Observation of Polymorphic Change through Analysis of FBRM Data: Transformation of Paracetamol from Form II to Form I

In the present research, batch cooling crystallization of paracetamol from ethanol solutions is used as a model system for exploring the utility of focused beam reflectance measurement (FBRM) data in detection of the formation and/or transformations of polymorphs in situ. Paracetamol is known to exist in three different polymorphic forms. The transition between Form I crystals (octahedrons) and Form II crystals (needle-like) is considered here. Such different shapes generate different chord length densities, and by tracking the chord-length density and the total chord counts through an efficient use of the FBRM, we show that it is possible to monitor the transition from Form II to Form I.