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An aqueous solution of a tri-block copolymer PPG–PEG–PPG has been used with two organic salts, sodium acetate and sodium citrate, to create new aqueous biphasic systems (ABS).

An aqueous biphasic system (ABS) was obtained after mixing an amino acid (l-proline) solution (5 mol·kg–1) with a 0.90 g·g–1 solution of nonionic surfactant (Triton X-100). The phase diagram of the system was constructed at 296 K. The system was found to work in a more efficient and economic way when the surfactant is enriched with a cosolute, isoamyl alcohol in a ratio of 2:1. The addition of isoamyl alcohol results in a decrease in density of the surfactant phase, much below the density of a dilute solution of proline (0.1 mol·kg–1). This results in very low consumption of the amino acid for the design of the ABS. The tolerance of the ABS toward changes in pH and concentrations have been found to improve drastically in the presence of the cosolute. When sodium alginate is used as a complexing agent, the developed system shows a pH-dependent separation for the alkaline earth metal ions Mg2+, Ca2+, Sr2+, and Ba2+ from one another. Detection of these metal ions after their separations has been achieved with eriochrome black T (EBT; for Mg2+ at pH 9.5) and arsenazo III (for Ca2+, Sr2+, and Ba2+ at pH 7.2) using absorption spectrometry. As different pH values are suitable for the complexation and extraction of different alkaline earths, it is possible to have a sequential separation of the individual elements from a mixture as and when required.

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This article describes a newly designed block copolymer based aqueous biphasic system (ABS, composed of two immiscible aqueous phases) which is further utilized to study extraction behavior of three iodine species viz., I 2 , I À , and IO 4 À . Phase diagram and tie line data reveals the potential working range of this new biphasic system. Fluorescence, dynamic light scattering, transmission electron microscopy (TEM) and conductance data establish the micellar arrangement in solutions of this particular block copolymer.Elemental iodine is easily soluble in copolymer solution due to charge transfer complexation. Polymer phase of the ABS is found to have species dependent selectivity of extraction for the three different iodine species. Two non toxic, non flammable dyes 3,6-diamino-10-phenylphenazinium chloride (DPC) and haematoxylin are introduced for the first time to detect iodide and periodate species respectively in the copolymer medium.