The determination of cysteine at Bi-powder carbon paste electrodes by cathodic stripping voltammetry

Abstract

The determination of cysteine by means of square wave cathodic stripping voltammetry (SWCSV) is reported here for the first time at Bi-modified carbon paste electrodes (CPEs). The modified electrodes are 17% w/w metallic Bi powder mixed with CP (Bi-CPEs) and the technique is based on the enhancement of Bi surface oxidation in the presence of cysteine at a carefully chosen accumulation potential and the subsequent reduction-stripping of the product (proposed to be bismuth(III) cysteinate) by potential scanning to more negative values. The wide concentration range of 1 × 10 −6–5 × 10 −5 M for cysteine can be assessed by SWCSV using Bi-CPEs and, by appropriate choice of accumulation times, two linear response concentration regimes could be identified: 1 × 10 −6–1 × 10 −5 M (accumulation for 600 s) and 1 × 10 −5–5 × 10 −5 M (accumulation for 100 s), with estimated detection limits of 3 × 10 −7 and 2 × 10 −6 M, respectively.