Process analytical technology-based (PAT) model simulations of a combined cooling, seeded and antisolvent crystallization of an active pharmaceutical ingredient (API)

Crystallization is one of the most important unit operations for production of active pharmaceutical ingredients (API) in pharmaceutical industry. This work studied the impact of solvent chemical composition on fesoterodine fumarate dissolution in 2-butanone/cyclohexane mixtures and seeded cooling crystallization, combining population balance equation (PBE) modelling with experiments. Thermodynamics, transport phenomena and kinetics of nucleation, crystal growth, agglomeration, and dissolution were taken into account, two in-line process analytical technologies (PAT) – attenuated total reflectance Fourier-transform infrared spectroscopy (ATR–FTIR) and focused beam reflectance measurement (FBRM) – were used for monitoring seeded experiments, and non-linear regression analysis was applied for parameter estimation. Cyclohexane not only decreased solute saturated solubility, but increased rates of all mechanisms. Model validation by temperature cycling showed a good agreement between results and simulations which opens up possibilities for further engineered optimization and control. Combined cooling & antisolvent crystallization (CCAC) experiment revealed a complex antisolvent impact on particle dynamics.