Ionic liquids (ILs) have been attracted considerable research interests because of their unique physical and chemical properties.In our previous study, we prepared anion-exchange phases based on N-methylimidazolium-and imidazolium-functionalized silica for the separation of inorganic and organic anions with strong anion-exhange interaction.We also prepared two sulfonated imidazolium-modified silica as zwitterionic stationary phases for the simultaneous separation of anions and cations.Here we introduce our recent work on silica-confined ionic liquid (SCIL) stationary phases for high-performance liquid chromatography (HPLC).A polymerizable long-chain IL monomer named 1-vinyl-3-octadecylimidazolium bromide, [C18VIm]Br, was prepared and then polymerized on 3-mercaptopropyl silica through surface radical chain-transfer reaction.The counteranions could be changed easily by ionic self-assembly.The resultant silica showed that the selectivity for constrained isomers of polycyclic aromatic hydrocarbons (PAHs) could be drastically enhanced via the facile modification of counter anions of the SCIL stationary phases.