Crystal modifications of 5-flurouracil-preparation and characterization.

The present study reports the identification and characterization of different crystal modifications of 5-Flurouracil. The drug was found to exist in five polymorphic and one solvatomorphic form. The lyophillization method was employed to reduce the crystallanity of commercial sample which resulted in Form VI. SEM was used to clarify the crystalline shapes characteristic of the drug and its crystal modifications. The melting temperature determined from DSC studies suggests them to be different crystal form while TGA reveals Form III to be acetonitrile solvate. Some major differences were found in the FTIR spectra of various forms. Appearance of new peaks in the XRD pattern reveals formation of new forms which are crystalline in nature. The further differentiation of polymorphic forms was performed by determining the enthalpy of solution in the given solvent which is based on differences in the lattice energy. Significant differences in the heat of solution of various modifications were observed. Acetonitrile solvate was found to be most crystalline and form prepared by lyphollizaiton was found to be least crystalline. Of all the methods, heat of solution provides the quantitative estimation which confirms the presence of different crystal modifications. [ABSTRACT FROM AUTHOR]