Polymer-grafted ion exchange adsorbents were of great interest for the development of high-performance protein chromatography in biopharmaceutical and related fields. In this work

protein retention was systematically investigated in ion exchange chromatography packed respectively with dextran-grafted cation exchange adsorbents containing sulphopropyl (SP) ligand

SP Sepharose XL and Capto S

and non-grafted cation exchange adsorbent

SP Sepharose FF

using five proteins. With an increase of buffer pHs

retention factors of proteins decreased among all the adsorbents

demonstrating the dominant role of electrostatic interaction for protein binding on cation exchange adsorbents. The evidences further revealed that the scattered positive charges on the surface of protein molecules

rather than net charge of protein molecule

determined protein retention on cation exchange adsorbent. Likely

counterions including NH

4

+

K

+

Na

+

and Mg

2+

exhibited distinct influence on protein retention. It was well ascribed to solvent-mediated indirect ion-macromolecule interactions and direct ion-macromolecule interactions. Compared w

ith SP Sepharose FF

polymer structure in dextran-grafted cation exchange adsorbents ultimately brought about different ligand distributions and smaller pore sizes

thereby regulating protein retention in cation exchange chromatography. By comparing the retention of myoglobin and β-lactoglobulinB in SP Sepharose XL and Capto S

we reasonably speculated that the enhancement of nonelectrostatic interaction caused by reducing the space arm length was a major reason for an increasing retention factor of myoglobin in Capto S. The results in this research help us understand adsorption mechanism of protein in polymer-grafted adsorbents and give scientific guidance for the development of chromatographic materials.