The present work focussed on screening of the environmental friendly imidazolium-based ionic liquid for the separations of (alkane/aromatic), (alkane/alk-1-ene), (cycloalkane/aromatic) and (water/alkan-1-ol) using (gas + liquid) chromatography (GLC) technique. In this reason the activity coefficients at infinite dilution, gamma(infinity)(13), for 29 organic solutes (alkanes, cycloalkanes, alkenes, alkynes, aromatics, alkanols and ketones) and water in ionic liquid 1-ethyl-3-methylimidazolium n-octylsulphate [EMIM](+)[OS] were measured at temperatures of (318.15, 333.15, 348.15 and 358.15) K. Stationary phase loadings of (23.77 and 40.76)% by mass were used to ensure repeatability of measurements. Uncertainties were determined using the law of propagation of uncertainty with an average absolute deviation of 2.53%. Density, viscosity and refractive index values were measured to confirm the purity of pure ionic liquid. Partial molar excess enthalpies at infinite dilution, Delta H-1(E,infinity), were also determined. The selectivities, S-ij(infinity), and capacities, k(j)(infinity), were determined for the separations of (alkane/aromatic), (alkane/alk-1-ene), (cycloalkane/aromatic) and (water/alkan-1-ol). The separating ability of the investigated ionic liquid was compared against previously investigated and industrial solvents such as sulfolane, n-methyl-2-pyrrolidine (NMP) and n-formylmorpholine (NFM). (C) 2015 Elsevier Ltd. All rights reserved.