General Concepts and Definitions of Aqueous Two-Phase Systems

Abstract

Aqueous two-phase systems (ATPS) are biphasic systems composed, traditionally, by two polymers or one polymer and one salt. However, the classification currently includes ATPS formed by ethanol, micelles, and ionic liquids. ATPS are a liquid–liquid separation technology used as primary recovery technique. This technology has been used to separate a wide spectrum of biomolecules as proteins, cells, DNA, virus-like particles, low molecular weight compounds, metals, etc. ATPS are designed by a binodal curve with the exact composition and conditions for each pair of components of the system. The binodal curve is used to determine the tie-line length and volume ratio of the systems, two of the principal parameters that determine the partition behavior in the system. ATPS has been classified in five groups: polymer–polymer, polymer–salt, alcohol–salt, micellar, and ionic liquid-based systems. All these systems possess specific characteristics that allow the separation of a wide diversity of biomolecules. The objective of this chapter is to define all general concepts in the ATPS study. In this regard the reader is introduced to the definitions of the parameters with which the partition behavior is evaluated: partition coefficient, selectivity, recovery yield, and purity. Furthermore, the molecular mechanisms and parameters (molecular size, electrochemical charge, hydrophobicity, etc.) involved on the partition of solutes in ATPS are underlined.