MSMPR Studies of Ciprofloxacin From Pure API and From Crude API: The Role of Impurities on Solubility and Kinetics

Despite the known effects of foreign species on crystallization and the frequently large number of impurities present in multistep pharmaceutical syntheses, the early characterization of continuous crystallization operations may be limited by the availability of representative crude material. As part of the development of an end-to-end process for ciprofloxacin HCl monohydrate, this work evaluates the impact of upstream impurities on mixed-suspension, mixed-product removal (MSMPR) crystallization kinetics. The kinetic parameters for nucleation and crystal growth in MSMPR crystallization have been estimated for the commercial, purified active pharmaceutical ingredient (API), as well as crude API containing approximately 60 unknown impurities. Results show that, while the upstream impurities did not have a significant impact on the nucleation rate, both the temperature-dependent growth rate coefficient and the growth activation energy decreased in crude API crystallization. This behavior implies that the ef...