Spectrophotometric Determination of Total Anthraquinones in Rhubarb with Ultrasonic Extraction

Sample of rhubarb was extracted thrice for 20 min each with ethanol-water (6+4) mixture solution ultrasonic ally. The content of total anthraquinones in the extract was determined by spectrophotometry using 1,8-dihydroxy-anthraquinone as standard sample at the wavelength of 428 nm. Under the optimum condition, linear relationship between values of absorbance and mass concentration of 1,8-dihydroxy-anthraquinone was kept in the range within 50.0 mg·L-1. The proposed method was applied to the determination of total anthraquinones in rhubarb; the average extraction rate obtained was in consistency with that obtained by reflux extraction method. Test for recovery was made by standard addition method, and values of recovery obtained were in the range of 99.7%-100.5%.