Laboratory investigations of negative ion molecule reactions of formic andacetic acids: implications for atmospheric measurements by ion-molecule reaction mass spectrometry

Laboratory measurements of gas-phase ion-molecule reactions of several nega tive ion species with formic and acetic acid have been carried out. A flow reactor operating at a temperature of 293 +/- 3 K and total gas pressures o f either 3 or 9 hPa was used. The negative reagent ion species investigated included OH-, O-2(-), O-3(-), CO4-, CO3-, CO3-H2O, HCO3-H2O, NO3-, NO3-H2O , NO2-, and NO2-H2O. The reactions were found to proceed either via proton transfer or clustering. Our measurements of ion-molecule reactions of negat ive ions with gaseous formic and acetic acids provide a firm base for quant itative detection of these acidic trace gases in the atmosphere by negative ion ion-molecule reaction mass spectrometry. (Int J Mass Spectrom 181 (199 8) 31-41) (C) 1998 Elsevier Science B.V.