Influence of the presence of dioctyl sulfosuccinate sodium as adjuvant on the equilibrium data of aqueous two-phase systems formed by polyethylene glycol + potassium phosphate + water at 298.15 K

Abstract

Liquid-liquid equilibrium data were obtained for aqueous two-phase systems (ATPS) formed by polyethylene glycol (4000 or 6000 g mol−1) + potassium phosphate (K2HPO4/H3PO4 or K2HPO4) + water. The effect of adding (0.05%) [w/w] of the dioctyl sulfosuccinate sodium (AOT) to the polymeric solution was studied. ATPS were determined using the turbidimetric method, at two pH values (7.0 and 9.3) and 298.15 K. Three tie-lines (TL) were determined using the lever rule. The effect of the variables pH, polymer molar mass and presence of the surfactant on binodal curves and TL were evaluated. In order to study the capacity of phase formation and the salting-out ability of the system-forming components, the salting-out effect and effective volume (EEV) of exclusion were determined. An increase in the biphasic region at the highest values of pH and molar mass of PEG was verified. Such results were correlated with the values of the parameters coefficient salting-out (k) and EEV. The increase in the system global composition caused an increase on the tie-lines length, varying in the range of (0.243–0.415). The different conditions determined had little effect on the tie-lines slope (STL). It was found that the presence of AOT in these ATPS caused a decrease in the EEV values of the systems (4285.916 − 6987.256).