Abstract: A sensitive catalytic wave can be obtained in Co(Ⅱ)-DMNH(1,2-dimethyl-2-nicotinic hy-drazone ethyleneoxime)-NO₂^-system (pH=9). The voltammetric behaviour of this system is studied in this paper. Acompound NH₄Co(DMNH)(NO₂)₂was adsorbed on the surface of hanging drop mercury electrode at-0. 70 V(vs. SCE). In cathodic scanning, NO₂^-could be reduced catalytically by it at -1. 0 Vand produced a catalytic wave. If hydroxyamine exists in above base solution, the catalytic wave is also obtained, but the optimum acidity is shifted from pH 9 to 8. 2. Using latter system, the content of cobalt in biological samples was determined by adsorptive stripping voltammetry. The results of analysis were satisfactory. The detection limit of cobalt is 1×10^-10mol/L.

Key words: Voltammetric behaviour of cobalt, Determination of cobalt, 1,2-Dimethyl-2-nicotinic hydrazone ethyleneoxime