Detection and characterization of artefact compounds during selenium speciation analysis in yeast by ICP-MS-assisted MALDI MS, oMALDI MS/MS and LC-ES-MS/MS

Abstract

Analysis of selenopeptides, isolated (and considered as pure) by 2D size-exclusion-reversed-phase HPLC, by capillary HPLC-ICP MS revealed a number of previously unreported Se-containing compounds. Their identity and origin were studied by the state-of-the art molecular mass spectrometric techniques including MALDI MS, oMALDI MS/MS and nanoLC-electrospray QTOF MS/MS. The research showed for the first time the possibility of loss of selenium from selenomethionine by degradation to vinylglycine and the formation of new Se peptides by methylation on carboxylic residues. The study substantiates claims for the use of the highest possible resolution HPLC for speciation studies. It raises concerns about misinterpretation of HPLC-ICP MS data on Se-speciation in selenised yeast since a number of peaks observed may be due to the formation of artefact compounds during some analytical procedures.