Determination of bisaramil and its metabolite in plasma using high-performance liquid chromatography with...

A column liquid chromatographic method using electrochemical detection has been developed for determination of an antiarrhythmic agent, bisaramil, and its metabolite in plasma. The plasma was fractionated by extraction with chloroform and chloroform-ethanol, and each fraction was dried and dissolved in ethyl acetate. After back-extraction into an acidic buffer, bisaramil was chromatographed on a reversed-phase column, and the metabolite, which has a higher polarity, was analysed by ion-pairing chromatography. Calibration curves were linear over the concentration range 2-200 ng/ml with coefficients of variation, within-day or day-to-day, not exceeding 5% at any level. The limits of detection of bisaramil and its metabolite were 0.5 and 1 ng/ml, respectively, using 0.5 ml of plasma. The dual-electrode detector was operated in the screening mode of oxidation (electrode 1, +0.55 V; electrode 2, +0.8 V), providing a greater specificity and reducing the background noise. This procedure was applied to a large number of samples in a pharmacokinetic study at the therapeutic dose.