The activity coefficients at infinite dilution, gamma(13)(infinity), for both polar and nonpolar solutes in an ionic liquid, 1-hexyl-3-methylimidazolium tetrafluoroborate ([HMIM+][BF4-]), have been determined by gas-liquid chromatography at T = (298.15 K and 323.15 K). This work is part of our research focus on ionic liquids. The selectivity values have been calculated at T = 298.15 K, and the results indicate that the ionic liquid, [HMIM+] [BF4-], should be a good solvent for separation of benzene and alkanes. The partial molar excess enthalpy values at infinite dilution have also been determined at T = 298.15 K and have been discussed in terms of intermolecular interactions. The results have been discussed in terms of measurements of gamma(13)(infinity), using other ionic liquids, taken from the recent literature.