Electrochemical Oxidation of L-selenomethionine and Se-methylseleno-L-cysteine at a Thiol-Compound-Modified Gold Electrode: Its Application in a Flow-Through Voltammetric Sensor.

Aflow-electrolytic cell that consists of a bare goldwire or of different thiol-compound-modified gold electrodes (such as 2,4-thiazolidinedione, 2-mercapto-5-thiazoline, 2-mercaptothiazoline, L-cysteine, thioglycolic acid) was designed to be used in a voltammetric detector to identify L-selenomethionine and Se-methylseleno-L-cysteine using high-performance liquid chromatography. Both L-selenomethionine and Se-methylseleno-L-cysteine are more efficiently electrochemically oxidized on a thiol/gold than on a bare gold electrode. For the DC mode, and for measurements with suitable experimental parameters, a linear concentration from 10 to 1600 ng·mL-1 was found. The limits of quantification for L-selenomethionine and Se-methylseleno-L-cysteine were below 10 ng·mL-1. The method can be applied to the quantitative determination of L-selenomethionine and Se-methylseleno-L-cysteine in commercial selenium-containing supplement products. Findings using high-performance liquid chromatography with a flow-through voltammetric detector and ultraviolet detector are comparable. [ABSTRACT FROM AUTHOR]