Advances in the application of deep eutectic solvents based aqueous biphasic systems: An up-to-date review

The success of separation and isolation of biomolecules and bioactive compounds from natural matrix depends greatly upon the choice of applied method. The sustainable and biocompatible nature of aqueous biphasic systems (ABS) has attracted much attention from the scientific community. The earliest ABS composed of polymer and inorganic salts have limited application due to ecological issue, small polarity difference between coexisting phases and viscosity. Ionic liquids (ILs) and deep eutectic solvents (DES) are newer superior solvents applied as one of the phase forming compounds in ABS. IL-ABS have been successfully demonstrated for separation and purification of numerous compounds. Recently, DES have been introduced in ABS owing to lower cost of starting material, ease of preparation, higher tunability and biodegradability. The appropriate choice of hydrogen bond acceptor (HBA) and hydrogen bond donor (HBD) in preparation of DES can easily modify the polarity of phases and facilitates ABS formation. This review discusses the application of DES-ABS in separation and purification of proteins, enzymes, amino acids, nucleic acids, polysaccharides, phytochemicals, dyes and pharmaceuticals. The factors affecting the extraction efficiency of DES-ABS for proteins are highlighted. The limitations and future prospects for application of DES-ABS in the separation technology are also discussed.