Switchable hydrophilicity solvent for extraction of pollutants in food and environmental samples: A review

Switchable hydrophilic solvents (SHSs) have been widely used in analytical chemistry since they were reported in 2005 due to the unique switchable advantages. This kind of solvent can be easily switched between hydrophilic and hydrophobic forms with the merits of greenness, rapidness of separation and cost-effectiveness. This article presents a review of three kinds of SHSs including secondary and tertiary amines, medium-chain fatty acids and di-(2-ethylhexyl) phosphate acid. Amine-based SHSs can reversibly switch between hydrophobic and hydrophilic states by addition of CO2 or N2. Besides, the fatty acids and di-(2-ethylhexyl) phosphate acid are used as the SHSs that switch the polarity via pH changes. The application of these SHSs for the pretreatment of pollutants in food and environmental samples are reviewed. In addition, the current challenge and development of SHSs are discussed in this paper.