Probing the OH Oxidation of Pinonic Acid at the Air–Water Interface Using Field-Induced Droplet Ionization Mass Spectrometry (FIDI-MS)

Abstract

Gas and aqueous phases are essential media for atmospheric chemistry and aerosol formation. Numerous studies have focused on aqueous-phase reactions as well as coupled gas/aqueous-phase mass transport and reaction. Few studies have directly addressed processes occurring at the air-water interface, especially involving surface-active compounds. We report here the application of field-induced droplet ionization mass spectrometry (FIDI-MS) to chemical reactions occurring at the atmospheric air-water interface. We determine the air-water interfacial OH radical reaction rate constants for sodium dodecyl sulfate (SDS), a common surfactant, and pinonic acid (PA), a surface-active species and proxy for biogenic atmospheric oxidation products, as 2.87 × 10 and 9.38 × 10 cm molec s, respectively. In support of the experimental data, a comprehensive gas-surface-aqueous multiphase transport and reaction model of general applicability to atmospheric interfacial processes is developed. Through application of the model, PA is shown to be oxidized exclusively at the air-water interface of droplets with a diameter of 5 μm under typical ambient OH levels. In the absence of interfacial reaction, aqueous- rather than gas-phase oxidation is the major PA sink. We demonstrate the critical importance of air-water interfacial chemistry in determining the fate of surface-active species.

Effect of inorganic-to-organic mass ratio on the heterogeneous OH reaction rates of erythritol: implications for atmospheric chemical stability of 2-methyltetrols

“…As shown in Table 1, assuming a 24 h averaged OH concentration of 1.5 × 10 6 molecule cm −3 (Mao et al, 2009), the τ of pure erythritol particles is estimated to be 14.7 ± 0.33 d. The timescales are slightly longer than those of other important particle removal processes, such as dry and wet deposition (∼ 5-12 d) with the similar particle size (200 nm) (Kanakidou et al, 2005). A similar result has been reported in the literature.…”

Ambient Ionization Mass Spectrometry: Recent Developments and Applications

“…Studies employing ESI have been widely performed and have provided evidence on the accelerated reaction rates occurring in the ESI microdroplets. , In a similar fashion, ambient ionization MS techniques have been used as platforms to study acceleration of reactions in microdroplets as well as to explore reaction mechanisms in bulk solutions . Acceleration of many reactions including degradation of the antibiotic Erythromycin A, tert -butyloxycarbonyl deprotection of amines, and oxidation of oleic and pinonic acids at air–water interfaces in levitated droplets have been investigated using DART, touch spray, and field-induced droplet ionization, respectively. For example, reactive LAESI was used to monitor the click reaction between various tetrazine compounds and BCN-amine .…”

Night-Time Oxidation of a Monolayer Model for the Air–Water Interface of Marine Aerosols—A Study by Simultaneous Neutron Reflectometry and in Situ Infra-Red Reflection Absorption Spectroscopy (IRRAS)

“…However, saturated surfactants have recently been shown to be of particular atmospheric importance [35], therefore processes that can attack saturated organic compounds are of particular interest. Understanding the night-time atmospheric ageing by NO 3 •, in addition to the chemistry of the dominant day-time oxidant OH• (e.g., [36]) and photochemical reactions that have recently received lots of attention (e.g., [37]) is therefore an important focus of current research. It is thus essential to investigate the NO 3 • chemistry at the air-water interface given the scarcity of previous studies [38,39].…”