Rapid and simple determination of sennoside A and B in rhei rhizoma by ion-pair high-performance liquid chromatography.

A simple and precise ion-pair high-performance liquid chromatographic method was developed for the determination of sennoside A and B in Rhei Rhizoma. A reversed-phase chromatographic system consisting of a chemically bonded ODS silica gel column with an acetate buffer (pH 5.0)-acetonitrile (68:32), containing 5 mM tetra-n-heptylammonium bromide, as the mobile phase was used. Sennoside A and B in this crude drug were separated and determined within 20 min after direct injection of the solution extracted with 70% methanol. The results for various samples are presented.