Synthesis of sulfo/vinyl biphasic silica hybrid monolithic capillary column and its application to on-column preconcentration for capillary electrochromatography

A novel method to synthesize sulfo/vinyl biphasic silica hybrid monolithic column in one step was developed for on-column preconcentration. In this method, sulfo-based segment is located at the inlet of capillary column, which acts as preconcentration column. It is synthesized by polymerization of 3-sulfopropyl methacrylate potassium salt (SPMA) and vinyltrimethoxysilane (VTMS) with tetramethoxysilane (TOMS). Close to the preconcentration column, a vinyl functionalized segment is formed and serves as separation column. It is synthesized by polymerization of only VTMS with TOMS. Vinyl groups on vinyl functionalized segment are modified with ligand containing sulfhydryl group, such as octadecanethiol (C18-SH for short), 6-mercapto-1-hexanol (HO-C6-SH for short), via thiol-ene click reaction. The interface between the two segments is seamless and without any dead volume. The applicability of this system is demonstrated by successful separation of closely related amines including p-phenylenediamine, aniline, p-toluidine, N-methyl aniline, N,N′-dimethylaniline, and diphenylamine. Good separation and enrichment are obtained. The proposed system is also successfully applied to complex biological samples, such as peptide, diluted BSA hydrolysate, and the results indicate that the system has a capability for preconcentration of low abundance peptides.