Polarographic and voltammetric determination of selected triazine-based azo dyes with different reactive groups

Mechanisms are suggested for the polarographic reduction of five triazinyl azo dyes differing only in their potentially reactive group, and optimum conditions are given for their polarographic and voltammetric determination. The limit of determination using a static mercury drop electrode was around 1 × 10−6 mol l−1 for last polarography and 2 × 10−8 mol l−1 for differential pulse polarography. Using a hanging mercury drop electrode, the limit of determination was around 1 × 10−8 mol l−1 for differential pulse voltammetry and around 2 × 10-10 mol l−1 for adsorptive stripping voltammetry. The reduction process of the azo group is used in all cases. Two of the dyes, viz. Cl and SCH2CH2OH derivatives, exhibit another reduction process at more negative potentials, which is shown to be due to a 2e− reduction of the leaving group/triazine bond followed immediately by a 2e− reduction of a CN bond in the triazine ring. With 3-carboxypyridyl, methoxy and amino derivatives the reduction in triazine region is overlapped by the reduction of base electrolyte.