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

Abstract

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 H 2 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.