Full Paper Voltammetry of Benzo[a]pyrene in Aqueous and Nonaqueous Media: Adsorptive Stripping Voltammetric Determination at Pencil Graphite Electrode Ertug ˘rul Keskin, Yavuz Yardım, Zühre S ¸ entürk* Yüzüncü Yıl University, Faculty of Science and Letters, Department of Analytical Chemistry, 65080 Van, Turkey *e-mail: zuhresenturk@hotmail.com Received: November 3, 2009 Accepted: January 6, 2010 Abstract A detailed study of the electrochemical oxidation of Benzo[a]pyrene (BaP) at the glassy carbon and pencil graphite electrodes was carried out in aqueous and nonaqueous media. Using square-wave stripping mode, the compound yielded a well-defined voltammetric response at pencil graphite electrode in acetate buffer, pH 4.8 at þ 1.13 V (vs. Ag/ AgCl) (a preconcentration step being carried out at a fixed potential of þ 0.70 V for 180 s). The process could be used to determine BaP concentrations in the range 0.25 – 1.25 mM, with a detection limit of 0.027 mM (6.82 mgL 1 ). The applicability to assay of spiked human urine samples was also illustrated. Keywords: Benzo[a]pyrene (BaP), Cyclic voltammetry, Adsorptive stripping square-wave voltammetry, Nonaqueous and aqueous media, Urine, Glassy carbon electrodes, Pencil graphite electrodes DOI: 10.1002/elan.200900527 1. Introduction Polycyclic aromatic hydrocarbons (PAHs) comprise a large group of high lipophilic compounds known to be carcino- genic and mutagenic agents. They are generally described as molecules which consist of three or more fused aromatic rings in various structural configurations. The carcinogenic- ity of PAHs is associated with the number of benzene rings in their structures and with their metabolic conversion to reactive electrophilic intermediates, including radical cat- ions and/or diolepoxides formed by one-electron oxidation and/or monooxygenation, respectively. Some PAHs are activated exclusively by one of these mechanisms, and others are activated by a combination of both. These carcinogenic intermediates or metabolites can covalently bind nucleophilic targets in nucleic acids (DNA and RNA) and proteins leading DNA adduct formation [1 – 5]. PAHs are introduced into the environment mainly via natural (forest fires and volcanic eruptions) and anthropogenic (fossil fuels, waste incineration, coke and asphalt produc- tion, oil refining, aluminum production, food processing and many other industrial activities) incomplete combustion processes [6]. Even extremely low concentrations of these compounds can increase the occurrence of various forms of cancer; therefore, simple and sensitive methods for their determination are of great interest [7]. Benzo[a]pyrene (BaP) (its structure is shown in Figure 1) is one of the most potent PAH carcinogens found in steel foundries, coke plants, and aluminum plants [8]. It is also present at high levels in households that rely on coal fires for cooking and heating [9]. BaP concentration marks the carcinogenic PAH levels very well in different matrices such as water, air and foodstuffs [10, 11]. Because of the widespread presence of BaP, humans are exposed to this compound via different pathways, i.e. inhalation, ingestion of contaminated food and/or water, and dermal contact. Due to the fact that PAH compounds are very hydrophobic, BaP, as well as other PAHs, tends to be stored in the fat tissue, liver and kidney. It is metabolized by mammals via a cytochrome P450-dependent monoox- ygenase and epoxide hydrolase to primary and secondary metabolites including arene oxides, diols, phenols, quinones, dihydrodiols and water soluble conjugates. It forms DNA adducts in vitro and in vivo by one-electron oxidation with reaction of the BaP cation radical at C-6 (80%) and by reaction of bay-region diol epoxides at C-10 (20%) [12 – 14]. Various analytical methods have been described for its determination together with other PAHs in complex environmental samples. The most widely used are gas chromatography with flame ionization [15, 16] or mass Fig. 1. Chemical structure of BaP. Full Paper Electroanalysis 2010, 22, No. 11, 1191 – 1199  2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim 1191