Direct Separation and Determination of Synephrine Enantiomers by High-Performance Liquid Chromatography with Electrochemical Detection

Abstract

High-performance liquid chromatography (HPLC) with electrochemical detection using a chiral ligand-exchange column (Sumichiral OA-5000) and a mobile aqueous phase containing 1 mM copper(II) acetate and 20 mM ammonium acetate (pH 6.4) was applied to the direct separation and determination of synephrine enantiomers. The calibration curve for each enantiomer showed good linearity (r = 0.999) over a concentration range of 0.2—100 μM with a detection limit of 0.2μM (signal-to-noise ratio (S/N) = 3). As far as reproducibility was concerned, the relative standard deviation (R.S.D.) was 2.6% at 20 μM d-synephrine and 2.4% at 20 μM /-synephrine. The degradation and optical isomerization of /-synephrine 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. © 1995, The Pharmaceutical Society of Japan. All rights reserved.