DETERMINATION OF COPPER(II) ION BY DIFFERENTIAL-PULSE VOLTAMMETRY USED A GLASSY-CARBON ELECTRODE WITH A NAFION(R) FILM

The determination of CU2+ by differential pulse voltammetry was carrie d out using a chemically modified electrode coated with a Nafion(R) fi lm to the surface of a glassy carbon electrode (GC/NAF electrode). Thi s method, which is based on the principle of ion-exchange equilibria b etween Nafion(R) and imidazole-copper(II) complex ions, is applicable to the determination of traces of Cu2+ by a measurement of the reducti on current of the Cu(II) complex ions incorporated into the Nafion(R) him. The procedure is as follows: immerse the GC/NAF electrode in 10 c m(3) of a sample solution containing traces (concentration, <1.0x10(-6 ) M) of Cu2+, 1.0x10(-2) M of imidazole as the complexing agent, and 0 .5 M of NaBr as the supporting electrolyte, and record the differentia l pulse voltammogram after stirring for 15 min at 25 degrees C. The re duction peak current obtained from this voltammogram was recoganize to be proportional to the Cu2+ concentration in the range of 1.0x10(-7) to 1.0x10(-6) M at pH 6.0 and 1.0x10(-8) to 1.0x10(-7) M at pH 7.0, re spectively. The relative standard deviations for the peak currents obt ained from four repeated determinations were 1.2 and 1.5% for 5.0x10(- 7) M of Cu2+ at pH 6.0 and 5.0x10(-8) M of CU2+ at PR 7.0, respectivel y. The diverse metal ions which coexist with Cu2+ at pH 6.0 did not in terfere up to about a 100-fold excess of Mn2+, Co2+, Ni2+ and Cd2+, ex cept 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 deter mination of Cu2+ in both waste- and river-water samples.