Characterization of pharmaceutical solvates by combined thermogravimetric and infrared analysis

The combined physical analytical technique of thermogravimetric and infrared analysis (TG/IR) is described for the investigation of pharmaceutical solids. TG/IR provides an unequivocal identification of the volatile content of a pharmaceutical solid. In the case of pharmaceutical solvates, TG/IR provides identification of the evolved gas from the crystalline solid. Variable temperature X-ray diffraction and differential scanning calorimetry techniques provide the required information to ascertain whether the evolved gas was due to a solvent incorporated into the crystal lattice or physically adsorbed onto the solid. This work illustrates three examples of TG/IR as utilized in a multidisciplinary approach to the physical characterization of pharmaceutical solids.