Influence of the temperature and type of salt on the phase equilibrium of peg 1500 + potassium phosphate and peg 1500 + sodium citrate aqueous two-phase systems

Abstract

Recebido em 6/10/06; aceito em 24/8/07; publicado na web em 19/12/07The present work analyzed the effect of the temperature and type of salt on the phase equilibrium of aqueous two-phase systems (ATPS) formed by poly (ethylene glycol) (PEG) 1500 + potassium phosphate, from (278.15 to 318.15) K, and PEG 1500 + sodium citrate, from (278.15 to 298.15) K. The rise of the temperature normally increased the slope of the tie line (STL). With respect to the influence of the type of salt, sodium citrate showed better capability to induce phase separation, when compared to potassium phosphate.

(Liquid+liquid) equilibrium of (NaNO3+PEG 4000+H2O) ternary system at different temperatures

“…Figure 1 shows that the sodium nitrate increases its capacity to induce the phase separation as temperature increases. According to Silva and Loh [38] and Carvalho et al [39], one can supposes that the polymer and sodium nitrate interactions decrease as temperature increases, thus, a lower concentration of sodium nitrate is bound to the polymer, leaving a large fraction of sodium nitrate in bulk solution, which reaches more easily the amount of free electrolyte necessary to cause phase separation.…”

“…The STL explains the effect of the operational conditions on system compositions. This value is computed as the ratio between the variation of the polymer and salt concentration in each phase of the system [39,40]:…”

Thermodynamic studies of partitioning behavior of lysozyme and conalbumin in aqueous two-phase systems

“…Biphasic systems were prepared by mixing PEG 1500 and an inorganic salt (sodium citrate or sodium sulfate) according to liquid-liquid equilibrium data cited by Carvalho et al [10] and Martins et al [11].…”

Partitioning of Geotrichum candidum Lipase from fermentative crude extract by aqueous two-phase system of polyethylene glycol and sodium citrate

“…The ATPS formed by PEO (1500 or 4000 or 6000 g mol -1 ) + sodium citrate + water or L35 (1900 g mol -1 ) + sodium citrate + water were prepared in five different compositions in accordance with the phase diagrams described in the literature [21][22][23]. After mixing the stock solutions, the systems were vigorously agitated and then left to rest for 24 h in a Vortex …”