Scientific Articles - PTR-MS Bibliography

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2011
[Saha2011] "Effects of airflow on odorants' emissions in a model pig house - A laboratory study using Proton-Transfer-Reaction Mass Spectrometry (PTR-MS).", Sci Total Environ, vol. 410-411: Department of Engineering, Aarhus University, Blichers AllÃ© 20, 8830 Tjele, Denmark. cksahabau@yahoo.com, pp. 161–171, Dec, 2011.
Abstract
Identification of different factors that affect emissions of gasses, including volatile organic compounds (VOCs) is necessary to develop emission abatement technology. The objectives of this research were to quantify and study temporal variation of gas emissions from a model pig house under varying ventilation rates. The used model was a 1:12.5 scale of a section of a commercial finishing pig house. The VOC concentrations at inlet, outlet, and slurry pit of the model space were measured using Proton-Transfer-Reaction Mass Spectrometry (PTR-MS). PTR-MS can measure the temporal variations of odor compounds' emission from the slurry pit in real time. The emissions of H(2)S and 14 VOCs were lower compared to real pig buildings except for ammonia, which indicated possible other sources of those compounds than the slurry in the slurry pit. The ventilation rate affected significantly on ammonia and trimethylamine emission (p<0.05). The hydrogen sulfide (H(2)S) emission was independent of the ventilation rate. VFAs' emission dependency on ventilation rate increased with the increase of carbon chain. Phenols, indoles and ketones showed the positive correlation with ventilation rate to some extent. Generally, compounds with high solubility (low Henry's constant) showed stronger correlation with ventilation rates than the compounds with high Henry's constant.
[1490] "Effects of Mentholation on Cigarette Smoke Emissions", Conference of the Society for Research on Nicotine and Tobacco (SRNT), Toronto, Canada, Conference of the Society for Research on Nicotine and Tobacco (SRNT), Feb., 2011.
[Singh2011] "An endophytic Phomopsis sp. possessing bioactivity and fuel potential with its volatile organic compounds", Microbial ecology, vol. 61, no. 4: Springer, pp. 729–739, 2011.
Abstract
An unusual Phomopsis sp. was isolated as endophyte of Odontoglossum sp. (Orchidaceae), associated with a cloud forest in Northern Ecuador. This fungus produces a unique mixture of volatile organic compounds (VOCs) including sabinene (a monoterpene with a peppery odor) only previously known from higher plants. In addition, some of the other more abundant VOCs recorded by GC/MS in this organism were 1-butanol, 3-methyl; benzeneethanol; 1-propanol, 2-methyl and 2-propanone. The gases of Phomopsis sp. possess antifungal properties and an artificial mixture of the VOCs mimicked the antibiotic effects of this organism with the greatest bioactivity against a wide range of plant pathogenic test fungi including: Pythium, Phytophthora, Sclerotinia, Rhizoctonia, Fusarium, Botrytis, Verticillium, and Colletotrichum. The IC50 values for the artificial gas mixture of Phomopsis sp. varied between 8 and 25.65 μl/mL. Proton transfer reaction-mass spectrometry monitored the concentration of VOCs emitted by Phomopsis sp. and yielded a total VOC concentration of ca. 18 ppmv in the head space at the seventh day of incubation at 23°C on PDA. As with many VOC-producing endophytes, this Phomopsis sp. did survive and grow in the presence of the inhibitory gases of Muscodor albus. A discussion is presented on the possible involvement of VOC production by the fungus and its role in the biology/ecology of the fungus/plant/environmental relationship.
[Fischer2011] "Evaporating Liquid Samples for Analysis with PTR-MS", 5th International PTR-MS Conference on Proton Transfer Reaction Mass Spectrometry and Its Applications, pp. 211–212, 2011.
Abstract
We present a method for measuring liquid samples with the PTR-MS by using a spray to convert the liquid into the gas phase. Advantages over headspace measurements concerning compounds with high Henry's law constants could be demonstrated.
[Cappellin2011] "Extending the dynamic range of proton transfer reaction time-of-flight mass spectrometers by a novel dead time correction.", Rapid Commun Mass Spectrom, vol. 25, no. 1: IASMA Research and Innovation Centre, Fondazione Edmund Mach, Food Quality and Nutrition Area, Via E. Mach 1, 38010 S. Michele a/A, Italy., pp. 179–183, Jan, 2011.
Abstract
Proton transfer reaction time-of-flight mass spectrometry (PTR-TOF-MS) allows for very fast simultaneous monitoring of volatile organic compounds (VOCs) in complex environments. In several applications, food science and food technology in particular, peaks with very different intensities are present in a single spectrum. For VOCs, the concentrations range from the sub-ppt all the way up to the ppm level. Thus, a large dynamic range is necessary. In particular, high intensity peaks are a problem because for them the linear dependency of the detector signal on VOC concentration is distorted. In this paper we present, test with real data, and discuss a novel method which extends the linearity of PTR-TOF-MS for high intensity peaks far beyond the limit allowed by the usual analytical correction methods such as the so-called Poisson correction. Usually, raw data can be used directly without corrections with an intensity of up to about 0.1 ions/pulse, and the Poisson correction allows the use of peaks with intensities of a few ions/pulse. Our method further extends the linear range by at least one order of magnitude. Although this work originated from the necessity to extend the dynamic range of PTR-TOF-MS instruments in agro-industrial applications, it is by no means limited to this area, and can be implemented wherever dead time corrections are an issue.
2010
[Kolarik2010] "The effect of a photocatalytic air purifier on indoor air quality quantified using different measuring methods", Building and Environment, vol. 45, no. 6, pp. 1434 - 1440, 2010.
Abstract
The effect on indoor air quality of an air purifier based on photocatalytic oxidation (PCO) was determined by different measuring techniques: sensory assessments of air quality made by human subjects, Proton-Transfer-Reaction Mass Spectrometry (PTR-MS) and chromatographic methods (Gas Chromatography/Mass Spectrometry and High-Pressure Liquid Chromatography with \{UV\} detection). The experiment was conducted in a simulated office, ventilated with 0.6 h−1, 2.5 h−1 and 6 h−1, in the presence of additional pollution sources (carpet, chipboard and linoleum). At the lowest air change rate, additional measurements were made with no pollution sources present in the office. All conditions were tested with the photocatalytic air purifier turned on and off. The results show that operation of the air purifier in the presence of pollutants emitted by building materials and furniture improves indoor air quality, as documented by sensory assessments made by human subjects. It also reduces concentrations of many chemical compounds present in the air as documented by the PTR-MS technique. For the lowest ventilation, results from measurements using the chromatographic methods have similar tendency, however many of the 50 compounds that were targeted for analysis were not detected at all, independent of whether the purifier was on or off. For the two conditions with higher ventilation the results were inconclusive.
[Feilberg2010b] "Effects of air Exchange, Temperature and slurry management on odorant Emissions from pig Production units and slurry tanks studied by Proton-Transfer-Reaction mass spectometry (PTR-MS)", World Congress of the International Commission of Agricultural and Biosystems Engineering (CIGR), 2010.
[Karl2010] "Efficient atmospheric cleansing of oxidized organic trace gases by vegetation", Science, vol. 330, no. 6005: American Association for the Advancement of Science, pp. 816–819, 2010.
Abstract
The biosphere is the major source and sink of nonmethane volatile organic compounds (VOCs) in the atmosphere. Gas-phase chemical reactions initiate the removal of these compounds from the atmosphere, which ultimately proceeds via deposition at the surface or direct oxidation to carbon monoxide or carbon dioxide. We performed ecosystem-scale flux measurements that show that the removal of oxygenated VOC via dry deposition is substantially larger than is currently assumed for deciduous ecosystems. Laboratory experiments indicate efficient enzymatic conversion and potential up-regulation of various stress-related genes, leading to enhanced uptake rates as a response to ozone and methyl vinyl ketone exposure or mechanical wounding. A revised scheme for the uptake of oxygenated VOCs, incorporated into a global chemistry-transport model, predicts appreciable regional changes in annual dry deposition fluxes.
[Kim2010] "Emissions and ambient distributions of Biogenic Volatile Organic Compounds (BVOC) in a ponderosa pine ecosystem: interpretation of PTR-MS mass spectra", Atmospheric Chemistry and Physics, vol. 10, no. 4: Copernicus GmbH, pp. 1759–1771, 2010.
Abstract
Two proton-transfer-reaction mass spectrometry systems were deployed at the Bio-hydro-atmosphere interactions of Energy, Aerosols, Carbon, H2O, Organics and Nitrogen-Southern Rocky Mountain 2008 field campaign (BEACHON-SRM08; July to September, 2008) at the Manitou Forest Observatory in a ponderosa pine woodland near Woodland Park, Colorado USA. The two PTR-MS systems simultaneously measured BVOC emissions and ambient distributions of their oxidation products. Here, we present mass spectral analysis in a wide range of masses (m/z 40+ to 210+) to assess our understanding of BVOC emissions and their photochemical processing inside of the forest canopy. The biogenic terpenoids, 2-methyl-3-butene-2-ol (MBO, 50.2%) and several monoterpenes (MT, 33.5%) were identified as the dominant BVOC emissions from a transmission corrected mass spectrum (PTR-MS), averaged over the daytime (11 a.m. to 3 p.m., local time) of three days. To assess contributions of oxidation products of local BVOC, we calculate an oxidation product spectrum with the OH- and ozone-initiated oxidation product distribution mass spectra of two major BVOC emissions at the ecosystem (MBO and β-pinene) that were observed from laboratory oxidation experiments. The majority ( 76%) of the total signal in the transmission corrected PTR-MS spectra could be explained by identified compounds. The remainder are attributed to oxidation products of BVOC emitted from nearby ecosystems and transported to the site, and oxidation products of unidentified BVOC emitted from the ponderosa pine ecosystem.
[Riess2010] "Experimental setup and analytical methods for the non-invasive determination of volatile organic compounds, formaldehyde and NOx in exhaled human breath.", Anal Chim Acta, vol. 669, no. 1-2: Hannover Medical School, Sports Physiology and Sports Medicine, Carl-Neuberg-Str. 1, 30625 Hannover, Germany., pp. 53–62, Jun, 2010.
Abstract
Different analytical devices were tested and evaluated for their suitability of breath gas analysis by examining the physiological parameters and chemical substances in the exhaled breath of ten healthy probands during light cycling in dependence of methanol-rich nutrition. The probands exercised under normal breathing conditions on a bicycle ergometer. Breath air was exhaled into a glass cylinder and collected under steady-state conditions. Non-invasively measured parameters were pulse rate, breath frequency, temperature, relative humidity, NO(x), total volatile organic compounds (TVOC(PAS)), carbon dioxide (CO(2)), formaldehyde, methanol, acetaldehyde, acetone, isoprene and volatile organic compounds (VOCs). Methanol rich food and beverages strongly influenced the concentration of methanol and other organic substances in human breath. On the other hand, nutrition and smoking had no clear effect on the physical conditions of the probands. The proton transfer reaction mass spectrometry (PTR-MS) method was found to be very suitable for the analysis of breath gas but the m/z 31, if assigned to formaldehyde, is sensitive to interferences. The time vs. concentration curves of nitric oxide showed sudden peaks up to 120ppb in most of the measurements. In one case a strong interference of the NO(x) signal was observed. The time resolved analysis of exhaled breath gas is of high capability and significance for different applications if reliable analytical techniques are used. Some compounds like nitric oxide (NO), methanol, different VOCs as well as sum parameters like TVOC(PAS) are especially suitable as markers. Formaldehyde, which is rapidly metabolized in the human body, could be measured reliably as a trace component by the acetylacetone (acac) method but not by PTR-MS.
[Jordan2010] "Extremely high mass resolution and sensitivity-comparison of two novel proton transfer reaction time-of-flight mass spectrometers (PTR-TOFMS)", Verhandlungen der Deutschen Physikalischen Gesellschaft, vol. -, no. Hanver 2010 issue, pp. -, 2010.
Abstract
Since many years PTR-MS is a well established technique in trace gas analysis with its major advantages of having very short response times of below 100ms and outstanding detection limits in the single digit pptv region. However, the quadrupole mass filter based instruments used so far cannot separate isobaric compounds due to lack of mass resolution. To overcome this problem Ionicon developed the so called PTR-TOF 8000 instrument, which couples the well established PTR ionization technique with a high resolution time-of-flight (TOF) mass analyzer. In contrast to a quadrupole based PTR-MS where only one nominal mass at a time can be monitored, the PTR-TOF acquires whole mass spectra in split-seconds at a resolution of up to 8.000 m/{delta}m (FWHM). As there might be applications where an enormous mass resolution is not necessarily needed, but the sensitivity has to be as high as possible, we now developed an instrument (called PTR-TOF 2000) that performs with an enhanced sensitivity at the expense of a somewhat lower mass resolution.
2009
[Sinha2009] "The effect of relative humidity on the detection of pyrrole by PTR-MS for OH reactivity measurements", International Journal of Mass Spectrometry, vol. 282, no. 3: Elsevier, pp. 108–111, 2009.
Abstract
The hydroxyl radical (OH) is the most important atmospheric oxidant. Recently Sinha et al. [V. Sinha, J. Williams, J.N. Crowley, J. Lelieveld, Atmos. Chem. Phys. 8 (2008) 2213] developed a new method to measure the total OH reactivity of ambient air (OH sink) employing a proton transfer reaction mass spectrometer (PTR-MS) as a detector. The new method uses pyrrole (C4H4NH) as a reagent and for an OH reactivity measurement this species must be measured under both dry (∼0% RH) and humid air (>30% RH). Here, we investigate the sensitivity dependence of the PTR-MS for pyrrole, as a function of relative humidity in the sampled air. Various normalizations with respect to the H3O+ ion and its different hydrated cluster ions H3O+(H2O)n=1,2,3 are compared. It is shown that both the primary ion signal (H3O+ ion m/z = 19) and the first water cluster ion H3O+(H2O) (m/z = 37) should be used for pyrrole quantification. However, in spite of using this normalization, the PTR-MS sensitivity for pyrrole changes by as much as 16% between dry (∼0% RH) and humid air (above 30% RH), with higher sensitivity when the sampled air is humid. Thus, for accurate quantification of pyrrole using a PTR-MS, calibration factors appropriate to dry and humid air should be employed. We recommend that humidity dependence of the PTR-MS be taken into account when reactivity measurements are performed using the pyrrole based comparative reactivity method (CRM).
[Leclercq2009] "Effects of cross-linking, capsule wall thickness, and compound hydrophobicity on aroma release from complex coacervate microcapsules.", J Agric Food Chem, vol. 57, no. 4: Department of Food Science and Nutrition, University of Minnesota, 1334 Eckles Avenue, St. Paul, Minnesota 55108, USA. lecle003@umn.edu, pp. 1426–1432, Feb, 2009.
Abstract
Microcapsules were produced by complex coacervation with a gelatin-gum acacia wall and medium-chain-triglyceride core. Dry capsules were partially rehydrated and then loaded with model aroma compounds covering a range of volatility, hydrophobicity, and molecular structure. An experimental design was prepared to evaluate the effects of cross-linking, wall/core ratio, and volatile load level on aroma release from capsules in a hot, aqueous environment. The real-time release on rehydration was measured by monitoring the headspace of a vessel containing the capsules to proton transfer reaction mass spectrometry (PTR-MS). Data collected showed no effects of cross-linking or wall/core ratio on volatile release in hot water for any of the volatiles studied. When comparing real-time release of the prepared coacervates to a spray-dried equivalent, there was no difference in the release from hot water but the release was slower when coacervates were added to ambient-temperature water. We found volatile release to be primarily determined by compound partition coefficients (oil/water and water/air) and temperature.
[Gasperi2009] "Effects of supercritical CO< sub> 2 and N< sub> 2 O pasteurisation on the quality of fresh apple juice", Food chemistry, vol. 115, no. 1: Elsevier, pp. 129–136, 2009.
Abstract
Supercritical pasteurisation is receiving increasing attention as an alternative technology for foodstuff pasteurisation, but often the possible effects on the perceptible quality are not sufficiently considered. To address this latter issue, besides standard microbial analysis, we here investigate the impact of CO2/N2O supercritical pasteurisation (100 bar, 36 °C and 10 min treatment time) on the quality traits of fresh apple juice, linked to consumer perception. Discriminative sensory analysis (triangle test) and basic chemical characterization (total solids, sugars, organic acids, polyphenols) could not clearly demonstrate any induced modification of the treated juice, while head space analysis of volatile compounds (both by GC–MS and PTR–MS) indicated a general depletion of the volatile compounds that must be considered in the development of a stabilization method based on supercritical gases.
[Karl2009] "Emissions of volatile organic compounds inferred from airborne flux measurements over a megacity", Atmospheric Chemistry and Physics, vol. 9, no. 1: Copernicus GmbH, pp. 271–285, 2009.
Abstract
Toluene and benzene are used for assessing the ability to measure disjunct eddy covariance (DEC) fluxes of Volatile Organic Compounds (VOC) using Proton Transfer Reaction Mass Spectrometry (PTR-MS) on aircraft. Statistically significant correlation between vertical wind speed and mixing ratios suggests that airborne VOC eddy covariance (EC) flux measurements using PTR-MS are feasible. City-median midday toluene and benzene fluxes are calculated to be on the order of 14.1±4.0 mg/m2/h and 4.7±2.3 mg/m2/h, respectively. For comparison the adjusted CAM2004 emission inventory estimates toluene fluxes of 10 mg/m2/h along the footprint of the flight-track. Wavelet analysis of instantaneous toluene and benzene measurements during city overpasses is tested as a tool to assess surface emission heterogeneity. High toluene to benzene flux ratios above an industrial district (e.g. 10–15 g/g) including the International airport (e.g. 3–5 g/g) and a mean flux (concentration) ratio of 3.2±0.5 g/g (3.9±0.3 g/g) across Mexico City indicate that evaporative fuel and industrial emissions play an important role for the prevalence of aromatic compounds. Based on a tracer model, which was constrained by BTEX (BTEX– Benzene/Toluene/Ethylbenzene/m, p, o-Xylenes) compound concentration ratios, the fuel marker methyl-tertiary-butyl-ether (MTBE) and the biomass burning marker acetonitrile (CH3CN), we show that a combination of industrial, evaporative fuel, and exhaust emissions account for >87% of all BTEX sources. Our observations suggest that biomass burning emissions play a minor role for the abundance of BTEX compounds in the MCMA (2–13%).
[OHara2009a] "Endogenous volatile organic compounds in breath and blood of healthy volunteers: examining breath analysis as a surrogate for blood measurements", Journal of Breath Research, vol. 3, no. 2, pp. 027005, 2009.
Abstract
To investigate the premise that levels of endogenous volatile organic compounds (VOC) in breath reflect those in blood, the concentration of acetone and isoprene were measured in radial arterial blood, peripheral venous blood and breath samples from ten healthy volunteers. Coefficients of repeatability as a percentage of mean are less than 30% in breath but greater than 70% in blood. The volunteer-mean ratios of arterial to venous blood concentration are 1.4 (0.9-2.1) for acetone and 0.55 (0.3-1.0) for isoprene. Concentration in breath showed a significant inter-subject correlation with concentration in arterial blood (CAB) for acetone but not for isoprene. Arterial blood/breath ratios are 580 (280-1060) for acetone and 0.47 (0.22-0.77) for isoprene. The sample-mean blood/breath ratio was used to calculate an estimate of CAB and the standard deviation of this estimate was lower than that of arterial blood measured directly. For most subjects, estimated CAB was within uncertainty limits of the actual CAB. Owing to the poor repeatability of VOC concentrations from consecutive blood samples, and the capacitive effects of the lung, this study suggests that breath VOC measurements may provide a more consistent measure than blood measurements for investigating underlying physiological function or pathology within individuals.
[Kameyama2009] "Equilibrator inlet-proton transfer reaction-mass spectrometry (EI-PTR-MS) for sensitive, high-resolution measurement of dimethyl sulfide dissolved in seawater.", Anal Chem, vol. 81, no. 21: National Institute for Environmental Studies, Tsukuba, 305-8506, Japan., pp. 9021–9026, Nov, 2009.
Abstract
We developed an equilibrator inlet-proton transfer reaction-mass spectrometry (EI-PTR-MS) method for fast detection of dimethyl sulfide (DMS) dissolved in seawater. Dissolved DMS extracted by bubbling pure nitrogen through the sample was continuously directed to the PTR-MS instrument. The equilibration of DMS between seawater and the carrier gas, and the response time of the system, were evaluated in the laboratory. DMS reached equilibrium with an overall response time of 1 min. The detection limit (50 pmol L(-1) at 5 s integration) was sufficient for detection of DMS concentrations in the open ocean. The EI-PTR-MS instrument was deployed during a research cruise in the western North Pacific Ocean. Comparison of the EI-PTR-MS results with results obtained by means of membrane tube equilibrator-gas chromatography/mass spectrometry agreed reasonably well on average (R(2) = 0.99). EI-PTR-MS captured temporal variations of dissolved DMS concentrations, including elevated peaks associated with patches of high biogenic activity. These results demonstrate that the EI-PTR-MS technique was effective for highly time-resolved measurements of DMS in the open ocean. Further measurements will improve our understanding of the biogeochemical mechanisms of the production, consumption, and distribution of DMS on the ocean surface and, hence, the air-sea flux of DMS, which is a climatically important species.
[Maleknia2009] "Eucalypt smoke and wildfires: Temperature dependent emissions of biogenic volatile organic compounds", International Journal of Mass Spectrometry, vol. 279, no. 2: Elsevier, pp. 126–133, 2009.
Abstract
Eucalypt contributions to biogenic sources of volatile organic compounds (VOCs) in Australia are estimated at teragram (Tg = 1012 g) amounts each year. Biogenic VOCs include plant-specific isoprenoids (isoprene and a range of terpenes) and other reactive organic compounds (i.e., acids, aldehydes and ketones). Atmospheric reactions of VOCs are numerous and many have significant environmental impact. Wildfires increase both the amounts of VOCs released and the complexity of their reactions. Proton-transfer reaction mass spectrometry (PTR-MS), gas chromatography mass spectrometry (GCMS) and direct analysis in real time (DART) mass spectrometry were applied to analyze release of VOCs as a function of temperatures ranging from ambient to combustion. PTR-MS enabled trace level analysis of VOCs from a complex forest atmosphere and revealed the release of terpenes associated with leaf damage during a storm. Temperature profile studies revealed ion abundances (i.e., emissions of VOCs) could be correlated with boiling points and vapor pressures of specific compounds. PTR-MS analysis of VOCs resulting from heating fresh leaf (E. grandis) material suggested that emissions of protonated methanol (m/z 33) and protonated acetaldehyde (m/z 45) were greatest at ∼60 °C while m/z 137 and 153 (associated with a series of terpenes) showed monotonic increases in ion abundance over a wide temperature range from ambient to 200 °C. GCMS analysis of fresh and senescent leaves of E. grandis showed that a series of VOCs (ethylvinylketone, diethylketone, 2-ethylfuran, hexanal and hexenals) are present only in fresh leaves while several terpenes (α and β pinenes, α-phellandrene, eucalyptol, γ-terpinene) were common in both. DART analysis of fresh leaf and stem of E. sideroxylon identified tissue-specific VOCs (e.g., methanol and ethanol were more abundant in stems). PTR-MS combustion studies of senescent leaves (E. grandis) identified two distinct, temperature-dependent VOC compositions. Before the appearance of smoke, the composition of VOCs remained consistent and correlated well with various naturally occurring isoprenoids, as observed in temperature profile studies. Sampling of eucalypt smoke suggested ions (m/z 75, 85, 87, 99, 111 and 125) correlated with protonated mass of oxygenated aldehydes, ketones, furans and substituted benzenes, and were due to pyrolysis of polycarbohydrates (cellulose and lignin) that are common in many types of wood.
[Amann2009] "Exhaled breath analysis-quantifying the storage of lipophilic compounds in the human body", Proceedings of Ecopole, vol. 3, pp. 9–13, 2009.
2008
[Keck2008] Keck, L., C. Hoeschen, and U. Oeh, "Effects of carbon dioxide in breath gas on proton transfer reaction-mass spectrometry (PTR-MS) measurements", International Journal of Mass Spectrometry, vol. 270, no. 3: Elsevier, pp. 156–165, 2008.
Abstract
PTR-MS is becoming a common method for the analysis of volatile organic compounds (VOCs) in human breath. Breath gas contains substantial and, particularly for bag samples, highly variable concentrations of water vapour (up to ∼6.3%) and carbon dioxide (up to ∼6.5%). The goal of this study was to investigate the effects of carbon dioxide on PTR-MS measurements; such effects can be expected in view of the already well known effects of water vapour. Carbon dioxide caused an increase of the pressure in the PTR-MS drift tube (∼1% increase for 5% CO2), and this effect was used to assess the CO2 concentration of breath gas samples along the way with the analysis of VOCs. Carbon dioxide enhanced the concentration ratio of protonated water clusters (H3O+H2O) to protonated water (H3O+) in the drift tube. Using the observed increase, being ∼60% for 5% CO2, it is estimated that the mobility of water cluster ions in pure CO2 is almost 65% lower than in air. Carbon dioxide had a significant effect on the mass spectra of the main breath gas components methanol, ethanol, 1-propanol, 2-propanol, acetone, and isoprene. Carbon dioxide caused a small increase (<10% for 5% CO2) of the normalised main signals for the non-fragmenting molecules methanol and acetone. The increase can be much higher for the fragmenting VOCs (ethanol, propanol, and isoprene) and was, for 5% CO2, up to ∼60% for ethanol. This effect of CO2 on fragment patterns is mainly a consequence of the increased abundance of protonated water clusters, which undergo softer reactions with VOCs than the hydronium ions. Breath gas samples stored in Teflon bags lost ∼80% of CO2 during 3 days, the decrease of VOC signals, however, is mainly attributed to decreasing VOC concentrations and to the loss of humidity from the bags.
[Kim2008] "Emissions and Photochemistry of BVOCs in a Ponderosa Pine woodland", AGU Fall Meeting Abstracts, vol. 1, pp. 0057, 2008.
Abstract
We deployed two proton-transfer-reaction mass spectrometry instruments (PTR-MS, IONICON ANALYTIK) for ambient and branch enclosure measurements at the Manitou Experimental Forest, located in the Southern Rocky Mountain area as a part of the Bio-hydro-atmosphere interactions of Energy, Aerosols, Carbon, H2O, Organics and Nitrogen (BEACHON) field campaign in 2008. Vegetation at the field site is dominated by Ponderosa Pine. BVOC emissions from Ponderosa Pine along with temperature, photosynthetic photon flux density (ppfd), relative humidity, and CO2 uptake were measured from two branch-enclosures (shade and sun). Diurnal variations and the emission response to environmental conditions are described and compared to existing models. In addition, we analyzed the speciation of BVOCs from enclosures by GC-MS. We will present quantitative and qualitative characteristics of BVOC emissions from Ponderosa Pine and analytical characteristics of PTR-MS such as fragmentation patterns of semi-volatile compounds (sesquiterpene, bornyl acetate etc) that we identified as major emissions from the enclosures. BVOC emissions observed in the enclosures will be quantitatively compared to BVOC distributions in ambient air. We explore the presence of possibly unidentified BVOCs in the forest canopy by examining PTR-MS mass spectra of enclosure and ambient air samples based on mass scans between 40 - 210 amu.
2007
[Song2007] "Effect of hydrophobic primary organic aerosols on secondary organic aerosol formation from ozonolysis of $\alpha$-pinene", Geophysical Research Letters, vol. 34, no. 20, 2007.
Abstract
Semi-empirical secondary organic aerosol (SOA) models typically assume a well-mixed organic aerosol phase even in the presence of hydrophobic primary organic aerosols (POA). This assumption significantly enhances the modeled SOA yields as additional organic mass is made available to absorb greater amounts of oxidized secondary organic gases than otherwise. We investigate the applicability of this critical assumption by measuring SOA yields from ozonolysis of α-pinene (a major biogenic SOA precursor) in a smog chamber in the absence and in the presence of dioctyl phthalate (DOP) and lubricating oil seed aerosol. These particles serve as surrogates for urban hydrophobic POA. The results show that these POA did not enhance the SOA yields. If these results are found to apply to other biogenic SOA precursors, then the semi-empirical models used in many global models would predict significantly less biogenic SOA mass and display reduced sensitivity to anthropogenic POA emissions than previously thought.
[1503] "Emission, oxidation, and secondary organic aerosol formation of volatile organic compounds as observed at Chebogue Point, Nova Scotia", Journal of Geophysical Research, vol. 112, 2007.
Abstract
<p>We report the detection of a class of related oxygenated compounds by proton-transfer-reaction mass-spectrometry (PTR-MS) that have rarely or never been observed as a group using in situ instrumentation. Measurements were made as part of the International Consortium for Atmospheric Research on Transport and Transformation (ICARTT) 2004 in Chebogue Point, Nova Scotia. The detected class of compounds discussed here includes acetic acid, formaldehyde, acetaldehyde, tentatively identified formic acid and hydroxyacetone, and unidentified compounds detected at mass to charge ratios 85, 87, 99, 101, 113, 115, and 129. Typical concentrations were 800, 2500, 450, 700, 85, 25, 50, 50, 60, 35, 20, and 25 ppt, respectively. The uniqueness of this class of compounds is illustrated by showing they were poorly related to trace gases found in the US outflow, local pollution, primary biogenic emissions and other oxygenated compounds such as acetone, methanol, and MEK measured by other in situ instrumentation. On the other hand these oxidized volatile organic compounds were related to chemical species in aerosols and their abundance was high during nucleation events. Thus they likely are gas phase species that are formed in parallel to biogenic secondary organic aerosol production. We clearly show these compounds do not originate from local sources. We also show these compounds match the oxidation products of isoprene observed in smog chamber studies, and we therefore suggest they must be mainly produced by oxidation of biogenic precursor compounds.</p>
[GomezAlvarez2007] "Experimental confirmation of the dicarbonyl route in the photo-oxidation of toluene and benzene.", Environ Sci Technol, vol. 41, no. 24: FundaciÃ³n Centro de Estudios Ambientales del MediterrÃ¡neo (CEAM), C/Charles Darwin 14, 46980 Paterna, Valencia, Spain. elena@ceam.es, pp. 8362–8369, Dec, 2007.
Abstract
The methodology of solid phase microextraction (SPME) with O-(2,3,4,5,6)-pentafluorobenzylhydroxylamine hydrochloride (PFBHA) on-fiber derivatization for the determination of carbonyls has been applied to the photo-oxidation of benzene and toluene carried out in the EUPHORE chambers. This work focuses on the results obtained for a number of highly reactive carbonyls, crucial in the determination of branching ratios and confirmation of the carbonylic route. The observed yields and kinetic behavior were compared to simulations with the Master Chemical Mechanism model, version 3.1 (MCMv3.1). The following yields were measured in the toluene system: glyoxal, (37 +/- 2)%; methylglyoxal, (37 +/- 2)%; 4-oxo-2-pentenal, > (13.8 +/- 1.5)%; and total butenedial, (13 +/- 7)% (cis-butenedial, (6 +/- 3)%; trans-butenedial, (7 +/- 4)%]. For benzene, the experimental glyoxal yields were (42 +/- 3) and (36 +/- 2)% for the two successive experiments (September 24 and 25, 2003), (17 +/- 9)% for total butenedial [(8 +/- 4)% cis-butenedial and (9 +/- 5)% trans-butenedial (September 24, 2003)] and (15 +/- 6)% total butenedial (September 25, 2003) [(7 +/- 3) and (7 +/- 3)% for the cis and trans isomers, respectively]. PTR-MS estimations for butenedial also allowed the two isomers of butenedial to be distinguished, but the measurements showed signs of interference from other products. The results presented confirm the fast ring cleavage and provide further experimental confirmation of the dicarbonylic route.
2006
[Klemm2006] "Experiments on forest/atmosphere exchange: Climatology and fluxes during two summer campaigns in NE Bavaria", Atmospheric Environment, vol. 40: Elsevier, pp. 3–20, 2006.
Abstract
During two summer field campaigns in 2001 and 2002, biosphere/atmosphere exchange fluxes of energy, gases, and particles were quantified in a Norway spruce forest in NE Bavaria at 775 m a.s.l. The overall goal of the BEWA campaigns was to study the influence of the emissions of reactive biogenic volatile organic compounds (BVOCs) on chemical and physical processes in the atmosphere, and an overview over the meteorological conditions, experimental frame, and the achieved results is provided. A rigorous quality assurance/quality control plan was implemented. From analysis of meteorological conditions and experimental success, golden day periods were selected for coordinated data analysis. These periods cover typical summertime conditions with various wind directions, NOx mixing ratios between 2 and 10 ppb, and O3 mixing ratios ranging between 13 and 98 ppb. Diurnal patterns of trace gas concentrations resulted from the dynamics of the boundary layer, from regional atmospheric processes (for example production of O3 in the atmosphere), and deposition. Turbulence also exhibited a diurnal pattern indicating thermal production during daytime and calm conditions during nighttime. However, in many cases, turbulence was often well developed during the nights. Horizontal advection of air masses into the trunk space occurred due to the patchiness of the forest. Nevertheless, for most conditions, the application of a one-dimensional model to describe the vertical exchange processes was appropriate. Therefore, the use of one single meteorological tower to study biosphere/atmosphere exchange is valid. Measured turbulent vertical exchange fluxes were estimated to be representative within an error of less than 25%. The results for VOC concentrations and fluxes were rather heterogeneous. Both model and measurements demonstrated that the Norway spruce trees acted as a weak source of formaldehyde.

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