Nonisothermal methods

Kinetic studies at several temperatures followed by application of the Arrhenius equation as described constitutes the usual procedure for the measurement of activation parameters, but other methods have been described. Bunce et al. eliminate the rate constant between the Arrhenius equation and the integrated rate equation, obtaining an equation relating concentration to time and temperature. This is analyzed by nonlinear regression to extract the activation energy. Another approach is to program temperature as a function of time and to analyze the concentration-time data for the activation energy. This nonisothermal method is attractive because it is efficient, but its use is not widespread. ... 

Nonisothermal methods for stability prediction use a temperatureprogramming oven to control the storage environment. Application of nonisothermal stability testing to a drug may provide stability information more quickly than but not as accurately as the isothermal method. 

N. Okusa and K. Kinuno, Kinetic studies on prediction of stability of pharmaceuticals. 1. Kinetic analysis by a nonisothermal method [in Japanese], Yakuzaigaku 28, 17-20(1968). 

I. Utsumi, I. Sugimoto, M. Kobayashi, and M. Ohtsuka, Estimation of the stability of pharmaceutical by nonisothermal method [in Japanese], Yukuzaigaku 34, 173-179(1974). 

N. Okusa, Prediction of stability of drugs. Iv. Prediction of stability by multilevel nonisothermal method, Chem. Pharm. Bull. 23, 803-809(1975). 

It is possible to determine the reaction onset temperature (T0) very precisely by nonisothermal methods, which is almost impossible to do by the isothermal method. The zero-time error is therefore absent. 

In another investigation, Gallagher and Johnson (147) compared isothermal and nonisothermal methods to study the reaction kinetics of the thermal decomposition of CaC03. According to isothermal kinetics studies, the reaction... 

The isothermal method should be used when the melting temperature of the sample is known and a better understanding is needed of the degradation of the material. The nonisothermal method should be used when the degradation temperature is not known. 

The kinetics of thermal degradation have generally been studied using isothermal and nonisothermal methods. In earlier literature, isothermal methods were mostly employed for the study of the kinetics of solid-state reactions. During the past three decades, however, nonisothermal methods, for example, the Doyle method [17, 18], Freeman and Carroll method [19], Coats and Redfem method [24], Ozawa method [20], Flynn and Wall method [21, 22], Friedman method [25], and Kissinger method [26], have received more attention. 

The generalized kinetic expression for the nonisothermal methods is as follows ... 

Ming Chen and Chia-Ting Chung. "Analysis of crystallization kinetics of poly(ether ether ketone) by a nonisothermal method." Journal of Polymer Science Part B Polymer Physics, pp. 2393-2399,1998. 

J. Kemeny, J. Sestak Comparison of crystallization kinetic theories derived by isothermal and nonisothermal methods Thermochim. Acta 110(1987)113... 

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