Preparation of poly(N-isopropylacrylamide)-grafted polymer monolith for hydrophobic interaction chromatography of proteins

Poly(N-isopropylacrylamide)-grafted polymer monolith has been achieved using a surface-initiated atom transfer radical polymerization grafting polymerization within the pores of poly(chloromethylstyrene-divinylbenzene) macroporous monolith contained in a 100 mm × 4.6 mm I.D. stainless steel column. The grafted-poly(N-isopropylacrylamide) on the surface of the grafted monolith that was used as chromatographic stationary phase showed a response to the variation of temperatures and/or salt concentrations. This study focus on its salt concentration responsive property and it has been revealed that the hydrophobicity of the grafted monolith can be adjusted by changing salt concentrations in the range of 0.05–2.0 mol/L. A variety of salts including sodium sulfate, ammonium sulfate and sodium chloride exhibited different effects on the alteration of hydrophobicity of the grafted monolith, and the effect of the salts was in the order of sodium sulfate > ammonium sulfate > sodium chloride. Based on this response to salt concentrations, the grafted monolith was applied in hydrophobic interaction chromatography of proteins, and the base-line separation of a six proteins mixture consisting of cytochrome c, myoglobin, ribonuclease A, bovine serum albumin, ovalbumin and thyroglobulin bovine was achieved by a salt gradient elution.