Enantioselective Extraction of Mandelic Acid Enantiomers by Aqueous Two-Phase Systems of Polyethylene Glycol and Ammonium Sulfate Containing β-Cyclodextrin as Chiral Selector
L. Tan, Y. Long, F. Jiao and X. Chen*
College of Chemistry and Chemical Engineering, Central South University, Changsha 410083, China
A new chiral separation technology, aqueous two-phase extraction, was proposed for the separation of racemic mandelic acid. The distribution behavior of mandelic acid enantiomers was investigated in aqueous two-phase systems composed of polyethylene glycol and ammonium sulfate containing β-cyclodextrin as chiral selector. The influences of the pH, the mass fraction of polyethylene glycol and ammonium sulfate, the polymerization degree of polyethylene glycol, the initial concentration of β-cyclodextrin, mandelic acid enantiomers and extractive temperature on the distribution behavior were studied respectively. The results show that β-cyclodextrin is inclined to recognize L-enantiomer; under the optimized conditions, the separation factor reaches 2.46 and the enantiomeric excess is 42.13% in the top phase and 40.43% in the bottom phase, respectively. Aqueous two phase chiral-extraction with strong chiral separation ability, plays great role in preparative separation of racemic compounds and is important for the development of aqueous two phase extraction technique.
Keywords: Aqueous two phase extraction, Chiral separation, Mandelic acid enantiomers, β-cyclodextrin