Time-resolved X-ray scattering using synchrotron radiation applied to the study of a polymorphic transition in carbamazepine

The thermodynamic status of alpha -carbamazepine has been clarified using equilibrium solubility measurements, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), heated X-ray powder diffraction (XRPD), and temperature-controlled X-ray scattering techniques. alpha -Carbamazepine is the least stable of the three well-characterized anhydrous polymorphs of carbamazepine at 25 degreesC. In addition, it was confirmed that alpha -carbamazepine undergoes an exothermic transition to gamma -carbamazepine at 130 degreesC. The novel technique of time-resolved simultaneous small- and wide-angle X-ray scattering has been successfully applied to monitor this transition in situ. It was concluded that alpha -carbamazepine has a monotropic relationship with gamma -carbamazepine. (C) 2001 Wiley-Liss, Inc. and the American Pharmaceutical Association.