Advances in terahertz time-domain spectroscopy of pharmaceutical solids: A review

The rapid development of terahertz time-domain spectroscopy (THz-TDS) as a highly versatile analytical tool for the characterisation of pharmaceutical materials has drawn considerable attention over the past two decades. In this review an overview of the current advances in the use of THz-TDS for the characterisation of small organic molecular crystals and their solid-state modifications, the characterisation of amorphous drug products as well as biopharmaceutical solid state formulations are presented. In addition, due to its low absorption from typical pharmaceutical excipients and the low scattering losses given the relatively long wavelength, THz-TDS can be used for non-destructive porosity measurement and characterisation of the microstructure of tablet matrices. The method and its applications are introduced and explained in the context of complementary characterisation techniques. (c) 2021 Elsevier B.V. All rights reserved.