In the present work, (liquid + liquid) equilibrium data have been determined experimentally for aqueous two-phase systems formed by the imidazolium ionic liquids of [C(n)mim][CH3COO] (n = 4, 6, 8) and inorganic salts of K3PO4, K2HPO4, and K2CO3 at T = 298.15 K. Combined with available data in the literature, the effect of alkyl chain length of cations, type of anions of the ionic liquids, and nature of the inorganic salts were examined on the binodal curves of the systems. Then the binodal curves were fitted to a four-parameter empirical equation, and the tie-lines were described by the Othmer-Tobias and Bancroft equations. In addition, the extraction capacity of the {[C(n)mim][CH3COO] (n = 4, 6, 8) + K3PO4} aqueous two-phase systems was evaluated through their application to the extraction of L-tryptophan. The high extraction efficiency suggests that these aqueous two-phase systems are feasible to be used in the extraction and separation process. (c) 2010 Elsevier Ltd. All rights reserved.