Ionic liquids: solvents and sorbents in sample preparation

The applications of ionic liquids (ILs) and IL-derived sorbents are rapidly expanding. By careful selection of the cation and anion components, the physicochemical properties of ILs can be altered to meet the requirements of specific applications. Reports of IL solvents possessing high selectivity for specific analytes are numerous and continue to motivate the development of new IL-based sample preparation methods that are faster, more selective, and environmentally benign compared to conventional organic solvents. The advantages of ILs have also been exploited in solid/polymer formats in which ordinarily nonspecific sorbents are functionalized with IL moieties in order to impart selectivity for an analyte or analyte class. Furthermore, new ILs that incorporate a paramagnetic component into the IL structure, known as magnetic ionic liquids (MILs), have emerged as useful solvents for bioanalytical applications. In this rapidly changing field, this Review focuses on the applications of ILs and IL-based sorbents in sample preparation with a special emphasis on liquid phase extraction techniques using ILs and MILs, IL-based solid-phase extraction, ILs in mass spectrometry, and biological applications.