Screening and Selective Preparation of Polymorphs by Fast Evaporation Method: A Case Study of Aspirin, Anthranilic Acid, and Niflumic Acid
journal contributionposted on 06.06.2012, 00:00 by Partha Pratim Bag, C. Malla Reddy
We show the preferential formation and scalability of two known polymorphs, I and II, of aspirin from acetone (at 50 °C) and dichloromethane (at 5 °C) solutions, respectively, and two known forms I (from water at 50 °C) and II (from methanol at 50 °C) of anthranilic acid with high purity by fast evaporation (FE) of solvent using rotary evaporation technique. The FE method also provided a means to identify a previously unknown form II of niflumic acid (NFA). The NFA form II, which is characterized by DSC, TGA, IR, and PXRD, could not be detected either by slow evaporation or liquid assisted grinding methods upon screening from a variety of solvents. The results demonstrate the efficiency and complementarity of the FE method to the existing techniques for selective preparation and scale up of API polymorphic forms.