[Preparation and characterization of a novel hydrophilic stationary phase and its application in pressurized...

Silica particles having different sizes were synthesized by a modified Stöber method. The reaction temperature, stirring rate, and time conditions were optimized. Finally, 580 nm monodispersed silica particles were synthesized. Moreover, a novel zwitterionic stationary phase with strong hydrophilicity was prepared based on a "thiolene" click reaction between cysteine and the silica particles modified vinyl group (Cys-vinyltrichlorosilane (VTMS)-SiO₂). A column packed with submicron cysteine-bonded silica was prepared by the slurry packing method. The hydrophilic mechanism was revealed by the separation of toluene, acrylamide, and thiourea using different ratios of acetonitrile. The effects of applied voltage, buffer concentration, and buffer pH on the separation ability of the capillary column packed with 580 nm Cys-VTMS-SiO₂ were examined to achieve optimal results. In addition, the run-to-run and day-to-day reproducibilities in terms of retention time and peak area for the above mentioned compounds were both 2.0%. The good batch-to-batch reproducibility indicated that the preparation method was suitable for the fabricated column. The column used in the pressurized capillary electrochromatography (pCEC) system demonstrated efficient and fast separation of a mixture consisting of nucleosides, phenols, amines, and peptides after the optimization of the separation condition. The proposed method shows good potential for the separation of polar and hydrophilic compounds.