On-line observation of the crystal growth in the case of the non-typical spherical crystallization methods of ambroxol hydrochloride

Design, Development, and Analysis of an Automated Sampling Loop for Online Monitoring of Chiral Crystallization

Enantiomeric purity is of prime importance for several industries, specifically in the production of pharmaceuticals. Crystallization processes can be used to obtain pure enantiomers in a suitable solid form. However, some process variants inherently rely on kinetic enhancement (preferential crystallization) of the desired enantiomer or on complex interactions of several phenomena (e.g., attrition-enhanced deracemization and Viedma ripening). Thus, a process analytical technology able to measure the enantiomeric composition of both the solid phase and the liquid phase would be valuable to track and eventually control such processes. This study presents the design and development of a novel automated analytical monitoring system that achieves this. The designed setup tracks the enantiomeric excess (ee) using a continuous closed-loop sampling loop that is coupled to a polarimeter and an attenuated total reflection Fourier transform infrared spectroscopy spectrometer. By heating the loop and alternately sampling either the liquid or the suspension, the combination of these measurements allows tracking of the ee of both the liquid and the solid. This work demonstrates a proof of concept of both the experimental and theoretical aspects of the new system.

Design of Experiments for Optimization of the Lactose Spherical Crystallization Process

This study provides a comprehensive assessment of the parameters of the spherical crystallization process and their impact on the micromeritic properties of lactose spherical agglomerates. A recently introduced definitive screening design was used to study various process parameters, with particular focus on building predictive models. The parameters included were: lactose solution concentration; volume ratio between the antisolvent and the whole crystallization system; crystallization system temperature; velocity of the addition of the lactose water solution; agitation velocity; and agitation time after whole addition of the lactose solution. Their effects on process yield, particle size parameters D10, D50 and D90, particle size distribution, morphological properties (roundness, solidity) and Hausner ratio were studied. Active effects were identified for all of these responses, with quadratic and interaction effects included. Lactose concentration, volume ratio, crystallization system temperature, and agitation velocity were identified as critical process parameters. For every response, a statistical model was built, where those for Hausner ratio, yield and roundness provided the best predictive performances. Based on these models, D10 and yield were successfully optimized. Definitive screening design proved as useful especially in the screening phase; however, additional experiments are needed to build models with high predictive power for all of these responses.