p>
[1815] Schueuermann, C.., P.. Bremer, and P.. Silcock, "{PTR}-{MS} volatile profiling of Pinot Noir wines for the investigation of differences based on vineyard site", Journal of Mass Spectrometry, jun, 2017.
2016
[1724] Capozzi, V., S. Makhoul, E. Aprea, A. Romano, L. Cappellin, A. Sanchez Jimena, G. Spano, F. Gasperi, M. Scampicchio, and F. Biasioli, "PTR-{MS} Characterization of VOCs Associated with Commercial Aromatic Bakery Yeasts of Wine and Beer Origin", Molecules, vol. 21, pp. 483, Apr, 2016.
Link: http://dx.doi.org/10.3390/molecules21040483
Abstract
<p>In light of the increasing attention towards &ldquo;green&rdquo; solutions to improve food quality, the use of aromatic-enhancing microorganisms offers the advantage to be a natural and sustainable solution that did not negatively influence the list of ingredients. In this study, we characterize, for the first time, volatile organic compounds (VOCs) associated with aromatic bakery yeasts. Three commercial bakery starter cultures, respectively formulated with three Saccharomyces cerevisiae strains, isolated from white wine, red wine, and beer, were monitored by a proton-transfer-reaction time-of-flight mass spectrometer (PTR-ToF-MS), a direct injection analytical technique for detecting volatile organic compounds with high sensitivity (VOCs). Two ethanol-related peaks (m/z 65.059 and 75.080) described qualitative differences in fermentative performances. The release of compounds associated to the peaks at m/z 89.059, m/z 103.075, and m/z 117.093, tentatively identified as acetoin and esters, are coherent with claimed flavor properties of the investigated strains. We propose these mass peaks and their related fragments as biomarkers to optimize the aromatic performances of commercial preparations and for the rapid massive screening of yeast collections.</p>
[1712] Masi, E.., C.. Taiti, D.. Heimler, P.. Vignolini, A.. Romani, and S.. Mancuso, "PTR-TOF-MS and HPLC analysis in the characterization of saffron (Crocus sativus L.) from Italy and Iran.", Food Chem, vol. 192, pp. 75–81, Feb, 2016.
Link: http://dx.doi.org/10.1016/j.foodchem.2015.06.090
Abstract
<p>Saffron samples from Italy and Iran were analyzed for their content in aroma and bioactive compounds with different analytical techniques. HPLC was used for the identification and quantification of crocins, picrocrocin, safranal and flavonoids content, while the novel proton transfer reaction time-of-flight mass spectrometer was employed for the aroma compounds analysis. Italian saffron turned out to be richer in total crocins and safranal contents. Sample characterization was performed with an unsupervised statistical approach; tests involving different numbers of parameters deriving from the two analytical techniques were performed. The results achieved showed that the best samples classification was obtained by joining the information acquired from both techniques; following such an approach, a sharper separation between Iranian and Italian samples was achieved. Finally, among the variables that most contribute to the description of variability, isophorone, safranal and picrocrocin were identified to be the most significant.</p>
2015
[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>
2014
[1703] Timkovsky, J.., P.. Gankema, R.. Pierik, and R.. Holzinger, "A plant chamber system with downstream reaction chamber to study the effects of pollution on biogenic emissions.", Environ Sci Process Impacts, vol. 16, pp. 2301–2312, 2014.
Link: http://dx.doi.org/10.1039/c4em00214h
Abstract
<p>A system of two plant chambers and a downstream reaction chamber has been set up to investigate the emission of biogenic volatile organic compounds (BVOCs) and possible effects of pollutants such as ozone. The system can be used to compare BVOC emissions from two sets of differently treated plants, or to study the photochemistry of real plant emissions under polluted conditions without exposing the plants to pollutants. The main analytical tool is a proton-transfer-reaction time-of-flight mass spectrometer (PTR-TOF-MS) which allows online monitoring of biogenic emissions and chemical degradation products. The identification of BVOCs and their oxidation products is aided by cryogenic trapping and subsequent in situ gas chromatographic analysis.</p>
[1643] Mochalski, P., K. Unterkofler, P. Spanel, D. Smith, and A. Amann, "Product ion distributions for the reactions of NO(+) with some physiologically significant aldehydes obtained using a SRI-TOF-MS instrument.", Int J Mass Spectrom, vol. 363, pp. 23–31, Apr, 2014.
Link: http://dx.doi.org/10.1016/j.ijms.2014.02.016
Abstract
<p>Product ion distributions for the reactions of NO(+) with 22 aldehydes involved in human physiology have been determined under the prevailing conditions of a selective reagent ionization time of flight mass spectrometry (SRI-TOF-MS) at an E/N in the flow/drift tube reactor of 130 Td. The chosen aldehydes were fourteen alkanals (the C2-C11 n-alkanals, 2-methyl propanal, 2-methyl butanal, 3-methyl butanal, and 2-ethyl hexanal), six alkenals (2-propenal, 2-methyl 2-propenal, 2-butenal, 3-methyl 2-butenal, 2-methyl 2-butenal, and 2-undecenal), benzaldehyde, and furfural. The product ion fragmentations patterns were determined for both dry air and humid air (3.5% absolute humidity) used as the matrix buffer/carrier gas in the drift tube of the SRI-TOF-MS instrument. Hydride ion transfer was seen to be a common ionization mechanism in all these aldehydes, thus generating (M-H)(+) ions. Small fractions of the adduct ion, NO(+)M, were also seen for some of the unsaturated alkenals, in particular 2-undecenal, and heterocyclic furfural for which the major reactive channel was non-dissociative charge transfer generating the M(+) parent ion. Almost all of the reactions resulted in partial fragmentation of the aldehyde molecules generating hydrocarbon ions; specifically, the alkanal reactions resulted in multiple product ions, whereas, the alkenals reactions produced only two or three product ions, dissociation of the nascent excited product ion occurring preferentially at the 2-position. The findings of this study are of particular importance for data interpretation in studies of aldehydes reactions employing SRI-TOF-MS in the NO(+) mode.</p>
[1551] Brilli, F., B. Gioli, P. Ciccioli, D. Zona, F. Loreto, I. A. Janssens, and R. Ceulemans, "Proton Transfer Reaction Time-of-Flight Mass Spectrometric (PTR-TOF-MS) determination of volatile organic compounds (VOCs) emitted from a biomass fire developed under stable nocturnal conditions", Atmospheric Environment, vol. 97, pp. 54 - 67, 2014.
Link: http://www.sciencedirect.com/science/article/pii/S1352231014006013
Abstract
<p>Abstract Combustion of solid and liquid fuels is the largest source of potentially toxic volatile organic compounds (VOCs), which can strongly affect health and the physical and chemical properties of the atmosphere. Among combustion processes, biomass burning is one of the largest at global scale. We used a Proton Transfer Reaction &ldquo;Time-of-Flight&rdquo; Mass Spectrometer (PTR-TOF-MS), which couples high sensitivity with high mass resolution, for real-time detection of multiple \{VOCs\} emitted by burned hay and straw in a barn located near our measuring station. We detected 132 different organic ions directly attributable to \{VOCs\} emitted from the fire. Methanol, acetaldehyde, acetone, methyl vinyl ether (MVE), acetic acid and glycolaldehyde dominated the \{VOC\} mixture composition. The time-course of the 25 most abundant VOCs, representing &sim;85% of the whole mixture of VOCs, was associated with that of carbon monoxide (CO), carbon dioxide (CO2) and methane (CH4) emissions. The strong linear relationship between the concentrations of pyrogenic \{VOC\} and of a reference species (i.e. CO) allowed us to compile a list of emission ratios (ERs) and emission factors (EFs), but values of \{ER\} (and EF) were overestimated due to the limited mixing of the gases under the stable (non-turbulent) nocturnal conditions. In addition to the 25 most abundant VOCs, chemical formula and concentrations of the residual, less abundant \{VOCs\} in the emitted mixture were also estimated by PTR-TOF-MS. Furthermore, the evolution of the complex combustion process was described on the basis of the diverse types of pyrogenic gases recorded.</p>
[1533] Sulzer, P., E. Hartungen, G. Hanel, S. Feil, K. Winkler, P. Mutschlechner, S. Haidacher, R. Schottkowsky, D. Gunsch, H. Seehauser, et al., "A Proton Transfer Reaction-Quadrupole interface Time-Of-Flight Mass Spectrometer (PTR-QiTOF): High speed due to extreme sensitivity", International Journal of Mass Spectrometry, vol. 368, pp. 1-5, 2014.
Link: http://www.sciencedirect.com/science/article/pii/S1387380614001584
Abstract
<p>Here we introduce a new prototype of a Proton Transfer Reaction-Time-Of-Flight Mass Spectrometry (PTR-TOFMS) instrument. In contrast to commercially available PTR-TOFMS devices so far, which utilize a transfer lens system, the novel prototype is equipped with a quadrupole ion guide for the highly effective transfer of ions from the drift tube to the mass spectrometer; hence we call it PTR-QiTOF, whereas &ldquo;Qi&rdquo; stands for &ldquo;Quadrupole interface&rdquo;. This new interface greatly improves the TOF mass resolution because of favorable injection conditions. Depending on whether we optimize the PTR-QiTOF to maximum sensitivity or maximum mass resolution, we get about 6900 and 10,400 m/m mass resolution, respectively, already at m/z 149 (increasing with ascending masses). Furthermore, we increase the pressure in the drift tube from typically 2.2 mbar to 3.8 mbar and the drift tube voltage from 600V to 1000 V. We directly compare the sensitivities of a commercial state-of-the-art PTR-TOFMS instrument to this &ldquo;high pressure&rdquo; PTR-QiTOF prototype and find that these modifications lead to a gain on average by a factor of 25 in terms of sensitivity with a maximum of about 4700 cps/ppbv for dichlorobenzene atm/z 147 for the PTR-QiTOF. This is (to our knowledge) the highest sensitivity ever reported for a PTR-MS instrument, regardless of the employed mass spectrometer. The increased sensitivity also has a very positive effect on the detection limit, which lies now at about 20 pptv with 100ms and 750 ppqv after 1 min integration time.Weprovide data on the linearity of the instrumental response over a concentration range of five orders of magnitude and evaluate the prototype&rsquo;s performance in a real-life test by analyzing the dynamic headspace of a minute amount of trinitrotoluene using only 2 s integration time.</p>
[1565] Makhoul, S., A. Romano, L. Cappellin, G. Spano, V. Capozzi, E. Benozzi, T. D. Märk, E. Aprea, F. Gasperi, H. El-Nakat, et al., "Proton-transfer-reaction mass spectrometry for the study of the production of volatile compounds by bakery yeast starters", Journal of Mass Spectrometry, vol. 49, pp. 850--859, Sep, 2014.
Link: http://dx.doi.org/10.1002/jms.3421
Abstract
<p>The aromatic impact of bakery yeast starters is currently receiving considerable attention. The flavor characteristics of the dough and the finished products are usually evaluated by gas chromatography and sensory analysis. The limit of both techniques resides in their low-throughput character. In the present work, proton-transfer-reaction mass spectrometry (PTR-MS), coupled to a time-of-flight mass analyzer, was employed, for the first time, to measure the volatile fractions of dough and bread, and to monitor Saccharomyces cerevisiae volatile production in a fermented food matrix. Leavening was performed on small-scale (1 g) dough samples inoculated with different commercial yeast strains. The leavened doughs were then baked, and volatile profiles were determined during leavening and after baking. The experimental setup included a multifunctional autosampler, which permitted the follow-up of the leavening process on a small scale with a typical throughput of 500 distinct data points in 16 h. The system allowed to pinpoint differences between starter yeast strains in terms of volatile emission kinetics, with repercussions on the final product (i.e. the corresponding micro-loaves). This work demonstrates the applicability of PTR-MS for the study of volatile organic compound production during bread-making, for the automated and online real-time monitoring of the leavening process, and for the characterization and selection of bakery yeast starters in view of their production of volatile compounds. Copyright &copy; 2014 John Wiley &amp; Sons, Ltd.</p>
[1609] Makhoul, S., A. Romano, L. Cappellin, G. Spano, V. Capozzi, E. Benozzi, T. D. Märk, E. Aprea, F. Gasperi, H. El-Nakat, et al., "Proton-transfer-reaction mass spectrometry for the study of the production of volatile compounds by bakery yeast starters.", J Mass Spectrom, vol. 49, pp. 850–859, Sep, 2014.
Link: http://dx.doi.org/10.1002/jms.3421
Abstract
<p>The aromatic impact of bakery yeast starters is currently receiving considerable attention. The flavor characteristics of the dough and the finished products are usually evaluated by gas chromatography and sensory analysis. The limit of both techniques resides in their low-throughput character. In the present work, proton-transfer-reaction mass spectrometry (PTR-MS), coupled to a time-of-flight mass analyzer, was employed, for the first time, to measure the volatile fractions of dough and bread, and to monitor Saccharomyces cerevisiae volatile production in a fermented food matrix. Leavening was performed on small-scale (1&thinsp;g) dough samples inoculated with different commercial yeast strains. The leavened doughs were then baked, and volatile profiles were determined during leavening and after baking. The experimental setup included a multifunctional autosampler, which permitted the follow-up of the leavening process on a small scale with a typical throughput of 500 distinct data points in 16&thinsp;h. The system allowed to pinpoint differences between starter yeast strains in terms of volatile emission kinetics, with repercussions on the final product (i.e. the corresponding micro-loaves). This work demonstrates the applicability of PTR-MS for the study of volatile organic compound production during bread-making, for the automated and online real-time monitoring of the leavening process, and for the characterization and selection of bakery yeast starters in view of their production of volatile compounds.</p>
[1704] Yener, S., A. Romano, L. Cappellin, T. D. Märk, J. {Sánchez Del Pulgar}, F. Gasperi, L. Navarini, and F. Biasioli, "PTR-ToF-MS characterisation of roasted coffees (C. arabica) from different geographic origins.", J Mass Spectrom, vol. 49, pp. 929–935, Sep, 2014.
Link: http://dx.doi.org/10.1002/jms.3455
Abstract
<p>Characterisation of coffees according to their origins is of utmost importance for commercial qualification. In this study, the aroma profiles of different batches of three monoorigin roasted Coffea arabica coffees (Brazil, Ethiopia and Guatemala) were analysed by Proton-Transfer-Reaction-Time of Flight-Mass Spectrometry (PTR-ToF-MS). The measurements were performed with the aid of a multipurpose autosampler. Unsupervised and supervised multivariate data analysis techniques were applied in order to visualise data and classify the coffees according to origin. Significant differences were found in volatile profiles of coffees. Principal component analysis allowed visualising a separation of the three coffees according to geographic origin and further partial least square regression-discriminant analysis classification showed completely correct predictions. Remarkably, the samples of one batch could be used as training set to predict geographic origin of the samples of the other batch, suggesting the possibility to predict further batches in coffee production by means of the same approach. Tentative identification of mass peaks aided characterisation of aroma fractions. Classification pinpointed some volatile compounds important for discrimination of coffees.</p>
2013
[1456] Zardin, E., O. Tyapkova, A. Buettner, and J. Beauchamp, "Performance assessment of proton-transfer-reaction time-of-flight mass spectrometry (PTR-TOF-MS) for analysis of isobaric compounds in food-flavour applications", \{LWT\} - Food Science and Technology, pp. -, 2013.
Link: http://www.sciencedirect.com/science/article/pii/S0023643813003964
Abstract
<p>Abstract Characterisation of food-flavour release using quadrupole-based on-line mass spectrometers such as proton-transfer-reaction mass spectrometry (PTR-MS, or PTR-QMS) can be complicated when nominally isobaric aroma compounds are present in complex food matrices. The recent combination of PTR-MS with time-of-flight mass spectrometry (PTR-TOF-MS) offers an analytical tool potentially capable of overcoming this problem because of its enhanced mass resolution. In this context, four pairs of isobaric compounds (cis-3-hexenol and 2,3-pentanedione, benzaldehyde and m-xylene, ethyl butanoate and 2-methylbutanol, and isobutyl isopentanoate and 1-hexanol) were investigated by PTR-TOF-MS to assess its mass-resolving power for food-flavour applications. Headspace analyses of aqueous solutions containing nominally isobaric aroma compounds that are unresolvable by PTR-QMS demonstrated that the PTR-TOF-MS mass-resolving power, which is m/z-dependent, enabled discrimination between isobaric peaks at a centre of mass separation down to at least 0.030&nbsp;Da. Visual discrimination between these isobaric compound peaks in the headspace of aqueous solutions down to a concentration range of a few tens of ng&nbsp;mL&minus;1 was also possible, enabling an empirical method for determining the limit of quantitation in solution for single compounds. PTR-TOF-MS offers distinct advantages over conventional PTR-MS for certain flavour release applications.</p>
[Sidheswaran2013] Sidheswaran, M., S. Cohn, D. P. Sullivan, and L. A. Gundel, "Performance Evaluation of Real Time Formaldehyde Monitors: PTR-MS and Interscan 4160-500B Portable Monitor", , 2013.
Link: http://eetd.lbl.gov/sites/all/files/lbnl-6357e.pdf
[1458] Beauchamp, J., J. Herbig, J. Dunkl, W. Singer, and A. Hansel, "On the performance of proton-transfer-reaction mass spectrometry for breath-relevant gas matrices", Measurement Science and Technology, vol. 24, pp. 125003, 2013.
Link: http://stacks.iop.org/0957-0233/24/i=12/a=125003
[Gloess2013] Gloess, A. N., M. Wellinger, B. Schoenbaechler, F. Wieland, C. Lindinger, and C. Yeretzian, "Predicting the Sensory Profiles of Coffee based on PTR-ToF-MS and GC-MS Measurements", CONFERENCE SERIES, pp. 54, 2013.
Link: http://www.ionicon.com/sites/default/files/uploads/doc/contributions_ptr_ms_Conference_6.pdf
[Yanagisawa2013] Yanagisawa, N., and K. Enya, "Preliminary results of measurement of volatile compounds adsorbed on diesel exhaust particles by PTR-TOFMS", CONFERENCE SERIES, pp. 239, 2013.
Link: http://www.ionicon.com/sites/default/files/uploads/doc/contributions_ptr_ms_Conference_6.pdf
[1594] Schuhfried, E., T. D. Märk, and F. Biasioli, "Primary Ion Depletion Kinetics (PIDK) Studies as a New Tool for Investigating Chemical Ionization Fragmentation Reactions with PTR-MS.", PLoS One, vol. 8, pp. e66925, 2013.
Link: http://dx.doi.org/10.1371/journal.pone.0066925
Abstract
<p>We report on a new approach for studying fragmentation channels in Proton Transfer Reaction-Mass Spectrometry (PTR-MS), which we name primary ion depletion kinetics (PIDK). PTR-MS is a chemical ionization mass spectrometric (CIMS) technique deploying hydronium ions for the chemical ionization. Induced by extremely high concentrations of analyte M, depletion of the primary ions in the drift tube occurs. This is observed as quasi zero concentration of the primary ion H3O(+), and constant MH(+). Under these non-standard conditions, we find an overall changed fragmentation. We offer two explanations. Either the changed fragmentation pattern is the result of secondary proton transfer reactions. Or, alternatively, the fast depletion of H3O(+) leads to reduced heating of H3O(+) in the drift field, and consequently changed fragmentation following protonation of the analyte M. In any case, we use the observed changes in fragmentation as a successful new approach to fragmentation studies, and term it primary ion depletion kinetics, PIDK. PIDK easily yields an abundance of continuous data points with little deviation, because they are obtained in one experimental run, even for low abundant fragments. This is an advantage over traditional internal kinetic energy variation studies (electric field per number density (E/N) variation studies). Also, some interpretation on the underlying fragmentation reaction mechanisms can be gleamed. We measure low occurring fragmentation (&lt;2% of MH(+)) of the compounds dimethyl sulfide, DMS, a compound that reportedly does not fragment, diethyl sulfide DES, and dipropyl sulfide DPS. And we confirm and complement the results with traditional E/N studies. Summing up, the new approach of primary ion depletion kinetics allows for the identification of dehydrogenation [MH(+) -H2] and adduct formation (RMH(+)) as low abundant fragmentation channels in monosulfides.</p>
[Zhang2013] Zhang, G., S. Nan Gao, W. Ding Wei, and Q. Jian Xu, "Proton Transfer Reaction-Mass Spectrometry Determination of the Emission Rate of Flavor Ingredients in Toothpastes", Applied Mechanics and Materials, vol. 299: Trans Tech Publ, pp. 229–232, 2013.
Link: http://www.scientific.net/AMM.299.229
Abstract
Under the experimental conditions, the headspace concentration of two flavor ingredients in toothpastes, limonene (C10H16) and menthone (C10H18O), was measured with proton transfer reaction - mass spectrometry (PTR-MS). Combined with the theoretical diffusion model and analytical solution, the partition coefficient and the emission rate of the two ingredients from toothpaste diluent to the circulated air were calculated. Theoretical Solutions of the distribution coefficients were obtained respectively as 0.00432 and 0.00418 for C10H16 and C10H18O. The corresponding simulated flavor concentration in headspace air Ca(t) had good agreement with the experimental values (R2 = 0.983 and 0.958 respectively). The exponential decay rate formulas for the two flavors were obtained from experimental data and the solution of the theoretical model.
[Hartungen2013] Hartungen, E., S. Juerschik, A. Jordan, A. Edtbauer, S. Feil, G. Hanel, H. Seehauser, S. Haidacher, R. Schottkowsky, L. Märk, et al., "Proton transfer reaction-mass spectrometry: fundamentals, recent advances and applications", The European Physical Journal Applied Physics, vol. 61, no. 02: Cambridge Univ Press, pp. 24303, 2013.
Link: http://journals.cambridge.org/production/action/cjoGetFulltext?fulltextid=8836242
Abstract
Proton transfer reaction-mass spectrometry (PTR-MS) offers many advantages for trace gas analysis, including no sample preparation, real-time analysis, high selectivity and sensitivity, ultra-low detection limits and very short response times. These characteristic features have made it an ideal tool for many applications in science, technology and society. Here we will discuss recent developments, in particular advances concerning sensitivity, selectivity and general applicability.

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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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