Identification of the principal selenium compounds in selenium-enriched natural sample extracts by ion-pair liquid chromatography with inductively coupled plasma- and electrospray ionization-mass spectrometric detection

Selenium-enriched garlic and yeast sample extracts and digests were analyzed using ion-pair high performance liquid chromatography (HPLC) with on-line inductively coupled plasma-mass spectrometric (ICP-MS) and electrospray ionization-mass spectrometric (ESI-MS) detection. The principal selenium compounds in these samples were identified as selenomethionine, and Se-adenosyl-selenohomocysteine in yeast, and γ-glutamyl-Se-methyl-selenocysteine and possibly γ-glutamyl-selenomethionine in garlic. The compounds identified account for 85 and 90% of the total selenium content of the yeast and the garlic samples, respectively. On-line HPLC-ESI-MS selected ion chromatograms (SIC) and mass spectra of selenium compounds extracted from selenium enriched samples are presented. Limits of quantification (LOQ, defined as S/N = 10) for HPLC-ICP-MS were in the range 10–50 ng mL–1 Se in the injected extracts. LOQ values for HPLC-ESI-MS were ca. 100 times higher than those of HPLC-ICP-MS.