Phase behavior of aqueous biphasic systems composed of novel choline amino acid ionic liquids and salts

Abstract

Phase diagrams of a series of ionic liquid-based aqueous biphasic systems (ILABS) composed of novel choline amino acid ionic liquids and inorganic salts were measured experimentally at T=(288.15, 298.15 and 308.15) K. Ionic liquids, salts, and temperature influenced the phase separation ability of the studied ILABS. Several parameters of the Merchuk equation were estimated by fitting the binodal curve data. Liquid-liquid equilibria of the investigated ILABS were determined by a gravimetrical method, including the tie-line lengths and slope of the tie-lines. Critical points of the corresponding ILABS were obtained by a mathematical calculation different from the conventional extrapolation. In the case of the phenylalanine+K3PO4+H2O system at 298.15K, the gravimetrical method and the mathematical calculation were validated by the tie-lines determined experimentally and the critical point derived from the extrapolation.