A quantitative comparison of in-line coating thickness distributions obtained from a pharmaceutical tablet mixing process using discrete element method and terahertz pulsed imaging

Pei, Chunlei and Lin, Hungyen and Markl, Daniel and Shen, Yao-Chun and Zeitler, J. Axel and Elliott, James A. (2018) A quantitative comparison of in-line coating thickness distributions obtained from a pharmaceutical tablet mixing process using discrete element method and terahertz pulsed imaging. Chemical Engineering Science, 192. pp. 34-45. ISSN 0009-2509 (https://doi.org/10.1016/j.ces.2018.06.045)

[thumbnail of Pei-etal-CES-2018-in-line-coating-thickness-distributions-obtained-from-a-pharmaceutical-tablet]
Preview
 Text. Filename: Pei_etal_CES_2018_in_line_coating_thickness_distributions_obtained_from_a_pharmaceutical_tablet.pdf
Accepted Author Manuscript
License: Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 logo
Download (488kB)| Preview

Abstract

The application of terahertz pulsed imaging (TPI) in an in-line configuration to monitor the coating thickness distribution of pharmaceutical tablets has the potential to improve the performance and quality of the spray coating process. In this study, an in-line TPI method is used to measure coating thickness distributions on pre-coated tablets during mixing in a rotating pan, and compared with results obtained numerically using the discrete element method (DEM) combined with a ray-tracing technique. The hit rates (i.e. the number of successful coating thickness measurements per minute) obtained from both terahertz in-line experiments and the DEM/ray-tracing simulations are in good agreement, and both increase with the number of baffles in the mixing pan. We demonstrate that the coating thickness variability as determined from the ray-traced data and the terahertz in-line measurements represents mainly the intra-tablet variability due to relatively uniform mean coating thickness across tablets. The mean coating thickness of the ray-traced data from the numerical simulations agrees well with the mean coating thickness as determined by the off-line TPI measurements. The mean coating thickness of in-line TPI measurements is slightly higher than that of the off-line measurements. This discrepancy can be corrected based on the cap-to-band surface area ratio of the tablet and the cap-to-band sampling ratio obtained from ray-tracing simulations: the corrected mean coating thickness of the in-line TPI measurements shows a better agreement with that of the off-line measurements.

ORCID iDs

Pei, Chunlei, Lin, Hungyen, Markl, Daniel ORCID logoORCID: https://orcid.org/0000-0003-0411-733X, Shen, Yao-Chun, Zeitler, J. Axel and Elliott, James A.;
CORE (COnnecting REpositories)