REACTIONS OF H3O- IONS WITH SOME ORGANIC-MOLECULES - APPLICATIONS TO TRACE GAS-ANALYSIS IN AIR( AND OH)

The reactions of H3O+ and OH- ions with several hydrocarbons and sever al oxygen-bearing organic molecules, MH, have been studied using a sel ected-ion flow tube (SIFT) and a flowing afterglow (FA) apparatus at 3 00 K. Most of the reactions are fast, proceeding via proton transfer p roducing a single product, viz. MH(2)(+) for the H3O+ reactions and M( -) or the OH- reactions, but in seven of the twenty-eight reactions tw o products are observed. In the reaction of H3O+ with trans-2-hexenal only one product is observed whereas in its reaction with the cis-3-he xenal isomer two products are observed. The significance of these obse rvations and the value of the data obtained in this study to trace gas analysis in atmospheric air and on human breath using H3O+ and OH- as chemical ionisation agents is discussed. A by-product of these studie s is an estimation of the proton affinity of methylcyclohexane.