2009

Kurki, Lauri; Marbach, Ralf

As a part of the PAT-KIVA project, this report summarizes the results of the work packages (WP's) 1.1 and 1.4. The WP1.4 consisted of laboratory studies to measure the absorption and scattering properties of several pharmaceutical powders. It also included the designing and building of the spectrometer accessories to make the measurements possible. The WP1.4 was needed to support of the WP1.1, where a wireless online probe of powder blend homogeneity was to be built. The idea was to be able to separate the chemical concentrations from the physical determinants of the powder blends by spatially resolved diffuse reflectance spectroscopy (SDR). The chemical concentrations were assumed, according to previous studies by others, to be faithfully represented in the calculated absorption coefficient. On the other hand, the physical properties like particle size distribution were assumed to be separated into the scattering coefficient and anisotropy factor. However, the studies indicated, that with the growth of particle size, these assumptions do not hold to any reasonable degree. Therefore it was decided not to design the online probe, but a laboratory research probe employing the SDR principle and being as versatile as possible regarding the wavelength range and illumination features. The design of the laboratory probe was nearly completed, but due to various reasons, it could not be built within the PAT-KIVA project. The main results of the WP1.4 were the building of spectrometer accessories and the measured optical properties of various powders. The main results of the WP1.1 were the preliminary comparison of SDR measurements to the "reference" measurements done in WP1.4, and the near completion of the very challenging design task of the laboratory SDR probe. Another main result connected with both work packages was the development of simulation software to solve the inverse problem of calculating samples' optical properties from spectroscopic measurements.