Rapid fabrication of ionic liquid-functionalized monolithic column via in-situ urea-formaldehyde polycondensation for pressurized capillary electrochromatography

A novel strategy for rapidly fabricating ionic liquid (IL)-bonded multifunctional monolithic stationary phase has been developed by an in-situ polycondensation of urea-formaldehyde (UF) and a lab-made acylamino-functionalized IL (1-acetylamino-propyl-3-methylimidazolium bromide, [AAPMIm]Br). Two polycondensation processes of UF with 1-amino-propyl-3-methylimidazolium bromide or [AAPMIm]Br were evaluated. Several parameters including mass ratio of urea-formaldehyde, amount of [AAPMIm]Br, polycondensation time and reaction temperature were optimized, and the [AAPMIm]Br-bonded monolithic stationary phase could be rapidly synthesized in 10 min with a satisfactory permeability and mechanical stability. Used for pressurized capillary electrochromatography (pCEC), a typical hydrophilic interaction (HI) retention could be obtained in the resultant [AAPMIm]Br-bonded monolith when the content of acetonitrile (ACN) in mobile phase exceeded 20%. Multiple retention mechanisms such as hydrophilic interaction (HI), hydrogen bond (HH), anion-exchange and cation-exclude interactions, were acheived in the [AAPMIm]Br-bonded monolith. Various polar compounds including phenols, benzoic acid and its homologues, and enkephalins have been well separated and thus demonstrated a satisfactory separation performance of the obtained monolith. A facile access is lighted for rapid preparation of ionic liquid-bonded monoliths with multiple retention mechanisms for pCEC.