[Separation of ofloxacin enantiomers by high performance capillary electrophoresis(HPCE)]

An analytical method for separation of ofloxacin enantiomers by HPCE using bovine serum albumin(BSA) as the chiral selector and isopropanol as the modifier was established. The effects of BSA concentration, pH of running buffer, isopropanol concentration, applied voltage and column temperature on the resolution of the enantiomers have been studied. The experimental results indicated that the BSA concentration and pH of the running buffer were the vital factors for the separation of the enantiomers. The concentration of isopropanol showed strong influence on the peak shape of enantiomers. Lower voltage and column temperature were favorable to improve the efficiency for the separation of the enantiomers. Optimum performance was achieved in a fused-silica capillary(45 cm x 30 microns ID, effective length 32 cm) at 30 degrees C and applied voltage of +15 kV with a pH 6.0 phosphate buffer containing 50 mg.ml-1 BSA and 5% isopropanol as running buffer and detected at 293 nm. The precision of this method was evaluated by repeated measurement of the migration times and peak areas for 0.45 mg.ml-1 ofloxacin standard solution. The RSD(n = 8) for migration times and peak areas were 1.6% and 1.1% for (-)-ofloxacin and were 1.8% and 2.8% for (+)-ofloxacin, respectively. The method was simple and fast and has been applied to separate enantiomers of ofloxacin products. The experimental results showed that the ratio of peak area of (-)-ofloxacin to that of (+)-ofloxacin was within the range of 0.995-0.998 with RSD(n = 6) of measurement between 1.8% and 2.0%.