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Vanilla still remains one of the most important and widely used flavours in the food industry and is also extensively employed by fragrance and pharmaceutical manufacturing companies. Natural vanilla flavour, extracted from the pods of the tropic orchid vanilla, is considerably more expensive than synthetic vanillin. The disparity of prices between natural vanillin and that derived from other sources has given rise to many cases of fraudulent adulteration, and for more than 30 years, strenuous efforts have been made to authenticate sources of vanillin. Stable isotope analysis is one of the most powerful analytical tools to distinguish between natural vanillin and that originating from other sources. Recently, a rapid and precise method for analysis of both δ13C and δ2H values of plant methoxyl groups has been published. Here, we report an application of the method for the control of authenticity of vanillin. Carbon and hydrogen stable isotope values of the vanillin molecule and vanillin methoxyl groups of vanillin samples of different origins including authentic and synthetic samples were measured. The results clearly show that use of this approach provides a rapid and reliable authenticity assessment of vanillin. The technique used for these studies is robust and rapid, involves minimum sample preparation and requires only a small amount of vanillin sample, usually 1 mg for stable carbon and 4 mg for stable hydrogen analysis.

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

Since the ban on growth-promoting antibiotics throughout the EU essential oils are used increasingly as feed additives. In order to ensure a reliable authenticity assessment of those oils appropriate methods were developed. 2H/1H−, 13C/12C− and 18O/16O isotope ratio mass spectrometric analysis of carvacrol from origanum and savory oil, thymol from thyme oil and trans-anethole from fennel oil in combination with IRMS-analysis of minor components and differential analysis is reported. This is the only reliable method to assess the authenticity of these spice oils, provided that an adulteration with major components should be detected. The major component IRMS-measurements is a powerful tool in the authenticity assessment of savory- and thyme oil. In case of origanum and fennel oils a comprehensive analysis including major and minor component-, differential-IRMS as well as enantioselective analysis is essential.

Flavour extracts of different blackberry cultivars were investigated in a view of authenticity assessment, using multielement-/multicomponent MDGC–IRMS and enantioselective MDGC analysis. In conclusion enantioselective analysis of heptan-2-ol and trans-linalool oxide (fur.) in conjunction with multielement MDGC-C/P-IRMS analysis were proved to be useful tools in the authenticity assessment of blackberry flavours.

By reductive glyceride cleavage food fats of different origin, converted to free glycerol and to fatty alcohols of the corresponding fatty acids, were investigated. Multielement IRMS-analysis (δ13C, δ18O) of the decomposition products was performed in order to develop GC-IRMS methods to the authenticity assessment of food fats. For this reason glycerol from olive oils of definite origin, as well as glycerol of commercially available edible fats and oils, was analysed. Furthermore, the determination of 18O/16O and 13C/12C isotope ratios of commercial glycerols from different origins was achieved. In addition, δ13CV‐PDB values of fatty alcohols corresponding to genuine fatty acid moieties were measured and their usability in view of fat authenticity assessment is discussed.

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.

The determination of glycerol and 2,3-butanediol by photometric or enzymatic methods is well established. This paper reports on the direct assessment of glycerol and stereoselective analysis of 2,3-butanediol isomers in wine using capillary GC without any derivatisation. A “model wine” and commercially available wines, as well as wines of definite origin were investigated. The contents of glycerol and 2,3-butanediol and the ratio of (R,R)- and meso-2,3-butanediol were determined. Capillary GC has proved to be a reliable alternative in glycerol assessment from wine, thus a GC-IRMS method for authenticity assessment of glycerol was developed.

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.

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 recently introduced solventless extraction technique, the Stir Bar Sorptive Extraction (SBSE), was applied for the enantioselective analysis of chiral flavour compounds in strawberries and their processed products using enantioselective multidimensional gas chromatography-mass spectrometry (enantio-MDGC-MS). Using this rapid method the usual preparation steps for complex matrices such as liquid/liquid extraction, solid phase extraction or distillation techniques can be omitted. The analysed chiral compounds showed fruit-specific characteristic enantiomeric ratios, irrespective of food processing techniques employed. Hence, it is possible to differentiate the flavour of authentic and aromatised strawberry products.

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.

Young plants of Agathosma crenulata (L.) Pillans were stem fed with aqueous solutions of 2H2 and 18O/2H2-labelled monoterpene ketone precursors. The essential oil was extracted by solid phase microextraction and subsequently analysed with enantioselective multidimensional gas chromatography–mass spectrometry. Both labelled pulegone precursors were converted into corresponding labelled menthone, isomenthone and menthofuran with different enantioselectivity. Feeding experiments with 18O/2H-labelled pulegone proved an enzymatic conversion of pulegone to menthofuran and the loss of the pulegone oxygen. Stereoselective analysis of all four isopulegone stereomers using octakis(2,3-di-O-butyryl-6-O-tert-butyldimethylsilyl)-γ-cyclodextrin or heptakis(2,3-di-O-acetyl-6-O-tert-butyldimethylsilyl)-β-cyclodextrin allowed the detection of enantiopure (1S)-cis- and (1S)-trans-isopulegone (>99%) in A. crenulata and buchu samples. Labelled isopulegone is discussed as a suitable pulegone precursor. Feeding experiments regarding the biosynthesis of 3-oxo-p-menthan-8-thiol and 3-oxo-p-menthan-8-thiol acetate are also reported. 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 multidimensional gas chromatography-mass spectrometry (enantio-MDGC-MS) is a valuable tool for the differentiation of enantiomers from complex matrices when present in trace amounts. The separation of chiral compounds provides further information on the diagnosis of diseases, and on normal and abnormal biochemical pathways. The formation of the normal urinary metabolite 3-hydroxy-2-methylbutanoic acid (HMBA), excreted in abnormally high amounts in beta-ketothiolase deficiency, is not absolutely clarified. Metabolic pathways involving this metabolite are isoleucine catabolism, as well as presumably beta-oxidation of fatty acids and ketogenesis. The latter two pathways are distinguishable in their enantioselectivity. Enantioselective analysis gives further information on interfering metabolic pathways and the selectivity of the enzyme(s) forming HMBA. Different ratios of the stereoisomers of HMBA in control urine samples and patients with beta-ketothiolase deficiency were detected. Analogous to HMBA urinary 3-hydroxybutanoic acid (HBA) was investigated in several diseases. The formation of HBA and HMBA is expected to result from the same or similar metabolic pathways. Differences in the enantiomeric ratio of HMBA may originate from the enantioselectivity of different enzyme systems.

The synthesis of octakis(2,3-di-O-propionyl-6-O-tert-butyldimethylsilyl)-γ-cyclodextrin and its use as chiral stationary phase in capillary gas chromatography is described. Separation factors and thermodynamic parameters of several chiral compounds on two columns with different cyclodextrin content and different polysiloxanes as diluting phase are investigated. © 2000 John Wiley & Sons, Inc. J Micro Sep 12: 482–492, 2000

Methylcitric acid (2-hydroxybutane-1,2,3-tricarboxylic acid–MCA) is a structural analogue of citric acid, but due to an additional methyl group it is a chiral molecule with two stereogenic centers and thus four stereoisomers are conceivable. MCA occurs naturally as prominent metabolite in body fluids of patients with inherited metabolic diseases such as propionic acidemia, methylmalonic aciduria, or holocarboxylase synthetase deficiency. Therefore methylcitric acid is considered to be an important diagnostic marker for these diseases. MCA is most likely produced from accumulated propionyl-CoA in these diseases by the enzyme si-citrate synthase from the citric acid cycle; however, there are other enzymes known which could catalyze the same reaction with different stereoselectivity, such as re-citrate synthase or the more specific enzyme methylcitrate synthase, found in microorganisms. Almost all methods dealing with MCA in the literature are non-enantioselective. For that reason there is no information about occurrence of MCA enantiomers in healthy people, patients with propionic acidemia, methylmalonic aciduria, or holocarboxylase synthetase deficiency and about value of enantiomeric distribution for diagnosis and long-term treatment. The enantioselective analysis of MCA as corresponding trimethyl ester was achieved by enantioselective multidimensional gas chromatography coupled with mass spectrometry using heptakis-(2,3-di-O-methyl-6-O-tert-butyl-dimethylsilyl)-β-cyclodextrin as chiral stationary phase. The described method allows a reliable screening of MCA in complex matrices like urine without time consuming sample preparation and with mass selective detection. During this investigation urine samples from various patients and healthy controls were analyzed. As concluded, MCA is a good diagnostic marker and can be easily measured by the method presented. Only the two stereoisomers (2S,3R) and (2S,3S) were detectable in patients and healthy controls. The varying ratios of these stereoisomers cannot presently be correlated with the health status of patients, although there are some indications that this might be possible. However, the quantitative levels of MCA, determined as the ratio of MCA absolute peak area divided by 1,000 to the creatinine contents of urine samples in this investigation, showed a dependence on the state of health and MCA would thus also be a possible marker for long-term treatment. Such a substance is of major interest nowadays since there are different studies searching for such a long-term marker in propionic acidemia or methylmalonic aciduria.

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.

Maple syrup urine disease is an autosomal recessive inherited disorder of branched-chain amino acid metabolism due to deficiency of the branched-chain alpha-keto acid dehydrogenase complex. The disease was originally named after the characteristic sweet aroma, reminiscent of maple syrup, present in the body fluids of affected patients. Until now, the substance responsible for the odour has not been positively identified. Using enantioselective multidimensional gas chromatography-mass spectrometry (enantio-MDGC-MS), we could demonstrate that 4,5-dimethyl-3-hydroxy-2[5H]-furanone (sotolone), a well-known flavour impact compound present in fenugreek and lovage, was present in urine from seven patients with maple syrup urine disease. Urine samples from healthy control persons lacked sotolone. We have shown that sotolone is responsible for the characteristic odour of maple syrup urine disease and, since maple syrup also contains sotolone, the naming of this disease appears to be correct.

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)

Enantioselective multidimensional gas chromatography-mass spectrometry is a valuable tool for the enantioselective analysis of compounds from complex matrices. Samples are separated initially on a precolumn and selected substances then transferred on-line to a main-column coated with suitable chiral stationary phase for enantioselective analysis with subsequent mass selective detection. In this paper the method is used as an adjunct to urinary organic acid analysis to provide information in patients with suspected inborn errors of metabolism. Lactic acid, alpha-hydroxyisocaproic acid, 3-phenyllactic acid and 3-(4-hydroxyphenyl)-lactic acid are separated in a single run. In addition, the enantioselective analysis of pyroglutamic acid is presented. D-Enantiomers of amino acids and alpha-hydroxycarboxylic acids derived from amino acids, point to a bacterial origin whereas the L-enantiomer is predominantly of endogenous origin. Therefore the enantiomeric ratio of chiral metabolites is an important parameter for the understanding of metabolic processes.

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

The δ13CPDB and δ15NAIR values of methyl N-methylanthranilate from mandarin essential oils have been measured by capillary gas chromatography, on-line coupled with isotope ratio mass spectrometry (GC/IRMS). Cold-pressed and distilled mandarin peel oils of different origins and petitgrain oils mandarinier as well as reference substances of methyl N-methylanthranilate and methyl anthranilate were investigated. The combination of the δ13C and δ15N values is useful in the authenticity control of mandarin oils. Keywords: GC/IRMS; δ13CPDB and δ15NAIR values; methyl N-methylanthranilate; mandarin essential oil; Citrus reticulata Blanco

Maple Syrup Urine disease (USUD) is an autosomal recessive inherited metabolic disorder of branched-chain amino acid (L-valin, L-leucine, and L-isoleucine metabolism named after the characteristic smell of affected patients urine. MSUD is caused by a deficiency of the branched-chain α-keto acid dehydrogenase compex resulting in an accumulation of branched-chain aamino acids and the corresponding α-keto-and α-hydroxy acids in blood, urine and cerebrospinal fluid causing neurological damage and mental retardation. The enantioselective analysis of chiral MSUD metabolites and analysis of achiral compounds as corresponding N,O-methoxycarbonyl methyl esters by derivatization with methyl chloroformate (MCF) has been achieved simultaneusly by enantioselective multidimensional gas chromatography-mass spectrometry using heptakis (2,3-di-O-methyl-6-O-tert-butyl-dimethyl-silyl)-β-cyclodextrin as chiral stationary phase. Derivatization with MCF allows the analysis of the structurally different metabolitetes such as branched-chain-carboxylic-, α-oxo-, α-hydroxy- and α-amino acids in a single chromaatographic run. Mass selective detection immensely improves the unequivocaaal identification of metabolites even when they occur as trace compound. The described method allows a reliable screening of MSUD metabolites in patients' urine without time consuming sample preparation and is also suitable for label enrichment analysis without any methodical changes. During this investigation urine sample from three MSUD paatients were analyzed.

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 genuineness of vanilla is discussed by integral authenticity evaluation of vanillin and some characteristic minor compounds such as 4-hydroxybenzyl alcohol, vanillic acid, 4-hydroxybenzaldehyde, anisic alcohol, anisic acid, and 4-hydroxybenzoic acid, including isotopic data as well as gas chromatographic quantification of compounds analyzed. Such integral authenticity profiles are new and promising perspectives in the authenticity evaluation of genuine vanilla. Data-banks with two parameter series (isotopic data and quantification using internal standards) are suggested to be realized by interlaboratory ring tests. Keywords: Genuine vanilla; authenticity assessment; authenticitiy profiles; isotope analysis; multicomponent cGC-IRMS analysis

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 simultaneous enantioselective gas chromatographic differentiation of the chiral main compounds of lavender, neroli, petitgrain and bitter orange oil [limonene, linalool, linalool oxides (furanoid), linalyl acetate, (E)-nerolidol, α-pinene, β-pinene, terpinen-4-ol and α-terpineol] is described, using a defined mixture of heptakis(2,3-di-O-methyl-6-O-tert-butyldimethylsilyl)-β-cyclodextrin and heptakis(2,3-di-O-acetyl-6-O-tert-butyldimethylsilyl)-β-cyclodextrin as the chiral stationary phase.

Two phenomena, enantioselectivity and isotope discrimination, during biosynthesis may both serve as endogenetic parameters in the authenticity control of natural flavor and fragrance compounds, if suitable methods and comprehensive data from authentic sources are available. Enantioselective capillary gas chromatography (enan‐tio‐cGC) and comparative isotope ratio mass spectrometry (IRMS), coupled on‐line with cGC, are reported as important tools in the authenticity control of flavors and essential oils. The literature on these topics is reviewed up to the beginning of 1995. Scope and limitations of enantio‐cGC and (enantio)‐cGC‐IRMS are discussed.

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 essential oils of 10 authentic coriander samples of different origin were analyzed. Capillary gas chromatography, on-line coupled with isotope ratio mass spectrometry (cGC-IRMS) using Stabilwax as the stationary phase, was applied. Alternatively, heptakis(2,3-di-O-methyl-6-O-tert-butyldimethylsilyl)-β-cyclodextrin in PS 268 was used as the chiral stationary phase. The enantiomeric ratio and the δ 13 C PDB values of some characteristic compounds were compared with those of commercially available spices and essential oils. The influence of isotopic effects on the 6 values during the primary CO 2 fixation was eliminated by definition of a suitable internal isotopic standard (i-IST). The isotopic effects among genuine monoterpenes are, therefore, exclusively determined by the influence of enzymatic reactions during secondary biogenetic pathways.

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.

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.

Enantioselective GC analysis of 4-ethyloctanoic and 4-methylheptanoic acid, using heptakis(2,3-di-O-methyl-6-O-tert-butyldimethylsilyl)-β-cyclodextrin as the chiral stationary phase, is described and the sensory properties of several 4-alkyl-branched acids, using gas chromatography-olfactometry (GC-O) equipment and octakis(2,3-di-O-methyl-6-tert-butyldimethylsilyl)-γ-cyclodextrin as the stationary phase, are evaluated. The chirospecific analysis of various 2-, 3-, and 4-alkyl-branched acids from commercially available Roman chamomile (Chamaemelum nobile (L.) Allioni), Parmesan cheese, and subcutaneous mutton adipose tissue, using either GC-GC (MDGC) or GC-MS analytical methods, is described. © 1994 Wiley-Liss, Inc.