Hans-Georg Schmarr

State Education and Research Center of Viticulture and Horticulture, Neustadt an der Haardt, Rheinland-Pfalz, Germany

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Publications (26)85.85 Total impact

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    ABSTRACT: Qualitative ripening-dependent changes of pineapple volatiles were studied via headspace solid-phase microextraction and analyzed by comprehensive two-dimensional gas chromatography quadrupole mass spectrometry (HS-SPME-GC×GC-qMS). Early green-ripe stage, post-harvest ripened, and green-ripe fruits at the end of their commercial shelf-life were compared to air-freighted pineapples harvested at full maturity. In total, more than 290 volatiles could be identified by mass spectrometry and their linear retention indices. The majority of compounds comprise esters (methyl and ethyl esters of saturated and unsaturated fatty acids, acetates), terpenes, alcohols, aldehydes, 2-ketones, free fatty acids, and miscellaneous γ- and δ-lactones. The structured separation space obtained by GC×GC allowed revealing various homologous series of compound classes as well as clustering of sesquiterpenes. Post-harvest ripening increased the diversity of the volatile profile compared to both early green-ripe maturity stages and on-plant ripened fruits.
    Analytical and Bioanalytical Chemistry 02/2015; 407(9):2591-2608. DOI:10.1007/s00216-015-8474-z · 3.58 Impact Factor
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    ABSTRACT: Ripening-dependent changes of pineapple volatiles were studied in a nontargeted profiling analysis. Volatiles were isolated via headspace solid phase microextraction and analyzed by comprehensive 2D gas chromatography and mass spectrometry (HS-SPME-GC×GC-qMS). Profile patterns presented in the contour plots were evaluated applying image processing techniques and subsequent multivariate statistical data analysis. Statistical methods comprised unsupervised hierarchical cluster analysis (HCA) and principal component analysis (PCA) to classify the samples. Supervised partial least squares discriminant analysis (PLS-DA) and partial least squares (PLS) regression were applied to discriminate different ripening stages and describe the development of volatiles during postharvest storage, respectively. Hereby, substantial chemical markers allowing for class separation were revealed. The workflow permitted the rapid distinction between premature green-ripe pineapples and postharvest-ripened sea-freighted fruits. Volatile profiles of fully ripe air-freighted pineapples were similar to those of green-ripe fruits postharvest ripened for 6 days after simulated sea freight export, after PCA with only two principal components. However, PCA considering also the third principal component allowed differentiation between air-freighted fruits and the four progressing postharvest maturity stages of sea-freighted pineapples.
    Analytical and Bioanalytical Chemistry 02/2015; 407(9):2609-2624. DOI:10.1007/s00216-015-8475-y · 3.58 Impact Factor
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    ABSTRACT: Headspace solid phase microextraction and chirospecific gas chromatography–mass spectrometry in selected ion monitoring mode (HS-SPME–GC–SIM-MS) allowed quantitative determination of δ-lactones (δ-C8, δ-C10) and γ-lactones (γ-C6, γ-C8, γ-C10). A stable isotope dilution assay (SIDA) with d7-γ-decalactone as internal standard was used for quantitative analysis of pineapple lactones that was performed at three progressing post-harvest stages of fully ripe air-freighted and green-ripe sea-freighted fruits, covering the relevant shelf-life of the fruits. Fresh pineapples harvested at full maturity were characterised by γ-C6 of high enantiomeric purity remaining stable during the whole post-harvest period. In contrast, the enantiomeric purity of γ-C6 significantly decreased during post-harvest storage of sea-freighted pineapples. The biogenetical background and the potential of chirospecific analysis of lactones for authentication and quality evaluation of fresh pineapple fruits are discussed.
    Food Chemistry 02/2015; 168:496-503. DOI:10.1016/j.foodchem.2014.07.071 · 3.26 Impact Factor
  • Petra Slabizki, Theodoros Potouridis, Hans-Georg Schmarr
    Chromatographia 12/2014; 77(23-24):1727-1730. DOI:10.1007/s10337-014-2761-2 · 1.37 Impact Factor
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    ABSTRACT: A method for trace-level analysis of 3-alkyl-2-methoxypyrazines (MPs) based on mixed-bed cation-exchange solid phase extraction followed by heart-cut multidimensional gas chromatographic analysis was applied in a trial on viticultural and enological treatments of Sauvignon blanc wines produced in Germany. The quantification was based on a stable isotope dilution assay using deuterated MPs. For method comparison, detection was either with selected ion monitoring with a quadrupole mass spectrometer (MS) or after selected reaction monitoring using a triple quadrupole MS. Comparable performance for MP detection in the lower ng L-1 concentration range was found for both detection methods; however, in some cases, matrix problems could only be solved with MS/MS detection. It could be shown that MP levels varied considerably between the investigated vintages, with concentrations often well below 10 ng L-1. Leaf removal as a viticultural trial was a measure to decrease MP concentrations; however, the effects observed were low in the vintages studied here. Cold maceration and stem addition to the must were found as valuable enological means for increasing the MP concentration and improving the green sensory notes typical for cold climate Sauvignon blanc wines.
    European Food Research and Technology 10/2014; 239(4). DOI:10.1007/s00217-014-2250-8 · 1.39 Impact Factor
  • Charlotte Legrum, Petra Slabizki, Hans-Georg Schmarr
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    ABSTRACT: With respect to the current hypothesis that natural amino acids may serve as starting material for the biosynthesis of alkyl-methoxypyrazines, the enantiomeric distribution of the potent aroma compound 3-sec-butyl-2-methoxypyrazine (SBMP) was determined in various species using heart-cut multidimensional gas chromatography (H/C MDGC) or comprehensive two-dimensional gas chromatography (GC × GC). Complementary to an earlier described separation on octakis-(6-O-methyl-2,3-di-O-pentyl)-γ-cyclodextrin used as chiral stationary phase, we found a reversal of the elution order of SBMP enantiomers on heptakis-(2,3-di-O-methyl-6-O-tert-butyldimethylsilyl)-β-cyclodextrin, providing further confirmation options for that type of analysis. Optimization of the enantioseparation of SBMP in a single-oven H/C enantio-MDGC system involved the use of a dual-jet cryo modulator for trapping of analytes transferred from the achiral (1)D column to the chiral (2)D column before starting the (2)D enantioseparation with an independent temperature ramp. For the enantiodifferentiation by enantio-GC × GC, the modulation period had to be significantly shortened to avoid loss of chiral resolution gained in (1)D. H/C MDGC with mass spectrometric detection (MS) using selected ion monitoring (SIM) was sufficient for parts per billion level analysis, whereas H/C MDGC-MS/MS or GC × GC time-of-flight (TOF) MS were necessary for parts per trillion level analysis. In various vegetables, lady beetles and Vitis vinifera species analyzed, only (S)-SBMP was detected, supporting the hypothesis of natural amino acids serving as starting material for the biosynthesis of alkyl-methoxypyrazines.
    Analytical and Bioanalytical Chemistry 08/2014; DOI:10.1007/s00216-014-8061-8 · 3.58 Impact Factor
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    ABSTRACT: The three constitutional isomers of dimethyl-substituted methoxypyrazines: 3,5-dimethyl-2-methoxypyrazine 1; 2,5-dimethyl-3-methoxypyrazine 2; and 2,3-dimethyl-5-methoxypyrazine 3 are potent flavor compounds with similar mass spectrometric, gas chromatographic, and nuclear magnetic resonance spectroscopic behavior. Therefore, unambiguous analytical determination is critical, particularly in complex matrices. The unequivocal identification of 1-3 could be achieved by homo- and heteronuclear NMR correlation experiments. The observed mass fragmentation for 1-3 is proposed and discussed, benefitting from synthesized partially deuterated 1 and 2. On common polar and apolar stationary phases used in gas chromatography (GC) 1 and 2 show similar behavior whereas 3 can be separated. In our focus on off-flavor analysis with respect to wine aroma, 1 has been described as a "moldy" off-flavor compound in cork and 2 as a constituent in Harmonia axyridis contributing to the so-called "ladybug taint," whereas 3 has not yet been described as a constituent of wine aroma. A successful separation of 1 and 2 could be achieved on octakis-(2,3-di-O-pentyl-6-O-methyl)-γ-cyclodextrin as stationary phase in GC. Applying heart-cut multidimensional GC analysis with tandem mass spectrometric detection we could confirm the presence of 1 as a "moldy" off-flavor compound in cork. However, in the case of Harmonia axyridis, a previous identification of 2 has to be reconsidered. In our experiments we identified the constitutional isomer 1, which was also found in Coccinella septempunctata, another species discussed with respect to the "ladybug taint." The analysis of such structurally related compounds is a demonstrative example for the importance of a chromatographic separation, as mass spectrometric data by itself could not guarantee the unequivocal identification.
    Analytical and Bioanalytical Chemistry 08/2014; 406(25). DOI:10.1007/s00216-014-8049-4 · 3.58 Impact Factor
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    ABSTRACT: Pineapples are highly valued tropical fruits appreciated by many consumers due to their exotic aroma impression. However, fully ripe fruits are exclusively available as a premium niche product, as they are to be exported by rapid cargo-planes. In contrast, the major proportion of pineapples offered on European markets is harvested at a premature green-ripe stage, since their mechanical and microbial stability allows cheaper fruit logistics by cargo ships. Consequently, sea-freighted fruits need to be post-harvest ripened for flavour development; however, differ in their volatile “profiles” compared to fruits harvested at full maturity [1]. In the presented study, HS-SPME-GC×GC-qMS profiles of four progressing post-harvest maturity stages of green-ripe pineapples were compared to fully ripe air-freighted fruits. The majority of more than 300 compounds identified were esters. The structured separation space obtained by GC×GC with clustering of compound classes as well as extracted ion contour plots of unique mass traces facilitated the identification of volatiles even though mass spectral reference data was unavailable. Profile patterns presented in the contour plots were subsequently analyzed in an unbiased fingerprinting approach applying image processing techniques and chemometric data analysis [2]. Based on significantly different signals, Hierarchical Cluster Analysis (HCA) and Partial Least Squares Discriminant Analysis (PLS-DA) were performed to explore interdependencies within the volatile “profiles” and discriminate the different maturity stages, respectively. Furthermore, Partial Least Squares (PLS) regression was shown to be an excellent tool to deduce those volatiles being formed during post-harvest storage. As a result of the fingerprint analysis clear-cut discrimination of differently ripened and post-harvest handled pineapple samples was possible. The HS-SPME-GC×GC-qMS analysis of volatiles in combination with multivariate statistical data evaluation allowed the distinction between different pineapple maturity stages, hence being an excellent method to rapidly screen for metabolic changes occurring during post-harvest shelf-life of pineapple and eventually other fruits. References [1] Steingass, C. B. et al., Food Chemistry 150 (2014) 382 [2] Schmarr, H.-G. et al., Journal of Chromatography A 1217 (2010) 565
    38th International Symposium on Capillary Chromatography (ISCC) and 11th GC×GC Symposium, Riva del Garda, Italy; 05/2014
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    ABSTRACT: Aroma relevant γ- and δ-lactones are important flavor compounds in various foodstuffs. Their quantitative determination is essential for evaluating food sensory properties as well as food authenticity studies. High-throughput head-space solid-phase microextraction as sample preparation, separation by capillary gas chromatography coupled with triple stage quadrupole mass spectrometry has been evaluated as the analytical method. Monitoring selected reaction mass fragments allowed sub-µg/L quantification of γ- and δ-lactones in complex wine matrices. Tandem mass spectrometry improves specific detection of γ- and δ-lactones, a prerequisite for reliable quantification at low-µg/L concentration levels in complex wine matrices. Copyright © 2013 John Wiley & Sons, Ltd.
    Rapid Communications in Mass Spectrometry 12/2013; 27(24):2751-9. DOI:10.1002/rcm.6736 · 2.64 Impact Factor
  • Hans-Georg Schmarr, Petra Slabizki, Charlotte Legrum
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    ABSTRACT: Trace level analyses in complex matrices benefit from heart-cut multidimensional gas chromatographic (MDGC) separations and quantification via a stable isotope dilution assay. Minimization of the potential transfer of co-eluting matrix compounds from the first dimension ((1)D) separation into the second dimension separation requests narrow cut-windows. Knowledge about the nature of the isotope effect in the separation of labeled and unlabeled compounds allows choosing conditions resulting in at best a co-elution situation in the (1)D separation. Since the isotope effect strongly depends on the interactions of the analytes with the stationary phase, an appropriate separation column polarity is mandatory for an isotopic co-elution. With 3-alkyl-2-methoxypyrazines and an ionic liquid stationary phase as an example, optimization of the MDGC method is demonstrated and critical aspects of narrow cut-window definition are discussed.
    Analytical and Bioanalytical Chemistry 06/2013; 405(20). DOI:10.1007/s00216-013-7072-1 · 3.58 Impact Factor
  • Petra Slabizki, Hans-Georg Schmarr
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    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; DOI:10.1016/j.chroma.2012.11.020 · 4.26 Impact Factor
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    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; 1270. DOI:10.1016/j.chroma.2012.11.010 · 4.26 Impact Factor
  • Hans-Georg Schmarr, Karl-Heinz Engel
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    ABSTRACT: Contents and enantiomeric distributions of linalool (3,7-dimethyl-1,6-octadien-3-ol) were investigated in raw and roasted cocoa beans (seeds of Theobroma cacao) of defined origin as well as in commercial products, such as cocoa powders or chocolates. The stereodifferentiation of linalool was achieved by enantioselective multidimensional gas chromatography using heptakis (2,3-di-O-methyl-6-O-tert-butyldimethylsilyl)-β-cyclodextrin as chiral stationary phase. Simultaneous steam distillation–extraction at pH 7 allowed sample preparation without racemization of linalool. Cocoa beans contain linalool primarily as (S)-enantiomer. Model experiments and analyses of commercial products such as cocoa powders and chocolates revealed that technological procedures employed in the manufacturing of cocoa products do not result in significant changes of the original enantiomeric distribution of linalool.
    European Food Research and Technology 11/2012; 235(5). DOI:10.1007/s00217-012-1812-x · 1.39 Impact Factor
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    ABSTRACT: Analytical multidimensional gas chromatography (MDGC) and the excellent separation efficiency it achieves serve advanced characterization of complex volatile and semi-volatile samples, which is unlikely to be accomplished by single-dimensional chromatography. Here, we provide a technical overview of recent method implementation in MDGC, for both the classical sense (i.e. conventional heart-cut MDGC), including recent approaches to MDGC, and the comprehensive two-dimensional gas chromatography (GC × GC) variant.We summarize selected applications in diverse fields that best typify the role of these methods. We also draw attention to concepts (e.g., orthogonality of separation mechanisms and recently introduced microfluidic technology), and briefly comment on compatibility of detection systems.As a guide to potential opportunities for continued innovation in multidimensional applications, we highlight the capabilities of GC platforms that either combine various GC × GC and MDGC arrangements or offer alternative operational modes for implementation of these methods.
    TrAC Trends in Analytical Chemistry 04/2012; 34:1–21. DOI:10.1016/j.trac.2011.10.013 · 6.61 Impact Factor
  • Hans-Georg Schmarr, Stefan Koschinski, Wei Sang, Petra Slabizki
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    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. DOI:10.1016/j.chroma.2011.10.033 · 4.26 Impact Factor
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    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. DOI:10.1021/jf103628g · 3.11 Impact Factor
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    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. DOI:10.1016/j.chroma.2010.06.049 · 4.26 Impact Factor
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    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. DOI:10.1016/j.aca.2010.05.002 · 4.52 Impact Factor
  • Hans-Georg Schmarr, Jörg Bernhardt
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    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; 1217(4-1217):565-574. DOI:10.1016/j.chroma.2009.11.063 · 4.26 Impact Factor
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    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. DOI:10.1002/jssc.200800294 · 2.59 Impact Factor