Vaporisation of an ionic liquid near room temperature

The temperature at which the vapour phase of the ionic liquids (ILs) 1-ethyl-3-methylimidazolium bis[(trifluoromethane)sulfonyl]imide, [C(2)C(1)Im][Tf2N], and 1-ethyl-3-methylimidazolium ethylsulfate, [C(2)C(1)Im][EtOSO3], can be detected was investigated using line-of-sight mass spectrometry (LOSMS). By optimising the detection system used in previous experiments, the lowest temperature for which vapour was detected for [C(2)C(1)Im][Tf2N] was similar to 340 K, whereas for [C(2)C(1)Im][EtOSO3] it was similar to 390 K. Initial investigations also show that the temperature at which measurements are made affects the enthalpy of vaporisation at 298 K, Delta H-vap(298). The reasons for these differences in Delta H-vap(298) with respect to temperature are discussed. The vapour pressure of both ILs is estimated at far lower temperatures than previously achieved and extrapolations to room temperature are given.