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 +1.15 V (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.