Selected Ion Flow Tube – Mass Spectrometry (SIFT-MS) study of the reactions of H3O+, NO+ and O2+ with a range of oxygenated volatile organic carbons (OVOCs)

Selected Ion Flow Tube-Mass Spectrometry (SIFT-MS) uses soft chemical ionisation, typically by H3O+, NO+ and O2+, to analyse trace gases in real time at mixing ratios down low parts per trillion volume (pptv) has recently been demonstrated as an effective method for monitoring volatile organic compounds (VOCs) the atmosphere. SIFT-MS analysis requires accurate rate coefficient product ion branching ratio data allow calculations without need calibration standards. Most constant have measured using helium carrier gas. Here we report constants of a number oxygenated (OVOCs) alongside benzene O2+ reagent ions nitrogen gas, permeation tube source certified gas standard introduce known concentrations into SIFT-MS. This includes first reported literature nonanal We found that most were similar those helium. However, ketones 1.2–5 times lower than observe higher fragmentation due changes made lens voltages instrument order tune sensitivity, altering energies. also show impact increasing flow temperature voltage on sensitivity ionisation benzene, butanone butanal under both dry humid conditions. Some compound library entries are from historic instruments lacked heated tube, therefore suffered water clustering current commercial models. reduces amount adduct formation thereby simplifying concentration determination. These results demonstrate ensure used acquired same conditions experiment being performed.