Separation and determination of five anthraquinones in rheum and rheum-containing preparations by capillary zone electrophoresis

A capillary zone electrophoresis method modified by beta-CD was, for the first time, developed for the simultaneous determination of five anthraquinones (physcion, chrysophanol, aloeemodin, emodin and rhein) in rheum and rheum-containing preparations. The factors relevant to the run buffer media and their effects on the separation were studied. A buffer solution composed of 15 mM sodium borate, 30 mM beta-CD, 20% acetonitrile and 1.0% ethanediol was found to be the most suitable electrolyte for separation, whereby the contents of the five anthraquinones in rheum and rheum-containing preparations could be easily determined in 20 min at 20 W. The relative standard deviation for the determination of the five constituents in the samples varied form 0.16-5.47%, and the recovery ranged between 92.0 and 107.3%. Moreover the inclusion constants of the target compounds, except for rhein with beta-CD, were also determined.