Novel aqueous two-phase systems composed of acetonitrile and polyols: Phase diagrams and extractive performance

A large number of works has been devoted to the study of alternative constituents to form aqueous two-phase systems (ATPS); however, scarce attention has been given to polyols as two-phase forming components. This work addresses the potential use of polyols (glycerol, erythritol, xylitol, sorbitol and maltitol) to create ATPS in presence of acetonitrile. Novel ternary phase diagrams were determined at 298 K and the impact of the polyol chemical structure through the liquid-liquid demixing was evaluated. It is shown that the ability for phase separation largely depends on the number of hydroxyl groups present in each polyol. Polyols with a higher number of hydroxyl groups are better phase separating agents increasing thus the ability for two-phase formation. The partitioning of a model biomolecule, vanillin, was also assessed to ascertain on these systems applicability as alternative extractive techniques. In all systems, vanillin preferentially migrates to the acetonitrile-rich phase (more hydrophobic layer) with recoveries higher than 89%, except to glycerol. This pattern was confirmed by solid-liquid solubility studies of vanillin in aqueous solutions containing diverse polyols supporting thus their phase separating ability. These novel systems can be used as alternative ATPS for the extraction and recovery of added-value biomolecules.