Simplified reversed-phase HPLC method with spectrophotometric detection for the assay of verapamil in rat plasma

Abstract

A high-performance liquid chromatographic (HPLC) method was developed for the assay of verapamil in rat plasma. After deproteinization of the plasma sample with an acetonitrile-perchloric acid (8:2) mixture containing dextromethorphan, the internal standard, an aliquot of the supernatant was directly analyzed on a cyanopropylsilane column with methanol-acetonitrile-triethylamine acetate buffer (10:30:60) as the mobile phase and detection at 235 mm. At a flow rate of 1.5 ml min −1, a complete analysis was completed in less than 6 min. The method was linear for verapamil concentrations in the range 0.5–10 μg ml −1 ( r=0.9999). Recoveries for the same drug concentrations from spiked rat plasma ranged from 85.6-93.0% ( n=8). The mean RSD values for intraday and interday assay reproducibility ( n=3) were, in both cases, less than 0.9%. The limit of detectability was about 0.1 μg ml −1. The method was found useful to monitor the plasma levels of verapamil in rats that had received this drug by the nasal, oral and intravenous routes of administration.