Qualitative and quantitative speciation analysis of water soluble selenium in three edible wild mushrooms species by liquid chromatography using post-column isotope dilution ICP-MS

Speciation analysis of Se in hot water extracts of three edible wild mushroom species (Macrolepiota procera, Lepista luscina and Boletus luridus) has been performed to investigate Se species naturally occurring in wild mushrooms. Mushroom extracts have been analysed using size exclusion, reversed-phase and anion exchange chromatographies. Those chromatographic separation systems were coupled on-line to an ICP-MS, which was equipped with an octopole reaction system using H2 as reaction gas to eliminate interfering argon dimers in Se detection. Post-column isotope dilution analysis has been used on-line with the separations to quantify Se in the eluting peaks by converting conventional intensity chromatograms into mass flow chromatograms (previous adequate mathematical corrections). 78Se/77Se ratio was used, after correction of intensity signals for SeH+ formation, to quantify both total Se and individual selenocompounds. Extraction efficiencies in hot water between 47 and 91% were obtained for Se, depending on the mushroom considered. Selenomethionine was found to be the major compound of Se in the aqueous extracts of the three types of mushroom investigated. A number of unknown selenocompounds, all of them corresponding to low molecular weight species, were also detected and their Se content was quantified.