DIFFERENTIAL-PULSE POLAROGRAPHY OF CADMIUM-URATE AND LEAD-URATE AND ADSORPTIVE STRIPPING VOLTAMMETRIC DETERMINATION OF URIC-ACID

The complex formation between uric acid and zinc, cadmium and lead ions has been investigated using differential pulse polarography in 0.01 M NaNO3. It is found that the complexes formed by Cd(II) and Pb(II) ions with uric acid have the stoichiometry of 1:2 and the logarithmic values of the apparent stability constant are 9.47 and 11.7, respectively. On the other hand, zinc(II) ions do not give any indication of complexation with uric acid. A sensitive voltammetric method is developed for the quantitative determination of uric acid. This method is based on controlled adsorptive preconcentration of uric acid on the hanging mercury drop electrode (HMDE), followed by tracing the voltammogram in the cathodic going potential scan. The modes used are direct current stripping voltammetry (DCSV) and differential pulse stripping voltammetry (DPSV). The detection limits found were 8 x 10(-9) M (quiescent period 15 sec) by DPSV and 1.6 x 10(-8) M by DCSV.