Magnetic ionic liquids in analytical sample preparation: A literature review

Magnetic ionic liquids (MILs) strongly respond to external magnetic fields in addition to having unique and tunable physiochemical properties of ionic liquids. Unlike ferrofluids, MILs are clean and particle-free magnetic liquids. The careful tailoring of MIL components allows their application as extraction solvents both in hydrophilic and hydrophobic media. The extraction process can be expedited due to magnetically enhanced phase separation of analyte-enriched MILs by eliminating the time-consuming steps of centrifugation and filtration. They have been used in many extraction techniques including dispersive liquid-liquid microextraction, single drop microextraction, stirring-assisted drop-breakup microextraction, stir bar dispersive liquid microextraction, aqueous two-phase system. The efforts have also been made to design instrument compatible MILs thus eliminating the need to extract dilution or reconstitution before introduction to the analytical instrument. This review aims to share with the analytical community the literature update, accomplishments, and limitations of the MIL based extraction techniques.