| A review of mainly chiral separation method, mainly liquid-liquid systems and their research actuality was given in detail. Kinds of aqueous two-phase system (ATPS) and their application in chiral separation as well as system property were also presented in this paper. Two kinds of ATPS and experimental designs were introduced to separate tryptophan (Trp), ofloxacin (OFLX) and chlortalidone enantiomers. Finally, most reasonable extraction mechanisms were suggested.(1) Trp was used as model molecule to investigated the enantioselectivity of ethanol/salts ATPS. Finally the extraction mechanisms was suggested. The titration method (cloud point method) was used to determine the phase diagrams for evaluate the phase separation ability of phase-forming salts. Various factors such as composition of system, the type of β-cyclodextrins derivatives (β-CDs) and mass fraction of β-cyclodextrins (β-CD) in initial feed, pH and temperature were studied to investigate their effect on enantioselectivity. The experimental results showed that only limited types of salt can form effective two phases with ethanol, enantioseparation are highly dependent on mass fraction of phase-forming salt or ethanol, pH of system, the type of chiral extractant and its concentration. Temperature also have some effects on the enantioseparation.(2) L-tartaric acid (L-TA) and hydroxypropyl-β-cyclodextrin (HP-β-CD) were used as chiral selectors to resolution of ofloxacin enantiomers in polyethylene glycol-based (PEG) aqueous biphasic systems. The influences of various factors on the partitioning and enantioselectivity of ofloxacin were studied. The variation of ratio of top-phase to bottom-phase with amount of PEG or salt was also presented. Experimental results showed that utilizing the cooperations of the L-TA and HP-β-CD, the system shows stronger enantioseparation ability than the monophasic recognition extraction. Compared to traditional organic/ water system, L-TA was used directly as selector without derivative experiments, the experimental procedure was simplified.(3) In this section, analysis condition of chlortalidone enantiomer was optimized and an orthogonal experimental design was used to study the distribution behavior of chlortalidone enantiomers in ATPS. Based on the ATPS system feature, extraction behavior of ATPS as well as properties of chlortalidone, an L9(3,4) orthogonal experimental was designed to evaluate the influence of factors on enantioselectivity in ATPS. Strong hydrophobicity of chlortalidone results in enantiomers largely distributing in top phase. Though a large mount of chiral selectors was added into the system, the partition coefficient (K) was unusually high, while separation factor (a) was really small. The ATPS is not good choice for separating of hydrophobic enantiomers. Figures19, Tables15, References99. |
