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Found 14 results
Title [ Year(Asc)]
Filters: Author is Dewulf, Jo  [Clear All Filters]
2013
[Simpraga2013] Šimpraga, M., H. Verbeeck, J. Bloemen, L. Vanhaecke, M. Demarcke, E. Joó, O. Pokorska, C. Amelynck, N. Schoon, J. Dewulf, et al., "Vertical canopy gradient in photosynthesis and monoterpenoid emissions: An insight into the chemistry and physiology behind", Atmospheric Environment: Elsevier, 2013.
Link: http://www.sciencedirect.com/science/article/pii/S1352231013005785
Abstract
It is well known that vertical canopy gradients and varying sky conditions influence photosynthesis (Pn), specific leaf area (SLA), leaf thickness (LT) and leaf pigments (lutein, â-carotene and chlorophyll). In contrast, little is known about these effects on monoterpenoid (MT) emissions. Our study examines simultaneously measured Pn, MT emissions and the MT/Pn ratio along the canopy of an adult European beech tree (Fagus sylvatica L.) in natural forest conditions. Dynamic branch enclosure systems were used at four heights in the canopy (7, 14, 21 and 25 m) in order to establish relationships and better understand the interaction between Pn and MT emissions under both sunny and cloudy sky conditions. Clear differences in Pn, MT emissions and the MT/Pn ratio were detected within the canopy. The highest Pn rates were observed in the sun leaves at 25 m due to the higher intercepted light levels, whereas MT emissions (and the MT/Pn ratio) were unexpectedly highest in the semi-shaded leaves at 21 m. The higher Pn rates and, apparently contradictory, lower MT emissions in the sun leaves may be explained by the hypothesis of Owen and Peñuelas (2005), stating synthesis of more photo-protective carotenoids may decrease the emissions of volatile isoprenoids (including MTs) because they both share the same biochemical precursors. In addition, leaf traits like SLA, LT and leaf pigments clearly differed with height in the canopy, suggesting that the leaf's physiological status cannot be neglected in future research on biogenic volatile organic compounds (BVOCs) when aiming at developing new and/or improved emission algorithms.
2011
[Simpraga2011] Šimpraga, M., H. Verbeeck, M. Demarcke, É. Joó, O. Pokorska, C. Amelynck, N. Schoon, J. Dewulf, H. Van Langenhove, B. Heinesch, et al., "Clear link between drought stress, photosynthesis and biogenic volatile organic compounds in Fagus sylvatica L.", Atmospheric Environment, vol. 45, no. 30: Elsevier, pp. 5254–5259, 2011.
Link: http://www.sciencedirect.com/science/article/pii/S1352231011006996
Abstract
Direct plant stress sensing is the key for a quantitative understanding of drought stress effects on biogenic volatile organic compound (BVOC) emissions. A given level of drought stress might have a fundamentally different effect on the BVOC emissions of different plants. For the first time, we continuously quantified the level of drought stress in a young potted beech (Fagus sylvatica L.) with a linear variable displacement transducer (LVDT) installed at stem level in combination with simultaneous measurements of BVOC emissions and photosynthesis rates at leaf level. This continuous set of measurements allowed us to examine how beech alters its pattern of photosynthesis and carbon allocation to BVOC emissions (mainly monoterpenes, MTs) and radial stem growth during the development of drought stress. We observed an increasing-decreasing trend in the MT emissions as well as in the fraction of assimilated carbon re-emitted back into the atmosphere (ranging between 0.14 and 0.01%). We were able to link these dynamics to pronounced changes in radial stem growth, which served as a direct plant stress indicator. Interestingly, we detected a sudden burst in emission of a non-identified, non-MT BVOC species when drought stress was acute (i.e. pronounced negative stem growth). This burst might have been caused by a certain stress-related green leaf volatile, which disappeared immediately upon re-watering and thus the alleviation of drought stress. These results highlight that direct plant stress sensing creates opportunities to understand the overall complexity of stress-related BVOC emissions.
[Simpraga2011a] Šimpraga, M., H. Verbeeck, M. Demarcke, É. Joó, C. Amelynck, N. Schoon, J. Dewulf, H. Van Langenhove, B. Heinesch, M. Aubinet, et al., "Comparing monoterpenoid emissions and net photosynthesis of beech ( Fagus sylvatica L.) in controlled and natural conditions", Atmospheric Environment, vol. 45, no. 17: Elsevier, pp. 2922–2928, 2011.
Link: http://www.sciencedirect.com/science/article/pii/S1352231011000884
Abstract
<p>Although biogenic volatile organic compounds (BVOCs) only represent a very limited fraction of the plant&rsquo;s carbon (C) budget, they play an important role in atmospheric chemistry for example as a precursor of tropospheric ozone. We performed a study comparing BVOC emissions of European beech (Fagus sylvatica L.) in controlled and natural environmental conditions. A young and adult beech tree was exposed to short-term temperature variations in growth room conditions and in an experimental forest, respectively. This study attempts to clarify how short-term temperature variations between days influenced the ratio between monoterpenoid (MT) emissions and net photosynthesis (Pn). Within a temperature range of 17&ndash;27 &deg;C and 13&ndash;23 &deg;C, the MT/Pn carbon ratio increased 10&ndash;30 fold for the growth room and forest, respectively. An exponential increasing trend between MT/Pn C ratio and air temperature was observed in both conditions. Beech trees re-emitted a low fraction of the assimilated C back into the atmosphere as MT: 0.01&ndash;0.12% and 0.01&ndash;0.30% with a temperature rise from 17 to 27 &deg;C and 13&ndash;23 &deg;C in growth room and forest conditions, respectively. However, the data showed that the MT/Pn C ratio of young and adult beech trees responded significantly to changes in temperature.</p>
[Joo2011] Joó, É., J. Dewulf, C. Amelynck, N. Schoon, O. Pokorska, M. Šimpraga, K. Steppe, M. Aubinet, and H. Van Langenhove, "Constitutive versus heat and biotic stress induced BVOC emissions in Pseudotsuga menziesii", Atmospheric Environment, vol. 45, no. 22: Elsevier, pp. 3655–3662, 2011.
Link: http://www.sciencedirect.com/science/article/pii/S1352231011004377
Abstract
Induced volatiles have been a focus of recent research, as not much is known of their emission behavior or atmospheric contribution. BVOC emissions were measured from Pseudotsuga menziesii saplings under natural environmental conditions, using a dynamic branch enclosure system and GC–MS for their analysis. We determined temperature and light dependency of the individual compounds, studied seasonality of the emissions and discuss the effect of heat stress in comparison with two specific biotic stresses that occurred naturally on the trees. A standardized emission rate of 6.8 μg g(dw)−1 h−1 for monoterpenes under stressed conditions was almost a magnitude higher than that obtained for healthy trees (0.8 ± 0.2 μg g(dw)−1 h−1), with higher beta factors characterizing the stressed trees. The response of the emissions to light intensity was different for the individual compounds, suggesting a distinct minimum light intensity to reach saturation. Heat stress changed the relative contribution of specific volatiles, with larger extent of increase of sesquiterpenes, methyl salicylate and linalool emissions compared to monoterpenes. Biotic stress kept low the emissions of sesquiterpenes, (E)-4,8-dimethyl-1,3,7-nonatriene and methylbutenol isomers, and increased the level of methyl salicylate and monoterpenes. The ratio of β-pinene/α-pinene was also found to be significantly enhanced from 1.3 to 2.4 and 3.2 for non-stressed, heat stressed and combined biotic and heat stressed, respectively.
[Biasioli2011] Biasioli, F., C. Yeretzian, T. D. Märk, J. Dewulf, and H. Van Langenhove, "Direct-injection mass spectrometry adds the time dimension to (B) VOC analysis", TrAC Trends in Analytical Chemistry, vol. 30, no. 7: Elsevier, pp. 1003–1017, 2011.
Link: http://www.sciencedirect.com/science/article/pii/S0165993611001269
Abstract
In the past decade, we have witnessed rapid development of direct-injection mass spectrometric (DIMS) technologies that combine ever-improving mass and time resolution with high sensitivity and robustness. Here, we review some of the most significant DIMS technologies, which have been applied to rapid monitoring and quantification of volatile organic compounds (VOCs) and biogenic VOCS (BVOCs). They include MS-e-noses, atmospheric-pressure chemical ionization (APCI), proton-transfer-reaction mass spectrometry (PTR-MS), and selected ion-flow-tube mass spectrometry (SIFT-MS). DIMS-based MS-e-noses provide the possibility to screen large sample sets and may yield rich analytical information. APCI is a widespread ionization method and pioneered DIMS in environmental and flavor-release applications. SIFT-MS and PTR-MS allow better control of precursor-ion generation and hence of the ionization process. SIFT-MS puts the focus on control of the ionization process, while PTR-MS does so on sensitivity. Most (B)VOCs of interest can be efficiently detected and often identified by DIMS, thanks also to the possibility of switching between different precursor ions and the recent realization of time-of-flight-based equipments. Finally, we give selected examples of applications for each of the key technologies, including research in food-quality control (MS-e-nose), flavor release (APCI), environmental sciences (PTR-MS) and health sciences (SIFT-MS).
[Laffineur2011a] Laffineur, Q., M. Aubinet, N. Schoon, C. Amelynck, J-F. Müller, J. Dewulf, H. Van Langenhove, K. Steppe, M. Šimpraga, and B. Heinesch, "Isoprene and monoterpene emissions from a mixed temperate forest", Atmospheric Environment, vol. 45, no. 18: Elsevier, pp. 3157–3168, 2011.
Link: http://www.sciencedirect.com/science/article/pii/S1352231011001981
Abstract
<p>We measured the isoprene and monoterpene fluxes continuously above a mixed forest site at Vielsalm in the eastern part of Belgium, using the disjunct eddy covariance technique with proton transfer reaction-mass spectrometry. Simultaneously, we also measured the carbon dioxide fluxes in order to deduce the gross primary production. The measurements were conducted from July to September 2009. During the day, the seasonal evolution of the isoprene/monoterpene emissions was studied using a monthly temperature and light dependence function deduced from our results to standardize the fluxes. A seasonal decrease in the standard emission factors was observed, probably linked to acclimation or senescence. The standard emission factor for isoprene fluxes (30 &deg;C, 1000 μmol m&minus;2 s&minus;1) fell from 0.91 &plusmn; 0.01 to 0.56 &plusmn; 0.02 μg m&minus;2 s&minus;1 and for monoterpene fluxes from 0.74 &plusmn; 0.03 to 0.27 &plusmn; 0.03 μg m&minus;2 s&minus;1. During the night, a slight positive flux of monoterpenes was observed that seemed to be driven by air temperature. The standard emission factor (30&deg;C) for nighttime monoterpene fluxes was equal to 0.093 &plusmn; 0.019 μg m&minus;2 s&minus;1. Finally, we studied the seasonal evolution of the relationship between the gross primary production and the isoprene/monoterpenes fluxes. A linear relationship was observed, highlighting the strong link between carbon assimilation and isoprene/monoterpene emissions.</p>
2010
[Demarcke2010] Demarcke, M., J-F. Müller, N. Schoon, H. Van Langenhove, J. Dewulf, E. Joó, K. Steppe, M. Šimpraga, B. Heinesch, M. Aubinet, et al., "History effect of light and temperature on monoterpenoid emissions from Fagus sylvatica L.", Atmospheric Environment, vol. 44, no. 27: Elsevier, pp. 3261–3268, 2010.
Link: http://www.sciencedirect.com/science/article/pii/S1352231010004462
Abstract
Monoterpenoid emissions from Fagus sylvatica L. trees have been measured at light- and temperature-controlled conditions in a growth chamber, using Proton Transfer Reaction Mass Spectrometry (PTR-MS) and the dynamic branch enclosure technique. De novo synthesized monoterpenoid Standard Emission Factors, obtained by applying the G97 algorithm (Guenther, 1997), varied between 2 and 32 μg gDW−1 h−1 and showed a strong decline in late August and September, probably due to senescence. The response of monoterpenoid emissions to temperature variations at a constant daily light pattern could be well reproduced with a modified version of the MEGAN algorithm (Guenther et al., 2006), with a typical dependence on the average temperature over the past five days. The diurnal emissions at constant temperature showed a typical hysteretic behaviour, which could also be adequately described with the modified MEGAN algorithm by taking into account a dependence on the average light levels experienced by the trees during the past 10–13 h. The impact of the past light and temperature conditions on the monoterpenoid emissions from F. sylvatica L. was found to be much stronger than assumed in previous algorithms. Since our experiments were conducted under low light intensity, future studies should aim at confirming and completing the proposed algorithm updates in sunny conditions and natural environments.
[Demarcke2010a] Demarcke, M., C. Amelynck, N. Schoon, F. Dhooghe, J. Rimetz-Planchon, H. Van Langenhove, and J. Dewulf, "Laboratory studies in support of the detection of biogenic unsaturated alcohols by proton transfer reaction-mass spectrometry", International Journal of Mass Spectrometry, vol. 290, no. 1: Elsevier, pp. 14–21, 2010.
Link: http://www.sciencedirect.com/science/article/pii/S1387380609003558
Abstract
The effect of the ratio of the electric field to the buffer gas number density (E/N) in the drift tube reactor of a proton transfer reaction-mass spectrometer (PTR-MS) on the product ion distributions of seven common biogenic unsaturated alcohols (2-methyl-3-buten-2-ol, 1-penten-3-ol, cis-3-hexen-1-ol, trans-2-hexen-1-ol, 1-octen-3-ol, 6-methyl-5-hepten-2-ol and linalool) has been investigated. At low E/N values, the dominant product ion is the dehydrated protonated alcohol. Increasing E/N results in more extensive fragmentation for all compounds. For cis-3-hexenol and 6-methyl-5-hepten-2-ol the contribution of the protonated molecule can be enhanced by reducing E/N with respect to commonly used PTR-MS E/N values (120–130 Td). Significant differences have been found between some of the isomeric species studied, opening a way for selective detection. The C10 alcohol linalool mainly results in product ions at m/z 137 and 81, which are also PTR-MS fingerprints of monoterpenes. This may complicate monoterpene quantification when linalool and monoterpenes are simultaneously present in sampled air. Furthermore the influence of the water vapour pressure in the PTR-MS inlet line on the product ion distributions has been determined. Some major fingerprint ions of the unsaturated alcohols were found to depend significantly on the water vapour pressure in the inlet line and this should be taken into account for accurate quantification of these species by PTR-MS.
[Joo2010a] Joó, É., J. Dewulf, M. Demarcke, C. Amelynck, N. Schoon, J-F. Müller, M. Šimpraga, K. Steppe, and H. Van Langenhove, "Quantification of interferences in PTR-MS measurements of monoterpene emissions from Fagus sylvatica L. using simultaneous TD-GC-MS measurements", International Journal of Mass Spectrometry, vol. 291, no. 1: Elsevier, pp. 90–95, 2010.
Link: http://www.sciencedirect.com/science/article/pii/S1387380610000357
Abstract
The interest in quantitative analysis of biogenic volatile organic compounds (BVOCs) emissions stems from their importance in atmospheric chemistry. In order to compare the most frequently used BVOC measurement techniques, simultaneous on-line PTR-MS and off-line GC-MS data collection was performed on a 3 years old Fagus sylvatica L. tree placed in a growth chamber. Using an internal standard (deuterated toluene) and applying the selective ion mode (SIM) resulted in significant improvements of monoterpene (MT) quantification by TD-GC-MS. PTR-MS quantification of MTs was based on the ion signal at m/z 137. In the course of the experiments the relative contribution of linalool compared to that of MTs was found to be up to 84%. Since this compound has also a PTR-MS signature at m/z 137, quantification of MT emission rates by PTR-MS was disturbed. Comparison of GC-MS and PTR-MS data allowed an estimation of the ratio of the PTR-MS sensitivity for linalool to the one for MTs at m/z 137. This ratio of sensitivities, combined with the information of the relative contribution of linalool to the sum of linalool and MTs obtained by GC-MS, resulted in accurate derivation of the sum of emission rates of linalool and MTs by PTR-MS. The results indicate that fast and on-line PTR-MS measurements of BVOCs are best accompanied by off-line GC measurements to detect possible interferences or to use the additional information for properly quantifying the sum of emission rates of several compounds.
[Joo2010] Joó, É., H. Van Langenhove, M. Šimpraga, K. Steppe, C. Amelynck, N. Schoon, J-F. Müller, and J. Dewulf, "Variation in biogenic volatile organic compound emission pattern of Fagus sylvatica L. due to aphid infection", Atmospheric Environment, vol. 44, no. 2: Elsevier, pp. 227–234, 2010.
Link: http://www.sciencedirect.com/science/article/pii/S1352231009008553
Abstract
Volatile organic compounds (VOCs) have been the focus of interest to understand atmospheric processes and their consequences in formation of ozone or aerosol particles; therefore, VOCs contribute to climate change. In this study, biogenic VOCs (BVOCs) emitted from Fagus sylvatica L. trees were measured in a dynamic enclosure system. In total 18 compounds were identified: 11 monoterpenes (MT), an oxygenated MT, a homoterpene (C14H18), 3 sesquiterpenes (SQT), isoprene and methyl salicylate. The frequency distribution of the compounds was tested to determine a relation with the presence of the aphid Phyllaphis fagi L. It was found that linalool, (E)-β-ocimene, α-farnesene and a homoterpene identified as (E)-4,8-dimethyl-1,3,7-nonatriene (DMNT), were present in significantly more samples when infection was present on the trees. The observed emission spectrum from F. sylvatica L. shifted from MT to linalool, α-farnesene, (E)-β-ocimene and DMNT due to the aphid infection. Sabinene was quantitatively the most prevalent compound in both, non-infected and infected samples. In the presence of aphids α-farnesene and linalool became the second and third most important BVOC emitted. According to our investigation, the emission fingerprint is expected to be more complex than commonly presumed.
2009
[Steppe2009] Steppe, K., R. Lemeur-UGent, J. Dewulf, H. Van Langenhove-UGent, C. Amelynck, N. Schoon, J-F. Müller-BISA, M. Aubinet-FUSAG, J. Dewulf, E. Joó, et al., "IMPACT OF PHENOLOGY AND ENVIRONMENTAL CONDITIONS ON BVOC EMISSIONS FROM FOREST ECOSYSTEMS IMPECVOC", Science for Sustainable Development (SSD), 2009.
Link: http://www.belspo.be/belspo/ssd/science/Reports/FinalReport_IMPECVOC_phase1.ML.pdf
[Demarcke2009] Demarcke, M., C. Amelynck, N. Schoon, F. Dhooghe, H. Van Langenhove, and J. Dewulf, "Laboratory studies in support of the detection of sesquiterpenes by proton-transfer-reaction-mass-spectrometry", International Journal of Mass Spectrometry, vol. 279, no. 2: Elsevier, pp. 156–162, 2009.
Link: http://www.sciencedirect.com/science/article/pii/S1387380608004351
Abstract
The effects of the ratio of the electric field strength to the buffer gas number density (E/N) in the drift tube of a proton transfer reaction mass spectrometer on the product ion distributions of the sesquiterpenes β-caryophyllene, α-humulene, α-cedrene and longifolene have been investigated.Chemical ionization of the sesquiterpenes resulted in important fragmentation of the nascent excited ion/molecule complex at the highest E/N values. The most important fragment ions were common to all sesquiterpenes and therefore cannot be used as fingerprints for specific isomers. The yield of the protonated molecule increased on average by a factor 1.6 by decreasing E/N from 140 to 80 Td. Taking into account the influence of E/N on the reaction time and on the reactant ion mobility, it is estimated that this decrease in E/N may lead to an overall increase in the PTR-MS detection sensitivity of sesquiterpenes (based on the ion signal at m/z 205) by a factor 3.5.Product ion distributions of α-cedrene and longifolene have also been determined at different water vapour pressures. No substantial influence of the water vapour pressure on the product ion yields was observed, which is an advantage when quantifying sesquiterpenes by PTR-MS in samples of varying relative humidity.
2008
[Demarcke2008] Demarcke, M., C. Amelynck, N. Schoon, JF. Muller, É. Joó, J. Dewulf, H. Van Langenhove, M. Simpraga, K. Steppe, R. Samson, et al., "Measurements of BVOC emissions from Fagus sylvatica L. in controlled environmental conditions: preliminary results", European Geophysical Union Conference, 2008.
Link: http://meetings.copernicus.org/www.cosis.net/abstracts/EGU2008/02589/EGU2008-A-02589-1.pdf
[Simpraga2008] Simpraga, M., K. Steppe, M. Demarcke, C. Amelynck, N. Schoon, É. Joó, J. Dewulf, H. Van Langenhove, R. Samson, JF. Muller, et al., "Preliminary observations of temperature effects on carbon losses throught BVOC emissions in Fagus sylVatica L.", European Geophysical Union Conference, vol. 10, 2008.
Link: https://biblio.ugent.be/publication/1208460/file/1209475.pdf

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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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