Corona Discharge and Field Electron Emission in Ambient Air Using a Sharp Metal Needle: Formation and Reactivity of CO and O

CO and O are known to be strong oxidizing reagents in biological systems. CO in particular can cause serious damage to DNA and proteins by H abstraction reactions. However, H abstraction of CO in the gas phase has not yet been reported. In this work we report on gas-phase ion/molecule reactions of CO and O with various molecules. CO was generated by the corona discharge of an O reagent gas using a cylindrical tube ion source. O 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 , a decrease in signal intensities of CO accompanied by the simultaneous increase of that of HCO was observed when organic compounds with H-C bond energies lower than ∼100 kcal mol such as -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 abstracts H from acid molecules such as formic, acetic, trifluoroacetic, nitric and amino acids. Gas-phase CO may play a role as a strong oxidizing reagent as it does in the condensed phase. The major discharge product CO in addition to O , O, and NO that are formed in ambient air may cause damage to biological systems.