Estimation of effective ion temperatures in a quadrupole ion trap

A modified Finnigan LCQ quadrupole ion trap has been used;ro determine the equilibrium constant of the complexation reaction of thiophenolate with 2,2,2-trifluoroethanol. The process is particularly useful as a thermometer reaction because it has an exceptionally large temperature dependence. Using Literature values for the thermochemistry, an effective ion temperature of 310 +/- 20 K is indicated for the ion trap. This value is much lower than some earlier estimates for ion traps, but is consistent with a recent theoretical analysis and some previous interpretations of experimental data. The results suggest that quadrupole ion traps are suitable for studying gas phase reactions under nearly thermal conditions. (C) 1998 American Society for Mass Spectrometry.