Mechanism for the Electrochemical Stripping Reduction of the Nickel and Cobalt Dimethylglyoxime Complexes

Reductive coulometric stripping potentiometry, a technique not hitherto described, has been used to establish that the reduction of Ni(II) and Co(II) dimethylglyoximates, adsorbed on a mercury film electrode, is a 10-electron process. Exhaustive adsorption of Ni(II) or Co(II) complexes, in the 0-4 μg L(-)(1) concentration range, was achieved by vibrationally promoted electrolysis for 3 min of ∼25 μL volume samples, hanging under the working electrode in a nitrogen atmosphere. The adsorbed complexes were reduced by means of a constant current of 50 μA. The technique was successfully used for the calibration-free determination of Ni(II) in certified seawater and river water reference samples.