Determination of Copper(II) Ion by Differential Pulse Voltammetry Used a Glassy Carbon Electrode with a Nafion® Film

Abstract

Abstract The determination of Cu2+ by differential pulse voltammetry was carried out using a chemically modified electrode coated with a Nafion® film to the surface of a glassy carbon electrode (GC/NAF electrode). This method, which is based on the principle of ion-exchange equilibria between Nafion® and imidazole–copper(II) complex ions, is applicable to the determination of traces of Cu2+ by a measurement of the reduction current of the Cu(II) complex ions incorporated into the Nafion® film. The procedure is as follows: immerse the GC/NAF electrode in 10 cm3 of a sample solution containing traces (concentration, < 1.0 × 10−6 M) of Cu2+, 1.0 × 10−2 M of imidazole as the complexing agent, and 0.5 M of NaBr as the supporting electrolyte, and record the differential pulse voltammogram after stirring for 15 min at 25 °C. The reduction peak current obtained from this voltammogram was recoganize to be proportional to the Cu2+ concentration in the range of 1.0 × 10−7 to 1.0 × 10−6 M at pH 6.0 and 1.0 × 10−8 to 1.0 × 10−7 M at pH 7.0, respectively. The relative standard deviations for the peak currents obtained from four repeated determinations were 1.2 and 1.5% for 5.0 × 10−7 M of Cu2+ at pH 6.0 and 5.0 × 10−8 M of Cu2+ at pH 7.0, respectively. The diverse metal ions which coexist with Cu2+ at pH 6.0 did not interfere up to about a 100-fold excess of Mn2+, Co2+, Ni2+, and Cd2+, except for about a 10-fold excess of Fe3+, and about a 50-fold excess of Zn2+ for the Cu2+ concentration. This method was applied to the determination of Cu2+ in both waste- and river-water samples.