Application of integral-equation theory to aqueous two-phase partitioning systems

Authors

  • C. A. Haynes,

    1. Dept. of Chemical Engineering and Chemical Sciences Division, Lawrence Berkeley Lab., University of California, Berkeley, CA 94720
    Current affiliation:
    1. Biotechnology Laboratory, University of British Columbia, Vancouver, B. C. V6T1Z3, Canada
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  • F. J. Benitez,

    1. Dept. of Chemical Engineering and Chemical Sciences Division, Lawrence Berkeley Lab., University of California, Berkeley, CA 94720
    Current affiliation:
    1. Ingenieria Quimica, Universidad de Extremadura, Badajoz, Spain
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  • H. W. Blanch,

    1. Dept. of Chemical Engineering and Chemical Sciences Division, Lawrence Berkeley Lab., University of California, Berkeley, CA 94720
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  • J. M. Prausnitz

    1. Dept. of Chemical Engineering and Chemical Sciences Division, Lawrence Berkeley Lab., University of California, Berkeley, CA 94720
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Abstract

A molecular-thermodynamic model is developed for representing thermodynamic properties of aqueous two-phase systems containing polymers, electrolytes, and proteins. The model is based on McMillan-Mayer solution theory and the generalized mean-spherical approximation to account for electrostatic forces between unlike ions. The Boublik-Mansoori equation of state for hard-sphere mixtures is coupled with the osmotic virial expansion truncated after the second-virial terms to account for short-range forces between molecules.

Osmotic second virial coefficients are reported from low-angle laser-light scattering (LALLS) data for binary and ternary aqueous solutions containing polymers and proteins. Ion-polymer specific-interaction coefficients are determined from osmoticpressure data for aqueous solutions containing a water-soluble polymer and an alkali chloride, phosphate or sulfate salt.

When coupled with LALLS and osmotic-pressure data reported here, the model is used to predict liquid-liquid equilibria, protein partition coefficients, and electrostatic potentials between phases for both polymer-polymer and polymer-salt aqueous two-phase systems. For bovine serum albumin, lysozyme, and α-chymotrypsin, predicted partition coefficients are in excellent agreement with experiment.

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