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

• Main Authors: P. G. Eger, F. Helleis, G. Schuster, G. J. Phillips, J. Lelieveld, J. N. Crowley
• Format: Article
• Language: English
• Published: Copernicus Publications 2019-03-01
• Series: Atmospheric Measurement Techniques
• Online Access: https://www.atmos-meas-tech.net/12/1935/2019/amt-12-1935-2019.pdf

<p>We present a chemical ionization quadrupole mass spectrometer (CI-QMS) with a radio-frequency (RF) discharge ion source through <span class="inline-formula">N₂∕CH₃I</span> as a source of primary ions. In addition to the expected detection of PAN, peracetic acid (PAA) and <span class="inline-formula">ClNO₂</span> through well-established ion–molecule reactions with <span class="inline-formula">I⁻</span> and its water cluster, the instrument is also sensitive to <span class="inline-formula">SO₂</span>, HCl and acetic acid (<span class="inline-formula">CH₃C(O)OH</span>) through additional ion chemistry unique to our ion source. We present ionization schemes for detection of <span class="inline-formula">SO₂</span>, 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 <span class="inline-formula">²¹⁰Po</span>. The additional sensitivity to <span class="inline-formula">SO₂</span> and HCl makes the CI-QMS suitable for investigating the role of sulfur and chlorine chemistry in the polluted marine and coastal boundary layer.</p>