(216b) Phase Separation Conditions for Sugaring-out in Acetonitrile-Water Systems

In recent years, phase separation from a homogeneous solution by creating a second immiscible phase has been investigated as an alternative to the traditional liquid-liquid extraction for separation of chemical species and recovery of biological products. The techniques that have been exploited include salting-out and aqueous two-phase systems, each with its advantages and shortcomings. Sugaring-out is a new phase partition method in which a monomeric carbohydrate or a disaccharide is used to trigger phase separation in an acetonitrile-water mixture. The addition of sugar (monomers or disaccharides) above a critical concentration in the mixture induces two-phase formation, with upper phase rich in acetonitrile and lower phase rich in water. The sugaring-out may provide an entirely new platform for extraction of organic compounds and other products from aqueous phase. However, as a new phase separation method, the conditions for sugaring-out in the form of phase diagram have not been reported. The current work was undertaken to investigate the effect of temperature (6 ? 15oC) and sugar concentration (105 - 180 g/L) on two-phase formation and selectivity of acetonitrile from aqueous phase. The selectivity and two-phase separation improved with increase in sugar concentration and decrease in temperature. For each temperature above certain sugar concentration (critical value) no significant change in upper phase composition occurred. This critical value increased with increase in temperature. Phase ratios (ratio of the volume of upper phase to the volume of lower phase) increased till the critical sugar concentration and remained constant thereafter. At the same sugar concentration, the phase ratios decreased with an increase in temperature.