77Se NMR spectroscopy for speciation analysis of selenium compounds

Abstract

Nuclear magnetic resonance (NMR) spectroscopy is widely used for the determination of the chemical structure of an organic compound. NMR spectroscopy is theoretically applicable to all metallic elements except cerium. In this chapter, we demonstrate selenium (Se) speciation in animal Se metabolites (selenometabolites) by NMR spectroscopy and review hitherto performed NMR spectroscopic studies of Se detection in biological samples. 77Se, an NMR-active isotope of Se, was directly observed, but its NMR receptivity was lower than its sensitivity in mass spectrometry. However, the use of enriched stable isotope improved the receptivity. Each selenometabolite had its own chemical shift, suggesting that the chemical shift of 77Se could be used as a fingerprint. Indirect measurement by heteronuclear multiple bond correlation (HMBC) spectroscopy with 1H nuclides was also effective for the Se speciation.