Photopolymerization of acrylamide as a new functionalization way of silica monoliths for hydrophilic interaction chromatography and coated silica capillaries for capillary electrophoresis

• Preparation of photo functionalizable silica monolith for separation sciences.
• Rapid, versatile and localizable strategy for functionalization of silica surfaces.
• Localizable photochemical process applied for the in-line preconcentration and electrokinetic separation of enkephalins.

A simple, rapid and localizable photochemical process for the preparation of hydrophilic coated capillary and silica-based monolithic capillary columns is described. The process involves the free radical polymerization of acrylamide monomers onto acrylate pre-activated silica surface triggered by UV photoinitiation. The experimental conditions (monomer content, time of irradiation) were optimized on silica monolithic columns by monitoring the evolution of the chromatographic properties (retention, permeability, efficiency) in HILIC mode using a set of nucleosides as test solutes. Compared to thermal polymerization process, the photoinitiation allows the preparation of highly retentive and efficient HILIC monolithic columns in less than 10 min of irradiation. This process was then successfully applied to the surface coating of fused silica capillary walls. In addition to its relative high stability and ability to reduce the electroosmotic flow, this polyacrylamide coating is localizable. Benefits of this localizable photochemical process are highlighted through the conception of an in-line integrated bimodal microseparation tool combining a SPE preconcentration step on a photografted silica monolith and an electrokinetic separation step in a polyacrylamide photopolymerized capillary section. Two neuropeptides are used as model solutes to illustrate the suitability of this approach.