Abstract

Background and the purpose of the study: The use of highly sulfated cyclodextrins (HS-CDs) as chiral selectors in capillary electrophoresis (CE) has been examined for rapid and reproducible enantioseparation of the model drug amlodipine, a calcium channel blocker. Materials and Methods: Fused silica capillaries with an inner diameter of 50 mu m, and a total length of 45.5 cm (8.5 cm to the detector) were used. Capillaries were rinsed with polyethylene oxide (PEO) once daily. A systematic method development approach was conducted by modifying selected parameters such as the type and concentration of the chiral selector, the buffer pH and concentration of the background electrolyte. Results: Baseline separation was achieved at low (i.e. 0.05w/v) concentrations of HS-alpha CD, but migration time and peak area repeatability were more than 4 and 25 of the relative standard deviation (RSD), respectively. At higher concentrations (>0.3) of HS-alpha CD, amlodipine was transported to the anode by the carrier ability of HS-aCD. In carrier mode, the migration order of enantiomers was reversed, the migration time was reduced and the peak area repeatability of analysis was improved. The optimum electrophoretic conditions for the stereoselective analysis of amlodipine were obtained in carrier mode with 25 mM sodium phosphate buffer containing 1.25 w/v of HS-alpha CD at pH 2.5 with an applied voltage of +15 kV. Under these conditions migration time was less than 3 min and within-day migration time and peak area repeatability, were less than 0.4 and 2.1 RSD, respectively. Conclusions: Rapid enantioseparation was achieved with minimum variation in quantitative analysis. These optimized conditions are appropriate for the enantioselective analysis of amlodipine.