Preparation of zwitterionic polymeric monolithic columns for hydrophilic interaction capillary liquid chromatography

Porous zwitterionic monolithic columns based on photo-initiated copolymerization of N,N-dimethyl-N-methacryloxyethyl-N-(3-sulfopropyl)ammonium betaine and poly(ethylene glycol) diacrylate in a binary porogen system comprising isopropanol and decanol were prepared in 75-μm-id fused silica capillaries. The resulting monolith was evaluated by hydrophilic interaction chromatography. Inverse size-exclusion chromatography was used to characterize the pore structure of the resulting monolith. A typical hydrophilic interaction chromatography mechanism was observed when the organic content in the mobile phase was higher than 60%. Good separations of amides, phenols, and benzoic acids were achieved. An efficiency of 75,000 plates/m was obtained. The effects of mobile phase pH, salt concentration, and organic modifier content on retention were investigated. For polar-charged analytes, both hydrophilic interactions and electrostatic interactions contributed to the selectivity.