H-point Standard Addition Method for the Simultaneous Spectrophotometric Determination of Captopril and Hydrochlorothiazide in Pharmaceutical Formulations

Simultaneous spectrophotometric determination of captopril and hydro-chlorothiazide in pharmaceutical formulations by the H-point standard addition method (HPSAM) is described. Absorbance at 211.5 and 230.3 nm was monitored upon the addition of standard solutions of captopril. The results showed that in prepared mixtures, captopril and hydrochlorothiazide can be determined simultaneously at concentration ratios varying from 1.0:0.8 to 2.5:1.5 μg/mL, respectively. Percentage recovery was found to be 95.33–104.37% for captopril and 96.8–105% for hydrochlorothiazide, with a relative standard deviation (RSD) of 2.46%. The method was successfully used to evaluate the antihypertensive captopril drug in a binary combination of hydrochlorothiazide in real samples with high precision and accuracy within the recovery percentage.