Extraction of selenium species in pharmaceutical tablets using enzymatic and chemical methods.

This report describes the extraction of selenium species contained in pharmaceutical tablets using either enzymatic hydrolysis or sodium dodecyl sulphate extraction (SDS). The selenium species were determined by ion chromatography coupled to inductively coupled plasma mass spectrometry. In the enzymatic extraction approach, proteolytic enzymes (protease/lipase) were used in a buffer containing 75 mM Tris–HCl at pH 7.5. It was found that the extraction efficiency was significantly improved relative to the use of the SDS approach. For example, the extraction recovery was more than 80% of total Se, where selenocystine Se-methyl-selenocysteine (SeMC) and selenomethionine (SeMet) in the samples were extracted. In contrast, chemical extraction of Se using SDS gave only 60% of total Se, while only two species, SeMC and SeMet, were found. In addition, SeMC was found to be unstable and degraded through oxidation in the extraction solution. Finally, the two enzyme methods were applied to commercial pharmaceutical tablets. [ABSTRACT FROM AUTHOR]