Facile Preparation of Zwitterionic Organic-Silica Hybrid Monolithic Capillary Column with an Improved "One-Pot" Approach for Hydrophilic-Interaction Liquid Chromatography (HILIC)

A simple single-step thermal-treatment "one-pot" approach for the preparation of organic-silica hybrid capillary monolithic columns is described. In this improved method, the cross-linker vinyltrimethoxysilane (VTMS) was replaced by 3-methacryloxypropyltrimethoxysilane (gamma-MAPS), which is more active in polymerization reactions, and only one thermal treatment step was required in the preparation of hybrid monoliths. Two zwitterionic organic-silica monolithic columns were successfully synthesized by using [2-(methacryloyloxy)-ethyl]dimethyl-(3-sulfopropyl)ammonium hydroxide (MSA) and 2-methacryloyloxyethyl phosphorylcholine (MPC) as the organic monomers. The effects of the tetramethoxysilane (TMOS)/gamma-MAPS molar ratio, content of monomer, composition of porogenic solvent, and reaction temperature on the morphologies of the hybrid monoliths were investigated. The MSA-silica and MPC-silica hybrid monolithic columns exhibited good permeability and good mechanical stability. The monolithic columns were used for the separation of polar compounds by capillary hydrophilic-interaction chromatography (cHILIC). A typical HILIC retention mechanism was observed at higher organic solvent contents (>50% ACN). The MSA monoliths were further investigated in the separation of various neutral, basic, and acidic analytes, as well as small peptides, by capillary liquid chromatography (cLC), and high efficiency and satisfactory reproducibility were achieved. In addition, the analysis of a tryptic digest of bovine serum albumin (BSA) by cLC tandem mass spectrometry (cLC-MS/MS) with an MSA monolith further demonstrated its potential in the separation of biological samples.