Ternary aquous solutions of water soluble polymers and certain electrolytes separate into a polymer-rich and a salt-rich phase over part of the composition space. Aquoes two-phase systems of this nature are useful for the separation and purification of biomaterials where the employment of a nonpolar solvent/aqueos phase system whould lead to degradation of biological activity [1 , 2 [.Polyethylene glycol (PEG), which is a hydrolic polymer, is often used in aqueous two-phase partitioning studies.
