Quantitative Mapping of Pharmaceutical Cocrystals Within Cellulose by Terahertz Spectroscopy

Terahertz (THz) spectroscopy is a powerful tool for identifying inter-molecular hydrogen bonds in pharmaceutical materials. Here, we present quantitative chemical imaging of multicomponent pellets composed of pharmaceutical cocrystals and cellulose by THz spectroscopy. The stabilized THz time-domain spectroscope with laser beam monitoring and feedback supports accurate absorption spectra measurement. The linearity of THz absorptions of cocrystals and cellulose against the concentration are experimentally verified. In addition, the concentrations of the materials inside pellets are quantitatively extracted and mapped from the THz spectroscopic image by linear regression using reference THz spectra obtained for cocrystals and diluents.