Abstract
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 NOx• that are formed in ambient air may cause damage to biological systems.
