The thermal behavior of five free anthraquinones (chrysophanol, emodin, physcion, aloe-emodin, and rhein) from rhubarb had
been investigated using TG, DTG and DTA technique. The results show that all the free anthraquinones have the similar TG and
DTG curve shapes, however, due to the substituted groups attached on the skeleton of 1,8-dihydroxy anthraquinone are different,
every anthraquinone has different mass loss features. Moreover, all the DTA curves of these free anthraquinones have two obviously
characteristic peaks, but with special curvilinear types, peak location and peak values. Therefore, thermal analysis (TA)
characteristics of anthraquinones above mentioned could be established, and it is possible to easily distinguish these anthraquinones
by using TA technique.