Application of dimethyl‐ β ‐cyclodextrin as a chiral selector in capillary electrophoresis for enantiomer separation of ephedrine and related compounds in some drugs

Dimethyl‐ β ‐cyclodextrin (DM‐ β ‐CD) modified capillary electrophoresis has been developed for chiral separation of ephedrine and related compounds, such as (±)‐norephedrine, (±)‐ N ‐methylephedrine, (±)‐ephedrine and (+)‐pseudoephedrine. The influence of some crucial parameters such as buffer concentration, pH value, DM‐ β ‐CD concentration, applied voltage and separation temperature on the separation was investigated. Under the optimum conditions, i.e. 40 mm DM‐ β ‐CD in 75 m m Tris (pH 2.5) as the running electrolyte, separation voltage +25 kV and temperature 25°C, a satisfactory separation of the enantiomers was accomplished. The detection limits (S/N = 3) ranged from 65 to 161 ng/mL and the linear range was 0.15 to 101.0 µg/mL for pressure injection. The present method was successfully applied for the analysis of a series of drugs such as anti‐tussive, the drug for rheum, the drug for rhinitis and a Chinese traditional herbal medicine, Ephedrae herba (Ma‐Huang in Chinese). The recoveries of ephedrine and related compounds in real samples ranged from 97.6 to 103.5%. This method is useful in the simple and rapid analysis of ephedrine derivatives in marketed products. Copyright © 2005 John Wiley & Sons, Ltd.