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Antibodies and related proteins have been the important therapeutic drugs or in vitro diagnostic agents,and the effective purification methods for antibodies have been widely studied.Protein A-based affinity chromatography has been adopted as the classical approach for the purification of antibody with high specificity and efficiency.However,Protein A-based capture is quite costly and associated with some practical restrictions.As a novel chromatographic technique,hydrophobic charge-induction chromatography (HCIC) is developing to purify antibody in more economical and practical way.The basic characteristic of HCIC resin is the pH-dependent adsorption behavior of dual-mode ligands that combine the hydrophobic and electrostatic interactions.The target protein can be adsorbed on the uncharged ligands at neutral pH by hydrophobic interactions,which can then be eluted by electrostatic repulsion between the protein and the charged ligands at acidic/basic conditions.In this work,with bovine serum immunoglobulin G (bIgG) and bovine serum albumin (BSA) as the model target and impurity,single and two-component adsorption isotherms,the adsorption kinetics and breakthrough curves of the protein mixtures were investigated using series of HCIC resins with different ligand densities and pore sizes.The influences of initial mass ratio of IgG to BSA were studied,and the competitive adsorption mechanism was discussed.The extended Langmuir-Freundlich equation and multi-component pore diffusion model was used to fit the competitive adsorption equilibrium and kinetics.The results demonstrated that bIgG could be preferentially adsorbed by HCIC resins and an overshoot phenomenon could be found during the dynamic adsorption.The more weakly bound BSA could be adsorbed ahead of more strongly bound component bIgG,which temporarily reached the adsorption capacities exceed the equilibrium value.Then BSA would be displaced by bIgG and the capacity eventually went back to the value of equilibrium adsorption.Better understanding on the competitive adsorption of target protein and some impurities in the multi-component feedstock is very essential to improve the separation selectivity and resolution of HCIC processes.