Investigation of the polymorphism of sulfathiazole by a combined DSC-HSM approach

A combination of differential scanning calorimetry (DSC) and hot-stage microscopy (HSM) has been used to investigate the polymorphism of sulfathiazole. The approach provides a unique insight into the polymorphic transformations and thermal behaviour exhibited by this compound. The results of the experiments show that sulfathiazole tends to crystallize as mixtures of polymorphs, although the literature methods of producing pure polymorph were followed. The use of light intensity profile obtained from the HSM images, as an alternative way to present results of HSM analysis is also introduced here. It was found to correspond very well with the DSC thermogram.