The phase diagrams of aqueous biphasic systems impart a distinct idea regarding the feasibility of biphase formation by different water soluble substances at their optimum concentrations. Depending on nature of the components viz., the water soluble polymers, surfactants, salts, amino acids or ionic liquids, a general trend of the biphase formation with varying temperature, pH and concentration has been studied over the recent years. This critical review is an endeavor to assess the general trends of these phase forming components to form biphasic systems with varying conditions of temperature and pH in light of the reported phase diagrams. Suitable explanations for the mechanisms of such behavior have been sorted out. The avenue yet to be explored has been addressed as these systems have a tremendous potential to be the future platform to solve different analytical issues. © 2016 Elsevier B.V.

KAMALIKA SEN

Chemistry

A CHAKRABORTY

University of Calcutta (informally known as Calcutta University or CU) is a collegiate public state university located in Kolkata, West Bengal, India.&nbsp;Within India it is recognized as a &quot;Five-Star University&quot; and accredited &quot;A&quot; Grade by National Assessment and Accreditation Council.

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The University of Calcutta has secured the Fifth position among the Universities of India in the prestigious &quot;Indian University Ranking 2019&quot; list, released by the NIRF of the Ministry of Human Resource Development, Government of India.

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It was established on 24 January 1857, and was one of the first institutions in Asia to be established as a multidisciplinary and Western-style university. Its alumni and faculty include several heads of state, heads of government, social reformers, prominent artists, only academy award winner and Dirac medal winner in India, many Fellows of the Royal Society and five Nobel laureates as of 2019 which is highest in South Asia.

University Of Calcutta

Journal of Chromatography A

A new aqueous biphasic system (ABS) was designed by mixing aqueous solutions of tri-block copolymer polypropylene glycol-block-polyethylene glycol-block-polypropylene glycol (PPG-PEG-PPG) with a nontoxic ionic liquid tris (2-hydroxyethyl) methyl-ammonium methyl sulfate. Well defined phase diagram validated with Merchuk equation along with suitable tie-lines was obtained by turbidometric titration method at 298&nbsp;K. The tie-line lengths and slope of tie lines were calculated and the results were validated using Othmer-Tobias and Bancroft equations. The newly designed ABS has been used to perform the extraction studies of cholesterol, zinc and Zn-cholesterol complex at different pHs of the solution. Zn-cholesterol complex was found to be formed at an acidic pH (1.5). The stability constant value of Zn-cholesterol complex was obtained in ethanolic medium, pristine polymer medium and in the ABS extracted polymer rich phase using Benesi-Hildebrand equation. The aggregation number of PPG-PEG-PPG solution obtained after extraction of cholesterol and Zn-cholesterol complex in ABS was found to be greater in comparison to the pristine copolymer solution. Kinetic spectrophotometric studies were also supporting higher stability of Zn-cholesterol complex in the ABS extracted polymer rich phase. Zn-cholesterol complex formation in acidic micellar medium (pH&nbsp;1.5) also falls in the pH range of normal human stomach and may offer a suitable method of zinc supplementation by absorption via cell membrane that resembles with the polymeric micellar aggregation. © 2016 Elsevier B.V.

Journal of Molecular Liquids

Ionic liquid vs tri-block copolymer in a new aqueous biphasic system for extraction of Zn-cholesterol complex

Polyvinylpyrrolidone (PVP) forms aqueous biphasic systems with tri-block co-polymers, surfactants and salts. The phase diagrams of PVP-salt and PVP-surfactant systems were constructed by a turbidometric titration method at 296 K. Density measurements of the phase forming solutions at this temperature also led to an attractive outcome of the formation of two tri-phasic systems among the components of our study (Na-tartrate + PVP + Triton-X-100 and Na-tartrate + PVP + PPG-PEG-PPG). We also constructed a spreadsheet reflecting the relationship between miscibility and the possibility of phase separation between the components, consisting of the seven phase forming solutions to open up different possibilities of ABS formation. Some completely new biphasic systems were obtained as well as the process of gel formation of a PVA solution in the presence of salt and polymer solutions was also observed. The applications of some of the developed ABSs are described for the recovery of an antibiotic drug, amoxicillin and a catalyst, molybdenum disulphide. © The Royal Society of Chemistry 2014.

RSC Advances

Phase separation in aqueous systems for realizing virtually significant extractions

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 Ba 2+ 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. © 2014 American Chemical Society.

Journal of Chemical and Engineering Data

L -proline based aqueous biphasic system: Design and application to isolate the alkaline earths

A clean liquid-liquid extraction system was designed for extraction of three different heavy metals (Hg 2+, Pb 2+ and Bi 3+) using an Aqueous Biphasic System consisting of a nonionic surfactant Triton X-100 in combination with two different salts viz., magnesium sulphate and sodium citrate. The extraction was monitored in two ways, by direct partitioning as well as by forming a complex with diphenylthiocarbazone (dithizone) for each metal ion in the Triton phase and measuring the colour intensity using a spectrophotometer. The change in extraction pattern at different pH of the salt rich phase was monitored. The possible change in speciation of these metal ions with pH was checked with the software programme 'CHEAQS' (Chemical Equilibria in Aquatic Systems). These heavy metals were also found to have higher extraction in the Triton phase when a prior complexation with dithizone was performed. The method may find extensive applications for the removal and decontaminations of the above mentioned toxic heavy metals from a sample. © 2011 The Korean Society of Industrial and Engineering Chemistry.

Journal	Data powered by TypesetJournal of Chromatography A
Publisher	Data powered by TypesetElsevier B.V.
ISSN	0021-9673