Stability of Hydrophobic Deep Eutectic Solvents against Water

Deep eutectic solvents are liquids formed by chemical reactions or strong intermolecular interactions between two or more compounds. One of their advantages is that solvent characteristics, such as acidic/basic and hydrophilic/hydrophobic properties, depend on their constituents. Hydrophobic deep eutectic solvents (HDESs), made from organic compounds that are barely soluble in water, are attracting attention as alternatives to volatile organic solvents, for example, for extracting organic compounds and metal ions from aqueous solutions. Hence, the stability of the HDESs against water is an important subject. This paper addresses the solubilities of water in HDESs and of HDESs in water and the effect of dissolved water on the physicochemical properties of HDESs.