Use of a TG/DTA/Raman system to monitor dehydration and phase conversions

Use of a TG/DTA/Raman system enabled real time collection of Raman spectra during the dehydration of Risedronate, the active pharmaceutical ingredient in the osteoporosis drug Actonel. Raman spectra collected during the dehydration of this material show a crystal lattice adjustment below the boiling point of water facilitating interpretation of the TG/DTA thermal profile. Raman spectra also revealed recrystallization processes subsequent to loss of lattice water that were not evident in the thermal analysis profile. Spectral evidence showing the formation and disappearance of a second hydrate form are observed during the dehydration of this material. In addition, spectral evidence indicating the presence of an anhydrate form of this material are observed prior to thermal induced degradation of this material.