Determination of the vinylsulphone azo dye, remazol brilliant orange 3R, by cathodic stripping voltammetry Original Research Article

Remazol brilliant orange 3R shows only a voltammetric peak for the reduction of the azo group. No peak was observed for the reduction of the sulfatoethylsulfone or vinylsulfone reactive groups. The reduction of a pre-protonated azo group involving a two-electron process, gives a hydrazo derivative in acidic solution. In alkaline solution the reduction process occurs at more negative potential with the formation of an unstable hydrazo compound which decomposes via HN–NH bond cleavage and loss of a sulfato group. Optimum conditions are given for the cathodic stripping voltammetric determination of the dye in aqueous solution. The optimum accumulation potential and time were 0 V and up to 60 s, respectively. Linear calibration graphs were obtained from 30 to 300 ng ml−1 in pH 4 and 6.2 to 62 ng ml−1 in pH 10. The limit of determination obtained was 1.5 ng ml−1 (pH 10). The coefficient of variation was 2.6% (n = 7) at 62 ng ml−1 of the reactive dye.