Binodal curves of the aqueous 1-butyl-3-methylimidazolium tetrafluoroborate ([Bmim]BF4) + sodium citrate (Na3C6H5O7) and [Bmim]BF4 + ammonium tartrate ((NH4)3C6H5O7) systems have been determined experimentally at T = (298.15, 308.15, and 323.15) K. The Merchuk equation was used to correlate the binodal data. The effective excluded volume (EEV) values obtained from the binodal model for these two systems were determined. The binodal curves and EEV both indicate that the salting-out abilities of the two salts follow the order: Na3C6H5O7 > (NH4)3C6H5O7. It was demonstrated that the two-phase area was expanded with a decrease in temperature, while the slope of the tie lines slightly decreases with an increase in temperature. The liquid−liquid equilibrium (LLE) data were obtained by density determination and binodal curves correlation of these systems. The Othmer−Tobias and Bancroft and two-parameter equations were used for the correlation of the tie-line data. Good agreement was obtained with the experimental tie-line data with both models.

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The effective method of ionic liquid-based aqueous two-phase extraction, which involves ionic liquid (IL) (1-butyl-3-methyllimidazolium chloride, [C4mim]Cl) and inorganic salt (K2HPO4) coupled with high-performance liquid chromatography (HPLC), has been used to extract trace tilmicosin in real water samples which were passed through a 0.45 μm filter. The effects of the different types of salts, the concentration of K2HPO4 and of ILs, the pH value and temperature of the systems on the extraction efficiencies have all been investigated. Under the optimum conditions, the average extraction efficiency is up to 95.8%. This method was feasible when applied to the analysis of tilmicosin in real water samples within the range 0.5-40 μg mL(-1). The limit of detection was found to be 0.05 μg mL(-1). The recovery rate of tilmicosin was 92.0-99.0% from the real water samples by the proposed method. This process is suggested to have important applications for the extraction of tilmicosin.