Quantitative Determination of the Scattering and Absorption Coefficients from Diffuse Reflectance and Transmittance Measurements: Application to Pharmaceutical Powders
| Autor: | Jochen Fricke, T. Burger, J. Kuhn, R. Caps |
|---|---|
| Rok vydání: | 1997 |
| Předmět: |
Diffuse reflectance infrared fourier transform
Chemistry Scattering Forward scatter 010401 analytical chemistry Analytical chemistry 01 natural sciences 0104 chemical sciences Computational physics 010309 optics Attenuation coefficient 0103 physical sciences Radiative transfer Transmittance Diffuse reflection Absorption (electromagnetic radiation) Instrumentation Spectroscopy |
| Zdroj: | Applied Spectroscopy. 51:309-317 |
| ISSN: | 1943-3530 0003-7028 |
| DOI: | 10.1366/0003702971940404 |
| Popis: | A measurement and data evaluation technique for the separate determination of the scattering and absorption properties of loose pharmaceutical powders is described. The equation of radiative transfer for diffuse reflectance and transmittance is analytically solved by using a three-flux approximation. Combined transmittance and reflectance measurements then allow one to derive both the scattering and the absorption coefficients. The scattering and absorption coefficients provide more information about particle size, degree of agglomeration, and chemical composition of the samples in comparison to the usual determination of only the ratio of the coefficients from diffuse reflectance measurements on optically thick samples. Furthermore, the theory of diffuse reflectance of optically thick samples according to Kubelka and Munk is compared to the three-flux approximation. The influence of the particle size on the scattering and absorption coefficient is investigated, and it is shown that the assumption of a wavelength-independent scattering coefficient, though often made in reflectance spectroscopy, is not generally valid. |
| Databáze: | OpenAIRE |
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