A rising temperature kinetic model to describe complex reaction kinetics of a drug: procainamide hydrochloride

The drug, procainamide hydrochloride (NH2C6H4CONHCH2CH2N(CH2CH3)2HCl), was studied using a simultaneous thermogravimetric–differential thermal analysis unit (TG–DTA) in an atmosphere of nitrogen. The study covered the range of temperature from ambient to 800°C. The DTA showed a melting point at 169°C followed by a two stage endothermic transition. The TG–DTG plots clearly showed this two-stage transition. A kinetic analysis of the two stages was attempted. The best fit appeared to be a first order mechanism for both stages. It also was noted that the values of Eact varied as the reaction progressed. Supportive evidence regarding the study was obtained from a range of other physio-chemical measurements.