Identification of new selenium non-peptide species in selenised yeast by nanoHPLC electrospray Q/time-of-flight-MS/MS
Résumé
A novel analytical strategy was proposed for the identification of selenium species in selenised yeast. It was based on on-line nanoHPLC electrospray hybrid quadrupole time-of-flight MS/MS analysis following a one-step fractionation of an aqueous extract by size-exclusion chromatography. The enhanced purity of the species arriving at a given moment at the detector allowed the detection of a series of compounds with the characteristic selenium isotopic pattern during a single chromatographic run. The high resolution and mass accuracy provided by the TOF analyser allowed, in combination with the double bond equivalent information and in-source fragmentation data, the determination of the empirical formulae of the detected selenium species. The identification was completed by targeted on-line fragmentation of pseudomolecular ions corresponding to the most abundant Se isotopes. Besides the identification of previously reported compounds (m/z 433, m/z 431) the data obtained confirmed the presence and allowed the structural characterization of 5 new adenine-containing selenium species (m/z 661, 613, 475, 406 and 403) along with some of their sulfur analogues. The signal-to background ratios obtained for these compounds with ES-MS detection were distinctly higher than those obtained with ICP-MS detection. © The Royal Society of Chemistry 2006.