A Strong Cation-Exchange Monolithic Column For Capillary Liquid Chromatography

The use of polymeric materials in ion-exchange chromatography is attractive because of their typically high mechanical stability and tolerance of a wide range of pH values. Polymeric monoliths with ion-exchange functionality are usually obtained either by direct co-polymerization of the monomers containing ion-exchange functionality or through different post-modifications of monolith surface. The second method not only suffers from time-consuming, poor preparation reproducibility, low ion-exchange capacity, but also the post-modification steps lead to adverse effects to the column life.A strong cation-exchange monolithic column was prepared by in-situ polymerization of 3-sulfopropyl methacrylate potassium salt and ethylene dimethacrylate in the presence of ternary porogens consisting of propan-1-ol, butane-1.4-diol and water. The separation performance of the prepared column was evaluated through the separation of a model mixture of common cations, and it was demonstrated that the ion-exchange monolith obtained by direct synthesis possesses higher separation efficiency than the one prepared through post-modification. The effects of the pH value and composition of mobile phase on the retention behaviors were examined, and it was confirmed that the retention of anilines on the column is attributed to the co-action of ion-exchange and hydrophobic interaction. Also the retention mechnism of proteins and amino acids on the monolithic column were investigated. Finally the strong cation-exchange monolithic column was used to the rapid determination of cations in seawater samples andρ-phenylene diamine in hair dye samples. The quantitative method was evaluated in terms of linear range, precision, detection limit and recovery.