Sensitive Detection of Gas-Phase Glyoxal by Electron Attachment Reaction Ionization Mass Spectrometry

Abstract

Glyoxal (GLY) acts as a key contributor to tropospheric ozone production and secondary organic aerosol (SOA) formation on local to regional scales. The detection of GLY provides useful indicators of fast photochemistry occurring in the lower troposphere. The fast and sensitive detection of GLY is thus important, while traditional chemical ionization such as the proton-transfer reaction (PTR) is extremely limited by the poor detection limit and extensive fragmentation. To address these limitations, electron attachment reaction (EAR) ionization was applied to detect GLY. The generation of parent anions (GLY–) without fragmentation was observed, and cryogenic photoelectron imaging spectroscopy further characterized the structure of GLY–. The detection limit was estimated to be as low as (52 ± 1) pptv (parts per trillion by volume) with 1 min measurements. Other components in ambient air, such as water, carbon dioxide, and trace gases (acetone, propanal, etc.) have no effect on the detection of GLY. The EAR ionization is more promising than PTR ionization in detecting GLY. The detection of GLY in ambient air by the EAR ionization has been demonstrated.

Formaldehyde and glyoxal measurement deploying a selected ion flow tube mass spectrometer (SIFT-MS)

“…Quite recently, electron attachment reaction (EAR) ionization mass spectrometry has been used for real-time measurements of GL in ambient air. Nevertheless, this technique does not seem to be sensitive enough for other volatile organic compounds (VOCs; Lu et al, 2019). It should be noted that mass spectrometric techniques are widely applied in atmospheric science for three main reasons.…”

“…Alternatively, the monitoring of FM and GL is achieved using VOC-selective spectroscopic techniques such as Fourier transform infrared spectroscopy (FTIR; Catoire et al, 2012), differential optical absorption spectroscopy (DOAS; Coburn et al, 2014), tunable diode laser absorption spectrometer (TDLAS; Catoire et al, 2012), or incoherent broadband cavity-enhanced absorption spectrometer (IBBCEAS; Liu et al, 2019;Lu et al, 2019). FTIR spectroscopy is mostly used in lab experiments (Catoire et al, 2012) deployed in situ or in line configuration inside atmospheric simulation chambers or photoreactors (Wisthaler et al, 2008).…”

“…In addition, long path FTIR systems are not mobile, or are of limited mobility, and the selective detection of FM and GL is relatively difficult due to the complex IR pattern in the presence of other VOCs. Other VOC-selective spectroscopic tools, such as DOAS and IBBCEAS, are mostly used in outdoor field studies (Coburn et al, 2014;Lu et al, 2019). These are expensive and delicate systems that can achieve detection limits in the sub-ppb level.…”

“…These are expensive and delicate systems that can achieve detection limits in the sub-ppb level. However, these techniques require a high-volume sampling flow of several liters per minute (L min −1 ; Coburn et al, 2014;Lu et al, 2019). Thus, they are not commonly deployed in laboratory studies or indoor field measurements.…”