Importance of kinetics and thermodynamics to the electron-capture detector

Abstract

The kinetic model for the electron-capture detector (ECD) has been reviewed. Emphasis was placed on the agreement between thermodynamic and kinetic data obtained from the ECD and independent data obtained by other techniques. During the past five years, sufficient kinetic and thermodynamic data have been obtained to establish clearly the validity of the ECD model for non-dissociative electron capture and for exothermic dissociative electron attachment. In addition, new ECD data have been obtained for a kinetic mechanism of dissociative electron capture, which had been postulated but had not been demonstrated. This mechanism provides values for rate constants which have heretofore never been measured. All of the mechanisms have been illustrated by the use of Morse potential energy curves. A direct correspondence was shown to exist between the gas-phase mechanisms and mechanisms in solution observed with electrochemical techniques. As a result, fundamental kinetic and thermodynamic data can be obtained from the solution data. Correlations have been given which permit the calculation of electron affinities from half-wave reduction potentials.