Simultaneous determination of enalapril and hydrochlorothiazide in pharmaceutical preparations using microemulsion liquid chromatography.

A rapid high-performance liquid chromatography procedure for analytical quality control of mixture containing enalapril maleate (ENM) and hydrochlorothiazide (HCT) in their pharmaceutical preparations was developed using a microemulsion as an eluent. The separation was performed on a column packed with cyano-bonded stationary phase adopting UV detection at 210 nm using a flow rate of 1 mL/min. The optimized microemulsion mobile phase consisted of 0.2 M sodium dodecyl sulfate, 1% octanol, 10% n-propanol and 0.3% triethylamine in 0.02 M phosphoric acid, and pH was adjusted at 3.5. The proposed method was found to be linear over the concentration ranges 1-100 and 0.05-5 μg/mL for ENM and HCT, respectively with a correlation coefficient of 0.9999 for both drugs. The developed method was validated in terms of specificity, linearity, lower limit of quantification, lower limit of detection, precision and accuracy. The proposed method is rapid (5 min), reproducible (relative standard deviation <2.0%) and achieves a satisfactory resolution between ENM and HCT (resolution factor = 3.62). The mean recoveries of the analytes in tablets were in agreement with those obtained from a comparison method, as revealed by statistical analysis of the obtained results using Student's t-test and the variance ratio F-test.