Study on the thermal performance of carbamazepine at different temperatures, pressures and atmosphere conditions

•The type of DSC pan can affect both the atmosphere and pressure in an experiment.•Carbamazepine is prone to degrade at temperatures close to the melting point when heated in a hermetically sealed system.•Special attention should be paid to the measurement conditions when examining the thermal behavior of strongly sublimating APIs. The aim of this study was to assess the impact of a sample pan together with the atmosphere of the measurement on the kinetics of thermal degradation of the strongly sublimating, antiepileptic drug – carbamazepine (CBZ). The fusion-cooling or annealing-cooling cycle was conducted under inert gas or an oxidative atmosphere for samples that were placed in either open or hermetically sealed pans. The thermal behavior of the samples was investigated using DSC, HPLC and ATR FT-IR spectroscopy. The samples that were fused or annealed in the open pans underwent only a phase transition, whereas these that were treated in the hermetically sealed pans partially degraded. Furthermore, when performing the TGA measurements coupled with FT-IR, there were no differences in the degradation kinetics between the inert gas and oxidative atmosphere up to 650 K. Above that temperature, there was an additional weight loss, associated with the combustion of an organic residue, for the sample that was heated in the oxidative atmosphere.