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Scientific Articles - PTR-MS Bibliography

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Found 59 results
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2016
[1791] Müller, M., B. E. Anderson, A. J. Beyersdorf, J. H. Crawford, G. S. Diskin, P. Eichler, A. Fried, F. N. Keutsch, T. Mikoviny, K. L. Thornhill, et al., "In situ measurements and modeling of reactive trace gases in a small biomass burning plume", Atmospheric Chemistry and Physics, vol. 16, pp. 3813–3824, 2016.
Link: http://www.atmos-chem-phys.net/16/3813/2016/
Abstract
<p>An instrumented NASA P-3B aircraft was used for airborne sampling of trace gases in a plume that had emanated from a small forest understory fire in Georgia, USA. The plume was sampled at its origin to derive emission factors and followed &thinsp;&sim;&thinsp;13.6 km downwind to observe chemical changes during the first hour of atmospheric aging. The P-3B payload included a proton-transfer-reaction time-of-flight mass spectrometer (PTR-ToF-MS), which measured non-methane organic gases (NMOGs) at unprecedented spatiotemporal resolution (10 m spatial/0.1 s temporal). Quantitative emission data are reported for CO2, CO, NO, NO2, HONO, NH3, and 16 NMOGs (formaldehyde, methanol, acetonitrile, propene, acetaldehyde, formic acid, acetone plus its isomer propanal, acetic acid plus its isomer glycolaldehyde, furan, isoprene plus isomeric pentadienes and cyclopentene, methyl vinyl ketone plus its isomers crotonaldehyde and methacrolein, methylglyoxal, hydroxy acetone plus its isomers methyl acetate and propionic acid, benzene, 2,3-butanedione, and 2-furfural) with molar emission ratios relative to CO larger than 1 ppbV ppmV&minus;1. Formaldehyde, acetaldehyde, 2-furfural, and methanol dominated NMOG emissions. No NMOGs with more than 10 carbon atoms were observed at mixing ratios larger than 50 pptV ppmV&minus;1 CO. Downwind plume chemistry was investigated using the observations and a 0-D photochemical box model simulation. The model was run on a nearly explicit chemical mechanism (MCM v3.3) and initialized with measured emission data. Ozone formation during the first hour of atmospheric aging was well captured by the model, with carbonyls (formaldehyde, acetaldehyde, 2,3-butanedione, methylglyoxal, 2-furfural) in addition to CO and CH4 being the main drivers of peroxy radical chemistry. The model also accurately reproduced the sequestration of NOx into peroxyacetyl nitrate (PAN) and the OH-initiated degradation of furan and 2-furfural at an average OH concentration of 7.45 &plusmn; 1.07 &times; 106 cm&minus;3 in the plume. Formaldehyde, acetone/propanal, acetic acid/glycolaldehyde, and maleic acid/maleic anhydride (tentatively identified) were found to be the main NMOGs to increase during 1 h of atmospheric plume processing, with the model being unable to capture the observed increase. A mass balance analysis suggests that about 50 % of the aerosol mass formed in the downwind plume is organic in nature.</p>
2015
[1710] Gamero-Negrón, R., J. {Sánchez Del Pulgar}, L. Cappellin, C. García, F. Gasperi, and F. Biasioli, "Immune-spaying as an alternative to surgical spaying in Iberian × Duroc females: Effect on the VOC profile of dry-cured shoulders and dry-cured loins as detected by PTR-ToF-MS.", Meat Sci, vol. 110, pp. 169–173, Dec, 2015.
Link: http://dx.doi.org/10.1016/j.meatsci.2015.07.018
Abstract
<p>Immunocastration in pigs has been proposed as a cruelty-free alternative to surgical castration. In this work the effect of immune-spaying of female pigs on the volatile compound profile of Iberian dry-cured products was evaluated. The head-space volatile compound of dry-cured shoulders and loins from surgically spayed, immune-spayed and entire Iberian &times; Duroc females was characterized by proton transfer reaction-time of flight-mass spectrometry. It was not possible to identify a significant effect of the castration modality on dry-cured shoulders, probably because of the heterogeneity of samples. Contrarily, Principal Component Analysis of dry-cured loins indicates a better homogeneity of samples and the separation of loins from surgically spayed and immune-spayed females. Some mass peaks tentatively identified as important flavor compounds in dry-cured products, 3-methylbutanal, 2,3-butanedione and 3-methylbutanoic acid, were significantly higher in the immune-spayed females. Therefore, immune-spaying seems to have a negligible effect on the volatile compound profile of dry-cured shoulders, whereas it could affect the VOC profile in the case of dry-cured loins.</p>
[1715] Sukul, P., P. Trefz, S. Kamysek, J. K. Schubert, and W. Miekisch, "Instant effects of changing body positions on compositions of exhaled breath.", J Breath Res, vol. 9, pp. 047105, Dec, 2015.
Link: http://dx.doi.org/10.1088/1752-7155/9/4/047105
Abstract
<p>Concentrations of exhaled volatile organic compounds (VOCs) may depend not only on biochemical or pathologic processes but also on physiological parameters. As breath sampling may be done in different body positions, effects of the sampling position on exhaled VOC concentrations were investigated by means of real-time mass spectrometry. Breaths from 15 healthy volunteers were analyzed in real-time by PTR-ToF-MS-8000 during paced breathing (12/min) in a continuous side-stream mode. We applied two series of body positions (setup 1: sitting, standing, supine, and sitting; setup 2: supine, left lateral, right lateral, prone, and supine). Each position was held for 2&thinsp;min. Breath VOCs were quantified in inspired and alveolar air by means of a custom-made algorithm. Parallel monitoring of hemodynamics and capnometry was performed noninvasively. In setup 1, when compared to the initial sitting position, normalized mean concentrations of isoprene, furan, and acetonitrile decreased by 24%, 26%, and 9%, respectively, during standing and increased by 63%, 36%, and 10% during lying mirroring time profiles of stroke volume and pET-CO2. In contrast, acetone and H2S concentrations remained almost constant. In setup 2, when compared to the initial supine position, mean alveolar concentrations of isoprene and furan increased significantly up to 29% and 16%, respectively, when position was changed from lying on the right side to the prone position. As cardiac output and stroke volume decreased at that time, the reasons for the observed concentrations changes have to be linked to the ventilation/perfusion ratio or compartmental distribution rather than to perfusion alone. During final postures, all VOC concentrations, hemodynamics, and pET-CO2 returned to baseline. Exhaled blood-borne VOC profiles changed due to body postures. Changes depended on cardiac stroke volume, origin, compartmental distribution and physico-chemical properties of the substances. Patients&#39; positions and cardiac output have to be controlled when concentrations of breath VOCs are to be interpreted in terms of biomarkers.</p>
[1625] Hu, L., D. B. Millet, M. Baasandorj, T. J. Griffis, P. Turner, D. Helmig, A. J. Curtis, and J. Hueber, "Isoprene emissions and impacts over an ecological transition region in the US Upper Midwest inferred from tall tower measurements", Journal of Geophysical Research: Atmospheres, Mar, 2015.
Link: http://dx.doi.org/10.1002/2014JD022732
Abstract
<p>We present one year of in-situ PTR-MS measurements of isoprene and its oxidation products MVK and MACR from a 244 m tall tower in the US Upper Midwest, located at an ecological transition between isoprene-emitting deciduous forest and predominantly non-isoprene-emitting agricultural landscapes. We find that anthropogenic interferences (or anthropogenic isoprene) contribute on average 20% of the PTR-MS m/z 69 signal during summer daytime, whereas MVK+MACR interferences (m/z 71) are minor (7%). After removing these interferences, the observed isoprene and MVK+MACR abundances show pronounced seasonal cycles, reaching summertime maxima of &gt;2500 pptv (1-hour mean). The tall tower is impacted both by nearby and more distant regional isoprene sources, with daytime enhancements of isoprene (but little MVK+MACR) under southwest winds, and enhancements of MVK+MACR (but little isoprene) at other times. We find that the GEOS-Chem atmospheric model with the MEGANv2.1 biogenic inventory can reproduce the isoprene observations to within model uncertainty given improved land cover and temperature estimates. However, a 60% low model bias in MVK+MACR cannot be resolved, even across diverse model assumptions for NOx emissions, chemistry, atmospheric mixing, dry deposition, land cover, and potential measurement interferences. This implies that, while isoprene emissions in the immediate vicinity of the tall tower are adequately captured, they are underestimated across the broader region. We show that this region experiences a strong seasonal shift between VOC-limited chemistry during the spring and fall and NOx-limited or transitional chemistry during the summer, driven by the spatiotemporal distribution of isoprene emissions. Isoprene&#39;s role in causing these chemical shifts is likely underestimated due to the underprediction of its regional emissions.</p>
2014
[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>
2013
[1592] Mesurolle, J., A. Saint-Eve, I. Déléris, and I. Souchon, "Impact of fruit piece structure in yogurts on the dynamics of aroma release and sensory perception.", Molecules, vol. 18, pp. 6035–6056, 2013.
Link: http://dx.doi.org/10.3390/molecules18056035
Abstract
<p>The aim of this work was to gain insight into the effect of food formulation on aroma release and perception, both of which playing an important role in food appreciation. The quality and quantity of retronasal aroma released during food consumption affect the exposure time of olfactory receptors to aroma stimuli, which can influence nutritional and hedonic characteristics, as well as consumption behaviors. In yogurts, fruit preparation formulation can be a key factor to modulate aroma stimulation. In this context, the impact of size and hardness of fruit pieces in fat-free pear yogurts was studied. Proton Transfer Reaction-Mass Spectrometry (PTR-MS) was used to allow sensitive and on-line monitoring of volatile odorous compound release in the breath during consumption. In parallel, a trained panel used sensory profile and Temporal Dominance of Sensations (TDS) methods to characterize yogurt sensory properties and their dynamic changes during consumption. Results showed that the size of pear pieces had few effects on aroma release and perception of yogurts, whereas fruit hardness significantly influenced them. Despite the fact that yogurts presented short and similar residence times in the mouth, this study showed that fruit preparation could be an interesting formulation factor to enhance exposure time to stimuli and thus modify food consumption behaviors. These results could be taken into account to formulate new products that integrate both nutritional and sensory criteria.</p>
[Deleris2013] Déléris, I., M. Kauffmann, A. Saint-Eve, G. Féron, and I. Souchon, "Improvement in the understanding of aroma compound retention and release in naso-oro-pharyngeal cavity", CONFERENCE SERIES, pp. 156, 2013.
Link: http://www.ionicon.com/sites/default/files/uploads/doc/contributions_ptr_ms_Conference_6.pdf
[1461] Yuan, B., C. Warneke, M. Shao, and J. A. de Gouw, "Interpretation of volatile organic compound measurements byproton-transfer-reaction mass spectrometry over the deepwaterhorizon oil spill", International Journal of Mass Spectrometry, vol. (in press), 2013.
Link: http://dx.doi.org/10.1016/j.ijms.2013.11.006
Abstract
<p>tA proton-transfer-reaction mass spectrometer (PTR-MS) was used onboard the NOAA WP-3D aircraftfor atmospheric measurements over the Deepwater Horizon (DWH) oil spill in the Gulf of Mexico in2010. A mass spectrum obtained by PTR-MS downwind from the accident site revealed the presenceof a complex mixture of volatile organic compounds (VOCs). Here, we interpret this mass spectrum bycomparing it with mass spectra of crude oil, gasoline and diesel samples measured in the laboratory.Aromatics were less abundant over the spill than from crude oil samples, due to the dissolution of thesespecies in the seawater. The mass spectra obtained from aircraft measurements and crude oil samplesboth show strong signals at masses with mass-to-charge ratio (m/z) of 14 &times; n &plusmn; 1, including 43, 57, 69,71, 83, 85, 97 and 111Yamu. PTR-MS coupled with a gas chromatograph was used to identify majormass signals from crude oil samples. Cycloalkanes are important contributors to the signals of mass m/z14 &times; n &plusmn; 1, especially for masses 69, 83, 97 and 111 amu. Aromatics could be interpreted from their specificmasses without significant interference for crude oil vapors, but the interferences to benzene from higheraromatics can be significant as crude oil evaporates. The interpretation of DWH mass spectrum is notonly helpful in understanding the atmospheric emissions associated with the DWH oil spill, but also forthe interpretation of PTR-MS measurements in urban air, near natural oil seeps and oil as well as naturalgas extraction activities.</p>
[Kassebacher2013] Kassebacher, T., P. Sulzer, S. Juerschik, E. Hartungen, A. Jordan, A. Edtbauer, S. Feil, G. Hanel, S. Jaksch, L. Maerk, et al., "Investigations of chemical warfare agents and toxic industrial compounds with proton-transfer-reaction mass spectrometry for a real-time threat monitoring scenario.", Rapid Commun Mass Spectrom, vol. 27, no. 2: Austria., pp. 325–332, Jan, 2013.
Link: http://dx.doi.org/10.1002/rcm.6456
Abstract
Security and protection against terrorist attacks are major issues in modern society. One especially challenging task is the monitoring and protection of air conditioning and heating systems of buildings against terrorist attacks with toxic chemicals. As existing technologies have low selectivity, long response times or insufficient sensitivity, there is a need for a novel approach such as we present here.We have analyzed various chemical warfare agents (CWAs) and/or toxic industrial compounds (TICs) and related compounds, namely phosgene, diphosgene, chloroacetone, chloroacetophenone, diisopropylaminoethanol, and triethyl phosphate, utilizing a high-resolution proton-transfer-reaction time-of-flight mass spectrometry (PTR-TOFMS) instrument with the objective of finding key product ions and their intensities, which will allow a low-resolution quadrupole mass spectrometry based PTR-MS system to be used with high confidence in the assignment of threat agents in the atmosphere.We obtained high accuracy PTR-TOFMS mass spectra of the six compounds under study at two different values for the reduced electric field in the drift tube (E/N). From these data we have compiled a table containing product ions, and isotopic and E/N ratios for highly selective threat compound detection with a compact and cost-effective quadrupole-based PTR-MS instrument. Furthermore, using chloroacetophenone (tear gas), we demonstrated that this instrument's response is highly linear in the concentration range of typical Acute Exposure Guideline Levels (AEGLs).On the basis of the presented results it is possible to develop a compact and cost-effective PTR-QMS instrument that monitors air supply systems and triggers an alarm as soon as the presence of a threat agent is detected. We hope that this real-time surveillance device will help to seriously improve safety and security in environments vulnerable to terrorist attacks with toxic chemicals.
[Ting2013] Ting, V. J. L., C. Soukoulis, E. Aprea, P. Silcock, P. Bremer, A. Romano, L. Cappellin, F. Gasperi, and F. Biasioli, "In-vivo volatile organic compound (VOC) release from fresh-cut apple cultivars: PTR-Quad-MS and PTR-ToF-MS", CONFERENCE SERIES, pp. 229, 2013.
Link: http://www.ionicon.com/sites/default/files/uploads/doc/contributions_ptr_ms_Conference_6.pdf
[1598] Ruzsanyi, V.., "Ion mobility spectrometry for pharmacokinetic studies–exemplary application.", J Breath Res, vol. 7, pp. 046008, Dec, 2013.
Link: http://dx.doi.org/10.1088/1752-7155/7/4/046008
Abstract
<p>Breath analysis is an attractive non-invasive method for diagnosis and therapeutic monitoring. It uses endogenously produced compounds and metabolites of isotopically labeled precursors. In order to make such tests clinically useful, it is important to have relatively small portable instruments detecting volatile compounds within short time. A particularly promising analytical technique is ion mobility spectrometry (IMS) coupled to a multi capillary column (MCC). This paper focuses on demonstrating the suitability of breath analysis for pharmacokinetic applications using MCC-IMS with respect to practicability and reproducibility testing the model substrate eucalyptol. Validation of the MCC-IMS measurements were performed using proton transfer reaction mass spectrometry (PTR-MS) and resulted in an excellent correspondence of the time-dependent concentrations presented by the two different analytical techniques. Moreover, the good accordance in variance of kinetic parameters with repeated measures, and the determined inter-subject differences indicate the eligibility of the analysis method.</p>
2012
[Luchner2012] Luchner, M., R. Gutmann, K. Bayer, J. Dunkl, A. Hansel, J. Herbig, W. Singer, F. Strobl, K. Winkler, and G. Striedner, "Implementation of proton transfer reaction-mass spectrometry (PTR-MS) for advanced bioprocess monitoring.", Biotechnol Bioeng, vol. 109, no. 12: ACIB GmbH, Muthgasse 11, A-1190 Vienna, Austria., pp. 3059–3069, Dec, 2012.
Link: http://dx.doi.org/10.1002/bit.24579
Abstract
We report on the implementation of proton transfer reaction-mass spectrometry (PTR-MS) technology for on-line monitoring of volatile organic compounds (VOCs) in the off-gas of bioreactors. The main part of the work was focused on the development of an interface between the bioreactor and an analyzer suitable for continuous sampling of VOCs emanating from the bioprocess. The permanently heated sampling line with an inert surface avoids condensation and interaction of volatiles during transfer to the PTR-MS. The interface is equipped with a sterile sinter filter unit directly connected to the bioreactor headspace, a condensate trap, and a series of valves allowing for dilution of the headspace gas, in-process calibration, and multiport operation. To assess the aptitude of the entire system, a case study was conducted comprising three identical cultivations with a recombinant E. coli strain, and the volatiles produced in the course of the experiments were monitored with the PTR-MS. The high reproducibility of the measurements proved that the established sampling interface allows for reproducible transfer of volatiles from the headspace to the PTR-MS analyzer. The set of volatile compounds monitored comprises metabolites of different pathways with diverse functions in cell physiology but also volatiles from the process matrix. The trends of individual compounds showed diverse patterns. The recorded signal levels covered a dynamic range of more than five orders of magnitude. It was possible to assign specific volatile compounds to distinctive events in the bioprocess. The presented results clearly show that PTR-MS was successfully implemented as a powerful bioprocess-monitoring tool and that access to volatiles emitted by the cells opens promising perspectives in terms of advanced process control.
[JLTing2012] Ting, V. J. L., C. Soukoulis, P. Silcock, L. Cappellin, A. Romano, E. Aprea, P. J. Bremer, T. D. Märk, F. Gasperi, and F. Biasioli, "In Vitro and In Vivo Flavor Release from Intact and Fresh-Cut Apple in Relation with Genetic, Textural, and Physicochemical Parameters", Journal of food science, vol. 77, no. 11: Wiley Online Library, pp. C1226–C1233, 2012.
Link: http://onlinelibrary.wiley.com/doi/10.1111/j.1750-3841.2012.02947.x/full
Abstract
Flavor release from 6 commercial apple cultivars (Fuji, Granny Smith, Golden Delicious, Jonagold, Morgen Dallago, and Red Delicious) under static conditions (intact or fresh-cut samples) and during consumption of fresh-cut samples (nosespace) was determined by proton transfer reaction mass spectrometry. Textural (firmness, fracturability, flesh elasticity, and rupture) and physicochemical (pH, acidity, and water content) properties of the apples were also measured. Static headspace analysis of intact fruits revealed Fuji and Granny Smith apples had the lowest concentration for all measured flavor compounds (esters, aldehydes, alcohols, and terpenes), whereas Red Delicious apples had the highest. Fresh-cut samples generally showed a significant increase in total volatile compounds with acetaldehyde being most abundant. However, compared to intact fruits, cut Golden and Red Delicious apples had a lower intensity for ester related peaks. Five parameters were extracted from the nosespace data of peaks related to esters (m/z 43, 61), acetaldehyde (m/z 45), and ethanol (m/z 47): 2 associated with mastication (duration of mastication–tcon; time required for first swallowing event–tswal), and 3 related with in-nose volatile compound concentration (area under the curve–AUC; maximum intensity–Imax; time for achieving Imax–tmax). Three different behaviors were identified in the nosespace data: a) firm samples with low AUC and tswal values (Granny Smith, Fuji), b) mealy samples with high AUC, Imax, tswal values, and low tcon (Morgen Dallago, Golden Delicious), and c) firm samples with high AUC and Imax values (Red Delicious). Strengths and limitations of the methodology are discussed.
[Ting2012] Ting, V. J. L., C. Soukoulis, P. Silcock, L. Cappellin, A. Romano, E. Aprea, P. J. Bremer, T. D. Maerk, F. Gasperi, and F. Biasioli, "In vitro and in vivo flavor release from intact and fresh-cut apple in relation with genetic, textural, and physicochemical parameters.", J Food Sci, vol. 77, no. 11: Research and Innovation Centre, Foundation Edmund Mach, via Mach 1, San Michele all' Adige, (TN), Italy., pp. C1226–C1233, Nov, 2012.
Link: http://dx.doi.org/10.1111/j.1750-3841.2012.02947.x
Abstract
Flavor release from 6 commercial apple cultivars (Fuji, Granny Smith, Golden Delicious, Jonagold, Morgen Dallago, and Red Delicious) under static conditions (intact or fresh-cut samples) and during consumption of fresh-cut samples (nosespace) was determined by proton transfer reaction mass spectrometry. Textural (firmness, fracturability, flesh elasticity, and rupture) and physicochemical (pH, acidity, and water content) properties of the apples were also measured. Static headspace analysis of intact fruits revealed Fuji and Granny Smith apples had the lowest concentration for all measured flavor compounds (esters, aldehydes, alcohols, and terpenes), whereas Red Delicious apples had the highest. Fresh-cut samples generally showed a significant increase in total volatile compounds with acetaldehyde being most abundant. However, compared to intact fruits, cut Golden and Red Delicious apples had a lower intensity for ester related peaks. Five parameters were extracted from the nosespace data of peaks related to esters (m/z 43, 61), acetaldehyde (m/z 45), and ethanol (m/z 47): 2 associated with mastication (duration of mastication-t(con); time required for first swallowing event-t(swal)), and 3 related with in-nose volatile compound concentration (area under the curve-AUC; maximum intensity-I(max); time for achieving I(max)-t(max)). Three different behaviors were identified in the nosespace data: a) firm samples with low AUC and t(swal) values (Granny Smith, Fuji), b) mealy samples with high AUC, I(max), t(swal) values, and low t(con) (Morgen Dallago, Golden Delicious), and c) firm samples with high AUC and I(max) values (Red Delicious). Strengths and limitations of the methodology are discussed. PRACTICAL APPLICATION: Volatile compounds play a fundamental role in the perceived quality of food. Using apple cultivars, this research showed that in vivo proton transfer reaction mass spectrometry (PTR-MS) could be used to determine the relationship between the release of volatile flavor compounds and the physicochemical parameters of a real food matrix. This finding suggests that in vivo PTR-MS coupled with traditional physicochemical measurements could be used to yield information on flavor release from a wide range of food matrices and help in the development of strategies to enhance food flavor and quality.
[Frank2012] Frank, D., I. Appelqvist, U. Piyasiri, and C. Delahunty, "In vitro measurement of volatile release in model lipid emulsions using proton transfer reaction mass spectrometry.", J Agric Food Chem, vol. 60, no. 9: Food Futures Flagship, CSIRO Food, Nutritional Sciences, North Ryde, New South Wales, Australia. damian.frank@csiro.au, pp. 2264–2273, Mar, 2012.
Link: http://dx.doi.org/10.1021/jf204120h
Abstract
The presence of fat in food plays an important role in the way aroma is released during consumption and in the creation of the overall sensory impression. Fat acts as a reservoir for lipophilic volatile compounds and modulates the timing and delivery of aroma compounds in a unique manner. Despite considerable research, reproducible in vitro methods for measuring the effect of fat on volatile release are lacking. An open in vitro cell was used to simulate the open human naso-oropharygeal system and was interfaced with a proton transfer reaction mass spectrometer (PTR-MS) to examine some of the fundamental effects of fat on dynamic volatile release in liquid fat emulsions. Lipid emulsions with various fat contents (0-20%) and droplet sizes (0.25, 0.5, and 5.0 ?M) were spiked with flavor volatiles representing a range of lipophilicity (K(o/w) = 1-1380). Preloaded syringes of spiked emulsion were injected into the cell, and temporal changes in release were measured under dynamic conditions. Significant differences in release curves were measured according to the lipid content of emulsions, the vapor pressure, and K(o/w) values of the volatile compounds. With increasing addition of fat, the critical volatile release parameters, maximum concentration (I(max)), time to maximum concentration (T(max)), and the integrated area under the concentration curve (AUC), were affected. The in vitro curves were reproducible and in agreement with theory and correlated with the preswallow phase of in vivo release data. An exponential model was used to calculate changes in mass transfer rates with increased fat addition.
[Dunne2012] Dunne, E., I. E. Galbally, S. Lawson, and A. Patti, "Interference in the PTR-MS measurement of acetonitrile at m/ z 42 in polluted urban air�A study using switchable reagent ion PTR-MS", International Journal of Mass Spectrometry, vol. 319: Elsevier, pp. 40–47, 2012.
Link: http://www.sciencedirect.com/science/article/pii/S1387380612001716
Abstract
In Proton Transfer Reaction Mass Spectrometer (PTR-MS) measurements of the atmosphere, the signal at m/z 42 is commonly regarded as a unique measure of acetonitrile. However, two other ions potentially contribute to the signal at m/z 42. These are 13C isotopologues of C3H5+ and the product ion C3H6+ produced by reaction of NO+ and O2+ (present in trace amounts in the H3O+ reagent gas), with a number of volatile organic compounds. Thus, there is the possibility of interference in the measurement of acetonitrile at m/z 42 by PTR-MS. Interference in the measurement of acetonitrile at m/z 42 was quantified in urban air over 17 days in Sydney, Australia, in summer. A PTR-MS with Switchable Reagent Ion capability was used for measurements at m/z 41 and 42 in three different primary reagent ion modes, O2+, NO+ and H3O+, to quantify the contribution of non-acetonitrile compounds to the signal at m/z 42 when the PTR-MS was operating in H3O+ reagent ion mode. Acetonitrile dominated the ion signal at m/z 42; however non-acetonitrile ions contributed 5–41% of the total ion signal at m/z 42. The average corrected and uncorrected acetonitrile concentrations were 120 pptv and 148 pptv respectively. The interference in the m/z 42 signal was calculated from known or interpolated concentrations of compounds identified as potential interferrants. Overall the isotopologue correction is due to alkenes including isoprene with probable contributions from other compounds not measured in this study. The other component of the interference, produced by reactions of O2+, is due to alkanes and alkenes. Levoglucosan, a biomass burning tracer in atmospheric particulate matter was more highly correlated with the corrected acetonitrile signal than the uncorrected acetonitrile signal. Measurements of acetonitrile by PTR-MS at m/z 42 in urban air will frequently require correction because of the non-trivial concentrations of alkanes and alkenes commonly observed in urban air.
[Loekke2012] Loekke, M. Marie, M. Edelenbos, E. Larsen, and A. Feilberg, "Investigation of Volatiles Emitted from Freshly Cut Onions (Allium cepa L.) by Real Time Proton-Transfer Reaction-Mass Spectrometry (PTR-MS).", Sensors (Basel), vol. 12, no. 12: Department of Engineering, Aarhus University, Blichers Allé 20, P.O. Box 50, Tjele DK-8830, Denmark. Anders.Feilberg@agrsci.dk., pp. 16060–16076, 2012.
Link: http://dx.doi.org/10.3390/s121216060
Abstract
Volatile organic compounds (VOCs) in cut onions (Allium cepa L.) were continuously measured by PTR-MS during the first 120 min after cutting. The headspace composition changed rapidly due to the very reactive volatile sulfurous compounds emitted from onion tissue after cell disruption. Mass spectral signals corresponding to propanethial S-oxide (the lachrymatory factor) and breakdown products of this compound dominated 0-10 min after cutting. Subsequently, propanethiol and dipropyl disulfide predominantly appeared, together with traces of thiosulfinates. The concentrations of these compounds reached a maximum at 60 min after cutting. Propanethiol was present in highest concentrations and had an odor activity value 20 times higher than dipropyl disulfide. Thus, propanethiol is suggested to be the main source of the characteristic onion odor. Monitoring the rapid changes of VOCs in the headspace of cut onion necessitates a high time resolution, and PTR-MS is demonstrated to be a very suitable method for monitoring the headspace of freshly cut onions directly after cutting without extraction or pre-concentration.
[Sulzer2012b] Sulzer, P., A. Jordan, E. Hartungen, and T. Maerk, "Ionisation method for a universal gas analyzer", , no. EP2606505A1, 2012.
Link: http://www.freepatentsonline.com/EP2421024.html
2011
[Deleris2011] Déléris, I., A. Saint-Eve, Y. Guo, P. Lieben, M-L. Cypriani, N. Jacquet, P. Brunerie, and I. Souchon, "Impact of swallowing on the dynamics of aroma release and perception during the consumption of alcoholic beverages", Chemical senses, vol. 36, no. 8: Oxford Univ Press, pp. 701–713, 2011.
Link: http://chemse.oxfordjournals.org/content/36/8/701.short
Abstract
The consumption protocol used during alcoholic beverage tasting may affect aroma perception. We used an integrated approach combining sensory analysis and physicochemistry to investigate the impact of swallowing on aroma release and perception. A panel of 10 persons evaluated the dynamics of aroma perception during the consumption of a commercial flavored vodka, using the method of temporal dominance of sensations. Two protocols (spitting out or swallowing of the product) were tested. Nosespace analysis was simultaneously carried out by proton transfer reaction mass spectrometry to evaluate aroma release in the nasal cavity. Comparison of the results obtained with the 2 protocols highlighted significant differences in both the perception and the release of aroma: the swallowing of the product resulted in more complex perceptions but decreased the dominance rates of aromatic attributes. Ethanol perception also had an impact when the product was swallowed. Aroma release data partly accounted for the differences in perception, particularly as concerned ethanol release. The time at which dominance appears as well as the dominance duration of some attributes can be related to some temporal parameters of release data. But the lack of knowledge concerning the variety and complexity of mechanisms continues to limit our understanding of relationship between aroma release and perception.
[Striedner2011] Striedner, G.., M.. Luchner, R.. Gutmann, A.. Hansel, and K.. Bayer, "Implementation of PTR-MS as tool in bioprocess monitoring - measurement of volatile components in the bioreactor exhaust gas", 5th International PTR-MS Conference on Proton Transfer Reaction Mass Spectrometry and Its Applications, pp. 24, 2011.
Link: http://www.ionicon.com/sites/default/files/uploads/doc/contributions_ptr_ms_Conference_5.pdf
Abstract
Common bioprocess conditions imply a gas-liquid-mixture with living cells as solid phase in a sterile environment which demands a great deal on sensor/analyzer technology and design. Online access to physiology relevant process variables, the ultimate request of process engineers, is still very limited as complexity of biological systems additionally constrains direct measurements...
[Xu2011] Xu, Q., Y. Zhang, J. Mo, and X. Li, "Indoor formaldehyde removal by thermal catalyst: kinetic characteristics, key parameters, and temperature influence.", Environ Sci Technol, vol. 45, no. 13: Department of Building Science, Tsinghua University, Beijing 100084, PR China., pp. 5754–5760, Jul, 2011.
Link: http://dx.doi.org/10.1021/es2009902
Abstract
Thermal catalytic oxidation (TCO) technology can continuously degrade formaldehyde at room temperature without added energy. However, there is very little knowledge on the TCO kinetic reaction mechanism, which is necessary in developing such air cleaners and in comparison with other air cleaning techniques. This paper addresses the problem of a novel TCO catalyst, Pt/MnO(x)-CeO(2). The experiments measuring the outlet concentrations of formaldehyde and other possible byproducts were conducted at temperatures of 25, 40, 60, 100, and 180 °C and at a series of inlet formaldehyde concentrations (280-3000 ppb). To measure the concentrations precisely and real timely, proton transfer reaction-mass spectrometry (PTR-MS) was used. We found the following from the experimental results: (1) no byproducts were detected; (2) the bimolecular L-H kinetic model best described the catalytic reaction rate; (3) the activation energy of the oxidation was about 25.8 kJ mol(-1); (4) TCO is most energy efficient at room temperature without auxiliary heating; (5) compared with photocatalytic oxidation (PCO) which needs ultraviolet light radiation, the reaction area of TCO can be much larger for a given volume so that TCO can perform much better not only in formaldehyde removal efficiency but also in energy saving.
[Dold2011] Dold, S., C. Lindinger, E. Kolodziejczyk, P. Pollien, S. Ali, J. Carlos Germain, S. Garcia Perin, N. Pineau, B. Folmer, K-H. Engel, et al., "Influence of foam structure on the release kinetics of volatiles from espresso coffee prior to consumption.", J Agric Food Chem, vol. 59, no. 20: Nestlé Research Center, P.O. Box 44, 1000 Lausanne 26, Switzerland., pp. 11196–11203, Oct, 2011.
Link: http://dx.doi.org/10.1021/jf201758h
Abstract
The relationship between the physical structure of espresso coffee foam, called crema, and the above-the-cup aroma release was studied. Espresso coffee samples were produced using the Nespresso extraction system. The samples were extracted with water with different levels of mineral content, which resulted in liquid phases with similar volatile profiles but foams with different structure properties. The structure parameters foam volume, foam drainage, and lamella film thickness at the foam surface were quantified using computer-assisted microscopic image analysis and a digital caliper. The above-the-cup volatile concentration was measured online by using PTR-MS and headspace sampling. A correlation study was done between crema structure parameters and above-the-cup volatile concentration. In the first 2.5 min after the start of the coffee extraction, the presence of foam induced an increase of concentration of selected volatile markers, independently if the crema was of high or low stability. At times longer than 2.5 min, the aroma marker concentration depends on both the stability of the crema and the volatility of the specific aroma compounds. Mechanisms of above-the-cup volatile release involved gas bubble stability, evaporation, and diffusion. It was concluded that after the initial aroma burst (during the first 2-3 min after the beginning of extraction), for the present sample space a crema of high stability provides a stronger aroma barrier over several minutes.

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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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