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Scientific Articles - PTR-MS Bibliography

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Found 746 results
Title [ Year(Asc)]
2017
[1770] Hatch, L. E., R. J. Yokelson, C. E. Stockwell, P. R. Veres, I. J. Simpson, D. R. Blake, J. J. Orlando, and K. C. Barsanti, "Multi-instrument comparison and compilation of non-methane organic gas emissions from biomass burning and implications for smoke-derived secondary organic aerosol precursors", Atmospheric Chemistry and Physics, vol. 17, pp. 1471–1489, Jan, 2017.
Link: http://dx.doi.org/10.5194/acp-17-1471-2017
Abstract
<p>Multiple trace-gas instruments were deployed during the fourth Fire Lab at Missoula Experiment (FLAME-4), including the first application of proton-transfer-reaction time-of-flight mass spectrometry (PTR-TOFMS) and comprehensive two-dimensional gas chromatography&ndash;time-of-flight mass spectrometry (GC&thinsp;&times;&thinsp;GC-TOFMS) for laboratory biomass burning (BB) measurements. Open-path Fourier transform infrared spectroscopy (OP-FTIR) was also deployed, as well as whole-air sampling (WAS) with one-dimensional gas chromatography&ndash;mass spectrometry (GC-MS) analysis. This combination of instruments provided an unprecedented level of detection and chemical speciation. The chemical composition and emission factors (EFs) determined by these four analytical techniques were compared for four representative fuels. The results demonstrate that the instruments are highly complementary, with each covering some unique and important ranges of compositional space, thus demonstrating the need for multi-instrument approaches to adequately characterize BB smoke emissions. Emission factors for overlapping compounds generally compared within experimental uncertainty, despite some outliers, including monoterpenes. Data from all measurements were synthesized into a single EF database that includes over 500 non-methane organic gases (NMOGs) to provide a comprehensive picture of speciated, gaseous BB emissions. The identified compounds were assessed as a function of volatility; 6&ndash;11 % of the total NMOG EF was associated with intermediate-volatility organic compounds (IVOCs). These atmospherically relevant compounds historically have been unresolved in BB smoke measurements and thus are largely missing from emission inventories. Additionally, the identified compounds were screened for published secondary organic aerosol (SOA) yields. Of the total reactive carbon (defined as EF scaled by the OH rate constant and carbon number of each compound) in the BB emissions, 55&ndash;77 % was associated with compounds for which SOA yields are unknown or understudied. The best candidates for future smog chamber experiments were identified based on the relative abundance and ubiquity of the understudied compounds, and they included furfural, 2-methyl furan, 2-furan methanol, and 1,3-cyclopentadiene. Laboratory study of these compounds will facilitate future modeling efforts.</p>
2016
[1683] Nenadis, N., S. Heenan, M. Z. Tsimidou, and S. van Ruth, "Applicability of PTR-MS in the quality control of saffron", Food Chemistry, vol. 196, pp. 961–967, Apr, 2016.
Link: http://dx.doi.org/10.1016/j.foodchem.2015.10.032
Abstract
<p>{The applicability of the emerging non-destructive technique, proton transfer reaction mass spectrometry (PTR-MS), was explored for the first time in the quality control of saffron. Monitoring of volatile organic compounds (VOCs) was achieved using a minute sample (35 mg). Fresh saffron was stored under selected conditions (25 and 40 &deg;C</p>
[1717] Klein, F., S. M. Platt, N. J. Farren, A. Detournay, E. A. Bruns, C. Bozzetti, K. R. Daellenbach, D. Kilic, N. K. Kumar, S. M. Pieber, et al., "Characterization of Gas-Phase Organics Using Proton Transfer Reaction Time-of-Flight Mass Spectrometry: Cooking Emissions.", Environ Sci Technol, vol. 50, pp. 1243–1250, Feb, 2016.
Link: http://dx.doi.org/10.1021/acs.est.5b04618
Abstract
<p>Cooking processes produce gaseous and particle emissions that are potentially deleterious to human health. Using a highly controlled experimental setup involving a proton-transfer-reaction time-of-flight mass spectrometer (PTR-ToF-MS), we investigate the emission factors and the detailed chemical composition of gas phase emissions from a broad variety of cooking styles and techniques. A total of 95 experiments were conducted to characterize nonmethane organic gas (NMOG) emissions from boiling, charbroiling, shallow frying, and deep frying of various vegetables and meats, as well as emissions from vegetable oils heated to different temperatures. Emissions from boiling vegetables are dominated by methanol. Significant amounts of dimethyl sulfide are emitted from cruciferous vegetables. Emissions from shallow frying, deep frying and charbroiling are dominated by aldehydes of differing relative composition depending on the oil used. We show that the emission factors of some aldehydes are particularly large which may result in considerable negative impacts on human health in indoor environments. The suitability of some of the aldehydes as tracers for the identification of cooking emissions in ambient air is discussed.</p>
[1716] Schuhfried, E., J. {Sánchez Del Pulgar}, M. Bobba, R. Piro, L. Cappellin, T. D. Märk, and F. Biasioli, "Classification of 7 monofloral honey varieties by PTR-ToF-MS direct headspace analysis and chemometrics.", Talanta, vol. 147, pp. 213–219, Jan, 2016.
Link: http://dx.doi.org/10.1016/j.talanta.2015.09.062
Abstract
<p>Honey, in particular monofloral varieties, is a valuable commodity. Here, we present proton transfer reaction-time of flight-mass spectrometry, PTR-ToF-MS, coupled to chemometrics as a successful tool in the classification of monofloral honeys, which should serve in fraud protection against mispresentation of the floral origin of honey. We analyzed 7 different honey varieties from citrus, chestnut, sunflower, honeydew, robinia, rhododendron and linden tree, in total 70 different honey samples and a total of 206 measurements. Only subtle differences in the profiles of the volatile organic compounds (VOCs) in the headspace of the different honeys could be found. Nevertheless, it was possible to successfully apply 6 different classification methods with a total correct assignment of 81-99% in the internal validation sets. The most successful methods were stepwise linear discriminant analysis (LDA) and probabilistic neural network (PNN), giving total correct assignments in the external validation sets of 100 and 90%, respectively. Clearly, PTR-ToF-MS/chemometrics is a powerful tool in honey classification.</p>
[1681] Pallozzi, E., G. Guidolotti, P. Ciccioli, F. Brilli, S. Feil, and C. Calfapietra, "Does the novel fast-GC coupled with PTR-TOF-MS allow a significant advancement in detecting VOC emissions from plants?", Agricultural and Forest Meteorology, vol. 216, pp. 232–240, Jan, 2016.
Link: http://dx.doi.org/10.1016/j.agrformet.2015.10.016
Abstract
<p>Most plants produce and emit a wide blend of biogenic volatile organic compounds (BVOCs). Among them, many isoprenoids exhibit a high atmospheric reactivity toward OH radicals and ozone. In the last few years, Proton Transfer Reaction&ndash;Mass Spectrometry (PTR&ndash;MS) has been widely used in both field and laboratory determination of BVOCs, complementing the traditional methods using gas chromatography&ndash;mass spectrometry (GC&ndash;MS) for their identification in air and emission sources. This technical note reports a number of experiments carried out with a PTR- (Time-of-Flight) TOF-MS equipped with a prototype fast-GC system, allowing a fast separation of those isobaric isoprenoid compounds that cannot be identified by a direct PTR-TOF-MS analysis. The potential of this fast-GC system to adequately complement the information provided by PTR-TOF-MS was investigated by using the BVOC emissions of Quercus ilex and Eucalyptus camaldulensis as reliable testing systems, due to the different blend of isoprenoid compounds emitted and the different dependence of their emission from environmental parameters. While the oak species is a strong monoterpene emitter, the eucalyptus used is one of the few plant species emitting both isoprene and monoterpenes. The performances provided by the type of fast-GC used in the new PTR-TOF-MS instrument were also compared with those afforded by conventional GC&ndash;MS methods. The results obtained in this investigation showed that this new instrument is indeed a quick and handy tool to determine the contribution of isoprene and eucalyptol to m/z 69.070 and monoterpenes and (Z)-3-hexenal to m/z 81.070, integrating well the on-line information provided by PTR-TOF-MS. However, some limitations emerged in the instrument as compared to traditional GC&ndash;MS, which can only be solved by implementing the injection and separation processes.</p>
[1734] VÄISÄNEN, TANELI., "Effects of Thermally Extracted Wood Distillates on the Characteristics of Wood-Plastic Composites", Academic Dissertation, no. 222, Eastern Finland University Library / Sales of publications P.O. Box 107, FI-80101 Joensuu, Finland, Publications of the University of Eastern Finland Dissertations in Forestry and Natural Sciences, 2016.
Link: http://epublications.uef.fi/pub/urn_isbn_978-952-61-2124-6/index_en.html
Abstract
<p>The use of raw materials derived from renewable sources is increasing due to the finiteness of crude oil reserves. In wood-plastic composites (WPCs), the plastic in a material is partially replaced by wood, which is an abundantly available and inexpensive raw material. WPCs are materials that encompass a wide range of performance levels such that they have diverse applications, e.g., in fencing and decking as well as in the manufacture of automobiles. The use of WPCs in indoor applications is also becoming increasingly popular. Despite the increasing popularity of WPCs, certain inherent limitations mean that these materials are unsuitable for some applications. Examples of the limitations associated with WPCs are their insufficient mechanical strength and their susceptibility to excess water absorption. Furthermore, the VOC (volatile organic compound) characteristics of WPCs have not been widely studied and therefore, a better understanding of these properties of WPCs would be of great importance. The properties of WPCs and their constituents can be altered by incorporating additives. However, some additives are rather expensive and their incorporation into WPCs is not straightforward. There is a clear need for novel, affordable and effective filler materials, especially those that would minimize the use of expensive constituents. Wood distillates are products originating from thermal processes where the components of wood are partly or completely decomposed into charcoal, condensable vapors, and non-condensable gases. Although the liquid components of wood have many potential applications, large volumes of liquids are still being discarded and not exploited in industrial applications. Thus, the incorporation of more of wood distillates into WPCs would enhance the use of raw materials and secondary products from the wood-processing industries. This would be both economically valuable and environmentally friendly since it would represent sustainable development by making commercial use of a potentially hazardous waste product. The main aim of this thesis was to investigate whether wood distillates could be used as WPC components. Another aim was to assess the possibility to improve the mechanical properties and water resistance of the WPCs with wood distillates. Furthermore, the applicability of proton-transfer-reaction time-of-flight massspectrometry (PTR-TOF-MS) in determining the VOC emission characteristics of WPCs was studied. The effects of incorporating hardwood and softwood distillates into WPCs were examined by characterizing the mechanical properties, water resistance and VOC emissions of these WPCs modified with the distillates. The distillate content varied from 1 wt% to 20 wt%. The suitability of PTR-TOF-MS for analyzing VOC emissions from WPCs was assessed by measuring VOC emissions from a WPC deck during a 41-day trial and comparing VOC emission rates between seven different WPC decks. Both hardwood and softwood distillates exerted positive effects on the water resistance of the WPC; the addition of hardwood distillate decreased the water absorption of the WPC by over 25% whereas at least a 16% decrease was observed for the WPC with the softwood distillate. Moreover, a 1 wt% addition of hardwood distillate into the WPC led to a highly significant increase (11.5%, p &lt; 0.01) in the tensile modulus as well as achieving minor enhancements in some other mechanical properties. Similarly, when 2 wt% of softwood was added to the WPC, a highly significant increase in the tensile strength (5.0%, p &lt; 0.01) was observed. Even though the addition of the distillates increased the total release of VOCs, the emission rates of harmful compounds, such as benzene, remained low. Nonetheless, the results from the VOC analyses indicated that some of the compounds investigated in this thesis may be smelled from the WPCs because their odor thresholds were exceeded. Wood distillates displayed good potential as natural additives in WPCs as they improved the mechanical properties and water resistance. The results of this thesis provide a basis for the further development of wood distillates as bio-based additives in WPCs</p>
[1735] Sukul, P., J. K. Schubert, P. Oertel, S. Kamysek, K. Taunk, P. Trefz, and W. Miekisch, "FEV manoeuvre induced changes in breath VOC compositions: an unconventional view on lung function tests", Scientific Reports, vol. 6, pp. 28029, Jun, 2016.
Link: http://dx.doi.org/10.1038/srep28029
Abstract
Breath volatile organic compound (VOC) analysis can open a non-invasive window onto pathological and metabolic processes in the body. Decades of clinical breath-gas analysis have revealed that changes in exhaled VOC concentrations are important rather than disease specific biomarkers. As physiological parameters, such as respiratory rate or cardiac output, have profound effects on exhaled VOCs, here we investigated VOC exhalation under respiratory manoeuvres. Breath VOCs were monitored by means of real-time mass-spectrometry during conventional FEV manoeuvres in 50 healthy humans. Simultaneously, we measured respiratory and hemodynamic parameters noninvasively. Tidal volume and minute ventilation increased by 292 and 171% during the manoeuvre. FEV manoeuvre induced substance specific changes in VOC concentrations. pET-CO2 and alveolar isoprene increased by 6 and 21% during maximum exhalation. Then they decreased by 18 and 37% at forced expiration mirroring cardiac output. Acetone concentrations rose by 4.5% despite increasing minute ventilation. Blood-borne furan and dimethyl-sulphide mimicked isoprene profile. Exogenous acetonitrile, sulphides, and most aliphatic and aromatic VOCs changed minimally. Reliable breath tests must avoid forced breathing. As isoprene exhalations mirrored FEV performances, endogenous VOCs might assure quality of lung function tests. Analysis of exhaled VOC concentrations can provide additional information on physiology of respiration and gas exchange.
[1764] Morozova, K., A. Romano, F. Lonardi, R. Ferrarini, F. Biasioli, and M. Scampicchio, "Microcalorimetric monitoring of grape withering", Thermochimica Acta, vol. 630, pp. 31–36, Apr, 2016.
Link: http://dx.doi.org/10.1016/j.tca.2016.01.011
Abstract
<p>tThis work aimed at monitoring the metabolic activity of grapes during withering by microcalorimetry.Samples of Corvina grapes, a cultivar used in the production of Amarone wine, were dehydrated for about120 days at an industrial scale plants (fruttaia). Single berries, sampled in the course of the witheringprocess, were closed in ampoules and maintained at constant temperature. As biochemical events (i.e.berry respiration, microbial growth, etc.) are always accompanied by the production of heat (q), the heat-flow (dq/dt) emitted by berries enclosed in the ampoules was used to monitor their metabolic activityduring withering, i.e. respiration. For each sampling time, the heat rate production of the berries at 298 Kwas monitored till a steady state signal was achieved (within 60 h). Such heat flow value was used asmarker during the entire withering process (120 days). Its trend allowed to characterize the changesin the metabolic activity of the grape berries along the withering process. To understand the origin ofsuch changes, the emission of volatile organic compounds (VOCs) were also measured by proton transfermass spectrometry (PTR-MS). The use of microcalorimetry associated with the analysis of specific VOCsfragments offered a valuable information to describe the withering process.</p>
[1738] Hansen, M. J., K. E. N. Jonassen, M. Marie Lokke, A. Peter S. Adamsen, and A. Feilberg, "Multivariate prediction of odor from pig production based on in-situ measurement of odorants", Atmospheric Environment, vol. 135, pp. 50–58, Jun, 2016.
Link: http://dx.doi.org/10.1016/j.atmosenv.2016.03.060
Abstract
<p>The aim of the present study was to estimate a prediction model for odor from pig production facilities based on measurements of odorants by Proton-Transfer-Reaction Mass spectrometry (PTR-MS). Odor measurements were performed at four different pig production facilities with and without odor abatement technologies using a newly developed mobile odor laboratory equipped with a PTR-MS for measuring odorants and an olfactometer for measuring the odor concentration by human panelists. A total of 115 odor measurements were carried out in the mobile laboratory and simultaneously air samples were collected in Nalophan bags and analyzed at accredited laboratories after 24 h. The dataset was divided into a calibration dataset containing 94 samples and a validation dataset containing 21 samples. The prediction model based on the measurements in the mobile laboratory was able to explain 74% of the variation in the odor concentration based on odorants, whereas the prediction models based on odor measurements with bag samples explained only 46&ndash;57%. This study is the first application of direct field olfactometry to livestock odor and emphasizes the importance of avoiding any bias from sample storage in studies of odor-odorant relationships. Application of the model on the validation dataset gave a high correlation between predicted and measured odor concentration (R2 = 0.77). Significant odorants in the prediction models include phenols and indoles. In conclusion, measurements of odorants on-site in pig production facilities is an alternative to dynamic olfactometry that can be applied for measuring odor from pig houses and the effects of odor abatement technologies.</p>
[1688] Breiev, K., K. M. M. Burseg, G. OConnell, E. Hartungen, S. S. Biel, X. Cahours, S. Colard, T. D. Maerk, and P. Sulzer, "An online method for the analysis of volatile organic compounds in electronic cigarette aerosol based on proton transfer reaction mass spectrometry", Rapid Commun. Mass Spectrom., vol. 30, pp. 691–697, Feb, 2016.
Link: http://dx.doi.org/10.1002/rcm.7487
Abstract
<p>Rationale Due to the recent rapid increase in electronic cigarette (e-cigarette) use worldwide, there is a strong scientific but also practical interest in analyzing e-cigarette aerosols. Most studies to date have used standardized but time-consuming offline technologies. Here a proof-of-concept for a fast online quantification setup based on proton transfer reaction mass spectrometry (PTR-MS) is presented. Methods The combination of a novel sampling interface with a time-of-flight PTR-MS instrument specially designed for three scenarios is introduced: (i) mainstream aerosol analysis (aerosol that the user inhales prior to exhalation), and analysis of exhaled breath following (ii) mouth-hold (no inhalation) and (iii) inhalation of e-cigarette aerosols. A double-stage dilution setup allows the various concentration ranges in these scenarios to be accessed. Results First, the instrument is calibrated for the three principal constituents of the e-cigarettes&#39; liquids, namely propylene glycol, vegetable glycerol and nicotine. With the double-stage dilution the instrument&#39;s dynamic range was easily adapted to cover the concentration ranges obtained in the three scenarios: 20&ndash;1100 ppmv for the mainstream aerosol characterisation; 4&ndash;300 ppmv for the mouth-hold; and 2 ppbv to 20 ppmv for the inhalation experiment. Conclusions It is demonstrated that the novel setup enables fast, high time resolution e-cigarette studies with online quantification. This enables the analysis and understanding of any puff-by-puff variations in e-cigarette aerosols. Large-scale studies involving a high number of volunteers will benefit from considerably higher sample throughput and shorter data processing times.</p>
[1713] Farré-Armengol, G., J. Penuelas, T. Li, P. Yli-Pirilä, I. Filella, J. Llusia, and J. D. Blande, "Ozone degrades floral scent and reduces pollinator attraction to flowers.", New Phytol, vol. 209, pp. 152–160, Jan, 2016.
Link: http://dx.doi.org/10.1111/nph.13620
Abstract
<p>In this work we analyzed the degradation of floral scent volatiles from Brassica nigra by reaction with ozone along a distance gradient and the consequences for pollinator attraction. For this purpose we used a reaction system comprising three reaction tubes in which we conducted measurements of floral volatiles using a proton-transfer-reaction time-of-flight mass spectrometer (PTR-TOF-MS) and GC-MS. We also tested the effects of floral scent degradation on the responses of the generalist pollinator Bombus terrestris. The chemical analyses revealed that supplementing air with ozone led to an increasing reduction in the concentrations of floral volatiles in air with distance from the volatile source. The results revealed different reactivities with ozone for different floral scent constituents, which emphasized that ozone exposure not only degrades floral scents, but also changes the ratios of compounds in a scent blend. Behavioural tests revealed that floral scent was reduced in its attractiveness to pollinators after it had been exposed to 120&nbsp;ppb O3 over a 4.5&nbsp;m distance. The combined results of chemical analyses and behavioural responses of pollinators strongly suggest that high ozone concentrations have significant negative impacts on pollination by reducing the distance over which floral olfactory signals can be detected by pollinators.</p>
[1724] Capozzi, V., S. Makhoul, E. Aprea, A. Romano, L. Cappellin, A. Sanchez Jimena, G. Spano, F. Gasperi, M. Scampicchio, and F. Biasioli, "PTR-{MS} Characterization of VOCs Associated with Commercial Aromatic Bakery Yeasts of Wine and Beer Origin", Molecules, vol. 21, pp. 483, Apr, 2016.
Link: http://dx.doi.org/10.3390/molecules21040483
Abstract
<p>In light of the increasing attention towards &ldquo;green&rdquo; solutions to improve food quality, the use of aromatic-enhancing microorganisms offers the advantage to be a natural and sustainable solution that did not negatively influence the list of ingredients. In this study, we characterize, for the first time, volatile organic compounds (VOCs) associated with aromatic bakery yeasts. Three commercial bakery starter cultures, respectively formulated with three Saccharomyces cerevisiae strains, isolated from white wine, red wine, and beer, were monitored by a proton-transfer-reaction time-of-flight mass spectrometer (PTR-ToF-MS), a direct injection analytical technique for detecting volatile organic compounds with high sensitivity (VOCs). Two ethanol-related peaks (m/z 65.059 and 75.080) described qualitative differences in fermentative performances. The release of compounds associated to the peaks at m/z 89.059, m/z 103.075, and m/z 117.093, tentatively identified as acetoin and esters, are coherent with claimed flavor properties of the investigated strains. We propose these mass peaks and their related fragments as biomarkers to optimize the aromatic performances of commercial preparations and for the rapid massive screening of yeast collections.</p>
[1712] Masi, E.., C.. Taiti, D.. Heimler, P.. Vignolini, A.. Romani, and S.. Mancuso, "PTR-TOF-MS and HPLC analysis in the characterization of saffron (Crocus sativus L.) from Italy and Iran.", Food Chem, vol. 192, pp. 75–81, Feb, 2016.
Link: http://dx.doi.org/10.1016/j.foodchem.2015.06.090
Abstract
<p>Saffron samples from Italy and Iran were analyzed for their content in aroma and bioactive compounds with different analytical techniques. HPLC was used for the identification and quantification of crocins, picrocrocin, safranal and flavonoids content, while the novel proton transfer reaction time-of-flight mass spectrometer was employed for the aroma compounds analysis. Italian saffron turned out to be richer in total crocins and safranal contents. Sample characterization was performed with an unsupervised statistical approach; tests involving different numbers of parameters deriving from the two analytical techniques were performed. The results achieved showed that the best samples classification was obtained by joining the information acquired from both techniques; following such an approach, a sharper separation between Iranian and Italian samples was achieved. Finally, among the variables that most contribute to the description of variability, isophorone, safranal and picrocrocin were identified to be the most significant.</p>
[1718] Sahu, L.. K., R. Yadav, and D. Pal, "Source identification of VOCs at an urban site of western India: Effect of marathon events and anthropogenic emissions", J. Geophys. Res. Atmos., pp. n/a–n/a, 2016.
Link: http://dx.doi.org/10.1002/2015JD024454
Abstract
<p>Ambient volatile organic compounds (VOCs) were measured using a high-resolution proton transfer reaction-time of flight-mass spectrometer at an urban site of Ahmedabad in India during the winter season in 2014. Mixing ratios of VOCs show large diurnal and day-to-day variations. Although strongly influenced by local emissions, periods of higher VOCs were observed during transport from the polluted Indo-Gangetic Plains than those from the cleaner Thar Desert. However with different rates, VOCs decreased exponentially with increasing wind speed. Relative abundance of methanol varied with weather conditions contributing highest and lowest under fog and clear-sky conditions, respectively. Among the compounds reported here, oxygenated VOCs (OVOCs) contribute to a large fraction (67&ndash;85%) with methanol being most abundant (40&ndash;58%). In spite of predominant vehicular emissions, diurnal distribution and emission ratios (ERs) of several VOCs indicate the role of biogenic and secondary sources. The ratios of isoprene/benzene and OVOCs/benzene show significant enhancements during daytime suggesting their contributions from biogenic and secondary sources. During marathon and cyclothon events, mixing ratios of VOCs were 2&ndash;10 times higher compared to a normal Sunday. The ERs of VOCs estimated using the nighttime data on marathon day are well within the range of values reported for several megacities of the world. The average contributions of primary anthropogenic sources to acetaldehyde, acetone, and isoprene were 44&thinsp;&plusmn;&thinsp;06%, 45&thinsp;&plusmn;&thinsp;07%, and 63&thinsp;&plusmn;&thinsp;12%, respectively. During cloudy condition, the increase in anthropogenic contribution to acetaldehyde (&nbsp;10%), acetone (9%) and isoprene (30%) is due to reduction in biogenic emissions and secondary formation of these VOCs.</p>
[1765] Peinado, I.., M.. Mason, A.. Romano, F.. Biasioli, and M.. Scampicchio, "Stability of beta-carotene in polyethylene oxide electrospun nanofibers", Applied Surface Science, vol. 370, pp. 111–116, May, 2016.
Link: http://dx.doi.org/10.1016/j.apsusc.2016.02.150
Abstract
<p>b-carotene (bc) was successfully incorporated into electrospun nanofibers of poly-(ethylene oxide) (PEO)with the aim of prolonging its shelf life and thermal stability. The physical and thermal properties of the bc-PEO-nanofibers were determined by scanning electron microscopy (SEM), color analysis, and differ-ential scanning calorimetry (DSC). The nanofibers of PEO and bc-PEO exhibited average fiber diameters of320 &plusmn; 46 and 230 &plusmn; 21 nm, with colorimetric coordinates L* = 95.7 &plusmn; 2.4 and 89.4 &plusmn; 4.6 and b* = &minus;0.5 &plusmn; 0.1and 6.2 &plusmn; 3.0 respectively. Thermogravimetric analysis coupled with Proton Transfer&ndash;Mass Spectroscopy(TGA/PTR-MS) demonstrated that coated bc inside PEO nanofibers increased thermal stability when compared to standard bc in powder form. In addition, b-carotene in the membranes showed higher stabilityduring storage when compared with b-carotene in solution with a decrease in concentration of 57 &plusmn; 4%and 70 &plusmn; 2% respectively, thus should extend the shelf life of this compound. Also, TGA coupled withPTR&ndash;MS resulted in a promising technique to online-monitoring thermal degradation.</p>
2015
[1582] Beale, R., J. L. Dixon, T. J. Smyth, and P. D. Nightingale, "Annual study of oxygenated volatile organic compounds in UK shelf waters", Marine Chemistry, vol. 171, pp. 96¬106, Apr, 2015.
Link: http://dx.doi.org/10.1016/j.marchem.2015.02.013
Abstract
We performed an annual study of oxygenated volatile organic compound (OVOC) seawater concentrations at a site off Plymouth, UK in the Western English Channel over the period of February 2011–March 2012. Acetone concentrations ranged from 2–10 nM (nanomole/L) in surface waters with a maximum observed in summer. Concentrations correlated positively with net shortwave radiation and UV light, suggestive of photochemically linked acetone production. We observed a clear decline in acetone concentrations below the mixed layer. Acetaldehyde varied between 4–37 nM in surface waters with higher values observed in autumn and winter. Surface concentrations of methanol ranged from 16–78 nM, but no clear annual cycle was observed. Methanol concentrations exhibited considerable inter-annual variability. We estimate consistent deposition to the sea surface for acetone and methanol but that the direction of the acetaldehyde flux varies during the year
[1612] Feilberg, A., P. Bildsoe, and T. Nyord, "Application of PTR-MS for measuring odorant emissions from soil application of manure slurry.", Sensors (Basel), vol. 15, pp. 1148–1167, 2015.
Link: http://dx.doi.org/10.3390/s150101148
Abstract
<p>Odorous volatile organic compounds (VOC) and hydrogen sulfide (H2S) are emitted together with ammonia (NH3) from manure slurry applied as a fertilizer, but little is known about the composition and temporal variation of the emissions. In this work, a laboratory method based on dynamic flux chambers packed with soil has been used to measure emissions from untreated pig slurry and slurry treated by solid-liquid separation and ozonation. Proton-transfer-reaction mass spectrometry (PTR-MS) was used to provide time resolved data for a range of VOC, NH3 and H2S. VOC included organic sulfur compounds, carboxylic acids, phenols, indoles, alcohols, ketones and aldehydes. H2S emission was remarkably observed to take place only in the initial minutes after slurry application, which is explained by its high partitioning into the air phase. Long-term odor effects are therefore assessed to be mainly due to other volatile compounds with low odor threshold values, such as 4-methylphenol. PTR-MS signal assignment was verified by comparison to a photo-acoustic analyzer (NH3) and to thermal desorption GC/MS (VOC). Due to initial rapid changes in odorant emissions and low concentrations of odorants, PTR-MS is assessed to be a very useful method for assessing odor following field application of slurry. The effects of treatments on odorant emissions are discussed.</p>
[1761] Misztal, P.K.., C.N.. Hewitt, J.. Wildt, J.D.. Blande, A.S.D.. Eller, S.. Fares, D.R.. Gentner, J.B.. Gilman, M.. Graus, J.. Greenberg, et al., "Atmospheric benzenoid emissions from plants rival those from fossil fuels", Scientific Reports, vol. 5, pp. 12064, Jul, 2015.
Link: http://dx.doi.org/10.1038/srep12064
Abstract
<p>Despite the known biochemical production of a range of aromatic compounds by plants and the presence of benzenoids in floral scents, the emissions of only a few benzenoid compounds have been reported from the biosphere to the atmosphere. Here, using evidence from measurements at aircraft, ecosystem, tree, branch and leaf scales, with complementary isotopic labeling experiments, we show that vegetation (leaves, flowers, and phytoplankton) emits a wide variety of benzenoid compounds to the atmosphere at substantial rates. Controlled environment experiments show that plants are able to alter their metabolism to produce and release many benzenoids under stress conditions. The functions of these compounds remain unclear but may be related to chemical communication and protection against stress. We estimate the total global secondary organic aerosol potential from biogenic benzenoids to be similar to that from anthropogenic benzenoids (&nbsp;10&thinsp;Tg y&minus;1), pointing to the importance of these natural emissions in atmospheric physics and chemistry.</p>
[1644] Stojić, A.., S. S Stojić, A.. Šoštarić, L.. Ilić, Z.. Mijić, and S.. Rajšić, "Characterization of VOC sources in an urban area based on PTR-MS measurements and receptor modelling.", Environ Sci Pollut Res Int, May, 2015.
Link: http://dx.doi.org/10.1007/s11356-015-4540-5
Abstract
<p>In this study, the concentrations of volatile organic compounds were measured by the use of proton transfer reaction mass spectrometry, together with NO x , NO, NO2, SO2, CO and PM10 and meteorological parameters in an urban area of Belgrade during winter 2014. The multivariate receptor model US EPA Unmix was applied to the obtained dataset resolving six source profiles, which can be attributed to traffic-related emissions, gasoline evaporation/oil refineries, petrochemical industry/biogenic emissions, aged plumes, solid-fuel burning and local laboratories. Besides the vehicle exhaust, accounting for 27.6&nbsp;% of the total mixing ratios, industrial emissions, which are present in three out of six resolved profiles, exert a significant impact on air quality in the urban area. The major contribution of regional and long-range transport was determined for source profiles associated with petrochemical industry/biogenic emissions (40&nbsp;%) and gasoline evaporation/oil refineries (29&nbsp;%) using trajectory sector analysis. The concentration-weighted trajectory model was applied with the aim of resolving the spatial distribution of potential distant sources, and the results indicated that emission sources from neighbouring countries, as well as from Slovakia, Greece, Poland and Scandinavian countries, significantly contribute to the observed concentrations.</p>
[1763] Kaser, L.., T.. Karl, B.. Yuan, R.. L. Mauldin, C.. A. Cantrell, A.. B. Guenther, E.. G. Patton, A.. J. Weinheimer, C.. Knote, J.. Orlando, et al., "Chemistry-turbulence interactions and mesoscale variability influence the cleansing efficiency of the atmosphere", Geophysical Research Letters, vol. 42, pp. 10894–10903, Dec, 2015.
Link: http://n2t.net/ark:/85065/d7gq709d
Abstract
<p>The hydroxyl radical (OH) is the most important oxidant in the atmosphere and the primary sink for isoprene, the dominant volatile organic compound emitted by vegetation. Recent research on the atmospheric oxidation capacity in isoprene-dominated environments has suggested missing radical sources leading to significant overestimation of the lifetime of isoprene. Here we report, for the first time, a comprehensive experimental budget of isoprene in the planetary boundary layer based on airborne flux measurements along with in situ OH observations in the Southeast and Central U.S. Our findings show that surface heterogeneity of isoprene emissions lead to a physical separation of isoprene and OH resulting in an effective slowdown in the chemistry. Depending on surface heterogeneity, the intensity of segregation (Is) could locally slow down isoprene chemistry up to 30%. The effect of segregated reactants in the planetary boundary layer on average has an influence on modeled OH radicals that is comparable to that of recently proposed radical recycling mechanisms.</p>
[1645] Ciesa, F., I. Höller, W. Guerra, J. Berger, J. {Dalla Via}, and M. Oberhuber, "Chemodiversity in the Fingerprint Analysis of Volatile Organic Compounds (VOCs) of 35 Old and 7 Modern Apple Cultivars Determined by Proton-Transfer-Reaction Mass Spectrometry (PTR-MS) in Two Different Seasons.", Chem Biodivers, vol. 12, pp. 800–812, May, 2015.
Link: http://dx.doi.org/10.1002/cbdv.201400384
Abstract
<p>Volatile organic compounds (VOCs) are chemical species that play an important role in determining the characteristic aroma and flavor of fruits. Apple (Malus &times; domestica Borkh.) cultivars differ in their aroma and composition of VOCs. To determine varietal differences in the aroma profiles, VOCs emitted by 7 modern and 35 old apple cultivars were analyzed using Proton Transfer Reaction Mass Spectrometry (PTR-MS). PTR-MS is a rapid, reproducible, and non-destructive spectrometric technique for VOC analysis of single fruits, developed for direct injection analysis. In the present study, we analyzed the differences in the emission of VOCs from single fruits at harvest and after a storage period of 60&plusmn;10 days, followed by 3 d of shelf life. Our results show that VOC profile differences among apple cultivars were more pronounced after storage than at harvest. Furthermore, chemodiversity was higher in old cultivars compared to modern cultivars, probably due to their greater genetic variability. Our data highlight the importance of storage and shelf life are crucial for the development of the typical aroma and flavor of several apple cultivars. The validity of the method is demonstrated by comparison of two different harvest years.</p>
[1635] Kus, P. Marek, and S. van Ruth, "Discrimination of Polish unifloral honeys using overall PTR-{MS} and HPLC fingerprints combined with chemometrics", LWT - Food Science and Technology, vol. 62, pp. 69–75, Jun, 2015.
Link: http://dx.doi.org/10.1016/j.lwt.2014.12.060
Abstract
<p>A total of 62 honey samples of six floral origins (rapeseed, lime, heather, cornflower, buckwheat and black locust) were analysed by means of proton transfer reaction mass spectrometry (PTR-MS) and HPLCDAD. The data were evaluated by principal component analysis and k-nearest neighbours classification in order to examine consistent differences in analytical fingerprints between various honeys allowing their discrimination. The study revealed, that both techniques were able to distinguish the floral origins, however the HPLC shows advantage over PTR-MS providing substantially better differentiation of all analysed honey types. Especially HPLC fingerprints recorded at 210 nm were most suitable for discrimination of botanical origin with the use of chemometric analysis. The obtained classification rates were: 100%, 93%, 100%, 83%, 100%, 100% (HPLC) and 69%, 67%, 78%, 67%, 100%, 88% (PTR-MS) for rapeseed, lime, heather, cornflower, buckwheat and black locust, respectively. Even if performance of PTR-MS in general was lower than HPLC, it might be useful for fast on-line screening of buckwheat honey.</p>
[1760] Seco, R., T. Karl, A. Guenther, K. P. Hosman, S. G. Pallardy, L. Gu, C. Geron, P. Harley, and S. Kim, "Ecosystem-scale volatile organic compound fluxes duringᅡᅠan extreme drought in a broadleaf temperate forestᅡᅠof the Missouri Ozarks (central USA)", Global Change Biology, vol. 21, pp. 3657–3674, Jul, 2015.
Link: http://dx.doi.org/10.1111/gcb.12980
Abstract
<p>Considerable amounts and varieties of biogenic volatile organic compounds (BVOCs) are exchanged between vegetation and the surrounding air. These BVOCs play key ecological and atmospheric roles that must be adequately represented for accurately modeling the coupled biosphere-atmosphere-climate earth system. One key uncertainty in existing models is the response of BVOC fluxes to an important global change process: drought. We describe the diurnal and seasonal variation in isoprene, monoterpene, and methanol fluxes from a temperate forest ecosystem before, during, and after an extreme 2012 drought event in the Ozark region of the central USA. BVOC fluxes were dominated by isoprene, which attained high emission rates of up to 35.4 mg m(-2) h(-1) at midday. Methanol fluxes were characterized by net deposition in the morning, changing to a net emission flux through the rest of the daylight hours. Net flux of CO2 reached its seasonal maximum approximately a month earlier than isoprenoid fluxes, which highlights the differential response of photosynthesis and isoprenoid emissions to progressing drought conditions. Nevertheless, both processes were strongly suppressed under extreme drought, although isoprene fluxes remained relatively high compared to reported fluxes from other ecosystems. Methanol exchange was less affected by drought throughout the season, confirming the complex processes driving biogenic methanol fluxes. The fraction of daytime (7-17 h) assimilated carbon released back to the atmosphere combining the three BVOCs measured was 2% of gross primary productivity (GPP) and 4.9% of net ecosystem exchange (NEE) on average for our whole measurement campaign, while exceeding 5% of GPP and 10% of NEE just before the strongest drought phase. The meganv2.1 model correctly predicted diurnal variations in fluxes driven mainly by light and temperature, although further research is needed to address model BVOC fluxes during drought events.</p>
[1624] Hu, L., D. B. Millet, M. Baasandorj, T. J. Griffis, K. R. Travis, C. W. Tessum, J. D. Marshall, W. F. Reinhart, T. Mikoviny, M. Müller, et al., "Emissions of C 6 -C 8 aromatic compounds in the United States: Constraints from tall tower and aircraft measurements", Journal of Geophysical Research: Atmospheres, vol. 120, pp. 826–842, Jan, 2015.
Link: http://dx.doi.org/10.1002/2014JD022627
Abstract
<p>We present two full years of continuous C6&ndash;C8 aromatic compound measurements by PTR-MS at the KCMP tall tower (Minnesota, US) and employ GEOS-Chem nested grid simulations in a Bayesian inversion to interpret the data in terms of new constraints on US aromatic emissions. Based on the tall tower data, we find that the RETRO inventory (year-2000) overestimates US C6&ndash;C8 aromatic emissions by factors of 2.0&ndash;4.5 during 2010&ndash;2011, likely due in part to post-2000 reductions. Likewise, our implementation of the US EPA&#39;s NEI08 overestimates the toluene flux by threefold, reflecting an inventory bias in non-road emissions plus uncertainties associated with species lumping. Our annual top-down emission estimates for benzene and C8 aromatics agree with the NEI08 bottom-up values, as does the inferred contribution from non-road sources. However, the NEI08 appears to underestimate on-road emissions of these compounds by twofold during the warm season. The implied aromatic sources upwind of North America are more than double the prior estimates, suggesting a substantial underestimate of East Asian emissions, or large increases there since 2000. Long-range transport exerts an important influence on ambient benzene over the US: on average 43% of its wintertime abundance in the US Upper Midwest is due to sources outside North America. Independent aircraft measurements show that the inventory biases found here for C6&ndash;C8 aromatics also apply to other parts of the US, with notable exceptions for toluene in California and Houston, Texas. Our best estimates of year-2011 contiguous US emissions are 206 (benzene), 408 (toluene), and 822 (C8 aromatics) GgC.</p>
[1637] Wood, E. C., B. W Knighton, E. C. Fortner, S. C. Herndon, T. B. Onasch, J. P. Franklin, D. R. Worsnop, T. R. Dallmann, D. R. Gentner, A. H. Goldstein, et al., "Ethylene glycol emissions from on-road vehicles.", Environ Sci Technol, vol. 49, pp. 3322–3329, Mar, 2015.
Link: http://dx.doi.org/10.1021/acs.est.5b00557
Abstract
<p>Ethylene glycol (HOCH2CH2OH), used as engine coolant for most on-road vehicles, is an intermediate volatility organic compound (IVOC) with a high Henry&#39;s law coefficient. We present measurements of ethylene glycol (EG) vapor in the Caldecott Tunnel near San Francisco, using a proton transfer reaction mass spectrometer (PTR-MS). Ethylene glycol was detected at mass-to-charge ratio 45, usually interpreted as solely coming from acetaldehyde. EG concentrations in bore 1 of the Caldecott Tunnel, which has a 4% uphill grade, were characterized by infrequent (approximately once per day) events with concentrations exceeding 10 times the average concentration, likely from vehicles with malfunctioning engine coolant systems. Limited measurements in tunnels near Houston and Boston are not conclusive regarding the presence of EG in sampled air. Previous PTR-MS measurements in urban areas may have overestimated acetaldehyde concentrations at times due to this interference by ethylene glycol. Estimates of EG emission rates from the Caldecott Tunnel data are unrealistically high, suggesting that the Caldecott data are not representative of emissions on a national or global scale. EG emissions are potentially important because they can lead to the formation of secondary organic aerosol following oxidation in the atmospheric aqueous phase.</p>

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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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