Measuring the Kinetics of Neutral Pair Evaporation from Cluster Ions of Ionic Liquid in the Drift Region of a Differential Mobility Analyzer.

Singly charged clusters [CA]C or [CA]A of two salts [CA] are produced by electrospray ionization of alcohol solutions of the ionic liquids 1-ethyl-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate (EMI-FAP) and 1,2-dimethyl-3-propylimidazolium-methide (DMPI-Me). The rate of neutral pair evaporation into [CA] + [CA]C or [CA]A is studied in atmospheric pressure as a function of temperature for the positive trimer ion ( = 2) of DMPI-Me and the negative trimer ion of EMI-FAP. The trimer is separated from all other electrosprayed ions in a first differential mobility analyzer (DMA) and then transferred through a cooled tube to a second DMA whose drift gas is kept at a controlled temperature (25 °C < < 100 °C).