Crystallization of selective polymorph using relationship between supersaturation and solubility

For polymorph screening, the plot of ΔC met /C c against C * /C c in nucleation kinetics was investigated. The polymorph screening for forms I and II and amorphous form of clopidogrel hydrogen sulfate was carried out according to the nucleation kinetics expressed by this plot. The stability order of polymorphs for famotidin was also predicted successfully by this model. This model was used in the expectation of supersaturation level for polymorphic formation. Two types of polymorphic crystallization: transformation from metastable form to stable form and nucleation and growth of polymorphic form without transformation can be explained. Amorphous form was also expected by this model. Even though polymorphs depend on lots of crystallization parameters such as solvent, temperature, concentration, cooling rate, and so forth, plot of ΔC met /C c and the C * /C c in various nucleation kinetics gives a guide line for screening of polymorph.