title: Specific cooperative effect for the enantiomeric separation of amino acids using aqueous two-phase systems with task-specific ionic liquids.
abstract: Aqueous two-phase systems (ATPS) based on hydrophilic ionic liquid (IL) and inorganic salt solution were designed and prepared for the enantiomeric separation of racemic amino acids. Two different kinds of hydrophilic ionic liquids (IL-1 and IL-2) containing functional groups were synthesized to separate racemic amino acids. Preliminary experiments showed that d-enantiomer of amino acids cooperatively interacted with ILs, which pushed d-enantiomer to remain in the bottom IL-rich phase. By contrast, l-enantiomer was transferred into the top Na2SO4-rich phase. The enantioselectivity of IL-1 was better than that of IL-2 because of their different intermolecular interactions. Various factors influencing separation efficiency were also systematically investigated including extraction time, IL volume and temperature. Furthermore, the mechanism was studied by (1)H NMR and DFT calculations, which showed that the hydrogen bond between the carboxylate and amide groups and the resonance-assisted hydrogen bond between amino and hydroxyl groups conditioned the movement between the residues and ILs. Finally, IL-1 was validated with other general amino acids by the same procedures based on ATPS.
authors.affiliation: Department of Chemistry, Zhejiang University, Hangzhou 310027, China.
authors.forename: Datong
authors.initials: D
authors.lastname: Wu
authors.affiliation: College of Chemistry and Life Science, Zhejiang Normal University, Jinhua 321004, China.
authors.forename: Ying
authors.initials: Y
authors.lastname: Zhou
authors.affiliation: Department of Chemistry, Zhejiang University, Hangzhou 310027, China.
authors.forename: Pengfei
authors.initials: P
authors.lastname: Cai
authors.affiliation: Department of Chemistry, Zhejiang University, Hangzhou 310027, China.
authors.forename: Shanshan
authors.initials: S
authors.lastname: Shen
authors.affiliation: Department of Chemistry, Zhejiang University, Hangzhou 310027, China. Electronic address: panyuanjiang@zju.edu.cn.
authors.forename: Yuanjiang
authors.initials: Y
authors.lastname: Pan
mesh_terms: D000596:Amino Acids / Q000737:chemistry / Q000302:isolation & purification*; D006860:Hydrogen Bonding; D057927:Hydrophobic and Hydrophilic Interactions; D052578:Ionic Liquids / Q000737:chemistry*; D013237:Stereoisomerism; D013696:Temperature; D014867:Water / Q000737:chemistry*
chemical_list: D000596:Amino Acids; D052578:Ionic Liquids; D014867:Water
keywords: Aqueous two-phase systems; Enantiomeric separation; Racemic amino acids; Task-specific ionic liquids