Enantioselective extraction of phenylsuccinic acid in aqueous two-phase systems based on acetone and β-cyclodextrin...

A novel aqueous two-phase system (ATPS) composed of β-cyclodextrin (β-CD) derivative and acetone was developed for enantioselective extraction of racemic phenylsuccinic acid (PSA). Binodal curves, tie-lines, and critical points for the investigated ATPS were determined and the experimental tie-lines data were successfully correlated by Othmer-Tobias, Bancroft, and Setschenow-type equations. ATPS containing sulfobutyl ether-β-CD (SBE-β-CD) exhibited better enantioselectivity than that using carboxymethyl-β-CD (CM-β-CD). To optimize enantioselective partitioning conditions of PSA in acetone/SBE-β-CD ATPS, three factors (PSA concentration, pH, and equilibrium temperature) were analyzed by using central composite design in response surface methodology. The calculated equilibrium constants of inclusion complexation are 1638.64M^-1 for SBE-β-CD-(R)-PSA and 835.84M^-1 for SBE-β-CD-(S)-PSA, respectively. Under the optimized conditions, the separation factor of 3.14 and high enrichment efficiency (E_R=98.06%, E_S=99.25%) were simultaneously achieved in a single step.