Identification of the Polymorphs of Sulfamethoxydiazine by Optical and Morphological Methods

Abstract

Refractive indices and related optical properties of 3 polymorphs and 2 solvates of sulfamethoxydiazine were determined by a polarizing microscope. A morphological measurement was also made for form I and III by a goniometer. All these data were useful for the simple and rapid identification of each form of sulfamethoxydiazine in a hospital pharmacy using a polarizing microscope. Especially the differences in key refractive indices between form II, the most active one, and form I or III are advantageous for discriminating form II from other less active forms in pharmaceutical preparations. Transition behaviors were also examined using a heating stage, from which the stability of 3 polymorphic forms were determined.