A DIFFERENTIAL-PULSE VOLTAMMETRIC DETERMINATION OF NISOLDIPINE USING GLASSY-CARBON ELECTRODE IN PHARMACEUTICAL PREPARATIONS

A differential pulse voltammetric method is described for the determin ation of nisoldipine based on the oxidation of the dihydropyridine gro up on the surface of a rotating glassy carbon disk electrode. The volt ammetric behavior of this compound was investigated in the supporting electrolyte consisting of 0.2 M KCl, 0.1 M phosphate buffer and 30 per cent ethanol during the investigation of the pH effect. The maximum si gnal to noise ratio and the most symmetrical peaks were obtained in th e use of the supporting electrolyte solution containing 0.1 M H2SO4 in 30 percent ethanol and initial potential of +300 mV. The factor affec ting the voltammetric current was diffusional in the range of 200-2000 rpm and up to 1x10(-4) M nisoldipine concentration. The detection lim it and reproducibility were calculated to be 8x10(-6) M for the concen tration of 7.8x10(-5) M NSD, accepting the ratio of signal-to-noise (S /N) equal to 3 and 0.9 % for 5 successive experiments, respectively. T he DP voltammetric determination of nisoldipine in film coated tablets was conducted using optimum rotating conditions. According to the sta tistical evaluations acceptable results were obtained. Therefore, the method proposed in this study is practical, sensitive and accurate for the analysis of nisoldipine preparations in the quality control labor atories.