Hyphenated techniques for speciation of Se in biological matrices
The nutraceutical market has become overwhelmed by the presence of Se-preparates. The lack of control and legislation is problematic. As Se is both essential and toxic, information on the total concentration and species are of the utmost importance. Therefore in this work methods were developed based on the use of several state-of-the art analytical techniques to meet the needs of these speciation analysis. The species were first separated by using liquid chromatography, detection of the species was done by inductively coupled plasma mass spectrometry and electrospray ionization tandem mass spectrometry. The major species identified in yeast-based Se-supplements was Se-Methionine. Furthermore other natural food sources rich in Se were examined: Brazil nuts (containing Se- Cystine and Se-Methionine) and garlic (containing Se-Me-SeCysteine, Se-Methionine and γ-glutamyl-Se-Me-SeCysteine). In vitro gastrointestinal digestions were used to mimic the conditions during human digestions The purpose of these experiments was to study the extractability and stability of several species in the different food sources. The final goal was to identify the main urinary metabolites after consumption of Se-rich food, both natural and enriched. Liquid hromatography in combination with electrospray ionization mass spectrometry required serious sample clean-up, this drawback was overcome by using gas chromatography in combination with Mass Spectrometry. The main metabolite found was a selenosugar: Se-Methyl-N-Acetyl galactosamine.
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