Microdetermination of selenium in protein fractions isolated by analytical methods

A method has been developed for the determination of selenium associated with proteins in chromatographic fractions, in polyacrylamide gels, and on nitrocellulose membranes after transfer. This method involves the complete digestion of samples in the purest nitric and perchloric acids and takes advantage of the specificity afforded by the 99% pure 2,3-diaminonaphthalene. The use of these and other reagents of highest purity produces very low blank values and allows a detection limit as low as 0.76 picomoles (60 picograms) of selenium. Quantitative recoveries of selenium in glutathione peroxidase and low coefficients of variation were obtained.