A new chemically modified carbon paste electrode (CPE) was constructed and used for rapid, simple, accurate, highly sensitive, and selective simultaneous determination of cadmium and mercury using square wave anodic stripping voltammetry. The electrode was prepared using magnetic nickel zinc ferrite nanocomposite, as the modifier, in CPE. The cations Cd2+ and Hg2+ were determined after preconcentration at the surface of the modified electrode at −1.00 V vs. Ag/AgCl. Operational parameters such as pH, deposition potential, and deposition time were optimized for the purpose of determining traces of metal ions at pH 2.5. Compared with CPE, the stripping peak currents had a significant increase at the modified electrode. Under the optimal conditions, the limit of detection, based on three times the background noise, was 0.04 and 0.01 μmol L−1 for Hg(II) and Cd(II) with a 150 s preconcentration, respectively. The effects of different cations and anions on the simultaneous determination of Cd2+ and Hg2+ were investigated. The results indicated that the electrode is highly selective. Furthermore, the present method was applied to the determination of Cd2+ and Hg2+ in waste-water and several plant foodstuff samples.
