Distribution of ethenzamide and other ingredients on granule surfaces studied by Raman microspectroscopy and mapping.

Distributions of API and medical additives in granules were analyzed using Raman microspectroscopy and mapping. In order to clearly detect ingredients present at low levels, the characteristic peak for each ingredient was used for identification. Two granulation processes, tumbling granulation and high-shear granulation were selected to examine the feasibility of Raman microspectroscopy for investigating granules. Ethenzamide, lactose monohydrate, cornstarch and methylcellulose were used to make model granules. Methylcellulose was distributed homogeneously from the early stage in both granulation methods. Cornstarch and lactose showed similar distribution properties in high-shear granulation. It was presumed from this observation that similar chemical structures with high-hydrophilic groups in the two compounds determined their similar distribution properties. These results suggest that Raman microspectroscopy using the unique absorption peak of each ingredient can detect each ingredient in the individual pixel size (2 × 2 μm). This analytical method can contribute to evaluation of granular conditions and granulation processes.