Impact of phase ratio, polydimethylsiloxane volume and size, and sampling temperature and time on headspace sorptive extraction recovery of some volatile compounds in the essential oil field.
ABSTRACT This study evaluates concentration capability of headspace sorptive extraction (HSSE) and the influence of sampling conditions on HSSE recovery of an analyte. A standard mixture in water of six high-to-medium volatility analytes (isobutyl methyl ketone, 3-hexanol, isoamyl acetate, 1,8-cineole, linalool and carvone) was used to sample the headspace by HSSE with stir bars coated with different polydimethylsiloxane (PDMS) volumes (20, 40, 55 and 110 microL, respectively), headspace vial volumes (8, 21.2, 40, 250 and 1000 mL), sampling temperatures (25, 50 and 75 degrees C) and sampling times (30, 60 and 120 min, and 4, 8 and 16 h). The concentration factors (CFs) of HSSE versus static headspace (S-HS) were also determined. Analytes sampled by the PDMS stir bars were recovered by thermal desorption (TDS) and analysed by capillary GC-MS. This study demonstrates how analyte recovery depends on its physico-chemical characteristics and affinity for PDMS (octanol-water partition coefficients), sampling temperatures (50 degrees C) and times (60 min), the volumes of headspace (40 mL) and of PDMS (in particular, for high volatility analytes). HSSE is also shown to be very effective for trace analysis. The HSSE CFs calculated versus S-HS with a 1000 mL headspace volumes at 25 degrees C during 4 h sampling ranged between 10(3) and 10(4) times for all analytes investigated while the limits of quantitation determined under the same conditions were in the nmol/L range.
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ABSTRACT: Fungi emit a large spectrum of volatile organic compounds (VOCs). In the present study, we characterized and compared the odor profiles of ectomycorrhizal (EM), pathogenic and saprophytic fungal species with the aim to use these patterns as a chemotyping tool. Volatiles were collected from the headspace of eight fungal species including nine strains (four EM, three pathogens and two saprophytes) using the stir bar sorptive extraction method and analyzed by gas chromatography - mass spectrometry (GC-MS). After removal of VOCs released from the growth system, 54 VOCs were detected including 15 novel compounds not reported in fungi before. Principle component and cluster analyses revealed that fungal species differ in their odor profiles, particularly in the pattern of sesquiterpenes. The functional groups and species could be chemotyped by using their specific emission patterns. The different ecological groups could be predicted with probabilities of 90 to 99%, whereas for the individual species the probabilities varied between 55 and 83%. This study strongly supports the concept that the profiling of volatile compounds can be used for non-invasive identification of different functional fungal groups.Fungal Genetics and Biology 03/2013; · 3.26 Impact Factor
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ABSTRACT: A dynamic headspace sorptive extraction (DHS) combined with thermal desorption (TD) and coupled with gas chromatography-mass spectrometry (GC/MS) was developed for the determination of eleven esters which contribute to the fruity aroma in sweet wines. A full factorial (4 factors, 2 level) experiment design was used to optimize the extraction conditions and the results were evaluated by Multiple Linear Regression (MLR) and Principal Component Analysis (PCA). The esters showed optimal extraction using an extraction temperature of 30 ºC during 20 min, and a subsequent purge volume of 300 mL and dry volume of 50 mL. Afterwards, quantification was achieved using calibration curves constructed for each ester with linear regression equations having correlation coefficients (R2) ranging from 0.9894 to 0.9981. The proposed method was successfully validated and showed good intermediate precision, repeatability and accuracy values for all the monitored compounds. Finally, the method was applied to quantify esters, with fruity aromatic notes, of sweet white and red wines, elaborated with different winemaking processes. Keywords dynamic headspace, experimental design, method validation, volatile esters, fruity aroma, sweet winesTalanta 01/2014; 123:32–38. · 3.50 Impact Factor
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ABSTRACT: The aim of this work was to develop a new analytical technique for the study of the organoleptic compounds (flavour profile) of the Graciano Vitis vinifera wine variety. The cv. Graciano is a singular variety of red grapes with its origins in La Rioja and Navarra (northern Spain). This variety transfers an intense red colour, aroma and high acidity to musts and provides greater longevity and, consequently, a better capacity for ageing wine. A new dual-stir bar sorptive extraction approach coupled with thermal desorption (TD) and GC-MS has been used to extract the volatile and semivolatile compounds. In this extraction step, the optimal values for the experimental variables were obtained through the Response Surface Methodology (RSM). Full scan chromatogram data were evaluated with two deconvolution software tools, and the results were compared. The volatile and semivolatile components were identified with an MS match ≥80%. As a result, the flavour metabolome of the Graciano Vitis vinifera wine variety was obtained, and 205 metabolites were identified using different databases. These metabolites were grouped into esters, acids, alcohols, nitrogen compounds, furans, lactones, ketones, aldehydes, phenols, terpenes, norisoprenoids, sulphur compounds, acetals and pyrans. The majority of the metabolites observed had already been reported in the literature; however, this work also identified new, previously unreported metabolites in red wines, which may be characteristic of the Graciano variety.Analytica chimica acta 05/2013; 777:41-8. · 4.31 Impact Factor