Non-aqueous capillary electrophoresis for separation and simultaneous determination of fraxin, esculin and esculetin in Cortex fraxini and its medicinal preparations.

A non-aqueous capillary electrophoresis method has been developed for the separation and simultaneous determination of fraxin, esculin and esculetin in Cortex fraxini and its preparation for the first time. Optimum separation of the analytes was obtained on a 47 cm x 75 microm i.d. fused-silica capillary using a non-aqueous buffer system of 60 mM sodium cholate, 20 mM ammonium acetate, 20% acetonitrile and 3% acetic acid at 20 kV and 292 K, respectively. The relative standard deviations (RSDs) of the migration times and the peak heights of the three analytes were in the range of 0.23-0.28 and 2.12-2.60%, respectively. Detection limits of fraxin, esculin and esculetin were 0.1557, 0.4073 and 0.5382 microg/mL, respectively. In the tested concentration range, good linear relationships (correlation coefficients 0.9995 for fraxin, 0.9999 for esculin and 0.9992 for esculetin) between peak heights and concentrations of the analytes were observed. This method has been successfully applied to simultaneous determination of the three bioactive components with the recoveries from 90.2 to 109.2% in the five samples.