This paper reports the selective and sensitive voltammetric determination of L-cysteine in the presence of folic acid using ethynylferrocene modified carbon nanotubes paste electrode in 0.1 M phosphate buffer solution (pH 7.0). Using square wave voltammetry, we could measure L-cysteine and folic acid in one mixture independently from each other by a potential difference of about 410 mV for the first time. Square wave voltammetric peak current of L-cysteine and folic acid increased linearly with their concentrations in the ranges of 0.2–250.0 and 1.0–500.0 μmolL−1, respectively. The detection limits of 0.07 and 0.6 μmolL−1 were achieved for Lcysteine and folic acid, respectively. The proposed voltammetric sensor was successfully applied to the determination of L-cysteine and folic acid in real samples.
