Separation and quantitation of azimilide and its putative metabolites by capillary electrophoresis

Reliable methods based on capillary electrophoresis (CE) have been developed for the separation and quantitation of azimilide, an antiarrhythmic drug under development at Procter & Gamble Pharmaceuticals (P&GP). Both capillary zone electrophoresis (CZE) and micellar electrokinetic capillary chromatography (MECC) were employed in the separation of azimilide from its impurities, degradants and/or metabolites. Separation of azimilide from NE-11178, F-410, F-1054 and F-1292 was obtained by MECC at pH 9 with 50 mM sodium dodecyl sulfate (SDS). The separation of azimilide and NE-10171, a key metabolite of azimilide, was difficult because their structures differ by only a single methyl group. The best separation was achieved under acidic pH conditions with cetyltriethyl ammonium chloride (CTAC) additive in the buffer. All of the CE separations were completed within a substantially shorter time and with better resolution than the corresponding high-performance liquid chromatography (HPLC) separations. Quantitation was done with azimilide and NE-10171. Calibration curves ranging from 10 to 1000 μg/ml were obtained with R² greater than 0.997 for both azimilide and NE-10171. The back-calculated concentrations of the calibration standards and the recoveries of the quality control (QC) samples were within the acceptance range currently used for HPLC methods. These results demonstrated the viability of CE as an alternative technique for drug metabolism studies in support of pharmaceutical development.