Determination of mass transfer dissolution rate constants from critical time of dissolution of a powder sample

This article presents a method for obtaining mass transfer dissolution rate constants of polydisperse, particulate solids under given hydrodynamic conditions. Oxalic acid, salicylic acid, and phthalimide were recrystallized and classified into various mesh cuts, which were then subjected to dissolution in a USP dissolution apparatus II. Expressions were derived for the anticipated dissolution profiles, and it is shown that cube root plots should show a nick at the point were the smallest particle dissolves. Time and microscopic dimensions then allow calculation of the mass transfer dissolution rate constant.