An investigation of the reactions of H3O+ and O2+ with NO, NO2, N2O and HNO2 in support of selected ion flow tube mass spectrometry

Abstract

A selected ion flow tube (SIFT) experimental investigation has been carried out of the reactions of H3O+, NO+ and O2+ with NO, NO2, N2O and HNO2, in order to obtain the essential kinetic data for the analyses of these compounds in air using selected ion flow tube mass spectrometry (SIFT-MS). These investigations show that NO+ ions do not react at a significant rate with any of these NOx compounds and that H3O+ ions react only with HNO2 (product ions H2NO2+ (75%) and NO+ (25%)). O2+ ions react with NO (product ion NO+), NO2 (product ion NO2+) and HNO2 (product ions NO+ (75%), NO2+ (25%)), but not with N2O. We conclude that both NO and NO2 can be accurately quantified in air using only O2+ precursor ions and SIFT-MS when HNO2 is not present. However, when HNO2 is present it invariably co-exists with both NO and NO2 and then both H3O+ and O2+ precursor ions are needed to determine the partial pressures of NO, NO2 and HNO2 in the air mixture. We also conclude that currently N2O cannot be analysed in air using SIFT-MS.

Intercomparison of nitrous acid (HONO) measurement techniques in a megacity (Beijing)

“…The bimolecular reaction of H 3 O + and nitrous acid produces the product ions H 2 NO 2 (m/z 48, 67 %) and NO + (m/z 30, 33 %). The rate constant (k) of this exothermic proton transfer reaction is calculated to be 2.7 × 10 −9 cm 3 s −1 with respect to hydronium (H 3 O + ) and 2.2 × 10 −9 cm 3 s −1 with respect to hydronium mono-hydrate (H 3 O • H 2 O) + (Spanel and Smith, 2000). Nitrous acid does not undergo proton transfer with hydronium di-hydrate (H 3 O • H 2 O 2 ) + and tri-hydrate (H 3 O • H 2 O 3 ) + in SIFT-MS. Nitrous acid mixing ratios herein were determined using the branching-ratiocorrected protonated product ion m/z 48 intensity normalized to both H 3 O + and H 3 O•H 2 O with their respective k values (Taipale et al, 2008).…”

“…Measurements were performed as part of the Air Pollution and Human Health in a Chinese megacity (APHH-Beijing, http://www.aphh.org.uk, last access: 26 November 2019) programme and of the "An integrated study of air pollution processes in Beijing" (AIRPRO) project, which aimed to understand atmospheric processes affecting air pollution in Beijing. An overview of the APHH-Beijing project is provided in Shi et al (2019). Measurements were performed at the Chinese Academy of Sciences' Institute of Atmospheric Physics (IAP) tower campus, an urban site located near the 4th ring road in the northern suburbs of Beijing.…”

Proton Transfer Reactions from N2H+ and ArH+ to Small Molecules

“…NO 2 + + N 2 leads to the peroxy isomer NOO + . [13] It was shown experimentally that H 3 O + is unreactive with NO 2 , i. e. standard PTRMS with H 3 O + does not allow for the detection of NO 2 , [14] in line with the relatively low PA of 6.13 eV. [15] The reaction of H 3 + with NO 2 , however, leads to formation of NO + with release of OH * and H 2 , as shown by Burt et al [16] Methane as the smallest hydrocarbon has quite a low PA of 5.63 eV, and thus is not protonated by H 3 O + .…”