Analysis of film coating thickness and surface area of pharmaceutical pellets using fluorescence microscopy and image analysis

A method is presented which enables geometrical characterisation of pharmac eutical pellets and their film coating. It provides a high level of details on the single pellet level. Image analysis was used to determine the coati ng thickness (h) applied on the pellets and the surface area (A) of the pel let cores. Different definitions of A and h are evaluated. Hierarchical ana lysis of variance was used to resolve different sources contributing to the total variance. The Variance within pellets and the variance between pelle ts were found as significant sources of variation. Special emphasis was put on evaluation of A/h due to its influence on the release rate of an active drug substance from the pellet core. The pellet images were thus used to p redict variations in the release rate using a mathematical model as a link between the image data and the release rate. General aspects of image analy sis are discussed. The method would be useful in calibration of near infrar ed spectra to h in process analytical chemistry. (C) 2000 Elsevier Science B.V. All rights reserved.