Lin, Hungyen and May, Robert K. and Evans, Michael J. and Zhong, Shuncong and Gladden, Lynn F. and Shen, Yaochun and Zeitler, J. Axel
http://strathprints.strath.ac.uk/53773/
A novel in-line technique utilising pulsed terahertz radiation for direct measurement of the film coating thickness of individual tablets during the coating process was previously developed and demonstrated on a production-scale coater. Here, we use this technique to monitor the evolution of tablet film coating thickness and its inter-tablet variability during the coating process under a number of different process conditions that have been purposefully induced in the production-scale coating process. The changes that were introduced to the coating process include removing the baffles from the coater, adding uncoated tablets to the running process, halting the drum, blockage of spray guns and changes to the spray rate. The terahertz sensor was able to pick up the resulting changes in average coating thickness in the coating drum and we report the impact of these process changes on the resulting coating quality.
Hungyen Lin,Yue Dong, Yaochun Shen, Axel J. Zeitler,
https://www.repository.cam.ac.uk/handle/1810/248408?show=full
Spectral domain optical coherence tomography (SD-OCT) has recently attracted a lot of interest
in the pharmaceutical industry as a fast and non-destructive modality for quantification of thin
film coatings that cannot easily be resolved with other techniques. Due to the relative infancy of
this technique, much of the research to date has focused on developing the in-line
measurement technique for assessing film coating thickness. To better assess OCT for
pharmaceutical coating quantification, this paper evaluates tablets with a range of film coating
thickness measured using OCT and terahertz pulsed imaging (TPI) in an off-line setting. In
order to facilitate automated coating quantification for film coating thickness in the range of 30 to
200 μm, an algorithm that uses wavelet denoising and a tailored peak finding method is
proposed to analysis each of the acquired A-scan. Results obtained from running the algorithm
reveal an increasing disparity between the TPI and OCT measured intra-tablet variability when
film coating thickness exceeds 100 μm. The finding further confirms that OCT is a suitable
modality for characterising pharmaceutical dosage forms with thin film coatings while TPI is well
suited for thick coatings.
