Electrochemical Determination of Diclofenac Sodium in Aqueous Solution on Cu-Doped Zeolite-Expanded Graphite-Epoxy Electrode Florica Manea,* a Monica Ihos , b Adriana Remes , a Georgeta Burtica, a Joop Schoonman c a “Politehnica” University of Timisoara, P-ta Victoriei no.2, 300006 Timisoara, Romania b National Research and Development Institute for Industrial Ecology, sos. Pandurilor, no. 90–92, sector V, 050663, Romania c Delft University of Technology, Department of Chemical Engineering ChemE 2600 GA Delft, The Netherlands *e-mail: florica.manea@chim.upt.ro; adriana.remes@chim.upt.ro Received: January 29, 2010; & Accepted: March 18, 2010 Abstract The electrochemical oxidation and determination of diclofenac sodium (DCF) at Cu-doped zeolite-modified ex- panded graphite-epoxy composite (CuZEGE) electrode was evaluated for a new alternative of quantitative deter- mination of sodium diclofenac in aqueous solutions. Cyclic voltammetry was used to characterize the electrochemi- cal behaviour of the electrode in the presence of diclofenac sodium in a 0.1 M NaOH supporting electrolyte. This modified electrode exhibited electrocatalytic effect towards sodium diclofenac oxidation, allowing its determination in aqueous solution. The linear dependence of the current versus diclofenac concentration was obtained using cyclic voltammetry, chronoamperometry, differential-pulsed voltammetry. The limit of detection for DCF reached by direct analysis on CuZEGE is from 2  10 À5 to 310 À7 M in relation with used technique and the potential value. Substantial enhancement of the electroanalytical parameters, e.g. the limit of detection of 510 À8 M. for the deter- mination of DCF at CuZEGE electrode was reached by applying a chemical preconcentration step prior to voltam- metric quantification. Keywords: Cu-doped zeolite-expanded graphite-epoxy electrode, Diclofenac sodium, Electrochemical determination DOI: 10.1002/elan.201000074 Presented at the International Conference on Modern Electroanalytical Methods Prague, December 9–14, 2009 1. Introduction In recent years, the growing use of pharmaceuticals has initiated a considerable concern regarding their presence in the environment [1–3]. Sodium diclofenac(DCF), so- dium[o-(2,6-dichloroanilino) phenyl] acetate, is a widely used anti-inflammatory drug, which exhibits anti-inflam- matory, analgesic and antipyretic activities, and can be re- garded as a representer of a novel class of water pharma- ceuticals contaminants, because it has been found in many wastewater treatment plants effluents [4]. Some- times, the wastewater treatment plants are not effective in diclofenac removal and mineralization and thus, rivers, lakes and ground water may be contaminated [1]. Besides the quantitative determination of diclofenac in dosage form, pharmaceuticals, and biological fluids, and because of its potential impact on human health the quantitative determination and control of diclofenac in water are a prime necessity. Several methods for the quantitative determination of diclofenac have been reported. They include spectropho- tometric [5–8], fluorometry [9], and chromatography [10– 12]. However, most of these techniques are time-consum- ing, laborious to perform or require chemical reagents, thus electrochemical methods have attracted interest, be- cause of the fast response, large sensitivities, simple oper- ation, and the possibilities of miniaturization [12–24]. Among the electrochemical methods, various voltammet- ric/amperometric [14–19] and potentiometric techniques [20–24] have been reported for the determination of di- clofenac. Because the rate of the electrooxidation of diclofenac on common solid carbon electrode is slow, and also offers a number of chemical, physical and structural properties to be used as a support for an electrocatalyst [14], the chemically modified carbon based electrodes involving a catalyst can be used to improve the electroanalytical per- formance. Zeolite is a common material that is usually employed as an inert feature of high interest in the design of the electrochemical sensors, because of its properties, i.e., shape, size and charge selectivities, physical and chemical stabilities, high ion-exchange and sorption ca- 2058  2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim Electroanalysis 2010, 22, No. 17-18, 2058 – 2063 Full Paper