Electrocatalytic determination of l-cysteine using a modified carbon nanotube paste electrode: Application to the analysis of some real samples

The electrooxidation of l-cysteine (l-Cys) was studied using a benzoylferrocene (BF) modified multi-wall carbon nanotube paste electrode (BFCNPE) using cyclic voltammetry (CV), square wave voltammetry (SWV) and chronoamperometry (CHA). Under optimum pH in CV the oxidation of l-Cys occurs at a potential about 215 mV less positive than that at the surface of unmodified carbon paste electrode. The catalytic oxidation peak currents were dependent on the l-Cys concentration and a linear calibration curve was obtained in the range 0.7–350.0 μmol/L of l-Cys with SWV method. The detection limit (3σ) was determined as 0.1 μmol/L. This method was also used for the determination of l-Cys in some real samples.