Liquid-phase microextraction techniques based on ionic liquids for preconcentration and determination of metals

• Ionic liquids (ILs) applied in liquid-phase microextraction (LPME) of metals.
• We review the most widely used procedure in IL-LPME for inorganic analysis.
• We discuss the possibility of speciation analysis and total metals determination.
• The review includes description of the possible future trends in the subject.

Current trends in analytical chemistry are leading to miniaturization and reduction in the cost of chemical analysis. Rapid development of traditional liquid-liquid extraction towards liquid-phase microextraction (LPME) is a direct consequence of these trends. Considerable reduction of solvents and waste has been achieved and the number of applications of LPME is rapidly growing. Different types of LPME have emerged, including single-drop microextraction, hollow-fiber LPME and dispersive liquid-liquid microextraction. However, the past decade brought considerable change to the analytical field with the application of ionic liquids (ILs). Their good thermal stability and low vapor pressure make them relatively non-hazardous for analytical applications in comparison to the solvents used traditionally. This review presents the applications of ILs in LPME of metals. It describes the most widely-used procedures and gives examples of emerging sample-preparation techniques.