Simultaneous determination of benazepril hydrochloride and hydrochlorothiazide in tablets by second-order derivative spectrophotometry.

A second-order derivative spectrophotometric method for the simultaneous determination of benazepril hydrochloride and hydrochlorothiazide in pharmaceutical dosage forms is described. The determination of benazepril hydrochloride in the presence of hydrochlorothiazide was achieved by measuring the second-order derivative signals at 253.6 and 282.6 nm, while the second-order derivative signal at 282.6 nm was measured for the determination of hydrochlorothiazide. The linear dynamic ranges were 14.80-33.80 microg ml(-1) for benazepril hydrochloride and 18.50-42.20 microg ml(-1) for hydrochlorothiazide, the correlation coefficient for the calibration graphs were better than 0.9998, n = 5, the precision (%RSD) was better than 1.43% and the accuracy was satisfactory (Er < 0.99%). The detection limits were found to be 2.46 and 1.57 microg ml(-1) for benazepril hydrochloride and hydrochlorothiazide, respectively. The method was applied in the quality control of commercial tablets and proved to be suitable for rapid and reliable quality control.