Phase Behavior of Ionic Liquids-Cesium Carbonate-Water Aqueous Two-phase Systems and Their Extraction of L-Tryptophan

Phase behavior and extraction ability of aqueous two-phase systems(ATPs) consisting of ionic liquids(ILs), Cs₂CO₃ and water were investigated in this paper. Four kinds of ionic liquids, namely, 1-amyl-3-methylimidazolium bromide(C₅mim]Br), 1-hexyl-3-methylimidazolium bromide(C₆mim]Br), 1-heptyl-3-methylimidazolium bromide (C₇mim]Br) and 1-octyl-3-methylimidazolium bromide(C₈mim]Br), were examined to discuss the influence of alkyl groups. Binodal curves and tie-lines at 288.15, 298.15 and 308.15 K were obtained. The partitioning behavior for L-tryptophan in such ATPs was further investigated. The effect of temperature, pH, Cs₂CO₃ concentration and the structure of ionic liquids on the partitioning were discussed in detail.