Experimental characterization of a standard, commercially available ion-exchange membrane cartridge for purification of large protein molecules was carried out. Individual membranes within the cartridge was qualitatively analyzed for possible defects in morphology and/or sorption patterns. Analysis was based on observation of membrane morphology using scanning electron micrographs (SEM) and protein binding patterns using dye-binding experiments. SEMs show polydispersity in pore size distribution that is substantiated by non-uniform protein binding patterns in equilibrium adsorption. Adsorption under dynamic conditions showed dependence of binding on order of membrane in the cartridge, face of the membrane and flow rate of the experiment. These experimental findings point toward limitations involved in using ion-exchange membranes for purification of large proteins. Furthermore, these experiments also magnify limitations in current theoretical understanding of membrane separations.