The silver amalgam film electrode in catalytic adsorptive stripping voltammetric determination of cobalt and nickel

The application of the silver amalgam film electrode (Hg(Ag)FE) of prolonged analytical applicability to the determination of cobalt and nickel by adsorptive stripping voltammetry is presented in this work. The method is based on adsorptive accumulation of analytes at the Hg(Ag)FE in a supporting electrolyte consisting of 0.1 M ammonia buffer and 50 μM cycloheksanedione dioxime. The reduction current of Co is catalytically enhanced by the presence of 0.4 M nitrite. Several key parameters of the differential pulse modulation were optimized, including pulse amplitude, accumulation potential and accumulation time. The detection limit obtained for 60 s accumulation time are estimated to be 5.8 × 10–11 M (0.0035 μg/L) Co and 2.2 × 10–10 M (0.013 μg/L) Ni. The repeatability of the peak current was 5.8% and 5.6% for Co and Ni, respectively. The calibration plots were linear from 0.01 to 7 μg/L Co and from 0.1 to 10 μg/L Ni. Finally, the Hg(Ag)FE was applied to the determination of nickel and cobalt in certified reference material with satisfactory result.