The thermal decomposition mechanism of irbesartan

Irbesartan (IBS) is an inhibitor of angiotensin II receptor. In order to study the thermal stability and the thermal decomposition mechanism of IBS, the thermal decomposition processes of IBS in nitrogen and in air atmospheres were studied by means of thermogravimetry (TG) and differential scanning calorimetry (DSC), the evolved gaseous products from thermal decomposition were identified with thermogravimetry coupled with Fourier transform infrared spectroscopy (TG-FTIR), and the residues of thermal decomposition at various temperatures were analyzed with infrared spectra, high-performance liquid chromatography (HPLC) and liquid chromatography-mass spectrometry (LC-MS). The molecular bond orders were calculated by GAMESS program of quantum chemistry, and the thermal decomposition mechanism of IBS was discussed. The results indicated that the thermal decomposition of IBS is a three-stage process and the initial temperatures of the decomposition are 204.7 and 201.0 °C in nitrogen and in air, respectively. The initial step of the decomposition is the partial decomposition of imidazolone and tetrazol sections. The thermal stability of IBS is quite good in the routine temperature.