Impact of Processing Conditions on Inter-tablet Coating Thickness Variations Measured by Terahertz In-Line Sensing

HUNGYEN LIN, ROBERT K. MAY, MICHAEL J. EVANS, SHUNCONG ZHONG, LYNN F. GLADDEN, YAOCHUN SHEN,

J. AXEL ZEITLER

Abstract

A novel in-line technique utilising pulsed terahertz radiation for directmeasurement 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. C⃝ 2015 Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci

This study was performed using TeraView's Spectra 3000 system. (TeraView, Cambridge, UK)

Full Article: http://onlinelibrary.wiley.com/doi/10.1002/jps.24503/full

Teraview at The American Coatings CONFERENCE 2014

TeraView are please to announce that they will be attending the American Coatings CONFERENCE on April the 7-9, 2014 in the Georgia World Congress Centre.

TeraView's Rob May and Ian Grundy will be in attendance, with Rob May presenting the following talk:

Title: Non-Contact, Substrate-Independent, Multi-Layer Paint Thickness Sensor

Session: 3.3

Date: 7th of April 2014

Time: 3:00-3:30 pm

Room: C208-210

For further information visit: http://www.american-coatings-show.com/en/conference

Application of terahertz pulsed imaging to analyse film coating characteristics of sustained-release coated pellets

• M. Haaser^a, b, c, 
• Y. Karrout^d, 
• C. Velghe^d, 
• Y. Cuppok^d, 
• K.C. Gordon^e, 
• M. Pepper^c, f, 
• J. Siepmann^d, 
• T. Rades^a, g, , , 
• P.F. Taday^c, 
• C.J. Strachan^a, h

• ^a School of Pharmacy, University of Otago, Dunedin, New Zealand
• ^b Cavendish Laboratories, University of Cambridge, Cambridge, United Kingdom
• ^c TeraView Ltd., Cambridge, United Kingdom
• ^d College of Pharmacy, Université Lille Nord de France, Lille, France
• ^e Department of Chemistry and MacDiarmid Institute, University of Otago, Dunedin, New Zealand
• ^f Department of Electronic Engineering, University College London, London, United Kingdom
• ^g Department of Pharmacy, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
• ^h Division of Pharmaceutical Technology, Faculty of Pharmacy, University of Helsinki, Helsinki, Finland
• • http://dx.doi.org/10.1016/j.ijpharm.2013.05.039, How to Cite or Link Using DOI

 Abstract

Terahertz pulsed imaging (TPI) was employed to explore its suitability for detecting differences in the film coating thickness and drug layer uniformity of multilayered, sustained-release coated, standard size pellets (approximately 1 mm in diameter). Pellets consisting of a sugar starter core and a metoprolol succinate layer were coated with a Kollicoat^® SR:Kollicoat^® IR polymer blend for different times giving three groups of pellets (batches I, II and III), each with a different coating thickness according to weight gain. Ten pellets from each batch were mapped individually to evaluate the coating thickness and drug layer thickness between batches, between pellets within each batch, and across individual pellets (uniformity). From the terahertz waveform the terahertz electric field peak strength (TEFPS) was used to define a circular area (approximately 0.13 mm²) in the TPI maps, where no signal distortion was found due to pellet curvature in the measurement set-up used. The average coating thicknesses were 46 μm, 71 μm and 114 μm, for batches I, II and III respectively, whilst no drug layer thickness difference between batches was observed. No statistically significant differences in the average coating thickness and drug layer thickness within batches (between pellets) but high thickness variability across individual pellets was observed. These results were confirmed by scanning electron microscopy (SEM). The coating thickness results correlated with the subsequent drug release behaviour. The fastest drug release was obtained from batch I with the lowest coating thickness and the slowest from batch III with the highest coating thickness. In conclusion, TPI is suitable for detailed, non-destructive evaluation of film coating and drug layer thicknesses in multilayered standard size pellets.

...Samples were measured on a TPI imaga 2000 (Teraview Ltd., Cambridge, UK).

You can download the article on ScienceDirect

• 
  

Critical factors in the measurement of tablet film coatings using terahertz pulsed imaging

Authors: Daniela Brock, J. Axel Zeitler, Adrian Funke, Klaus Knop, Peter Kleinebudde,
Article first published online: 5 APR 2013; Journal of Pharmaceutical Sciences; DOI: 10.1002/jps.23521
+Wiley Textbooks Periodicals, Inc.

More info at:
http://onlinelibrary.wiley.com/doi/10.1002/jps.23521/abstract

Abstract

The present work gives an insight into some key measurement and signal processing considerations in terahertz pulsed imaging (TPI). TPI is increasingly used for the measurement of the spatial variation of coating thickness on coated solid dosage forms. The potential of TPI for the assessment of coating thickness distributions and the use in process development is described in recent literature. However, some critical factors need to be taken into account when working with this technique. These are (1) the signal processing of the raw data, (2) the influence of the composition of the sample matrix on the TPI signals and subsequent coating analysis, (3) signal distortions that can occur at tablet edges or areas with defects, and (4) the refractive index as a key parameter in the quantification of layer thickness. In this paper, we will highlight to what extent these factors impact on the qualitative and quantitative analysis of TPI data and how artifacts and misinterpretation of data can be avoided to ensure fully quantitative and robust measurements.

More about terahertz pulsed imaging for the study of Pharmaceutical tablets:
http://www.teraview.com/applications/pharmaceutical/terahertz-pulsed-imaging.html