Characteristics of Thermal Analysis Patterns of Free Anthraquinones from Rheum

In comparison with those of 1,8-dihydric anthraquinones,the characteristic TG-DTA curves of the free anthraquinones(Rhein,Emodin,Aloe-emodin,Chrysophanol and Physcion) from Rheum were determined.The results showed that they had similar TG curves.However,due to the different substituents(attached) on the 1,8-dihydrox anthraquinones,each sample had different weight loss.On the DTA curves of free anthraquinones,there are two obviously characteristic peaks,while there are obviously differences(between) their curve shapes,peak location and peak values,therefore,free anthraquinones distilled and sublimated from Rheum can be determined by TG-DTA.