(668a) X-Ray Microtomography and Image Analysis as Complementary Methods for Morphological Characterization and Coating Thickness Measurement of Coated Particles

Because of the functionality of controlled release tablet coatings, it is desirable to have a rapid means of optimizing coating conditions and predicting the performance of a batch, prior to exhaustive lab analysis. This work reviews X-Ray Microtomography as a powerful non-destructive technique for the microstructural characterization of coated particles and to reveal internal details and characteristics of the coating shell in both 2D and 3D. In addition, X-Ray Microtomography was shown to be a helpful tool to visualize and unambiguously identify and quantify eventual cracks and damages three-dimensionally inside or on the surface of particles. This is hardly possible by other methods. Furthermore, parameters such as density, porosity, adhesion at the interfaces and coating thickness can be easily calculated. In particular, X-Ray Microtomography was found to be an adequate tool for the quantification of the coating thickness and coating quality of coated spherical particles. Together with an average thickness value for each particle in the batch and an average value for the whole batch population, X-Ray Microtomography protocol could generate coating thickness distribution intra-particle and inter-particle, which brought precious information such as coating thickness uniformity and homogeneity and zero-coating spots. The feasibility of the technique and the goodness of the developed protocol to quantify coating thickness and coating quality were demonstrated. The results indicate that by using X-Ray Microtomography and computational image analysis the quantification of the labelled polymer characteristics of the coating structure was extremely good. The robustness, the potential, and limitations of the X-Ray Tomography are discussed based on experimental work. For that purpose the tablet cores, Sodium Benzoate, Purox®, and Microcrystalline Cellulose, MCC, were both film coated with two aqueous solutions of hydroxypropyl methylcellulose, HPMC and one Poly Vinyl Alcohol, PVA and the film coating was performed using an Prototype pilot-scale top-spray fluidized bed coater.