Sugars as hydrogen-bond donors tune the phase behavior in a novel liquid–liquid biphasic system formed by hydrophilic deep eutectic solvents and n-propanol

In this work, a novel liquid–liquid biphasic system of sugar-based deep eutectic solvents (DESs) was studied. The liquid–liquid biphasic system was formed when sugar-based DESs and n-propanol (NPA) showed incompatibility in an aqueous solution at above critical concentrations and 298.15 K. The DESs were prepared by choline chloride and sugars (sucrose, glucose, fructose, and xylose). The influence of the hydroxyl group and structure of HBD on the phase behavior was evaluated using phase diagrams and tie-lines length (TLL). Results showed that the biphasic region of DESs-based system was expanded by enhancing the hydrophilic of HBD. Each HBD (sucrose, glucose, fructose) and choline chloride can form ternary system with NPA and water. With this phase behavior, the molar ratio of DESs in two phases is the same as the original ratio of the DES formation. A non-random two-liquid (NRTL) model was used to correlate the tie-lines data of the systems, and the binary interaction parameters of the model were then obtained. Shikimic and vanillic acids used as biomolecule probes in two phases was studied to further explore the extraction potential of these DES-based systems. This work showed that the nature of HBDs influences the distribution behavior of shikimic and vanillic acids. And the DES-based systems presented higher extraction efficiencies (from 88.02% to 91.90%) for shikimic acid, which shows good extraction levels.