pH-Zone-refming counter-current chromatography was applied to the separation of alkaloids from a crude extract of the root of Sophora flavescens Ait using a multilayer coil planet centrifuge. After methyl tert.-butyl ether and water were equilibrated, triethylamine (10 mM) was added to the organic phase as a retainer and hydrochloric acid (5-10 mM) to the aqueous phase as an eluter. The separation was performed by eluting the aqueous phase while the organic phase was used as the stationary phase. From. 1.0 g of the crude extract, sophocarpine (170 mg) and matrine (600 mg) were separated within 4.5 h at high purity of over 98%. (C) 1998 Published by Elsevier Science B.V. All rights reserved.