SIMULTANEOUS DETERMINATION OF ENALAPRIL MALEATE AND HYDROCHLOROTHIAZIDE IN TABLETS BY DERIVATIVE UV SPECTROPHOTOMETRY AND HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY

A method for the simultaneous determination of enalapril maleate and hydrochlorothiazide in pharmaceutical formulations (tablets) is described. The procedure is based on the use of the high-performance liquid chromatography (HPLC), and of the second-derivative ultraviolet spectra, by utilizing the linear relationship between substances concentration and derivative peak amplitude. The minimum concentration detectable by derivative spectrophotometry was 1 mug ml-1 for both drugs, and by HPLC 50 ng ml-1 for hydrochlorothiazide and 100 ng ml-1 for enalapril maleate. The relative standard deviations observed were approx. 2% for derivative spectrophotometry, and 1.5% for HPLC. The proposed methods, which give thoroughly comparable data, are simple and rapid, and allow precise and accurate results.