Callback Service

Undefined

The world's leading PTR-MS company

Providing ultra-sensitive solutions for real-time trace gas analysis since 1998

Navigation

You are here

Scientific Articles - PTR-MS Bibliography

Welcome to the new IONICON scientific articles database!

Publications

Found 767 results
Title [ Year(Asc)]
2012
[Bamberger2012] Bamberger, I., L. Hoertnagl, T. Ruuskanen, R. Schnitzhofer, M. Müller, M. Graus, T. Karl, G. Wohlfahrt, and A. Hansel, "Deposition of terpenes to vegetation-a paradigm shift towards bidirectional VOC exchange?", EGU General Assembly Conference Abstracts, vol. 14, pp. 7949, 2012.
Link: http://adsabs.harvard.edu/abs/2012EGUGA..14.7949B
Abstract
Biogenic volatile organic compounds (BVOCs) are important precursors for secondary organic aerosol (SOA) formation (Hallquist et al., 2009). In addition reactive BVOCs play a crucial role in local tropospheric ozone production (Atkinson, 2000). According to the present scientific understanding vegetation is recognized as a major VOC emission source rather than a deposition sink. Our recent observations however demonstrate that an uptake of terpene compounds to mountain grassland can be significant - at least under certain atmospheric conditions. After a severe hailstorm volume mixing ratios (VMR) of locally emitted terpene compounds originating from conifers located at the mountain slopes were strongly enhanced, even during daytime hours. Weeks after the hailstorm our PTR-MS and PTR-time-of-flight (PTR-TOF) instruments still measured deposition fluxes of monoterpenes (m/z 137.133), sesquiterpenes (m/z 205.195), and oxygenated terpenes (m/z 153.128) to the grassland. The total amount of terpenoids (on a carbon basis) deposited to the grassland during the weeks after the hailstorm is comparable to the total methanol emission of the entire growing season (Bamberger et al., 2011). These findings pose the question whether the terminology should be adjusted from VOC emission to VOC exchange.
[Sulzer2012a] Sulzer, P., S. Juerschik, B. Agarwal, T. Kassebacher, E. Hartungen, A. Edtbauer, F. Petersson, J. Warmer, G. Holl, D. Perry, et al., "Designer Drugs and Trace Explosives Detection with the Help of Very Recent Advancements in Proton-Transfer-Reaction Mass Spectrometry (PTR-MS)", Future Security: Springer, pp. 366–375, 2012.
Link: http://link.springer.com/chapter/10.1007/978-3-642-33161-9_55
Abstract
At the "Future Security 2011" we presented an overview of our studies on the "Detection and Identification of Illicit and Hazardous Substances with Proton-Transfer-Reaction Mass Spectrometry (PTR-MS)" including first results on explosives, chemical warfare agents and illicit and prescribed drugs detection. Since then we have considerably extended these preliminary studies to the detection of defined traces of some of the most common explosives, namely TNT, PETN, TATP, and DATP deposited into aluminum foam bodies, and to the detection of a number of novel and widely unknown designer drugs: ethylphenidate, 4-fluoroamphetamine and dimethocaine. Moreover, we have dramatically improved our time-of-flight based PTR-MS instruments by substantially increasing their sensitivity and hence lowering the detection limit, making them even more suitable and applicable to threat agents with extremely low vapour pressures. Data from measurements on certified gas standards are presented in order to underline these statements. The data demonstrate that, in comparison to the first generation instruments, a gain of one order of magnitude in terms of sensitivity and detection limit has been obtained.
[Schuhfried2012] Schuhfried, E., E. Aprea, L. Cappellin, C. Soukoulis, R. Viola, T. D. Maerk, F. Gasperi, and F. Biasioli, "Desorption kinetics with PTR-MS: Isothermal differential desorption kinetics from a heterogeneous inlet surface at ambient pressure and a new concept for compound identification", International journal of mass spectrometry, vol. -: Elsevier, pp. -, 2012.
Link: http://www.sciencedirect.com/science/article/pii/S1387380612000292
Abstract
Proton transfer reaction-mass spectrometry (PTR-MS) is a soft ionization mass spectrometric technique for monitoring volatile organic compounds (VOCs) with a very low limit of detection (LOD) (parts per trillion by volume) and excellent time resolution (split seconds). This makes PTR-MS a particularly interesting instrument for investigating surface desorption kinetics of volatile organic compounds (VOCs) under realistic conditions, i.e., at ambient pressure from a heterogeneous surface. Here, we report on the investigation of heterogeneous inlet surface kinetics with PTR-MS and based thereon, develop concepts to assist compound identification in PTR-MS. First, we studied differential isothermal desorption kinetics using heterogeneous inlet surface data measured by Mikoviny et al. [7] with their newly developed high-temp-PTR-MS. The best fit to their data is obtained with bimodal pseudo-first order kinetics. In addition, we explored the normalization of the data and calculated data points of the desorption isotherms. We found evidence that the interesting part of the isotherm can be linearized in a double log plot. Then we investigated the idea to use memory effects of the inlet system to assist compound identification. At the moment, the main problem is the dependence of the kinetics on the initial equilibrium gas phase adsorption concentration, and thus, the surface coverage. As a solution, we suggest an empirical, quasi-concentration independent, yet compound specific parameter: the normalized desorption time tnd describing the decline of the signal to 1/e2 of the initial concentration, normalized to an initial concentration of 10,000 counts per second (cps). Furthermore, we investigated property–property and structure–property relationships of this new parameter. Further possible improvements are discussed as well.
[Kassebacher2012] Kassebacher, T., P. Sulzer, S. Juerschik, B. Agarwal, F. Petersson, E. Hartungen, H. Seehauser, and T. D. Maerk, "Detecting and Quantifying Toxic Industrial Compounds (TICs) with Proton-Transfer-Reaction Mass Spectrometry (PTR-MS)", Future Security: Springer, pp. 438–447, 2012.
Link: http://link.springer.com/chapter/10.1007/978-3-642-33161-9_62
Abstract
In the course of the FP7-SEC project "SPIRIT" (Safety and Protection of built Infrastructure to Resist Integral Threats) we focused our research with Proton-Transfer-Reaction Mass Spectrometry (PTR-MS) on C-agents, specifically Toxic Industrial Compounds (TICs). Most TICs are readily available and represent a considerable threat when used in terroristic attacks. We show the principal procedure of PTR-MS detection measurements on two chemicals, namely phosgene and chloroacetone. With studies of the former we want to point out principle differences between measurements on a quadrupole mass filter based and a Time-of-Flight-based PTR-MS instrument and point out the respective benefits and drawbacks. For the latter we present the results of a diluted headspace measurement and illustrate the connection with security standards in buildings.
[Zehm2012] Zehm, S., S. Schweinitz, R. Wuerzner, H. Peter Colvin, and J. Rieder, "Detection of Candida albicans by mass spectrometric fingerprinting.", Curr Microbiol, vol. 64, no. 3: Department of Vascular Surgery, Innsbruck University Hospital, Anichstrasse 35, Innsbruck, Austria. sarah.zehm@gmail.com, pp. 271–275, Mar, 2012.
Link: http://dx.doi.org/10.1007/s00284-011-0064-5
Abstract
<p>Candida albicans is one of the most frequent causes of fungal infections in humans. Significant correlation between candiduria and invasive candidiasis has previously been described. The existing diagnostic methods are often time-consuming, cost-intensive and lack in sensitivity and specificity. In this study, the profile of low-molecular weight volatile compounds in the headspace of C. albicans-urine suspensions of four different fungal cell concentrations compared to nutrient media and urine without C. albicans was determined using proton-transfer reaction mass spectrometry (PTR-MS). At fungal counts of 1.5 x 10(5) colony forming units (CFU)/ml signals at 45, 47 and 73 atomic mass units (amu) highly significantly increased. At fungal counts of &lt;1.5 x 10(5) CFU/ml signals at 47 and 73 amu also increased, but only at 45 amu a statistically significant increase was seen. Time course alterations of signal intensities dependent on different cell concentrations and after addition of Sabouraud nutrient solution were analysed. Recommendations for measurement conditions are given. Our study is the first to describe headspace profiling of C. albicans-urine suspensions of different fungal cell concentrations. PTR-MS represents a promising approach to rapid, highly sensitive and non-invasive clinical diagnostics allowing qualitative and quantitative analysis.</p>
[Agarwal2012] Agarwal, B.., S.. Juerschik, P.. Sulzer, F.. Petersson, S.. Jaksch, A.. Jordan, and T.. D. Maerk, "Detection of isocyanates and polychlorinated biphenyls using proton transfer reaction mass spectrometry.", Rapid Commun Mass Spectrom, vol. 26, no. 8: Institut fuer Ionenphysik und Angewandte Physik, Leopold Franzens Universitaet Innsbruck, Technikerstr. 25, A-6020 Innsbruck, Austria., pp. 983–989, Apr, 2012.
Link: http://dx.doi.org/10.1002/rcm.6173
Abstract
Isocyanates are highly reactive species widely used in industry. They can cause irritation of the eyes, trigger asthma, etc. Polychlorinated biphenyls (PCBs) were widely used in electrical equipments like capacitors and transformers in the last century and are still present in the environment today. PCBs are known to cause cancer and to affect the immune, reproductive, nervous and endocrine systems. Therefore, there is a need for a simple, rapid and reliable analytical method for the detection of traces of isocyanates and of PCBs.The data presented in this paper were obtained using a proton transfer reaction (PTR) time-of-flight mass spectrometer and a high sensitivity PTR quadrupole mass spectrometer. We also utilized a recently developed direct aqueous injection (DAI) inlet system for proton transfer reaction mass spectrometry (PTR-MS) instruments that allows the analysis of trace compounds in liquids.We detected four isocyanates in the headspace above small sample quantities and investigated their fragmentation pathways to obtain a fundamental understanding of the processes involved in proton transfer reactions and also to determine the best operating conditions of the PTR-MS instruments. In addition, nine PCBs were unambiguously identified via their exact mass and isotopic distribution and detected in different concentration levels via direct injection of the liquid.Utilizing recent developments and improvements in PTR-MS, we can rapidly detect two important environmental pollutant compound classes (isocyanates and PCBs) at high accuracy and without any sample preparation. In this paper, we provide proof of the detection of traces of isocyanates and PCBs in air and also of PCBs in liquids. These results could be used for the development of a real-time monitoring device for industrial waste, polluted air or water quality surveillance.
[Knighton2012] W Knighton, B., S. C. Herndon, J. F. Franklin, E. C. Wood, J. Wormhoudt, W. Brooks, E. C. Fortner, and D. T. Allen, "Direct measurement of volatile organic compound emissions from industrial flares using real-time online techniques: Proton Transfer Reaction Mass Spectrometry and Tunable Infrared Laser Differential Absorption Spectroscopy", Industrial & Engineering Chemistry Research, vol. 51, no. 39: ACS Publications, pp. 12674–12684, 2012.
Link: http://pubs.acs.org/doi/abs/10.1021/ie202695v
Abstract
During the 2010 Comprehensive Flare Study a suite of analytical instrumentation was employed to monitor and quantify in real-time the volatile organic compound (VOC) emissions emanating from an industrial chemical process flare burning either propene/natural gas or propane/natural gas. To our knowledge this represents the first time the VOC composition has been directly measured as a function of flare efficiency on an operational full-scale flare. This compositional information was obtained using a suite of proton-transfer-reaction mass spectrometers (PTR-MS) and quantum cascade laser tunable infrared differential absorption spectrometers (QCL-TILDAS) to measure the unburned fuel and associated combustion byproducts. Methane, ethyne, ethene, and formaldehyde were measured using the QC-TILDAS. Propene, acetaldehyde, methanol, benzene, acrolein, and the sum of the C3H6O isomers were measured with the PTR-MS. A second PTR-MS equipped with a gas chromatograph (GC) was operated in parallel and was used to verify the identity of the neutral components that were responsible for producing the ions monitored with the first PTR-MS. Additional components including 1,3-butadiene and C3H4 (propyne or allene) were identified using the GC/PTR-MS. The propene concentrations derived from the PTR-MS were found to agree with measurements made using a conventional GC with a flame ionization detector (FID). The VOC product (excludes fuel components) speciation profile is more dependent on fuel composition, propene versus propane, than on flare type, air-assisted versus steam-assisted, and is essentially constant with respect to combustion efficiency for combustion efficiencies >0.8. Propane flares produce more alkenes with ethene and propene accounting for approximately 80% (per carbon basis) of the VOC combustion product. The propene partial combustion product profile was observed to contain relatively more oxygenated material where formaldehyde and acetaldehyde are major contributors and account for 20 - 25% of VOC product carbon. Steam-assisted flares produce less ethyne and benzene than air-assisted flares. This observation is consistent with the understanding that steam assisted flares are more efficient at reducing soot, which is formed via the same reaction mechanisms that form benzene and ethyne.
[1512] Park, J.-H.., A.. H. Goldstein, J.. Timkovsky, S.. Fares, R.. Weber, J.. Karlik, and R.. Holzinger, "Eddy covariance emission and deposition flux measurements using proton transfer reaction-time of flight-mass spectrometry (PTR-TOF-{MS}): comparison with PTR-{MS} measured vertical gradients and fluxes", Atmospheric Chemistry and Physics Discussions, vol. 12, pp. 20435–20482, Aug, 2012.
Link: http://dx.doi.org/10.5194/acpd-12-20435-2012
Abstract
<p>During summer 2010, a proton transfer reaction-time of flight-mass spectrometer (PTR-TOF-MS) and a standard proton transfer reaction mass spectrometer (PTR-MS) were deployed simultaneously for one month in an orange orchard in the Central Valley of California to collect continuous data suitable for eddy covariance (EC) flux calculations. The high time resolution (5 Hz) and high mass resolution (up to 5000 m Δ m&minus;1) data from the PTR-TOF-MS provided the basis for calculating the concentration and flux for a wide range of volatile organic compounds (VOC). Throughout the campaign, 664 mass peaks were detected in mass-to-charge ratios between 10 and 1278. Here we present PTR-TOF-MS EC fluxes of the 27 ion species for which the vertical gradient was simultaneously measured by PTR-MS. These EC flux data were validated through spectral analysis (i.e. co-spectrum, normalized co-spectrum, and ogive). Based on inter-comparison of the two PTR instruments, no significant instrumental biases were found in either mixing ratios or fluxes, and the data showed agreement within 5% on average for methanol and acetone. For the measured biogenic volatile organic compounds (BVOC), the EC fluxes from PTR-TOF-MS were in agreement with the qualitatively inferred flux directions from vertical gradient measurements by PTR-MS. For the 27 selected ion species reported here, the PTR-TOF-MS measured total (24 h) mean net flux of 299 μg C m&minus;2 h&minus;1. The dominant BVOC emissions from this site were monoterpenes (m/z 81.070 + m/z 137.131 + m/z 95.086, 34%, 102 μg C m&minus;2 h&minus;1) and methanol (m/z 33.032, 18%, 72 μg C m&minus;2 h&minus;1). The next largest fluxes were detected at the following masses (attribution in parenthesis): m/z 59.048 (mostly acetone, 12.2%, 36.5 μg C m&minus;2 h&minus;1), m/z 61.027 (mostly acetic acid, 11.9%, 35.7 μg C m&minus;2 h&minus;1), m/z 93.069 (para-cymene + toluene, 4.1%, 12.2 μg C m&minus;2 h&minus;1), m/z 45.033 (acetaldehyde, 3.8%, 11.5 μg C m&minus;2 h&minus;1), m/z 71.048 (methylvinylketone + methacrolein, 2.4%, 7.1 μg C m&minus;2 h&minus;1), and m/z 69.071 (isoprene + 2-methyl-3-butene-2-ol, 1.8%, 5.3 μg C m&minus;2 h&minus;1). Low levels of emission and/or deposition (&lt;1.6% for each, 5.8% in total flux) were observed for the additional reported masses. Overall, our results show that EC flux measurements using PTR-TOF-MS is a powerful new tool for characterizing the biosphere-atmosphere exchange including both emission and deposition for a large range of BVOC and their oxidation products.</p>
[Hansen2012c] Hansen, M. J., A. P. S. Adamsen, K. E. N. Jonassen, and A. Feilberg, "The effect of pit ventilation on the emission of odorants from pig production", CHEMICAL ENGINEERING, vol. 30, 2012.
Link: http://www.aidic.it/cet/12/30/039.pdf
[Hansen2012] Hansen, M. J. Ã. ¸rgen, K. Toda, T. Obata, A. Peter S. Adamsen, and A. Feilberg, "Evaluation of single column trapping/separation and chemiluminescence detection for measurement of methanethiol and dimethyl sulfide from pig production.", J Anal Methods Chem, vol. 2012: Department of Engineering, Science and Technology, Aarhus University, Blichers Allé 20, 8830 Tjele, Denmark., pp. 489239, 2012.
Link: http://dx.doi.org/10.1155/2012/489239
Abstract
Reduced sulfur compounds are considered to be important odorants from pig production due to their low odor threshold values and low solubility in slurry. The objective of the present study was to investigate the use of a portable method with a single silica gel column for trapping/separation coupled with chemiluminescence detection (SCTS-CL) for measurement of methanethiol and dimethyl sulfide in sample air from pig production. Proton-transfer-reaction mass spectrometry (PTR-MS) was used to evaluate the trapping/separation. The silica gel column used for the SCTS-CL efficiently collected hydrogen sulfide, methanethiol and dimethyl sulfide. The measurement of methanethiol by SCTS-CL was clearly interfered by the high concentration of hydrogen sulfide found in pig production, and a removal of hydrogen sulfide was necessary to obtain reliable results. Air samples taken from a facility with growing-finishing pigs were analyzed by SCTS-CL, PTR-MS, and a gas chromatograph with sulfur chemiluminescence detection (GC-SCD) to evaluate the SCTS-CL. The difference between the concentrations of methanethiol and dimethyl sulfide measured with SCTS-CL, PTR-MS, and GC-SCD was below 10%. In conclusion, the SCTS-CL is a portable and low-cost alternative to the commercial methods that can be used to measure methanethiol and dimethyl sulfide in sample air from pig production.
[Aaltonen2012] Aaltonen, H., and , "Exchange of volatile organic compounds in the boreal forest floor", : Helsingin yliopisto, 2012.
Link: https://helda.helsinki.fi/handle/10138/37593
Abstract
Terrestrial ecosystems, mainly plants, emit large amounts of volatile organic compounds (VOCs) into the atmosphere. In addition to plants, VOCs also have less-known sources, such as soil. VOCs are a very diverse group of reactive compounds, including terpenoids, alcohols, aldehydes and ketones. Due to their high reactivity, VOCs take part in chemical reactions in the atmosphere and thus also affect Earth s radiation balance. In this study, chamber and snow gradient techniques for measuring boreal soil and forest floor VOC fluxes were developed. Spatial and temporal variability in fluxes was studied with year-round measurements in the field and the sources of boreal soil VOCs in the laboratory with fungal isolates. Determination of the compounds was performed mass spectrometrically. This study reveals that VOCs from soil are emitted by living roots, above- and belowground litter and microbes. The strongest source appears to be litter, in which both plant residuals and decomposers play a role in the emissions. Temperature and moisture are the most critical physical factors driving VOC fluxes. Since the environment in boreal forests undergoes strong seasonal changes, the VOC flux strength of the forest floor varies markedly during the year, being highest in spring and autumn. The high spatial heterogeneity of the forest floor was also clearly visible in VOC fluxes. The fluxes of trace gases (CO2, CH4 and N2O) from soil, which are also related to the soil biological activity and physical conditions, did not correlate with the VOC fluxes. Our results show that emissions of VOCs from the boreal forest floor accounts for as much as several tens of percent, depending on the season, of the total forest ecosystem VOC emissions. This can be utilized in air chemistry models, which are almost entirely lacking the below-canopy compartment.
[Tasin2012] Tasin, M., L. Cappellin, and F. Biasioli, "Fast direct injection mass-spectrometric characterization of stimuli for insect electrophysiology by proton transfer reaction-time of flight mass-spectrometry (PTR-ToF-MS).", Sensors (Basel), vol. 12, no. 4: IASMA Research and Innovation Centre, Fondazione Edmund Mach, San Michele all'Adige, Italy. marco.tasin@slu.se, pp. 4091–4104, 2012.
Link: http://dx.doi.org/10.3390/s120404091
Abstract
Electrophysiological techniques are used in insect neuroscience to measure the response of olfactory neurons to volatile odour stimuli. Widely used systems to deliver an olfactory stimulus to a test insect include airstream guided flow through glass cartridges loaded with a given volatile compound on a sorbent support. Precise measurement of the quantity of compound reaching the sensory organ of the test organism is an urgent task in insect electrophysiology. In this study we evaluated the performances of the recent realised proton transfer reaction-time of flight mass-spectrometry (PTR-ToF-MS) as a fast and selective gas sensor. In particular, we characterised the gas emission from cartridges loaded with a set of volatile compounds belonging to different chemical classes and commonly used in electrophysiological experiments. PTR-ToF-MS allowed a fast monitoring of all investigated compounds with sufficient sensitivity and time resolution. The detection and the quantification of air contaminants and solvent or synthetic standards impurities allowed a precise quantification of the stimulus exiting the cartridge. The outcome of this study was twofold: on one hand we showed that PTR-ToF-MS allows monitoring fast processes with high sensitivity by real time detection of a broad number of compounds; on the other hand we provided a tool to solve an important issue in insect electrophysiology.
[Sulzer2012c] Sulzer, P., A. Edtbauer, E. Hartungen, S. Juerschik, A. Jordan, G. Hanel, S. Feil, S. Jaksch, L. Märk, and T. D. Märk, "From conventional proton-transfer-reaction mass spectrometry (PTR-MS) to universal trace gas analysis", International Journal of Mass Spectrometry, vol. 321: Elsevier, pp. 66–70, 2012.
Link: http://www.sciencedirect.com/science/article/pii/S1387380612001704
Abstract
We present here a slightly modified PTR-MS instrument that is not only capable to ionize trace compounds in air via proton-transfer-reactions (PTR) but is also able to ionize via charge-transfer-reactions (CTR) with help of reagent ions (Kr+ in particular) possessing higher ionization energies than common air constituents. This means that with minor adaptations a common PTR-MS instrument can be used for the analysis of nearly all available substance classes by using both PTR and/or CTR ionization. Especially in environmental research, the field of application where PTR-MS is used most widely, now not only trace volatile organic compounds (benzene, toluene, etc.) but additionally also very important (inorganic) substances, such as CO, CO2, CH4, NOx, and SO2, can be detected and quantified with the same instrument. As all ionizing agents are produced in a hollow cathode discharge ion source with good purity no additional mass filter is needed for reagent ion selection (as in other analytical methods employed) and remaining reagent ion impurities can be clearly distinguished from isobaric sample compounds due to the high mass resolution of the time-of-flight mass spectrometer used in the present PTR-MS instrument (PTR-TOF 8000). We present data obtained with various gas standards ranging from a “classical” PTR-MS aromatics mixture to samples containing molecules possessing ionization energies all the way up to 14 eV (CO).
[Jardine2012] Jardine, K.., G.. A. Barron-Gafford, J.. P. Norman, L.. Abrell, R.. K. Monson, K.. T. Meyers, M.. Pavao-Zuckerman, K.. Dontsova, E.. Kleist, C.. Werner, et al., "Green leaf volatiles and oxygenated metabolite emission bursts from mesquite branches following light-dark transitions.", Photosynth Res, vol. 113, no. 1-3: The University of Arizona-Biosphere 2, P.O. Box 8746, Tucson, AZ 85738, USA. jardine@email.arizona.edu, pp. 321–333, Sep, 2012.
Link: http://dx.doi.org/10.1007/s11120-012-9746-5
Abstract
Green leaf volatiles (GLVs) are a diverse group of fatty acid-derived compounds emitted by all plants and are involved in a wide variety of developmental and stress-related biological functions. Recently, GLV emission bursts from leaves were reported following light-dark transitions and hypothesized to be related to the stress response while acetaldehyde bursts were hypothesized to be due to the 'pyruvate overflow' mechanism. In this study, branch emissions of GLVs and a group of oxygenated metabolites (acetaldehyde, ethanol, acetic acid, and acetone) derived from the pyruvate dehydrogenase (PDH) bypass pathway were quantified from mesquite plants following light-dark transitions using a coupled GC-MS, PTR-MS, and photosynthesis system. Within the first minute after darkening following a light period, large emission bursts of both C(5) and C(6) GLVs dominated by (Z)-3-hexen-1-yl acetate together with the PDH bypass metabolites are reported for the first time. We found that branches exposed to CO(2)-free air lacked significant GLV and PDH bypass bursts while O(2)-free atmospheres eliminated the GLV burst but stimulated the PDH bypass burst. A positive relationship was observed between photosynthetic activity prior to darkening and the magnitude of the GLV and PDH bursts. Photosynthesis under (13)CO(2) resulted in bursts with extensive labeling of acetaldehyde, ethanol, and the acetate but not the C(6)-alcohol moiety of (Z)-3-hexen-1-yl acetate. Our observations are consistent with (1) the "pyruvate overflow" mechanism with a fast turnover time (<1 h) as part of the PDH bypass pathway, which may contribute to the acetyl-CoA used for the acetate moiety of (Z)-3-hexen-1-yl acetate, and (2) a pool of fatty acids with a slow turnover time (>3 h) responsible for the C(6) alcohol moiety of (Z)-3-hexen-1-yl acetate via the 13-lipoxygenase pathway. We conclude that our non-invasive method may provide a new valuable in vivo tool for studies of acetyl-CoA and fatty acid metabolism in plants at a variety of spatial scales.
[Halbritter2012] Halbritter, S.., M.. Fedrigo, V.. Hoellriegl, W.. Szymczak, J.. M. Maier, A.. Ziegler, and M.. Hummel, "Human Breath Gas Analysis in the Screening of Gestational Diabetes Mellitus", DIABETES TECHNOLOGY & THERAPEUTICS, vol. 14, pp. 10, 2012.
Link: http://dx.doi.org/10.1089/dia.2012.0076
Abstract
{Background: We present a pilot study on the feasibility of the application and advantages of online, noninvasive breath gas analysis (BGA) by proton transfer reaction quadrupole mass spectrometry for the screening of gestational diabetes mellitus (GDM) in 52 pregnant women by means of an oral glucose tolerance test (OGTT). Subjects and Methods: We collected and identified samples of end-tidal breath gas from patients during OGTT. Time evolution parameters of challenge-responsive volatile organic compounds (VOCs) in human breath gas were estimated. Multivariate analysis of variance and permutation analysis were used to assess feasibility of BGA as a diagnostic tool for GDM. Results: Standard OGTT diagnosis identified pregnant women as having GDM (n = 8), impaired glucose tolerance (n = 12), and normal glucose tolerance (n = 32); a part of this latter group was further subdivided into a ''marginal'' group (n = 9) because of a marginal high 1-h or 2-h OGTT value. We observed that OGTT diagnosis (four metabolic groups) could be mapped into breath gas data. The time evolution of oxidation products of glucose and lipids, acetone metabolites, and thiols in breath gas after a glucose challenge was correlated with GDM diagnosis (P = 0.035). Furthermore, basal (fasting) values of dimethyl sulfide and values of methanol in breath gas were inversely correlated with phenotype characteristics such as homeostasis model assessment of insulin resistance index (R= -0.538; P = 0.0002
[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
[Cappellin2012b] Cappellin, L., E. Aprea, P. Granitto, R. Wehrens, C. Soukoulis, R. Viola, T. D. Märk, F. Gasperi, and F. Biasioli, "Linking GC-MS and PTR-TOF-MS fingerprints of food samples", Chemometrics and Intelligent Laboratory Systems, vol. 118, pp. 301 - 307, 2012.
Link: http://www.sciencedirect.com/science/article/pii/S0169743912001219
Abstract
Recently the first applications in food science and technology of the newly available volatile organic compound (VOC) detection technique proton transfer reaction�mass spectrometry, coupled with a time of flight mass analyzer (PTR-TOF-MS), have been published. In comparison with standard techniques such as GC-MS, PTR-TOF-MS has the remarkable advantage of being extremely fast but has the drawback that compound identification is more challenging and often not possible without further information. In order to better exploit and understand the analytical information entangled in the PTR-TOF-MS fingerprint and to link it with SPME/GC-MS analyses we employed two multivariate calibration methods, \{PLS\} and the more recent LASSO. We show that, while in some cases it is sufficient to consider a single PTR-TOF-MS peak in order to predict the intensity of a SPME/GC-MS peak, in general a multivariate approach is needed. We compare the performances of \{PLS\} and \{LASSO\} in terms of prediction capabilities and interpretability of the model coefficients and conclude that \{LASSO\} is more suitable for this problem. As case study, we compared \{GC\} and PTR-MS data for different matrices, namely olive oil and grana cheese.
[Andersen2012] Andersen, K. Barkve, M. J. Ã. ¸rgen Hansen, and A. Feilberg, "Minimisation of artefact formation of dimethyl disulphide during sampling and analysis of methanethiol in air using solid sorbent materials.", J Chromatogr A, vol. 1245: Applied Plasma Physics AS, Bedriftsveien 25, PO Box 584, 4305 Sandnes, Norway., pp. 24–31, Jul, 2012.
Link: http://dx.doi.org/10.1016/j.chroma.2012.05.020
Abstract
Methanethiol (MT) is a potent odorant that can be difficult to measure due to its high volatility and reactivity; it easily reacts to form dimethyl disulphide (DMDS) during sampling and/or analysis. This paper focuses on finding an optimal method for sampling and measuring MT with minimum artefact formation using sorbent materials and a thermal desorption-gas chromatography-mass spectrometry method (TD-GC-MS). Experiments were conducted to identify suitable sorbent materials and tubes for analysis. Breakthrough, desorption rate, the effects of storage and desorption temperatures were investigated and different drying methods were established with respect to quantitative sampling and formation of DMDS. Proton-transfer-reaction mass spectrometry (PTR-MS) was used in the development of the method and was an especially useful tool for determination of breakthrough. The results show that glass tubes packed with silica gel for pre-concentration of MT before analysis with TD-GC-MS give the best results. In addition, a combination of Tenax TA and carbonised molecular sieve or Tenax TA cooled to 0 °C gives acceptable results. 80 °C was found to be the optimal desorption temperature. For all the sampling methods tested, storage conditions were observed to be very critical for transformation of MT. Room temperature storage should be limited to few minutes and, in general, tubes should be kept at 0°C or lower during storage.
[King2012] King, J., K. Unterkofler, G. Teschl, S. Teschl, P. Mochalski, H. Koc, H. Hinterhuber, and A. Amann, "A modeling-based evaluation of isothermal rebreathing for breath gas analyses of highly soluble volatile organic compounds", Journal of breath research, vol. 6, no. 1: IOP Publishing, pp. 016005, 2012.
Link: http://iopscience.iop.org/1752-7163/6/1/016005
Abstract
Isothermal rebreathing has been proposed as an experimental technique for estimating the alveolar levels of hydrophilic volatile organic compounds (VOCs) in exhaled breath. Using the prototypic test compounds acetone and methanol, we demonstrate that the end-tidal breath profiles of such substances during isothermal rebreathing show a characteristic increase that contradicts the conventional pulmonary inert gas elimination theory due to Farhi. On the other hand, these profiles can reliably be captured by virtue of a previously developed mathematical model for the general exhalation kinetics of highly soluble, blood-borne VOCs, which explicitly takes into account airway gas exchange as a major determinant of the observable breath output. This model allows for a mechanistic analysis of various rebreathing protocols suggested in the literature. In particular, it predicts that the end-exhaled levels of acetone and methanol measured during free tidal breathing will underestimate the underlying alveolar concentration by a factor of up to 1.5. Moreover, it clarifies the discrepancies between in vitro and in vivo blood–breath ratios of hydrophilic VOCs and yields further quantitative insights into the physiological components of isothermal rebreathing and highly soluble gas exchange in general.

Pages

Featured Articles

Download Contributions to the International Conference on Proton Transfer Reaction Mass Spectrometry and Its Applications:

 

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).
Link

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.
Link

 

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

 

Download the latest version of the IONICON publication database as BibTeX.