甲硝唑的热分解动力学及其含量测定

Application of Thermogravimetry to the Study of Thermal Decom-position Kinetics of Metronidazolum and Its Deter-mination

用热重法 ( TG)研究甲硝唑热分解非等温动力学和与其制剂的稳定性差异 ,并用热重仪测定片剂的含量。推断热分解过程为加速分解反应 ( acceleratedα-tcurve) ,其动力学方程为 :dα/( dt) =Ae- EaRT( 3 α2 /3) ,动力学补偿效应表达式为 :ln A=0 .2 3 4 3 Ea-6.3 1 3 1。实验表明 :甲硝唑具有很高的热解活化能 ,热稳定性好 ;其制剂的热分解活化能稍低 ,对药物的热稳定性影响不大。热重法测定含量与药典法无显著性差异。

Thermogravimetry was used to study the non isothermal decomposition kinetics and the difference of stability between metronidazolum and its excipients and it was also used to determine metronidazolum of excipients. The kinetic equation can be expressed as: dα/(dt)=Ae\+\{-EαRT\}(3α\+\{2/3\}),which corresponds to “the mechanism of accelerated α t curve” , and the mathematic expression of the kinetic compensation effect is found to be: lnA=\{0.2343\}Ea-\{6.3131.\} The results also indicated that metronidazolum has a high activation energy of thermal decomposition, and a good stability; and its excipients have slightly lower activation energy. There is no extraordinary difference between thermogravimetry and pharmacopeia.