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Found 777 results
Title [ Year(Desc)]
2004
[Biasioli2004b] Biasioli, F., F. Gasperi, D. Mott, E. Aprea, F. Marini, and TD. Maerk, "Characterization of Strawberry Genotypes by PTR-MS Spectral Fingerprinting: a Three Year Study", V International Strawberry Symposium 708, pp. 497–500, 2004.
Link: http://www.actahort.org/books/708/708_87.htm
Abstract
Proton Transfer Reaction Mass Spectrometry (PTR-MS) fingerprinting has been used to accurately and rapidly identify the cultivar of single intact strawberry fruits. The technique has been applied in a 3-cultivar experiment with 70 fruits harvested in 2002, 2003 and 2004. The proposed models correctly predicted the cultivar. Cross-validation tests verified 100% correct classification. The data indicated the possibility of correctly characterizing single fruit by fast non-invasive measurements without any pre-treatment and/or concentration of the headspace gas mixture. This is a necessary preliminary step in view of correlation studies of PTR-MS data with genetics and other characterization of fruits, in particular, sensory analysis. Extension to more cultivars is envisaged.
[Boscaini2004] Boscaini, E., T. Mikoviny, A. Wisthaler, E. von Hartungen, and T. D. Märk, "Characterization of wine with PTR-MS", International Journal of Mass Spectrometry, vol. 239, no. 2: Elsevier, pp. 215–219, 2004.
Link: http://www.sciencedirect.com/science/article/pii/S1387380604003537
Abstract
A new method for measuring volatile profiles of alcoholic beverages (or other ethanol-containing analytes such as perfumes or herbs) has been developed. The method is based on proton transfer reaction mass spectrometry (PTR-MS). However, instead of hydronium ions (H3O+) protonated ethanol clusters (C2H5OH2+(C2H5OH)n = 1,2) are used as chemical ionization reagent ions. A stable reagent ion distribution is obtained by a 10-fold dilution of analyte headspace into ethanol-saturated nitrogen. Samples with different ethanol content can thus be directly compared. Characteristic mass spectral fingerprints have been obtained for four wine varieties. Principal component analysis discriminates between different wine varieties and shows specific correlations between wine variety and selected ions.
[Christian2004] Christian, TJ., B. Kleiss, RJ. Yokelson, R. Holzinger, PJ. Crutzen, WM. Hao, T. Shirai, and DR. Blake, "Comprehensive laboratory measurements of biomass-burning emissions: 2. First intercomparison of open-path FTIR, PTR-MS, and GC-MS/FID/ECD", Journal of geophysical research, vol. 109, no. D2: American Geophysical Union, pp. D02311, 2004.
Link: http://www.agu.org/pubs/crossref/2004/2003JD003874.shtml
Abstract
Oxygenated volatile organic compounds (OVOC) can dominate atmospheric organic chemistry, but they are difficult to measure reliably at low levels in complex mixtures. Several techniques that have been used to speciate nonmethane organic compounds (NMOC) including OVOC were codeployed/intercompared in well-mixed smoke generated by 47 fires in the U.S. Department of Agriculture Forest Service Fire Sciences Combustion Facility. The agreement between proton transfer reaction mass spectrometry (PTR-MS) and open-path Fourier transform infrared spectroscopy (OP-FTIR) was excellent for methanol (PT/FT = 1.04 ± 0.118) and good on average for phenol (0.843 ± 0.845) and acetol (∼0.81). The sum of OP-FTIR mixing ratios for acetic acid and glycolaldehyde agreed (within experimental uncertainty) with the PTR-MS mixing ratios for protonated mass 61 (PT/FT = 1.17 ± 0.34), and the sum of OP-FTIR mixing ratios for furan and isoprene agreed with the PTR-MS mixing ratios for protonated mass 69 (PT/FT = 0.783 ± 0.465). The sum of OP-FTIR mixing ratios for acetone and methylvinylether accounted for most of the PTR-MS protonated mass 59 signal (PT/FT = 1.29 ± 0.81), suggesting that one of these compounds was underestimated by OP-FTIR or that it failed to detect other compounds that could contribute at mass 59. Canister grab sampling followed by gas chromatography (GC) with mass spectrometry (MS), flame ionization detection (FID), and electron capture detection (ECD) analysis by two different groups agreed well with OP-FTIR for ethylene, acetylene, and propylene. However, these propylene levels were below those observed by PTR-MS (PT/FT = 2.33 ± 0.89). Good average agreement between PTR-MS and GC was obtained for benzene and toluene. At mixing ratios above a few parts per billion the OP-FTIR had advantages for measuring sticky compounds (e.g., ammonia and formic acid) or compounds with low proton affinity (e.g., hydrogen cyanide and formaldehyde). Even at these levels, only the PTR-MS measured acetonitrile and acetaldehyde. Below a few ppbv only the PTR-MS measured a variety of OVOC, but the possibility of fragmentation, interference, and sampling losses must be considered.
[Schnitzler2004] SCHNITZLER, JÖRG-PETER., M. Graus, J. Kreuzwieser, U. Heizmann, H. Rennenberg, A. Wisthaler, and A. Hansel, "Contribution of different carbon sources to isoprene biosynthesis in poplar leaves", Plant Physiology, vol. 135, no. 1: Am Soc Plant Biol, pp. 152–160, 2004.
Link: http://www.plantphysiol.org/content/135/1/152.short
Abstract
This study was performed to test if alternative carbon sources besides recently photosynthetically fixed CO2 are used for isoprene formation in the leaves of young poplar (Populus × canescens) trees. In a 13CO2 atmosphere under steady state conditions, only about 75% of isoprene became 13C labeled within minutes. A considerable part of the unlabeled carbon may be derived from xylem transported carbohydrates, as may be shown by feeding leaves with [U-13C]Glc. As a consequence of this treatment approximately 8% to 10% of the carbon emitted as isoprene was 13C labeled. In order to identify further carbon sources, poplar leaves were depleted of leaf internal carbon pools and the carbon pools were refilled with 13C labeled carbon by exposure to 13CO2. Results from this treatment showed that about 30% of isoprene carbon became 13C labeled, clearly suggesting that, in addition to xylem transported carbon and CO2, leaf internal carbon pools, e.g. starch, are used for isoprene formation. This use was even increased when net assimilation was reduced, for example by abscisic acid application. The data provide clear evidence of a dynamic exchange of carbon between different cellular precursors for isoprene biosynthesis, and an increasing importance of these alternative carbon pools under conditions of limited photosynthesis. Feeding [1,2-13C]Glc and [3-13C]Glc to leaves via the xylem suggested that alternative carbon sources are probably derived from cytosolic pyruvate/phosphoenolpyruvate equivalents and incorporated into isoprene according to the predicted cleavage of the 3-C position of pyruvate during the initial step of the plastidic deoxyxylulose-5-phosphate pathway.
[LaPorta2004] La Porta, N., F. Biasioli, F. Gasperi, and T. D. Märk, "Discrimination of Heterobasidion annosum ISGs by evaluation of volatile organic compounds", S. Michele all'Adige, Italy, vol. 27, no. 8, pp. 379–382, 2004.
Link: http://core.kmi.open.ac.uk/download/pdf/2835560#page=418
Abstract
Heterobasidion annosum represents one of the most dangerous fungi in the conifer forest of the boreal hemisphere. This fungus was differentiated into three biological species (Intersterile groups; ISGs) characterized by different host specificity, patogenicity and distribution. A fast and easy identification of the ISG has important consequences on the silvicultural decition making. However, the determination of the ISG from the morphological traits of fruit bodies or, least of all, from mycelium is usually not easy. Proton Transfer Reaction – Mass Spectrometry (PTR-MS) is a new technique proposed and realised by the University of Innsbruck, and now issued also to the market. This technique allows high performance on-line measurements for a large number of VOCs. The aim of this work was to verify the possibility to discriminate the H. annosum ISGs based on their volatile compound emission and to identify putative characteristic masses that may play an important role in the host specificity and in the specific antagonistic fungi among each ISGs. Twelve strains belong to the three ISGs (here idicated by F, P and S) were analysed by PTRMS fingerprinting. P ISG was definitely separated from F and S ISGs. In addition, several masses show to be significantly different among the three ISGs. ANOVA on PTR-MS peak values identified 16 significant masses out of 230. Applications and limitations of this approach are discussed.
[Grabmer2004] Grabmer, W., M. Graus, C. Lindinger, A. Wisthaler, B. Rappenglück, R. Steinbrecher, and A. Hansel, "Disjunct eddy covariance measurements of monoterpene fluxes from a Norway spruce forest using PTR-MS", International Journal of Mass Spectrometry, vol. 239, no. 2: Elsevier, pp. 111–115, 2004.
Link: http://www.sciencedirect.com/science/article/pii/S1387380604003914
Abstract
Interest in reliable quantification of organic trace compounds released from terrestrial ecosystems stems from their impact on oxidant levels such as ozone and hydroxyl radicals and on secondary organic aerosol formation. In an attempt to quantify these emissions, a disjunct sampler (DS) was coupled to a PTR-MS instrument. In the disjunct eddy covariance (DEC) technique, an instantaneous grab sample is taken at intervals of tens of seconds and vertical wind speed is recorded at the instant of sample collection. The intermittent periods are used for sample analysis by a moderately fast chemical sensor, in this case a PTR-MS instrument, which allows for fast and sensitive detection of biogenic volatile organic compounds. The vertical turbulent transport of a trace compound is then calculated from the covariance of the fluctuations in vertical wind speed and compound mixing ratio. Fluxes of monoterpenes from a Norway spruce forest were measured during the 2002 summer intensive field campaign of BEWA2000 and results compared well with data obtained using relaxed eddy accumulation (REA) and the enclosure approach. In addition to this field experiment, a laboratory test was carried out to validate the disjunct sampling procedure.
[Jaksch2004] Jaksch, D., R. Margesin, T. Mikoviny, JD. Skalny, E. Hartungen, F. Schinner, NJ. Mason, and TD. Märk, "The effect of ozone treatment on the microbial contamination of pork meat measured by detecting the emissions using PTR-MS and by enumeration of microorganisms", International Journal of Mass Spectrometry, vol. 239, no. 2: Elsevier, pp. 209–214, 2004.
Link: http://www.sciencedirect.com/science/article/pii/S1387380604003471
Abstract
In this paper, we report the results of treating commercial samples of pork meat with ozone in order to determine whether such treatment reduces microbial growth and hence extends the shelf lifetime of such products. The technique of Proton-Transfer-Reaction Mass Spectrometry (PTR-MS) was used to study volatile emissions with the signal detected at mass 63 (assumed to be a measure for dimethylsulphide) being used as a diagnostic of bacterial activity. Such a signal was found to strongly increase with time for an untreated meat sample whereas ozone-treated meat samples showed much reduced emissions—suggesting that the microbial activity had been greatly suppressed by ozone treatment. An independent analysis, however, revealed that microbial counts were very high, independent of the treatment.
[Tani2004] Tani, A., S. Hayward, A. Hansel, and N. C Hewitt, "Effect of water vapour pressure on monoterpene measurements using proton transfer reaction-mass spectrometry (PTR-MS)", International Journal of Mass Spectrometry, vol. 239, no. 2: Elsevier, pp. 161–169, 2004.
Link: http://www.sciencedirect.com/science/article/pii/S1387380604003495
Abstract
The effects of water vapour pressure (WVP) on the fragmentation of seven monoterpene and related C10 volatile organic compounds (VOCs) in the drift tube of a proton transfer reaction-mass spectrometer (PTR-MS) were investigated. In addition, the combined effects of varying WVP and the ratios of electric field strength to number density of the buffer gas (E/N) were investigated in detail for three of these compounds, the monoterpenes α-pinene and sabinene plus the related C10 VOC p-cymene. Under normal operating conditions (E/N = 124 Td), WVP affected the fragment patterns of all compounds with the exception of β-pinene and the three oxygenated C10 VOCs. WVP had a significant effect on the fragment patterns of α-pinene and sabinene at the lower E/N ratios (around 80 Td) but had little effect on fragmentation towards the higher E/N ratios used here (∼142 Td). On the other hand, p-cymene fragmentation was most affected by WVP under normal operating conditions. PTR-MS sensitivity towards the three compounds was also considered under three conditions where reaction was assumed with (1) H3O+ only; (2) H3O+ and H3O+H2O; and (3) H3O+, H3O+H2O and H3O+(H2O)2. Our results indicate that α-pinene and sabinene react not only with H3O+ and H3O+H2O via direct proton transfer but also with H3O+(H2O)2 via ligand switching. p-Cymene seems to react only with H3O+ via direct proton transfer and with H3O+H2O via ligand switching. It is speculated that the WVP effect on fragmentation results from the differing abundances of hydrated reagent ions which causes different frequencies of individual reactions to occur, thus, determining how ‘soft’ the overall reaction is. These results also indicate that under normal conditions, a correction should be made for WVP if the concentration of p-cymene in air samples is to be determined from the single ion signal of either protonated molecular ions or the most dominant fragment ions.
[Northway2004] Northway, MJ., JA. De Gouw, DW. Fahey, RS. Gao, C. Warneke, JM. Roberts, and F. Flocke, "Evaluation of the role of heterogeneous oxidation of alkenes in the detection of atmospheric acetaldehyde", Atmospheric Environment, vol. 38, no. 35: Elsevier, pp. 6017–6028, 2004.
Link: http://www.sciencedirect.com/science/article/pii/S1352231004006429
Abstract
Unexpectedly high values for acetaldehyde have been observed in airborne measurements using a proton-transfer-reaction mass spectrometry instrument. The acetaldehyde values increase with increasing ambient ozone levels with a ratio up to 5 pptv acetaldehyde per ppbv of ozone in the free troposphere. The elevated values of acetaldehyde cannot easily be explained from known tropospheric chemistry. Here, we investigate the possibility that the elevated acetaldehyde signals are due to a sampling artifact. Laboratory experiments show that the elevated signals are not due to changes of the ion chemistry in the instrument, or from the instrument materials reacting with ozone. The heterogeneous oxidation of a number of unsaturated organic compounds is investigated as a possible source for a chemical artifact produced in the instrument inlet. The products of the heterogeneous reactions are consistent with gas phase chemistry, and the ozonolysis of some alkenes does produce acetaldehyde when they have the appropriate hydrocarbon structure. The amount of reactive material in the free troposphere expected to accumulate in the aircraft inlet is unknown, and the exact origin of reactive compounds that contribute to the artifact production remains unresolved.
[Karl2004] Karl, T., M. Potosnak, A. Guenther, D. Clark, J. Walker, J. D. Herrick, and C. Geron, "Exchange processes of volatile organic compounds above a tropical rain forest: Implications for modeling tropospheric chemistry above dense vegetation", Journal of geophysical research, vol. 109, no. D18: American Geophysical Union, pp. D18306, 2004.
Link: http://www.agu.org/pubs/crossref/2004/2004JD004738.shtml
Abstract
Disjunct eddy covariance in conjunction with continuous in-canopy gradient measurements allowed for the first time to quantify the fine-scale source and sink distribution of some of the most abundant biogenic (isoprene, monoterpenes, methanol, acetaldehyde, and acetone) and photooxidized (MVK+MAC, acetone, acetaldehyde, acetic, and formic acid) VOCs in an old growth tropical rain forest. Our measurements revealed substantial isoprene emissions (up to 2.50 mg m−2 h−1) and light-dependent monoterpene emissions (up to 0.33 mg m−2 h−1) at the peak of the dry season (April and May 2003). Oxygenated species such as methanol, acetone, and acetaldehyde were typically emitted during daytime with net fluxes up to 0.50, 0.36, and 0.20 mg m−2 h−1, respectively. When generalized for tropical rain forests, these fluxes would add up to a total emission of 36, 16, 19, 106, and 7.2 Tg/yr for methanol, acetaldehyde, acetone, isoprene, and monoterpenes, respectively. During nighttime we observed strong sinks for oxygenated and nitrogen-containing compounds such as methanol, acetone, acetaldehyde, MVK+MAC, and acetonitrile with deposition velocities close to the aerodynamic limit. This suggests that the canopy resistance (Rc) is very small and not the rate-limiting step for the nighttime deposition of many VOCs. Our measured mean dry deposition velocities of methanol, acetone, acetaldehyde, MVK+MAC, and acetonitrile were a factor 10–20 higher than estimated from traditional deposition models. If our measurements are generalized, this could have important implications for the redistribution of VOCs in atmospheric chemistry models. Our observations indicate that the current understanding of reactive carbon exchange can only be seen as a first-order approximation.
[Yeretzian2004] Yeretzian, C., P. Pollien, C. Lindinger, and S. Ali, "Individualization of Flavor Preferences: Toward a Consumer-centric and Individualized Aroma Science", Comprehensive Reviews in food science and food safety, vol. 3, no. 4: Wiley Online Library, pp. 152–159, 2004.
Link: http://onlinelibrary.wiley.com/doi/10.1111/j.1541-4337.2004.tb00066.x/abstract
Abstract
Personal dietary choices are largely based on flavor preferences. Thus understanding individual flavor perception and preference is vital to understanding the basis of human diet selection. We have developed novel tools to measure in real time and at an individual level volatile aroma compounds delivered breath-by-breath to the nose while eating and drinking. The same food may deliver different aromas to different people, due the specificities of their in-mouth environment (inter-individual differences). Moreover, a person may eat a given food in a different manner, leading to variations in the aroma profile reaching the nose (intra-individual differences). Understanding the basis of these differences opens the door to an individualized aroma science and the road to delivering nutritional value and health through products consumers prefer. The challenge to the food industry is to align what the consumer wants with what the consumer needs, delivering nutritional value and health through products they prefer.
[Ruth2004] van Ruth, S. M., and K. Buhr, "Influence of mastication rate on dynamic flavour release analysed by combined model mouth/proton transfer reaction–mass spectrometry", International Journal of Mass Spectrometry, vol. 239, no. 2: Elsevier, pp. 187–192, 2004.
Link: http://www.sciencedirect.com/science/article/pii/S1387380604003562
Abstract
The influence of mastication rate on the dynamic release of seven volatile flavour compounds from sunflower oil was evaluated by combined model mouth/proton transfer reaction–mass spectrometry (PTR–MS). Air/oil partition coefficients were measured by static headspace gas chromatography. The dynamic release of the seven volatile flavour compounds from sunflower oil was significantly affected by the compounds’ hydrophobicity and the mastication rate employed in the model mouth. The more hydrophobic compounds were released at a higher rate than their hydrophilic counterparts. Increase in mastication rate increased the maximum concentration measured by 36% on average, and the time to reach this maximum by 35% on average. Mastication affected particularly the release of the hydrophilic compounds. The maximum concentration of the compounds correlated significantly with the compounds’ air/oil partition coefficients. The initial release rates over the first 15 s were affected by the type of compound, but not by the mastication rate. During the course of release, the proportions of the hydrophilic compounds to the overall flavour mixture in air decreased. The contribution of the hydrophobic compounds increased. Higher mastication rates, however, increased the proportions of the hydrophilic compounds and decreased those of the hydrophobic compounds.
[Mei2004] Mei, J. B., G. A. Reineccius, B. W Knighton, and E. P. Grimsrud, "Influence of strawberry yogurt composition on aroma release", Journal of agricultural and food chemistry, vol. 52, no. 20: ACS Publications, pp. 6267–6270, 2004.
Link: http://pubs.acs.org/doi/abs/10.1021/jf049787t
Abstract
The primary objective of this study was to determine how yogurt ingredients affect aroma release in the mouth during eating. A model strawberry flavor consisting of ethyl butanoate, ethyl 3-methylbutanoate, (Z)-hex-3-enol, 2-methylbutanoic acid, 5-hexylhydro-2(3H)-furanone, and 3-methyl-3-phenylglycidic acid ethyl ester was added to unflavored, unsweetened yogurt that had different added sweeteners and hydrocolloids. In all, 12 yogurt formulations were examined to determine the effects of gelatin, modified food starch, pectin, sucrose, high-fructose corn syrup, and aspartame on aroma release. Aroma release was monitored by breath-by-breath analysis (proton-transfer reaction−mass spectrometry) during eating of the test yogurts. Results showed aroma release of the ethyl butanoate, (Z)-hex-3-enol, and ethyl 3-methylbutanoate to be suppressed by sweeteners, with 55 DE high-fructose corn syrup having the greatest effect. Addition of thickening agents had no significant effect on the aroma release profiles of the compounds under study.
[Gouw2004] de Gouw, J., C. Warneke, R. Holzinger, T. Klüpfel, and J. Williams, "Inter-comparison between airborne measurements of methanol, acetonitrile and acetone using two differently configured PTR-MS instruments", International Journal of Mass Spectrometry, vol. 239, no. 2: Elsevier, pp. 129–137, 2004.
Link: http://www.sciencedirect.com/science/article/pii/S1387380604003513
Abstract
Proton-transfer-reaction mass spectrometry (PTR-MS) has emerged as a useful tool to study the atmospheric chemistry of volatile organic compounds (VOCs). The technique combines a fast response time with a low detection limit, and allows atmospheric measurements of many important VOCs and their oxidation products. Here, we inter-compare the results obtained with two differently configured PTR-MS instruments operated onboard a Falcon aircraft during the Mediterranean Intensive Oxidants Study (MINOS) campaign in the Mediterranean region. One PTR-MS was operated at a drift tube pressure of 2.3 mbar and an electric field divided by gas number density value (E/N) of 120 Td for the detection of VOCs and aromatic hydrocarbons. The other PTR-MS was operated at an increased pressure of 2.8 mbar and a reduced E/N of 97 Td for the detection of peroxyacetyl nitrate (PAN). As a consequence, more H3O+(H2O)n cluster ions were present in the drift tube, which undergo proton-transfer reactions with VOCs similar to H3O+ ions. The results for methanol (CH3OH), acetonitrile (CH3CN) and acetone (CH3COCH3) obtained with the instruments compared very well. The agreement between the two results was relatively independent of the ambient mixing ratio of water, which influences the H3O+(H2O)n cluster ion distribution, and of ozone, which has been implicated in the artificial formation of aldehydes and ketones.
[Kuster2004] Kuster, W.. C., B.. T. Jobson, T.. Karl, D.. Riemer, E.. Apel, P.. D. Goldan, and F.. C. Fehsenfeld, "Intercomparison of volatile organic carbon measurement techniques and data at La Porte during the TexAQS2000 Air Quality Study.", Environ Sci Technol, vol. 38, no. 1: Aeronomy Laboratory, National Oceanic and Atmospheric Administration, R/AL7, 325 Broadway, Boulder, Colorado 80305, USA. bkuster@al.noaa.gov, pp. 221–228, Jan, 2004.
Link: http://pubs.acs.org/doi/abs/10.1021/es034710r
Abstract
The Texas Air Quality Study 2000 (TexAQS2000) investigated the photochemical production of ozone and the chemistry of related precursors and reaction products in the vicinity of Houston, TX. The colocation of four instruments for the measurement of volatile organic carbon compounds (VOCs) allowed a unique opportunity for the intercomparison of the different in-situ measuring techniques. The instruments included three gas chromatographs, each with a different type of detector, and a Proton-Transfer-Reaction Mass Spectrometer (PTR-MS) with each system designed to measure a different suite of VOCs. Correlation plots and correlation statistics are presented for species measured by more than one of these instruments. The GC instruments were all in agreement to within 10-20% (slope) with coefficients of variation (r2) of > or = 0.85. The PTR-MS agreement with other instruments was more dependent on species with some very good agreements (r2 values of approximately 0.95 for some aromatics), but isoprene, acetaldehyde and propene were substantially less highly correlated (0.55 < r2 < 0.80). At least part of these differences were undoubtedly due to the timing of sample acquisition in an environment in which VOC levels changed very rapidly on both quantitative and temporal scales.
[Boscaini2004a] Boscaini, E., M. L. Alexander, P. Prazeller, and T. D. Märk, "Investigation of fundamental physical properties of a polydimethylsiloxane (PDMS) membrane using a proton transfer reaction mass spectrometer (PTRMS)", International Journal of Mass Spectrometry, vol. 239, no. 2: Elsevier, pp. 179–186, 2004.
Link: http://www.sciencedirect.com/science/article/pii/S1387380604003586
Abstract
A membrane introduction proton transfer reaction mass spectrometer (MI-PTRMS) has been employed for the characterisation of a polydimethylsiloxane (PDMS) membrane. For this purpose the diffusion and partition coefficients (which serve as a measure for solubility) have been determined experimentally for different classes of chemical compounds both non-polar and polar species, i.e., aromatics, alcohols, and ketones. It turned out that not only polar compounds exhibit strong interaction with a hydrophobic membrane such as the PDMS, but also non-polar compounds as trimethylbenzene or propylbenzene show strong interaction with a PDMS membrane. Stronger analyte–membrane interaction leads to a slower diffusion coefficient and larger partition coefficient. The effect of the temperature on the diffusion coefficient and partition coefficient has also been investigated, i.e., at higher temperature diffusion becomes faster and solubility lower. Permeability can be calculated from diffusion and partition coefficients and the activation energy has been derived from corresponding Arrhenius plots. The MI-PTRMS system shows detection limits in the order of tens of pptv and its response is linear for more than four orders of magnitude.
[Williams2004] Williams, J., R. Holzinger, V. Gros, X. Xu, E. Atlas, and D. W. R. Wallace, "Measurements of organic species in air and seawater from the tropical Atlantic", Geophysical research letters, vol. 31, no. 23: Wiley Online Library, 2004.
Link: http://onlinelibrary.wiley.com/doi/10.1029/2004GL020012/full
Abstract
A West -East crossing of the Tropical Atlantic during Meteor cruise 55 included measurements of organic species within the atmospheric marine boundary layer and the upper ocean. Acetone, methanol, acetonitrile and DMS were measured between 10–0°N and 35°W–5°E, on either side of the ITCZ. Methanol and acetone concentrations were higher in the northern hemisphere, both in surface seawater and the atmosphere whereas acetonitrile and DMS showed no significant interhemispheric gradient. Three depth profiles from 0–200 m for these species were measured. Acetone, methanol, DMS and acetonitrile generally decreased with depth with the sharpest decrease in concentration in all profiles being found at the bottom of the mixed layer. The average air mixing ratios and surface seawater concentrations for the whole dataset are respectively: acetone 0.53 nmol/mol and 17.6 nmol/L; acetonitrile 0.11 nmol/mol and 6.19 nmol/L; methanol 0.89 nmol/mol and 118.4 nmol/L; and DMS 0.05 nmol/mol and 1.66 nmol/L.
[Boscaini2004b] Boscaini, E., M. L. Alexander, P. Prazeller, and T. D. Märk, "Membrane inlet proton transfer reaction mass spectrometry (MI-PTRMS) for direct measurements of VOCs in water", International Journal of Mass Spectrometry, vol. 239, no. 2: Elsevier, pp. 171–177, 2004.
Link: http://www.sciencedirect.com/science/article/pii/S1387380604003896
Abstract
The use of a membrane inlet proton transfer reaction mass spectrometry (MI-PTRMS) system was investigated for the quantitative analysis of VOCs directly from water. Compounds playing an important role in environmental, biological and health issues such as methanol, acetonitrile, acetone, dimethylsulfide (DMS), isoprene, benzene, and toluene have been analyzed both in fresh and salty water. The system shows very good sensitivity, reproducibility, and a linear response of up to five orders of magnitude. The detection limit for DMS is about 100 ppt and for methanol is about 10 ppb both in fresh and salty water. The response time of the various compounds across the membrane is on the order of a few minutes. This fast response and the fact that the PTRMS can perform absolute measurements without the necessity of calibration make the system suitable for on-line and -site measurements of VOCs directly from water.
[Roberts2004] Roberts, DD., P. Pollien, C. Yeretzian, C. Lindinger, KD. Deibler, J. Delwiche, and , "Nosespace analysis with proton-transfer-reaction mass spectrometry: intra-and interpersonal variability", Handbook of flavor characterization: sensory analysis, chemistry, and physiology, vol. -, pp. 151–162, 2004.
Link: http://www.crcnetbase.com/doi/abs/10.1201/9780203912812.ch10
[Hayward2004] Hayward, S., A. Tani, S. M. Owen, and N. C Hewitt, "Online analysis of volatile organic compound emissions from Sitka spruce (Picea sitchensis).", Tree Physiol, vol. 24, no. 7: Institute of Environmental and Natural Sciences, Lancaster University, Lancaster, LA1 4YQ, U.K., pp. 721–728, Jul, 2004.
Link: http://treephys.oxfordjournals.org/content/24/7/721.short
Abstract
Volatile organic compound (VOC) emissions from Sitka spruce (Picea sitchensis Bong.) growing in a range of controlled light and temperature regimes were monitored online with a proton transfer reaction-mass spectrometer (PTR-MS) operating at a temporal resolution of approximately 1 min. Isoprene emissions accounted for an average of more than 70% of measured VOCs and up to 3.5% of assimilated carbon. Emission rates (E) for isoprene correlated closely with photosynthetic photon flux (PPF) and temperature, showing saturation at a PPF of between 300 and 400 micromol m(-2) s(-1) and a maximum between 35 and 38 degrees C. Under standard conditions of 30 degrees C and 1000 micromol m(-2) s(-1) PPF, the mean isoprene E was 13 microg gdm(-1) h(-1), considerably higher than previously observed in this species. Mean E for acetaldehyde, methanol and monoterpenes at 30 degrees C were 0.37, 0.78 and 2.97 microg gdm(-1) h(-1), respectively. In response to a sudden light to dark transition, isoprene E decreased exponentially by > 98% over about 3 h; however, during the first 7 min, this otherwise steady decay was temporarily but immediately depressed to approximately 40% of the pre-darkness rate, before rallying during the following 7 min to rejoin the general downward trajectory of the exponential decay. The sudden sharp fall in isoprene E was mirrored by a burst in acetaldehyde E. The acetaldehyde E maximum coincided with the isoprene E minimum (7 min post-illumination), and ceased when isoprene emissions resumed their exponential decay. The causes of, and linkages between, these phenomena were investigated.
[Schade2004] Schade, G. W., and T. G. Custer, "OVOC emissions from agricultural soil in northern Germany during the 2003 European heat wave", Atmospheric Environment, vol. 38, no. 36: Elsevier, pp. 6105–6114, 2004.
Link: http://www.sciencedirect.com/science/article/pii/S1352231004007344
Abstract
Fluxes of methanol and acetone were measured from an agricultural field plot during one of the hottest weeks of the heat wave of the summer of 2003 in Europe. Significant positive fluxes from the bare, plowed soil for these oxygenated volatile organic compounds were found. Methanol fluxes ranged from 0 to 0.20 mg C m−2 h−1 while acetone fluxes ranged from −0.01 to 0.05. Mixing ratios for both methanol and acetone showed significant increases at night, consistent with a ground-based emission source for both the compounds. Methanol emissions were well correlated with sensible heat flux, peaking around noon. Assuming abiological production from soil organic matter in the topsoil, we calculate that 48 kJ mol−1 of energy is required to liberate the methanol from the topsoil. In contrast to methanol, acetone fluxes were not correlated with any measured meteorological parameter. This suggests that acetone has another source and may be produced in the soil subsurface, possibly through biological or moisture-driven processes. Using the flux data, we also simulated relaxed eddy accumulation (REA) experiments and reconfirm that sonic temperature can be used to calculate b-factors for REA analysis of a variety of trace gas fluxes.
[Steinbacher2004] Steinbacher, M., J. Dommen, C. Ammann, C. Spirig, A. Neftel, and ASH. Prevot, "Performance characteristics of a proton-transfer-reaction mass spectrometer (PTR-MS) derived from laboratory and field measurements", International Journal of Mass Spectrometry, vol. 239, no. 2: Elsevier, pp. 117–128, 2004.
Link: http://www.sciencedirect.com/science/article/pii/S1387380604003434
Abstract
Volatile organic compounds (VOCs) play an important role in the formation of ozone and aerosols in the atmosphere. In an increasing number of field campaigns the proton-transfer-reaction mass spectrometer (PTR-MS) has proven to be a useful and fast tool for measuring VOCs and studying the relevant atmospheric processes. This work describes laboratory and field measurements with two different versions of the PTR-MS and presents important instrument specific features. The temperature stabilization and the change of the gasket material in the newer version significantly improved the performance of the instrument, as demonstrated by periodical background measurements under field conditions. The investigation of the mass discrimination illustrated the necessity of an elaborate verification. The humidity dependence of benzene was substantially lower than in former studies, which used higher drift tube pressures, but it is still higher than predicted by a simple dimer/monomer equilibrium model. An instrument comparison with a fluorescent technique was performed for formaldehyde and showed differences between pure formaldehyde calibration gases and complex ambient air samples. An intercomparison of two PTR-MSs measuring ambient air yielded satisfactory results after calibration for most of the considered masses. Comparing PTR-MS and gas chromatograph measurements of aromatic compounds, revealed a good agreement for conditions of fresh anthropogenic emissions. In photochemically aged air, many masses detected by the PTR-MS are not only influenced by anthropogenically and biogenically emitted but also oxidized VOCs.
[Hansel2004] Hansel, A., "Proton transfer mass spectrometer", europhysics news, vol. 35, no. 6, pp. 197–199, 2004.
Link: http://www.europhysicsnews.org/articles/epn/pdf/2004/06/epn04606.pdf
[Critchley2004] Critchley, A., TS. Elliott, G. Harrison, CA. Mayhew, JM. Thompson, and T. Worthington, "The proton transfer reaction mass spectrometer and its use in medical science: applications to drug assays and the monitoring of bacteria", International Journal of Mass Spectrometry, vol. 239, no. 2: Elsevier, pp. 235–241, 2004.
Link: http://www.sciencedirect.com/science/article/pii/S1387380604003550
Abstract
Proton transfer reaction mass spectrometry (PTR-MS) enables monitoring of trace gases in air with high sensitivity without major gases interfering. In this paper, we present the potential use of a proton transfer reaction mass spectrometer for two medical applications; the monitoring of drugs and bacterial infection. The first study illustrates a feasibility trial to monitor the intravenous anaesthetic agent 2,6-di-isopropyl phenol (propofol), and two of its metabolites, on the breath of patients in real-time during surgery. Propofol is a commonly used intravenous anaesthetic. However, there is no method of instantaneously monitoring the plasma concentration of the agent during surgery, and therefore determining whether or not the plasma level is of such a value to ensure that the patient is correctly anaesthetized. That propofol and its metabolites were monitored in real-time using the PTR-MS suggests possibilities for routine intravenous anaesthesia monitoring analogous to that for volatile anaesthetic agents. In addition to the above work we also investigated proton transfer to another anaesthetic, sevoflurane. Comparisons between PTR-MS and selected ion flow tube (SIFT) investigations are presented. The second study presented in this paper investigated the volatile organic compounds emitted by microbial cell cultures. The objective was to show that different microbial cultures could be readily distinguished from the resulting mass spectra recorded using the PTR-MS. The initial results are encouraging, which taken together with the real-time analysis and high sensitivity of the PTR-MS, means that proton transfer reaction mass spectrometry has the potential to characterise bacterial infection rapidly.
[Ezra2004] Ezra, D., J. Jasper, T. Rogers, B. Knighton, E. Grimsrud, and G. Strobel, "Proton transfer reaction-mass spectrometry as a technique to measure volatile emissions of Muscodor albus", Plant Science, vol. 166, no. 6: Elsevier, pp. 1471–1477, 2004.
Link: http://www.sciencedirect.com/science/article/pii/S0168945204000536
Abstract
Muscodor albus is an endophytic fungus that produces volatile organic compounds (VOCs) that both inhibit and kill other microorganisms. This fungus is now being used to treat human wastes and disinfest soils of plant disease causing organisms. The development of a method to accurately determine the quantity and quality of volatiles being emitted by this organism is critical for optimizing its application as an antimicrobial agent. Proton transfer reaction-mass spectrometry (PTR-MS) was used to monitor the concentration of VOCs emitted by M. albus. This on-line technique is fast, accurate and provides data at the detection limits of ppb. Production of VOCs is temperature dependent with decreased gas production occurring at higher temperatures. The technique was also applied to soils containing M. albus along with the plant pathogen Pythium ultimum and it was possible to successfully monitor VOC production in situ.

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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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