[Guazzotti2003] "Characterization of carbonaceous aerosols outflow from India and Arabia: Biomass/biofuel burning and fossil fuel combustion",
Journal of geophysical research
, vol. 108, no. D15: American Geophysical Union, pp. 4485, 2003.
A major objective of the Indian Ocean Experiment (INDOEX) involves the characterization of the extent and chemical composition of pollution outflow from the Indian Subcontinent during the winter monsoon. During this season, low-level flow from the continent transports pollutants over the Indian Ocean toward the Intertropical Convergence Zone (ITCZ). Traditional standardized aerosol particle chemical analysis, together with real-time single particle and fast-response gas-phase measurements provided characterization of the sampled aerosol chemical properties. The gas- and particle-phase chemical compositions of encountered air parcels changed according to their geographic origin, which was traced by back trajectory analysis. The temporal evolutions of acetonitrile, a long-lived specific tracer for biomass/biofuel burning, number concentration of submicrometer carbon-containing particles with potassium (indicative of combustion sources), and mass concentration of submicrometer non-sea-salt (nss) potassium are compared. High correlation coefficients (0.84 < r2 < 0.92) are determined for these comparisons indicating that most likely the majority of the species evolve from the same, related, or proximate sources. Aerosol and trace gas measurements provide evidence that emissions from fossil fuel and biomass/biofuel burning are subject to long-range transport, thereby contributing to anthropogenic pollution even in areas downwind of South Asia. Specifically, high concentrations of submicrometer nss potassium, carbon-containing particles with potassium, and acetonitrile are observed in air masses advected from the Indian subcontinent, indicating a strong impact of biomass/biofuel burning in India during the sampling periods (74 (±9)% biomass/biofuel contribution to submicrometer carbonaceous aerosol). In contrast, lower values for these same species were measured in air masses from the Arabian Peninsula, where dominance of fossil fuel combustion is suggested by results from single-particle analysis and supported by results from gas-phase measurements (63 (±9))% fossil fuel contribution to submicrometer carbonaceous aerosol). Results presented here demonstrate the importance of simultaneous, detailed gas- and particle-phase measurements of related species when evaluating possible source contributions to aerosols in different regions of the world.
[Roberts2003] "Comparison of nosespace, headspace, and sensory intensity ratings for the evaluation of flavor absorption by fat.",
J Agric Food Chem
, vol. 51, no. 12: NestlÃ© Research Center, P.O. Box 44, Vers-Chez-les-Blanc, 1000 Lausanne 26, Switzerland. email@example.com, pp. 3636–3642, Jun, 2003.
The goal of this study was to better understand the correspondence between sensory perception and in-nose compound concentration. Five aroma compounds at three different concentrations increasing by factors of 4 were added to four matrixes (water, skim milk, 2.7% fat milk, and 3.8% fat milk). These were evaluated by nosespace analysis with detection by proton transfer reaction mass spectrometry (PTR-MS), using five panelists. These same panelists evaluated the perceived intensity of each compound in the matrixes at the three concentrations. PTR-MS quantification found that the percent released from an aqueous solution swallowed immediately was between 0.1 and 0.6%, depending on the compound. The nosespace and sensory results showed the expected effect of fat on release, where lipophilic compounds showed reductions in release as fat content increases. The effect is less than that observed in headspace studies. A general correlation between nosespace concentration and sensory intensity ratings was found. However, examples of perceptual masking were found where higher fat milks showed reductions in aroma compound intensity ratings, even if the nosespace concentrations were the same.
[Christian2003] "Comprehensive laboratory measurements of biomass-burning emissions: 1. Emissions from Indonesian, African, and other fuels",
J. Geophys. Res
, vol. 108, no. 4719, pp. 1–4719, 2003.
Trace gas and particle emissions were measured from 47 laboratory fires burning 16 regionally to globally significant fuel types. Instrumentation included the following: open-path Fourier transform infrared spectroscopy; proton transfer reaction mass spectrometry; filter sampling with subsequent analysis of particles with diameter <2.5 μm for organic and elemental carbon and other elements; and canister sampling with subsequent analysis by gas chromatography (GC)/flame ionization detector, GC/electron capture detector, and GC/mass spectrometry. The emissions of 26 compounds are reported by fuel type. The results include the first detailed measurements of the emissions from Indonesian fuels. Carbon dioxide, CO, CH4, NH3, HCN, methanol, and acetic acid were the seven most abundant emissions (in order) from burning Indonesian peat. Acetol (hydroxyacetone) was a major, previously unobserved emission from burning rice straw (21–34 g/kg). The emission factors for our simulated African fires are consistent with field data for African fires for compounds measured in both the laboratory and the field. However, the higher concentrations and more extensive instrumentation in this work allowed quantification of at least 10 species not previously quantified for African field fires (in order of abundance): acetaldehyde, phenol, acetol, glycolaldehyde, methylvinylether, furan, acetone, acetonitrile, propenenitrile, and propanenitrile. Most of these new compounds are oxygenated organic compounds, which further reinforces the importance of these reactive compounds as initial emissions from global biomass burning. A few high-combustion-efficiency fires emitted very high levels of elemental (black) carbon, suggesting that biomass burning may produce more elemental carbon than previously estimated.
[Biasioli2003] "Coupling proton transfer reaction-mass spectrometry with linear discriminant analysis: a case study.",
J Agric Food Chem
, vol. 51, no. 25: Istituto Agrario di S. Michele a/A, S. Michele, Via E. Mach 2, 38010, Italy. firstname.lastname@example.org, pp. 7227–7233, Dec, 2003.
Proton transfer reaction-mass spectrometry (PTR-MS) measurements on single intact strawberry fruits were combined with an appropriate data analysis based on compression of spectrometric data followed by class modeling. In a first experiment 8 of 9 different strawberry varieties measured on the third to fourth day after harvest could be successfully distinguished by linear discriminant analysis (LDA) on PTR-MS spectra compressed by discriminant partial least squares (dPLS). In a second experiment two varieties were investigated as to whether different growing conditions (open field, tunnel), location, and/or harvesting time can affect the proposed classification method. Internal cross-validation gives 27 successes of 28 tests for the 9 varieties experiment and 100% for the 2 clones experiment (30 samples). For one clone, present in both experiments, the models developed for one experiment were successfully tested with the homogeneous independent data of the other with success rates of 100% (3 of 3) and 93% (14 of 15), respectively. This is an indication that the proposed combination of PTR-MS with discriminant analysis and class modeling provides a new and valuable tool for product classification in agroindustrial applications.
[Karl2003] "Dynamic measurements of partition coefficients using proton-transfer-reaction mass spectrometry (PTR–MS)",
International Journal of Mass Spectrometry
, vol. 223: Elsevier, pp. 383–395, 2003.
Liquid–gas partition coefficients (HLC) of volatile organic compounds (VOCs) in water–air systems are determined using a novel dynamic approach by coupling a stripping cell directly to a proton-transfer-reaction mass spectrometer (PTR–MS). Two complementary set-ups are evaluated, one suited for determining HLCs of highly volatile compounds (<10 M/atm), the second adapted for medium to low volatile compounds (∼10–1000 M/atm). We validated the method using 2-butanone, investigated the temperature dependence of various HLCs and applied the stripping technique to a series of VOCs. Compared to alternative state-of-the-art techniques the present approach has the advantage of being simple, fast and less prone to artefacts. Furthermore, it allows to quantify volatile compounds in the headspace without calibration or addition of standards.
[Lirk2003] "Elective haemodialysis increases exhaled isoprene.",
Nephrol Dial Transplant
, vol. 18, no. 5: Department of Anesthesiology and Critical Care Medicine, Leopold Franzens University of Innsbruck, Anichstrasse 35, A-6020 Innsbruck, Austria., pp. 937–941, May, 2003.
Uraemic odour is a characteristic feature of patients with end-stage renal disease (ESRD). However, few investigations have been carried out into the composition of exhaled air in ESRD patients undergoing haemodialysis (HD). Increases of exhaled isoprene levels by a factor of up to 2.7 following HD have been reported.We attempted to confirm these findings in 50 patients undergoing HD using haemophan (n=23) or polysulphone (n=27) dialysis membranes. Parallel evaluation of ambient air, calorie intake, medication and haemodynamic variables was performed. Samples were analysed using proton transfer reaction-mass spectrometry (PTR-MS).Significant changes in breath isoprene concentration were observed when comparing patients before [39.14+/-14.96 parts per billion (ppbv)] and after (63.54+/-27.59 ppbv) dialysis (P<0.001). The quotient of values before and after dialysis was 1.84 (SD 1.41). No significant differences in isoprene kinetics were found between the use of haemophan and polysulphone membranes. No significant correlations were observed between isoprene quotients and variations in blood pressure during HD, calorie intake, ingestion of lipid-lowering drugs or serum lipid levels.Isoprene concentration was higher in the exhaled air of patients after HD as compared with values before HD. Large interindividual variability existed in isoprene kinetics. Oxidative stress appears to be an unlikely cause for this rise. An alternative hypothesis is an influence of respiratory variables on isoprene exhalation based upon Henry's law constant. We therefore propose to perform online monitoring of isoprene exhalation by PTR-MS during the HD session to investigate the possible influence of respiratory variables.
[DeGouw2003] "Emission sources and ocean uptake of acetonitrile (CH3CN) in the atmosphere",
Journal of geophysical research
, vol. 108, no. D11: American Geophysical Union, pp. 4329, 2003.
Airborne measurements of acetonitrile (CH3CN) were made off the U.S. west coast, over California, and during two transfer flights over the U.S. in April and May of 2002. Acetonitrile was strongly enhanced in the plumes from two forest fires, confirming the usefulness of the measurement as an indicator for biomass burning emissions. The emission ratios relative to CO of acetonitrile in the two plumes were slightly higher than previously reported values for fires burning in other fuel types. No significant acetonitrile release was observed in the Los Angeles basin or from other point sources (ships and a power plant). Acetonitrile concentrations were significantly reduced in the marine boundary layer indicating the presence of an ocean uptake sink. Increased loss of acetonitrile was observed close to the coast, suggesting that acetonitrile was efficiently lost by dissolving in the upwelling ocean water, or by biological processes in the surface water.
[Biasioli2003a] "Fingerprinting mass spectrometry by PTR-MS: heat treatment vs. pressure treatment of red orange juice - a case study",
International journal of mass spectrometry
, vol. 223: Elsevier, pp. 343–353, 2003.
Proton transfer reaction mass spectrometry (PTR-MS) is more and more applied to rather different fields of research and applications showing interesting performances where high sensitivity and fast monitoring of volatile organic compounds (VOCs) are required. Based on this technique and aiming at the realisation of an automatic system for routine applications in food science and technology, we tested here a novel approach for fingerprinting mass spectrometric detection and analysis of complex mixtures of VOCs. In particular, we describe and discuss corresponding head space (HS) sampling methods and possible data analysis techniques. As a first test case we studied here the properties of four red orange juices processed by different stabilisation methods starting from the same industrial batch: untreated juice, thermal pasteurised (flash and standard) juice and high pressure stabilised juice. We demonstrate the possibility of a fast automatic discrimination/classification of the samples with the further advantage, compared to the use of electronic noses, of useful information on the mass of the discriminating compounds. Moreover, first comparisons with discriminative analysis by a sensory panel shows evidence that there is a correlation between the ability of the PTR-MS to distinguish different juice samples and that of a panel of trained judges with the obvious advantages of an instrumental approach.
[Boscaini2003] "Gas chromatography-olfactometry (GC-O) and proton transfer reaction-mass spectrometry (PTR-MS) analysis of the flavor profile of grana padano, parmigiano reggiano, and grana trentino cheeses.",
J Agric Food Chem
, vol. 51, no. 7: Institut fuer Ionenphysik, Universitaet Innsbruck, Technikerstrasse 25, A-6020 Innsbruck, Austria., pp. 1782–1790, Mar, 2003.
Gas chromatography-olfactometry (GC-O) and proton transfer reaction-mass spectrometry (PTR-MS) techniques were used to deduce the profile of odor-active and volatile compounds of three grana cheeses: Grana Padano (GP), Parmigiano Reggiano (PR), and Grana Trentino (GT). Samples for GC-O analysis were prepared by dynamic headspace extraction, while a direct analysis of the headspace formed over cheese was performed by PTR-MS. The major contributors to the odor profile were ethyl butanoate, 2-heptanone, and ethyl hexanoate, with fruity notes. A high concentration of mass 45, tentatively identified as acetaldehyde, was found by PTR-MS analysis. Low odor threshold compounds, e.g., methional and 1-octen-3-one, which contributed to the odor profile but were not detected by FID, were detected by PTR-MS. Principal component analysis on both GC-O and PTR-MS data separated the three cheese samples well and showed specific compounds related to each sample.
[Salisbury2003] "Ground-based PTR-MS measurements of reactive organic compounds during the MINOS campaign in Crete, July–August 2001",
Atmospheric Chemistry and Physics
, vol. 3, no. 4: Copernicus GmbH, pp. 925–940, 2003.
This study presents measurements of acetonitrile, benzene, toluene, methanol and acetone made using the proton-transfer-reaction mass spectrometry (PTR-MS) technique at the Finokalia ground station in Crete during the Mediterranean INtensive Oxidant Study (MINOS) in July-August 2001. Three periods during the campaign with broadly consistent back trajectories are examined in detail. In the first, air was advected from Eastern Europe without significant biomass burning influence (mean acetonitrile mixing ratio 154 pmol/mol). In the second period, the sampled air masses originated in Western Europe, and were advected approximately east-south-east, before turning south-west over the Black Sea and north-western Turkey. The third well-defined period included air masses advected from Eastern Europe passing east and south of/over the Sea of Azov, and showed significant influence by biomass burning (mean acetonitrile mixing ratio 436 pmol/mol), confirmed by satellite pictures. The mean toluene:benzene ratios observed in the three campaign periods described were 0.35, 0.37 and 0.22, respectively; the use of this quantity to determine air mass age is discussed. Methanol and acetone were generally well-correlated both with each other and with carbon monoxide throughout the campaign. Comparison of the acetone and methanol measurements with the MATCH-MPIC model showed that the model underestimated both species by a factor of 4, on average. The correlations between acetone, methanol and CO implied that the relatively high levels of methanol observed during MINOS were largely due to direct biogenic emissions, and also that biogenic sources of acetone were highly significant during MINOS ( 35%). This in turn suggests that the model deficit in both species may be due, at least in part, to missing biogenic emissions.
[Hansson2003] "The influence of gel strength on aroma release from pectin gels in a model mouth and in vivo, monitored with proton-transfer-reaction mass spectrometry.",
J Agric Food Chem
, vol. 51, no. 16: The Swedish Institute for Food and Biotechnology (SIK), P.O. Box 5401, S-402 29 Goeteborg, Sweden. email@example.com, pp. 4732–4740, Jul, 2003.
The course of events from taking a food into the mouth to the perception of the food's flavor involves many steps, from dilution with saliva, mastication, and transportation of the compounds to the olfactory epithelium to transformation into signals that go to the brain. In addition, there are also the effects of the food's structure and properties. In this study, a proton-transfer-reaction mass spectrometer (PTR-MS) was used to investigate how four pectin-containing systems with different structures and strengths affected the release of aroma compounds in a model mouth and in the nose of an assessor. Both the model mouth and the in-nose measurements showed that the strength and structure of pectin-containing systems are important with regard to the quantity of aroma compounds that are released. Mastication and saliva were also shown to have a large influence on how much of the aroma compound is released from the mouth to the nose.
[Mayr2003a] "In-vivo analysis of banana aroma by Proton Transfer Reaction-Mass Spectrometry.",
Flavour Research at the Dawn of the Twenty-first Century-Proceedings of the 10th Weurman Flavour Research Symposium, Beaune, France, 25-28 June, 2002.
: Editions Tec & Doc, pp. 256–259, 2003.
We report on in-vivo breath-by-breath analysis of volatiles released in the mouth during eating of ripe and unripe banana using Proton Transfer Reaction-Mass Spectrometry (PTR-MS). The time-intensity profiles of isopentyl and isobutyl acetate, two key odour compounds of ripe, and (E)2-hexenal and hexanal, typical for unripe banana, are discussed. The questions we address is: how do retronasal aroma (nosespace, NS) and orthonasal aroma (headspace, HS) differ? Two main differences were noticed. First, the NS concentrations of some compounds are increased, compared to the HS, while others are decreased. Second, aroma in the mouth is dynamic, evolving with time. The in-mouth situation has characteristics of its own that may lead to an aromatic experience specific to the eating situation.
[Pollien2003b] "Liquid–air partitioning of volatile compounds in coffee: dynamic measurements using proton-transfer-reaction mass spectrometry",
International Journal of Mass Spectrometry
, vol. 228, no. 1: Elsevier, pp. 69–80, 2003.
Recently we introduced a dynamic approach to determine Henry’s law constants (HLCs) of volatile organic compounds (VOCs) in water, and applied it to a series organic compounds dissolved in pure water. Here, we first discuss a further development of the original approach such that it can be applied to complex liquid food systems (coffee). Second, we examine the impact of non-volatile constituents on the HLC. More specifically, we evaluate the impact of non-volatile coffee constituents on the HLC of 2-methylpropanal, 3- and 2-methylbutanal, dimethylsulfide, dimethyldisulfide and ethyl-2-methylbutyrate. Finally, we demonstrate that the concentration on the VOC in solution does not affect the HLC, over the investigated concentration range of 10−4 to 10 ppm.
[Tani2003] "Measurement of monoterpenes and related compounds by proton transfer reaction-mass spectrometry (PTR-MS)",
International Journal of Mass Spectrometry
, vol. 223: Elsevier, pp. 561–578, 2003.
The reactions of monoterpenes and related C10 compounds with H3O+ in a proton transfer reaction-mass spectrometer (PTR-MS) were studied, with a view to better understanding the signal produced by this instrument when detecting these compounds. The monoterpenes α- and β-pinene, 3-carene and limonene produced fragment ions of masses 67, 81 and 95 as well as a protonated molecular ion of mass 137, while p-cymene (C10H14) produced ions of masses 41, 91, 93 and 119 in addition to mass 135. The fragmentation patterns were observed to vary as E/N was varied. Camphor (C10H16O) did not fragment within the E/N range 80–120 Td. The proton transfer reaction rate coefficients for these monoterpene species with H3O+ were found to be 2.2×10−9 to 2.5×10−9 cm3 s−1. For camphor the rate coefficient was 4.4×10−9 cm3 s−1. Water vapour pressure in the inlet air affected the fragmentation pattern for p-cymene, limonene and 3-carene. The uncertainties associated with the PTR-MS measurement of these compounds are discussed.
[Alexander2003] "Membrane introduction proton-transfer reaction mass spectrometry",
International Journal of Mass Spectrometry
, vol. 223: Elsevier, pp. 763–770, 2003.
The combination of membrane introduction mass spectrometry (MIMS) and proton-transfer reaction mass spectrometry (PTR-MS) is explored. The PTR-MS is used to measure properties of a well-characterized membrane material, poly-dimethylsiloxane (PDMS). It is found that the ability of the PTR-MS to measure absolute concentrations in real-time makes it an ideal tool for the characterization of membrane properties and the interaction of the membrane with multiple organic species. Values for the diffusion coefficients of several molecules are measured and found to be in agreement with literature values. Time modulation of the analyte across the membrane is explored as a method of resolving isobaric interferences for different chemical species. This is demonstrated for acetone and propanal. Finally, the benefit of combining MIMS with PTR-MS is demonstrated by the direct analysis of organic species in the headspace of a hot water solution where the high humidity would not allow analysis using the PTR-MS alone.
[Gros2003] "Origin of anthropogenic hydrocarbons and halocarbons measured in the summertime European outflow (on Crete in 2001)",
Atmospheric Chemistry and Physics
, vol. 3, no. 4: Copernicus GmbH, pp. 1223–1235, 2003.
[Prazeller2003] "Proton transfer reaction ion trap mass spectrometer",
Rapid communications in mass spectrometry
, vol. 17, no. 14: Wiley Online Library, pp. 1593–1599, 2003.
Proton transfer reaction mass spectrometry is a relatively new field that has attracted a great deal of interest in the last few years. This technique uses H3O+ as a chemical ionization (CI) reagent to measure volatile organic compounds (VOCs) in the parts per billion by volume (ppbv) to parts per trillion by volume (pptv) range. Mass spectra acquired with a proton transfer reaction mass spectrometer (PTR-MS) are simple because proton transfer chemical ionization is ‘soft’ and results in little or no fragmentation. Unfortunately, peak identification can still be difficult due to isobaric interferences. A possible solution to this problem is to couple the PTR drift tube to an ion trap mass spectrometer (ITMS). The use of an ITMS is appealing because of its ability to perform MS/MS and possibly distinguish between isomers and other isobars. Additionally, the ITMS duty cycle is much higher than that of a linear quadrupole so faster data acquisition rates are possible that will allow for detection of multiple compounds. Here we present the first results from a proton transfer reaction ion trap mass spectrometer (PTR-ITMS). The aim of this study was to investigate ion injection and storage efficiency of a simple prototype instrument in order to estimate possible detection limits of a second-generation instrument. Using this prototype a detection limit of 100 ppbv was demonstrated. Modifications are suggested that will enable further reduction in detection limits to the low-ppbv to high-pptv range. Furthermore, the applicability of MS/MS in differentiating between isobaric species was determined. MS/MS spectra of the isobaric compounds methyl vinyl ketone (MVK) and methacrolein (MACR) are presented and show fragments of different mass making differentiation possible, even when a mixture of both species is present in the same sample. However, MS/MS spectra of acetone and propanal produce fragments with the same molecular masses but with different intensity ratios. This allows quantitative distinction only if one species is predominant. Fragmentation mechanisms are proposed to explain the results.
[Pollien2003] "Proton transfer reaction mass spectrometry, a tool for on-line monitoring of acrylamide formation in the headspace of maillard reaction systems and processed food.",
, vol. 75, no. 20: Nestle Research Center, Vers-chez-les-Blanc, 1000 Lausanne 26, Switzerland., pp. 5488–5494, Oct, 2003.
The formation of acrylamide was measured in real time during thermal treatment (120-170 degrees C) of potato as well as in Maillard model systems composed of asparagine and reducing sugars, such as fructose and glucose. This was achieved by on-line monitoring of acrylamide released into the headspace of the samples using proton transfer reaction mass spectrometry (PTR-MS). Unambiguous identification of acrylamide by PTR-MS was accomplished by gas chromatography coupled simultaneously to electron-impact MS and PTR-MS. The PTR-MS ion signal at m/z 72 was shown to be exclusively due to protonated acrylamide obtained without fragmentation. In model Maillard systems, the formation of acrylamide from asparagine was favored with increasing temperature and preferably in the presence of fructose. Maximum signal intensities in the headspace were obtained after approximately 2 min at 170 degrees C, whereas 6-7 min was required at 150 degrees C. Similarly, the level of acrylamide released into the headspace during thermal treatment of potato was positively correlated to temperature.
[Kreuzwieser2003] "Quantification of carbon sources for isoprene emission in poplar leaves",
AGU Fall Meeting Abstracts
, vol. 1, pp. 0119, 2003.
Isoprene is the most abundant volatile organic compound emitted by plants and in particular by trees. Current interest in understanding its biosynthesis in chloroplasts is forced by the important role isoprene plays in atmospheric chemistry. Leaf isoprene formation is closely linked to photosynthesis by a dynamic use of recently fixed photosynthetic precursors in the chloroplast. Under steady state conditions in [13C]CO2 atmosphere approximately 75 % of isoprene became labeled within minutes. The source of unlabeled C is suggested to be of extra-chloroplastidic and/or from starch degradation. In order to test whether these alternative carbon sources - leaf internal C-pools and xylem-transported carbohydrates, contribute to leaf isoprene formation in poplar (Populus tremula x P. alba) on-line proton-transfer-reaction-mass spectrometry (PTR-MS) was used to follow 13C-labeling kinetics.
[Mayr2003] "Rapid detection of meat spoilage by measuring volatile organic compounds by using proton transfer reaction mass spectrometry",
Applied and environmental microbiology
, vol. 69, no. 8: Am Soc Microbiol, pp. 4697–4705, 2003.
The evolution of the microbial spoilage population for air- and vacuum-packaged meat (beef and pork) stored at 4°C was investigated over 11 days. We monitored the viable counts (mesophilic total aerobic bacteria, Pseudomonas spp., Enterobacteriaceae, lactic acid bacteria, and Enterococcus spp.) by the microbiological standard technique and by measuring the emission of volatile organic compounds (VOCs) with the recently developed proton transfer reaction mass spectrometry system. Storage time, packaging type, and meat type had statistically significant (P < 0.05) effects on the development of the bacterial numbers. The concentrations of many of the measured VOCs, e.g., sulfur compounds, largely increased over the storage time. We also observed a large difference in the emissions between vacuum- and air-packaged meat. We found statistically significant strong correlations (up to 99%) between some of the VOCs and the bacterial contamination. The concentrations of these VOCs increased linearly with the bacterial numbers. This study is a first step toward replacing the time-consuming plate counting by fast headspace air measurements, where the bacterial spoilage can be determined within minutes instead of days.
[Kennedy2003] "Reactions of H< sub> 3 O< sup>+ with a number of bromine containing fully and partially halogenated hydrocarbons",
International Journal of Mass Spectrometry
, vol. 223: Elsevier, pp. 627–637, 2003.
The thermal bimolecular rate coefficients and product ion branching ratios for the reactions of H3O+ with the bromine containing molecules CH3Br, CH2Br2, CH2FBr, CHF2Br, CHFBr2, CH2BrCl, CHBrCl2, CHBr2Cl, CH3CH2Br, CH2BrCH2Cl, CH2BrCH2Br, CF3CF2Br and CF2BrCF2Br at 300 K are reported. H3O+ reacts with an experimental rate coefficient (kexp) close to the collisional value (kc≈10−9 cm3 molecule−1 s−1) with CHFBr2, CHBrCl2, CHBr2Cl, CH2BrCH2Cl, and CH2BrCH2Br, at a decreased efficiency with CH3CH2Br (kexp/kc≈0.3). The other neutral reactant molecules, CH3Br, CH2FBr, CHF2Br, CF3CF2Br, and CF2BrCF2Br react through a three-body associative process. There is no observable reaction with CH2Br2 and CH2BrCl. Mechanistic arguments are given that go some way to explaining the observed range in both reactivity and reaction pathways.
[Harrison2003] "Real-time breath monitoring of propofol and its volatile metabolites during surgery using a novel mass spectrometric technique: a feasibility study.",
Br J Anaesth
, vol. 91, no. 6: Featherstone Department of Anaesthesia and Intensive Care, Queen Elizabeth Hospital, University Hospital Birmingham NHS Trust, Birmingham B15 2TH, UK., pp. 797–799, Dec, 2003.
At present, there is no rapid method for determining the plasma concentration of i.v. anaesthetics. A solution might be the measurement of the anaesthetic concentration in expired breath and its relation to the plasma concentration. We used chemical ionization methods to determine whether an i.v. anaesthetic can be detected in the low concentrations (parts per billion by volume) in the expired breath of an anaesthetized patient.Chemical ionization mass spectrometry can measure trace gases in air with high sensitivity without interference from major gases. We carried out a feasibility trial with a proton transfer reaction mass spectrometer (PTR-MS) to monitor the i.v. anaesthetic agent propofol and two of its metabolites in exhaled gas from an anaesthetic circuit. Exhaled gas was sampled via a 4 m long, unheated tube connected to the PTR-MS.Propofol and its metabolites were monitored in real time in the expired breath of patients undergoing surgery.Routine measurement of i.v. agents, analogous to that for volatile anaesthetic agents, may be possible.
[Karl2003c] "Seasonal variation of biogenic VOC emissions above a mixed hardwood forest in northern Michigan",
Geophysical Research Letters
, vol. 30, no. 23: Wiley Online Library, 2003.
Fluxes of biogenic volatile organic compounds (VOCs) were measured at a hardwood forest in northern Michigan (UMBS, Prophet research site) over the course of the growing and senescing season. Methanol, acetaldehyde, acetone and isoprene were found to be the most abundant biogenic VOCs with maximum fluxes (mixing ratios in ppbv) of 2.0 mg m−2 h−1 (21.0), 1.0 mg m−2 h−1 (2.7), 1.6 mg m−2 h−1 (5.6) and 7.6 mg m−2 h−1 (6), respectively. The emission patterns show distinct seasonal changes and indicate a spring peak for methanol due to rapid leaf expansion and a fall peak for acetone and acetaldehyde most likely attributed to senescing and decaying biomass; isoprene emissions peaked as expected in the summer. We estimate potential source strengths of 8.9 Tg (C) y−1 methanol, 2.7 Tg (C) y−1 acetaldehyde and 7.0 Tg (C) y−1 acetone for deciduous temperate forests, which is a substantial contribution to the global atmospheric VOC budget.
[Gouw2003] "Sensitivity and specificity of atmospheric trace gas detection by proton-transfer-reaction mass spectrometry",
International Journal of Mass Spectrometry
, vol. 223: Elsevier, pp. 365–382, 2003.
[Summer2003] "Sevoflurane in exhaled air of operating room personnel",
Anesthesia & Analgesia
, vol. 97, no. 4: IARS, pp. 1070–1073, 2003.
Evidence on potential health hazards arising from exposure to volatile anesthetics remains controversial. Exposure may, in principle, be supervised by monitoring of ambient air or, alternatively, in vivo. We used the Proton Transfer Reaction-Mass Spectrometry to screen the breath of 40 operating room staff members before operating room duty, 0, 1, 2, and 3 h after duty, and before commencing duty on the consecutive day, and control persons. Staff members exhibited significantly increased sevoflurane levels in exhaled air after duty, with a mean of 0.80 parts per billion as compared with baseline values of 0.26 parts per billion (P < 0.05). Analysis of variance with adjustment for within correlation (repeated measurements) showed a statistically significant time-effect (P < 0.001). We conclude that (a) Proton Transfer Reaction-Mass Spectrometry biomonitoring of exhaled sevoflurane can serve as a simple and rapid method to determine volatile anesthetic excretion after occupational exposure, and (b) significant concentrations of sevoflurane may be continuously present in persons exposed to sevoflurane on a daily basis.