| Aqueous two phase extration is a new and green separation and enrichment technology, and it has some advantages, such as simple, timesaving, efficient, green and eco-friendly, and it has been applied to the quantitative separation and extraction of metal ions, separation and purification of bioactivator and extraction of natural product. The existent aqueous two-phase system included polymer-polymer aqueous two-phase system, polymer-salt aqueous two-phase system, ionic liquid-salt aqueous two-phase system and micromolecule organic solvent-salt aqueous two-phase system. Because organic solvent is volatile and instable, the price of ionic liquid is higher and the viscosity of system containing two polymer is larger, the application of these three types of aqueous two-phase systems in large-scale industrial production was affected. One polymer of polymer-polymer aqueous two-phase system was replaced by salt, and it is polymer-salt aqueous two-phase system. The cost and viscosity of polymer-salt aqueous two-phase system is cheaper, and it has the advantage of good biocompatibility. It is applied in the separation and enrichment of bioactivator, natural product and antibiotic, and has high-exploited value and broad prospects on its application. The study of phase equilibrium theory and nature of aqueous two-phase system is the theoretical cornerstone to support its development, but the present study didn’t explain the formation mechanism of aqueous two-phase system and it did not predict its distribution mechanism of the matter in two phases, which restrict its development. As the guidance of its development, the thermodynamic theory of aqueous two-phase system is imperative for the further advances in the studies of aqueous two-phase system.As the significant milestone of the development history of biology and medical science, antibiotics played a great important role to promote the prevention and treatment in the disease of human and animal. With using antibiotics extensively in clinical medicine, breeding industry and food processing industry, the drug residue in food of animal originated the problem and the antibiotics environment pollution has attracted the people’s attention. The matrix elements of food and environment samples are complex and the samples contain many interfering substance, meanwhile, the residual antibiotics in real sample is trace or ultratrace. It is difficult to determine the trace of antibiotics only by using the available analysis and detection methods. Therefore, it is crucial to build up a simple, fast and effective pretreatment technology for separation and enrichment in order to determine the residual antibiotics.The aim of this paper is to establish the Brij35-salt aqueous two-phase extraction system, which will be applied to the separation and enrichment pretreatment of residual antibiotics in food and environment samples. The forming-phase abilities of salts and the thermodynamics behavior in forming-phase will be studied, which is the massy theoretical basis of the applied research of Brij35-salt aqueous two-phase system. The influence mechanism of the effect of influencing factors on the selective distribution behavior in system had been investigated, and the obvious significance and optimal experiment condition had been determined. These provided a new technological means and scientific basis for the separation and enrichment of other pollutant in food and environment samples. The concrete research content goes as follows:(1) The binodal curves data of14groups of Brij35-inorganic salt/organic salt aqueous two-phase system at different temperatures were determined, and the experimental data were fit by the experience equation. The optimal fitting equation was determined for each aqueous two-phase system. The liquid-liquid phase equilibrium data of14groups of Brij35-inorganic salt/organic salt aqueous two-phase system at different temperatures were determined by experiment or computer. The data were correlated and obtained the satisfactory fitting results.(2) The salting-out abilities of salts and the effect of temperature on the forming-phase conditions were deeply discussed through the effective exclude value of Brij35-salt aqueous two-phase system, the binodal curves diagram and the gibbs free energy of anion and cation. The conclusions can be drawn as follows:①The salting-out ability of salt with the same cation (or anion) is much stronger when the valence of anion (or cation) is higher.②When the cation of salt is same, its salting-out ability strengthened with the increase in effective exclude value and gibbs free energy of anion, namely, monovalent anion (OH-<C6H11O7-)<divalent anion (C2O42-<C4H4O62-<CO32-<HPO42+-)<trivalent (C6H5O73-<PO43-).③When the anion of salt is same, its salting-out ability strengthened with the increase in effective exclude value and gibbs free energy of cation, namely, NH4<K+<Na+, monovalent cation (Li+)<divalent cation (Zn2+<Mg2+).④Rising temperature leads to the increase in the value of effective exclude value, which indicated that the forming-phase abilities of ATPS enhanced, namely, the binodal curve moved towards the origin of coordinate, two-phase area expaned and the single phase area reduced.⑤The hydrophobicity of Brij35strengthened with the increase in temperature, which resulted in that the forming-phase ability of system enhanced and the absolute value of slope of tie-line rised.(3) The excess gibbs free energy of Brij35-salt aqueous two-phase system was represented by the sum of three components of long-range interaction contribution, short-range interaction contribution and combinatorial contribution because the electrolyte and polymer coexisted in aqueous two-phase system and each component influences each other. These three contributions were respectively represented by PDH equation, modified NRTL equation and Flory-Huggins equation, and the liquid-liquid phase equilibrium data were correlated by the thermodynamic work equation. The liquid-liquid phase equilibrium data that were not used in the correlation was obtained by the prediction of the thermodynamic work equation and its model parameter. The prediction data were compared with the experiment data, and it gave a satisfactory results.(4) The green separation/enrichment/detection technique coupling Brij35-organic salt/inorganic salt aqueous two-phase extraction system with high performance liquid chromatography was built in order to trace the residual antibiotics in food and environment sample.①The Brij35-NaH2PO4aqueous two-phase extraction system was constructed and used in the separation and enrichment of residual trace chloramphenicol in aquatic products and environment water samples. The response surface method was used in designing the experiment scheme and analyzing the experiment data, and it supports the following conclusions that the relationship between extraction efficiency and the experiment influence factors includes the concentration of NaH2PO4, the concentration of Brij35, and the temperature and pH of system is not linear; the interaction of influence factors also affected the extraction efficiency; the influence of the concentration of NaH2PO4and its temperature on extraction efficiency is significant.②The Brij35-(NH4)2SO4aqueous two-phase extraction system was applied to separate and enrich residual thiamphenicol in soil and bee products, the effect of experiment influence factors on the extraction efficiency and enrichment factor was discussed, the linear relation of extraction efficiency and influence factors was verified by the response surface method, and the optimal experiment conditions was found.③Based on the concept of environment friendly, the Brij35-organic salt (Na2C4H4O6) aqueous two-phase extraction system was coupled with high performance liquid chromatography, and this system was successfully applied to simultaneously separate and determine residual sulfadiazine and sulfamethazine in animal by-products and environment water samples. The influence intension of experiment factors on extraction efficiency and enrichment factor was studied and the optimal experiment condition was established. |
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