Comparison of high-performance liquid chromatography and absorbance ratio methods for the determination of hydrochlorothiazide and lisinopril in pharmaceutical formulations

The aim of this research was to study and to standardize a highperformance liquid chromatography (HPLC) and absorbance ratio method for the determinat ion of hydrochlorothiazide and lisinopril in commercially available pharmac eutical dosage forms. An HPLC method has been developed for the simultaneou s determination of hydrochlorothiazide and lisinopril from formulations, us ing acetonitrile:water (20:80 v/v) (pH 3.8), as a mobile phase at now rate of 1.0 mlmin(-1) and LiChrosorb RP-C-18 column (5 mu, 20cmx4.6 mm), asa sta tionary phase. Detection was carried out using a UV detector at 213.0 nn. I n the second method, an absorbance ratio method, the determination of hydro chlorothiazide and lisinopril was performed by using the absorbances read a t 272.0 nm, 258.8 nm and 262.7 nm in the zero-order spectra of their mixtur e. The absorbance ratio was also developed as a comparison method. The proposed methods, which give thoroughly comparable data, are simple and rapid, and allow precise and accurate results.