Corona Discharge and Field Electron Emission in Ambient Air Using a Sharp Metal Needle: Formation and Reactivity of CO(3)(−•) and O(2)(−•)

CO(3)(−•) and O(2)(−•) are known to be strong oxidizing reagents in biological systems. CO(3)(−•) in particular can cause serious damage to DNA and proteins by H(•) abstraction reactions. However, H(•) abstraction of CO(3)(−•) in the gas phase has not yet been reported. In this work we report on gas-phase ion/molecule reactions of CO(3)(−•) and O(2)(−•) with various molecules. CO(3)(−•) was generated by the corona discharge of an O(2) reagent gas using a cylindrical tube ion source. O(2)(−•) was generated by the application of a 15 kHz high frequency voltage to a sharp needle in ambient air at the threshold voltage for the appearance of an ion signal. In the reactions of CO(3)(−•), a decrease in signal intensities of CO(3)(−•) accompanied by the simultaneous increase of that of HCO(3)(−) was observed when organic compounds with H–C bond energies lower than ∼100 kcal mol(−1) such as n-hexane, cyclohexane, methanol, ethanol, 1-propanol, 2-propanol, and toluene were introduced into the ion source. This clearly indicates the occurrence of H(•) abstraction. O(2)(−•) abstracts H(+) from acid molecules such as formic, acetic, trifluoroacetic, nitric and amino acids. Gas-phase CO(3)(−•) may play a role as a strong oxidizing reagent as it does in the condensed phase. The major discharge product CO(3)(−•) in addition to O(2)(−•), O(3), and NO(x)(•) that are formed in ambient air may cause damage to biological systems.