A Validated Stability-Indicating LC Method for Simultaneous Determination of Enalapril and Hydrochlorothiazide in Pharmaceutical Samples

A stability-indicating liquid chromatographic method was developed and validated for the simultaneous determination of enalapril maleate and hydrochlorothiazide in drug substances and dosage forms. The method was developed using a RP-18 column with mobile phase containing methanol - tetrahydrofuran - phosphate buffer (pH 2.2; 0.01M) (32:5:63, v/v/v) at a flow rate of 1.0 mL min-1 and UV detection at 210 nm. Enalapril and hydrochlorothiazide were subjected to hydrolytic, oxidative, thermal and photolytic stress conditions. The degradation products were well resolved from main peaks, proving the stability-indicating power of the method. The assay was linear for enalapril and hydrochlorothiazide concentrations of 40-140 μg/mL and 100-350 μg/mL respectively. The developed method was selective, accurate and precise for enalapril and hydrochlorothiazide determination. This method was successfully applied for determination of enalapril and hydrochlorothiazide in combined commercial tablets. The proposed method was found to be suitable for quantitative determination and the stability study of enalapril and hydrochlorothiazide in pharmaceutical preparations.