Using terahertz time-domain spectroscopy to identify pharmaceutical cocrystals

The conversion of polycrystalline pharmaceutical materials into their cocrystals has been monitored using terahertz (THz) spectroscopy. Eight cocrystal systems have been studied and their THz spectra were found to exhibit differences from the constituent materials. Cocrystals of theophylline and DL and L forms of malic acid were clearly differentiated using THz spectroscopy while powder X-ray diffraction (PXRD) results were less conclusive.