Neutral polar methacrylate‐based monoliths for normal phase nano‐LC and CEC of polar species including N‐glycans

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Abstract
Neutral diol methacrylate‐based monoliths were developed for normal phase chromatography (NPC) and NP‐CEC of polar compounds including N‐glycans. Four different diol methacrylate‐based monoliths were synthesized via the copolymerization of a functional monomer using either glyceryl monomethacrylate (GMM) or glycidyl methacrylate (GMA) and a crosslinker either ethylene dimethacrylate (EDMA) or trimethylolpropane trimethacrylate (TRIM). While the GMM‐based monoliths yield in one reaction step polar diol methacrylate monoliths that are ready for use in NPC or NP‐CEC, the GMA‐based monoliths required a postmodification with hot sulfuric acid to convert the epoxy functions into diols before use in NPC or NP‐CEC. All the four monoliths are neutral and void of fixed charges on their surfaces but yet exhibited relatively strong EOF in NP‐CEC. The EOF is attributed to the adsorption of ions from the mobile phase thus forming the electric double layer necessary for producing a bulk mobile phase flow. Under the same in situ copolymerization conditions of GMM or GMA with either EDMA or TRIM, the GMM–EDMA monolith was the best choice in terms of retention, separation efficiency, EOF velocity in CEC and linear flow velocity in Nano‐LC.