SIMULTANEOUS DETERMINATION OF NICKEL(II) AND COBALT(II) BY SQUARE-WAVE ADSORPTIVE STRIPPING VOLTAMMETRY ON A ROTATING-DISK MERCURY FILM ELECTRODE

Adsorptive stripping voltammetry was used for the simultaneous determination of Ni(II) and Co(II); the metal ions were complexed with dimethylglyoxime and the complexes were adsorbed on the surface of a glassy carbon rotating disc electrode, which was pre-plated with mercury. The stripping step was carried out by using a square-wave potential-time excitation signal. An electrochemical cleaning of the mercury film was employed, enabling the same mercury film to be used for a series of measurements. The limits of detection were 12 ng l-1 for Co(II) and 14 ng l-1 for Ni(II) (for 120 s preconcentration), the relative standard deviation was typically about 2-3% (at the 1.2 mug l-1 level) and linearity held for a concentration range of at least two orders of magnitude.