<p>We present a Chemical Ionisation Quadrupole Mass Spectrometer (CI-QMS) with radio-frequency (RF) discharge ion source through N<sub>2</sub>/CH<sub>3</sub>I as source of primary ions. In addition to the expected detection of PAN, peracetic acid and ClNO<sub>2</sub> through well-established ion-molecule-reactions with I- and its water cluster, the instrument is also sensitive to SO<sub>2</sub>, HCl and acetic acid (CH<sub>3</sub>C(O)OH) through additional ion chemistry unique for our ion source. We present ionisation schemes for detection of SO<sub>2</sub>, HCl and acetic acid along with illustrative data sets from three different field campaigns underlining the potential of the CI-QMS with an RF discharge ion source as an alternative to <sup>210</sup>Po. The additional sensitivity to SO<sub>2</sub> and HCl makes the CI-QMS suitable for investigating the role of sulphur and chlorine chemistry in the polluted marine and coastal boundary layer.</p>