Using nor-isothermal method on kinetic parameters of degradation of aspirin

Key words: 
• nor-isothermal method /
• isothermal method /
• kinetic parameter /
• aspirin /
• degradation

Abstract: Objective: To study the kinetic parameters of degradation of aspirin by the nor-isothermal method(and Compare with isothermal method),To researched the accuracy and credibility of the method. Methods: Aspirin was used as a model drug.Under certainly experiment conditions,the stability of aspirin was studied by the nor-isothermal method which was defined as a linear relationship between time and temperature.The value of activation energy(Ea) and frequency factors(A) were calculated by applying the nonlinear least-square method. Results: The degradation of aspirin was attributed to pseudo first order reaction.The Ea values calculated by the nor-isothermal method were 16.13(pH 2)、18.19(pH 4) and 23.87(pH 6) kJ/mol(the mean values of Ea at 5 ℃/h and 10 ℃/h) respectively.The corresponding isothermal method values were 16.12(pH 2),18.01(pH 4) and 23.93(pH 6) kJ/mol respectively. Conclusion: The results indicated that the kinetic parameter determined by the nor-isothermal method was in good accord with that of isothermal method.These results indicated that the nor-isothermal method described in this study could be adequately used for the stability study and was a rapid and accurate method for the determination of kinetic parameters.