RESUMO
A simple high-performance liquid chromatographic method was developed for determination of diltiazem in human plasma. Diltiazem and the internal standard, verapamil, were extracted from plasma samples using mixture of n-hexane and diethyl ether. The mobile phase was 0.1M ammonium dihydrogen phosphate - acetonitrile [62:38 v/v]. Triethylamine [0.08% v/v in the mobile phase] was added before the pH was adjusted to 5.9 with 85% phosphoric acid. Analysis was run at a flow rate of 1.0 ml/min at a detection wavelength of 238 nm. The method was specific and sensitive with a detection limit of 2.5 ng/ml at a signal-to-noise ratio of 3:1. The limit of quantification was set at 5 ng/ml. The calibration curve was linear over a concentration range of 5-160 ng/ml. Mean recovery value of the extraction procedure was about 90%, while the within and between day coefficient of variation and percent error values of the assay method were less than 10%