صدیقه هاشم نیا

Dopamine (DA) and uric acid (UA) are important human body compounds that play determining role in metabolism [1], hence, monitoring their concentration in biologic fluids such as blood and urine may prevent and control many diseases. These are electrochemically active compounds that can be determined by different techniques. In recent years, the development of voltammetric methods for their determination in human body fluids such as urine and serum has received considerable interest. However. at bare electrodes DA and UA are oxidized at nearly the same potential, which result in overlapped voltammetric responses making their simultaneous discrimination highly difficult. Thus, it is essential to develop reliable methods with good sensitivity and selectivity for simultaneous determination of DA and UA in routine analysis. Among the methods, chemically modified electrodes (CMEs) with metal nanoparticles are becoming popular ways because of the characteristics such as easier fabrication process, more excellent electrochemical catalytic ability and physical stability l2l. l,{anoparticle modified electrodes can also show an apparent increase in signal to noise ratio in electrochemical systems. Silver is a good substrate electrode for the preparation of modified electrodes. In the present work, after the synthesis of the nanosized silver colloids by a chemical reduction process in aqueous solution inthe presence of polyvinylpyrrolidone (PVP) as a stabilizingagent [3], a silver nanoparticle modified carbon paste electrode was prepared. The modified electrode was studied for the DA voltammetric responses in the presence of uric acid. The oxidative potentials of DA and UA could be separated by the modified electrode, thereby enabling the independent determination of DA in the presence of UA (Fig. 1). The modified electrode showsan excellent electrocatalyic activity towards the oxidation of DA in 0.1 M phosphate buffer solution (pH 8.0) and the linear dynamic range of DA exten