Corona Discharge and Field Electron Emission in Ambient Air Using a Sharp Metal Needle: Formation and Reactivity of CO3 -• and O2 -•.

CO3 -• and O2 -• are known to be strong oxidizing reagents in biological systems. CO3 -• in particular can cause serious damage to DNA and proteins by H• abstraction reactions. However, H• abstraction of CO3 -• in the gas phase has not yet been reported. In this work we report on gas-phase ion/molecule reactions of CO3 -• and O2 -• with various molecules. CO3 -• was generated by the corona discharge of an O2 reagent gas using a cylindrical tube ion source. O2 -• 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 CO3 -•, a decrease in signal intensities of CO3 -• accompanied by the simultaneous increase of that of HCO3 - 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. O2 -• abstracts H+ from acid molecules such as formic, acetic, trifluoroacetic, nitric and amino acids. Gas-phase CO3 -• may play a role as a strong oxidizing reagent as it does in the condensed phase. The major discharge product CO3 -• in addition to O2 -•, O3, and NO x • that are formed in ambient air may cause damage to biological systems.