(292a) Protein Adsorption Kinetics in Chromatographic Particles Visualized by Optical Microscopy

We have recently developed a new method to image transient patterns of protein adsorption in individual spherical chromatographic particles under strong binding conditions. The method takes advantage of the difference in refractive index between the protein-free and protein-saturated adsorbent matrix. When the particles are viewed with an ordinary microscope using white light illumination, the adsorption front appears as a bright ring that moves in time from the surface of the particle to its center. Experimental data were previously obtained for a limited number of proteins with the cation exchanger SP-Sepharose-FF. Sharp rings were observed confirming that protein mass transfer within the particles occurs via a shell-progressive diffusion mechanism. Quantitative analysis based on the shrinking core model provided an accurate and precise way of determining the intraparticle diffusivity for individual particles. In this work we extend these measurements to investigate (a) the effect of ionic strength on protein adsorption in IEX resins, (b) the adsorption of different proteins in agarose-based HIC resins, and (c) the adsorption of IgG in Protein A adsorbents.