An experimental study has been conducted to evaluate the capability of a seeded batch cooling crystallization with a temperature cycling method to produce a narrow crystal size distribution and grow a desired polymorphic form of sulfathiazole crystals. The study used focused beam reflectance measurement (FBRM), and attenuated total reflectance ultraviolet/visible (ATR-UV/Vis) spectroscopy for the in-situ monitoring and control of the process. Results of the experiments show that only seeds of form I were able to be grown from n-propanol and the application of temperature cycling helped in enhancing the size uniformity of the product. Results also show that the temperature cycling method has a good prospect to be implemented for the control of polymorphic purity. The inability of the seeds of form II and form III to grow in n-propanol may be due to the presence of impurities in the system.
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