General solution for diffusion-controlled dissolution of spherical particles. 2. Evaluation of experimental data.

Our general particle dissolution model unified three traditional particle dissolution models and predicted that dissolution rates depend on surface curvature. Spherical benzocaine particles were prepared with a hot-melt dispersion method and physicochemically characterized. Their dissolution behavior was studied to evaluate the general dissolution model. A flow-through dissolution test system was used which employed an HPLC pump, an HPLC UV detector, a cylindrical-shaped dissolution cell, and a data collection system. Single benzocaine particle dissolution profiles were determined at ambient temperature (22-23 degrees C) in water at a constant flow rate. Dissolution rate normalized by surface area was found to be particle radius-dependent and fitted well by the general particle dissolution model with a diffusion layer thickness of 110 microm and benzocaine diffusion coefficient of 1.4 x 10(-5) cm(2)/s. Analysis of literature particle dissolution data also supported this general model. Our general model accounts for literature reports of apparent diffusion layer thicknesses being smaller for small particles compared with large particles. This study supports the applicability of the general particle dissolution model for a flow-through dissolution test system. Copyright 2002 Wiley-Liss, Inc. and the American Pharmaceutical Association J Pharm Sci 91:534-542, 2002