Simultaneous Determination of Ephedrine and Pseudoephedrine in Mice Plasma by Capillary Zone Electrophoresis

A low cost, accurate, rapid and sensitive capillary zone electrophoresis (CZE) quantitative method, using thiamine hydrochloride as internal standard (IS), was developed for the simultaneous analysis of ephedrine and pseudoephedrine in mice plasma. Analytes were extracted from plasma samples by n-hexane/dichloromethane/isopropanol (2:1:0.1, v/v/v) after alkalization, and stripped with 1.5% hydrochloric acid solution. Separation was performed by CZE using 50mM borax-20mM threonine (pH 9.27) as running buffer, with voltage of +10 kV applied and UV detection wavelength at 210 nm. The total running time was within 10 min. Calibration curves for plasma samples were linear over the concentration range of 0.075-5.0 μg/mL for ephedrine and 0.0375-2.5 μg/mL for pseudoephedrine. The method had a limit of quantitation of 17.80 ng/mL for ephedrine and 22.00 ng/mL for pseudoephedrine,respectively. The method was reliable and feasible for the evaluation of pharmacokinetic profiles of drug products containing ephedrine and pseudoephedrine.