Determination of trace levels of niguldipine in urine and blood by adsorptive stripping voltammetry at the hanging mercury drop electrode.

A relatively simple electroanalytical procedure for the determination of niguldipine in biological samples is described. The technique involves adsorptive accumulation of the drug at the hanging mercury drop electrode (HMDE) followed by a differential-pulse polarographic determination of the preconcentrated species. The adsorptive stripping response is evaluated with respect to various experimental conditions, such as solvent composition and pH of the supporting electrolyte, accumulation potential and accumulation time. After a simple sample preparation, the method can be used for the determination of niguldipine in blood and urine. Interfering substances are simply removed by precipitation, adding a small amount of 5% ZnSO4 solution and ethanol to the urine or blood sample and centrifuging the mixture. A limit of detection of 6.7 ng per ml of urine and 41 ng per ml of blood is found with a mean recovery of 96% in urine and 71% in blood. The mean relative errors are 8.4% and 2.2%, respectively.