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Found 775 results
Title [ Year(Desc)]
2006
[1499] Varutbangkul, V.., F.. J. Brechtel, R.. Bahreini, N.. L. Ng, M.. D. Keywood, J.. H. Kroll, R.. C. Flagan, J.. H. Seinfeld, A.. Lee, and A.. H. Goldstein, "Hygroscopicity of secondary organic aerosols formed by oxidation of cycloalkenes, monoterpenes, sesquiterpenes, and related compounds", Atmospheric Chemistry and Physics, vol. 6, pp. 2367–2388, Jun, 2006.
Link: http://nature.berkeley.edu/ahg/pubs/Hygroscopicity.pdf
Abstract
<p>A series of experiments has been conducted in the Caltech indoor smog chamber facility to investigate the water uptake properties of aerosol formed by oxidation of various organic precursors. Secondary organic aerosol (SOA) from simple and substituted cycloalkenes (C5-C8) is produced in dark ozonolysis experiments in a dry chamber (RH&nbsp;5%). Biogenic SOA from monoterpenes, sesquiterpenes, and oxygenated terpenes is formed by photooxidation in a humid chamber (&nbsp;50% RH). Using the hygroscopicity tandem differential mobility analyzer (HTDMA), we measure the diameter-based hygroscopic growth factor (GF) of the SOA as a function of time and relative humidity. All SOA studied is found to be slightly hygroscopic, with smaller water uptake than that of typical inorganic aerosol substances. The aerosol water uptake increases with time early in the experiments for the cycloalkene SOA, but decreases with time for the sesquiterpene SOA. This behavior could indicate competing effects between the formation of more highly oxidized polar compounds (more hygroscopic), and formation of longer-chained oligomers (less hygroscopic). All SOA also exhibit a smooth water uptake with RH with no deliquescence or efflorescence. The water uptake curves are found to be fitted well with an empirical three-parameter functional form. The measured pure organic GF values at 85% RH are between 1.09&ndash;1.16 for SOA from ozonolysis of cycloalkenes, 1.01&ndash;1.04 for sesquiterpene photooxidation SOA, and 1.06&ndash;1.10 for the monoterpene and oxygenated terpene SOA. The GF of pure SOA (GForg) in experiments in which inorganic seed aerosol is used is determined by assuming volume-weighted water uptake (Zdanovskii-Stokes-Robinson or &quot;ZSR&quot; approach) and using the size-resolved organic mass fraction measured by the Aerodyne Aerosol Mass Spectrometer. Knowing the water content associated with the inorganic fraction yields GForg values. However, for each precursor, the GForg values computed from different HTDMA-classified diameters agree with each other to varying degrees. Comparing growth factors from different precursors, we find that GForg is inversely proportional to the precursor molecular weight and SOA yield, which is likely a result of the fact that higher-molecular weight precursors tend to produce larger and less hygroscopic oxidation products.</p>
[Clementschitsch2006] Clementschitsch, F., and K. Bayer, "Improvement of bioprocess monitoring: development of novel concepts", Microbial Cell Factories, vol. 5, no. 19, pp. -, 2006.
Link: http://www.microbialcellfactories.com/content/5/1/19
Abstract
The advancement of bioprocess monitoring will play a crucial role to meet the future requirements of bioprocess technology. Major issues are the acceleration of process development to reduce the time to the market and to ensure optimal exploitation of the cell factory and further to cope with the requirements of the Process Analytical Technology initiative. Due to the enormous complexity of cellular systems and lack of appropriate sensor systems microbial production processes are still poorly understood. This holds generally true for the most microbial production processes, in particular for the recombinant protein production due to strong interaction between recombinant gene expression and host cell metabolism. Therefore, it is necessary to scrutinise the role of the different cellular compartments in the biosynthesis process in order to develop comprehensive process monitoring concepts by involving the most significant process variables and their interconnections. Although research for the development of novel sensor systems is progressing their applicability in bioprocessing is very limited with respect to on-line and in-situ measurement due to specific requirements of aseptic conditions, high number of analytes, drift, and often rather low physiological relevance. A comprehensive survey of the state of the art of bioprocess monitoring reveals that only a limited number of metabolic variables show a close correlation to the currently explored chemical/physical principles. In order to circumvent this unsatisfying situation mathematical methods are applied to uncover "hidden" information contained in the on-line data and thereby creating correlations to the multitude of highly specific biochemical off-line data. Modelling enables the continuous prediction of otherwise discrete off-line data whereby critical process states can be more easily detected. The challenging issue of this concept is to establish significant on-line and off-line data sets. In this context, online sensor systems are reviewed with respect to commercial availability in combination with the suitability of offline analytical measurement methods. In a case study, the aptitude of the concept to exploit easily available online data for prediction of complex process variables in a recombinant E. coli fed-batch cultivation aiming at the improvement of monitoring capabilities is demonstrated. In addition, the perspectives for model-based process supervision and process control are outlined.
[Aprea2006a] Aprea, E., F. Biasioli, F. Gasperi, T. D. Maerk, and S. van Ruth, "In vivo monitoring of strawberry flavour release from model custards: effect of texture and oral processing", Flavour and fragrance journal, vol. 21, no. 1: Wiley Online Library, pp. 53–58, 2006.
Link: http://onlinelibrary.wiley.com/doi/10.1002/ffj.1702/abstract
Abstract
The interaction of oral processing protocols and food texture on in vivo flavour release was evaluated by nose-space analysis. Nose-space analysis was carried out by proton transfer reaction mass spectrometry, and strawberry-flavoured custards were prepared with 0.1% (w/w) and 1.0% (w/w) carboxymethyl cellulose to modify the texture. Two oral processing protocols were adopted during the study; a free-chewing protocol and an imposed protocol. Twenty-one subjects participated in the study. Significant effects on in-nose flavour release were observed for the type of compound, the custard's texture, the oral processing protocol and the subjects. When people were allowed to eat as they normally do, individuals could be divided into three groups on the basis of swallowing time: first group, swallowing time <4 s; second group, swallowing time >6 s; intermediate group, t(swallow) varying (4–6 s). Within each group, different effects of the texture of the custards on in-nose flavour concentrations were observed, indicating that individual behaviour plays a considerable role in determining texture effects on flavour perception.
[Boland2006] Boland, A. B., C. M. Delahunty, and S. M. van Ruth, "Influence of the texture of gelatin gels and pectin gels on strawberry flavour release and perception", Food chemistry, vol. 96, no. 3: Elsevier, pp. 452–460, 2006.
Link: http://www.sciencedirect.com/science/article/pii/S0308814605001974
Abstract
The release of strawberry flavour compounds from pectin gels and gelatin gels was evaluated by instrumental and sensory analysis. Three gel textures were established based on Young’s modulus of elasticity (E) for each gel. The E of the low, medium and high rigidity gelatine and pectin gels was 181, 300 and 493 N m−2, respectively. Air/gel partition coefficients were determined by static headspace analysis. In-nose/proton transfer reaction-mass spectrometry analysis produced temporal release profiles. Sensory analysis was conducted to assess perceived odour, thickness, strawberry flavour and sweetness using magnitude estimation. The type of hydrocolloid affected static and in-nose compound concentrations significantly. The pectin gels showed lower air/gel partition coefficients than the gelatin gels, but increased flavour release. Increased gel rigidity resulted in lower air/gel partition coefficients; higher maximum concentrations of volatiles and lower release rates during in-nose analysis; decreased perception of odour, strawberry flavour and sweetness; and higher intensity ratings for thickness in sensory analysis. Consequently, both type of hydrocolloid and rigidity of the sample greatly affected flavour release and perception.
[Presto2006] Presto, A. A., and N. M. Donahue, "Investigation of alpha-pinene + ozone secondary organic aerosol formation at low total aerosol mass.", Environ Sci Technol, vol. 40, no. 11: Center for Atmospheric Particle Studies, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA., pp. 3536–3543, Jun, 2006.
Abstract
We present a method for measuring secondary organic aerosol (SOA) production at low total organic mass concentration (COA) using proton-transfer reaction mass spectrometry (PTR-MS). PTR-MS provides high time resolution measurements of gas-phase organic species and, coupled with particle measurements, allows for the determination of aerosol yield in real time. This approach facilitates the measurement of aerosol production at low COA; in fact aerosol mass fractions can be measured during alpha-pinene consumption as opposed to only at the completion of gas-phase chemistry. The high time resolution data are consistent with both the partitioning theory of Pankow (Atmos. Environ. 1994, 28,185 and 189) and the previous experimental measurements. Experiments including the effect of UV illumination and NOx reveal additional features of alpha-pinene + ozone product photochemistry and volatility. The high time resolution data also elucidate aerosol production from alpha-pinene ozonolysis at COA < 10 microg m(-3) and show that extrapolations of current partitioning models to conditions of low COA significantly underestimate SOA production under dark, low-NOx conditions. However, extrapolations of current models overestimate SOA production under illuminated, higher-NOx conditions typical of polluted regional air masses.
[Mayrhofer2006] Mayrhofer, S., T. Mikoviny, S. Waldhuber, A. O. Wagner, G. Innerebner, I. H. Franke-Whittle, T. D. Maerk, A. Hansel, and H. Insam, "Microbial community related to volatile organic compound (VOC) emission in household biowaste.", Environ Microbiol, vol. 8, no. 11: Institut fuer Mikrobiologie, Universitaet Innsbruck, Innsbruck, Austria. sabine.mayrhofer@uibk.ac.at, pp. 1960–1974, Nov, 2006.
Link: http://dx.doi.org/10.1111/j.1462-2920.2006.01076.x
Abstract
Malodorous emissions and potentially pathogenic microorganisms which develop during domestic organic waste collection are not only a nuisance but may also pose health risks. The aim of the present study was to determine whether the presence of specific microorganisms in biowastes is directly related to the composition of the emitted volatile organic compounds (VOCs). The succession of microbial communities during 16 days of storage in organic waste collection bins was studied by denaturing gradient gel electrophoresis (DGGE) of amplified 16S ribosomal DNA in parallel with a classical cultivation and isolation approach. Approximately 60 different bacterial species and 20 different fungal species were isolated. Additionally, some bacterial species were identified through sequencing of excised DGGE bands. Proton transfer reaction mass spectrometry (PTR-MS) was used to detect VOCs over the sampling periods, and co-inertia analyses of VOC concentrations with DGGE band intensities were conducted. Positive correlations, indicating production of the respective VOC or enhancement of microbial growth, and negative correlations, indicating the use of, or microbial inhibition by the respective compound, were found for the different VOCs. Measurement of the VOC emission pattern from a pure culture of Lactococcus lactis confirmed the positive correlations for the protonated masses 89 (tentatively identified as butyric acid), 63 (tentatively identified as dimethylsulfide), 69 (likely isoprene) and 73 (likely butanone).
[Abanda-Nkpwatt2006] Abanda-Nkpwatt, D., M. Muesch, J. Tschiersch, M. Boettner, and W. Schwab, "Molecular interaction between Methylobacterium extorquens and seedlings: growth promotion, methanol consumption, and localization of the methanol emission site.", J Exp Bot, vol. 57, no. 15: Biomolecular Food Technology, Technical University of Munich, Lise-Meitner-Strasse 34, D-85354 Freising, Germany., pp. 4025–4032, 2006.
Link: http://dx.doi.org/10.1093/jxb/erl173
Abstract
Four Methylobacterium extorquens strains were isolated from strawberry (Fragaria x ananassa cv. Elsanta) leaves, and one strain, called ME4, was tested for its ability to promote the growth of various plant seedlings. Seedling weight and shoot length of Nicotiana tabacum, Lycopersicon esculentum, Sinapis alba, and Fragaria vesca increased significantly in the presence of the pink-pigmented facultative methylotroph (PPFM), but the germination behaviour of seeds from six other plants was not affected. The cell-free supernatant of the bacterial culture stimulated germination, suggesting the production of a growth-promoting agent by the methylotroph. Methanol emitted from N. tabacum seedlings, as determined by proton-transfer-reaction mass spectrometry (PTR-MS), ranged from 0.4 to 0.7 ppbv (parts per billion by volume), while significantly lower levels (0.005 to 0.01 ppbv) of the volatile alcohol were measured when the seedlings were co-cultivated with M. extorquens ME4, demonstrating the consumption of the gaseous methanol by the bacteria. Additionally, by using cells of the methylotrophic yeast Pichia pastoris transformed with the pPICHS/GFP vector harbouring a methanol-sensitive promoter in combination with the green fluorescence protein (GFP) reporter gene, stomata were identified as the main source of the methanol emission on tobacco cotyledons. Methylobacterium extorquens strains can nourish themselves using the methanol released by the stomata and release an agent promoting the growth of the seedlings of some crop plants.
[Inomata2006a] Inomata, S., H. Tanimoto, N. Aoki, J. Hirokawa, and Y. Sadanaga, "A novel discharge source of hydronium ions for proton transfer reaction ionization: design, characterization, and performance.", Rapid Commun Mass Spectrom, vol. 20, no. 6: Atmospheric Environment Division, National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba, Ibaraki 305-8506, Japan. ino@nies.go.jp, pp. 1025–1029, 2006.
Link: http://dx.doi.org/10.1002/rcm.2405
Abstract
A novel ion source based on direct current (d.c.) discharge has been developed for proton transfer reaction ionization operated at relatively high ion drift tube pressure. The shape and geometry of the ion source are designed to maximize overall ion intensity and to minimize interference from sample air. The initial performance of the technique, including speciation and intensity of reagent ions, their stability, and the impact of artifact signals, is evaluated by means of a proton transfer reaction time-of-flight mass spectrometer (PTR-TOFMS) newly built in our laboratory. Intensities of the hydronium (H(3)O(+)) ions are typically (5-7) x 10(5) counts for a 1-min integration time with a duty cycle of approximately 1%. The fluctuations of the ion signals over a period of hours are within 4%. Although the formation of artifact ions from sample air (NO(+) and O(2) (+)), which react with volatile organic compounds (VOCs) and subsequently cause fragmentation, is observed as background signals in addition to hydronium and mono- and di-hydrate H(3)O(+) ions, intensities of both NO(+) and O(2) (+) ions are only approximately 0.5% of those of H(3)O(+) ions. Using our PTR-TOFMS system at a drift tube pressure of approximately 5 Torr, the detection sensitivities are significantly improved and the detection limits for propene, acetaldehyde, acetone, isoprene, benzene, toluene, and p-xylene are estimated to be at the sub-ppbv level for 1-min integration.
[Rogers2006] Rogers, TM., EP. Grimsrud, SC. Herndon, JT. Jayne, E. C Kolb, E. Allwine, H. Westberg, BK. Lamb, M. Zavala, LT. Molina, et al., "On-road measurements of volatile organic compounds in the Mexico City metropolitan area using proton transfer reaction mass spectrometry", International Journal of Mass Spectrometry, vol. 252, no. 1: Elsevier, pp. 26–37, 2006.
Link: http://www.sciencedirect.com/science/article/pii/S1387380606000583
Abstract
A proton transfer reaction mass spectrometer (PTR-MS) was redesigned and deployed to monitor selected hydrocarbon emissions from in-use vehicles as part of the Mexico City Metropolitan Area (MCMA) 2003 field campaign. This modified PTR-MS instrument provides the necessary time response (<2 s total cycle time) and sensitivity to monitor the rapidly changing hydrocarbon concentrations, within intercepted dilute exhaust emission plumes. Selected hydrocarbons including methanol, acetaldehyde, acetone, methyl tertiary butyl ether (MTBE), benzene and toluene were among the vehicle exhaust emission components monitored. A comparison with samples collected in canisters and analyzed by gas chromatography provides validation to the interpretation of the ion assignments and the concentrations derived using the PTR-MS. The simultaneous detection of multiple hydrocarbons in dilute vehicle exhaust plumes provides a valuable tool to study the impact of driving behavior on the exhaust gas emissions.
[Tholl2006] Tholl, D., W. Boland, A. Hansel, F. Loreto, U. Röse, SR, and JÖRG-PETER. SCHNITZLER, "Practical approaches to plant volatile analysis", The Plant Journal, vol. 45, no. 4: Wiley Online Library, pp. 540–560, 2006.
Link: http://onlinelibrary.wiley.com/doi/10.1111/j.1365-313X.2005.02612.x/full
Abstract
Plants emit volatile organic compounds (VOCs) that play important roles in their interaction with the environment and have a major impact on atmospheric chemistry. The development of static and dynamic techniques for headspace collection of volatiles in combination with gas chromatography–mass spectrometry analysis has significantly improved our understanding of the biosynthesis and ecology of plant VOCs. Advances in automated analysis of VOCs have allowed the monitoring of fast changes in VOC emissions and facilitated in vivo studies of VOC biosynthesis. This review presents an overview of methods for the analysis of plant VOCs, including their advantages and disadvantages, with a focus on the latest technical developments. It provides guidance on how to select appropriate instrumentation and protocols for biochemical, physiological and ecologically relevant applications. These include headspace analyses of plant VOCs emitted by the whole organism, organs or enzymes as well as advanced on-line analysis methods for simultaneous measurements of VOC emissions with other physiological parameters.
[Aprea2006] Aprea, E., F. Biasioli, G. Sani, C. Cantini, T. D. Maerk, and F. Gasperi, "Proton transfer reaction-mass spectrometry (PTR-MS) headspace analysis for rapid detection of oxidative alteration of olive oil.", J Agric Food Chem, vol. 54, no. 20: Agri-Food Quality Department, IASMA Research Center, Via E. Mach 1, 38010 San Michele all'Adige (TN), Italy. eugenio.aprea@iasma.it, pp. 7635–7640, Oct, 2006.
Link: http://dx.doi.org/10.1021/jf060970r
Abstract
Olive oil has been characterized by rapid proton transfer reaction-mass spectrometry (PTR-MS) headspace analysis without any concentration of the volatiles or pretreatment of the samples. Comparison of extra virgin and defective (rancid) samples, as described by a panel of sensory judges, and the monitoring of thermo-oxidation processes are discussed. Multivariate analysis of PTR-MS data has been carried out and cross-validated, providing (i) reliable classification models for extra virgin oil as opposed to defective oil and (ii) calibration models able to predict independently thermo-oxidative degradation and the corresponding peroxide value. PTR-MS fragmentation patterns of volatiles considered in this study are also reported.
[Inomata2006] Inomata, S., H. Tanimoto, S. Kato, J. Suthawaree, Y. Kanaya, P. Pochanart, Y. Liu, and Z. Wang, "PTR-MS measurements of non-methane volatile organic compounds during an intensive field campaign at the summit of Mount Tai, China", : June, 2006.
Link: http://www.atmos-chem-phys-discuss.net/9/26697/2009/
Abstract
Owing to recent industrialization, Central East China has become a significant source of air pollutants. To examine the processes controlling the chemistry and transport of tropospheric ozone, we continuously measured non-methane volatile organic compounds (NMVOCs) as part of an intensive field campaign at Mount Tai, China, in June 2006 (MTX2006), using proton transfer reaction mass spectrometry (PTR-MS). Temporal variations of NMVOCs were recorded in mass-scan mode from m/z 17 to m/z 300 during 12–30 June 2006. More than thirty kinds of NMVOCs were detected up to m/z 160, including alkenes, aromatics, alcohols, aldehydes, and ketones. Oxygenated VOCs were the predominant NMVOCs. During the night of 12 June, we observed an episode of high NMVOCs concentrations attributed to the burning of agricultural biomass. The ΔNMVOCs/ΔCO ratios derived by PTR-MS measurements for this episode are compared to emission ratios from various types of biomass burning as reviewed by Andreae and Merlet (2001) and to ratios recently measured by PTR-MS in tropical forests (Karl et al., 2007) and at urban sites (Warneke et al., 2007).
[Maerk2006] Märk, J., P. Pollien, C. Lindinger, I. Blank, and T. Märk, "Quantitation of furan and methylfuran formed in different precursor systems by proton transfer reaction mass spectrometry.", J Agric Food Chem, vol. 54, no. 7: Nestlé Research Center, Vers-chez-les-Blanc, 1000 Lausanne 26, Switzerland., pp. 2786–2793, Apr, 2006.
Link: http://dx.doi.org/10.1021/jf052937v
Abstract
Furan has recently received attention as a possibly hazardous compound occurring in certain thermally processed foods. Previous model studies have revealed three main precursor systems producing furan upon thermal treatment, i.e., ascorbic acid, Maillard precursors, and polyunsaturated lipids. We employed proton transfer reaction mass spectrometry (PTR-MS) as an on-line monitoring technique to study furan formation. Unambiguous identification and quantitation in the headspace was achieved by PTR-MS/gas chromatography-mass spectrometry coupling. Ascorbic acid showed the highest potential to generate furan, followed by glyceryl trilinolenate. Some of the reaction samples generated methylfuran as well, such as Maillard systems containing alanine and threonine as well as lipids based on linolenic acid. The furan yields from ascorbic acid were lowered in an oxygen-free atmosphere (30%) or in the presence of reducing agents (e.g., sulfite, 60%), indicating the important role of oxidation steps in the furan formation pathway. Furthermore, already simple binary mixtures of ascorbic acid and amino acids, sugars, or lipids reduced furan by 50-95%. These data suggest that more complex reaction systems result in much lower furan amounts as compared to the individual precursors, most likely due to competing reaction pathways.
[Gross2006] Gross, D. S., M. E. Gälli, M. Kalberer, A. S. H. Prevot, J. Dommen, R. M Alfarra, J. Duplissy, K. Gaeggeler, A. Gascho, A. Metzger, et al., "Real-time measurement of oligomeric species in secondary organic aerosol with the aerosol time-of-flight mass spectrometer", Analytical chemistry, vol. 78, no. 7: ACS Publications, pp. 2130–2137, 2006.
Link: http://pubs.acs.org/doi/abs/10.1021/ac060138l
[Granitto2006] Granitto, P. M., C. Furlanello, F. Biasioli, and F. Gasperi, "Recursive feature elimination with random forest for PTR-MS analysis of agroindustrial products", Chemometrics and Intelligent Laboratory Systems, vol. 83, no. 2: Elsevier, pp. 83–90, 2006.
Link: http://www.sciencedirect.com/science/article/pii/S0169743906000232
Abstract
In this paper we apply the recently introduced Random Forest-Recursive Feature Elimination (RF-RFE) algorithm to the identification of relevant features in the spectra produced by Proton Transfer Reaction-Mass Spectrometry (PTR-MS) analysis of agroindustrial products. The method is compared with the more traditional Support Vector Machine-Recursive Feature Elimination (SVM-RFE), extended to allow multiclass problems, and with a baseline method based on the Kruskal–Wallis statistic (KWS). In particular, we apply all selection methods to the discrimination of nine varieties of strawberries and six varieties of typical cheeses from Trentino Province, North Italy. Using replicated experiments we estimate unbiased generalization errors. Our results show that RF-RFE outperforms SVM-RFE and KWS on the task of finding small subsets of features with high discrimination levels on PTR-MS data sets. We also show how selection probabilities and features co-occurrence can be used to highlight the most relevant features for discrimination.
[Graus2006] Graus, M., A. Hansel, A. Wisthaler, C. Lindinger, R. Forkel, K. Hauff, M. Klauer, A. Pfichner, B. Rappenglück, D. Steigner, et al., "A relaxed-eddy-accumulation method for the measurement of isoprenoid canopy-fluxes using an online gas-chromatographic technique and PTR-MS simultaneously", Atmospheric Environment, vol. 40: Elsevier, pp. 43–54, 2006.
Link: http://www.sciencedirect.com/science/article/pii/S1352231006003190
Abstract
A relaxed-eddy-accumulation set-up using an online gas-chromatographic technique and proton-transfer-reaction mass spectrometry was applied to determine isoprenoid fluxes above a Norway spruce forest in July 2001/2002. The system was quality assured and its suitability for determination of canopy fluxes of isoprenoids was demonstrated. Flux measurements of oxygenated hydrocarbons failed the data quality check due to artefacts presumably arising from line and ozone-scrubber effects. Observations of turbulent fluxes of isoprenoids during the two field experiments show good agreements with primary flux data derived from enclosure measurements and modelling results using a canopy-chemistry emission model (CACHE).
[Mestres2006] Mestres, M., R. Kieffer, and A. Buettner, "Release and perception of ethyl butanoate during and after consumption of whey protein gels: relation between textural and physiological parameters.", J Agric Food Chem, vol. 54, no. 5: Facultat d'Enologia, Dept Química Analítica i Orgànica, Universitat Rovira i Virgili, Tarragona, Spain., pp. 1814–1821, Mar, 2006.
Link: http://dx.doi.org/10.1021/jf0517501
Abstract
The influence of gel texture on parameters such as positioning of food material in the oral cavity during mastication, and salivation, and their influence on aroma release in vivo was studied. Retronasal perception was followed by means of time-resolved sensory evaluation, while volatile release patterns were observed by means of PTR-MS. A clear correlation was found between individual-specific consumption patterns and the respective sensory perception. Also, gel texture could be clearly correlated with respective physicochemical release patterns in vivo and to the corresponding retronasal aroma perception.
[1501] Holzinger, R.., A.. Lee, M.. McKay, and A.. H. Goldstein, "Seasonal variability of monoterpene emission factors for a ponderosa pine plantation in California", Atmospheric Chemistry and Physics, vol. 6, pp. 1267–1274, Apr, 2006.
Link: http://nature.berkeley.edu/ahg/pubs/seasonal.pdf
Abstract
<p>Monoterpene fluxes have been measured over an 11 month period from June 2003 to April 2004. During all seasons ambient air temperature was the environmental factor most closely related to the measured emission rates. The monoterpene flux was modeled using a basal emission rate multiplied by an exponential function of a temperature, following the typical practice for modelling temperature dependent biogenic emissions. A basal emission of 1.0 μmol h&minus;1 m&minus;2 (at 30&deg;C, based on leaf area) and a temperature dependence (β) of 0.12&deg;C&minus;1 reproduced measured summer emissions well but underestimated spring and winter measured emissions by 60&ndash;130%. The total annual monoterpene emission may be underestimated by &nbsp;50% when using a model optimized to reproduce monoterpene emissions in summer. The long term dataset also reveals an indirect connection between non-stomatal ozone and monoterpene flux beyond the dependence on temperature that has been shown for both fluxes.</p>
[Ammann2006] Ammann, C., A. Brunner, C. Spirig, and A. Neftel, "Technical note: Water vapour concentration and flux measurements with PTR-MS", Atmospheric Chemistry and Physics, vol. 6, no. 12: Copernicus GmbH, pp. 4643–4651, 2006.
Link: http://www.atmos-chem-phys.net/6/4643/2006/acp-6-4643-2006.pdf
[Forkel2006] Forkel, R., O. Klemm, M. Graus, B. Rappenglück, W. R. Stockwell, W. Grabmer, A. Held, A. Hansel, and R. Steinbrecher, "Trace gas exchange and gas phase chemistry in a Norway spruce forest: A study with a coupled 1-dimensional canopy atmospheric chemistry emission model", Atmospheric Environment, vol. 40: Elsevier, pp. 28–42, 2006.
Link: http://www.sciencedirect.com/science/article/pii/S1352231006003189
Abstract
Numerical modelling is an efficient tool to investigate the role of chemical degradation of biogenic volatile organic compounds (BVOC) and the effect of dynamical processes on BVOC and product mixing ratios within and above forest canopies. The present study shows an application of the coupled canopy-chemistry model CACHE to a Norway spruce forest at the Waldstein (Fichtelgebirge, Germany). Simulated courses of temperature, trace gas mixing ratios, and fluxes are compared with measurements taken during the BEWA2000 field campaigns. The model permits the interpretation of the observed diurnal course of ozone and VOC by investigating the role of turbulent exchange, chemical formation and degradation, emission, and deposition during the course of the day. The simulation results show that BVOC fluxes into the atmosphere are 10–15% lower than the emission fluxes on branch basis due to chemical BVOC degradation within the canopy. BVOC degradation by the NO3 radical was found to occur in the lower part of the canopy also during daytime. Furthermore, the simulations strongly indicate that further research is still necessary concerning the emission and deposition of aldehydes and ketones.
[Grabmer2006] Grabmer, W., J. Kreuzwieser, A. Wisthaler, C. Cojocariu, M. Graus, H. Rennenberg, D. Steigner, R. Steinbrecher, and A. Hansel, "VOC emissions from Norway spruce ( Picea abies L.[Karst]) twigs in the field�Results of a dynamic enclosure study", Atmospheric Environment, vol. 40: Elsevier, pp. 128–137, 2006.
Link: http://www.sciencedirect.com/science/article/pii/S135223100600327X
Abstract
During the 2002 summer intensive field campaign of BEWA2000 a proton-transfer-reaction mass spectrometer (PTR-MS) was used for online determination of volatile organic compounds (VOC) emitted by Norway spruce (Picea abies L. [Karst]) twigs in a dynamic sampling enclosure. Emissions of isoprenoids (isoprene and monoterpenes) and oxygenated VOC (OVOC; acetaldehyde, acetone, methanol, and ethanol) were investigated. Emissions showed clear diurnal patterns with high daytime emission rates amounting to 1.8 μg C g−1 dwt h−1 for the sum of monoterpenes and in the range of 0.1 to 0.6 μg C g−1 dwt h−1 for isoprene>acetone>ethanol>methanol. Data were used to validate existing models on isoprene and monoterpene emissions and to discuss environmental and physiological factors affecting VOC emissions. Isoprene and acetaldehyde emission rates were best modelled applying the Guenther 1993 temperature and solar radiation algorithm. Emissions of monoterpenes, acetone and ethanol were best described by a temperature-only exponential algorithm. Using these model approaches a maximum emission variability of 66% was covered (isoprene). Poor r2 values ranging from 0.15 to 0.42 were typical for oxygenated VOC emission modelling indicating the need for model improvement e.g. development of process-based models describing the emission as a result of biochemical de novo synthesis as well as physico-chemical transport properties inside the leaves.
[DeGouw2006] De Gouw, JA., C. Warneke, A. Stohl, AG. Wollny, CA. Brock, OR. Cooper, JS. Holloway, M. Trainer, FC. Fehsenfeld, EL. Atlas, et al., "Volatile organic compounds composition of merged and aged forest fire plumes from Alaska and western Canada", Journal of geophysical research, vol. 111, no. D10: American Geophysical Union, pp. D10303, 2006.
Link: http://www.agu.org/pubs/crossref/2006/2005JD006175.shtml
Abstract
The NOAA WP-3 aircraft intercepted aged forest fire plumes from Alaska and western Canada during several flights of the NEAQS-ITCT 2k4 mission in 2004. Measurements of acetonitrile (CH3CN) indicated that the air masses had been influenced by biomass burning. The locations of the plume intercepts were well described using emissions estimates and calculations with the transport model FLEXPART. The best description of the data was generally obtained when FLEXPART injected the forest fire emissions to high altitudes in the model. The observed plumes were generally drier than the surrounding air masses at the same altitude, suggesting that the fire plumes had been processed by clouds and that moisture had been removed by precipitation. Different degrees of photochemical processing of the plumes were determined from the measurements of aromatic VOCs. The removal of aromatic VOCs was slow considering the transport times estimated from the FLEXPART model. This suggests that the average OH levels were low during the transport, which may be explained by the low humidity and high concentrations of carbon monoxide and other pollutants. In contrast with previous work, no strong secondary production of acetone, methanol and acetic acid is inferred from the measurements. A clear case of removal of submicron particle volume and acetic acid due to precipitation scavenging was observed.
2007
[Sinha2007] Sinha, V., J. Williams, M. Meyerhöfer, U. Riebesell, AI. Paulino, and A. Larsen, "Air-sea fluxes of methanol, acetone, acetaldehyde, isoprene and DMS from a Norwegian fjord following a phytoplankton bloom in a mesocosm experiment", Atmospheric Chemistry and Physics, vol. 7, no. 3: Copernicus GmbH, pp. 739–755, 2007.
Link: http://www.atmos-chem-phys.net/7/739/2007/acp-7-739-2007.html
Abstract
{The ocean's influence on volatile organic compounds (VOCs) in the atmosphere is poorly understood. This work characterises the oceanic emission and/or uptake of methanol, acetone, acetaldehyde, isoprene and dimethyl sulphide (DMS) as a function of photosynthetically active radiation (PAR) and a suite of biological parameters. The measurements were taken following a phytoplankton bloom, in May/June 2005 with a proton transfer reaction mass spectrometer (PTR-MS), from mesocosm enclosures anchored in the Raunefjord, Southern Norway. The net flux of methanol was always into the ocean, and was stronger at night. Isoprene and acetaldehyde were emitted from the ocean, correlating with light (ravcorr
[Aprea2007a] Aprea, E., F. Biasioli, F. Gasperi, D. Mott, F. Marini, and T. D. Maerk, "Assessment of Trentingrana cheese ageing by proton transfer reaction-mass spectrometry and chemometrics", International dairy journal, vol. 17, no. 3: Elsevier, pp. 226–234, 2007.
Link: http://www.sciencedirect.com/science/article/pii/S0958694606000501
Abstract
Proton transfer reaction-mass spectrometry (PTR-MS) data have been analysed by chemometric techniques to monitor cheese ageing by means of on-line direct head-space gas analysis. Twenty cheese loaves of Trentingrana, a trademarked cheese produced in northern Italy, of different origin and ripening degree, were sampled over the whole Trentingrana production area. An increase of the spectral intensity with ripening has been observed for most of the PTR-MS peaks and a univariate analysis identified 16 mass peaks that were significantly different for ripened and young cheeses, respectively. Moreover, the usefulness of different discriminant analyses and class modelling techniques have been investigated. Discriminant Partial Least Squares analysis, while indicating average behaviour and possible outliers, was not able to correctly classify all samples. Soft class modelling performed better and allowed a 100% correct classification. Partial least square calibration predicted the ageing time of each loaf with reasonable accuracy with a maximum cross-validation error of 3.5 months.
[Yelvington2007] Yelvington, P. E., S. C. Herndon, J. C. Wormhoudt, J. T. Jayne, R. C. Miake-Lye, B. W Knighton, and C. Wey, "Chemical speciation of hydrocarbon emissions from a commercial aircraft engine", Journal of Propulsion and Power, vol. 23, no. 5, pp. 912–918, 2007.
Link: http://arc.aiaa.org/doi/abs/10.2514/1.23520

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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).
Link

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.
Link

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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