I am currently soaking surfaces of different sized nanopores with a drug. I want to differentiate the contribution the pore has to drug release from the uncontrolled release from surface adhesion. I am currently referring to Peppas' 1987 paper, using the "flat slab" equation. I want to determine the amount of drug that is actually trapped within the pores and whether this surface can be used for sustained release. Finally, can anyone refer me to a program or method of predicting the hydrodynamic/stokes radii of a small molecule? Vitamin E for example? Thanks!