STUDIES ON THE NON-ISOTHERMAL KINETICS OF THERMAL DECOMPOSITION OF QUINOLONE DRUGS AND THEIR THERMAL STABILITY

AIM　To study the thermal stabilities of quinolone drugs and to establish equations for their decomposition kinetics. METHODS　Using TG(thermogravimetry)-DTG(differential thermogravimetry) to determine the thermal decomposition curves of the drugs and Achar differential method and Coats-Redfern integral method to determine their thermal decomposition functions. RESULTS　Form their TG-DTG curves and IR spectra, the thermal decomposition processes of the four quinolone drugs were deduced and the thermal kinetic parameters, such as energy of activation (E), order of reaction (n), frequency factor (A) and kinetic compensation constants were determined. CONCLUSION　The order of thermal stability is: rufloxacin hydrochloride > enoxacin > ofloxacin > norfloxacin, and the processes of thermal decomposition of the 4 drugs are the same. The thermal stabilities of the capsules of the 4 drugs are all better than the drug materials themselves. The mechanism functions of norfloxacin, enoxacin and ofloxacin are the same, the kinetic equation may be expressed as: dα/dt=Ae^-E/RT(1-α)², while for rufloxacin hydrochloride it is: dα/dt=Ae^-E/RT(1-α)³.