Organic selenium compounds determination in the complex matrix by the 1H-77Se HMBC method

Abstract

The development of the organic Selenium (Se) speciation assay to evaluate Se-enriched yeasts (SeYs) with high selectivity and good sensitivity is highly desired. We investigated contents of three organic Se compounds with a proton-detected 1H-77Se multiple-bond correlation (1H-77Se HMBC) method in a complex yeast matrix. The method showed quantitative correlation peaks resulting by the long-range coupling (nJ(77Se,1H), n = 2, 3) between 1H and 77Se atoms. Broadband excitation and homonuclear coupling evolution suppression can be achieved by utilizing the shaped pulse in the 77Se dimension and the constant time period, respectively. Several NMR methods were compared to improve performances of the 1H-77Se HMBC method in sensitivity. The limit of quantifications (LOQs) were 0.10, 0.11, and 0.15 mmol/L for SeMet, MeSeCys and SeCys2, respectively. Furthermore, the method can greatly raise the resolution without any separation technique compared to other one- and two-dimensional NMR and chromatographic method. The validation of the methodology showed satisfactory specificity, accuracy, precision, and linearity. The method was suitable for routine analysis, quality control and market supervision of Se species in the enriched-Se yeast.