Aqueous two-phase systems for protein separation studies on phase inversion

Jose C. Merchuk, Barbara A. Andrews, Juan A. Asenjo

Research output: Contribution to journalArticlepeer-review

637 Scopus citations


Phase equilibrium studies were done with the PEG 400-phosphate system, obtaining equilibrium binodal lines, tie lines and phase inversion points. A method of calculation of the critical point on the binodal curve is described. The influence of the presence of NaCl in solution was studied, and the comparative results are presented. It was found that in some range of concentration the shift produced in the binodal line can be important. The rate of phase separation can be used as an indication of which of the phases is continuous. Using this method the phase inversion point can be determined in the system for each tie line. A range of ambiguity was found, where the continuity of the phases is affected not only by the composition of the mixture, but also by the fluid dynamics. Within this range, gentle agitation produces a bottom-continuous suspension, while strong agitation produces a top-continuous suspension. Two inversion points exist therefore on each tie line, delimiting on the phase equilibrium plane a region where the phase continuity depends on fluid dynamics. The convergence of this region towards the critical point can be used to control of the consistency of the experimental data.

Original languageEnglish
Pages (from-to)285-293
Number of pages9
JournalJournal of Chromatography - Biomedical Applications
Issue number1-2
StatePublished - 26 Jun 1998


  • Aqueous two-phase systems
  • Phase inversion
  • Proteins

ASJC Scopus subject areas

  • Chemistry (all)


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