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Stable isotope ratios of individual plant components have become a valuable tool for the determination of the geographical origin and authenticity of foodstuff. A recently published method with considerable potential in this context is the measurement of the deuterium/hydrogen (D/H) isotope ratios of plant matter methoxyl groups. The method entailed cleavage of methyl ethers or esters with hydriodic acid (HI) to form gaseous methyl iodide (CH3I) and then measurement of the d 2 H value of this gas. Here, as a follow up to a previous study, we describe a method for the rapid and precise d 13 C analysis of plant matter methoxyl groups using gas chromatography/combustion/isotope ratio mass spectrometry (GC/C/IRMS). Conditions for sample preparation were investigated for isotope discrimination effects, the GC conditions optimized, the reproducibility of the measurement of standards undertaken, and the precision of the method defined. The reproducibility of the d 13 C value determined for a CH3I standard on 20 consecutive measurements was found to be 0.17%. The method was also tested on four methoxyl-rich plant components: vanillin, lignin, wood and pectin. The analytical precision obtained, expressed as the average standard deviation, for these compounds was found to be better than 0.13%. The described procedure which is simple and rapid, allowing preparation and analysis of a sample within 1h, produces accurate and reproducible isotopic measurements. We suggest that this validated d 13 C method when employed together with the recently published d 2 H method for two-dimensional stable isotope studies of organic matter

The stereoisomers of linalool and lilac aldehyde/alcohol were determined in the flower scent of 15 plant species using enantioselective multidimensional gas chromatography/mass spectrometry (enantio-MDGC/MS). Both linalool and all 8 stereoisomers of lilac alcohol and lilac aldehyde were detected, and there was a species-specific pattern. Single stereoisomers were collected by micropreparative-enantio-MDGC and were electrophysiologically tested on antennae of the noctuid moth Hadena bicruris, a species known to rely on lilac aldehyde for finding its host plant. The moth responded to all 8 stereoisomers, though only four stereoisomers were found in the scent of its host plant. The moth was less sensitive to some isomers than to others.

δ13CV-PDB, δ2HV-SMOW and δ18OV-SMOW multielement isotope ratio mass spectrometry analysis of linalool and linalyl acetate, the main components of lavender oils, is reported. Self-prepared and commercially available lavender oils, as well as samples of linalool and linalyl acetate labelled as synthetic and natural products respectively, were investigated. Multielement/multicomponent isotope ratio mass spectrometry analysis and—as far as possible—in conjunction with enantioselective analysis is judged to be the most comprehensive basis of authenticity assessment in flavour and essential oil analysis.

The combination of gas chromatography-combustion-isotope ratio mass spectrometry (GC-C-IRMS) and gas chromatography-pyrolysis-isotope ratio mass spectrometry (GC-P-IRMS) is applied to the authenticity assessment of cinnamaldehyde from various sources. For that reason, cinnamon oils were self-prepared by steam distillation from three different varieties of cinnamon bark on the market, C. ceylanicum (ceylon), C. cassia (cassia) and C. burmanii (cassia vera). Furthermore, the so-called wood cinnamon was investigated, which is produced from the outer bark of older branches of cinnamon of minor quality. Self-prepared oils were analysed from commercial cinnamon powder. In addition several commercial samples of cinnamon oil and cinnamaldehyde, some of them declared to be natural, were investigated. δ 2ΗV-SMOW and δ 13CV-PDB values of cinnamaldehyde were determined and characteristic authenticity ranges were deduced, allowing the differentiation between synthetic and natural samples. By correlation of both the δ 2ΗV-SMOW and δ 13CV-PDB values, characteristic authenticity ranges were defined for ceylon, cassia and wood cinnamon. The δ 2ΗV-SMOW and δ 13CV-PDB values of cassia vera samples are in the range of cassia. By comparing the δ 2ΗV-SMOW values of different self-prepared samples (ground bark, distillate) of cinnamon determined by TC/EA-IRMS with the corresponding GC-IRMS values, online GC-IRMS methods are proved to be essential in the authentication of complex natural products.

Syringa vulgaris L. inflorescences were fed with aqueous solutions of regioselectively deuterated compounds assumed to be precursors of lilac aldehyde and lilac alcohol, respectively. Volatiles were extracted by stir bar sorptive extraction (SBSE) and analyzed using enantioselective multidimensional gas chromatography/mass spectrometry (enantio-MDGC/MS); deuterium-labeled lilac aldehydes and lilac alcohols were separated from unlabeled stereoisomers on a fused silica capillary column, coated with heptakis(2,3-di-O-methyl-6-O-tert-butyldimethylsilyl)-beta-cyclodextrin (DIME-beta-CD) (30%) in SE 52 (70%), as the chiral stationary phase. Feeding experiments with [5,5-(2)H(2)]mevalonic acid lactone 22 and [5,5-(2)H(2)]deoxy-d-xylose 23 indicate that the novel mevalonate independent 1-deoxy-d-xylose 5-phosphate/2C-methyl-d-erythritol 4-phosphate pathway is the dominant metabolic route for biosynthesis in lilac flowers. Additionally, bioconversion of deuterium-labeled d(5)-(R/S)-linalool 3, d(6)-(R)-linalool 21, d(5)-(R/S)-8-hydroxylinalool 6, d(5)-(R/S)-8-oxolinalool 7, d(5)-lilac aldehydes 8-11 and d(5)-lilac alcohols 12-15 into lilac during in vivo feeding experiments was investigated and the metabolic pathway is discussed. Incubation of petals with an aqueous solution of deuterated d(5)-(R/S)-linalool 3 indicates an autonomic terpene biosynthesis of lilac flavor compounds in the flower petals of lilac.

Gas chromatography-pyrolysis-isotope mass spectrometry (GC-P-IRMS) is applied to the authenticity assessment of lavender oils. For this reason, self-prepared lavender oils, samples of linalool and linalyl acetate labeled as synthetic and natural, and commercially available lavender oils have been investigated. 2H/1H isotope ratios of linalool and linalyl acetate have been determined, and characteristic ranges of authenticity were deduced. Samples of natural linalool and linalyl acetate are clearly differentiated from those of synthetic origin by their δ2HV-SMOW values. Besides enantioselective multidimensional gas chromatography-mass spectrometry (enantio-MDGC-MS), online GC-P-IRMS has proven to be an additional and powerful tool in the detection of lavender oils adulteration.

The sesquiterpene germacrene D and two deuterium-labeled isotopomers were analyzed by enantio-multidimensional gas chromatography with tandem mass spectrometry in order to investigate mass spectral fragmentation mechanisms. The deuterated analogues were derived from in vivo feeding experiments with 1-[5,5-D2]deoxy-D-xylulose-5-phosphate using intact plant material of Solidago canadensis and were formed by biosynthesis via the methylerythritol phosphate pathway.

2-Methyl-4-(2,2,3-trimethylcyclopent-3-en-1-yl)-but-2-enol is a synthetic fragrance with a strong sandalwood-like odor. It was found that the (R)-enantiomer is exclusively responsible for the sandalwood-like odor, whilst the (S)-enantiomer has only a faint, non-specific odor. Consequently, enantioselective analysis is a powerful tool in sensory quality control of 2-methyl-4-(2,2,3-trimethylcyclopent-3-en-1-yl)-but-2-enol. The industrial synthesis starts from u-campholene aldehyde via 2-methyl-4-(2,2,3-trimethylcyclopent-3-en-1-yl)-but-2-enal. This is why the enantiomeric purity of 2-methyl-4-(2,2,3-trimethylcyclopent-3-en-1-yl)-but-2-enol depends on the purity of u-campholene aldehyde as starting material. Hence, an enantioselective analysis of u-campholene aldehyde, 2-methyl-4-(2,2,3-trimethylcyclopent-3-en-1-yl)-but-2-enal, and 2-methyl-4-(2,2,3-trimethylcyclopent-3-en-1-yl)-but-2-enol was achieved by enantioselective gas chromatography using tert-butyldimethylsilylated-cyclodextrin derivatives as chiral GC phases.

Stir bar sorptive extraction (SBSE), a recently introduced solventless extraction technique, was applied for the enantioselective analysis of chiral monoterpenes in tea tree oil, eucalyptus oil and thyme oil using enantioselective multidimensional gas chromatography–mass spectrometry (enantio-MDGC–MS). In addition, headspace sorptive extraction (HSSE) and in vivo headspace sorptive extraction (in vivo HSSE) of the chiral monoterpenes in three aromatic and medicinal plants, thyme [Thymus vulgaris (L.)], eucalyptus [Eucalyptus globulus (L.)] and tea tree [Melaleuca alternifolia (C.)], was investigated and the results of the different sampling techniques were compared and discussed. This method was utilized in order to establish characteristic authenticity profiles of the essential oils. Moreover, the enantiomeric ratios of the major and minor chiral components emitted in living plants were determined. Copyright © 2001 John Wiley & Sons, Ltd.

Several cyclodextrin derivatives dissolved in different polysiloxanes have been investigated with regard to their suitability for achieving simultaneous enantioseparation of kavain, dihydrokavain, methysticin, and dihydromethysticin by high resolution gas chromatography. Enantioseparation of these four chiral kavapyrones is achieved using heptakis(2,3-di-O-methyl-6-O-tert-butyldimethylsilyl)-β-cyclodextrin dissolved in a mixture of SE-30/SE-52 (1:1) as the chiral stationary phase.

Separation factors and thermodynamic data for the separation of various chiral analytes on different di-O-tert-butyldimethyl-silylated cyclodextrin derivatives are collected and described. Modifying the substitution pattern of the tert-butyldimethylsilyl group in position 2 and 3 or changing from β- to γ-cyclodextrin significantly affects the separation properties of the cyclodextrin derivatives.

3-Mercapto-2-methylpropanol, an odorous compound recently identified in red wines, was extracted from a red wine variety, using a low-temperature vacuum distillation coupled with a specific reversible thiol capture. The analysis of the diacetylated wine extract by enantioselective multidimensional gas chromatography with mass spectrometry detection revealed the presence of only one enantiomer, (R)-3-mercapto-2-methylpropanol. Although both of the optical isomers are characterized by the same broth and sweat odour, they have very different odour thresholds. The amounts of (R)-3-mercapto-2-methylpropanol in young Cabernet-Sauvignon and Merlot wines can exceed its perception threshold, thus suggesting its contribution to the aroma of these wines.

Enantioselective gas chromatography and/or 13C/12C isotope ratio analysis are suitable tools for the authenticity assessment of the fusel alcohols, 2- and 3-methylbutanol (1 and 2, respectively). The chiral compound, 1 is biosynthesised almost completely as the (S)-enantiomer, regardless of which carbohydrate source is used for fermentation. The type of CO2 fixation and some plant-specific influences were of prime importance to the 13C/12C isotope ratios of the starting materials in alcoholic fermentation, and the δ13C values of 1 and 2 differed significantly. In general, the δ13C values of 2 were about 4–5o lower than those of 1 produced via the same fermentation process. 13C/12C isotope ratio analysis results can be used to determine between fusel alcohols produced from different sources, and provides a new and valuable method of authenticity assessment.

The δ13CPDB values of characteristic flavour compounds of black Ceylon, Darjeeling and Assam teas were determined using gas chromatography-isotope ratio mass spectrometry. The influence of different harvest times, years and various cultivation regions on the δ13CPDB and the δ13C cis linalool oxide (fur.) values were investigated. By comparison with suitable internal isotopic standards, adulterations with methyl salicylate were detectable.

The even numbered γ(δ)-thionolactones (C6–C12) were investigated, using heptakis(2,3-di-O-methyl-6-O-tert-butyldimethylsilyl)- and heptakis(2,3-di-O-acetyl-6-O-tert-butyldimethylsilyl)-β-cyclodextrin as chiral stationary phases in capillary gas chromatography. The odor characteristics of γ(δ)-thionolactone enantiomers were investigated by enantioselective gas chromatography/olfactometry.

Methyl-branched volatiles in apples and processed apples are investigated. The ratio of 3-methyl-branched and 2-methyl-branched flavor compounds was determined and the enantiomeric distribution of the latter investigated. The enantiomeric ratios of 2-methyl-branched volatiles are analyzed, using heptakis(2,3-di-O-methyl-6-O-tert-butyldimethylsilyl)-β-cyclodextrin as an efficient enantioselective stationary phase in capillary GC. 2-Methylbutanoic acid and the corresponding esters (methyl−n-hexyl ester), 2-methylbutanol, and 2-methylbutyl acetate were detected as genuine flavor compounds favoring (S)-configuration and high enantiomeric purity (>99%). 3-Methylbutanoic acid, 3-methylbutanol, and 3-methylbutyl acetate are proved to be not genuine compounds of the apple aroma but fermentation products. Keywords: Apple flavor; methyl-branched volatiles; enantioselective capillary gas chromatography; enantioselective multidimensional gas chromatography (enantio-MDGC)

The direct enantioseparation of 2-methylbutanal, 2-methylpentanal, 2-ethylhexanal, 3-methylpentanal and 4-methylhexanal was achieved using enantioselective gas chromatography and the chiral stationary phase heptakis-[2,3-di-O-acetyl-6-O-tert.butyldimethylsilyl]-β-cyclodextrin (DIAC-TBDMS-β-CD). Odour characteristics and threshold values of detection for compounds were evaluated by enantioselective gas chromatography/olfactometry. Enantiopure reference compounds with defined absolute configurations were synthesized starting from the corresponding alcohols or acids which were commercially available or prepared in the laboratory.

Multidimensional gas chromatography coupled on-line with isotope ratio mass spectrometry (MDGC-IRMS) is presented as a powerful method for origin-specific analysis. Scope and limitations of this sophisticated coupling technique are discussed with regard to accuracy and precision.

The δ13CPDB values of characteristic flavor components of mandarin essential oils have been measured by gas chromatography/isotope ratio mass spectrometry. For genuine mandarin oils a characteristic authenticity profile was established and used for the authenticity control of commercially available mandarin oils. In addition to cold-pressed mandarin essential oils, distilled mandarin and sweet orange oils were investigated to assess blends of cold-pressed mandarin oils with these products. Keywords: GC/IRMS; δ13CPDB values; authenticity profile; authenticity control; mandarin essential oil; Citrus reticulata Blanco

Using enantioselective multidimensional gas chromatography with heptakis[2,3-di-O-acetyl-6-O-(tert-butyldimethylsilyl)]-β-cyclodextrin as the chiral stationary phase, the simultaneous analysis of the 3-butylphthalide enantiomers and all eight 3-butylhexahydrophthalide stereoisomers was achieved. Enantiomeric distributions of compounds in celery, celeriac, celery seed, and fennel extracts were elucidated. Keywords: Enantioselective multidimensional gas chromatography (enantio-MDGC); 3-butyl(hexahydro)phthalide stereoisomers; celery; celeriac; fennel

Using enantioselective gas chromatography and heptakis(2,3-di-O-acetyl-6-O-tert-butyldimethylsilyl)-β-cyclodextrin (DIAC-TBDMS-β-CD) as the chiral stationary phase, the direct enantioseparation of 4-tert-butyl-α-methyldihydrocinnamaldehyde was achieved. The threshold values and odour characteristics of the enantiomers were investigated by enantioselective gas chromatography/olfactometry. In order to elucidate stereochemical features, the carbonyl-function was oxidized to the corresponding acid and diastereomeric amides were generated with (S)-2-amino-2-phenyl-ethanol [L(+)-α-phenylglycinol] as the enantiopure reagent. After separation and isolation by high-performance liquid chromatography, absolute configurations were deduced from X-ray structure elucidation of a pure stereoisomer. Amide cleavage, reduction and selective oxidation yielded the enantiomers of 4-tert-butyl-α-methyldihydrocinnamaldehyde.

Using heptakis-(2,3-di-O-acetyl-6-O-tert-butyldimethylsilyl)-β-cy-clodextrin as the chirul stationary phase in enantioselective gas chromatography, the simultaneous enantioselective analysis of all eight 3-butylhexahydrophthalide Stereoisomers was achieved. Fur-thermore, the odor characteristics and odor thresholds were investigated by enantioselective gas chromatography/olfactometry. Racemic standards were synthesized via hydrogenation and subsequent base catalyzed epimerization. Starting from racemic 3-butylphthalide. After separation by high performance liquid chromatography. Relative configurations of the pure diastereoisom-ers were determined by means of NOE-difference spectroscopy. The absolute configuration at C-3 was determined starting from (3S)-butylphthalide as an educt for hydrogenation and epimerization. Absolute configurations of all eight 3-butylhexahydrophtbalide stereoisomers are unambiguously concluded from the NOE-experi-ments in connection with the determination of the absolute configuration at C-3.

The synthesis of enantiopure 3-methylthioalkanals, in particular of 3-methylthiobutanal enantiomers, is described. Elucidation of the structure was achieved by aldehyde-evoked reduction to 3-methylthiobutanol of a known absolute configuration. The odour characteristics of the enantiomers were determined by enantioselective gas chromatography/ olfactometry using octakis(2,3-di-O-butyryl-6-O-tert-butyldimethylsilyl)-γ-cyclodextrin as the chiral stationary phase. Exclusively, the (R)-configured 3-methylthiobutanal exhibits the odour typical of cooked potatoes, whereas the (S)-configured stereoisomer is odourless.

The direct enantioseparation of 2-phenylpropanol, 2-phenylpropanal and 2-phenylpropanal dimethyl acetal was achieved, using enantioselective gas chromatography and heptakis-[2,3-di-0-acetyl-6-0-tert.butyldimethylsilyl]-β-cyclodextrin (DIAC-β-CD) or octakis-[2,3-di-0-acetyl-6-0-tert.butyldimethylsilyl]-γ-cyclodex-trin (DIAC-γ-CD) as the chiral stationary phase. Their odour characteristics and threshold values were investigated by enantioselective gas chromatography/olfactometry. Starting from commercially available (R)-2-phenylpropionic acid, enantiopure (R)-configured reference compounds were synthesized.

Using enantioselective gas chromatography (GC) with an octakis-(2,6-di-O-tert-butyldimethylsilyl)-γ-cyclodextrin column, the direct enantioselective analysis of 3-butylphthalide enantiomers was achieved. Investigations relating to their sensory characteristics and odour thresholds were carried out via enantioselective gas chromatography/olfactometry. In order to elucidate stereochemical features, the lactone structure of racemic 3-butylphthalide was hydrolysed and the carboxy function protected as an isopropylester: the hydroxy function at C-3 was esterified with (R)-2-phenylpropionic acid. The resulting diastereomeric esters were separated and isolated by high performance liquid chromatography. Absolute configurations were derived from 1H-NMR studies according to the Helmchen model, subsequently followed by ester cleavage and recylisation to the corresponding 3-butylphthalide enantiomers. Investigation of the essential oil of celery seed show enantiomeric distributions in the range of 95:5 in favour of the (3S)-enantiomer. This enantiomer shows a significantly lower GC odour threshold value than does the (3R)-enantiomer.

The enantiomeric distributions of cis- and trans-2-methyl-4-propyl-1,3-oxathiane and 3-mercaptohexyl acetate and butanoate in passion fruit extracts were determined by means of multidimensional gas chromatography (MDGC) using sulfur-selective detection. 4S-configured oxathianes and S-configured 3-mercaptohexyl alkanoates of high enantiomeric purity were detected. 2,2-Dimethyl-4-propyl-1,3-oxathiane and 3-mercaptohexyl propanoate were used as internal standard components, allowing a quantification of the volatiles investigated. The trace components were found in a range from less than 0.5 to 18 ppb. The results are discussed with regard to the biosynthesis of these volatiles. Due to the high enantiomeric purities detected, the differentiation between naturally occurring flavor compounds and synthetic racemates added to passion fruit products is realized conclusively.

The influence of sample preparation on the accuracy of 13C/12C-ratios is investigated. Dynamic headspace, simultaneous distillation-extraction and solvent extraction are used as methods of sample preparation in order to gain access to the volatiles of strawberries.

The odour characteristics of chiral 3[2H]-furanones, which are important aroma compounds, have been evaluated by sniffing the separated enantiomers through the port of a gas chromatograph (gc-sniffing). The results revealed great differences in the odour quality and thresholds of the single enantiomers. The determination of the origin of 2,5-dimethyl-4-hydroxy-3[2H]-furanone and 2,5-dimethyl-4-methoxy-3[2H]- furanone from strawberries, pineapples and commercial samples has been achieved using GC-isotope ratio mass spectrometry (GC-IRMS). For this technique to be successful, it is essential that preparative and storage procedures should not influence the isotope ratio of compound analysed; this is demonstrated to be the case for 2,5-dimethyl-4-hydroxy-3[2H]-furanone.

This paper deals with gas chromatographic separations of enantiomers on tert-butyldimethylsilylated cyclodextrins, namely heptakis(2,3-di-O-acetyl-6-O-tert-butyldimethylsilyl)-β-cyclodextrin, heptakis(6-O-tert-butyldimethylsilyl-2,3-di-O methyl)-β-cyclodextrin, and octakis(2,3-di-O-butyl-6-O-tert-butyldimethylsilyl)-β-cyclodextrin. The advantages of these cyclodextrin derivatives in comparison with common cyclodextrins are outlined. The qualities of separations using these chiral stationay phases are demonstrated for separations of Aerangis lactone by multidimensional gas chromatography with heptakis(6-O-tert-butyldimethylsilyl-2,3-di-O-methyl)-β-cyclodextrin as the main column. Furthermore, the resolution of chiral aldehydes, namely 2-methylpentanal, 2-methylbutanal, 2-phenylpropanal, and 2-methyl-3-(4-tert-butylphenyl)propanal is shown, using heptakis(2,3-di-O-acetyl-6-O-tert-butyldimethylsilyl)-β-cyclodextrin as the chiral stationary phase. The separation of homologous secondary alcohols such as 2-alkanols (C 5 -C 9 ), 3-alkanols (C 6 -C 8 ), and 1-alken-3-ols (C 5 -C 9 ) on octakis(2,3-di-O- butyl-6-O-tert-butyldimethylsilyl)-γ-cyclodextrin is described

The influence of different polysiloxane solvents on the efficiency and stereoselectivity of columns coated with mixtures of heptakis (2,3-di-O-acetyl-6-O-tert-butyldimethylsilyl)-β-cyclodextrin and the polysiloxanes was investigated. Generally, the enantioselectivity increased with decreasing polarity of the silicone solvent and/or increasing cyclodextrin concentration, with some exceptions. Thermodynamic investigations showed that a change of the diluting phase or the cyclodextrin concentration affects entropy as well as enthalpy differences between the diastereomeric cyclodextrin/solute complexes. As a consequence, a certain cyclodextrin/polysiloxane combination is superior to another only at a particular temperature.

Capillary gas chromatography coupled on-line with isotope ratio mass spectrometry (GC/IRMS) is used to determine the δ13CPDB-values of some typical peppermint oil constituents. By the method of the internal isotopic standard (i-IST), a characteristic isotopic fingerprint of authentic peppermint oil is established and used for the authenticity control of commercially available peppermint oils. Furthermore, enantioselective capillary gas chromatography in combination with IRMS (enantio-GC/IRMS) is used to prove the genuineness of peppermint oil.

Thermodynamic data, which are derived from measurements of separation factors at different temperatures for various chiral compounds, show some expected, but also some surprising effects concerning the mechanism of chiral recognition for the cyclodextrin derivatives investigated.

The enantiomeric distributions of δ- and γ-lactones from dairy products are determined by enantioselective multidimensional gas chromatography. By using heptakis(2,3-di-O-acetyl-6-O-TBDMS)-β-cyclodextrin as the chiral main column, the simultaneous stereodifferentiation of the δ- and γ-lactones C13–C18 is reported for the first time. Genuine lactones of dairy products preferably occur as (R)-enantiomers. Flavoured margarine and coconut are analysed and discussed. Reference compounds are synthesized as racemates and separated by enantioselective HPLC into the enantiomers. Chiral compounds of characteristic enantiomeric ratios are detected irrespective of the manufacturing processes used.

The direct enantioselective analysis of 3-, 4-, and 5-hydroxy fatty acids from biological material has been achieved by enantioselective multidimensional gas chromatography (enantio-MDGC) with heptakis(2,3-di-O-methyl-6-O-tert-butyldimethylsilyl)- or (2,3-di-O-acetyl-6-O-tert-butyldimethylsilyl)-β-cyclodextrin as chiral stationary phase. All the bacteria investigated produced polyesters of enatiomerically pure (R) configured compounds.

Using enantioselective multidimensional gas chromatography (enantio-MDGC) and the column combination polyethylene glycol/heptakis (2,3-di-O-acetyl-6-O-ter-butyldimethylsilyl)-β-cyclodextrin in OV 1701-vi, the chiral monoterpenoids cis/trans-rose oxides, linalol, citronellal, citronellol and terpinen-4-ol were stereoanalysed simultaneously. The method is applied to chirality evaluation of these compounds in Cymbopogon (Citronella) oils. The enantiomeric distributions are discussed as indicators to the authenticity of these essential oile

The direct enantioselective analysis of menthone, isomenthone, menthol, neomenthol, neoisomenthol and menthylacetate in Mentha oils is achieved, using multi-dimensional gas chromatography with heptakis (2,3-di-O-methyl-6-O- tert .-butyldimethylsilyl)-β-cyclodextrin in PS 268 as the chiral stationary phase.

Multidimensional enantioselective gas chromatography, employing heart-cutting from a non-chiral precolumn onto a selectivity adjusted, modified cyclodextrin coated chiral main column, permits the simultaneous stereo differentiation of the chiral major compounds of buchu leaf oil. Commercially available essential oil as well as laboratory prepared samples were directly analysed. The enantiomeric distribution of limonene, menthone, isomenthone and pulegone was investigated, and the characteristic flavour impact compounds, 3-oxo-p-menthane-8-thiol and its thiol acetate, were stereoanalysed. Their chirality evaluation is discussed as an indicator of authenticity of ‘cassis’ type fruit aromas and fragrances.

The δ13CPDB-values of some carboxylic esters from apple flavours have been determined by capillary gas chromatography, on-line coupled with isotope ratio mass-spectrometry (GC-IRMS) and compared with the isotopic ratios of some commercially available samples. For the first time, the chirospecific measurement of the isotopic ratios of 2-methylbutanoates is described. Enantioselective capillary gas chromatography (enantio-GC), GC-IRMS as well as enantio-GC-IRMS are demonstrated as sophisticated methods in monitoring the authenticity of natural flavour compounds.

Authenticity assessment of trans-anethole is deduced from (2)H/(1)H and (13)C/(12)C isotope ratios, determined by gas chromatography-isotope ratio mass spectrometry (GC-IRMS). For that purpose, self-prepared anise and fennel oils, and synthetic and "natural" samples of trans-anethole, as well as commercially available anise and fennel oils have been investigated. Authenticity ranges of (2)H/(1)H and (13)C/(12)C isotope ratios of trans-anethole were defined. Scope and limitations of the applied online GC-IRMS techniques are discussed.

Preparative resolution of the enantiomers of several chiral dihydrofuranones, known to be important flavor compounds, has been achieved by combining the use of bonded β-cyclo-dextrin as chiral stationary phase with closed-loop recycling chromatography. The purity of the separated enantiomers has been determined by chirospecific capillary GC analysis, using heptakis(2,3-di-O-methyl-6-TBDMS)-β-cyclodextrin as the chiral stationary phase.

The odor impression of the pure enantiomers of various chiral dihydrofuranones which are important flavor compounds has been evaluated by sniffing the well separated optical antipodes in the GC eluate from heptakis(2,3-di-O-methyl-6-TBDMS)-β-cyclodextrin as the chiral phase for capillary gas chromato-graphic separation. Liquid chromatographic separation has been achieved by the use of bonded β-cyclodextrin as the chiral stationary phase and methanol–water as eluent. Enantiomer separation in the latter was improved by addition of triethylammonium acetate to the eluent.

The latest analytical advances in quality assessment of flavours and fragrances are reviewed, including capillary gas chromatography (cGC)-olfactometry for the identification and sensory evaluation of important odorants by means of odour activity values, aroma extract dilution analysis and stable isotope dilution assay (SIDA). Enantioselective cGC and comparative stable isotope ratio mass spectrometry (IRMS), coupled on-line with cGC, are reported as important tools in the authenticity control of flavours and fragrances. The literature on these topics is reviewed up to the beginning of 1992. The scope and limitations of chirospecific cGC and cGC-IRMS are discussed. The trends and perspectives in the origin control of flavours and fragrances are outlined.

Phenolic 2-methylbutanoates are known to be characteristic components of various essential oils, but their optical purity is not known. Enantiomeric pseudoisoeugenyl 2-methylbutanoates have been synthesized and their sensory properties are found to depend on the optical and geometrical isomerism of the components investigated. Furthermore, (S)-2-methylbutanoates have been detected as the genuine esters from Pimpinella anisum (L.), Arnica (unknown splecies) and Pimpinella saxifraga (L.), using ester hydrolysis and subsequent enantioselective MDGC analysis of the corresponding 2-methylbutanoic acid.

Enantioselective multidimensional gas chromatography using the column combination Carbowax 20 M/heptakis-(2,3-di-O-acetyl-6-O-tert-butyldimethylsilyl)-β-cyclodextrin in OV 1701-vinyl allows the simultaneous stereodifferentiation of trans- and cis-linalol oxides (furanoid), camphor, octan-3-ol, oct-1-en-3-ol, linalyl acetate, lavandulol, terpinen-4-ol and linalol. The method is applied to commercially available as well as self-prepared essential oils of Lavandula species. Chirality evaluation is discussed in view of quality assessment of these essential oils.

cis/trans Rose oxides, linalol, citronellol and carvone are widespread natural fragrance compounds and well known among the genuine constituents of rose oils. Using enantioselective multidimensional gas chromatography (enantio-MDGC) and the column combination Carbowax 20 M/heptakis(2,3-di-O-acetyl-6-O-tert-butyldimethylsilyl)-β-cyclodextrin in OV 1701-vi the direct and simultaneous stereoanalysis of these chiral fragrance compounds is achieved. The method is applied to the chirality evaluation of cis/trans rose oxides, linalol and citronellol from authentic Bulgarian and Turkish rose oils as well as commercially available rose oils. The enantiomeric ratios of genuine constituents from rose oils are discussed as indicators of naturalness.

8-Mercapto-p-menthan-3-on, bekannt als Aromaleitsubstanz des Buchublatterols, wurde durch Addition von H2S an enantiomerenreines (R)- und (S)-Pulegon mit anschliesender flussigkeitschromatographischer Trennung stereoisomerenrein dargestellt und qualitativ sensorisch beurteilt. Mit Heptakis-(2,3,6-tri-O-methyl)-β-Cyclodextrin als chiraler stationarer HRGC-Phase werden die Streoisomeren chirospezifisch analysiert.

Heptakis(2,3-di-O-acetyl-6-O-tert-butyldimethylsilyl)-β-cyclo -dextrin proves to be a versatile chiral stationary phase for the direct differentiation of aroma-relevant enantiomers.