Yoshikazu Matsushima

Temperature-responsive chromatography using poly(N-isopropylacrylamide)-modified silica

A new concept in chromatography is proposed that utilizes a temperature-responsive surface with a constant aqueous mobile phase. The surface of the silica stationary phase in high-performance liquid chromatography (HPLC) has been modified with temperature-responsive polymers to exhibit temperature-controlled hydrophilic/hydrophobic changes. Poly(N-isopropylacrylamide) (PIPAAm) was grafted onto (aminopropyl)silica using an activated ester-amine coupling method. These grafted silica surfaces show hydrophilic properties at lower temperatures which, as temperature increases, transform to hydrophobic surface properties. The elution profile of five mixed steroids on an HPLC column packed with this material depends largely on the temperature of the aqueous mobile phase. Retention times increase with increasing temperature without any change in the eluent. Changes in the retention times of hydrophobic steroids were larger than those for hydrophilic steroids. The temperature-responsive interaction between PIPAAm-modified silica and these steroids is proposed to result from changes in the surface properties of the HPLC stationary phase by the transition of hydrophilic/hydrophobic surface-grafted IPAAm polymers. We demonstrate a novel and useful new chromatography system in which surface properties and the resulting function of the HPLC stationary phase are controlled by external temperature changes. This method should be effective in biological and biomedical separations of peptides and proteins using only aqueous mobile phases.

Analysis of peptides and proteins by temperature-responsive chromatographic system using N-isopropylacrylamide polymer-modified columns

A new method of HPLC using packing materials modified with a temperature responsive polymer, poly(N-isopropylacrylamide) (PIPAAm), was developed. Homogeneous PIPAAm polymer and its copolymer with butyl methacrylate (BMA) were synthesized and grafted to aminopropyl silica by activated ester-amine coupling and they were used as packing materials. The surface properties and functions of the stationary phases are controlled by external temperature. Isocratic elution by aqueous mobile phase alone is the basis for separation of peptides and protein. The separation of the mixture of three peptides, insulin chain A and B and beta-endorphin fragment 1-27 was achieved by changing the column temperature with 0.9% NaCl aqueous solution as the sole eluent. Retention of peptides and proteins was controlled both by column temperature and by NaCl concentration in the aqueous mobile phases in this chromatographic system.

TEMPERATURE-RESPONSIVE CHROMATOGRAPHY

Abstract We have developed a new method for HPLC which uses packing materials modified with a temperature-responsive polymer, poly( N -isopropylacrylamide). The surface properties and functions of the stationary phases are controlled by the external temperature. In the proposed chromatographic system, the elution of target substances is controlled by only a small change in the column temperatures.