The activity coefficient at infinite dilution (gamma(infinity)(13)) for 30 solutes: alkanes, alkenes, cycloalkanes, alkynes, ketones, alcohols, and aromatic compounds was determined from gas-liquid chromatography (glc) measurements at three temperatures (303.15, 313.15, and 323.15) K. The ionic liquid: trioctylmethylammonium bis(trifluoromethylsulfonyl)imide, was used as the stationary phase. For each temperature, gamma(infinity)(13) values were determined using two columns with different mass percent packing of the ionic liquid. The selectivity (S-12(infinity)) value was calculated from the gamma(infinity)(13) to determine the suitability of the solvent as a potential entrainer for extractive distillation in the separation of an hexane/benzene mixture, indicative of a typical industrial separation problem for benchmarking purposes. (C) 2009 Elsevier Ltd. All rights reserved.