Study of electrochemical bleaching of p-nitrosodimethylaniline and its role as hydroxyl radical probe compound

Journal of Applied Electrochemistry (Impact Factor: 2.15). 02/2011; 41(5):599-607. DOI: 10.1007/s10800-011-0268-1

ABSTRACT In the present paper, research on the electrochemical bleaching of p-nitrosodimethylaniline (RNO) in different electrolyte systems is presented with special attention to the role of RNO as a
selective hydroxyl radical probe compound. At a Ti/Pt90–Ir10 anode, RNO was found to be bleached in 0.050M sodium sulphate electrolyte due to lattice active oxygen without hydroxyl
radicals being intermediately present. In 0.050M sodium chloride, the bleaching rate was greatly enhanced due to indirect
bulk oxidation by active chlorine species, again without the presence of hydroxyl radicals in the oxidation mechanisms. Under
galvanostatic electrolysis, a linear relationship was found between the concentration of added chloride to a supporting sodium
sulphate electrolyte and the first order rate constant of the bleaching reaction, showing the importance of the indirect bulk
chlorine bleaching in chloride electrolyte systems. In this fashion both the chemically bonded active oxygen and the chemical
bulk oxidation by active chlorine species proved to be valid bleaching pathways of RNO that according to these findings cannot
be regarded as a fully selective hydroxyl radical probe compound. In addition, the difference in the mechanisms of chloride
electrolysis at Ti/Pt90–Ir10 and Si–BDD anodes was clearly demonstrated using t-BuOH as hydroxyl radical scavenger.

KeywordsElectrochemical oxidation–Bleaching of dye–Hydroxyl radical probe compound–
pNDA–Chlorine oxidation

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