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The characteristic flavor of Coffea arabica from Yunnan is largely attributed to the primary processing treatments through affecting the VOCs accumulation. Therefore, a rapid and comprehensive detection technique is needed to accurately recognize VOCs in green coffee beans with different pretreatment methods. Hence, we conducted volatile profiles and identified nine markers of three different primary processed green coffee beans from the major production areas in Yunnan with the combined of HS-SPME-GC-MS and PTR-TOF-MS. The relationships between the chemical composition and the content of VOCs in green coffee beans were elucidated. Among the markers, palmitic acid (F3), linoleic acid (F6), α -ethylidene phenylacetaldehyde (T4), and phytane (T8) contributed to the antioxidant activity of sun-exposed green coffee beans. In conclusion, the analytical technology presented here provided a general tool for an overall and rapid understanding of a detailed volatile profiles of green coffee beans in Yunnan. • Characterizing chemical classes in different primary processed green coffee beans. • Identified nine markers in different processed green coffee beans from three origins. • Confirmed the viability of rapid recognition of markers in green coffee beans. • Possible contributors of antioxidant activity were found in VOCs and markers. [ABSTRACT FROM AUTHOR]

The postharvest fragrance quality of aromatic cut flowers is crucial, yet efficient and rapid detection methods are lacking. To develop a rapid and accurate method for evaluating the fragrance quality during the senescence of aromatic cut flowers, this study first utilized HS–SPME–GC–MS to analyze the fragrance of six Hedychium cultivars cut flowers at different stages postharvest (bud, semi-open, full bloom, and senescence), identifying 69 compounds. Multivariate statistical analysis revealed significant during full bloom, with monoterpenoids predominant in 'ZS', 'EM', 'Gaoling', and 'Jin', and benzenoids/phenylpropanoids in 'MH'. Concurrently, PTR–ToF–MS detected 68 masses consistent with GC–MS results. PLS–DA analysis identified eucalyptol, benzyl acetate, linalool, (E)- β -ocimene, methyl benzoate, and masses m/z 91.057, m/z 137.134, m/z 81.07, m/z 102.096, m/z 31.019 as potential markers for distinguishing Hedychium varieties. Additionally, PLS analysis identified masses m/z 58.078, m/z 103.076, and m/z 155.144 as predictors of agarospirol content; m/z 73.065, m/z 74.069, m/z 151.151 for eucalyptol, and m/z 27.021, m/z 31.019, m/z 41.039, m/z 43.054, m/z 55.054, m/z 57.033, m/z 70.077, m/z 72.056, m/z 88.079, m/z 91.057, m/z 92.065, and m/z 108.089 for benzyl acetate. The results provide new methods for efficient fragrance evaluation during the postharvest senescence of aromatic flower. [Display omitted] • Identified 69 VOCs in six Hedychium cut flowers using HS–SPME–GC–MS. • PTR–ToF–MS effectively evaluates fragrance changes in Hedychium cut flowers. • Combining GC–MS and PTR–ToF–MS enhances floral scent detection efficiency. [ABSTRACT FROM AUTHOR]

Insight investigation on both edible pulps and inedible parts involving inflorescence axis and shreds of Artocarpus heterophyllus Lam were carried out, a total of 98 VOCs and 201 masses were identified by the combination of HS-SPME-GC-MS and PTR-TOF-MS. Among them, according to the consistency of OAV and results of VIP > 1, p < 0.05, compounds methyl isovalerate (A2), 3-methylbutyl acetate (A5) and octanoic acid, ethyl ester (A21) were recognized as aroma markers to distinguish the pulps, shreds and inflorescence axis. Meanwhile, the inflorescence axis (IC 50 : 1.82 mg/mL) and shreds (IC 50 : 16.74 mg/mL) exhibited more excellent antioxidant potency than pulps (IC 50 : 17.43 mg/mL) in vitro. These findings validated the feasibility of coupling HS-SPME-GC-MS and PTR-TOF-MS for rapid detection of characteristic VOCs of this plant, and offered new prospect of fragrance utilization and waste management of the edible and inedible parts of A. heterophyllus fruit. [Display omitted] • HS-SPME-GC–MS and PTR-TOF-MS were coupled in identifying VOCs profiles of jackfruit. • Aroma markers to distinguish three parts of A. heterophyllus fruit were recognized. • VOCs from inedible parts of jackfruit showed potency in fragrance development. [ABSTRACT FROM AUTHOR]

The characteristics of wintertime volatile organic compounds (VOCs) in the North China Plain (NCP) region are complicated and remain obscure. VOC measurements were conducted by a proton transfer reaction time-of-flight mass spectrometer (PTR-ToF-MS) at a rural site in the NCP from November to December 2018. Uncalibrated ions measured by PTR-ToF-MS were quantified and the overall VOC compositions were investigated by combining the measurements of PTR-ToF-MS and gas chromatography-mass spectrometer/flame ionization detector (GC-MS/FID). The measurement showed that although atmospheric VOCs concentrations are often dominated by primary emissions, the secondary formation of oxygenated VOCs (OVOCs) is non-negligible in the wintertime, i.e., OVOCs accounts for 42% ± 7% in the total VOCs (151.3 ± 75.6 ppbV). We demonstrated that PTR-MS measurements for isoprene are substantially overestimated due to the interferences of cycloalkanes. The chemical changes of organic carbon in a pollution accumulation period were investigated, which suggests an essential role of fragmentation reactions for large, chemically reduced compounds during the heavy-polluted stage in wintertime pollution. The changes of emission ratios of VOCs between winter 2011 and winter 2018 in the NCP support the positive effect of "coal to gas" strategies in curbing air pollutants. The high abundances of some key species (e.g. oxygenated aromatics) indicate the strong emissions of coal combustion in wintertime of NCP. The ratio of naphthalene to C8 aromatics was proposed as a potential indicator of the influence of coal combustion on VOCs. [Display omitted] [ABSTRACT FROM AUTHOR]

• PTR-ToF-MS was used for the first time for real-time full qualitative and quantitative detection of VOCs released by 41 historical movie films on a cellulose acetate base. • Around 100 different organic ions were attributed to VOCs emitted from films. • Acetic acid, acetaldehyde, acetone, butanol, DMF, formic acid, methanol, propanoic acid dominated the VOC mixture composition. • Over 41 films, acetic acid was the most abundant VOC for 27 films reels, butanol for 6, DMF for 3, formic acid for 2, acetaldehyde for 2, acetone for 1. Cellulose acetate (CA) has been widely used since the second half of the 20th century as a transparent support for photographs and movie films in order to replace the flammable cellulose nitrate. Over time, hydrolysis occurs and the deacetylation of the CA produces acetic acid (AA), a well-known phenomenon in film archives, the so-called "vinegar syndrome". However, beside AA, other off-gassing compounds may be present, and very few studies have been devoted to their quantitative and qualitative assessment. Proton Transfer Reaction "Time-of-Flight" Mass Spectrometer (PTR-ToF-MS) combines high sensitivity with high mass resolution for real-time detection of multiple Volatile Organic Compounds (VOCs). This technique was used to evaluate the air composition from 41 films dated from the second half of the 20th century, which showed different degradation levels (ranked using A-D strips®: level 0–1.5). More than 100 VOCs were detected, and their distribution was different from one film to another. AA was the most abundant VOC in 27 film cans. In others, it was either N,N dimethylformamide (DMF), butanol, acetaldehyde, acetone or formic acid. This study shows that PTR-MS is a powerful tool to monitor in real-time, and non-invasively, objects degradation in a museum environment via the quantitative and qualitative analysis of their VOCs emissions, and that this can be used for hierarchical cluster analysis classification. [ABSTRACT FROM AUTHOR]

[Display omitted] • HSSE-GC-MS, PTR-TOF-MS, and SIFT-MS for identifying VOCs in hatching eggs. • Egg breed discrimination with high accuracy (up to 95.5%) using VOC profiles. • GC-MS and direct trace gas MS systems are complementary in identifying egg VOCs. • VOC analysis for non-destructive quality control and biological information in eggs. Over the past decade, advanced analytical techniques have been utilized to examine volatile organic compounds (VOCs) in eggs. These VOCs offer valuable insights into factors such as freshness, fertility, the presence of cracks, embryo sex, and breed. In our study, we assessed three mass spectrometry-based systems (headspace sorptive extraction gas chromatography-mass spectrometry; HSSE-GC-MS, proton transfer reaction time-of-flight-mass spectrometry; PTR-TOF-MS; and selected ion flow tube mass spectrometry; SIFT-MS) to analyze and identify VOCs present in intact hatching eggs from three distinct breeds (Dekalb white layer, Shaver brown layer, and Ross 308 broiler). The eggs were sampled on incubation days 2 and 8, to identify VOCs that distinguish breeds irrespective of incubation day. VOC measurements were conducted on 15 eggs per breed by placing them together with PDMS-coated stir bars inside inert Teflon® air sampling bags. After an accumulation period of 2 h, the headspace was analyzed using PTR-TOF-MS and SIFT-MS, while the VOCs adsorbed onto the stir bars were analyzed using GC-MS for additional compound identification. Partial least squares discriminant analysis (PLS-DA) models were constructed for breed differentiation, and variable selection was performed. As a result, 111 VOCs were identified using HSSE-GC-MS, with alcohols and esters being the most abundant. The PLS-DA models demonstrated the efficacy of breed discrimination, with the HSSE-GC-MS and the PTR-TOF-MS exhibiting the highest balanced accuracy of 95.5 % using a reduced set of 11 VOCs and 5 product ions, respectively. The SIFT-MS model had a balanced accuracy of 92.8 % with a reduced set of 11 product ions. Furthermore, complementarity was observed between HSSE-GC-MS, which primarily selected higher molecular weight VOCs, and PTR-TOF-MS and SIFT-MS. A higher correlation was found for compound abundances between the HSSE-GC-MS and the PTR-TOF-MS relative to the SIFT-MS, indicating that the PTR-TOF-MS was better suited to quantify specific compounds identified by the HSSE-GC-MS. Finally, the findings support the presence of VOCs originating from both synthetic and natural sources, highlighting the ability of the VOC analysis systems to non-destructively perform quality control and reveal differences in management practices or biological information encoded in eggs. [ABSTRACT FROM AUTHOR]

Exposure to herbivore-induced plant volatiles (HIPVs) is known to enhance the defense responses in plants. This so-called priming effect has only been marginally studied in intercropping systems. We tested whether HIPVs from cowpea, which often serves as an intercrop alongside maize, can prime herbivore-induced volatile emissions in maize. Conventional volatile collection assays and real-time mass spectrometry revealed that maize plants that were exposed to HIPVs from cowpea infested with Spodoptera exigua caterpillars emitted more than control plants when they themselves were subsequently damaged by the same pest. The enhanced emission was only evident on the first day after infestation. Maize plants that were exposed to HIPVs from cowpea infested by S. frugiperda larvae showed no priming effect and released considerably less upon S. frugiperda infestation than upon S. exigua infestation. The latter may be explained by the fact that S. frugiperda is particularly well adapted to feed on maize and is known to suppress maize HIPV emissions. Our results imply that HIPVs from cowpea, depending on the inducing insect herbivore, may strongly prime maize plants. This deserves further investigation, also in other intercropping systems, as it can have important consequences for tritrophic interactions and crop protection. [ABSTRACT FROM AUTHOR]

Fire represents a major threat to Mediterranean terrestrial ecosystems because of the high temperatures reached during summer. While massive loads of organic, inorganic compounds and particulate matter are known to be emitted into the atmosphere from forest wildfires, less is known about the emission from vegetation surrounding fires where air temperatures higher than 100 °C can be reached. Little information exists on the emission from dead vegetation accumulated as litter over forest soils, from which fires often starts. In this study, the response of litter to heatwaves generated by nearby fires was investigated under controlled conditions. Litter samples collected in a Mediterranean maquis and a Holm oak stand during summer were placed in an enclosure flushed with a continuous flow of air, the temperature of the enclosure was progressively risen to 125 °C, until some smog developed but no flaming occurred. The gas from the enclosure was analysed for the content of CO 2 , H 2 O, and volatile organic compounds (VOC) to assess the dependence of emission from the air temperature. VOC emission was continuously determined by Proton-Transfer-Reaction mass spectrometry with time of flight (PTR-TOF-MS). Data obtained were complemented with those obtained by collecting VOC on traps that were later analysed by Gas chromatography–mass spectrometry (GC-MS). Results provided useful information to understand the emission mechanism of VOC and other gases from dead vegetation present in the litter of two Mediterranean ecosystems, both dominated by evergreen vegetation species. The study demonstrated that low molecular weight VOC and aromatic hydrocarbons (arenes) produced mostly by thermal oxidation of the wood biopolymers are emitted in addition to isoprenoids typically associated to storage organs and photosynthetic pathway. Moreover, our results support parameterization of litter VOC emission processes in air quality models. [Display omitted] • CO 2 and VOC emissions from litter of two Mediterranean ecosystems were measured. • Carbon emission from litter was found to strongly increase with temperature. • Low molecular weight oxygenated compounds dominated VOC emission. • Isoprenoid emissions were higher in the Mediterranean maquis than Holm oak litter. [ABSTRACT FROM AUTHOR]

Photoionization detectors (PIDs) are low-cost sensors that are widely used for real-time volatile organic compound (VOC) monitoring in buildings. Performance assessment of PIDs is often based on reference VOC measurements derived from offline, time-integrated sample analysis. Such assessment techniques lack valuable real-time information that is needed to evaluate how PIDs track transient VOC emission events. The objective of this study is to evaluate the real-time performance of a PID in sensing indoor VOC mixtures during building disinfection events through co-location measurements with a state-of-the-art proton transfer reaction time-of-flight mass spectrometer (PTR-TOF-MS). Field measurements were conducted in a tiny house laboratory using an isobutylene-calibrated PID and a PTR-TOF-MS during the use of spray-based disinfectants. The PID and PTR-TOF-MS measurements demonstrated that chemical disinfectants are a major source of VOCs in buildings, with the latter revealing the presence of a large diversity of VOCs. In general, the PID was successful in identifying VOC emission events during the application of the disinfectants. Thus, PIDs may be suitable for integration with building automation systems for ventilation control. The PID response was much less than the PTR-TOF-MS response, suggesting that the PID is not efficiently detecting many components of the emitted VOC mixtures. The PID performed best for alcohol-based disinfectants, moderately well for lactic acid- and botanical-based disinfectants, and poorly for disinfectants featuring peracetic and acetic acid. Detailed correlation analysis between the PID and PTR-TOF-MS responses provides a basis for improving the reliability of PIDs in estimating VOC concentrations through application of product-specific correction factors. • Indoor field evaluation of a low-cost VOC sensor with a state-of-the-art PTR-TOF-MS. • Real-time performance assessment of a PID during building disinfection events. • PID performance is dependent on the disinfectant product used and their emitted VOCs. • PIDs may be suitable for integration with building automation systems for ventilation control. [ABSTRACT FROM AUTHOR]

Abstract In this study we examine the application of a factor analysis technique for datasets recorded by the chemical ionization instrument Proton Transfer Reaction - Time-of-Flight - Mass Spectrometer (PTR-ToF-MS). Numerical simulations were carried out to test and optimize the performance of the factorization method Multivariate Curve Resolution - Alternating Least Squares (MCR-ALS). The simulations demonstrated that the choice of initial estimates for the factor analysis are crucial for the outcome of the factorization. For this purpose we describe a new method based on the Pearson correlation coefficient which, compared to the other tested methods, yields the best factorization results. Overlapping contributions of different substances to a certain mass bin and large uncertainties in the data deteriorate the performance of the factor analysis. The deconvolution technique was also applied to data obtained with a PTR-ToF-MS employed at a smog chamber. The response from single substances (fragmentation patterns) such as α-pinene, α-pinene oxide and pinonaldehyde as well as a more complex experiment involving the ozonolysis of α-pinene are investigated. For the single substances, the factorization method points to the presence of impurities which could be differentiated from the masses affiliated with the actual substances. The α-pinene ozonolysis experiment was analysed with the factorization technique and yielded four factors, one representing the decay of the reactant and three different products. The matrix factorization technique appeared to be a valuable tool allowing for a detailed analysis of complex mass spectra without the need of any prior information. Highlights • Investigation of the suitability of factor analysis to interpret PTR-ToF-MS datasets. • Factor analysis performance tested on chemical model systems. • Measured fragmentation patterns of α-pinene, α-pinene oxide and pinonaldehyde. • Factor analysis of a smog chamber dark α-pinene ozonolysis experiment at 293 K. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Reactions of 9 D-labeled volatile compounds with H 3 O+ in PTR- MS were investigated. • Exothermic proton transfer was the dominant ionization mechanism. • Deuterium/hydrogen isotope exchange reactions with water in drift tube were noted. • D/H exchange led to generation of various isotopologue ions and complex spectra. Abstract Product ion distributions resulting from the primary reactions of H 3 O+ with nine D-labeled volatile organic compounds and the subsequent sequential reactions with H 2 O have been determined using a Proton Transfer Reaction Time of Flight Mass Spectrometer (PTR-TOF 8000 (IONICON Analytik GmbH)) at various reduced electric field (E/N) values ranging from 80 up to 150 Td and for two different absolute humidity levels of air sample < 0.1% and 5%. The specific D-labeled compounds used in this study are acetone-d 6 , toluene-d 8 , benzene-d 6 , ethanol-d (C 2 H 5 OD), ethanol-d 2 (CH 3 CD 2 OH), ethanol-d 6 , 2-propanol-d 8 , 2-propanol-d 3 (CD 3 CH(OH)CH 3), and isoprene-d 5 (CH 2 CHC(CD 2)CD 3). With the exception of the two 2-propanol compounds, non-dissociative proton transfer is the dominant primary reaction pathway. For 2-propanol-d 8 and 2-propanol-d 3 the major primary reaction channel involved is dissociative proton transfer. However, unlike their undeuterated counterparts, the primary product ions undergo subsequent deuterium/hydrogen isotope exchange reactions with the ever present water in the drift tube, the extent of which of course depends on the humidity within that tube. This exchange leads to the generation of various isotopologue product ions, the product ion branching percentages of which are also dependent on the humidity in the drift tube. This results in complex mass spectra and the distribution of product ions leads to issues of reduced sensitivity and accuracy. However, the effect of D/H exchange considerably varies between the compounds under study. In the case of acetone-d 6 it is very weak (< 1%), because the exchange process is not facile when the deuterium is in the methyl functional group. In comparison, the H 3 O+/ benzene-d 6 (C 6 D 6) reaction and sequential reactions with water result in the production of the isotopologue ions C 6 D n (H 7-n)+ (where n = 0–6). Changing the value of E/N and/or the humidity in the drift tube considerably affects the amount of the isotope exchange reactions and hence the resulting sequential product ion distributions. An important conclusion of the findings from this work is that care must be taken in the choice of an exogenous deuterated compound for use in breath pharmacokinetic studies using proton transfer reaction mass spectrometry; otherwise the resulting D/H exchange processes impose interpretative problems. [ABSTRACT FROM AUTHOR]

The characterization of 72 Italian honey samples from 8 botanical varieties was carried out by a comprehensive approach exploiting data fusion of IR, NIR and Raman spectroscopies, Proton Transfer Reaction – Time of Flight – Mass Spectrometry (PTR-MS) and electronic nose. High-, mid- and low-level data fusion approaches were tested to verify if the combination of several analytical sources can improve the classification ability of honeys from different botanical origins. Classification was performed on the fused data by Partial Least Squares – Discriminant Analysis; a strict validation protocol was used to estimate the predictive performances of the models. The best results were obtained with high-level data fusion combining Raman and NIR spectroscopy and PTR-MS, with classification performances better than those obtained on single analytical sources (accuracy of 99% and 100% on test and training samples respectively). The combination of just three analytical sources assures a limited time of analysis. [ABSTRACT FROM AUTHOR]

Volatile organic compounds (VOCs), which are ubiquitous pollutants in the urban and regional atmosphere, promote the formation of ozone (O 3) and secondary organic aerosols, thereby significantly affecting the air quality and human health. The ambient VOCs at a coastal suburban site in Hong Kong were continuously measured using proton-transfer-reaction time-of-flight mass spectrometry (PTR-ToF-MS) from November 2020 to December 2020. 83 VOC species, including 23 C x H y , 53 C x H y O 1-3 , and 7 nitrogen-containing species, were measured during the campaign, with a mean concentration of 36.75 ppb. Oxygenated VOCs (OVOCs) accounted for most (77.4%) of the measured species, including C x H y O 1 (50.7%) and C x H y O 2 (25.1%). The measured VOC species exhibited distinct temporal and diurnal variations. High concentrations of isoprene and OVOCs were measured in autumn with more active photochemistry, whereas large evening peaks of aromatics from local and regional primary emissions were prominent in winter. The OH reactivity and O 3 formation potential (OFP) of key precursors were quantified. OVOCs contributed about half of the total OH reactivity and OFP, followed by alkenes and aromatics, and the contribution of aromatics increased significantly in winter. The potential source contribution function was used to investigate the potential source regions associated with high VOC concentrations. Through positive matrix factorization analysis, six major sources were identified based on fingerprint molecules. The contributions of biogenic sources and secondary formation to the observed species were notable in late autumn, whereas vehicle emissions and solid fuel combustion had higher contributions in winter. The findings highlight the important role of OVOCs in photochemical pollution and provide valuable insights for the development of effective pollution control strategies. [Display omitted] • Comprehensive characterization of 83 volatile organic compounds in Hong Kong. • Abundant OVOCs contribute significantly to OH reactivity and ozone formation. • Key potential sources of complex VOCs and OVOCs were identified and quantified. • Regional transport, vehicle emission and photochemistry drive the VOC variability. [ABSTRACT FROM AUTHOR]

Several analytical techniques, i.e. Near Infrared (NIR) and Mid-Infrared (MIR) spectroscopy, Hyper Spectral Imaging (HSI), Gas Chromatography coupled to Mass Spectrometry (GC-MS) and Proton-transfer Reaction Time-of-Flight Mass spectrometry (PTR-TOF-MS), combined with chemometrics, are examined to evaluate their potential for solving food authenticity questions on the case of rice. In total, 237 rice samples were analyzed in this study to examine origin and variety assessment and sourced from producing countries (Italy, Spain, Vietnam, Pakistan and Thailand). The Gaussian Process Latent Variable Model (GP-LVM) was applied as technique to obtain a meaningful compressed representation of the data in a two-dimensional space followed by a classification with a nearest neighbour algorithm. What concerns the origin assessment, GC-MS results score good across all countries, resulting in the most accurate method, with prediction rates ranging from 86% to 94%. Data fusion experiments of combination of GC-MS with NIR, or GC-MS with HSI resulted in prediction rates on origin assessment of more than 90%. Variety assessment was performed with these analytical techniques. Using single techniques, HSI achieved prediction values above 90% for all classes (96%–99%). For data fusion experiments of variety assessment combining GC-MS and NIR all prediction values were equal or higher than 92%; for GC-MS combined with HSI, prediction values were all 98%. The presented methodology can be successfully used for the authentication of rice. • New methods to control the authenticity of rice were developed. • Successful origin and variety assessment of rice. • NIR, MIR, GC-MS, PTR-TOF-MS and hyperspectral imaging, combined with chemometrics. • Successful mid-level data fusion experiments. • Highest prediction values obtained for GC-MS (origin) and HSI (variety). [ABSTRACT FROM AUTHOR]

Quantitative proton-transfer-reaction mass spectrometer (PTR-MS) measurements of ambient volatile organic compounds (VOCs) require proper calibration procedures. In particular, compound product ion distribution and humidity-dependent responses must be characterized. In this study, we generated twelve gas-phase terpenoid standards using a dynamic dilution system to calibrate the PTR-MS with time-of-flight mass spectrometer (PTR-ToF-MS): six monoterpenes, two monoterpene derivatives, and four sesquiterpenes. The humidity-dependent response was characterized for three terpenoid compounds to compare different molecular structures: α-pinene, δ-limonene, and longifolene. We provide the first comprehensive summary of PTR-ToF-MS product ion distributions for twelve common biogenic volatile organic compounds using two different reduced electric field (E/N) values, 80 Td and 130 Td. Results demonstrated that neglecting to correct for individual product ion distributions of different terpenoid isomers can result in an error of up to 26% for reported mixing ratios. δ-Limonene and longifolene exhibited a small humidity-dependent response in the PTR-ToF-MS, but this did not contribute significantly to the overall measurement error. These results will improve quantification of commonly-measured biogenic volatile organic compound emissions and chemistry in the atmosphere. [ABSTRACT FROM AUTHOR]

This work was performed to evaluate the possible application of PTR-ToF-MS technique in distinguishing between Coffea arabica (Arabica) and Coffea canephora var. robusta (Robusta) commercial stocks in each step of the processing chain (green beans, roasted beans, ground coffee, brews). volatile organic compounds (VOC) spectra from coffee samples of 7 Arabica and 6 Robusta commercial stocks were recorded and submitted to multivariate statistical analysis. Results clearly showed that, in each stage of the coffee processing, the volatile composition of coffee is highly influenced by the species. Actually, with the exception of green beans, PTR-ToF-MS technique was able to correctly recognize Arabica and Robusta samples. Particularly, among 134 tentatively identified VOCs, some masses (16 for roasted coffee, 12 for ground coffee and 12 for brewed coffee) were found to significantly discriminate the two species. Therefore, headspace VOC analyses was showed to represent a valuable tool to distinguish between Arabica and Robusta. [ABSTRACT FROM AUTHOR]

One of the most common volatile organic compounds (VOCs) group is monoterpenes. Monoterpenes share the molecular formula C 10 H 16 , they are usually cyclic and have a pleasant smell. The most common monoterpenes are limonene (present in citrus fruits) and α-pinene (present in conifers’ resin). Different monoterpenes have different chemical, biological and ecological properties thus it is experimentally very important to be able to differentiate between them in real time. Real time instruments such as Proton Transfer Reaction-Time of Flight-Mass Spectrometry (PTR-ToF-MS), offer a real time solution for monoterpene measurement but at the cost of selectivity resulting in all monoterpenes being seen at the same m / z . In this work we used Selective Reagent Ion-Time of Flight-Mass Spectrometry (SRI/PTR-ToF-MS) in order to explore the differences in ion branching when different ionizations (H 3 O + , NO + and O 2 + ) and different drift tube reduced field energies (E/N) were used. We report a comprehensive ion library with many unique features, characteristic for individual monoterpenes. [ABSTRACT FROM AUTHOR]

This paper presents the sources and characteristics of ambient volatile organic compounds (VOCs) measured using PTR-TOF-MS instrument in a metropolitan city of India during winter to summer transition period. Mixing ratios of VOCs exhibited strong diurnal, day-to-day and episodic variations. Methanol was the most dominant species with monthly mean values of 18–22 pbbv. The emission ratios of VOCs relative to benzene calculated from nighttime data were used to estimate the relative contributions of vehicle exhaust and other sources. The increasing daytime ratios of oxygenated-VOCs (OVOCs)/benzene and isoprene/benzene from February to March indicates increasing contribution of photo-oxidation and biogenic sources. Daytime fractions of acetone (18%), acetaldehyde (15%) and isoprene (4.5%) to the sum of measured VOCs in March were higher than those in February. Variations of VOCs at lower temperatures (<25 °C) were predominantly controlled by anthropogenic sources. At high temperatures, particularly in the range of 32–40 °C during March, levels of OVOCs and isoprene were influenced by biogenic emissions. The emissions of OVOCs from vehicle exhaust were estimated to be smaller (20–40%) than those from other sources. The contributions of biogenic and secondary sources to OVOCs and isoprene increased by 10–15% from winter to summer. This study provides evidence that the winter-to-summer transition has an impact on sources and composition of VOCs in tropical urban areas. [ABSTRACT FROM AUTHOR]

This study investigated the diel emission of volatile organic compounds (VOCs) from intact apple ( Malus x domestica Borkh., cv. Golden Delicious) and grape ( Vitis vinifera L., cv. Pinot Noir) foliage. Volatiles were monitored continuously for 48 h by proton transfer reaction - time of flight - mass spectrometry (PTR-ToF-MS). In addition, volatiles were collected by closed-loop-stripping-analysis (CLSA) and characterized by gas chromatography-mass spectrometry (GC-MS) after 1 h and again 24 and 48 h later. Fourteen and ten volatiles were characterized by GC-MS in apple and grape, respectively. The majority of these were terpenes, followed by green leaf volatiles, and aromatic compounds. The PTR-ToF-MS identified 10 additional compounds and established their diel emission rhythms. The most abundant volatiles displaying a diel rhythm included methanol and dimethyl sulfide in both plants, acetone in grape, and mono-, homo- and sesquiterpenes in apple. The majority of volatiles were released from both plants during the photophase; whereas methanol, CO 2 , methyl-butenol and benzeneacetaldehyde were released at significantly higher levels during the scotophase. Acetaldehyde, ethanol, and some green leaf volatiles showed distinct emission bursts in both plants following the daily light switch-off. These new results obtained with a combined analytical approach broaden our understanding of the rhythms of constitutive volatile release from two important horticultural crops. In particular, diel emission of sulfur and nitrogen-containing volatiles are reported here for the first time in these two crops. [ABSTRACT FROM AUTHOR]

Respiratory absorption factors (AFs) are essential parameters in the evaluation of human health risks from toxic volatile organic compounds (VOCs) in ambient air. A method for the real time monitoring of VOCs in inhaled and exhaled air by proton transfer reaction time-of-flight mass spectrometry (PTR-TOF-MS) has been developed to permit the calculation of respiratory AFs of VOCs. Isoprene was found to be a better breath tracer than O 2 , CO 2 , humidity, or acetone for distinguishing between the expiratory and inspiratory phases, and a homemade online breath sampling device with a buffer tube was used to optimize signal peak shapes. Preliminary tests with seven subjects exposed to aromatic hydrocarbons in an indoor environment revealed mean respiratory AFs of 55.0%, 55.9%, and 66.9% for benzene, toluene, and C8-aromatics (ethylbenzene and xylenes), respectively. These AFs were lower than the values of 90% or 100% used in previous studies when assessing the health risks of inhalation exposure to hazardous VOCs. The mean respiratory AFs of benzene, toluene and C8-aromatics were 66.5%, 70.2% and 82.3% for the three female subjects; they were noticeably much higher than that of 46.4%, 45.2% and 55.3%, respectively, for the four male subjects. [ABSTRACT FROM AUTHOR]

In-vitro and in-vivo flavour release from 21 different apple cultivars was studied using proton transfer reaction time-of-flight mass spectrometry (PTR-ToF-MS) with a focus on the relationship between texture and volatile organic compound (VOC) emission. Generally, firm-juicy cultivars had a shorter time to first swallow ( T swal ) and a higher number of swallows ( N swal ), while softer-mealy cultivars had a longer T swal and a lower N swal. Firm-juicy cultivars containing high VOC concentrations had a short time to maximum intensity ( T max ) owing to a shorter T swal and a higher N swal as juice was released during mastication. Swallowing increased VOC flow through the nasal cavity. These results differ from previous flavour release studies with gel/gel-like model systems as juiciness/release of fluids is not a factor in such matrices. The current study, therefore, highlights the benefits of using in-vivo analysis to gain a better understanding of flavour release in real food products. [ABSTRACT FROM AUTHOR]

Organic Fraction of Municipal Solid Waste was adopted to produce biogas to feed a SOFC generator. Several experimental tests were accomplished on the trace compounds monitoring with PTR-ToF-MS instrument. The main organic compounds detected with the instrument were: sulfurs, terpenes, carboxyls, carbonyls and siloxanes. Coupled to these tests SOFC experiments were accomplished investigating the slipover influence from sorbent materials of sulfurs, chlorines and siloxanes. Limiting factors were evidenced from sulfur, chlorine and siloxane impact on SOFC using an electrochemical impedance spectroscopy (EIS). Tolerable concentration level of single organic compounds appears to be below 1 ppm(v) for H2S and no concentration is tolerated for siloxanes. [ABSTRACT FROM AUTHOR]

[Display omitted] • New methods to control the authenticity of oregano were developed. • Successful origin and variety assessment of oregano. • Detection of 10 % adulteration in oregano with myrtle, sumac, olive and cistus. • Batch to batch control of oregano possible with several analytical techniques. • NIR, MIR, GC–MS, PTR-TOF-MS and hyperspectral imaging, combined with chemometrics. Several analytical techniques, i.e. spectroscopic techniques as Near Infrared (NIR) and Mid-Infrared (MIR), Hyper Spectral Imaging (HSI), Gas Chromatography coupled to Mass Spectrometry (GC–MS) and Proton-transfer Reaction Time-of-Flight Mass spectrometry (PTR-TOF-MS), combined with chemometrics, are examined to evaluate their potential to solve different food authenticity questions on the case of oregano. In total, 102 oregano samples from one harvest season were analyzed for origin and variety assessment, 159 samples for adulteration-assessment and 72 samples for batch-to-batch control. The Gaussian Process Latent Variable Model (GP-LVM) was applied as technique to obtain a reduced two-dimensional space. A Random Forest Regression algorithm was used as regression model for the adulteration assessment. Prediction rates of more than 89% could be achieved for origin assessment. For variety assessment, prediction rates of more than 78% could be obtained. Batch-to-batch control could be successfully performed with NIR and PTR-TOF-MS. Detection of adulteration could be successfully performed from 10% on with HSI, NIR and PTR-TOF-MS. [ABSTRACT FROM AUTHOR]

The feasibility of reusing waste materials as an inexpensive sorbent to remove volatile organic compounds from gaseous waste streams has been demonstrated. Ashes from wood-chips were tested as sorbent materials for VOCs removal with a PTR-ToF-MS instrument. Both scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX) and BET analysis were used to identify the structural characteristics, elemental composition and surface area of the tested ashes respectively. Most of the tentatively identified compounds were less strongly adsorbed by wet ash: thiols, siloxanes, carbonyl compounds and terpenes. Hydrogen sulfide and alcohols show improving removal performance in wet conditions. These results are related to the water solubility properties. Siloxanes were tentatively identified and monitored with PTR-ToF-MS. This demonstrates how this instrument is a suitable tool for simultaneously providing a multitude of analysis for rapid in situ monitoring of fuel contaminants. Considering the low cost, and the recycling of environmental pollutants, wood ashes are a possible choice for VOCs removal from biogas. [ABSTRACT FROM AUTHOR]

PTR-ToF-MS has been previously used to analyse the headspace of wine, but it is not fully exploited in the field due to problems related to the high ethanol concentration. In the case of alcoholic fermentation during bread-making, we have recently proposed improvements to the method by introducing argon in the system in order to reduce fragmentation and formation of ethanol clusters. In this study, we optimize the experimental setup in the case of wine by (i) boosting the sampling protocol (sample headspace flushing and incubation); (ii) determining the optimal E / N value while using argon as carrier gas and (iii) proving that the optimized protocol reduces the effect of ethanol. The new protocol has been verified to discriminate eight French wines coming from three different regions (Gers, Gironde, Languedoc) and, in order to assess the applicability of the method in a relevant problem of oenological interest, we also tested it on a set of samples consisting of a red wine fermented with two different commercial preparations of Oenococcus oeni . Using principal component analysis of selected m / z signals, differentiation among wines from different geographical origin was achievable. Samples corresponding to the reference wine and to wines inoculated with two different commercial preparations were clearly separated. Intriguingly, our approach suggests the selective degradation of volatile organic compounds by O. oeni in wine as new possible feature of malolactic starter cultures in wine. [ABSTRACT FROM AUTHOR]

Honey, in particular monofloral varieties, is a valuable commodity. Here, we present proton transfer reaction-time of flight-mass spectrometry, PTR-ToF-MS, coupled to chemometrics as a successful tool in the classification of monofloral honeys, which should serve in fraud protection against mispresentation of the floral origin of honey. We analyzed 7 different honey varieties from citrus, chestnut, sunflower, honeydew, robinia, rhododendron and linden tree, in total 70 different honey samples and a total of 206 measurements. Only subtle differences in the profiles of the volatile organic compounds (VOCs) in the headspace of the different honeys could be found. Nevertheless, it was possible to successfully apply 6 different classification methods with a total correct assignment of 81–99% in the internal validation sets. The most successful methods were stepwise linear discriminant analysis (LDA) and probabilistic neural network (PNN), giving total correct assignments in the external validation sets of 100 and 90%, respectively. Clearly, PTR-ToF-MS/chemometrics is a powerful tool in honey classification. [ABSTRACT FROM AUTHOR]

Most plants produce and emit a wide blend of biogenic volatile organic compounds (BVOCs). Among them, many isoprenoids exhibit a high atmospheric reactivity toward OH radicals and ozone. In the last few years, Proton Transfer Reaction–Mass Spectrometry (PTR–MS) has been widely used in both field and laboratory determination of BVOCs, complementing the traditional methods using gas chromatography–mass spectrometry (GC–MS) for their identification in air and emission sources. This technical note reports a number of experiments carried out with a PTR- (Time-of-Flight) TOF-MS equipped with a prototype fast-GC system, allowing a fast separation of those isobaric isoprenoid compounds that cannot be identified by a direct PTR-TOF-MS analysis. The potential of this fast-GC system to adequately complement the information provided by PTR-TOF-MS was investigated by using the BVOC emissions of Quercus ilex and Eucalyptus camaldulensis as reliable testing systems, due to the different blend of isoprenoid compounds emitted and the different dependence of their emission from environmental parameters. While the oak species is a strong monoterpene emitter, the eucalyptus used is one of the few plant species emitting both isoprene and monoterpenes. The performances provided by the type of fast-GC used in the new PTR-TOF-MS instrument were also compared with those afforded by conventional GC–MS methods. The results obtained in this investigation showed that this new instrument is indeed a quick and handy tool to determine the contribution of isoprene and eucalyptol to m / z 69.070 and monoterpenes and ( Z )-3-hexenal to m / z 81.070, integrating well the on-line information provided by PTR-TOF-MS. However, some limitations emerged in the instrument as compared to traditional GC–MS, which can only be solved by implementing the injection and separation processes. [ABSTRACT FROM AUTHOR]

Immunocastration in pigs has been proposed as a cruelty-free alternative to surgical castration. In this work the effect of immune-spaying of female pigs on the volatile compound profile of Iberian dry-cured products was evaluated. The head-space volatile compound of dry-cured shoulders and loins from surgically spayed, immune-spayed and entire Iberian × Duroc females was characterized by proton transfer reaction-time of flight-mass spectrometry. It was not possible to identify a significant effect of the castration modality on dry-cured shoulders, probably because of the heterogeneity of samples. Contrarily, Principal Component Analysis of dry-cured loins indicates a better homogeneity of samples and the separation of loins from surgically spayed and immune-spayed females. Some mass peaks tentatively identified as important flavor compounds in dry-cured products, 3-methylbutanal, 2,3-butanedione and 3-methylbutanoic acid, were significantly higher in the immune-spayed females. Therefore, immune-spaying seems to have a negligible effect on the volatile compound profile of dry-cured shoulders, whereas it could affect the VOC profile in the case of dry-cured loins. [ABSTRACT FROM AUTHOR]

The organic contamination has been recently considered as the most important problem for the photolithography world in the semiconductor industry, especially when the photolithographic methods moved from 130 nm node to 32 nm node. One of the most common organic compounds found in photolithography areas of the clean room is Trimethylsilanol (TMS), which can adsorb on the optical lenses forming a thin molecular layer, hence causing damages. Salt crystal formation is another potential threat for the optical devices. In the clean rooms, this salt is produced by a light-induced reaction between ammonia and an acid. In the context of semiconductor industry, the involved acid is usually the acetic acid produced by hydrolysis from propylene glycol methyl ether acetate (PGMEA), a commonly used organic compound in the photolithography. Here, we present an innovative analytical method using a state-of-the-art proton-transfer reaction–time-of-flight–mass spectrometer (PTR–ToF–MS) for on-line and continuous survey of volatile organic compounds (VOCs) with an emphasis on TMS and PGMEA. The effect of relative humidity on the detection and fragmentation of these organic compounds was assessed. The new analytical method is operated in a real life clean room environment and the results were compared with those obtained with off-line measurements using automated thermal desorber–gas chromatography–mass spectrometry (ATD–GC–MS) as reference method. The contamination sources were detected and identified, which is of paramount importance for the microelectronic fabrication plant. The trapping efficiency of the chemical filters used for AMCs filtration in the photolithography zone was determined. [ABSTRACT FROM AUTHOR]

Floral scent profiles play crucial role in the ornamental values of cut flowers, and efficient floral scent profiling acquisition is a critical premise for quality assessment and genetic improvement of fragrant cut flowers. Despite the fact that cross breeding is an effective method for improving the fragrance of cut flowers, less focus has been paid on floral scent evaluation in cross populations due to the complexity of fragrance phenotype detection. In the current study, floral scent profile of Hedychium coronarium 'ZS', H. 'Jin' and their 110F 1 hybrid cultivars were evaluated. Headspace solid phase microextraction- gas chromatography-mass spectrometry (HS–SPME–GC–MS) identified 33 volatile organic compounds (VOCs), including 15 monoterpenoids, 7 sesquiterpenoids, 9 phenylpropanoids, 1 fatty acid derivative, and 1 other, while proton transfer reaction-time of flight-mass spectrometry (PTR–ToF–MS) detected 68 masses. Correlation analysis indicated that β -myrcene, α -terpinene, eucalyptol, (E)- β -ocimene, cyclopentene, 3-isopropenyl-5, 5-, allo-ocimene, indole, isoamyl benzoate, (E)- β -famesene, m / z 74.069 and m / z 118.069 played an important role in sensory concentration of Hedychium flowers fragrance. Furthermore, partial least squares (PLS) analysis of VOCs and masses revealed that 44 masses were highly sensitive to 21 VOCs (8 monoterpenoids, 6 sesquiterpenoids, 5 benzenoids/phenylpropanoids, 1 fatty acid derivative, and indole). Overall, the data showed that two mass spectrometric methodologies were highly complementary, revealing a novel and dynamic perspective on volatile complex diversity of Hedychium F 1 hybrid population cut flowers. • Floral scent profile of Hedychium F 1 hybrid population cut flowers were detected by HS–SPME–GC–MS and PTR–ToF–MS. • Floral scent of Hedychium F 1 hybrids cut flowers have obvious changes. • Multivariant analysis confirmed the complementarity and correspondence between chromatographic and direct injection method in floral scent determination. [ABSTRACT FROM AUTHOR]

For the first time, emission/deposition fluxes of volatile organic compounds (VOCs) and H 2 S from a historic closed landfill site in Southern Italy were determined by Eddy Covariance (EC) using Proton Transfer Reaction Time-of-Flight Mass Spectrometry (PTR-TOF-MS). This was done in two field campaigns of one week performed in July and October 2016, where fluxes of CO 2 and CH 4 were also measured. Many compounds not previously identified in the biogas were detected by PTR-TOF-MS, but only in July some of them produced positive fluxes exceeding the flux limit of detection. Methanol was the most emitted compound with an average flux of 44.20 ± 4.28 μg m−2 h−1, followed by toluene with a mean flux of 18.97 ± 2.47 μg m−2 h−1. Toluene fluxes were 10 times higher than those of benzene, fitting rather well with values previously measured in the biogas. VOCs emission fluxes of monoterpenes and highly reactive arenes did not reflect, however, the biogas composition. This, combined with tiny emissions of VOC oxidation products, suggests that landfill emissions underwent some photochemical degradation before being dispersed in the atmospheric boundary layer (ABL). Deposition fluxes of some VOCs emitted from the sea was also observed in July. No relevant VOC fluxes were instead measured in October, suggesting that temperature was the variable controlling most landfill emission. Albeit small, summer landfill emissions from the investigated site can have an impact on the population living nearby, because they contain or still generate compounds that causing nuisance. [Display omitted] • VOCs from landfills by Proton Transfer Reaction Time-of-Flight Mass Spectrometer. • Eddy Covariance turbulent fluxes of VOCs, CO 2 and CH 4 from landfills. • Summer fluxes of VOCs and H 2 S not previously identified in the biogas were measured. • No relevant fluxes of VOCs and H 2 S were measured in autumn. • Methanol was the most emitted compound followed by toluene. [ABSTRACT FROM AUTHOR]

Volatile organic compounds (VOCs) are ubiquitous atmospheric constituents and play important roles in tropospheric photochemistry. The real-time chemical characterization of VOCs was carried out in this study using the proton-transfer-reaction time-of-flight mass spectrometer (PTR-TOF-MS) at an urban site of Delhi for the complete year of 2019. The average concentrations of total VOCs ranging from m/z 31.02 to 181.12 were 131.3 ± 96, 78.7 ± 47.3, 151.2 ± 83.2, 199.6 ± 101.2 ppbv in the winter, summer, monsoon, and post-monsoon seasons, respectively. The positive matrix factorization (PMF) receptor model on an advanced ME-2 engine was used to perform source apportionment analysis. This analysis reveals two traffic-related factors, two solid-fuel combustion factors, two secondary VOC factors, one biogenic, and one solvent-use factor depending upon the season. The traffic-related emissions mainly comprised of aromatics and simple non-aromatics, contributed about 31% (∼one-third) of the total VOCs measured over the study period. Solid fuel combustion factors consisting of phenols, furans, and nitrogen-containing compounds contributed about 28%, while Secondary VOCs contributed about 31% cumulatively over the study period. The contributions of biogenic sources were significant only during the summer and monsoon seasons. A local source near the sampling site was identified as a solvent-use factor, mainly comprised of ethyl acetate due to the renovation work near the sampling site during monsoon and post-monsoon season. The difference in the profile of primary sources was influenced by the local emissions and regional transport of air masses. Meteorological conditions and planetary boundary layer highly influence the formation of secondary VOCs. [Display omitted] • Real-time measurements of NMVOCs during different seasons in Delhi. • Highest levels of NMVOCs are present during post-monsoon season. • Source apportionment of NMVOCs using ME-2 multilinear engine. • Traffic related emissions are present throughout all seasons. • Biogenic sources of VOCs are dominant during summer and monsoon season. [ABSTRACT FROM AUTHOR]

This study is based on the high mass and time-resolved measurements of seven VOCs using a PTR-TOF-MS instrument at an urban site of India during winter 2013. Daily levels of OVOCs and aromatics were in the ranges of 3.5–37 ppbv and 0.85–23 ppbv, respectively with OVOCs accounted for up to 80% of total measured VOCs. The impact of long-range transport from the polluted Indo-Gangetic Plain and clean Thar desert was observed during the episodes of high and low VOCs, respectively. VOCs exhibited strong diurnal variations with peaks during morning and evening hours and lowest in the afternoon. Relatively elevated aromatics during evening hours coincided with the lowest-OVOCs indicating influence of fresh vehicular emissions. Emission ratios of isoprene and OVOCs with respect to benzene followed the diurnal cycles of temperature and solar flux indicating role of biogenic and photochemical processes, respectively. Correlation study of VOCs with benzene suggests major contribution from anthropogenic and also from biogenic and secondary sources to some extent. The higher emission ratios of ∆methanol/∆acetonitrile correspond to the episodes of long-range transport from biomass burning sources located in the Indo-Gangetic Plain (IGP). In addition to the pattern of emission, the diurnal and day-to-day variations of VOCs were influenced by the local meteorological conditions and depth of planetary boundary layer (PBL). [ABSTRACT FROM AUTHOR]

Green leaf volatiles (GLVs) emitted by plants after stress or damage induction are a major part of biogenic volatile organic compounds (BVOCs). Proton transfer reaction time-of-flight mass spectrometry (PTR-TOF-MS) is a high-resolution and sensitive technique for in situ GLV analyses, while its performance is dramatically influenced by humidity, electric field, etc. In this study the influence of gas humidity and the effect of reduced field (E/N) were examined in addition to measuring calibration curves for the GLVs. Calibration curves measured for seven of the GLVs in dry air were linear, with sensitivities ranging from 5 to 10 ncps/ppbv (normalized counts per second/parts per billion by volume). The sensitivities for most GLV analyses were found to increase by between 20% and 35% when the humidity of the sample gas was raised from 0% to 70% relative humidity (RH) at 21°C, with the exception of (E)-2-hexenol. Product ion branching ratios were also affected by humidity, with the relative abundance of the protonated molecular ions and higher mass fragment ions increasing with humidity. The effect of reduced field (E/N) on the fragmentation of GLVs was examined in the drift tube of the PTR-TOF-MS. The structurally similar GLVs are acutely susceptible to fragmentation following ionization and the fragmentation patterns are highly dependent on E/N. Overall the measured fragmentation patterns contain sufficient information to permit at least partial separation and identification of the isomeric GLVs by looking at differences in their fragmentation patterns at high and low E/N. [ABSTRACT FROM AUTHOR]

Combustion of solid and liquid fuels is the largest source of potentially toxic volatile organic compounds (VOCs), which can strongly affect health and the physical and chemical properties of the atmosphere. Among combustion processes, biomass burning is one of the largest at global scale. We used a Proton Transfer Reaction “Time-of-Flight” Mass Spectrometer (PTR-TOF-MS), which couples high sensitivity with high mass resolution, for real-time detection of multiple VOCs emitted by burned hay and straw in a barn located near our measuring station. We detected 132 different organic ions directly attributable to VOCs emitted from the fire. Methanol, acetaldehyde, acetone, methyl vinyl ether (MVE), acetic acid and glycolaldehyde dominated the VOC mixture composition. The time-course of the 25 most abundant VOCs, representing ∼85% of the whole mixture of VOCs, was associated with that of carbon monoxide (CO), carbon dioxide (CO 2 ) and methane (CH 4 ) emissions. The strong linear relationship between the concentrations of pyrogenic VOC and of a reference species (i.e. CO) allowed us to compile a list of emission ratios (ERs) and emission factors (EFs), but values of ER (and EF) were overestimated due to the limited mixing of the gases under the stable (non-turbulent) nocturnal conditions. In addition to the 25 most abundant VOCs, chemical formula and concentrations of the residual, less abundant VOCs in the emitted mixture were also estimated by PTR-TOF-MS. Furthermore, the evolution of the complex combustion process was described on the basis of the diverse types of pyrogenic gases recorded. [ABSTRACT FROM AUTHOR]

Coeliac disease (CD) is a common chronic inflammatory disorder of the small bowel induced in genetically susceptible people by the exposure to gliadin gluten. Even though several tests are available to assist the diagnosis, CD remains a biopsy-defined disorder, thus any non-invasive or less invasive diagnostic tool may be beneficial. The analysis of volatile metabolites in exhaled breath, given its non-invasive nature, is particularly promising as a screening tool of disease in symptomatic or non-symptomatic patients. In this preliminary study the proton transfer reaction time of flight mass spectrometry coupled to a buffered end-tidal on-line sampler to investigate metabolites in the exhaled breath of patients affected by coeliac disease under a gluten free diet was applied. Both H3O+ or NO+ were used as precursor ions. In our investigation no differences were found in the exhaled breath of CD patients compared to healthy controls. In this study, 33 subjects were enrolled: 16 patients with CD, all adhering a gluten free diet, and 17 healthy controls. CD patients did not show any symptom of the disease at the time of breath analysis; thus the absence of discrimination from healthy controls was not surprising. [ABSTRACT FROM AUTHOR]

Proton transfer reaction-mass spectrometry (PTR-MS) has successfully been applied to a wide variety of food matrices, nevertheless the reports about the use of PTR-MS in the analysis of alcoholic beverages remain anecdotal. Indeed, due to the presence of ethanol in the sample, PTR-MS can only be employed after dilution of the headspace or at the expense of radical changes in the operational conditions. In the present research work, PTR-ToF-MS was coupled to a prototype FastGC system allowing for a rapid (90 s) chromatographic separation of the sample headspace prior to PTR-MS analysis. The system was tested on red wine: the FastGC step allowed to rule out the effect of ethanol, eluted from the column during the first 8 s, allowing PTR-MS analysis to be carried out without changing the ionization conditions. Eight French red wines were submitted to analysis and could be separated on the basis of the respective grape variety and region of origin. In comparison to the results obtained by direct injection, FastGC provided additional information, thanks to a less drastic dilution of the sample and due to the chromatographic separation of isomers. This was achieved without increasing duration and complexity of the analysis. [ABSTRACT FROM AUTHOR]

Highlights: [•] On-line analysis of the roaster off-gas during coffee roasting was performed with proton-transfer-reaction time-of-flight mass-spectrometry (PTR-ToF-MS). [•] The formation dynamics of volatile organic compounds (VOCs) varied with the variety of coffee being roasted. [•] Changing the time temperature roasting profile influenced the VOC formation dynamics significantly. [•] Off-line analysis of the coffee brew complemented the measurements. [Copyright &y& Elsevier]

Highlights: [•] Different Italian PDO dry-cured hams have been evaluated by PTR-ToF-MS. [•] Raw material from Italian industrial crosses has been genetically characterised. [•] The effect of SCD and SREBF1 markers on volatile compound profile was studied. [•] Both markers affect the volatile compound profile of dry-cured ham. [•] Evident effects in San Daniele ham, moderate ones in Parma and Toscano ham. [Copyright &y& Elsevier]

Highlights: [•] Detector-induced mass discrimination and non-linearity effects in PTR-ToF-MS. [•] Ion feedback of the PTR-ToF-MS micro-channel plate (MCP). [•] Detector diagnostics in PTR-ToF-MS. [Copyright &y& Elsevier]

Highlights: [•] We measured fluxes of a multitude of VOC by PTR–TOF–MS in a poplar-based SRC plantation. [•] Isoprene flux was mostly controlled by temperature and light. [•] Methanol flux underwent a complex control involving enzymatic and environmental drivers. [•] Emissions of isoprene and monoterpenes are widespread across poplar genotypes. [•] We quantified the importance of within-plant isoprene oxidation. [Copyright &y& Elsevier]

Abstract: The effect of the IGF-II genotype (AG vs. GG) on the morphological and compositional parameters, the fatty acid composition of intramuscular fat, the odour concentration (analysed by dynamic olfactometry) and the volatile compound profile (analysed by proton transfer reaction time-of-flight mass spectrometry) of dry-cured Iberian ham was studied for the first time, and compared to the effect of pig rearing system (high-oleic concentrated feed vs. acorn and grass). The IGF-II genotype had no effect on most variables. However, it influenced the concentration of some odorants (methanethiol and octanal), although it did not affect odour concentration. Conversely, the rearing system had a significant effect on a large number of ham variables. Results indicate a negligible effect of the IGF-II genotype on the final ham quality and confirm that the rearing system has a marked effect. [Copyright &y& Elsevier]

• A dynamic sensorial evaluation of 6 wines is coupled to dynamic aroma release recording. • Addition of ellagitannin extract impacts the dynamic of sensations of oxidized wine. • Addition of ellagitannin extract impacts the length of aroma release in mouth. • Addition of ellagitannin extract preserves fruitiness under oxidative conditions. Addition of oenological tannins claims to have a positive impact on wine stability, protection from oxidation and likely sensory persistence. However, their role on red wine aroma during oxidation is controversial. The present study aims at investigating the effect of addition of oenological tannins on wine flavour (mainly aroma) before and after air exposure. Temporal Dominance of Sensations, a dynamic sensory evaluation, was coupled with a dynamic chemical measurement (nosespace analysis) using a Proton-Transfer-Reaction Mass-Spectrometer connected to the nasal cavity of 17 assessors. Results showed that the oxidation of a non-oaked Pinot Noir red wine decreases the fruity aroma dominance and increases the maderised and prune one. A contextual decrease of the fruity ethyl decanoate and increase of oxidative Strecker aldehydes are observed. Ellagitannins but not proanthocyanidins preserved perception of fruitiness and prevented increase of maderised notes. Moreover, ellagitannins increase the aroma persistence mainly in the non-oxidized wine. [ABSTRACT FROM AUTHOR]

Abstract: The High Resolution Proton-Transfer-Reaction Time-of-Flight Mass Spectrometer (HR PTR-TOF-MS) is a powerful analytical tool used by various scientific communities for real-time measurements of volatile organic compounds (VOC). The analysis of HR PTR-TOF-MS data is, however, particularly demanding because of the large amount of complex data being generated. Based on recently developed or described mathematical methods, we have produced a new software tool, the PTR-TOF Data Analyzer, which greatly facilitates the data analysis process. The new software solution allows for i) a combined Poisson counting statistics and dead time correction of ion count rates, ii) accurate mass axis calibration, iii) an iterative residual peak analysis that detects up to 5 isobaric peaks per unit m/z, iv) time series analysis of both low and high mass and time resolution data and v) visualization of analysis results for fast quality assurance checks. After having been successfully tested by a group of users with different application needs, the PTR-TOF Data Analyzer is made generally available to the scientific community. This will improve the user-friendliness of the PTR-TOF-MS technique and facilitate scientific work with this new analytical mass spectrometer. [Copyright &y& Elsevier]

Abstract: 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. [Copyright &y& Elsevier]

Volatile Organic Compounds (VOCs) formed during anaerobic digestion of aerobically pre-treated Organic Fraction of Municipal Solid Waste (OFMSW), have been monitored over a 30 day period by a direct injection mass spectrometric technique: Proton Transfer Reaction Time-of-Flight Mass Spectrometry (PTR-ToF-MS). Most of the tentatively identified compounds exhibited a double-peaked emission pattern which is probably the combined result from the volatilization or oxidation of the biomass-inherited organic compounds and the microbial degradation of organic substrates. Of the sulfur compounds, hydrogen sulfide had the highest accumulative production. Alkylthiols were the predominant sulfur organic compounds, reaching their maximum levels during the last stage of the process. H 2 S formation seems to be influenced by the metabolic reactions that the sulfur organic compounds undergo, such as a methanogenesis induced mechanism i.e. an amino acid degradation/sulfate reduction. Comparison of different batches indicates that PTR-ToF-MS is a suitable tool providing information for rapid in situ bioprocess monitoring. [ABSTRACT FROM AUTHOR]

Abstract: In the present study, PTR-TOF-MS was applied to better understand the influence of sugar composition on flavour release in a strawberry flavoured cereal bar system. To achieve this, measurements were made both statically from the headspace above cereal bar samples (in vitro) and dynamically from flavour release in the nose space during consumption (in vivo). An artificial strawberry flavour of known constituents (17 flavour active volatile compounds) was used in the preparation of cereal bars. For in vitro measurements, eight samples varying in the glucose syrup solids 42DE to polydextrose ratio were assessed. Measurements clearly showed that the level of glucose syrup solids substitution by polydextrose influenced the release of the added flavour compounds. In addition, distinguishable differences were detected for the release of volatile compounds between samples with different levels of glucose syrup solids and polydextrose during in vivo measurements. The improved mass resolution, sensitivity and speed of PTR-TOF-MS enabled direct comparisons between the rate compounds reached the nose space, maximum nose space concentration of compounds, and the time after which compounds were no longer detected in the nose-space. [Copyright &y& Elsevier]