Design and evaluation of C18 stationary phases with different polar-embedded groups for liquid chromatography

New stationary phases including polar embedded stationary phases that are capable of utilising green mobile phases have recently emerged. This study presents two straightforward strategies for preparing C18 phases with distinct polar-embedded groups: thioether (C18T) and quaternary ammonium (C18Q). The two strategies were assessed based on convenience, cost, yield, and time efficiency. After successful characterization, the phases and commercial C18 phases were thoroughly evaluated using various standard substances and testing protocols. Both C18T and C18Q exhibited excellent wettability in highly aqueous mobile phases and good shape selectivity. C18T which has a low bonding density, demonstrated an impressive level of selectivity in the separation of basic compounds compared to other phases. In comparison, C18Q exhibited enhanced performance in separating acidic compounds, benefiting from the embedded quaternary ammonium groups. The present study proposes a novel approach for constructing polar embedded alkyl stationary phases, which represents a necessary supplement to the existing C18 materials.