Kinetic study of the drug acetazolamide using thermogravimetry

The drug acetazolamide (C4H6N4O3S2) was studied using a simultaneous thermogravimetric–differential thermal analysis (TG–DTA) unit. The study covered the temperature range of ambient to 600 °C. The DTA showed a melting point of 258.5 °C followed by a three-stage decomposition. The TG–DTG plots clearly show the decomposition when subjected to heat treatment in a nitrogen atmosphere. A kinetic analysis of all stages was attempted, where a zero-order process appeared to be the best fit mechanism and plots of ln k versus T−1 show this. The values of Eact are shown to vary throughout each stage as the reaction progressed.