Chemical Distribution Uniformity Assessment of "Intra-Tablet" by Hyperspectral Raman Imaging Analysis

This study aimed to develop a new index, Distribution Uniformity Index (DUI), to assess the "intra-tablet" homogeneity.

High-resolution hyperspectral Raman imaging was adopted to scan a tablet to get the components' distribution. The heuristic algorithm was applied to generate a Raman heatmap with RGB colors quantitatively correlated with the concentrations of each component. DUI is defined as the ratio of the area under the uniformity curve of the sample image to that of the randomized image. The accuracy and applicability of DUI were verified by constructing model images with controlled uniformity and random regions. The effects of "intra-tablet" homogeneity on the disintegration and dissolution of spironolactone tablets were investigated.

DUI value was directly obtained from heuristic visual analysis of macro-pixel from hyperspectral Raman images. A good linear relationship and good repeatability were confirmed between DUI and the uniformity of model images. The size of CaSO₄·2H₂O affected the "intra-tablet" homogeneity of spironolactone tablets, which was detected by the DUI value. The better "intra-tablet" homogeneity led to a higher disintegration and dissolution of spironolactone tablets.

DUI represents a novel index to evaluate the "intra-tablet" homogeneity and is beneficial for formulation research and development.