-
[show abstract]
[hide abstract]
ABSTRACT: A robust method for routine quality control of corky off-flavour compounds in wine and cork soak matrices has been established. Based on an automated headspace solid phase microextraction (HS-SPME), the method needs only marginal sample preparation and achieves low (sub-ngL(-1)) trace level detection limits (LODs) for the most relevant off-flavour compounds, such as 2,4,6-trichloroanisole (TCA), 2,3,4,6-tetrachloroanisole (TeCA) and 2,4,6-tribromoanisole (TBA). Particularly for wine matrix, reliable trace level quantification had only been achieved after applying heart-cutting multidimensional gas chromatography (MDGC). Using a halogen-sensitive electron capture detector (ECD) and quantification with a stable isotope dilution assay (SIDA), LODs of 0.1ngL(-1) for TCA, TeCA and TBA could be obtained. Since a SIDA based quantification method is used with a non-mass spectrometric detector, the necessary chromatographic resolution of internal standard and target analyte peaks resulted from the use of highly deuterated [(2)H(5)]-isotopologues.
Journal of chromatography. A 11/2012; · 4.19 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The separation of deuterated and non-deuterated compounds in gas liquid partitioning chromatography (GLC) on silicone type stationary phase usually results in the inverse isotope effect. With ionic liquids (ILs) as stationary phase, however, this may show a totally different nature. The inverse isotope effect, in which heavier (deuterated) isotopic compounds (isotopologues) elute earlier, is to be expected when van der Waals (London) dispersion forces play a dominant role in the solute-stationary phase interaction. Such (apolar) interactions seem to play only a minor role when ILs are the stationary phases, leading to only a marginal inverse isotope effect, e.g. for the separation of 2,4,6-trichloroanisole and its [(2)H(5)]-isotopologue on 1,12-di(tripropylphosphonium) dodecane bis(trifluoromethansulfonyl) amide (commercialized as SLB-IL59, Supelco). Indeed, with the most polar stationary phase available (commercialized as SLB-IL111; Supelco), this separation showed a normal isotope effect. Further examples are presented and the nature of the isotope effect observed is discussed.
Journal of chromatography. A 11/2012; · 4.19 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: This work describes the development of a trace level (<1 ngL(-1)) analysis of haloanisoles in complex wine matrix. The suggested method involves sample preparation based on solid phase extraction, a clean-up to remove acidic compounds, concentration of the haloanisole fraction and large volume on-column injection into a multidimensional GC-MS system. Mass spectrometric detection in the selected ion mode allowed reliable quantification of 2,4,6-trichloroanisole (TCA) or 2,4,6-tribromoanisole (TBA), via their highly deuterated ([(2)H5]) isotopologues as internal standards (stable isotope dilution analysis; SIDA), which had prior been synthesized in house. The development of this new method had become necessary, as a one-dimensional HS-SPME-GC-ECD method, routinely applied for analysis of TCA in cork soaks, had to be extended for TeCA and TBA determination, but failed due to co-elutions within wine matrices. The newly developed SPE//MDGC-MS method provided detection limits well below olfactory thresholds of the analytes with 0.05 ngL(-1) (LOD), 0.19 ngL(-1) (LOQ) for TCA, 0.06 ngL(-1) (LOD), 0.21 ngL(-1) (LOQ) for TeCA, and 0.09 ngL(-1) (LOD), 0.34 ngL(-1) (LOQ) for TBA.
Journal of chromatography. A 10/2011; 1226:96-102. · 4.19 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Aroma changes in Chardonnay and Riesling base wines caused by the second fermentation were investigated by a targeted component analysis: A stable isotope dilution approach using headspace solid phase microextraction coupled online to gas chromatography mass spectrometry (HS-SPME-GC-MS) was applied to quantify 37 compounds relevant for sparkling wine aroma. In an enrichment experiment, glycosylated precursors isolated from one Chardonnay and one Riesling base wine were used to double the original amount in these base wines. Along with increased concentrations of precursor-derived volatiles after the second fermentation, descriptive sensory evaluation revealed an enhancement of fruity aroma impressions reminiscent of, for example, peach or cantaloupe. Except for benzyl alcohol, linalool, and 3-methylpentanol, no quantitative 2-fold increase of volatiles was found with a 2-fold increase in precursor concentration, as other metabolic pathways seem to interfere with aroma formation from glycosides.
Journal of Agricultural and Food Chemistry 02/2011; 59(6):2524-33. · 2.82 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The analysis of 3-alkyl-2-methoxypyrazines in Vitis vinifera grape must or wine at the low nanogram per liter level failed in several situations when applying a one-dimensional gas chromatographic analysis with mass spectrometric detection (GC-MS). Sample preparation methods such as headspace solid phase microextraction or solid phase extraction were convenient procedures, however lacking extraction selectivity for complex matrices. Analysis by comprehensive two-dimensional gas chromatography with mass spectrometric detection clearly demonstrated the potential for co-elution in such matrices and the risk for erroneous results when applying one-dimensional GC-MS. In one example, matrix problems would have been a challenge even for a comprehensive two-dimensional chromatographic approach with MS detection (GC×GC-MS). A solution to matrix problems was found by protonating the 3-alkyl-2-methoxypyrazines in acidic pH and sample clean-up using solid phase extraction with a mixed-mode polymeric cation-exchange sorbent. Quantification was performed by a stable isotope dilution assay, following analysis by on-line coupled high performance liquid chromatography with multidimensional gas chromatography and detection with mass spectrometry (on-line LC-MDGC-MS). This new approach allowed trace-level analysis of 3-alkyl-2-methoxypyrazines in grape musts and wines and is described for V. vinifera Sauvignon blanc, following 3-alkyl-2-methoxypyrazines concentrations during ripening and in the processed wines.
Journal of chromatography. A 10/2010; 1217(43):6769-77. · 4.19 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Microoxygenation (MOX) is a widely applied technique to deliver continuously trace amounts of oxygen to red wine during vinification and ageing in order to improve color stability and sensory properties. Proven by sensory means, the added oxygen modifies not only tannin structure and color of the wines, but also their composition of volatiles. In this study different microoxygenation treatments prior and after malolactic fermentation were carried out for Pinot noir, Cabernet Sauvignon and Dornfelder wines of the 2007 vintage. Volatile components of subsequent wines were analyzed using headspace-solid phase microextraction coupled to comprehensive two-dimensional gas chromatography-quadrupole mass spectrometry (GC x GC-qMS). Quantitative data were retrieved from two-dimensional images obtained from GC x GC chromatograms of volatile compounds applying a software package, which is commonly used in the field of proteomics for two-dimensional electrophoresis gels. This approach revealed a discrimination of the applied treatments by multivariate statistics based on volatiles alone, such as the clear distinction among wines treated before or after malolactic fermentation in case of Cabernet Sauvignon and Dornfelder or the effect of different oxygen doses. Besides the differentiation of MOX treatments from the untreated control, specific varietal and technological effects could be distinguished. The image processing of the GC x GC data offered valuable tools which were able to identify those areas in the 2D images that were most responsible for discrimination among different MOX treatments. Based on the loadings of individual aroma compounds a set of markers for the MOX-induced modifications of volatiles could be suggested.
Analytica chimica acta 07/2010; 672(1-2):114-23. · 4.31 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: An image processing approach originating from the proteomics field has been transferred successfully to the processing of data obtained with comprehensive two-dimensional gas chromatographic separations data. The approach described here has proven to be a useful analytical tool for unbiased pattern comparison or profiling analyses, as demonstrated with the differentiation of volatile patterns (“aroma”) from fruits such as apples, pears, and quince fruit. These volatile patterns were generated by headspace solid phase microextraction coupled to comprehensive two-dimensional gas chromatography (HS-SPME-GC × GC). The data obtained from GC × GC chromatograms were used as contour plots which were then converted to gray-scale images and analyzed utilizing a workflow derived from 2D gel-based proteomics. Run-to-run variations between GC × GC chromatograms, respectively their contour plots, have been compensated by image warping. The GC × GC images were then merged into a fusion image yielding a defined and project-wide spot (peak) consensus pattern. Within detected spot boundaries of this consensus pattern, relative quantities of the volatiles from each GC × GC image have been calculated, resulting in more than 700 gap free volatile profiles over all samples. These profiles have been used for multivariate statistical analysis and allowed clustering of comparable sample origins and prediction of unknown samples. At present state of development, the advantage of using mass spectrometric detection can only be realized by data processing off-line from the identified software packages. However, such information provides a substantial basis for identification of statistically relevant compounds or for a targeted analysis.
Journal of chromatography. A 11/2009; · 4.19 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: A method for the analysis of the homologous series of alkanals, (E)-2-alkenals, and (E,E)-2,4-alkadienals is described utilizing a headspace solid-phase microextraction (HS-SPME) step and on-fiber derivatization with O-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine (PFBHA) hydrochloride. Oxime derivatives formed on the fiber are desorbed in the gas chromatographic injector and analyzed by comprehensive 2-D GC coupled to quadrupole MS (GC x GC-qMS). Selecting specific fragment ions within the electron impact mass spectra of the oxime derivatives provides a suitable method for the target analysis of these aldehyde classes, which furthermore benefits from the increased separation efficiency by GC x GC. The analysis of higher molecular weight aldehydes is described in wine and grape seed oil as examples. Quantification of the aldehydes utilizes a stable isotope dilution analysis (SIDA) assay with octan-d(16)-al as isotopomeric internal standard. Besides the selectivity and sensitivity of aldehyde analysis using PFBHA derivatives, critical aspects on background level contamination and repeatability of the sample preparation method are discussed. Optimization of GC x GC-qMS parameters allowed a considerable saving of the cryogenic medium, involving additional (unmodulated) conditioning runs, rendering the method more amenable to routine analysis.
Journal of Separation Science 10/2008; 31(19):3458-65. · 2.73 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: An improved method for the analysis of carbonyls is described utilizing a headspace solid-phase microextraction (HS-SPME) step and on-fiber derivatization with O-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine (PFBHA) hydrochloride. Thermal desorption of the oxime derivatives formed on the fiber is followed by gas chromatographic separation coupled to an ion trap tandem mass spectrometer (GC-ITMS). Selecting specific fragment ions within the electron ionization (EI(+)) mass spectra of these oxime derivatives as precursor ions for MS-MS fragmentation provides a suitable method for the target analysis of individual carbonyl classes, such as alkanals, (E)-2-alkenals, (E,E)-2,4-alkadienals, and others. Retention indices on polar as well as on apolar stationary phases along with EI(+) mass spectra patterns are presented for a large set of oxime derivatives, giving valuable information needed for unambiguous assignment of substances in complex sample matrices. The fast sample preparation and derivatization step via HS-SPME can be automated and is applicable to a variety of biological samples and foodstuffs, allowing rapid and sensitive screening analyses of important aldehydic biomarkers and aroma active compounds.
Analytica chimica acta 07/2008; 617(1-2):119-31. · 4.31 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The key compound in the wine off-flavor phenomenon "Untypische Alterungsnote" (UTA) is 2-aminoacetophenone (AAP). A new method for its quantitative analysis in wine is described. The analysis is based on solid phase extraction with LiChrolut EN as sorbent material followed by multidimensional gas chromatography coupled to mass spectrometry (MDGC-MS). Matrix effects due to the complex wine aroma composition could be overcome by an alkaline washing step of the extract and the use of selected ion monitoring as detection mode. Quantification is based on a stable isotope dilution assay using deuterated 2-aminoacetophenone as internal standard.
Journal of Chromatography 06/2007; 1150(1-2):78-84. · 4.53 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The enantiomeric compositions of 2-methylbutanol (1), 4-methylhexanol (2), 2-methylbutanoic acid (3), and 4-methylhexanoic acid (4) present in rhubarb (Rheum rhabarbarum L.) stalks were determined. Enantiodifferentiation was achieved via multidimensional gas chromatography using heptakis(2,3,6-tri-O-ethyl)-beta-cyclodextrin as a chiral stationary phase. For all compounds the enantiomeric ratios were in favor of the (R)-enantiomers. The alcohols (1 and 2) exhibited generally high excesses of the (R)-enantiomers, the ratios varying slightly from batch to batch. For the acid (3) a rather narrow range averaging 65% (R):35% (S) was observed. The procedure applied to isolate the volatiles (vacuum headspace technique, simultaneous distillation--extraction, liquid--liquid extraction) had no significant impact on the enantiomeric ratios. The study describes for the first time a plant used as food material in which 2-methyl-branched volatiles are not nearly exclusively present as (S)-enantiomers. This information enlarges the current regulatory knowledge regarding the classification of these important flavor compounds as "natural" on the basis of their enantiomeric ratios.
Journal of Agricultural and Food Chemistry 12/2003; 51(24):7086-91. · 2.82 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: An approach based on on-line coupled liquid chromatography-gas chromatography (LC-GC) was developed for the rapid analysis of gamma-oryzanol in rice. Total lipids were extracted from rice and subjected to LC-GC without any prior purification. gamma-Oryzanol was pre-separated by HPLC from rice lipids and transferred on-line to GC analysis in order to separate its major constituents. 24-methylenecycloartanyl ferulate, cycloartenyl ferulate, campesteryl ferulate, beta-sitosteryl ferulate and campestanyl ferulate. The identities of the compounds were confirmed by off-line GC-MS analysis. Total gamma-oryzanol content could be quantified by HPLC-UV detection and the distribution of gamma-oryzanol constituents could be determined by on-line coupled GC analysis. The proposed methodology paves the way for high-throughput investigations providing information on natural variations in gamma-oryzanol content and its composition in different rice varieties.
Journal of Chromatography 02/2003; 985(1-2):403-10. · 4.53 Impact Factor
