"Evaluation of the use of bioethanol fuelled buses based on ambient air pollution screening and on-road measurements.",
Sci Total Environ
, vol. 452-453, pp. 40–49, May, 2013.
<p>Mitigation measures to reduce greenhouse gas emissions may have adverse effects on urban air quality and human exposure to harmful pollutants. The use of bioethanol fuelled vehicles is increasing worldwide and may create new undesired pollution effects. Different measurement campaigns were performed in a pilot study to contribute to the understanding of the consequences associated with the use of bioethanol blended fuel (E95) on a series of pollutants. Ambient screening measurements of NO2, O3, acetic acid, formaldehyde and acetaldehyde were performed at different urban locations, exposed and not exposed to the circulation of bioethanol buses. In addition, volatile organic compounds were measured at the exhaust pipe of a bioethanol fuelled bus, both under idling conditions (carbonyls; DNPH cartridge) and under on-road driving conditions applying online monitoring (PTR-TOF). Higher ambient acetaldehyde values were measured at locations exposed to bioethanol fuelled buses than at locations not exposed, and very high acetaldehyde and acetic acid values were measured from the exhaust pipe during driving conditions (acetaldehyde>150 ppm; acetic acid ≈ 20-30 ppm) and modelled at close distance to the bioethanol bus. Human exposure to high concentration of acetaldehyde is expected, and it may involve a significantly increased chance in developing cancer. The high concentration of acetic acid will involve odour annoyance and significant material degradation or corrosion.</p>
[Raseetha2013] "Evolution of antioxidant enzymes activity and volatile release during storage of processed broccoli ( Brassica oleracea L. italica)",
LWT-Food Science and Technology
: Elsevier, 2013.
The objective of this study was to investigate the effects of temperature treatments (i.e. freezing at −18 °C, cool storage at 4 °C and heating at 50, 70 and 100 °C for 10 min) on the activity of peroxidase (POD), lipoxygenase (LOX), ascorbic acid oxidase (AAO), superoxide dismutase (SOD) and catalase (CAT) in broccoli (Brassica oleracea L. italica). Volatiles released during storage at 20 °C for 24 h were monitored using on-line Proton Transfer Reaction Mass Spectrometry (m/z 21–180). Partial Least Square Regression (PLSR) was used to evaluate possible correlations between enzymes and volatiles released during storage. The results showed that temperature treatment had significant effect on all enzymes, except LOX. Temperature treatment at 70 °C resulted in at least 65% decrease in POD and AAO activity. In contrast, SOD and CAT activities generally increased during storage after temperature treatments. PLSR2 results showed that volatiles released after different temperature treatments and 24 h storage had a strong correlation with the residual activity of POD, AAO and SOD but not CAT and LOX. PLSR1 results suggested that POD had the highest correlation to volatile release during storage of processed broccoli followed by AAO, SOD, CAT and LOX (the least).
[Joyce2013] "Fast Phenotyping of LFS-Silenced (Tearless) Onions by Desorption Electrospray Ionization Mass Spectrometry (DESI-MS).",
J Agric Food Chem
, vol. 61, no. 7: The New Zealand Institute for Plant and Food Research Limited , Private Bag 4704, Christchurch, New Zealand., pp. 1449–1456, Feb, 2013.
Fast MS techniques have been applied to the analysis of sulfur volatiles in Allium species and varieties to distinguish phenotypes. Headspace sampling by proton transfer reaction (PTR) MS and surface sampling by desorption electrospray ionization (DESI) MS were used to distinguish lachrymatory factor synthase (LFS)-silenced (tearless; LFS-) onions from normal, LFS-active (tear-inducing; LFS+), onions. PTR-MS showed lower concentrations of the lachrymatory factor (LF, 3) and dipropyl disulfide 12 from tearless onions. DESI-MS of the tearless onions confirmed the decreased LF 3 and revealed much higher concentrations of the sulfenic acid condensates. Using DESI-MS with MS(2) could distinguish zwiebelane ions from thiosulfinate ions. DESI-MS gave reliable fast phenotyping of LFS+ versus LFS- onions by simply scratching leaves and recording the extractable ions for <0.5 min. DESI-MS leaf compound profiles also allowed the rapid distinction of a variety of Allium cultivars to aid plant breeding selections.
[Manikam2013] "Feasibility of using combined Proton Transfer Reaction Mass Spectrometry (PTR-MS) technique and biochemical analyses to assess the quality of broccoli florets during postharvest storage, handling and temperature treatments",
: University of Otago, 2013.
The objective of this research was to gain a better understanding of the relationship between changes in volatiles release, colour and biochemical markers (i.e. pigment content, antioxidant levels, activity of enzymes and oxidative damage levels) during postharvest storage and mechanical damage. This study attempted to find potential volatile markers, using Proton Transfer Reaction Mass Spectrometry (PTR-MS), that were statistically correlated with biochemical and physiological changes associated with postharvest storage and mechanical damage. Multivariate statistical analysis and regression analysis using Partial Least Squares Regression (PLSR) was used to evaluate possible correlations. It is hypothesized that volatile markers in combination with biochemical analyses can be used to assess quality changes during postharvest storage and handling of broccoli. The intensity of protonated volatile organic compounds with the mass ions m/z 33 and m/z 49 were tentatively identified as methanol and methanethiol. While both increased, methanol was the dominant volatile detected. The increase of these mass ions was observed at the onset of senescence (Day 3, 23 °C), at which point chlorophyll breakdown was initiated, resulting in colour change from green to yellow. Validations were carried out using cytokinin 6-benzylaminopurine (BAP) which delays the onset of senescence for several days. Application of BAP delayed senescence in a concentration dependent manner, with 50 ppm or above BAP slowed the rate of senescence, as determined by chlorophyll loss measurement. Application of BAP also slowed the rate of methanol release. Colour change as a marker for the onset of senescence was validated using markers of oxidative damage and defence, which are known to be key indicators of the onset and progression of senescence. Depending on the BAP concentrations, measurements of antioxidant enzymes, non-enzymatic antioxidants and markers of oxidative damage confirmed that senescence was delayed. To further determine if the release of methanol was due to major cellular disruption, which occurs during senescence, broccoli florets at different stages of senescence were subjected to severe mechanical damage and the damaged tissues were monitored for up to six hours. In addition, broccoli florets were subjected to different temperature treatments ranging from -18 to 100 °C to simulate different types of cellular and metabolic disruption. The stage of senescence prior to mechanical damage was the critical factor determining the cellular and metabolic integrity of broccoli samples six hours following the damage event although mechanical damage accelerated the breakdown of photosynthetic pigments, the inactivation of antioxidant enzymes, the degradation of non-enzymatic antioxidants and increases in the levels of oxidative damage and methanol. The temperature treatments (-18, 50, 70 and 100 °C) disrupted cellular metabolism as evidenced by changes in the activities of several enzymes (POD, SOD, CAT and AAO) and led to significant increases in…
[Kohl2013b] "First observation of a potential non-invasive breath gas biomarker for kidney function.",
J Breath Res
, vol. 7, no. 1: Ionimed Analytik GmbH, Eduard Bodem Gasse 3, A-6020 Innsbruck, Austria., pp. 017110, Mar, 2013.
We report on the search for low molecular weight molecules-possibly accumulated in the bloodstream and body-in the exhaled breath of uremic patients with kidney malfunction. We performed non-invasive analysis of the breath gas of 96 patients shortly before and several times after kidney transplantation using proton-transfer-reaction mass spectrometry (PTR-MS), a very sensitive technique for detecting trace amounts of volatile organic compounds. A total of 642 individual breath analyses which included at least 41 different chemical components were carried out. Correlation analysis revealed one particular breath component with a molecular mass of 114 u (unified atomic mass units) that clearly correlated with blood serum creatinine, which is the currently accepted marker for assessing the function of the kidney. In particular, daily urine production showed good correlation with the identified breath marker. An independent set of seven samples taken from three patients at the onset of dialysis and three controls with normal kidney function confirmed a significant difference in concentration between patients and controls for a compound with a molecular mass of 114.1035 u using high mass resolving proton-transfer-reaction time-of-flight mass spectrometry (PTR-TOF-MS). A chemical composition of CHO was derived for the respective component. Fragmentation experiments on the same samples using proton-transfer-reaction triple-quadrupole tandem mass spectrometry (PTR-QqQ-MS) suggested that this breath marker is a C-ketone or a branched C-aldehyde. Non-invasive real-time monitoring of the kidney function via this breath marker could be a possible future procedure in the clinical setting.
 "Fragmentation of allylmethylsulfide by chemical ionization: dependence on humidity and inhibiting role of water.",
J Phys Chem A
, vol. 117, pp. 5149–5160, Jun, 2013.
<p>We report on a previously unknown reaction mechanism involving water in the fragmentation reaction following chemical ionization. This result stems from a study presented here on the humidity-dependent and energy-dependent endoergic fragmentation of allyl methyl sulfide (AMS) upon protonation in a proton transfer reaction-mass spectrometer (PTR-MS). The fragmentation pathways were studied with experimental (PTR-MS) and quantum chemical methods (polarizable continuum model (PCM), microhydration, studied at the MP2/6-311+G(3df,2p)//MP2/6-31G(d,p) level of theory). We report in detail on the energy profiles, reaction mechanisms, and proton affinities (G4MP2 calculations). In the discovered reaction mechanism, water reduces the fragmentation of protonated species in chemical ionization. It does so by direct interaction with the protonated species via covalent binding (C3H5(+)) or via association (AMS·H(+)). This stabilizes intermediate complexes and thus overall increases the activation energy for fragmentation. Water thereby acts as a reusable inhibitor (anticatalyst) in chemical ionization. Moreover, according to the quantum chemical (QC) results, when water is present in abundance it has the opposite effect and enhances fragmentation. The underlying reason is a concentration-dependent change in the reaction principle from active inhibition of fragmentation to solvation, which then enhances fragmentation. This amphoteric behavior of water is found for the fragmentation of C3H5(+) to C3H3(+), and similarly for the fragmentation of AMS·H(+) to C3H5(+). The results support humidity-dependent quantification efforts for PTR-MS and chemical ionization mass spectrometry (CIMS). Moreover, the results should allow for a better understanding of ion-chemistry in the presence of water.</p>
[Edtbauer2013] "From Proton-Transfer-Reaction Mass Spectrometry (PTR-MS) to Universal Trace Gas Analysis with Selective-Reagent-Ionization Mass Spectrometry (SRI-MS) in Kr+ mode",
, pp. 76, 2013.
 "Headspace analysis of new psychoactive substances using a Selective Reagent Ionisation-Time of Flight-Mass Spectrometer",
International Journal of Mass Spectrometry
, pp. -, 2013.
<p>The rapid expansion in the number and use of new psychoactive substances presents a significant analytical challenge because highly sensitive instrumentation capable of detecting a broad range of chemical compounds in real-time with a low rate of false positives is required. A Selective Reagent Ionisation-Time of Flight-Mass Spectrometry (SRI-ToF-MS) instrument is capable of meeting all of these requirements. With its high mass resolution (up to m/Δm of 8000), the application of variations in reduced electric field strength (E/N) and use of different reagent ions, the ambiguity of a nominal (monoisotopic) m/z is reduced and hence the identification of chemicals in a complex chemical environment with a high level of confidence is enabled. In this study we report the use of a SRI-ToF-MS instrument to investigate the reactions of H3O+, O2+, NO+ and Kr+ with 10 readily available (at the time of purchase) new psychoactive substances, namely 4-fluoroamphetamine, methiopropamine, ethcathinone, 4-methylethcathinone, N-ethylbuphedrone, ethylphenidate, 5-MeO-DALT, dimethocaine, 5-(2-aminopropyl)benzofuran and nitracaine. In particular, the dependence of product ion branching ratios on the reduced electric field strength for all reagent ions was investigated and is reported here. The results reported represent a significant amount of new data which will be of use for the development of drug detection techniques suitable for real world scenarios.</p>
 "Heterogeneous OH oxidation of biomass burning organic aerosol surrogate compounds: assessment of volatilisation products and the role of OH concentration on the reactive uptake kinetics.",
Phys Chem Chem Phys
, vol. 15, pp. 5898–5915, Apr, 2013.
<p>The reactive uptake coefficients (γ) of OH by levoglucosan, abietic acid, and nitroguaiacol serving as surrogate compounds for biomass burning aerosol have been determined employing a chemical ionisation mass spectrometer coupled to a rotating-wall flow-tube reactor over a wide range of [OH] ∼10(7)-10(11) molecule cm(-3). Volatilisation products of these organic substrates due to heterogeneous oxidation by OH have been determined at 1 atm using a high resolution proton transfer reaction time-of-flight mass spectrometer (HR-PTR-ToF-MS). γ range within 0.05-1 for [OH] = 2.6 × 10(7)-3 × 10(9) molecule cm(-3) for all investigated organic compounds, but decrease to 0.008-0.034 for [OH] = 4.1 × 10(10)-6.7 × 10(10) molecule cm(-3). γ as a function of [OH] can be described by a Langmuir-Hinshelwood model, neglecting bulk processes, suggesting that despite its strong reactivity, OH is mobile on surfaces prior to reaction. The best fit Langmuir-Hinshelwood parameters on average are K(OH) = 3.81 × 10(-10) cm(3) molecule(-1) and k(s) = 9.71 × 10(-17) cm(2) molecule(-1) s(-1) for all of the investigated organic compounds. Volatilised products have been identified indicating enhancements over background of 50% up to a factor of 15. Amongst the common volatile organic compounds (VOCs) identified between levoglucosan, abietic acid, and nitroguaiacol were methanol, acetaldehyde, formic acid, and acetic acid. VOCs having the greatest enhancement over background were glucic acid from levoglucosan, glycolic acid from abietic acid, and methanol and nitric acid from nitroguaiacol. Reaction mechanisms leading to the formation of glucic acid, glycolic acid, methanol, and nitric acid are proposed. Estimated lower limits of atmospheric lifetimes of biomass burning aerosol particles, 200 nm in diameter, by heterogeneous OH oxidation under fresh biomass burning plume conditions are ∼2 days and up to ∼2 weeks for atmospheric background conditions. However, estimated lifetimes depend crucially on [OH] and corresponding γ, emphasising the need to determine γ under relevant conditions.</p>
[Romano2013] "Hyphenation of PTR-ToF-MS and newly developed software provides a new effective tool for the study of inter-individual differences among tasters",
, pp. 59, 2013.
 "Impact of fruit piece structure in yogurts on the dynamics of aroma release and sensory perception.",
, vol. 18, pp. 6035–6056, 2013.
<p>The aim of this work was to gain insight into the effect of food formulation on aroma release and perception, both of which playing an important role in food appreciation. The quality and quantity of retronasal aroma released during food consumption affect the exposure time of olfactory receptors to aroma stimuli, which can influence nutritional and hedonic characteristics, as well as consumption behaviors. In yogurts, fruit preparation formulation can be a key factor to modulate aroma stimulation. In this context, the impact of size and hardness of fruit pieces in fat-free pear yogurts was studied. Proton Transfer Reaction-Mass Spectrometry (PTR-MS) was used to allow sensitive and on-line monitoring of volatile odorous compound release in the breath during consumption. In parallel, a trained panel used sensory profile and Temporal Dominance of Sensations (TDS) methods to characterize yogurt sensory properties and their dynamic changes during consumption. Results showed that the size of pear pieces had few effects on aroma release and perception of yogurts, whereas fruit hardness significantly influenced them. Despite the fact that yogurts presented short and similar residence times in the mouth, this study showed that fruit preparation could be an interesting formulation factor to enhance exposure time to stimuli and thus modify food consumption behaviors. These results could be taken into account to formulate new products that integrate both nutritional and sensory criteria.</p>
[Deleris2013] "Improvement in the understanding of aroma compound retention and release in naso-oro-pharyngeal cavity",
, pp. 156, 2013.
 "Interpretation of volatile organic compound measurements byproton-transfer-reaction mass spectrometry over the deepwaterhorizon oil spill",
International Journal of Mass Spectrometry
, vol. (in press), 2013.
<p>tA proton-transfer-reaction mass spectrometer (PTR-MS) was used onboard the NOAA WP-3D aircraftfor atmospheric measurements over the Deepwater Horizon (DWH) oil spill in the Gulf of Mexico in2010. A mass spectrum obtained by PTR-MS downwind from the accident site revealed the presenceof a complex mixture of volatile organic compounds (VOCs). Here, we interpret this mass spectrum bycomparing it with mass spectra of crude oil, gasoline and diesel samples measured in the laboratory.Aromatics were less abundant over the spill than from crude oil samples, due to the dissolution of thesespecies in the seawater. The mass spectra obtained from aircraft measurements and crude oil samplesboth show strong signals at masses with mass-to-charge ratio (m/z) of 14 × n ± 1, including 43, 57, 69,71, 83, 85, 97 and 111Yamu. PTR-MS coupled with a gas chromatograph was used to identify majormass signals from crude oil samples. Cycloalkanes are important contributors to the signals of mass m/z14 × n ± 1, especially for masses 69, 83, 97 and 111 amu. Aromatics could be interpreted from their specificmasses without significant interference for crude oil vapors, but the interferences to benzene from higheraromatics can be significant as crude oil evaporates. The interpretation of DWH mass spectrum is notonly helpful in understanding the atmospheric emissions associated with the DWH oil spill, but also forthe interpretation of PTR-MS measurements in urban air, near natural oil seeps and oil as well as naturalgas extraction activities.</p>
[Kassebacher2013] "Investigations of chemical warfare agents and toxic industrial compounds with proton-transfer-reaction mass spectrometry for a real-time threat monitoring scenario.",
Rapid Commun Mass Spectrom
, vol. 27, no. 2: Austria., pp. 325–332, Jan, 2013.
Security and protection against terrorist attacks are major issues in modern society. One especially challenging task is the monitoring and protection of air conditioning and heating systems of buildings against terrorist attacks with toxic chemicals. As existing technologies have low selectivity, long response times or insufficient sensitivity, there is a need for a novel approach such as we present here.We have analyzed various chemical warfare agents (CWAs) and/or toxic industrial compounds (TICs) and related compounds, namely phosgene, diphosgene, chloroacetone, chloroacetophenone, diisopropylaminoethanol, and triethyl phosphate, utilizing a high-resolution proton-transfer-reaction time-of-flight mass spectrometry (PTR-TOFMS) instrument with the objective of finding key product ions and their intensities, which will allow a low-resolution quadrupole mass spectrometry based PTR-MS system to be used with high confidence in the assignment of threat agents in the atmosphere.We obtained high accuracy PTR-TOFMS mass spectra of the six compounds under study at two different values for the reduced electric field in the drift tube (E/N). From these data we have compiled a table containing product ions, and isotopic and E/N ratios for highly selective threat compound detection with a compact and cost-effective quadrupole-based PTR-MS instrument. Furthermore, using chloroacetophenone (tear gas), we demonstrated that this instrument's response is highly linear in the concentration range of typical Acute Exposure Guideline Levels (AEGLs).On the basis of the presented results it is possible to develop a compact and cost-effective PTR-QMS instrument that monitors air supply systems and triggers an alarm as soon as the presence of a threat agent is detected. We hope that this real-time surveillance device will help to seriously improve safety and security in environments vulnerable to terrorist attacks with toxic chemicals.
[Ting2013] "In-vivo volatile organic compound (VOC) release from fresh-cut apple cultivars: PTR-Quad-MS and PTR-ToF-MS",
, pp. 229, 2013.
 "Ion mobility spectrometry for pharmacokinetic studies–exemplary application.",
J Breath Res
, vol. 7, pp. 046008, Dec, 2013.
<p>Breath analysis is an attractive non-invasive method for diagnosis and therapeutic monitoring. It uses endogenously produced compounds and metabolites of isotopically labeled precursors. In order to make such tests clinically useful, it is important to have relatively small portable instruments detecting volatile compounds within short time. A particularly promising analytical technique is ion mobility spectrometry (IMS) coupled to a multi capillary column (MCC). This paper focuses on demonstrating the suitability of breath analysis for pharmacokinetic applications using MCC-IMS with respect to practicability and reproducibility testing the model substrate eucalyptol. Validation of the MCC-IMS measurements were performed using proton transfer reaction mass spectrometry (PTR-MS) and resulted in an excellent correspondence of the time-dependent concentrations presented by the two different analytical techniques. Moreover, the good accordance in variance of kinetic parameters with repeated measures, and the determined inter-subject differences indicate the eligibility of the analysis method.</p>
[Fischer2013a] "The LCU: Versatile Trace Gas Calibration",
6th International PTR-MS Conference on Proton Transfer Reaction Mass Spectrometry and Its Applications
, pp. 192, 2013.
 "Massive emissions of carcinogenic benzenoids from paddy residue burning in North India",
, vol. 104, pp. 1703-1709, 2013.
<p>Benzenoids are organic pollutants emitted mainly by traffic and industrial sources. Here, using a combination of on-line in situ PTR-MS measurements of several benzenoids and methyl cyanide (a biomassburning tracer), satellite remote sensing data of fire counts and back trajectory of air masses at a site in Mohali, we show that massive amounts of benzenoids are released from post-harvest paddy residue burning. Two periods, one that was not influenced by paddy residue burning (period 1, 18 : 00–03 : 30 IST; 5–6 October 2012) and another which was strongly influenced by paddy residue burning (period 2, 18 : 00– 03 : 30 IST; 3–4 November 2012) were chosen to assess normal and perturbed levels. Peak values of 3830 ppb CO, 100 ppb NOx, 40 ppb toluene, 16 ppb benzene, 24 ppb for sum of all C-8 benzenoids and 13 ppb for sum of all C-9 benzenoids were observed during period 2 (number of measurements in period 2 = 570) with the average enhancements in benzenoid levels being more than 300%. The ozone formation potential of benzenoids matched that of CO, with both contributing 5 ppb/h each. Such high levels of benzenoids for 1–2 months in a year aggravate smog events and can enhance cancer risks in northwestern India.</p>
[Feilberg2013] "Measurement of H2S by PTR-MS: Experiences and implications",
, pp. 98, 2013.
[Pleil2013] "Meeting reports for 2013: recent advances in breath biomarker research",
Journal of breath research
, vol. 7, no. 2: IOP Publishing, pp. 029001, 2013.
 "Methanol, acetaldehyde, and acetone in the surface waters of the Atlantic Ocean",
Journal of Geophysical Research: Oceans
, vol. 118, pp. 5412–5425, 2013.
<p>Oceanic methanol, acetaldehyde, and acetone concentrations were measured during an Atlantic Meridional Transect (AMT) cruise from the UK to Chile (49°N to 39°S) in 2009. Methanol (48–361 nM) and acetone (2–24 nM) varied over the track with enrichment in the oligotrophic Northern Atlantic Gyre. Acetaldehyde showed less variability (3–9 nM) over the full extent of the transect. These oxygenated volatile organic compounds (OVOCs) were also measured subsurface, with methanol and acetaldehyde mostly showing homogeneity throughout the water column. Acetone displayed a reduction below the mixed layer. OVOC concentrations did not consistently correlate with primary production or chlorophyll-a levels in the surface Atlantic Ocean. However, we did find a novel and significant negative relationship between acetone concentration and bacterial leucine incorporation, suggesting that acetone might be removed by marine bacteria as a source of carbon. Microbial turnover of both acetone and acetaldehyde was confirmed. Modeled atmospheric data are used to estimate the likely air-side OVOC concentrations. The direction and magnitude of air-sea fluxes vary for all three OVOCs depending on location. We present evidence that the ocean may exhibit regions of acetaldehyde under-saturation. Extrapolation suggests that the Atlantic Ocean represents an overall source of these OVOCs to the atmosphere at 3, 3, and 1 Tg yr−1 for methanol, acetaldehyde, and acetone, respectively.</p>
[Fischer2013] "Micro-Capillary-Column PTR-TOF",
6th International PTR-MS Conference on Proton Transfer Reaction Mass Spectrometry and Its Applications
, pp. 162, 2013.
[Tsevdou2013] "Monitoring the effect of high pressure and transglutaminase treatment of milk on the evolution of flavour compounds during lactic acid fermentation using PTR-ToF-MS.",
, vol. 138, no. 4: Laboratory of Food Chemistry and Technology, School of Chemical Engineering, National Technical University of Athens, Polytechnioupoli Zografou, Zografou 15780, Athens, Greece., pp. 2159–2167, Jun, 2013.
In this study, the effects of thermal or high hydrostatic pressure (HHP) treatment of a milk base in the absence or presence of a transglutaminase (TGase) protein cross-linking step on the flavour development of yoghurt were investigated. The presence of several tentatively identified volatile flavour compounds (VOCs), both during the enzymatic treatment and the lactic acid fermentation of the milk base, were monitored using a proton transfer reaction time-of-flight mass spectrometer (PTR-ToF-MS). The formation of the major flavour compounds (acetaldehyde, diacetyl, acetoin, and 2-butanone) followed a sigmoidal trend described by the modified Gompertz model. The HHP treatment of milk increased significantly the volatile compound formation rate whereas it did not affect the duration of the lag phase of formation, with the exception of acetaldehyde and diacetyl formation. On the contrary, the TGase cross-linking of milk did not significantly modify the formation rate of the volatile compounds but shortened the duration of the lag phase of their formation.
 "Multi-capillary-column proton-transfer-reaction time-of-flight mass spectrometry.",
J Chromatogr A
, vol. 1316, pp. 112–118, Nov, 2013.
<p>Proton-transfer-reaction time-of-flight mass-spectrometry (PTR-TOFMS) exhibits high selectivity with a resolution of around 5000m/Δm. While isobars can be separated with this resolution, discrimination of isomeric compounds is usually not possible. The coupling of a multi-capillary column (MCC) with a PTR-TOFMS overcomes these problems as demonstrated in this paper for the ketone isomers 3-heptanone and 2-methyl-3-hexanone and for different aldehydes. Moreover, fragmentation of compounds can be studied in detail which might even improve the identification. LODs for compounds tested are in the range of low ppbv and peak positions of the respective separated substances show good repeatability (RSD of the peak positions <3.2%). Due to its special characteristics, such as isothermal operation, compact size, the MCC setup is suitable to be installed inside the instrument and the overall retention time for a complete spectrum is only a few minutes: this allows near real-time measurements in the optional MCC mode. In contrast to other methods that yield additional separation, such as the use of pre-cursor ions other than H3O(+), this method yields additional information without increasing complexity.</p>
[Cappellin2013a] "Multiclass methods in the analysis of metabolomic datasets: The example of raspberry cultivar volatile compounds detected by GC-MS and PTR-MS",
Food Research International
: Elsevier, 2013.
Multiclass sample classification and marker selection are cutting-edge problems in metabolomics. In the present study we address the classification of 14 raspberry cultivars having different levels of gray mold (Botrytis cinerea) susceptibility. We characterized raspberry cultivars by two headspace analysis methods, namely solid-phase microextraction/gas chromatography–mass spectrometry (SPME/GC–MS) and proton transfer reaction-mass spectrometry (PTR-MS). Given the high number of classes, advanced data mining methods are necessary. Random Forest (RF), Penalized Discriminant Analysis (PDA), Discriminant Partial Least Squares (dPLS) and Support Vector Machine (SVM) have been employed for cultivar classification and Random Forest-Recursive Feature Elimination (RF-RFE) has been used to perform feature selection. In particular the most important GC–MS and PTR-MS variables related to gray mold susceptibility of the selected raspberry cultivars have been investigated. Moving from GC–MS profiling to the more rapid and less invasive PTR-MS fingerprinting leads to a cultivar characterization which is still related to the corresponding Botrytis susceptibility level and therefore marker identification is still possible.