Modified kinetic model of the electron-capture detector: Molecular electron affinities and electron collection modes

The kinetic model for electron-capture detection (ECD) has recently been expanded to include excited states. Multiple electron affinities for C 6F 6, anthracene and tetracene have been reported in the literature. The temperature dependence of the ECD response is calculated using these values and the expanded two state model. Activation energies and pre-exponential terms for kinetic rate constants are determined. The pre-exponential terms for thermal electron attachment are compared with the maximum value calculated from the DeBroglie wavelength of the electron and the probability for stabilization. Temperature data from different methods of electron collection are compared. A general procedure for the determination of electron affinities from ECD data is presented. The following ECD electron affinities are reported: C 6Cl 6, 1.17±0.02 and 0.71±0.02; C 6F 5Cl, 0.96±0.03 and 0.82±0.02; C 6F 5NO 2, 1.52±0.02; C 6H 5NO 2, 1.00±0.01 and m-hydroxyacetophenone, 0.74±0.02 (all values in electron volts, eV).