Retention Behavior of Anti-Arrhythmic Drugs on the Chromolith Performance RP 18 Column. Liquid Chromatographic Determination of Mexiletine Hydrochloride

The retention behavior in liquid chromatography of a series of anti-arrhythmic drugs is described. Chromatographic analysis was performed on a Chromolith Performance ODS column with acetonitrile–phosphate buffer mixtures as mobile phases. The effects of the proportion of organic solvent (from 20 to 90%), phosphate buffer pH (from 2.73 to 7.5), flow rate (from 1 to 6 mL min^–1), and isocratic or gradient elution on the retention of the compounds was studied. Mexiletine hydrochloride was determined in the pure substance and in capsules by isocratic liquid chromatography with 20:80 (v/v) acetonitrile–0.007 M phosphate buffer, pH 3.0, as mobile phase at 2 mL min^–1. Methanol was found to be a suitable solvent for extraction of the active substance from capsules. The calibration plot was linear (r=0.9999) in the concentration range 1.0 to 6.0 g mL^–1. The proposed method is selective, precise (RSD=0.37%), and accurate (recovery=100.08%).Revised: 28 January and 2 March 2004