DIRECT SEPARATION AND DETERMINATION OF SYNEPHRINE ENANTIOMERS BY HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY WITH ELECTROCHEMICAL DETECTION

High-performance Liquid chromatography (HPLC) with electrochemical det ection using a chiral ligand-exchange column (Sumichiral OA-5000) and a mobile aqueous phase containing 1 mM copper(II) acetate and 20 mM am monium acetate (pH 6.4) was applied to the direct separation and deter mination of synephrine enantiomers, The calibration curve for each ena ntiomer showed good linearity (r=0.999) over a concentration range of 0.2-100 mu M with a detection limit of 0.2 mu M (signal-to-noise ratio (SIN)=3). As far as reproducibility was concerned, the relative stand ard deviation (R.S.D.) was 2.6% at 20 mu M d-synephrine and 2.4% at 20 mu M I-synephrine. The degradation and optical isomerization of I-syn ephrine in Citrus unshiu were caused by ultraviolet (UV) light or heat , The synephrine enantiomers in citrus plants, crude drugs and Chinese medicines were determined by the present method.