Cysteine determination via adsorptive stripping voltammetry using a bare glassy carbon electrode

Abstract

The electrochemical determination of cysteine is investigated by adsorptive stripping voltammetric detection of a copper–cysteine complex compound using a bare glassy carbon electrode. In acidic 0.1 M KNO₃ solution (pH 4), the electrochemical oxidation of this complex compound generates a characteristic anodic peak ca. −0.17 V vs. a standard mercury/mercurous sulphate reference electrode. The voltammetric response is highly reproducible within 2.1% error (n = 3). A linear dynamic range is obtained for a cysteine concentration of 1.0 μM to 10.0 μM. The sensitivity of 0.18 ± 0.006 μA μM⁻¹ and the limit of detection of 0.03 μM (n = 3) make our methodology highly applicable for practical applications. Successful determination of cysteine concentration in the presence of glutathione has also been demonstrated by the sequential determination of the concentrations of total thiol and the tripeptide alone.