Structured parallel diffusion model for intraparticle mass transport of proteins to porous adsorbent

A structured parallel diffusion model (SParD model) has been developed to describe the intraparticle mass transport of proteins in porous chromatographic matrices. This model takes into account surface diffusion, hindered pore diffusion, pore size distribution of porous supports, and the shrinking of effective pore radius by protein adsorption. Moreover, the Maxwell–Stefan approach was adopted to express the surface diffusion. The uptake kinetics of proteins, bovine serum albumin and γ-globulin, to anion exchanger, DEAE Spherodex M, is studied by batch adsorption. The dynamic adsorption data thus obtained are analyzed by the SParD model. The surface diffusivities of the two proteins are acquired by matching the model with experimental data. The hindrance effect on pore diffusion in different-sized pores was illuminated by the calculated intraparticle concentration profiles of adsorbed protein and the ratios of surface diffusion to pore diffusion rates in different pores. Thus, the validity and usefulness of the SParD model have been confirmed.