Versatile ene-thiol photoclick reaction for preparation of multimodal monolithic silica capillary columns

This paper presents a photografting process of monolithic silica capillary columns based on the ene-thiol click chemistry. This study is performed on a "generic" vinyl-functionalized silica monolith (Hmin 6±1μm). The photoclick reaction is investigated using different thiol monomers (octadecanethiol, cysteine and sodium mercaptoethanesulfonate) to prepare capillary columns dedicated to various chromatographic modes (reversed-phase, HILIC and strong cation exchange). Whatever the monomer used, the photografting reaction is achieved in less than 5min with a relatively high thiol monomer content. This allows preparing highly retentive and efficient monolithic columns while avoiding polymerization and/or column clogging. In addition to the aforementioned properties (duration, versatility, efficiency), this photo-triggered chemical reaction allows addressing several appropriate surface functionalizations inside a single monolithic column in order to prepare nanovolume multimodal capillary columns. A multimodal biphasic monolithic column with a 1cm length cation-exchange segment followed by a 9cm length reversed-phase segment (SCX-RP) is prepared through two successive photografting reactions using a UV-mask to localize the reactions. This multimodal biphasic column is investigated using a model sample for the selective fractionation and separation of cationic and neutral compounds and is applied to the on-line preconcentration and separation of β-blockers.