A study of a visual inspection technique for in-process monitoring of coating of pharmaceutical pellets

A systemic approach to development of process analytical technology (PAT) tools for monitoring the critical quality and performance attributes of the manufacturing process is of great importance in ensuring final product quality in the pharmaceutical industry. The aim of this study was to examine the possibilities for a visual inspection technique as a PAT tool for in-process and on-line monitoring of the coating process of pharmaceutical pellets. The in-process conditions of the Wurster coating system were studied and an experimental visual imaging system that mimics these conditions was set up. Image analysis methods were developed that allow the determination of pellets' coating thickness estimation from the images acquired during the coating process. The results of the proposed visual imaging method were evaluated through comparison with a reference method and a good agreement of the coating thickness estimations by the two methods was found.