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Scientific Articles - PTR-MS Bibliography

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Found 767 results
Title [ Year(Asc)]
2016
[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>
[1819] Sarkar, C., V. Sinha, V. Kumar, M. Rupakheti, A. Panday, K. S. Mahata, D. Rupakheti, B. Kathayat, and M. G. Lawrence, "Overview of {VOC} emissions and chemistry from {PTR}-{TOF}-{MS} measurements during the {SusKat}-{ABC} campaign: high acetaldehyde, isoprene and isocyanic acid in wintertime air of the Kathmandu Valley", Atmospheric Chemistry and Physics, vol. 16, pp. 3979–4003, mar, 2016.
Link: https://www.atmos-chem-phys.net/16/3979/2016/acp-16-3979-2016.pdf
Abstract
<p>The Kathmandu Valley in Nepal suffers from severe wintertime air pollution. Volatile organic compounds (VOCs) are key constituents of air pollution, though their specific role in the valley is poorly understood due to insufficient data. During the SusKat-ABC (Sustainable Atmosphere for the Kathmandu Valley&ndash;Atmospheric Brown Clouds) field campaign conducted in Nepal in the winter of 2012&ndash;2013, a comprehensive study was carried out to characterise the chemical composition of ambient Kathmandu air, including the determination of speciated VOCs, by deploying a proton transfer reaction time-of-flight mass spectrometer (PTR-TOF-MS) &ndash; the first such deployment in South Asia. In the study, 71 ion peaks (for which measured ambient concentrations exceeded the 2σ detection limit) were detected in the PTR-TOF-MS mass scan data, highlighting the chemical complexity of ambient air in the valley. Of the 71 species, 37 were found to have campaign average concentrations greater than 200 ppt and were identified based on their spectral characteristics, ambient diel profiles and correlation with specific emission tracers as a result of the high mass resolution (m ∕ Δm &thinsp;&gt;&thinsp; 4200) and temporal resolution (1 min) of the PTR-TOF-MS. The concentration ranking in the average VOC mixing ratios during our wintertime deployment was acetaldehyde (8.8 ppb) &thinsp;&gt;&thinsp; methanol (7.4 ppb) &thinsp;&gt;&thinsp; acetone + propanal (4.2 ppb) &thinsp;&gt;&thinsp; benzene (2.7 ppb) &thinsp;&gt;&thinsp; toluene (1.5 ppb) &thinsp;&gt;&thinsp; isoprene (1.1 ppb) &thinsp;&gt;&thinsp; acetonitrile (1.1 ppb) &thinsp;&gt;&thinsp; C8-aromatics (&thinsp;&sim;&thinsp;1 ppb) &thinsp;&gt;&thinsp; furan (&thinsp;&sim;&thinsp;0.5 ppb) &thinsp;&gt;&thinsp; C9-aromatics (0.4 ppb). Distinct diel profiles were observed for the nominal isobaric compounds isoprene (m ∕ z &thinsp;=&thinsp; 69.070) and furan (m ∕ z &thinsp;=&thinsp; 69.033). Comparison with wintertime measurements from several locations elsewhere in the world showed mixing ratios of acetaldehyde (&thinsp;&sim;&thinsp; 9 ppb), acetonitrile (&thinsp;&sim;&thinsp; 1 ppb) and isoprene (&thinsp;&sim;&thinsp; 1 ppb) to be among the highest reported to date. Two &quot;new&quot; ambient compounds, namely formamide (m ∕ z &thinsp;=&thinsp; 46.029) and acetamide (m ∕ z &thinsp;=&thinsp; 60.051), which can photochemically produce isocyanic acid in the atmosphere, are reported in this study along with nitromethane (a tracer for diesel exhaust), which has only recently been detected in ambient studies. Two distinct periods were selected during the campaign for detailed analysis: the first was associated with high wintertime emissions of biogenic isoprene and the second with elevated levels of ambient acetonitrile, benzene and isocyanic acid from biomass burning activities. Emissions from biomass burning and biomass co-fired brick kilns were found to be the dominant sources for compounds such as propyne, propene, benzene and propanenitrile, which correlated strongly with acetonitrile (r2&thinsp;&gt;&thinsp;0.7), a chemical tracer for biomass burning. The calculated total VOC OH reactivity was dominated by acetaldehyde (24.0 %), isoprene (20.2 %) and propene (18.7 %), while oxygenated VOCs and isoprene collectively contributed to more than 68 % of the total ozone production potential. Based on known secondary organic aerosol (SOA) yields and measured ambient concentrations in the Kathmandu Valley, the relative SOA production potential of VOCs were benzene &thinsp;&gt;&thinsp; naphthalene &thinsp;&gt;&thinsp; toluene &thinsp;&gt;&thinsp; xylenes &thinsp;&gt;&thinsp; monoterpenes &thinsp;&gt;&thinsp; trimethylbenzenes &thinsp;&gt;&thinsp; styrene &thinsp;&gt;&thinsp; isoprene. The first ambient measurements from any site in South Asia of compounds with significant health effects such as isocyanic acid, formamide, acetamide, naphthalene and nitromethane have been reported in this study. Our results suggest that mitigation of intense wintertime biomass burning activities, in particular point sources such biomass co-fired brick kilns, would be important to reduce the emission and formation of toxic VOCs (such as benzene and isocyanic acid) in the Kathmandu Valley.</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>
[1794] 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 C6–C8 aromatic compounds in the United States: Constraints from tall tower and aircraft measurements", Journal of Geophysical Research: Atmospheres, vol. 120, pp. 826–842, 2015.
Link: http://onlinelibrary.wiley.com/doi/10.1002/2014JD022627/abstract
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>
[1666] Yamada, H., S. Inomata, and H. Tanimoto, "Evaporative emissions in three-day diurnal breathing loss tests on passenger cars for the Japanese market", Atmospheric Environment, vol. 107, pp. 166–173, Apr, 2015.
Link: http://dx.doi.org/10.1016/j.atmosenv.2015.02.032
Abstract
<p>Breakthrough emissions that dominate diurnal evaporative emissions from gasoline vehicles were observed in continuous 3-day diurnal breathing loss (DBL) tests. These measurements were conducted on nine vehicles for the Japanese market. Two of these vehicles, made by US and European manufacturers, also meet regulations in their countries of origin. Four vehicles exhibited marked emissions caused by breakthrough emissions during the experimental period, all made by Japanese manufacturers. Using our experimental results, we estimate the total diurnal evaporative emissions from gasoline vehicles in Japan to be 32,792 t y&minus;1. The compositions of the breakthrough and permeation emissions were analyzed in real time using proton transfer reaction plus switchable reagent ion mass spectrometry to estimate the ozone formation potential for the evaporative emissions. The real-time measurements showed that the adsorption of hydrocarbons in a sealed housing evaporative determination unit can result in underestimation, when concentrations are only monitored before and after a DBL test. The composition analysis gave an estimated maximum incremental reactivity (MIR) 20% higher for the breakthrough emissions than for the gasoline that was tested, while the MIR for the permeation emissions was almost the same as the MIR for the fuel. Evaporative emissions from gasoline vehicles in Japan were found to contribute 4.2% to emissions from stationary sources using a mass-based estimate, or 6.1% of emissions from stationary sources using a MIR-based estimate.</p>
[1678] Colard, S., G. O'Connell, P. Sulzer, K. Breiev, X. Cahours, and S. S. Biel, "An Experimental Method to Determine the Concentration of Nicotine in Exhaled Breath and its Retention Rate Following Use of an Electronic Cigarette", J Environ Anal Chem, vol. 02, 2015.
Link: http://dx.doi.org/10.4172/2380-2391.1000161
Abstract
<p>An experimental method is presented for the first time to determine the concentration of nicotine in exhaled breath following e-cigarette use in experienced participants and the impact that vaping topography has on the retention rate of nicotine. Aerosols from e-cigarettes containing different concentrations of nicotine were first evaluated by GC-FID to determine the concentration of nicotine delivered per puff versus machine - vaping intensity. These e-cigarettes were then vaped by participants through a cigarette holder attached to a smoking topography analyzer which recorded puff volume and puff duration. This allowed the concentration of nicotine in the aerosol inhaled by the participant during each puff to be determined. A PTR-MS instrument was then used to determine the concentration of nicotine exhaled following each use of the e-cigarette. By dividing this figure by the nicotine concentration delivered enabled its retention rate to be calculated. The principal finding was over 99% of the nicotine was retained by the participants when the e-cigarette aerosol was inhaled and a reduced but still substantial quantity was retained (on average 86%) when the e-cigarette aerosol was held in the mouth only (i.e, no inhalation). In both cases, the nicotine concentrations detected in the exhaled breath were low (range 1.8 - 1786 ppb). The experimental method presented here may be used to determine the concentration of other e-cigarette aerosol constituents in exhaled breath and the retention rate of those constituents which is useful for the evaluation of e-cigarettes from a consumer and bystander perspective.</p>
[1627] Sahu, L.K.., and P. Saxena, "High time and mass resolved PTR-TOF-MS measurements of VOCs at an urban site of India during winter: Role of anthropogenic, biomass burning, biogenic and photochemical sources", Atmospheric Research, vol. 164-165, pp. 84–94, Oct, 2015.
Link: http://dx.doi.org/10.1016/j.atmosres.2015.04.021
Abstract
<p>This study is based on the high mass and time-resolved measurements of seven VOCs using a PTR-TOF-MS instrument at an urban site of India during winter 2013. Daily levels of OVOCs and aromatics were in the ranges of 3.5&ndash;37 ppbv and 0.85&ndash;23 ppbv, respectively with OVOCs accounted for up to 80% of total measured VOCs. The impact of long-range transport from the polluted Indo-Gangetic Plain and clean Thar desert was observed during the episodes of high and low VOCs, respectively. VOCs exhibited strong diurnal variations with peaks during morning and evening hours and lowest in the afternoon. Relatively elevated aromatics during evening hours coincided with the lowest-OVOCs indicating influence of fresh vehicular emissions. Emission ratios of isoprene and OVOCs with respect to benzene followed the diurnal cycles of temperature and solar flux indicating role of biogenic and photochemical processes, respectively. Correlation study of VOCs with benzene suggests major contribution from anthropogenic and also from biogenic and secondary sources to some extent. The higher emission ratios of ∆methanol/∆acetonitrile correspond to the episodes of long-range transport from biomass burning sources located in the Indo-Gangetic Plain (IGP). In addition to the pattern of emission, the diurnal and day-to-day variations of VOCs were influenced by the local meteorological conditions and depth of planetary boundary layer (PBL).</p>
[1710] Gamero-Negrón, R., J. {Sánchez Del Pulgar}, L. Cappellin, C. García, F. Gasperi, and F. Biasioli, "Immune-spaying as an alternative to surgical spaying in Iberian × Duroc females: Effect on the VOC profile of dry-cured shoulders and dry-cured loins as detected by PTR-ToF-MS.", Meat Sci, vol. 110, pp. 169–173, Dec, 2015.
Link: http://dx.doi.org/10.1016/j.meatsci.2015.07.018
Abstract
<p>Immunocastration in pigs has been proposed as a cruelty-free alternative to surgical castration. In this work the effect of immune-spaying of female pigs on the volatile compound profile of Iberian dry-cured products was evaluated. The head-space volatile compound of dry-cured shoulders and loins from surgically spayed, immune-spayed and entire Iberian &times; Duroc females was characterized by proton transfer reaction-time of flight-mass spectrometry. It was not possible to identify a significant effect of the castration modality on dry-cured shoulders, probably because of the heterogeneity of samples. Contrarily, Principal Component Analysis of dry-cured loins indicates a better homogeneity of samples and the separation of loins from surgically spayed and immune-spayed females. Some mass peaks tentatively identified as important flavor compounds in dry-cured products, 3-methylbutanal, 2,3-butanedione and 3-methylbutanoic acid, were significantly higher in the immune-spayed females. Therefore, immune-spaying seems to have a negligible effect on the volatile compound profile of dry-cured shoulders, whereas it could affect the VOC profile in the case of dry-cured loins.</p>
[1715] Sukul, P., P. Trefz, S. Kamysek, J. K. Schubert, and W. Miekisch, "Instant effects of changing body positions on compositions of exhaled breath.", J Breath Res, vol. 9, pp. 047105, Dec, 2015.
Link: http://dx.doi.org/10.1088/1752-7155/9/4/047105
Abstract
<p>Concentrations of exhaled volatile organic compounds (VOCs) may depend not only on biochemical or pathologic processes but also on physiological parameters. As breath sampling may be done in different body positions, effects of the sampling position on exhaled VOC concentrations were investigated by means of real-time mass spectrometry. Breaths from 15 healthy volunteers were analyzed in real-time by PTR-ToF-MS-8000 during paced breathing (12/min) in a continuous side-stream mode. We applied two series of body positions (setup 1: sitting, standing, supine, and sitting; setup 2: supine, left lateral, right lateral, prone, and supine). Each position was held for 2&thinsp;min. Breath VOCs were quantified in inspired and alveolar air by means of a custom-made algorithm. Parallel monitoring of hemodynamics and capnometry was performed noninvasively. In setup 1, when compared to the initial sitting position, normalized mean concentrations of isoprene, furan, and acetonitrile decreased by 24%, 26%, and 9%, respectively, during standing and increased by 63%, 36%, and 10% during lying mirroring time profiles of stroke volume and pET-CO2. In contrast, acetone and H2S concentrations remained almost constant. In setup 2, when compared to the initial supine position, mean alveolar concentrations of isoprene and furan increased significantly up to 29% and 16%, respectively, when position was changed from lying on the right side to the prone position. As cardiac output and stroke volume decreased at that time, the reasons for the observed concentrations changes have to be linked to the ventilation/perfusion ratio or compartmental distribution rather than to perfusion alone. During final postures, all VOC concentrations, hemodynamics, and pET-CO2 returned to baseline. Exhaled blood-borne VOC profiles changed due to body postures. Changes depended on cardiac stroke volume, origin, compartmental distribution and physico-chemical properties of the substances. Patients&#39; positions and cardiac output have to be controlled when concentrations of breath VOCs are to be interpreted in terms of biomarkers.</p>
[1625] Hu, L., D. B. Millet, M. Baasandorj, T. J. Griffis, P. Turner, D. Helmig, A. J. Curtis, and J. Hueber, "Isoprene emissions and impacts over an ecological transition region in the US Upper Midwest inferred from tall tower measurements", Journal of Geophysical Research: Atmospheres, Mar, 2015.
Link: http://dx.doi.org/10.1002/2014JD022732
Abstract
<p>We present one year of in-situ PTR-MS measurements of isoprene and its oxidation products MVK and MACR from a 244 m tall tower in the US Upper Midwest, located at an ecological transition between isoprene-emitting deciduous forest and predominantly non-isoprene-emitting agricultural landscapes. We find that anthropogenic interferences (or anthropogenic isoprene) contribute on average 20% of the PTR-MS m/z 69 signal during summer daytime, whereas MVK+MACR interferences (m/z 71) are minor (7%). After removing these interferences, the observed isoprene and MVK+MACR abundances show pronounced seasonal cycles, reaching summertime maxima of &gt;2500 pptv (1-hour mean). The tall tower is impacted both by nearby and more distant regional isoprene sources, with daytime enhancements of isoprene (but little MVK+MACR) under southwest winds, and enhancements of MVK+MACR (but little isoprene) at other times. We find that the GEOS-Chem atmospheric model with the MEGANv2.1 biogenic inventory can reproduce the isoprene observations to within model uncertainty given improved land cover and temperature estimates. However, a 60% low model bias in MVK+MACR cannot be resolved, even across diverse model assumptions for NOx emissions, chemistry, atmospheric mixing, dry deposition, land cover, and potential measurement interferences. This implies that, while isoprene emissions in the immediate vicinity of the tall tower are adequately captured, they are underestimated across the broader region. We show that this region experiences a strong seasonal shift between VOC-limited chemistry during the spring and fall and NOx-limited or transitional chemistry during the summer, driven by the spatiotemporal distribution of isoprene emissions. Isoprene&#39;s role in causing these chemical shifts is likely underestimated due to the underprediction of its regional emissions.</p>
[1623] Baasandorj, M.., D.. B. Millet, L.. Hu, D.. Mitroo, and B.. J. Williams, "Measuring acetic and formic acid by proton-transfer-reaction mass spectrometry: sensitivity, humidity dependence, and quantifying interferences", Atmos. Meas. Tech., vol. 8, pp. 1303–1321, 2015.
Link: http://dx.doi.org/10.5194/amt-8-1303-2015
Abstract
We present a detailed investigation of the factors governing the quantification of formic acid (FA), acetic acid (AA), and their relevant mass analogues by proton-transfer-reaction mass spectrometry (PTR-MS), assess the underlying fragmentation pathways and humidity dependencies, and present a new method for separating FA and AA from their main isobaric interferences. PTR-MS sensitivities towards glycolaldehyde, ethyl acetate, and peroxyacetic acid at m/z 61 are comparable to that for AA; when present, these species will interfere with ambient AA measurements by PTR-MS. Likewise, when it is present, dimethyl ether can interfere with FA measurements. For a reduced electric field (E/N) of 125 Townsend (Td), the PTR-MS sensitivity towards ethanol at m/z 47 is 5–20 times lower than for FA; ethanol will then only be an important interference when present in much higher abundance than FA. Sensitivity towards 2-propanol is <1% of that for AA, so that propanols will not in general represent a significant interference for AA. Hydrated product ions of AA, glycolaldehyde, and propanols occur at m/z 79, which is also commonly used to measure benzene. However, the resulting interference for benzene is only significant when E/N is low (<= 100 Td). Addition of water vapor affects the PTR-MS response to a given compound by (i) changing the yield for fragmentation reactions and (ii) increasing the importance of ligand switching reactions. In the case of AA, sensitivity to the molecular ion increases with humidity at low E/N but decreases with humidity at high E/N due to water-driven fragmentation. Sensitivity towards FA decreases with humidity throughout the full range of E/N. For glycolaldehyde and the alcohols, the sensitivity increases with humidity due to ligand switching reactions (at low E/N) and reduced fragmentation in the presence of water (at high E/N). Their role as interferences will typically be greatest at high humidity. For compounds such as AA where the humidity effect depends strongly on the collisional energy in the drift tube, simple humidity correction factors (XR) will only be relevant for a specific instrumental configuration. We recommend E/N   125 Td as an effective condition for AA and FA measurements by PTR-MS, as it optimizes between the competing E/N-dependent mechanisms controlling their sensitivities and those of the interfering species. Finally, we present the design and evaluation of an online acid trap for separating AA and FA from their interfering species at m/z 61 and 47, and we demonstrate its performance during a field deployment to St. Louis, USA, during August–September of 2013.

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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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