Adsorption isotherms on high-performance liquid chromatographic sorbents. II. Proteins on cation exchangers with silica support.

Adsorption isotherms of proteins were measured by frontal chromatography in a miniaturized chromatographic system with short, narrow-bore columns. The adsorbents were microparticulate, macroporous siliceous cation exchangers, used in the high-performance liquid chromatography of proteins, and the range of mobile phase compositions was similar to that used in elution chromatography for their separation. Adsorption of protein on the wetted stainless-steel parts of the system was reduced by coating the metal surface with a hydrophilic polymer layer. The adsorption isotherms of proteins were concave down and, in most cases, well represented by the Langmuir model. However, the data could also be fitted with reasonable accuracy to the isotherm equation by Jovanović. Although the siliceous cation exchangers were of different provenance, the isotherms of the proteins were similar. Isotherms measured by the shake-flask method were found to be identical with those obtained by frontal chromatography.