Vapor-liquid equilibria (VLE) for two binary systems 1-propanol + water and methyl acetate + methanol, and the ternary mixtures with the ionic liquid 1-ethyl-3-methylimidazolium ethyl sulfate [EMIM](+)[EtSO4](-) as entrainer were measured by headspace gas chromatography. From the experimental VLE data, the influence of the ionic liquid on the separation factors was investigated. The experimental results for the ternary systems show that [EMIM](+)[EtSO4](-) has a great influence on the separation factors of the systems investigated. Furthermore, the experimental separation factors were compared with the predicted ones of other ionic liquids and conventional selective solvents using modified UNIFAC (Dortmund). (C) 2011 Elsevier B.V. All rights reserved.