Mass-spectrometric studies of kinetic characteristics of codeine molecule thermodesorption by non-stationary surface ionization method.

The adsorption and surface ionization of codeine molecules С₁₈H₂₁O₃N (m/z 299) on the surface of oxidized tungsten have been studied by a non-stationary method of voltage modulation under the same experimental conditions with a high-vacuum mass-spectrometric setup using a "black chamber" all walls of which are cooled with liquid nitrogen. For the codeine molecule dissociation with the $(C-C_1{)}_{\beta }$ bond breaking and formation of ionizable radicals, the rate constants K⁺ and K⁰, the activation energy Е⁺ and Е⁰ of thermodesorption, and the pre-exponential factors in the continuity equation for the radicals C₉H₇N⁺CH₃ (m/z 144) have been defined by surface ionization on the surface of oxidized tungsten W_xO_y. The results of determining the surface ionization coefficient and estimates of the ionization potentials of these radicals have been presented.