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

Chunlei Pei, Hungyen Lin, Daniel Markl, Yao-Chun Shen, J. Axel Zeitler, James A. Elliott

Research output: Contribution to journalArticle

7 Citations (Scopus)
3 Downloads (Pure)

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.

Original languageEnglish
Pages (from-to)34-45
Number of pages12
JournalChemical Engineering Science
Volume192
Early online date18 Jun 2018
DOIs
Publication statusPublished - 31 Dec 2018

Keywords

  • coating thickness variability
  • discrete element method
  • pharmaceutical coating
  • Terahertz in-line sensing
  • Terahertz pulsed imaging

Fingerprint Dive into the research topics of 'A quantitative comparison of in-line coating thickness distributions obtained from a pharmaceutical tablet mixing process using discrete element method and terahertz pulsed imaging'. Together they form a unique fingerprint.

  • Cite this