Fig. 2.

Relative predicted surface-area-normalized dissolution rate for a monoprotic weak acid in phosphate buffer at pH 6.5. Assumes different drug pK_a values at a high (50 mM) and low (1 mM) buffer concentration. Drug diffusivity = 7.9 × 10⁻⁶ cm²/s. Effective diffusion layer thickness = 30 μm