Department of Physics and Mathematics, University of Eastern Finland, P.O. Box 111, FI-80101 Joensuu, Finland.
Appl Spectrosc. 2010 Jan;64(1):127-31. doi: 10.1366/000370210792966170.
The terahertz measurement technique has become popular in the field of pharmaceutical technology for tablet quality inspection. Spectral data obtained from the tablets is based on the utilization of Fresnel's formulas for an ideal slab. However, a tablet is a porous medium. Hence, in the THz gap one has to assume that a tablet constitutes at least an effective medium if the Fresnel theory is applied in quantitative permittivity spectra analysis. Hence, it is suggested that one should consider instead of the permittivity of homogeneous media the concept of effective permittivity in the THz terminology of porous tablets. Usually the fill factor of a component of a tablet is known but not the detailed bulk structure. Nevertheless, it is possible to estimate the complex effective permittivity of a tablet with the aid of so-called Wiener bounds. The idea of this article is to present a modification of Wiener bounds applied to the estimation of the real and imaginary part of the permittivity of the pure component of a tablet. As an example, the effective complex permittivity of a starch acetate tablet is considered.
太赫兹测量技术在药物技术领域已成为片剂质量检测的热门技术。从片剂获得的光谱数据基于对理想平板的菲涅尔公式的利用。然而，片剂是多孔介质。因此，在太赫兹间隙中，如果应用菲涅尔理论进行定量介电谱分析，那么片剂至少构成有效介质。因此，有人建议，应该考虑多孔片剂的太赫兹术语中的有效介电常数，而不是均匀介质的介电常数。通常片剂中某一成分的填充因子是已知的，但不是详细的整体结构。尽管如此，仍有可能借助所谓的维纳界限来估计片剂的复有效介电常数。本文的想法是提出一种应用于片剂纯成分介电常数实部和虚部估计的维纳界限的改进方法。作为一个例子，考虑了醋酸淀粉片剂的有效复介电常数。
