ABSTRACT
The nonisothermal thermogravimetric decomposition of amitriptyline hydrochloride was investigated under pure nitrogen atmosphere at four different heating rates (β =5, 10, 15, 20oC min-1). Friedman, Flynn-wall-Ozawa, and Tang isoconversional methods were used to calculate the activation energy Ea. The results obtained was compared with that obtained by the distributed activation energy model, Miura procedure. Activation energy, Ea, results showed that the isoconversional kinetic methods used (Friedman, Flynn-Wall-Ozawa and Tang methods) were in good agreement with each other, together with the distributed activation energy model. It was found that the activation energy Ea was not really changed and was almost independent with respect to the level of conversion (α). This result suggests that the nonisothermal decomposition process of amitriptyline hydrochloride follows a single-step reaction. The master-plots were used to obtain the reaction kinetic model, which was confirmed by the integral composite I method. The kinetic triplet determined was, activation energy, Ea = 74.68 kJmol-1 , pre-exponential factor, A= 3.71×103 min-1 and the reaction kinetic model follows the Avrami-Erofeev model, (nucleation and growth) , A4, f(α)= 4(1-α)[-ln(1-α)]3/4 , g(α) =[-ln(1-α)]1/4 .