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International audience; Glutathione peroxidase 1 (Gpx1), one of the most responsive selenoproteins to the variation of selenium concentration, is often used to evaluate ”selenium status” at a cellular or organismal level. The four major types of analytical methodologies to quantify Gpx1 were revisited. They include (i) an enzymatic assay, (ii, iii) polyacrylamide gel electrophoresis (PAGE) with (ii) western blot detection of protein or (iii) inductively coupled plasma mass spectrometry (ICP MS) detection of selenium, and (iv) size-exclusion chromatography with ICP MS detection. Each of the four methods was optimized for the quantification of Gpx1 with maximum sensitivity. The methods based on the enzymatic and immunodetection offer a much higher sensitivity but their accuracy is compromised by the limited selectivity and limited dynamic range. The advantages, drawbacks and sources of error of each technique are critically discussed and the need for the cross-validation of the results using the different techniques to assure the quality assurance of quantitative analysis is emphasized.

International audience; A high efficiency chromatographic separation on a porous graphitic carbon stationary phase was developed for a large-scale separation of selenium metabolites in Se-rich yeast prior to their identification by electrospray hybrid quadrupole trap/Orbitrap mass spectrometry (Orbitrap MSn). The reversed-phase (RP) separation mode offered distinctly higher separation efficiency than the hydrophilic ion interaction (HILIC) mode. The latter was nevertheless complementary and useful to validate the detection of several compounds. The method allowed the detection of 64 metabolites including 30 SeSe or SeS conjugates (3 triple S/Se/S ones) and 14 selenoethers. 21 previously unreported metabolites were detected on the basis of the selenium isotopic pattern usually matched with the sub-ppm mass accuracy. 9 of these metabolites were subsequently identified using the multi-stage high mass accuracy (

International audience; A method for the determination of 13 volatile sulfur compounds including dimethyl sulfide, dimethyl disulfide (DMDS), carbon disulfide and other sulfides and thiols in water samples was developed. The analytes were stripped from the sample by a flow of helium and preconcentrated in a capillary cryogenic trap. This was followed by determination by gas chromatography-microwave-induced plasma atomic emission spectrometry. Detection limits ranged from 8 pg (0.4 ng l-1) for ethanethiol to 17 pg (0.9 ng l-1) for DMDS. The method was successfully applied to the quantitative analysis of fresh and sea water and after slight modifications also to different Belgian beer types and coffee powder. A system for the automated sample delivery was developed for liquid samples.