Fourier transform infrared spectroscopy as well as X-ray diffraction (XRD) were employed to thoroughly study phase transitions taking place during heating-cooling-heating cycle of carbamazepine (CBZ), a well known and commonly used antiepileptic drug. Both techniques revealed cold crystallization taking place during second heating. Moreover, XRD studies for the first time proved the coexistence of CBZ (form I) and iminostilbene (product of the degradation of CBZ) after a heating-cooling cycle. Moving window two-dimensional correlation (MW 2D-COS) spectroscopy and two-dimensional correlation spectroscopy were shown to be effective tools to reveal phase sequences and to provide information about the order of sequential changes of bands' intensities during each phase transition, respectively.
Keywords: 2D-COS; Carbamazepine; Fourier transform infrared spectroscopy; X-ray diffraction; XRD; degradation; phase transition; two-dimensional correlation spectroscopy.