Previously, we have studied the adsorption of bovine serum albumin (BSA) and γ-globulin on poly(ethylenimine) (PEI)-grafted Sepharose FF resins and found that there existed a critical ionic capacity (cIC, 600 mmol/L for BSA and 460 mmol/L for γ-globulin), above which the uptake rate increased drastically due to an enhanced "chain delivery" effect.Subsequent studies showed that a moderate salt concentration may promote the occurrence of the "chain delivery" due to the weakened binding and/or the increased flexibility of PEI chains, indicating that decreasing the charge density of PEI chains may be more favorable for its working as an ion exchanger.