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Covering: up to 2019Soon after the birth of gas chromatography, mass spectrometry and olfactometry were used as detectors, which allowed impressive development to be achieved in the area of odorant determinations. Since the mid-80s, structured methods of gas chromatography-olfactometry have appeared, allowing the determination of which odor constituents play a key role in materials. Progressively, numerous strategies have been proposed for sample preparation from raw materials, the representativeness evaluation of extracts, the identification of odor constituents, their quantification, and subsequently, the recombination of the key odorants to mimic the initial odor. However, the multiplicity of options at each stage of the analysis leads to a confusing landscape in this field, and thus, the present review aims at critically presenting the available options. For each step, the most frequently used alternatives are described, together with their strengths and weaknesses based on theoretical and experimental justifications according to the literature. These techniques are exemplified by many applications in the literature on aromas, fragrances and essential oils, with the initial focus on wine odorants, followed by a short overview on the molecular diversity of key odorants, which illustrates most of the facets and complexities of odor studies, including the issues raised by odorant interactions such as synergies.

Although representativeness is often a prerequisite when sampling odors, the methods used have never been assessed from the analytical and sensory perspective simultaneously. We validate several critical innovations in the methods used to sample odors, starting with a previously developed static-and-trapped headspace (ST-HS) cell, to minimize sorptive biases and allow for thermodesorption of trapped odors. The addition of a desorption oven allows for restoration and testing of odors sampled by not only ST-HS but also other techniques (solid-phase microextraction, headspace sorptive extraction, purge-and-trap headspace). The ST-HS cell exhibits satisfactory representativeness, much higher than the three other techniques. This allows, for the first time, a proposal to use this technology as an olfactive camera to capture and restore an odor. The method was tested on a sample of a complex fresh ashtray odor.

This technical editorial provides the authors with up‐to‐date information to assure the scientific reliability of quantitative data when preparing a manuscript. It summarizes the key points of procedures that have been previously detailed in the Guidelines and Recommended Practices cited hereafter. The reader is warmly encouraged to refer to these papers published in open access.

The quantification of hydroperoxides is crucial in several areas, in particular in the fragrance domain, because they have been identified as skin sensitizers. The reference compounds necessary to calibrate the instruments have very limited availability, and require drastic storage conditions (-78 °C) due to their instability. To overcome these limitations, we propose a GC-FID approach involving their silylation, and the prediction of response factors. This procedure provides a good alternative to a full calibration down to a concentration level of 500 mg/kg, with an underestimation of about 20%. In the analysis of essential oils and fragrance concentrates, larger deviations are found; however, they are not inherent in the technique but rather in the chemistry of hydroperoxides that readily react with aldehydes to form peroxyhemiacetals, thereby decreasing the concentration of free hydroperoxides. These observations are in agreement with quantitative 1H NMR and HPLC-Chemiluminescence analyses. Copyright © 2016 John Wiley & Sons, Ltd.

This recommended practice enables the quantification of volatile compounds in flavourings to be made by gas chromatography with flame-ionization detection, without having authentic compounds available, and also in many cases it can avoid time-consuming calibration procedures. The relative-response factors (RRF) can be predicted from the molecular formula of the compound, and this approach can be applied to compounds containing the atoms C, H, O, N, S, F, Cl, Br, I, and Si, providing that the molecular formula and number of benzene rings in the analytes are known. The purity of chemically-defined flavouring substances or chromatographic standards can also be estimated using these predicted RRF, and this procedure can also be used to quantify (poly)hydroxylated compounds, after their derivatization into trimethylsilyl ethers or esters. Copyright © 2016 John Wiley & Sons, Ltd.

Limonene and linalool are major components in many essential oils, and both readily autoxidize to form terpene hydroperoxides. These hydroperoxides are sensitizers capable of causing allergic contact dermatitis, so it is important to have accurate analytical methods for them in perfumery raw materials and formulations. This laboratory has previously reported a method to detect terpene hydroperoxides based on high-performance liquid chromatography using a post-column chemiluminescence reaction. Using this method, it was shown that peroxyhemiacetals formed by reaction of terpene hydroperoxides with endogenous aldehydes exist as components in common citrus oils. This was further substantiated by NMR analysis using a variety of techniques. Some percentage of the peroxyhemiacetals can dissociate back to the corresponding parent terpene hydroperoxides and aldehydes under certain conditions which are currently not fully understood, even if the polarity of the solvating environment appear to be important. However, gas chromatographic analysis indicates that there may also be alternative degradation pathways. The presence and chemical behaviour of peroxyhemiacetals must be studied further and analytically accounted for, if meaningful results are to be obtained in the context of the dermal sensitizing potency of a sample. Copyright © 2016 John Wiley & Sons, Ltd.

The forthcoming extension of the regulated fragrance allergen number is raising a challenge: the previously developed quantification methods need to be drastically improved in terms of rapidity, without altering their reliability. This work describes a procedure based on comprehensive bidimensional gas chromatography, hyphenated with a low-cost quadrupole mass spectrometer (GCxGC-QMS). The second chromatographic dimension was operated in a dual configuration, consisting of two parallel secondary columns, one being connected to the QMS, the other to a flame ionization detector (FID). This not only allowed optimization of the chromatographic gas flows when compared to the usual single second dimension, but it also enabled the use of the FID signal to extend the quantification range from 2 to 10,000 mg/kg. The QMS was used at a low level (2-100 mg/kg), where coelutions are frequent, and the FID was used for the most abundant analytes (100-10,000 mg/kg) with a low risk of significant interferences. To assess the identity and purity of the analyte peak at low level, we propose a strategy and summarize it in a decisional tree. To our knowledge, this represents the first fully developed quantification method based on a GCx2GC-QMS/FID system. In contrast to other methods, it enables the quantification of a wide variety of analytes in fragrances in a single run, without requiring a series of sample dilutions to match the calibration range.

The intramolecular 13C composition of a molecule retains evidence relevant to its (bio)synthetic history and can provide valuable information in numerous fields ranging from biochemistry to environmental sciences. Isotope ratio monitoring by 13C NMR spectrometry (irm-13C NMR) is a generic method that offers the potential to conduct 13C position-specific isotope analysis with a precision better than 1‰. Until now, determining absolute values also required measurement of the global (or bulk) 13C composition (δ13Cg) by mass spectrometry. In a radical new approach, it is shown that an internal isotopic chemical reference for irm-13C NMR can be used instead. The strategy uses 1H NMR to quantify both the number of moles of the reference and of the studied compound present in the NMR tube. Thus, the sample preparation protocol is greatly simplified, bypassing the previous requirement for precise purity and mass determination. The key to accurate results is suppressing the effect of radiation damping in 1H NMR wh...

The persistence of synthetic cyclohexyl- and norbornyl-derived ketones was assessed by using OECD 301F and 301D biodegradation tests. While cyclohexyl-derived ketones either reached or came close to the pass level (60%) after 60 d, the corresponding norbornyl derivatives yielded significantly less biodegradation (40%). By analyzing extracts at 60 d, the key degradation products of four norbornyl derivatives were identified. Consistently, 2-bicyclo[2.2.1]heptane carboxylic acid was found as a principal degradation product with minor quantities of bicyclo[2.2.1]heptan-2-one and 2-bicyclo[2.2.1]heptane acetic acid. When the three degradation products were re-synthesized and tested individually for biodegradability, the former two were found to be ultimately biodegradable after 60 d in OECD 301D tests, thus proving non-persistence. Similarly, 2-bicyclo[2.2.1]heptane acetic acid was found to be degraded significantly, albeit with long lag phases exceeding 60 d in the case of freshwater inoculum, then ultimately reaching the pass level. On the other hand, norbornyl ketones were still only partially biodegradable in the same test. We conclude that despite the potential for ultimate biodegradation of norbornyl-derived ketones, current screening tests yield an incomplete picture of their biodegradability, particularly when applying strict OECD criteria. The appearance of long lag phases when re-testing norbornyl ketone degradation products underlines the importance of extending tests to well beyond 28 and even 60 d in the case of freshwater inocula.

Many flavour regulations around the world contain a list of so-called ‘restricted substances’ (RS), i.e. substances that occur naturally in source materials for flavourings and food ingredients with flavouring properties, but whose presence in certain foods is restricted and/or for which maximum levels are set, for example, the European regulation 1334/2008. Only a few publications refer to the determination of RS in compound flavourings or their raw materials, and the latter only concern the analysis of one or two individual RS in single essential oils. The Working Group on Methods of Analysis of the International Organization of the Flavor Industry (IOFI) has developed a method for the rapid routine determination of β-asarone, coumarin, menthofuran, methylchavicol, methyleugenol, pulegone, safrole and α- and β-thujones in flavourings and their raw materials by gas chromatography-mass spectrometry (GC-MS), using selected-ion monitoring and internal standards. The method has been evaluated by nine flavour-industry laboratories using a complex surrogate flavouring containing all of the above analytes, at concentrations that would be likely to produce levels in finished foods of around typical maximum limits for these RS. Results were obtained from a total of 15 columns and sets of analytical conditions, using 11 GC/MS instruments, with in each case a determination of the analyte in two versions of the flavouring. With reproducibility relative standard deviations (RSDR) of less than about 20%, and recoveries of 80–120%, the method performance can be considered as satisfactory for rapid routine checks on the levels of restricted substances in compound flavourings. The method is intended for flavour-industry laboratories in order for them to fulfil their obligation to inform food-industry clients of the amounts of these substances in commercial flavourings, but is not intended for their analysis in finished foods. Copyright © 2014 John Wiley & Sons, Ltd.

The quantification of volatile compounds in cosmetic products or raw materials remains problematic because of the complexity of the matrices. Two approaches were investigated on the basis of a full vaporization of analytes from a sample deposited on a cylinder of polydimethylsiloxane (PDMS) foam: (1) an internal standardization using the same calibration curve for all samples, which gives rise to unexplained peak magnifications that biases the determinations, and (2) a standard addition protocol. The latter was tested for the analysis of suspected allergens and allowed the quantification of all compounds except farnesol and Lyral®. A decision tree was proposed to ascertain peak identity and the validity of the regression curve. Using this strategy in the range of 50–100 mg/l, 91% of all individual results (except farnesol and Lyral®) in all matrices fell within a tolerance interval of ±25%. In addition, the use of disposable PDMS cylinders allowed 400 injections without polluting the injector or the column. Copyright © 2014 John Wiley & Sons, Ltd.

Over the past 15 years, chromatographic techniques with mass spectrometric detection have been increasingly used to monitor the rapidly expanded list of regulated flavour and fragrance ingredients. This trend entails a need for good quantification practices suitable for complex media, especially for multi-analytes. In this article, we present experimental precautions needed to perform the analyses and ways to process the data according to the most recent approaches. This notably includes the identification of analytes during their quantification and method validation, when applied to real matrices, based on accuracy profiles. A brief survey of application studies based on such practices is given.This article is part of the themed issue ‘Quantitative mass spectrometry’.

The performance of HPLC-UV as a means of quantifying selected furocoumarins in essential oils has been evaluated, based on a ring test validation approach. Accuracy profiles were generated, to determine bias and statistical confidence associated with determination at different concentrations, along with lower limits of quantification (LOQ). From these findings, it can be concluded that the method described may only be used in simple cases (essential oils), to measure individual furocoumarin compounds at concentrations greater than 10mg/l; the non compound-specific nature of detection by absorption in the UV range is unable to overcome the effect of interferences arising from chromatographic coelutions, such as those encountered in the analysis of complex commercial fragrance mixtures. The use of an algorithmically calculated 'spectral similarity' function, with reference to authentic standards, may be used to improve reliability in assignment and quantification.

Because a flame ionization detector (FID) is based on the combustion of analytes, we have previously shown that a good correlation exists between the relative response factors (RRFs) and the combustion enthalpies. The latter can themselves be predicted by ab initio calculation, or directly from the molecular formula. As a consequence, the RRFs can be simulated with good accuracy for all volatile constituents of flavours and fragrances. The technique is exemplified here with several applications in the field of flavours and fragrances. The composition of complex mixtures by full internal standardization is very time consuming. This task can be greatly shortened with satisfactory accuracy if predicted RRFs are used instead of the inaccurate semi-quantification (all RRFs = 1). Non-commercially available compounds normally require re-synthesis to determine their RRFs. This time-consuming step can be avoided and the compounds well quantified by using predicted RRFs. In addition, with unstable standards, measuring their RRFs or purities is impossible, whereas this issue is overcome with the present technique. We herein report the successful testing of the predicted RRFs in comprehensive GC×GC-FID. Copyright © 2012 John Wiley & Sons, Ltd.

Previous publications investigated different data treatment strategies for quantification of volatile suspected allergens by GC/MS. This publication presents the validation results obtained on “ready to inject” samples under reproducibility conditions following inter-laboratory ring-testing. The approach is based on the monitoring of three selected ions per analyte using two different GC capillary columns. To aid the analysts a decisional tree is used for guidance during the interpretation of the analytical results. The method is evaluated using a fragrance oil concentrate spiked with all suspected allergens to mimic the difficulty of a real sample extract or perfume oil. At the concentrations of 10 and 100 mg/kg, imposed by Directive 76/768/EEC for labeling of leave-on and rinse-off cosmetics, the mean bias is +14% and −4%, respectively. The method is linear for all analytes, and the prediction intervals for each analyte have been determined. To speed up the analyst's task, an automated data treatment is also proposed. The method mean bias is slightly shifted towards negative values, but the method prediction intervals are close to that resulting from the decisional tree.

Many terpenes used as fragrance compounds autoxidize when exposed to air, forming allylic hydroperoxides that have the potential to be skin contact allergens. To trigger the immunotoxicity process that characterizes contact allergy, these hydroperoxides are supposed to bind covalently to proteins in the skin via radical pathways. We investigated the formation of reactive radical intermediates from 7-hydroperoxy-3,7-dimethylocta-1,5-dien-3-ol and 2-hydroperoxylimonene, responsible for the sensitizing potential acquired by autoxidized linalool and limonene. Both compounds were synthesized through new short and reproducible synthetic pathways. The hydroperoxide decomposition catalyzed by Fe(II)/Fe(III) redox systems, playing a key role in degradating peroxides in vivo, was examined by spin-trapping-EPR spectroscopy. Alkoxyl and carbon-centered free radicals derived from the hydroperoxides were successfully trapped by the spin-trap 5,5-dimethyl-1-pyrroline N-oxide, whereas peroxyl radicals were characterized by spin-trapping studies with 5-diethoxyphosphoryl-5-methyl-1-pyrroline N-oxide. Using liquid chromatography combined with mass spectrometry, we demonstrated the formation of adducts, via radical mechanisms induced by Fe(II)/Fe(III), between the hydroperoxides and N-acetylhistidine methyl ester, a model amino acid that is prone to radical reactions. Free radicals derived from these hydroperoxides can thus induce amino acid chemical modifications via radical mechanisms. The study of these mechanisms will help to understand the sensitizing potential of hydroperoxides.

Fragranced consumer products are generally formulated together with surfactants. In application, these products are often highly diluted with water. Analyzing trace amounts of fragrance ingredients in such mixtures is challenging and usually requires either time-consuming sample cleanup or extensive cleaning of the trapping device to avoid memory effect and cross-contamination between samples. To overcome these limitations, a new disposable extraction device has been developed to be used in combination with a thermodesorption-GC-MS unit. Made of PDMS foam cylinders, it efficiently extracts trace amounts of hydrophobic compounds from complex aqueous solutions and provides an online sample cleanup, thanks to the controlled desorption temperature, which allows retaining the low volatile constituents of the matrix within the absorptive foam. Combined with a stable isotope dilution assay, accurate quantifications of Cetalox(®), Muscenone™, Helvetolide(®), Polysantol(®), Dartanol, and Myrrhone(®) from aqueous solution containing surfactant and from water from the aeration tank of a sewage plant were successfully conducted. LOQ varied between 1 and 25 ppb (20% confidence interval, α = 0.1).

Simultaneous distillation-extraction (SDE) combines, in a single step, hydro-distillation of volatiles from a sample with continuous solvent extraction of the solutes dissolved in the aqueous distillate. The solvent extract containing the isolated flavour volatiles can be subsequently analysed by gas chromatography. The technique is applicable to compounds possessing a wide range of volatility, but it is suitable neither for compounds of low volatility (e.g. vanillin), nor for highly volatile materials (e.g. methanethiol). The present guidelines concern the isolation of flavouring substances by simultaneous distillation-extraction (SDE), based on the experience of the authors in laboratories of the flavour industry. Copyright © 2014 John Wiley & Sons, Ltd.

The enforcement of the REACH regulation in the fragrance domain has created new challenges for the analytical and physical chemist. Many chemicals used as perfumery ingredients are hydrophobic, because low-polar compounds exhibit a higher substantivity (i.e. persistence after application) than do polar compounds. As a result, the usual protocols are often unsuitable and new methods must be developed. Biodegradation studies sometimes call for the quantifi cation of traces of such hydrophobic analytes in complex media (e.g. waste water, aqueous surfactant solutions). Existing sample preparation techniques are either ineffi cient or time consuming. A new approach is proposed, based on single-use absorbants, which allows accurate quantifi cation down to the 100 ppb range. This extremely simple technique allows good throughput analyses. Determining the environmental profi le of a compound requires the determination of some physical constants. Among these, solubility in water can be obtained from theoretical models or experimentally, but the resulting values may greatly diff er as a function of the model or the protocol. Several experimental approaches are critically discussed and compared with a refer- ence technique. The air-to-water partition coeffi cients are determined by using an improved version of the previously devel- oped static-and-trapped headspace technique. Copyright © 2009 John Wiley & Sons, Ltd. hydrophobic compounds in the presence of surfactants and in the measurement of physical constants. Each of these topics will be later reported in detail in separate papers. Two compounds, Cetalox® and Polysantol,® are used here to illustrate these devel- opments, as they are important constituents of compounded fragrances. They are representative of the amber and sandal- wood families, respectively, and both are hydrophobic.

In this study, usual methods commonly applied to report the quantitative composition of flavours, fragrances and essential oils were compared. The MS determinations without response factors exhibited a lack of accuracy and reproducibility. FID provided better results, but the determinations were still unsatisfactory. The best results were obtained by true internal standardization in MS and FID, which is time-consuming for mixtures composed of many constituents. The use of a response factor database was thus proposed and validated by testing the response dependence on GC parameters, using an experimental design. Very low time variations were observed. Under standard GC conditions, the determination of a model mixture with four different instruments exhibited a mean bias of < 3.4%.

The intramolecular (13)C composition of a molecule retains evidence relevant to its (bio)synthetic history and can provide valuable information in numerous fields ranging from biochemistry to environmental sciences. Isotope ratio monitoring by (13)C NMR spectrometry (irm-(13)C NMR) is a generic method that offers the potential to conduct (13)C position-specific isotope analysis with a precision better than 1‰. Until now, determining absolute values also required measurement of the global (or bulk) (13)C composition (δ(13)Cg) by mass spectrometry. In a radical new approach, it is shown that an internal isotopic chemical reference for irm-(13)C NMR can be used instead. The strategy uses (1)H NMR to quantify both the number of moles of the reference and of the studied compound present in the NMR tube. Thus, the sample preparation protocol is greatly simplified, bypassing the previous requirement for precise purity and mass determination. The key to accurate results is suppressing the effect of radiation damping in (1)H NMR which produces signal distortion and alters quantification. The methodology, applied to vanillin with dimethylsulfone as an internal standard, has an equivalent accuracy (1‰) to that of the conventional approach. Hence, it was possible to clearly identify vanillin from different origins based on the (13)C isotopic profiles.

We previously showed that the relative response factors of volatile compounds were predictable from either combustion enthalpies or their molecular formulae only 1. We now extend this prediction to silylated derivatives by adding an increment in the ab initio calculation of combustion enthalpies. The accuracy of the experimental relative response factors database was also improved and its population increased to 490 values. In particular, more brominated compounds were measured, and their prediction accuracy was improved by adding a correction factor in the algorithm. The correlation coefficient between predicted and measured values increased from 0.936 to 0.972, leading to a mean prediction accuracy of ± 6%. Thus, 93% of the relative response factors values were predicted with an accuracy of better than ± 10%. The capabilities of the extended algorithm are exemplified by (i) the quick and accurate quantification of hydroxylated metabolites resulting from a biodegradation test after silylation and prediction of their relative response factors, without having the reference substances available; and (ii) the rapid purity determinations of volatile compounds. This study confirms that Gas chromatography with a flame ionization detector and using predicted relative response factors is one of the few techniques that enables quantification of volatile compounds without calibrating the instrument with the pure reference substance.

A method is described for the analysis of suspected volatile allergens in products containing high molecular weight or non-volatile compounds such as plant extracts, solid and liquid detergents, shampoos, etc. The method is based on dissolution/extraction of the sample followed by direct injection in a programmed temperature vaporizing inlet, the liner of which contains PDMS foam to retain the high molecular weight non-volatile material. The liner is automatically replaced after each injection, by an automated liner exchange device. Analysis is done by GC-MS operated in the retention-time locked mode. The figures of merit are illustrated with the analysis of some real samples.

Methods for the quantitative analysis of perfume compounds in shampoo were developed using SPME (solid-phase microextraction). The method development started with the extraction of the perfume compounds from water, and subsequently from shampoo aqueous dispersion. It was observed that the addition of salts decreased the extraction efficiencies with the concentration of shampoo in water as low as 0.1% in contrast to the effect of the salt in water. Step-by-step optimization to increase extraction efficiency and minimize matrix effect was investigated. Dilution of shampoo with water was found to be an efficient method for quantification. It decreased the viscosity of the shampoo and increased the concentration of free analytes. Largely diluted shampoos enabled an efficient SPME extraction and allowed the use of a unified calibration applicable to different types of shampoo. The exhaustive SPME extraction of small amounts of sample, e.g. 50 µl, provided another fast quantitative method. This unprecedented work presents quantitative methods for the analysis of perfume compounds in shampoo. This research extends the knowledge of perception and reconstitution of perfume compounds in shampoo, and facilitates development of new detergent products. Copyright © 2006 John Wiley & Sons, Ltd.

The present work makes the first attempt to take into account adsorptions in the determination of partition coefficients by modeling the multiple headspace extraction (MHE) process. Modeling a six-step MHE procedure of a homologous series of methyl ketones revealed that their adsorption-desorption on the walls was the rate-limiting step. Moreover, a comparison between experimental and predicted MHE plots shows that only the last MHE points were affected by adsorption phenomena. Using cell materials with the lowest sorptive properties, partition coefficients were then accurately calculated from the first four MHE steps. This kinetic approach supports previous work in which adsorptions were lowered owing to the choice of sampling cell materials. It also justifies some reproducibility limitations of the MHE quantification procedure mentioned in the literature.

Air-to-water partition coefficients are experimentally determined using a multiple headspace extraction procedure and an automated headspace cell. The approach is first validated with 2-butanone and then applied to a homologous series of methyl ketones. As adsorptions of the most hydrophobic compounds occurred in the sampling cell, technical improvements have been tested. This study represents the first attempt to overcome analyte adsorptions by studying and minimizing the effect of the cell's adsorption of hydrophobic analytes on the determination of their partition coefficients. The present method allows the measurement of several analytes at the same time, in the ppm range, without calibration, and with a limited manpower.

Commercial interfaces for multidimensional gas chromatography (MDGC) are based either on a valve or a pneumatic switching between columns. Both exhibit significant drawbacks and only few suppliers exist. An extremely simple interface has been set up to overcome these limitations without requiring any pneumatic control or valves switching. This new MDGC design is based on the cryo-control of the analyte transfer from the first to the second column through two cool strands of a capillary. This technique is simple to implement and does not require any special column connections. Applications involve non-polar/polar phase combinations, as well as chiral analysis, hyphenation to a conventional mass spectrometer, and olfactometric detection. In contrast to conventional MDGC configuration, the present configuration allows the use of a single oven to operate both columns at different temperatures.

An evaluation of comprehensive two-dimensional (2D) gas chromatography (GCxGC) was performed to assess its suitability for the analysis of volatile fragrance components, recognized by the European Commission's Scientific Committee on Cosmetics and other Non-food Products (SCCNFP) as possible skin sensitizers. The 24 volatile components listed by the SCCNFP were baseline-resolved or better within one 30 min analysis. High-quality calibration data for standard mixtures were obtained, with R-2 > 0.998 over the concentration range 2-1000 mg/l. However, the analysis of small spiked amounts of target compounds in truly complex fragrances was problematic, due to uncertainty in component assignment. The benefits and limitations of GCxGC are reported, and a discussion of the proposed directions for the solution of this analysis is provided.

The European legislation requires that fragranced products are evaluated for their content in 24 compounds that are suspected to be skin sensitizers. Their quantitation in fragrance concentrates may not be achieved with GC-flame ionization detection (FID), due to the complexity of these mixtures and even comprehensive GC-FID does not provide sufficient resolution. This paper reports the first example of quantitation based on the hyphenation of comprehensive GC with a low-cost quadrupole MS. A detection frequency of 30.7 Hz can be obtained by monitoring a single ion. This allows a satisfactory evaluation of the area sum over the 2-3 modulations of a given compound and linear calibration curves are obtained. Analyses are completed within 35 min.

Recent changes in European legislation require monitoring of 24 volatile compounds in perfumes as they might elicit skin sensitization. This paper reports a GC-MS quantitation procedure for their determination in fragrance concentrates. GC and MS conditions were optimized for a routine use: analysis within 30 min, solvent and internal standard selection, and stock solution stability. Calibration curves were linear in the range of 2-100 mg/L with coefficients of determination in excess of 0.99. The method was tested using real perfumes spiked with known amounts of reference compounds.

A multisniffing system has been developed to allow three panelists to simultaneously participate in a GC-olfactometric analysis. This device, associated with a computerized data treatment, allows shortening CHARM and GC-"SNIF' analyses to less than 1 week and less than 1 day, respectively. The program was developed as an extension of an existing commercial chromatography data system, as usual GC processing functions are suited to the treatment of olfactograms (plots of odor response versus GC elution time). Because of the improved algorithm, the consequences of gaps in coincident responses were minimized, and the systematic use of a panel improved the repeatability of CHARM olfactograms. Comparing both methods, GC-SNIF repeatability appears to be higher than that of CHARM, as the former method uses a larger panel, but in a shorter lapse of time.

Many fragrance terpenes autoxidize yielding allylic hydroperoxides that are strong skin allergens. These chemicals are supposed to bind through radical reactions to proteins in the skin to start the immunotoxic process characterizing skin sensitization, and further allergic contact dermatitis. In order to get more insight into this reactivity, we investigated the chemical behavior of the allylic hydroperoxides responsible for the allergenicity of autoxidized limonene and linalool. We studied by liquid chromatography-mass spectrometry the reactivity in Fe(II)/Fe(III) systems, able to degrade peroxides in vivo, toward amino acids prone to radical reactions, together with glutathione. We validated that carbon radicals issued from these compounds alter directly the lateral chain of some of the amino acids tested forming adducts via radical processes. However, in parallel, due to the high oxidative strength of the media, we show that redox processes can also be induced and engender chemical modifications on the amino acids themselves. Amino acids chemically modified by the oxidant stress can then react with radicals issued from the hydroperoxides through what we call a “non-direct” reactivity process. Understanding protein binding processes to allergenic allylic hydroperoxides needs thus to consider both covalent binding of carbon radicals to the amino acids and additional oxido-reduction processes contributing to their sensitizing potential.

Reporting the composition of complex mixtures by “semi-quantification” after GC/FID gives rise to large biases [1]. We have previously shown that the relative response factors (RRFs) can be predicted from combustion enthalpies, themselves predicted by ab initio calculation, or from molecular formulae [2]. Therefore, the RRFs can be simulated with good accuracy for all volatile constituents of flavors and fragrances. The usefulness of such calculated RRFs is exemplified here with three different quantification cases that would be time-consuming when using conventional internal standardization, or not feasible without the pure standards.

Together with a brief history of the development of simultaneous distillation–extraction (SDE), this review intends to provide the reader with practical guidelines that can be drawn from the literature, and to help the analyst in the choice of optimum experimental conditions adapted to a given sample preparation problem. This paper starts from the original apparatus of Likens and Nickerson, includes designs for micro-scale experiments, and ends up with the version operating under vacuum, and another for large-scale operations. The question of artifact formation is covered, together with proposed solutions for their prevention. Examples are given from applications in the field of flavours, fragrances and the environment. To better illustrate capabilities and limits of SDE, comparisons of SDE with other techniques of sample preparation are presented. Copyright © 2001 John Wiley & Sons, Ltd.

In a previous publication, a preparative apparatus was developed and optimized for simultaneous distillation–extraction (SDE) based on a theoretical model. In this paper, its performances were tested under various working conditions using a model mixture of flavourings. Separations were achieved at boiling water temperature as well as under mild conditions, which reduce artefact formation (room temperature, reduced pressure). High recoveries were obtained for batch experiments, but the boiler can also be fed from an external tank for continuous operations. This permits consideration of the preparative isolation of volatiles on a laboratory scale for subsequent fractionation and analysis, as well as industrial scale operations. Examples are given for real food flavours: one-step preparation and isolation of a reaction flavour, isolation of yoghurt and coffee flavourings, recovery of natural benzaldehyde from wastewater. In addition, the use of a food-grade solvent to achieve SDE isolation yields an ‘edible’ extract which can be reincorporated into a food without elimination of the solvent. Copyright © 1998 John Wiley & Sons, Ltd.

Simultaneous distillation−extraction (SDE) is routinely used by analysts for sample preparation prior to gas chromatography. As the GC profile of the isolated volatiles must be representative of th...

A new headspace-GC-sniffing method is proposed. Using a recently developed headspace cell, the vapor phase is collected under conditions that mimic well those of an aroma above a food. Data treatment is based on detection frequency, rather than on perceived intensity or successive dilutions as used in other approaches. Repeatability appears satisfactory, and independent panels are even able to generate similar aromagrams, without training prior to the analysis. Using a minimum of six assessors, this technique seems to be more reliable than classical ones. To compare detection frequencies between two aromagrams, an estimation of the least significant difference is given. A theoretical justification of this approach is suggested, on the basis of determination of detection thresholds. Keywords: Headspace-GC-sniffing; impact odorants; detection frequency

Yogurt exhibits a delicate and low intense flavor which requires mild sample isolation techniques and sensitive identification means. This paper decribes the application of two new flavor separation techniques: combined static and dynamic headspace, and preparative simultaneous distillation−extraction under vacuum. Of the 91 components identified by mass spectrometry, 21 were found to have a major impact on the aroma using a new method for the treatment of GC−sniffing data. One of these compounds, 1-nonen-3-one, was identified by spectral means for the first time in a flavor. Its odor detection threshold of 8 pg/kg appears to be one of the lowest among known flavor compounds. On the basis of the peak areas of yogurt and milk aromagrams, some compounds seem to be already present in milk, others appear to be generated by the strains. Keywords: Yogurt aroma; headspace; GC−olfactometry; impact-compound; composition

The degradation of Romandolide ([1-(3',3'-dimethyl-1'-cyclohexyl)ethoxycarbonyl] methyl propanoate), a synthetic alicyclic musk, by activated sludge inocula was investigated using both the manometric respirometry test OECD 301F and the CO₂ evolution test. In addition to measuring its biodegradability, key steps of the upper part of the metabolic pathway responsible for Romandolide degradation were identified using extracts at different time points of incubation. Early metabolism of Romandolide yielded ester hydrolysis products, including Cyclademol (1-(3,3-dimethylcyclohexyl)ethanol). The principal metabolites after 31 days were identified as 3,3-dimethyl cyclohexanone and 3,3-dimethyl cyclohexyl acetate. Formation of 3,3-dimethyl cyclohexanone from Cyclademol by sludge was confirmed in subsequent experiments using Cyclademol as a substrate, indicating the involvement of an oxygen insertion reminiscent of a Baeyer-Villiger oxidation. Further mineralization of 3,3-dimethyl cyclohexanone was also confirmed in subsequent studies. Three steps were thus required for complete biodegradation of the alicyclic musk: (1) successive ester hydrolyses leading to the formation of Cyclademol with concomitant degradation of the resulting acids, (2) conversion of Cyclademol into 3,3-dimethyl cyclohexanone, and (3) further mineralization via ring cleavage.

Fragranced consumer products are generally formulated together with surfactants. In application, these products are often highly diluted with water. Analyzing trace amounts of fragrance ingredients in such mixtures is challenging and usually requires either time-consuming sample cleanup or extensive cleaning of the trapping device to avoid memory effect and cross-contamination between samples. To overcome these limitations, a new disposable extraction device has been developed to be used in combination with a thermodesorption-GC-MS unit. Made of PDMS foam cylinders, it efficiently extracts trace amounts of hydrophobic compounds from complex aqueous solutions and provides an online sample cleanup, thanks to the controlled desorption temperature, which allows retaining the low volatile constituents of the matrix within the absorptive foam. Combined with a stable isotope dilution assay, accurate quantifications of Cetalox(®), Muscenone™, Helvetolide(®), Polysantol(®), Dartanol, and Myrrhone(®) from aqueous solution containing surfactant and from water from the aeration tank of a sewage plant were successfully conducted. LOQ varied between 1 and 25 ppb (20% confidence interval, α = 0.1).

In a previous report, we validated the use of a database that compiled the relative response factors of flavor and fragrance compounds under standard GC conditions for a flame ionization detector. Here we investigate the prediction of unknown response factors from the molecular structure by using combustion enthalpies. In a first step, this enthalpy was well-predicted with either ab initio calculation or multiple linear regression based on the molecular formula. In a second step, good correlation was observed between these combustion enthalpies and experimental relative response factors, and so the response factors were predictable from only the molecular formula. With a database of 351 compounds, about 60% of them exhibited a difference of less than 5% between the predicted and experimental relative response factors and about 80% exhibited a difference of less than 10%.

Quantitative isotopic C-13-NMR at natural abundance recently became a new tool for the authentication of natural flavours. In contrast to isotopic-ratio mass spectrometry, which yields the global C-13/C-12 ratio of a molecule, isotopic C-13-NMR allows the determination of isotopic ratios of each spectroscopically differentiable carbon site. Since it requires a significant amount of the purified analyte, an optimized vanillin isolation procedure is presented here. It involves an accelerated solvent extraction of beans, a fat removal step and a subsequent medium-pressure isolation of the vanillin peak on a reusable reverse-phase column, using mostly water as a mobile phase (97%). The overall recovery from the bean extract is 90%. The procedure was automated as much as possible and checked against the risk of isotopic fractionation. The overall protocol was demonstrated to be suitable for isotopic measurements. Copyright (C) 2010 John Wiley & Sons, Ltd.

As a result of a positive response to a dithiocarbamate test, the sulphur content of caper volatiles has been investigated by GC-MS. In addition to sulphides, isothiocyanates and other flavour molecules, elemental sulphur (S8) was identified for the first time in a non-processed food. This paper presents the primary description of the aromatic bud which is widely consumed in Mediterranean countries. The organoleptic profiles of uncommon thiocyanates, nitriles and of the elemental sulphur are presented.

The simultaneous distillation—extraction (SDE) system developed by Likens and Nickerson (ASBC Proceedings, 1964, p. 5) and modified by Godefroot, Sandra and Verzele [J. Chromatogr., 203 (1981) 325] is one of the most popular methods currently used to isolate volatile components from a matrix prior to gas chromatographic analysis. Since it leads to a thermal generation of artefacts, the device has been improved in the present work to allow isolation between 20 and 40°C under vacuum. The system was closed and made airtight by means of a valve under static vacuum to avoid volatile losses. These conditions require the use of solvents with a boiling point close to that of water and the temperature must be electronically regulated. The absence of artefact generation was tested with linalyl acetate, honey and a Maillard model reaction. The recovery yields of classical SDE and SDE under vacuum were found to be similar.

The volatiles of faham leaves, a flavoring and medicinal plant of the Indian Ocean, have been analyzed by GC/MS. Besides the main compound, coumarin, 99 minor components were identified after enrichment with a preparative capillary chromatograph. The presence of diterpenes (kaurenes and phytadienes) was confirmed using GC/FTIR. This study represents the first description of the volatile fraction of faham. A sensory evaluation of the leaves of faham used in rums and infusions is also given.

Many modulation systems in comprehensive 2D GC (GC x GC) are based on cryogenic methods. High trapping temperatures in these systems can result in ineffective trapping of the more volatile compounds, whilst temperatures that are too low can prevent efficient remobilisation of some compounds. To better understand the trapping and release of compounds over a wide range of volatilities, we have investigated a number of different constant temperature modulator settings, and have also examined a constant temperature differential between the cryo-trap and the chromatographic oven. These investigations have led us to modify the temperature regulation capabilities of the longitudinally modulated cryogenic system (LMCS). In contrast to the current system, where the user sets a constant temperature for the cooling chamber, the user now sets the temperature difference between the cryo-trap and the chromatographic oven. In this configuration, the cooling chamber temperature increases during the chromatographic run, tracking the oven temperature ramp. This produces more efficient, volatility-dependent modulation, and increases the range of volatile compounds that can be analysed under optimal trap-and-release conditions within a single analytical run. This system also reduces cryogenic fluid consumption.