Recent development of ionic liquid stationary phases for liquid chromatography

• The immobilized patterns of ionic liquids onto the supports are presented.
• Ionic liquid stationary phases (ILSPs) could separate various classes of compounds with multi-mechanisms.
• The methods for characterization of retention mechanism of ILSPs are described.

Based on their particular physicochemical characteristics, ionic liquids have been widely applied in many fields of analytical chemistry. Many types of ionic liquids were immobilized on a support like silica or monolith as stationary phases for liquid chromatography. Moreover, different approaches were developed to bond covalently ionic liquids onto the supporting materials. The obtained ionic liquid stationary phases show multi-mode mechanism including hydrophobic, hydrophilic, hydrogen bond, anion exchange, π–π, and dipole–dipole interactions. Therefore, they could be used in different chromatographic modes including ion-exchange, RPLC, NPLC and HILIC to separate various classes of compounds. This review mainly summarizes the immobilized patterns and types of ionic liquid stationary phases, their retention mechanisms and applications in the recent five years.