Uric acid is the final oxidation product of purine metabo-

lism. Severe changes in the concentration of uric acid causes several diseases such as gout, hyperuricemia and Lesch–Nyhan syndrome. Therefore, the accurate determination of uric acid in urine samples can be a powerful indicator of diagnosing diseases. Thus, many researchers have focused to develop a simple, sensitive and accurate method for determining uric acid. Various methods have been developed for the determination of uric acid including, e.g., enzyme biochip system, fluoroscence, liquid chromatography, scanning electrochemical microscopy. Self-assembled monolayers have also been developed for the determination of uric acid in urine samples. Recently, it has been shown that electrochemical determination of uric acid at polymer modified electrodes showed good selectivity and sensitivity. Moreover, ascorbic acid which is a powerful water soluble antioxidant, has a key role in protecting against the oxidative injury and has been used for the treatment of several diseases. Therefore, the detection of ascorbic acid has a biological importance. Several techniques have been used for the determination of ascorbic acid such as capillary zone electrophoresis, spectrofluorometry, flow injection, voltammetry, and chemiluminescence. However, electrochemical methods have attracted more attention because of sensitivity, selectivity and simplicity. At bare electrodes, the oxidation of ascorbic acid occurs at a potential close to that of uric acid and the bare electrode very often suffers from fouling effects. Therefore it is necessary to develop an electrochemical sensor to separate the oxidation peak potentials of uric acid and ascorbic acid and for the determination of uric acid in the presence of ascorbic acid. Up to now, no articles have been reported concerning the determination of uric acid on a poly(3-acetylthiophene) or derivatives of poly(thiophenes) modified glassy carbon electrodes (GCEs). However, there are limited reports about the electropolymerization of other thiophenes used for determination of some neurotransmitters. The electropolymerization of thiophenes on a GCE enables better electrode surfaces for the electrocatalytic oxidation of biochemical species because poly(thiophenes) have potentially more useful electronic properties and provide highly conducting surfaces. In this paper, a poly(3-acetylthiophene) modified glassy carbon electrode was prepared to study the electrocatalytic oxidation of uric acid. The method is based on modification of a GCE by electropolymerization of 3-acetylthiophene in acetonitrile containing 0.05 M LiClO4 as the supporting electrolyte using cyclic voltammetry. Then the coated electrode was utilized for determination of uric acid using voltammetric methods. It has been shown that the oxidation potential of uric acid can be well separated from than that of ascorbic acid at the modified electrode. The results showed that the modified electrode could be used to detect uric acid in the presence of ascorbic acid. The modified electrode has successfully been applied for the determination of uric acid in urine samples.