Deep eutectic solvents in separations: Methods of preparation, polarity, and applications in extractions and capillary electrochromatography

•Preparation methods, polarity, and the use of deep eutectic solvents (DES) in extractions is reviewed.•Seven different DES preparation methods are systematically discussed.•Betaine dye, kamlet-taft parameters, and nile red methods have been used to provide polarity scales for DES.•DESs in the extraction of various compounds is reviewed.•As additives in capillary electrochromatography, DESs improve separation characteristics.