HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY OF SULFUR-CONTAINING AMINO-ACIDS AND RELATED-COMPOUNDS WITH AMPEROMETRIC DETECTION AT A MODIFIED ELECTRODE

Organic disulfides generally are not oxidized at bare electrodes under conditions that are suited to routine amperometric detection, and thiols are typically oxidized in a manner that leads to partial blockage of the surface. Modification of a carbon electrode with a film of Ru(III,IV) oxide stabilized with cyanocross-links permits the amperometric detection of cystine, cysteine, glutathione, methionine, and glutathione disulfide under conditions compatible with their chromatographic separation on a strong cation-exchange column. Detection limits of 0.2-0.6-mu-M and linear dynamic ranges of at least 1-50-mu-M were obtained. The electrode was stable for at least 11 days with a pH 1 citrate, phosphate mobile phase.