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1-vinyl-3-octylimidazolium (ViOcIm+) based ionic liquids (ILs) monolithic capillary columns with different counter ions (bromide,Br-; tetrafluoroborate,BF4-; hexafluorophosphate,PF6-; and bis-trifluoromethanesulfonylimide,NTf2-) were prepared by thermal free radical copolymerization.These synthesized ILs-monolithic columns were systematically characterized,which exhibited homogeneous monolithic matrix,satisfying permeability and good mechanical stability and clearly confirmed a change in pore size varied from 15.53 to 31.08 nm with the size of anions increasing.Under capillary electrochromatography (CEC) mode,stable reversed electroosmotic flow (EOF) was obtained over a wide pH range from 2.0 to 12.0 on these resulting ILs-monolithic columns and decreased in the order of ViOcIm+Br- < ViOcIm+BF4- < VOIm+PF6- < ViOcIm+NTf2- based column at the same test pH.The results showed that the highest separation efficiency of thiourea and its analogues was obtained on ViOcIm+Br- based column,which corresponded to the greatest column efficiency (theoretical plates,N) of 151000 plates m-1 for thiourea.Four aromatic hydrocarbons were well separated on each monolithic column using 40% v/v ACN,30 mM acetic acid of pH 3.0 as the mobile phase with the eluting sequence of thiourea < toluene < ethylbenzene < propylbenzene < butylbenzene.Moreover,baseline separation of four proteins was obtained on ViOcIm+NTf2- based column with acetonitrile/acetic acid (20%,v/v) as mobile phase.The experimental results indicated that anions significantly influenced ILs based polymers,which gave these columns potential to separate both small molecules and macro biomolecules.In summary,the adjustable property of ILs extended the range of options for the stationary phases in CEC to a great extent.