Sulfonamides are among the most widely employed antibacterial agents in both human and veterinary medicine for prophylactic and therapeutic purposes due to their low cost andefficiency in the treatment of bacterial diseases. However, the widespread use of sulfonamides can lead to problems in terms of human health, taking into consideration that allergic and toxic reactions have been observed in patients treated frequently with sulfas. Therefore, methodswhich are accurate, simple and economical in terms of both time and cost for drug residue monitoring need to be developed (1). Chemically modified carbon paste electrodes (CCPEs) have been widely used because of their advantages such as renewability of their surface, stableresponse and low ohmic resistance (2). CeO2 (called Ceria) nano particles have attracted a lot of attention due to its high catalytic activity (CeO2 to Ce2O3) and biocompatibility (3). Recently, the decoration of RGO with different nanoparticles has received intense interest for producing a newtype of hybrid materials with properties that are variant from those of the individual components (4). In this study, a nano composite carbon paste electrode which contained 5%
Ceria NPs decorated RGO NPs was used as working electrode. The electrochemical behavior ofsulfadiazine at bare and ceria NPs decorated graphene nano composite carbon paste electrode was investigated by cyclic voltammetry and the results are shown in Fig.1 (A). The surface morphology of a bare and CeO2 NPs decorated on RGO NPs modified carbon paste electrode arerepresented in Fig.1 (B and C) respectively. As it can be seen in FE-SEM image (C), a large number of CeO2 nanoparticles have been attached to the RGO surface with a good dispersion, indicating a good combination between nanoparticles and RGO. The study was carried out by using Fast Fourier Transfer Square Wave Voltammetry (FFT SWV) was applied as detection technique. The proposed nanocomposite electrode showed two linear responses to sulfadiazine concentrations from 3 to 10 μM and 30 to 700μM (R2 = 0.9956 & 0.9948, respectively). In order to show the applicability of the proposed electrode, it was successfully used in determination of sulfadiazine in pharmaceutical products with acceptable 5% relative errors