Subspeciation of nickel disulfide by carbon paste electrode voltammetry catalyzed by Ni2+

In subspeciation of sulfidic nickel, carbon paste electrode voltammetry was developed for the specific determination of Ni3S2 or NiS, but NiS2 was found to be unreactive. Ni2+ in pH 7.2 acetate solution was able to catalyze NiS2 to undergo redox reactions. The cyclic voltammogram showed two anodic peaks at -0.3 and +0.7 V and a cathodic peak at -0.6 V. The first anodic peak at -0.3 V and the cathodic peak were common among the three nickel sulfides, but the second anodic peak at +0.7 V was unique to NiS2. This peak current gave a linear dose response to NiS2 from 40 to 610 microg, with a correlation coefficient of 0.994, and a detection limit of 40 microg.