Thermoanalytical study of a new norfloxacin solvate

Abstract

The identification and structural and thermal characterization of new polymorphs and pseudopolymorphs (solvates) is of great importance, since each crystalline phase can present significant differences in their physicochemical properties. This work reports the formation of a new non-stoichiometric solvate (1:0.2 n/n) of norfloxacin (a broad-spectrum antibiotic) with ethanol synthesized by mechanochemical method. Based on the thermal analysis (TG-DTA, DSC and DSC-microscopy), and with the aid of infrared vibrational spectroscopy (FTIR) and Powder X-Ray Diffraction (PXRD) it is shown that after the loss of solvent the polymorphic form C was formed, which changes to polymorphic form A at 209 °C, a process not yet reported. In addition, FTIR data show that the norfloxacin molecule is present in solid state in zwitterionic form (solvate and form C) and in nonionized form (form A).