title: Solvatochromic relationship: prediction of distribution of ionic solutes in aqueous two-phase systems.
abstract: Partition ratios of several ionic compounds in 20 different polymer/polymer aqueous two-phase systems (ATPS) containing 0.15 M NaCl in 0.01 M phosphate buffer, pH 7.4, were determined. The differences between the electrostatic properties of the phases in all the ATPS were estimated from partitioning of the homologous series of dinitrophenylated-amino acids. Also the solvatochromic solvent parameters characterizing the solvent dipolarity/polarizability (π*), solvent hydrogen-bond donor acidity (α), and solvent hydrogen-bond acceptor basicity (β) of aqueous media were measured in the coexisting phases of the ATPS. The solute-specific coefficients for the compounds examined were determined by the multiple linear regression analysis using the modified linear solvation energy relationship equation. The minimal number of ATPS necessary for determination of the coefficients was established and 10 ATPS were selected as a reference ATPS set. The solute-specific coefficients values obtained with this reference set of ATPS were used to predict the partition ratios for the compounds in 10 ATPS not included in the reference set. The predicted partition ratios values were compared to those determined experimentally and found to be in good agreement. It is concluded that the presented model of solute-solvent interactions as the driving force for solute partitioning in polymer/polymer ATPS describes experimental observations with 90-95% accuracy.
authors.affiliation: Laboratory of Separation and Reaction Engineering, Dpt. de Engenharia Química, Faculdade de Engenharia da Universidade do Porto, Rua Dr. Roberto Frias, s/n 4200-465 Porto, Portugal. ppalma@fe.up.pt
authors.forename: Pedro P
authors.initials: PP
authors.lastname: Madeira
authors.forename: Ana
authors.initials: A
authors.lastname: Bessa
authors.forename: Dragana P C
authors.initials: DP
authors.lastname: de Barros
authors.forename: Miguel A
authors.initials: MA
authors.lastname: Teixeira
authors.forename: Luís
authors.initials: L
authors.lastname: Álvares-Ribeiro
authors.forename: M Raquel
authors.initials: MR
authors.lastname: Aires-Barros
authors.forename: Alírio E
authors.initials: AE
authors.lastname: Rodrigues
authors.forename: Arnon
authors.initials: A
authors.lastname: Chait
authors.forename: Boris Y
authors.initials: BY
authors.lastname: Zaslavsky
mesh_terms: D000596:Amino Acids / Q000737:chemistry; D005591:Chemical Fractionation / Q000379:methods; D006860:Hydrogen Bonding; D006863:Hydrogen-Ion Concentration; D007477:Ions / Q000737:chemistry; D016014:Linear Models; D008956:Models, Chemical; D011108:Polymers / Q000737:chemistry*; D015203:Reproducibility of Results; D012965:Sodium Chloride / Q000737:chemistry; D012997:Solvents / Q000737:chemistry*; D055672:Static Electricity; D014867:Water / Q000737:chemistry*
chemical_list: D000596:Amino Acids; D007477:Ions; D011108:Polymers; D012997:Solvents; D014867:Water; D012965:Sodium Chloride