Aqueous two-phase separation (ATPS) is a powerful, greener tool for the
partitioning-based extraction and concentration of compounds in a mixture. ATPS is
characterized by the separation of the biphasic layers upon the addition of the aqueous
salt solution to aqueous ionic liquids. The aqueous biphasic system using chiral ionic
liquids (CILs) has been studied for the resolution of the chiral molecules and their
enantioseparation. Thus, in this chapter, abrief introduction to the ATPS formation
thermodynamics for the polymer-polymer, polymer-salt, and salt-salt type ionic liquid
isgiven. Apart from this, the effect of the salt, pH, and temperature on the
physicochemical behavior of aqueous biphasic systems is discussed. The chiral ionic
liquid-based ATPS is further categorized as tetrabutylammonium, choline,
imidazolium, tropine, and quinine-based ionic liquids for enantioseparation. The study
includes the effect of salts, cation of IL, anion of IL, temperature, pH, and Cu2+ ions.
The chiral resolution of molecules and biomolecules is studied using these ionic liquids
for amino acids and proteins.
Keywords: Aqueous two-phase system (ATPS), Aqueous biphasic system (ABS), Chiral ionic liquids (CILs), Chiral resolution, Chiral separation, Enantiomeric excess, Ionic liquid, Tie line length.
