[Lindinger2013] "Proton-Transfer-Reaction Mass Spectrometry: Increased Selectivity in Explosives and Designer Drugs Detection",
: IONICON Analytik, 2013.
[Hartungen2004] "Proton-transfer-reaction mass spectrometry (PTR-MS) of carboxylic acids: Determination of Henry's law constants and axillary odour investigations",
International Journal of Mass Spectrometry
, vol. 239, no. 2: Elsevier, pp. 243–248, 2004.
Proton-transfer-reaction mass spectrometry (PTR-MS) was used as an analytical tool to measure gas-phase concentrations of short-chain fatty acids. Chemical ionisation of C2single bondC6 carboxylic acids by PTR-MS produced intense protonated molecular ions (with traces of hydrates) along with acylium ion fragments. Gas-phase concentrations were derived using the established method for calculating PTR-MS sensitivity factors. Henry's law constants of carboxylic acids for aqueous solutions at 40 °C were determined. Direct monitoring of volatile fatty acids, known to be associated with secretions from the human axilla, was performed via a specially designed transfer device situated in the axilla. Mass spectral data corresponded with the findings of a sensory assessor.
[Biasioli2004] "PTR-MS monitoring of odour emissions from composting plants",
International journal of mass spectrometry
, vol. 239, no. 2: Elsevier, pp. 103–109, 2004.
We studied the possibility of monitoring with proton transfer reaction-mass spectrometry (PTR-MS) odours emitted in various situations related to composting plants of municipal solid waste (MSW), i.e., waste storage, waste management, and biofilters. Comparison of PTR-MS volatile profiles of the gaseous mixtures entering and exiting a biofilter suggests the possibility of fast and reliable monitoring biofilter efficiency. Moreover, we investigated the relationships between the olfactometric assessment of odour concentration and PTR-MS spectral line intensity finding a positive correlation between the former and several masses and their overall intensity. The application of multivariate calibration methods allows to determine odour concentrations based only on PTR-MS instrumental data. The possibility of avoiding the use of time consuming and expensive olfactometric methods and applications in monitoring waste treatments plants and, in particular, of biofilters is suggested.
[Soukoulis2012] "PTR-TOF-MS Analysis for Influence of Milk Base Supplementation on Texture and Headspace Concentration of Endogenous Volatile Compounds in Yogurt",
Food and Bioprocess Technology
, vol. 5, no. 6: Springer, pp. 2085–2097, 2012.
In the present study, the effects of milk fat (0.3% and 3.5% w/w), solids non-fat (8.4% and 13% w/w), and modified tapioca starch (0%, 0.5%, 1.0%, 1.5%, and 2.0% w/w) concentrations on the textural and physicochemical properties as well as the concentration of several endogenous flavor compounds in the headspace of set and stirred yogurts were investigated. The novel proton transfer reaction time-of-flight mass spectrometry technique was implemented for the non-invasive determination of the amounts of volatile organic compounds in the samples headspace. Milk fat and skim milk powder supplementation of the milk samples increased significantly the firmness and adhesiveness of yogurts (p < 0.001) and improved the stability of the formed gels by increasing their water holding capacity and reducing the amounts of expulsed whey (3.94 and 5.1 g for the milk fat and SNF-fortified samples). Acetaldehyde was significantly (p < 0.001) higher in the low fat-unfortified systems (6.15 ± 0.48 and 5.6 ± 0.60 ppmv, respectively). A similar trend was also reported in the case of 2-propanone (0.91 ± 0.11 and 1.13 ± 0.07 ppmv), diacetyl (334 ± 37 and 350 ± 34 ppbv), 2,3-pentanedione (54 ± 6 and 55 ± 6 ppbv), and 2-butanone (56 ± 7 and 68 ± 5 ppbv) for the same systems. In contrast, the concentration of flavor compounds in the headspace with hydroxyl groups (ethanol and acetoin) increased (p < 0.001) by solid non-fat fortification of milk base (350 ± 32 and 206 ± 7 ppbv, respectively, for the systems fortified with skim milk powder). Modified tapioca starch addition improved the textural properties and gel stability of yogurts whereas affected only the ethanol concentration (222 ± 16 and 322 ± 55 for the control and 2.0% w/w containing systems, respectively). Our data suggested that the reinforcement of textural and structural properties combined with the protein binding affinity of the flavor compounds seemed to be responsible for the aforementioned observations. In the case of stirred yogurts, the gel breakdown did not provoke significant changes in the headspace concentration of the most compounds, with the exception of ethanol, acetoin, and 2,3-pentanedione being significantly (p < 0.05) higher in the stirred yogurts (267 ± 29, 153 ± 11, and 38 ± 1 ppbv, respectively) than set style ones (232 ± 19, 134 ± 9, and 45 ± 3 ppbv, respectively).
[Cappellin2012] "PTR-ToF-MS and data mining methods: a new tool for fruit metabolomics",
, vol. 8, no. 5: Springer, pp. 761–770, 2012.
Proton Transfer Reaction-Mass Spectrometry (PTR-MS) in its recently developed implementation based on a time-of-flight mass spectrometer (PTR-ToF-MS) has been evaluated as a possible tool for rapid non-destructive investigation of the volatile compounds present in the metabolome of apple cultivars and clones. Clone characterization is a cutting-edge problem in technical management and royalty application, not only for apple, aiming at unveiling real properties which differentiate the mutated individuals. We show that PTR-ToF-MS coupled with multivariate and data mining methods may successfully be employed to obtain accurate varietal and clonal apple fingerprint. In particular, we studied the VOC emission profile of five different clones belonging to three well known apple cultivars, such as ‘Fuji’, ‘Golden Delicious’ and ‘Gala’. In all three cases it was possible to set classification models which can distinguish all cultivars and some of the clones considered in this study. Furthermore, in the case of ‘Gala’ we also identified estragole and hexyl 2-methyl butanoate contributing to such clone characterization. Beside its applied relevance, no data on the volatile profiling of apple clones are available so far, our study indicates the general viability of a metabolomic approach for volatile compounds in fruit based on rapid PTR-ToF-MS fingerprinting.
[Heenan2012] "PTR-TOF-MS monitoring of in vitro and in vivo flavour release in cereal bars with varying sugar composition",
, vol. 131, no. 2: Elsevier, pp. 477–484, 2012.
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.