Influence of the crosslinker type on the chromatographic properties of hydrophilic sulfoalkylbetaine-type monolithic columns

In order to investigate the effects of the crosslinker on the separation performance of polar zwitterionic sulfoalkylbetaine-type monolithic columns, three crosslinkers, i.e. 1,4-bis(acryloyl)piperazine (PDA), ethylene dimethacrylate (EDMA) and N , N ′-methylenebisacrylamide (MBA), were copolymerized with the hydrophilic monomer N , N -dimethyl- N -acryloyloxyethyl- N -(3-sulfopropyl)ammonium betaine (SPDA). The chromatographic properties of the three hydrophilic sulfoalkylbetaine-type monolithic columns, including column efficiency, permeability, porosity and separation mechanism, were systematically compared using scanning electron microscopy or micro-HPLC. Good selectivity in micro-HPLC separations was achieved on all three monolithic columns. The results indicate that the polarity of sulfoalkylbetaine-type monolithic columns may be related to the polarity of the crosslinker, which further affects column selectivity and efficiency. A particularly high column efficiency (100,000 plates/m) was obtained on the novel poly(SPDA- co -PDA) monolithic column at a linear velocity of 1   mm/s using thiourea as test analyte. A higher resolution was also observed for nucleobases, nucleosides and hydrophilic organic acids on this novel poly(SPDA- co -PDA) monolithic column compared to the other two columns.