Micellar electrokinetic capillary chromatography as an alternative method for the determination of dexamethasone, trimethoprim, and polymyxin B

A micellar electrokinetic capillary chromatographic method is presented which enables quantification of dexamethasone, polymyxin B and trimethoprim in synthetic mixtures and pharmaceutical products. Separation was carried out at 25?°C and 30 kV, with 10 mmol L^–1 borate–phosphate buffer adjusted to pH 8 as electrolyte, with 50 mmol L^–1 sodium dodecyl sulfate. Under these conditions separations were performed in 10 min. The limits of detection and quantification were approximately 2 mg L^–1 for each component, except for polymyxin B. The method was applied to different commercial formulations.