Capabilities of Terahertz Technology in Porosity Estimation of Pharmaceutical Tablets

Terahertz radiation, with frequency from 0.1 to 10 THz, can differentiate materials with different material properties, particularly the refractive index. This property can be extended to identify porosity changes in a material as variations in the porosity levels change the refractive index value of the material. Quantitative assessment of porosity is very important in pharmaceutical tablets since it decides the tablet's disintegration and dissolution and, thereby, the bioavailability of the oral drug. Hence, THz spectroscopy is an excellent tool to probe into the porosity changes and quantitatively estimate the porosity value of the pharmaceutical tablets. Here, a THz frequency domain spectroscopy (FDS) system has been employed for the studies. The material properties of the tablets, in terms of the refractive index values, are extracted from the THz-FDS measurement data. The extracted refractive index value is then employed to quantify the porosity of the tablets. Pharmaceutical ablets compacted at different pressure levels were used in the study. Further, the porosity extracted from the THz measurements has been validated with the nominal porosity estimated by standard methods for these tablets.