Quantitative phase analyses through the Rietveld method with X-ray powder diffraction data of heat-treated carbamazepine form III.

The present work shows that the heated carbamazepine (CBZ) powder form III can be described as purely triclinic form I or a mixture of triclinic form I and monoclinic form III, depending on the resolution of the X-ray diffraction equipment used. Visual identification of the minor phase is possible when high-resolution synchrotron light is used. Quantitative phase analyses of CBZ forms I and III, after thermal treatment, were performed by using both synchrotron and conventional copper rotating anode X-ray powder diffraction data and the Rietveld method. Also, the Rietveld method could be adequately applied to determine the phase percentage in the heated material, even when usual resolution data are acquired.