FLOW-INJECTION ANALYSIS WITH ONLINE PRECONCENTRATION OF TRACE SELENIUM

A flow injection analysis system has been developed for the determination of very low concentrations (< 1 ng/ml) of selenium(IV). The system involves a micro column packed with a resin loaded with Bismuthiol-II sulfonate (Bis-II S) for the on-line preconcentration of trace selenium(IV) and a manifold for the quantification of selenium based on the Se-catalyzed reduction of 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H tetrazolium bromide (MTT). Selenium was selectively collected as selenotrisulfide (-S-Se-S-) on the resin by reaction with Bis-11 S, and eluted with a small volume of penicillamine solution which withdraws the selenium from the resin. Selenium thus eluted as penicillamine selenotrisulfide was introduced to the flow injection analyzer, where penicillamine selenotrisulfide catalyzes the reduction of MTT to formazan by dithiothreitol. The interference from copper ion was eliminated by the adsorption of Cu on the resin as a bathocuproine disulfonate chelate. Reliability of the present method was confirmed from the determination of selenium contents in a biological standard sample.