Determination of trace selenium in biological material by preconcentration and x-ray emission spectrometry

Selenium is determined in the ng g^?1 to μg g^?1 range in biological and environmental samples. A wet digestion procedure was optimized with respect to volatility losses and recovery yields, by using ⁷⁵Se metabolically incorporated into rat organs. Selenium is preconcentrated from the digestion liquid by a two-step reduction with 4 M HCl and ascorbic acid. The colloidal selenium formed is adsorbed on activated carbon and filtered on a Nucleopore membrane for measurement by energy-dispersive x-ray fluorescence. Almost complete recovery was obtained, and the detection limit was 20 ng, corresponding to 10 ng g^?1 for a 2-g sample. Biological reference materials were analyzed with satisfactory results, and the accuracy of the method was good.