Isoquinolinium ionic liquid has been studied as the temperature-composition phase diagrams of 13 binary mixtures composed of the ionic liquid (IL) N-octylisoquinolinium bis{(trifluoromethyl)sulfonyl}imide, ([C(8)iQuin][NTf2]) and an aliphatic hydrocarbon (n-hexane, or n-heptane), or cyclic hydrocarbons (cyclohexane, or cycloheptane), or an aromatic hydrocarbon (toluene, or ethylbenzene, or n-propylbenzene, or thiophene), or an alcohol (1-butanol, or 1-hexanol, or 1-octanol, or 1-decanol, or 1-dodecanol, or 2-phenylethanol), or water have been determined from ambient temperature to the boiling point temperature of the solvent at ambient pressure. A dynamic method was used over a broad range of mole fractions and temperatures from 270 to 360 K. For the binary systems the immiscibility in the liquid phase with an upper critical solution temperature (UCST) was observed in all mixtures. In the case of the mixture of {IL + alkylbenzene} only one experimental point of immiscibility was observed because of the very high UCSTs. Complete solubility in the liquid phase was observed for 1-butanol and 2-phenylethanol. In the mixtures with alcohols the typical dependence was observed that with an increasing chain length of an alcohol the solubility decreases and the UCST increases. The coexistence curves corresponding to liquid-liquid phase equilibrium (LLE) boundaries have been correlated using the well-known NRTL model. The ternary system of {[C(8)iQuin][NTf2] (1)+2-phenylethanol (2)+ water (3)} was studied at 298.15 K to analyze the performance of the ([C(8)iQuin][NTf2]) in the extractive selectivity of 2-phenylethanol from medium of biosynthesis. From the ternary LLE experiments, it was found that the selectivities and the distribution coefficients of the 2-phenylethanol were as high as 1539 and 1214. The experimental results were correlated using the NRTL model. The root mean square deviation (RMSD) of mole fraction in ternary system was 0.003. (C) 2011 Elsevier B.V. All rights reserved.