Chemical ionization quadrupole mass spectrometer with an electrical discharge ion source for atmospheric trace gas measurement

Abstract

Abstract. We present a chemical ionization quadrupole mass spectrometer (CI-QMS) with a radio-frequency (RF) discharge ion source through N2∕CH3I as a source of primary ions. In addition to the expected detection of PAN, peracetic acid (PAA) and ClNO2 through well-established ion–molecule reactions with I− and its water cluster, the instrument is also sensitive to SO2, HCl and acetic acid (CH3C(O)OH) through additional ion chemistry unique to our ion source. We present ionization schemes for detection of SO2, HCl and acetic acid along with illustrative datasets from three different field campaigns underlining the potential of the CI-QMS with an RF discharge ion source as an alternative to 210Po. The additional sensitivity to SO2 and HCl makes the CI-QMS suitable for investigating the role of sulfur and chlorine chemistry in the polluted marine and coastal boundary layer.

Shipborne measurements of ClNO<sub>2</sub> in the Mediterranean Sea and around the Arabian Peninsula during summer

“…Nitryl chloride (ClNO 2 ), hydrogen chloride (HCl), and sulfur dioxide (SO 2 ) were detected with a chemical ionization quadrupole mass spectrometer (CI-QMS) using an electrical, radio-frequency (RF) discharge ion source. The instrument and the ion-molecule reactions involved in the detection of the above-mentioned trace gases are described in detail by Eger et al (2019). Briefly, ClNO 2 was monitored as I•ClNO − 2 at a mass-to-charge ratio (m/z) of 208 and 210 subsequent to the reaction of ClNO 2 with I − (McNeill et al, 2006;Osthoff et al, 2008;Thornton et al, 2010).…”

“…HCl was observed as I(CN)Cl − (m/z 188 and 190) (Eger et al, 2019) with a sensitivity of 0.17 Hz pptv −1 per 10 6 Hz of I − at m/z 188 (and 0.05 Hz pptv −1 at m/z 190), a detection limit of 98 pptv, and a total measurement uncertainty of 20 % ± 72 pptv. As m/z 190 suffers from known interferences (e.g.…”

“…The formation of ClNO 2 can have a significant impact on regional NO x cycling and radical chemistry, especially in the polluted coastal and marine boundary layer (Simon et al, 2009;Riedel et al, 2014;Sarwar et al, 2014). The Cl atoms formed in Reaction (R2) can enhance oxidation rates of several volatile organic compounds (VOCs), especially during early morning hours (Phillips et al, 2012;Riedel et al, 2012a;Young et al, 2012) thus contributing to photochemical ozone production (Simon et al, 2009;Riedel et al, 2014;Sarwar et al, 2014;Faxon et al, 2015;Wang et al, 2019).…”

“…Other studies included coastal sites in Canada (Osthoff et al, 2018) and coastal/urban sites in the United Kingdom (Bannan et al, 2015(Bannan et al, , 2017Priestley et al, 2018;Sommariva et al, 2018). Whereas ClNO 2 was initially believed to play a significant role only in areas with marine influence (Behnke et al, 1997;Keene et al, 1999), midcontinental measurements in the US (Thornton et al, 2010;Riedel et al, 2013;Faxon et al, 2015) revealed the im-portance of anthropogenic sources (e.g. industrial combustion, cooling towers, natural gas extraction, and suspension of road salt) and sea salt chloride transported inland.…”

Pyruvic acid in the boreal forest: gas-phase mixing ratios and impact on radical chemistry

“…They influence the acidity of aerosols and cloud droplets and are involved in the formation of secondary organic aerosols (SOAs), thereby impacting air quality and climate (Kanakidou et al, 2005;Hallquist et al, 2009). Pyruvic acid, CH 3 C(O)C(O)OH, the simplest α-keto acid, is omnipresent in plants, where it is central to the metabolism of isoprene, monoterpenes and sesquiterpenes (Eisenreich et al, 2001;Magel et al, 2006;Jardine et al, 2010), and is also found in tropospheric air, especially in the boundary layer of vegetated regions (see Sect. 1.3).…”