Physicochemical Characterization of the PEG8000-Na₂SO₄ Aqueous Two-Phase System

Abstract

The polyethylene glycol-sodium sulfate aqueous two-phase system has been characterized at 23°C. Tielines for the phase diagram were obtained experimentally. Phases in equilibrium were characterized by means of the solvatochromic parameters π*, R, and , which provide a measurement of the polarity/polarizability and the H-bond donor and acceptor abilities, respectively. The ability of the phases to participate in hydrophobic interactions was characterized by means of the free energy of transfer of a methylene group between the conjugated phases, using the partition of a homologous series of dinitrophenylated amino acids. The results show the effect of the presence of polymer and salt in the aqueous phase, and a comparison of both phases with pure water is made.

Polyethylene glycol 8000+ citrate salts aqueous two-phase systems: Relative hydrophobicity of the equilibrium phases

“…When the logarithm of the partition coefficients of each DNP-amino acid, lnK, is plotted as a function of the TLL of the PEG-citrate ATPSs, a linear representation is obtained (Figure 1). A similar tendency was previously observed for other polymer-salt ATPSs [16,18]. The TLL is considered a measurement of the differences in phase composition and it becomes larger as the biphasic system moves into the heterogeneous region.…”

“…The procedure to obtain the partition coefficients of the DNP-amino acids has been explained in detail before [16][17][18][19]. Different amounts of a given DNP-amino acid stock solution (from 0 to 100 mg) were added to six replicates of a certain ATPS with the same feed composition.…”

“…The ∆G*(CH 2 ) for polymer-polymer ATPSs containing different buffers and NaCl as additive was determined using homologous series of DNP-amino acids [12,13] and aliphatic alcohols [14]. For polymer-salt ATPSs, the relative hydrophobicity was studied in biphasic systems of the type (PEG or UCON)-salt using the same homologous series of DNP-amino acids [16][17][18][19][20] or aliphatic alcohols [15]. Furthermore, the effect of different concentrations of salt additives (NaCl, NaSCN, NaClO 4 and NaH 2 PO 4 ) was investigated in PEG8000-Na 2 SO 4 ATPSs [19,20], showing that ∆G*(CH 2 ) become more negative when the concentration of the salt additive increases.…”

Gibbs free energy of transfer of a methylene group on {UCON+(sodium or potassium) phosphate salts} aqueous two-phase systems: Hydrophobicity effects

“…A deeper explanation can be found elsewhere [14,15]. Using a basic group-contribution concept, the logarithm of the partition coefficient ln K i can be accounted as the summation of two contributions: the alkyl part of the molecule (constructed by the summation of n methylene groups) and the non-alkyl part of the molecule, as follows [6,[21][22][23][24]:…”

Solute partitioning in polymer–salt ATPS: The Collander equation

“…The procedure to obtain the partition coefficients has been explained in detail before [15,16]. Suitable amounts of a stock solution of each solute (from 0 to 100 mg) were added to six replicates of the ATPS with the same feed composition.…”