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.

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.

Compound biodegradability tests with natural microbial communities form an important keystone in the ecological assessment of chemicals. However, biodegradability tests are frequently limited by a singular focus either on the chemical and potential transformation products or on the individual microbial species degrading the compound. Here, we investigated a methodology to simultaneously analyze community compositional changes and biomass growth on dosed test compound from flow cytometry (FCM) data coupled to machine-learned cell type recognition. We quantified the growth of freshwater microbial communities on a range of carbon dosages of three readily biodegradable reference compounds, phenol, 1-octanol, and benzoate, in comparison to three fragrances, methyl jasmonate, myrcene, and musk xylene (as a nonbiodegradable control). Compound mass balances with between 0.1 to 10 mg C · liter−1 phenol or 1-octanol, inferred from cell numbers, parent compound analysis, and CO2 evolution, as well as use of 14C-labeled compounds, showed between 6 and 25% mg C · mg C−1 substrate incorporation into biomass within 2 to 4 days and 25 to 45% released as CO2. In contrast, similar dosage of methyl jasmonate and myrcene supported slower (4 to 10 days) and less (2.6 to 6.6% mg C · mg C−1 with 4.9 to 22% CO2) community growth. Community compositions inferred from machine-learned cell type recognition and 16S rRNA amplicon sequencing showed substrate- and concentration-dependent changes, with visible enrichment of microbial subgroups already at 0.1 mg C · liter−1 phenol and 1-octanol. In general, community compositions were similar at the start and after the stationary phase of the microbial growth, except at the highest used substrate concentrations of 100 to 1,000 mg C · liter−1. Flow cytometry cell counting coupled to deconvolution of communities into subgroups is thus suitable to infer biodegradability of organic chemicals, permitting biomass balances and near-real-time assessment of relevant subgroup changes. IMPORTANCE The manifold effects of potentially toxic compounds on microbial communities are often difficult to discern. Some compounds may be transformed or completely degraded by few or multiple strains in the community, whereas others may present inhibitory effects. In this study, we benchmark a new method based on machine-learned microbial cell recognition to rapidly follow dynamic changes in aquatic communities. We further determine productive biodegradation upon dosing of a number of well-known readily biodegradable tester compounds at a variety of concentrations. Microbial community growth was quantified using flow cytometry, and the multiple cell parameters measured were used in parallel to deconvolute the community on the basis of similarity to previously standardized cell types. Biodegradation was further confirmed by chemical analysis, showing how distinct changes in specific populations correlate to degradation. The method holds great promise for near-real-time community composition changes and deduction of compound biodegradation in natural microbial communities.

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 1 H NMR and HPLC-Chemiluminescence analyses.

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 (S&T-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 S&T-HS but also other techniques (solid-phase microextraction, headspace sorptive extraction, purge-andtrap headspace). The S&T-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.