Quantification of Benazepril Hydrochloride and Hydrochlorothiazide in Tablet Dosage Form by Simultaneous Equation Spectrophotometric Method

Simple, accurate, precise, reproducible, requiring no prior separation, and economical procedures for simultaneous estimation of benazepril hydrochloride (BEN) and Hydrochlorothiazide (HCT) in tablet dosage form have been developed. Simultaneous equation method employs for estimation of both drugs in methanol at 240？nm and 270？nm as two analytical wavelengths. BEN and HCT at their respective (240？nm and 270？nm) show linearity in a concentration range of 2–12？μg/mL and 4–14？μg/mL. Recovery studies for BEN are 100.0–100.6% and 99.8–100.0% for HCT in the case of simultaneous equation method confirming the accuracy of the proposed method. The proposed method is recommended for routine analysis since it is rapid, simple, accurate and also sensitive and specific. 1. Introduction Benazepril hydrochloride (BEN) is chemically 3-[[1-(ethoxycarbonyl)-3-phenyl-(1S)-propyl]amino]-2,3,4,5-tetrahydro-2-oxo-1H-1-(3S)-benzazepine-1-acetic acid monohydrochloride (Figure 1(a)). The empirical formula of BEN is C24H28N2O5·HCl with a molecular weight of 460.96？g/mole [1]. It is an angiotensin converting enzyme. It is used as antihypertensive agent. Figure 1: (a) Structure of hydrochlorothiazide. (b) Structure of benazepril hydrochloride. Hydrochlorothiazide (HCT) is chemically 6-chloro-3,4-dihydro-2H-1,2,4-benzothiadiazine-7-sulfonamide 1,1-dioxide (Figure 1(b)). The empirical formula is C7H8ClN3O4S2 with a molecular weight 297.73？g/mole [2]. It is a diuretic agent. BEN and HCT are official in the british Pharmacopeia and the Indian Pharmacopeia. Many methods have been reported in the literature for both determination of BEN, individually and with other drugs in combination [3–17]. However, there is no UV spectrophotometric method reported for the simultaneous estimation of BEN and HCT in pharmaceutical preparations in the literature survey. The objective of the present work is to develop and validate new analytical methods for simultaneous determination of BEN and HCT in tablet dosage form. 2. Experimental 2.1. Materials and Methods A double-beam Shimadzu UV-visible spectrophotometer 1700 (Pharma spec), with wavelength accuracy of ±0.5？nm and a pair of 1？cm matched quartz cells, was used to measure absorbance of the resulting solution. All weighing was done on an electronic balance (Shimadzu BL-220H). All statistical calculations were carried out using Microsoft Excel 2007 analytical tool. Analytically pure BEN and HCT were procured as gift sample from Dishman Pharmaceuticals Ltd. and Cadila Pharmaceutical Pvt. Ltd. (Ahmedabad, India). Methanol (E. Merck, Mumbai, India)