Development of temperature and pressure variable aqueous biphasic extraction system with superheated water

双水相体系(ATP)是由水、某些无机盐和水溶性聚合物混合而成，可用于各种化合物的分离。聚乙二醇组分具有无毒、不燃、不挥发等特点，因此，基于聚乙二醇组分的ATPS具有环境友好的特点。为了提高ATPS的分离选择性，扩大ATPS的适用范围，我们研制了一种可以在高温下进行萃取的ATPS萃取装置。从溶质与聚合物溶液相的相互作用和盐析效应的角度，研究了正构醇、酮和硝基烷烃在聚乙二醇钠盐形成的ATPS中的分布行为。结果表明，基于聚乙二醇基的ATPS和聚乙二醇凝胶体系的分离选择性基本相同。对聚乙二醇水溶液的差示扫描量热法研究表明，聚乙二醇聚合物形成一种水化结构，其组成为50%(w/w)的聚乙二醇单环氧乙烷或环氧乙烷的水化数为2.4，聚乙二醇水体系的分离选择性可归因于溶质化合物在水合聚乙二醇聚合物结构中的分配。此外，为了阐明聚合物的疏水部分对ATPS分离选择性的贡献，采用烷基键合二氧化硅颗粒填充柱，研究了无机阴离子在反相液相色谱中的保留行为。结果表明，在烷基键合二氧化硅表面形成了溶剂化水相，它对溶质化合物表现出不同于整体液态水的亲和力。

Aqueous two-phase systems (ATPS) are formed by mixing water, certain inorganic salts and water-soluble polymers and can be useful for the separation of various compounds. Polyethylene glycol (PEG) is nontoxic, nonflammable and nonvolatile so that the PEG-based ATPS can be regarded as environmentally friendly.We have developed an ATPS extraction device which enables one to carry out extraction at elevated temperature in order to enhance the separation selectivity and expand the applicability of ATPS. The distribution behavior of n-alcohols, ketones and nitroalkanes in ATPS formed from PEG and Na_2SO_4 was investigated from the viewpoints of interaction of the solutes with the polymer solution phase and the salting-out effect. The results obtained revealed that the separation selectivities exerted by the PEG-based ATPS and the PEG gel system are approximately the same. Differential scanning calorimetry studies on aqueous PEG solutions suggested that PEG polymer forms a hydration structure of which the composition is 50 % (w/w) PEG or the hydration number per ethylene oxide is 2.4 and the separation selectivity of the PEG-water systems can be ascribed to partition of solute compounds into the hydrated PEG polymer structure. Furthermore, it has been demonstrated that the separation selectivity of the ATPS depends strongly on temperature.Furthermore, in order to clarify the contribution of hydrophobic moieties of polymers on the separation selectivity of ATPS, the retention behavior of inorganic anions in reversed-phase liquid chromatography was investigated using the columns packed with alkyl bonded silica particles. From the results obtained, it has been concluded that the solvated water phase is formed on the surface of alkyl-bonded silica and exhibits an affinity to solute compounds different from that of the bulk liquid water.