Investigation into the impact of sub-populations of agglomerates on the particle size distribution and flow properties of conventional microcrystalline cellulose grades

Microcrystalline cellulose (MCC) is regarded as one of the most versatile tablet filler binders, finding a wide use in both granulation and direct compression operations. It has been shown that MCC particle populations consist of a mixture of 'rod like' primary particles, and agglomerates, and that the proportion of these primary particles and agglomerates differs within the different grades of materials, contributing to the different bulk properties of these materials. However, the proportion of primary particles and agglomerates has not previously been fully elucidated, and their contribution to the performance factors such as flow explained. In this paper we use a novel microscopy-based characterization technique to demonstrate that the proportion of 'agglomerates' in the series of MCC grades between PH101 and PH200 is, by number, very low, but sufficient to perturb a volume-based particle size method by significant amounts.