Voltammetric Studies on the Potent Carcinogen, 7,12-Dimethylbenz[a]anthracene: Adsorptive Stripping Voltammetric Determination in Bulk Aqueous Forms and Human Urine Samples and Detection of Dna Interaction on Pencil Graphite Electrode

Abstract

7,12-Dimethylbenz[a]anthracene (DMBA), is a widely studied polycyclic aromatic hydrocarbon that has long been recognized as a very potent carcinogen. Initially, the electrochemical oxidation of DMBA at the glassy carbon and pencil graphite electrodes in non-aqueous media (dimethylsulphoxide with lithium perchlorate) was studied by cyclic voltammetry. DMBA was irreversibly oxidized in two steps at high positive potentials, resulting in the ill-resolved formation of a couple with a reduction and re-oxidation wave at much lower potentials. Special attention was given to the use of adsorptive stripping voltammetry together with a medium exchange procedure on disposable pencil graphite electrode in aqueous solutions over the pH range of 3.0-9.0. The response was characterized with respect to pH of the supporting electrolyte, pre-concentration time and accumulation potential. Using square-wave stripping mode, the compound yielded a well-defined voltammetric response in acetate buffer, pH 4.8 at +1.15V (vs. Ag/AgCl)(a pre-concentration step being carried out at a fixed potential of +0.60 V for 360 s). The process Could be used to determine DMBA concentrations in the range 2-10 nM, with an extremely low detection limit of 0.194 nM (49.7 ng L-1). The applicability to assay of spiked human urine samples was also illustrated. Finally, the interaction of DMBA with fish sperm double-stranded DNA based on decreasing of the oxidation signal of adenine base was studied electrochemically by using differential pulse voltammetry with a pencil graphite electrode at the surface and also in solution. The favorable signal-to-noise characteristics of biosensor resulted in low detection limit (ca. 46 nM) following a 300-s interaction. These results displayed that the electrochemical DNA-based biosensor could be used for the sensitive, rapid. simple and cost effective detection of DMBA-DNA interaction. (C) 2009 Elsevier B.V. All rights reserved.