Corona Discharge Ionization Source for a Planar High-Field Asymmetric Waveform Ion Mobility Spectrometer

Abstract

A corona discharge (CD) ionization source was prepared for a planar high-field asymmetric waveform ion mobility spectrometer (FAIMS). The effects of discharge current and discharge distance on ionization efficiency were investigated; and the electric field dependence of the ion injection in the reaction region was studied. The results showed that the discharge current of CD source had good linearity with the intensity of reactant ion peak (RIP), and the RIP intensity increased to a stable level at the discharge distance of >5 mm. An injection electrode was introduced to improve the ionization efficiency. A square-wave voltage applied to the electrode was found to provide optimal performance of ion injection and utilization. The operating parameters of the CD-FAIMS were optimized to achieve trace level detection of dimethyl methylphosphonate (DMMP) sample. The detection limit for DMMP was 0.5 µg/m3.