CATHODIC STRIPPING VOLTAMMETRY OF COPPER-COMPLEXED REACTIVE DYES AT AHANGING MERCURY DROP ELECTRODE - REACTIVE-VIOLET-5

Reactive Violet 5 and its hydrolysis product, which is produced as a s ide product in the dyeing process, can be determined in an admixture a t sub-ppb levels by cathodic stripping voltammetry because the potenti als of their azo reduction peaks are separated sufficiently. For both dyes, at intermediate pH values the azo peak is preceded by a complexe d -copper reduction peak at a less negative potential, which aids the identification of the dyes. The use of pH 6 EDTA buffer removes the co mplexed-copper peak, as does the use of an acidic buffer (pH < 3). Thi s unusual use of EDTA as a pH buffer facilitates the determination of mixtures of the dye and its hydrolysis product.