Determination of Selenium in Biological Materials by Gas Chromatography

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Abstract
A simple and practical method has been developed for determining specific forms of selenium in biological materials. The procedure is based on the selective chelation of tetravalent selenium with 4-nitro-o-phenylenediamine to form 5-nitroplazselenol, which is measured by electron-capture gas chromatography. Organoselenium and selenite (Se IV) are determined by digesting the sample in concentrated nitric acid, and total selenium is determined by further treatment of the digest with hydrochloric acid. The difference between the two values obtained represents the selenate (Se VI) content. Selenium recovery ranges from 75 to 90% and is assessed by using a 75Se-labeled tracer for liquid scintillation spectrometric assay. Gas-chromatographic conditions permit detection of selenium concentrations below 1 ppb. Mean deviation and relative accuracy average 2.3 and 3.4%, respectively. The method has been used in human population studies to assess selenium-mercury correlations and to examine the selenium content and form in specific protein fractions of fish muscle.