ABSTRACT
This chapter presents work showing how ensemble release profiles are influenced by particular parameter distributions, which parameters are involved and which model release equations result. In working with an assembly of microcapsules, nanoparticles, liposomes, emulsion droplets, or any multiparticulate system, it is often supposed that the population as a whole will follow the same behavioral pattern as the single units of which it is constituted, for example, the batch and the individuals will exhibit identical kinetics in drug release, uptake of substances or chemical reaction. Since batch standardization is based on overall and mean properties, differences in parameter heterogeneity between batches have been overlooked, and little is known of their dependence on manufacturing processes. Mass transport heterogeneity has been detected semiquantitatively by counting the number of methyl-orange microcapsules changing color at fixed times on penetration of acid from the exterior.
