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
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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

Using Terahertz Spectroscopy for Observing the Kinetics of Recrystallisation of Polybutene-1

Journal of Infrared, Millimeter, and Terahertz Waves

February 2013, Volume 34, Issue 2, pp 187-193
doi: 10.1007/s10762-013-9956-8

Authors: V. Křesálek, T. Gavenda
More details at: http://link.springer.com/article/10.1007/s10762-013-9956-8

Abstract

This paper deals with the use of terahertz spectroscopy for observing the kinetics of recrystallisation of polybutene-1 as a suitable material for manufacturing optical elements in the terahertz region of the electromagnetic spectrum. These materials were studied from the perspective of their optical properties – the refractive index and the absorption coefficient. The time dependencies of the refractive index and the absorption coefficient were measured, because polybutene-1 is a material which recrystallises for a number of days from the date of its manufacture. The coefficients describing the recrystallisation process were calculated from the fitting function derived from the Avrami equation. In this paper, the measurement results are presented and the possibilities of the use of the studied materials are discussed.

...Measurement was conducted by a TPS^TM Spectra 3000...Thickness was measured at 12 points of each sample to achieve the desired accuracy, after averaging the measured values. The calculation of the refractive index and absorption coefficient was performed with the TPS^TM Spectra 3000 software, with air as the reference value...