Simultaneous electrochemical determination of xanthine and uric acid at a nanoparticle film electrode

A sensitive electrochemical method was developed for simultaneous determination of uric acid (UA) and xanthine (XA) at a glassy carbon electrode modified with multi-wall carbon nanotubcs (MWNTs) film. The oxidation peak currents of UA and XA were increased at the MWNTs film electrode significantly. The experimental parameters, which influence the peak currents of UA and XA, such as the amount of MWNTs on the glassy carbon electrode, the pH of the solution, accumulation time, and scan rate, were optimized. Under optimum conditions, the peak currents were linear to the concentration of UA over the wide range from 1x10(-7) mol L-1 to 1x10(-4) mol L-1 and to that of XA over the wide range from 2x10(-8) mol L-1 to 2x10(-5) mol L-1. The interferences studies showed that the MWNTs-modified electrode exhibited excellent selectivity in the presence of ascorbic acid, dopamine, and hypoxanthine. The proposed procedure was successfully applied to detect UA and XA in human serum without any preliminary treatment.