Validation of a capillary electrophoresis method for the determination of a quinolone antibiotic and its related impurities

Abstract

Free solution capillary electrophoresis (FSCE) has been employed for the novel determination of a quinolone antibiotic which has limited solubility between pH values of 2 and 11. This limited pH range gave problems with HPLC methods that were attempted for quantitative analysis. The fused-silica capillaries utilised in CE are able to withstand pH extremes, therefore CE was used in preference to HPLC for determining both drug content and levels of related impurities present in drug substance. A CE method operating at pH 1.5 was shown to be suitable for this analysis. The sample was prepared at 0.5 mg/ml in 0.1 M NaOH and injected utilising pH mediated sample stacking. This represents the first report describing the analytical performance of this stacking procedure. Although several reports have shown CE to be suitable for pharmaceutical analysis this report is the first to provide validation details for an impurity determination method. Acceptable levels of precision, linearity, limits of detection and quantitation were achieved. Capillary electrophoresis of basic drug compounds at low pH offers a useful alternative and complement to HPLC.