The partition of sodium phosphate and sodium chloride in aqueous dextran poly(ethylene glycol) two-phase systems

• Published in: Journal of colloid and interface science Vol. 99; no. 1; pp. 187 - 193
• Main Authors: Bamberger, Stephan, Seaman, Geoffrey V.F, Brown, Julie A, Brooks, Donald E
• Format: Journal Article
• Language: English
• Published: San Diego, CA Elsevier Inc 1984; Elsevier
• Subjects: Applied sciences; Exact sciences and technology; Natural polymers; Physicochemistry of polymers; Starch and polysaccharides; Dextran; Ethylene oxide polymer; Phase diagram; Content; Influence; Polarimetry; Aqueous solution; Sodium Phosphates; Equilibrium dialysis; Mixture; Sodium Chlorides
• ISSN: 0021-9797; 1095-7103
• DOI: 10.1016/0021-9797(84)90099-7

It is known that the addition of phosphate buffer to two polymer aqueous phase systems has a strong effect on the partition behavior of cells and other particles in such mixtures. The addition of sodium phosphate to aqueous poly(ethylene glycol) dextran phase systems causes a concentration-dependent shift in the binodial on the phase diagram, progressively lowering the critical conditions for phase separation as the phosphate concentration is increased. Sodium chloride produces no significant shift in the critical point relative to the salt-free case. Accurate determinations of the phase diagram require measurements of the density of the phases; data are presented which allows this parameter to be calculated from polarimetric measurements of the dextran concentrations of both phases. Increasing polymer concentrations in the phase systems produce increasing preference of the phosphate for the dextran-rich bottom phase. Equilibrium dialysis experiments showed that poly(ethylene glycol) effectively rejected phosphate, and to a lesser extent chloride, but that dextran had little effect on the distribution of either salt. Increasing ionic strength via addition of 0.15 M NaCl to phase systems containing 0.01 M phosphate produces an increased concentration of phosphate ions in the bottom dextran-rich phase.