HPCE Determination of Ephedrine Hydrochloride and Pseudo-Ephedrine Hydrochloride in Drugs with Enrichment by Electro-stacking

HPCE with electro-stacking enrichment was applied to the determination of ephedrine hydrochloride and pseudo-ephedrine hydrochloride in 6 drugs.Analytical conditions were studied and following optimized parameters were given: ① wavelength for UV-detection: 205 nm;② internal standard: resorcinol;③ electrophoretic medium: 40 mmol·L-1 borax solution(pH 9.2);④ separation voltage: 20 kV;⑤ time of sample introduction: 10 s;⑥ temperature of capillary: 25 ℃.Linear relationships between values of relative peak area(i.e.,ratio of peak area of the analyte to peak area of internal standard) and concentration of ephedrine and pseudo-ephedrine were kept in the same range of 1 to 400 mg·L-1,with detection limits(3S/N) of 0.35 mg·L-1 and 0.29 mg·L-1 respectively.Recovery was tested by standard addition method using 2 drug samples as matrixes,giving values of average recovery of 101.1%(for ephedrine) and 103.6%(for pseudo-ephedrine).