engleski

Amperometric determination of L-cysteine with an electrode based on ternary silver-copper sulfide

A simple method for amperometric determination of L-cysteine using an electrode based on ternary silver-copper sulfide is presented. Electrochemical characterizations (by cyclic voltammetry) of three electrode materials, prepared under different conditions, has revealed that the electrode based on material that consists of jalpaite (Ag3CuS2) doped with a small amount of metallic silver [1-2] (proven through the usage of XRD pattern) has shown the best electrocatalytical performance for L-cysteine oxidation. For amperometric determination, electrocatalytical oxidation of thiol group at 0.04 V vs. Ag/AgCl has been chosen. Electrochemical impedance spectroscopy has revealed that oxidation takes place on electrode surface without fouling effect, which provides a wide linear working range between 0.5 μmol dm-3 and 100 μmol dm-3. The electrode could be operated with at pH that was between 4 and 8, although the best performance has been obtained under physiological conditions (pH 7-7, 5). The calculated detection limit based on 3σ criterion was 0.025 μmol dm-3, with sensitivity of 55 nA μmol-1 dm3. In the presence of uric acid, folic acid, ascorbic acid and glucose no interference has been noticed. This amperometric sensor has shown remarkable stability and excellent reproducibility. The sensor was exploited for determination of L-cysteine in a dietary supplement with excellent recoveries.

amperometic, electroanalytic, cysteine, ternary crystal sulfides electrode

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