Optimization of API Drying Via Hemi-Solvate Conversion Kinetics

Drying of an early stage API candidate required excessively long cycle times in the pilot plant filter dryer. Investigation of the drying curve revealed the rate-limiting step was desolvation, as opposed to removal of unbound ethanol solvent. Intrinsic kinetics were then developed for the ethanol hemi-solvate as a funtion of temperature, and compared to the apparent kinetics derived from the pilot scale dryer. Mass spectrometry and Raman spectroscopy PATs supplemented the kinetic study to elucidate a more fundamental understanding of the form conversion. The results were combined to optimize drying conditions on scale, and model the time needed to reach an API dryness of 0.1 wt%.