SILICA-BASED MONOLITHIC CAPILLARY COLUMNS MODIFIED TO ZWITTERIONIC STATIONARY PHASE FOR HYDROPHILIC INTERACTION LIQUID CHROMATOGRAPHY

Zwitterionic monolithic capillary columns intended for isocratic gradient hydrophilic interaction chromatography (HILIC) separations are introduced. Silica-based capillary columns (150 mm x 0.1 mm) were prepared by acidic hydrolysis of tetramethoxysilane in the presence of polyethylene glycol and urea. The modification by a 3-(trimethoxysilyl)propyl methacrylate and then by a zwitterionic [2-(methacryloyloxy)ethyl]-dimethyl-(3-sulfopropyl)-ammonium hydroxide to HILIC stationary phase bearing sulfoalkylbetaine groups on its surface followed. Prepared columns were characterized in HILIC separation mode employing mobile phase containing 10% (v/v) of 5 mM ammonium acetate pH = 4.5 in acetonitrile. Comparison with the commercially available ZIC-HILIC (R) column (Merck SeQuant (R)) under the same separation conditions using a mixture of aromatic carboxylic acids as a sample was done on the basis of separation efficiency of tested columns as well as retention factors and peak asymmetry of individual solutes.