Simultaneous determination of moexipril hydrochloride and hydrochlorothiazide in tablets by derivative spectrophotometric and high-performance liquid chromatographic methods

Abstract

Two new simple and selective assay methods have been presented for the binary mixtures of moexipril hydrochloride (MOEX) and hydrochlorothiazide (HCTZ) in pharmaceutical formulations. The first method depends on second-derivative ultraviolet spectrophotometry with zero-crossing measurements at 215 and 234 nm for MOEX and HCTZ, respectively. The assay was linear over the concentration ranges 1.0–11.0 μg ml −1 for MOEX and 0.5–9.0 μg ml −1 for HCTZ. The determination limits for MOEX and HCTZ were found to be 1.0 and 0.5 μg ml −1, respectively; while the detection limits were 0.2 μg ml −1 for MOEX and 0.1 μg ml −1 for HCTZ. The second method was based on isocratic reversed-phase liquid chromatography by using a mobile phase acetonitrile–20 mM phosphate buffer (pH 4.0) (50:50, v/v). Lisinopril was used as an internal standard (IS) and the substances were detected at 212 nm. The linearity range for both drugs was 0.5–12.0 μg ml −1. The determination and detection limits were found to be 0.100 and 0.010 μg ml −1 for MOEX and 0.025 and 0.005 μg ml −1 for HCTZ, respectively. The proposed methods were successfully applied to the determination of these drugs in synthetic mixtures and commercially available tablets with a high percentage recovery, good accuracy and precision.