Purpose: Polymorphic transformations during the wet granulation of a metastable polymorph of flufenamic acid were monitored in situ using online X-ray powder diffraction. The resulting data were used in testing a proposed process induced transformation rate model, which allows the extent and occurrence of polymorphic transformations during wet granulation to be controlled by adjusting the granulation time.
Methods: A small-scale, top mixing granulator was designed for compatibility with novel X-ray powder diffraction equipment (available from X-Ray Optical Systems of East Greenbush, NY).
Results: The unique polycapillary optic and X-ray source allowed the transformation of the metastable to the stable polymorph to be followed during the granulation. Following a diffraction peak each for the metastable and stable forms demonstrated that polymorphic transformations during the wetting phase of granulation follow the trends predicted by the model.
Conclusions: The advanced online monitoring may allow real-time control of the process by the adjustment of process parameters, such as granulation time, and clearly qualifies as a PAT (process analytical technology).