VOLTAMMETRIC BEHAVIOR OF ALIZARIN RED S ADSORBED ON ELECTROCHEMICALLYPRETREATED GLASSY-CARBON ELECTRODES

The electrochemical behavior of alizarin red S (dihydroxyanthraquinone sulfonate, ARS) adsorbed on electrochemically preanodized glassy carbo n electrodes was studied by cyclic voltammetry. The adsorption of ARS was greatly enhanced by the electrochemical pretreatment of the electr odes. The central quinone functionalities of the adsorbed ARS underwen t quasi-reversible reduction to give stable products. Oxidation of the dihydroxyl functionalities gave unstable products which underwent fur ther follow-up chemical transformation to give new electroactive speci es. The products of the chemical transformation of the oxidized specie s could be further oxidized at a more positive potential, resulting in two pairs of quasi-reversible, quinone-like redox waves. (C) 1998 Els evier Science Ltd. All rights reserved.