Preparation And Evaluation Of A Strong Cation-exchange Polymer Silica-microspheres-encapsulated Monolithic Column

Monoliths are commonly classified into three types: organic polymer, inorganic silicaand organic-inorganic hybrid monolithic columns. Organic polymer monolithic columnssuffer from the limitations of poor mechanical stability, easy swelling/shrinking, uneven poresize and unsuitability for the separation of small molecular analytes. On the contrary,inorganic silica monolithic columns not only circumvent the above drawbacks, but alsoexhibit a good chromatographic performance attributed to the unique bimodal pore(throughpore and mesopore) structures. However, the procedures for preparation of inorganicsilica monolithic columns are generally complex, time-consuming, and prone to cracks of thecontinuous bed. As a novel type of organic-inorganic hybrids,silica-microspheres-encapsulated monolithic columns have received more and more attentionowing to the integration of the advantages from organic and inorganic monoliths with thepreparation procedure simplified in recent years.In the present study, a strong cation-exchange polymer silica-microspheres-encapsulatedmonolithic column was prepared by in-situ polymerization of3-sulfopropyl methacrylatepotassium salt and ethylene dimethacrylate in the presence of ternary porogens consisting ofn-propanol,1,4-butanediol and water in a250μm i.d. fused silica capillary prepacked withsilica-microspheres. The total concentration of the monomers, temperature and time of thepolymerization were investigated, and the optimal conditions for preparation of the columnwere established. The optimized concentration, temperature and time are T=30%(C=50%),60℃and3h, respectively. The prepared column was evaluated in terms of micro-porestructure, permeability, endurance of pressure, ability of anti-swelling and column efficiency.The separation performance of the prepared column was evaluated through the separation of agroup mixture of common cations. Finally, the monolithic column was applied to enrich theclenbuterol in urine. After several parameters including composition of desorption solution,adsorption capacity of extraction column, sample flow rate and pH value of the sample matrixwere optimized, an about500times high enhancement factor was obtained.