| Aqueous two-phase system,the development tendency of future environment friendly separation technology,which possesses advantages like user-friendly control,time saving,environmental friendly and efficient,has found wide application in the separation,purification and recovery of metal ions,bioactivators and natural products.The most frequently used aqueous two-phase systems mainly formed by polymer,ionic liquid or micro molecule organic solvent with salt.However,the industrialization process of aqueous two-phase extraction technology was affected due to the strong volatility of organic solvents,high cost of ionic liquids and high viscosity of polymer-polymer systems.Constructing quaternary aqueous two-phase systems by combining ionic liquid/polymer-based aqueous two-phase systems with micro molecule organic solvent systems could well reduce the cost and viscosity of extraction systems meanwhile retained excellent extraction characteristic of the ionic liquids and polymers.It is of high development value and broad application prospect.Researches on phase equilibrium theory and characteristic of liquid-liquid equilibrium are the theoretical cornerstone for the development of aqueous two-phase systems,but the existing research data and results could not distinctly reveal the mechanism of phase-forming process and the distribution behavior of target material between the two phases,which have restricted the application of aqueous two-phase systems.Therefore,it is essential to investigate the thermodynamics and kinetics of relevant aqueous two-phase systems.Antibiotics count for much in areas like medical and biology,which are used extensively in food manufacturing,clinical medicine as well as breed aquatics.They could effectively strengthen the control and prevention of diseases from human and other species.However,common occurance of contamination accidents brought by antibiotics has attracted much attention in these days.Given that the composition is complicated in food or other environment sample and there is little antibiotics contained therein,the key to detection of antibiotics is to to seek for simpler,more sensitive and more efficient pretreatment approaches.The aim of this work is to establish quaternary aqueous two-phase systems through a combination of traditional ionic liquid/ polymer-based ternary systems with small molecule organic solvent-based ones.A small molecular alcohol and an ionic liquid（or a polymer,or another small molecule organic liquid）were mixed in proper proportions and were seen as a whole.The phase separation abilities of salts and the thermodynamics were studied,which provided theoretical basis for the application of ionic liquid/ polymer/ small molecule organic solvent-based aqueous two-phase systems.These systems were then be applied to the extraction of antibiotic residues in food.The influences of various factors on the distribution behavior of target materials in two phases were discussed and the optimum experiment conditions were screened out,which provided novel technical measures and basis for the fractionation detection of antibiotics in food.The detailed contents are as follows:（1）The binodal curve data of various ethanol-isopropanol/[Bmim]BF4/PEG400-salt aqueous two-phase systems at different temperatures and organic component ratios were determined and fitted with several nonlinear equations.The optimal fitting equation was selected.The liquid-liquid equilibrium data of ethanol-isopropanol/[Bmim]BF4/PEG400-salt aqueous two-phase systems at different temperatures and organic component ratios were calculated by the ―lever arm rule‖ and the data were satisfactorily represented by nonlinear fitting.Furthermore,the NRTL and UNIQUAC models were employed for the simulation and prediction of liquid-liquid equilibrium data,and favorable results were gained.（2）The effect of salt species,temperatures,organic component ratios and system types on the phase separation capabilities were deeply discussed through analyzing the effective exclude values,phase diagrams and tie-line lengths of ethanol-isopropanol/[Bmim]BF4/ PEG400-salt aqueous two-phase systems at different temperatures and organic component ratios.The following conclusions were drawn:（1）The salting-out capabilities of anions follow: CO32->SO42-,CO32->H2PO4-while the salting-out abilities of cations follow: Na+>NH4+,which are consistent with the analysis results of Hofmeister series and the Gibbs free energy theory of hydrate;（2）The phase separation ability of ethanol-isopropanol-（NH4）2SO4 ATPS increases as temperature decreases whereas higher temperature means stronger phase separation ability of ethanol-PEG400-Na2SO4 ATPS;（3）The phase separation ability of ethanol-isopropanol system is strengthened as the ratio of isopropanol in the alcohol mixture increases;The phase separation ability of ethanol-ionic liquid system is strengthened as the ratio of [Bmim]BF4 in the organic mixture increases;（4）The phase separation capabilities of different systems follow the order of ionic liquid-ethanol system > isopropanol-ethanol system ≈ polymer-ethanol system.（3）The separation and detection technique was established with（[Bmim]BF4+ethanol）-inorganic salt aqueous two-phase extraction systems coupled with high performance liquid chromatography for antibiotic residues in food.（1）The（[Bmim]BF4+ethanol）-Na2CO3 aqueous two-phase system was constructed for the separation and determination of residual penicillin in alcohol products.The effects of multiple parameters on the extraction procedure of penicillin,including time,temperature,pH,concentrations of Na2CO3 and [Bmim]BF4-ethanol mixture,were studied and the optimal conditions for extraction process were determined;（2）The（[Bmim]BF4+ethanol）-NaH2PO4 aqueous two-phase system was constructed for the separation and determination of residual erythromycin in milk and honey.The effects of multiple parameters on the extraction procedure of erythromycin,including time,temperature,pH,concentrations of Na2CO3 and [Bmim]BF4-ethanol mixture,were studied and the optimal conditions for extraction process were determined. |
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