Terahertz surface refractive index maps of biconvex (top) and flat faced (bottom) tablets compacted at different compression forces.
A paper published by the Terahertz Applications Group earlier in the year was selected by the editors of the Journal of Pharmaceutical Sciences as their pick of the most original and most significant scientific findings published in the preceding three issues (July 2013 - September 2013).
The featured paper is Hardness and density distributions of pharmaceutical tablets measured by terahertz pulsed imaging, by Robert K. May, Ke Su, Lianghao Han, Shuncong Zhong, James A. Elliott, Lynn F. Gladden, Mike Evans, Yaochun Shen, J. Axel Zeitler, Journal of Pharmaceutical Sciences, Volume 102, Issue 7, pages 2179–2186, July 2013
The abstract for this paper is:
We present terahertz pulsed imaging (TPI) as a novel tool to quantify the hardness and surface density distribution of pharmaceutical tablets. Good agreement between the surface refractive index (SRI) measured by TPI and the crushing force measured from diametral compression tests was found using a set of tablets that were compacted at various compression forces. We also found a strong correlation between TPI results and tablet bulk density, and how these relate to tablet hardness. Numerical simulations of tablet surface density distribution by finite element analysis exhibit excellent agreement with the TPI measured SRI maps. These results show that TPI has an advantage over traditional diametral compression and is more suitable for nondestructive hardness and density distribution monitoring and control of pharmaceutical manufacturing processes