Saeed Arayne M, Safila Naveed and Najma Sultana
A sensitive, reproducible isocratic reversed phase method has been developed and validated for the simultaneous quantification of enalapril and diuretics (hydrochlorothiazide and furosemide) in active pharmaceutical ingredients, dosage formulations and human serum using high-performance liquid chromatography (RP-HPLC). The method was validated according to ICH guidelines for the parameters: specificity, stability, limits of detection (LLOD), limits of quantification (LLOQ), linearity, accuracy, precision and recovery. Chromatographic separation was performed on Hypersil ODS C18 (150×4.6mm, 5micron) and Purospher Start C18 (250 mm×4.6 mm, 5 μm) columns using gradient elution, when methanol: water (75:25 v/v) was used as the mobile phase and pH adjusted to 3 with orthophosphoric acid having flow rate of 1.0 mL min-1 at ambient temperature. The lower limit of quantitation (LLOQ) and detection (LLOD) were 5,4.6,12.6 and 1.6,1.53,4.1 ngL-1 for HCT, ENP and FRS respectively. Calibration curves were linear in the concentration range of 2.5-100 μg mL-1 with a correlation coefficient ± 0.999 for all three drugs. Intra-day and inter-day precisions were less than 2 %. The accuracies were in the range of precision 98.0–102%. The retention time of HCT, ENP and FRS were found to be 3,3.5 and 4 mins respectively which shows the rapidness. This is the first full report of a method for the simultaneous determination of these three key drugs. The newly developed method is useful for future routine analysis of these drugs enalapril and diuretics in active pharmaceutical ingredients, pharmaceutical preparations, serum and could be used in therapeutic drug monitoring, clinical, laboratories and adherence to medicine studies, which would be helpful in decision making regarding treatment change in combination therapies.