Redox properties of isradipine and its electrochemical detection in the HPLC determination of the compound in human serum

The electrochemical behaviour of isradipine in a mixed solution of Britton- Robinson buffer (pH 11.8):acetonitrile:methanol (6:3:1, v/v) was studied by cyclic voltammetry and spectroelectrochemistry using an optically transpar ent thin layer electrode of carbon cloth. The cyclic voltammogram showed se veral peaks whose shape and potentials depended on the pH. The peak at 330 nm, corresponding to the absorbance of the dihydropyridine ring, disappeare d after electrolysis at a potential that was more positive than the oxidati on peak. The oxidation peak corresponds to the oxidation of the dihydropyri dine ring. Peak height at pH 11.8 was proportional to isradipine concentrat ion. On the basis of the redox properties of isradipine, HPLC was conducted applying electrochemical detection on a polybutadiene coated alumina colum n using an alkaline mobile phase. The method was applied for the determinat ion of isradipine content in human serum. A good linear relationship betwee n isradipine concentration and peak height was found in the concentration r ange of 2-200 ng/mL with a correlation coefficient of 0.9924. The detection limit was 0.5 ng/mL. The within-day and day-to-day variation were examined for control human serum and percentage relative standard deviation ranged from 0.5 to 6.7. Interference from many other coadministered drugs was stud ied in the specified experimental conditions. Photo and heat stabilities of the compound were also studied. Copyright (C) 2000 John Wiley & Sons, Ltd.