Differential-pulse voltammetric determination of molybdenum in nitrate medium in the presence of 8-hydroxyquinoline

The determination of Mo(VI) by differential-pulse voltammetry based on catalytic currents in nitrate medium is described. The existence of catalytic currents in the system Mo(VI)NO₃^? in the presence of 8-hydroxyquinoline was proved by various polarographic techniques. The optimum background electrolyte is 20 ml 0.5 M KNO₃?0.005 M HNO³ with the addition of 1 ml of 1 × 10^?2 M 8-hydroxyquinoline. The detection limit is 7 × 10^?10 M under these conditions. Cr(VI), Cu(II), Cd(II) and Pb(II) interfere when present at higher concentrations then Mo(VI) and W(VI) interferes at an equal concentration to Mo(VI). The method was successfully used in analyses of environmental samples.