Polyethyene glycol (PEG) and salt based aqueous two-phase systems (ATPSs) are a green chemistry alternative to the to use of organic solvents as shown by their many applications for the extraction, purification, and seperation of a wide range of chemical substances. The formation of an ATPS was primarily influenced by the average molecular mass of PEG, the identity of the salt, and the concentrations of both the PEG and the salt. Particular attention was placed on observing trends that predict which organic or inorganic salts were most likely to sucessfully form ATPSs. Over 60 salts were initially screened with PEG 1000, salt, and water proportions of 17.5%, 17.5% and 65% (w/w) respectively. Under these conditions, 16 salts formed ATPSs. Successful ATPS formulations were tested at lower mass percents of PEG 1000 and salt to observe their ATPS forming power. Subsequently, 9 other salts were coaxed into creating ATPSs by increasing the molecular mass of PEG. In examining the trends, it was observed that only polyanionic oxide salts formed ATPSs. Water solubility of these polyanionic oxide salts, related to both cation and anion identities, was significantly correlated to ATPS formation. A method of classifying ATPS forming power was created. Inorganic salts such a carbonate, sulfate, phosphate, molydbate, and sulfite were ATPS forming anions along with represenatives of citrate, tartrate, oxalate, and gluconate organic salts. The ATPS forming power of salts was shown to be pH dependent.

Tuneable parameters for the preparation of aqueous two-phase systems

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