Determination of Ephedrine, Pseudo-Ephedrine and Caffeine in a Dietary Product by Capillary Electrophoresis

This paper reports the determination of caffeine, ephedrine and pseudo-ephedrine in a dietary product by two rapid and simple methods utilising capillary electrophoresis (CE). The solutes were extracted from the product using 0.2 M HCl and determined by CE with background electrolytes containing 7.5% highly sulfated-β-cyclodextrin (7–11 sulfate groups per β-CD molecule) at pH 2.5 and pH 7.6. Determination of ephedrine and pseudo-ephedrine was accomplished at pH 2.5 with the anode at the detection side of the capillary whereas caffeine was quantified at pH 7.6 with a normal electrophoresis polarity mode. Triethanolamine was added to the running buffer at pH 2.5 in order to reverse the electroosmotic flow (EOF) and thereby speed up the separation of ephedrine and pseudo-ephedrine. Revised: 18 November 2005 and 2 January 2006