Laser Raman investigation of drug-polymer conjugates: sulfathiazole-povidone coprecipitates.

Laser Raman spectroscopy is used for the investigation of the drug-polymer conjugates, sulfathiazole-povidone. Specifically, Raman spectra, both in the lattice vibration and the intramolecular vibration regions, are used to characterize various polymoprhic forms of sulfathiazole. It is found that sulfathiazole exists in two unsolvated forms, untreated sulfathiazole and another form grown from propanol. The crystals grown from ethanol include varying amounts of ethanol depending on the growth condition. The nature of the povidone-sulfathiazole coprecipitates of various compositions are studied. We find no evidence of any new polymorphic form of sulfathiazole in these coprecipitates. The coprecipitates are found to consist of one of the unsolvated forms of sulfathiazole.