Abstract: Thermal decomposing curves of triptolide and triptonide in different heating speeds were obtained in the nitrogen atmosphere by TG-DTG and DTA-DDTA techniques to study their thermal stability,decomposition kinetics and shelflife under the heat condition.Four thermal analysis kinetic methods (Kissinger,Ozawa,Coats-Redfern and Achar) were used to speculate the probable mechanism of thermal decomposing reaction and the kinetic parameters.The shelflife of triptolide and triptonide at room temperature (25 ℃) was calculated by the kinetic parameters of the first stage.The TG-DTG curves of triptolide showed two steps.The temperature range of the first step was from 200 ℃ to 340 ℃ and the temperature range of the second step was from 340 ℃ to 440 ℃.The total weight loss rate of triptolide was 85.5%.The DTA-DDTA curves showed an endothermic peak at about 232 ℃ and an exothermic peak at about 298 ℃.The TGDTG curves of triptonide also showed two steps.The temperature range of the first step was from 200 ℃ to 290 ℃ and the temperature range of the second step was from 290 ℃ to 490 ℃.The total weight loss rate of triptonide was 64.4%.The DTA-DDTA curves showed an endothermic peak at about 252 ℃ and an exothermic peak at about 280 ℃.The most probable kinetic mechanisms of the first stage thermal decomposition of triptolide was chemical reaction and the corresponding mechanisms followed reaction order equation.The average apparent activation energy Ea was 136.66 kJ/mol and the logarithm of preexponential factor lnA was 26.47.The most probable kinetic mechanisms of the first stage thermal decomposition of triptonide was chemical reaction and the corresponding mechanisms followed second order reaction equation.The average apparent activation energy Ea was 127.19 kJ/mol for the first step.The logarithm of preexponential factor lnA was 25.23 for the first step.The theoretical shelflife of triptolide and triptonide at room temperature were about 4-5 years.These results provided reference for the quality control and preparation and processing research of the related drug contained triptolide and triptonide.

Key words: triptolide, triptonide, thermal analysis, thermal decomposition kinetics