[Enantioseparation of tropicamide by capillary electrophoresis with square wave amperometric detection]

An enantioseparation method for tropicamide by high performance capillary electrophoresis with square wave amperometric detection (SWAD) was developed. The enantiomers of tropicamide were baseline separated in 16 min with an uncoated fused-silica capillary (75 microm i.d. x 50 cm) under the optimum conditions: 7 mmol/L Tris-10 mmol/L citric acid-2 mmol/L H3BO(3)-15 mmol/L beta-cyclodextrin (beta-CD) (pH 3.0) as background electrolyte, SWAD balance potential (E(b)) + 0.80 V (vs. Ag/AgCl), separation voltage 15 kV, injection height 20 cm, and injection time 10 s. The calibration curve of the enantiomers showed good linearity in the range from 5 micromol/L to 750 micromol/L with detection limit of 2 micromol/L. The average recoveries of added standards were 96% - 103%. The effects of the concentrations of beta-CD and the boric acid, the pH of the background electrolyte on resolutions (Rs) of the enantiomers were discussed in details. The proposed method was applied to the determination of a commercial tropicamide eye-drops sample without pre-treatment, and satisfactory results were obtained.