Poly(4-amino-1-1′-azobenzene-3, 4′-disulfonic acid) coated electrode for selective detection of dopamine from its interferences

Here, we described a new method for electrochemically selective detection of dopamine (DA). In this report, for the first time, electrochemical polymerization of 4-amino-1-1'-azobenzene-3,4'-disulfonic acid (acid yellow 9 dye (AY)) was carried out onto the surface of glassy carbon (GC) electrode and indium tin oxide coated electrode (ITO) from acidic solution containing AY monomers. A polymerized film of acid yellow on the surface of a glassy carbon electrode was characterized by cyclic voltammetry (CV). The redox response of the poly(AY) film on the GC electrode showed a couple of redox peak in 0.1 M sulfuric acid solution and the pH dependent peak potential was -58 mV/pH which was close to the Nernst behavior. The poly(AY) film-coated GC electrode (GC/PAY) exhibited excellent electrocatalytic activity towards the oxidations of dopamine (DA) in 0.1 M phosphate buffer solution (PBS, pH 7.0) and increased the anodic peak current three time higher than bare GC electrode. GC/PAY did not reduce the considerable overpotential for oxidation of DA when compare to bare GC electrode. However, in contrast to other polymer modified electrode, due to the strong negatively charged back bone of poly(AY) highly repelled the important interference of DA, such as ascorbic acid (AA), uric acid (UA) and reduced form of nicotinamide adenine dinucleotide (NADH) in 0.1 M PBS (pH 7.0) and did not showed any response for oxidation of these interferences. This behavior makes the GC/PAY for selective detection of DA in the presence of higher concentrations AA, UA and NADH. Using differential pulse voltammetry the calibration curves for DA were obtained over the range of 1-100 mu M with good selectivity and sensitivity. The proposed method provides a simple method for selective detection of DA from its interferences. (C) 2007 Elsevier B.V. All rights reserved.