Micellar electrokinetic capillary chromatography for the separation of cefalexin and its related substances

Micellar electrokinetic capillary chromatography (MEKC) was examined for an alysis of cefalexin and its related substances. Good selectivity was obtain ed with two different buffer solutions: a sodium acetate buffer (50 mM, pH 5.25) containing sodium dodecyl sulfate (50 mu SDS) or sodium phosphate buf fer (40 mM, pH 7.0) containing 100 mM SDS. Both methods permit cefalexin to be completely separated from its ten related substances within 20 min. The robustness of the method, using pH 5.25 acetate buffer, was examined by me ans of a full-fraction factorial design to test the influence of buffer pH, concentration of SDS and buffer concentration. The parameters for validati on such as linearity, precision, limit of detection and limit of quantitati on are also reported. The results show that method 1 is suitable for the an alysis of cefalexin.