Accurate mass analysis and structure elucidation of selenium metabolites by liquid chromatography electrospray time-of-flight mass spectrometry

摘要

In this work, we describe a procedure for the structure elucidation of selenium compounds, based on accurate mass analysis of ions by means of liquid chromatography electrospray time-of-flight mass spectrometry (LC-TOFMS). It has been applied for the identification of novel Se species from the low-molecular-weight (LMW) range fraction of selenised yeast used for food supplements. The characterization of the suspected selenised species has been based on the information obtained from: (1) accurate mass measurements of both the protonated molecules and fragments from in-source CID fragmentation; (2) (high-resolution) isotopic signatures that are characteristic of selenium-containing ions and; (3) proposed elemental compositions and their double bond equivalent (DBE) values that can be used to assist the structure elucidation of new selenium species. Different examples on the identification of non-peptide selenium species are described in detail, including two selenised compounds that have been characterized here for the first time (i.e., m/z 426 and 513). Possible elemental compositions and structures of these selenised compounds were proposed on the basis of the data collected by LC-TOFMS, and the advantages and drawbacks of the proposed approach are critically discussed. The signal-to-noise ratio obtained for the detected selenised compounds in LC-TOFMS analyses was clearly higher than using LC-ICPMS detection.