Concurrent Determination of Diltiazem, Lisinopril, Captopril, and Enalapril in Dosage Formulations and in Human Serum by Liquid Chromatographic Technique

Abstract

The aim of this study was to develop an analytical method that can quantify diltiazem, lisinopril, captropil, and enalapril in pharmaceuticals dosage forms and biological fluids, as these drugs are co-administered drugs. For the determination of diltiazem and ACE inhibitors a novel, trouble-free, quick, isocratic high performance liquid chromatography method has been established. The ACE inhibitors, which were assayed alongside diltiazem, include lisinopril, captopril, and enalapril. These drugs were tested in bulk, dosage formulations, and human serum. The analytes were separated on Pruospher Star RP-18 endcapped (250 mm × 4.6 mm id), and the mobile phase composition was acetonitrile:methanol:water (5:45:50 v/v/v). The pH of the mobile phase was adjusted with ortho-phosphoric acid at 2.5. The flow rate was maintained at 1 mLmin−1 at room temperature (25°C). The maximum wavelength for the assay was 230 nm on a UV detector. ICH validation parameters were followed while validating the method. The selected concentration range for establishing the linearity for diltiazem was 2.5–25 µgmL−1, 20–200 µgmL−1 for lisinopril enalapril, and 30–300 µgmL−1 for captopril. This linearity range was best as was demonstrated by r2 ≥ 0.999 (n = 6).