A pulsed corona discharge switchable high resolution ion mobility spectrometer-mass spectrometer

Abstract

A pulsed corona discharge ionisation source, a candidate replacement for ⁶³Ni ionisation sources for ion mobility spectrometry, is described along with a new design of ion mobility spectrometer-mass spectrometer. Preliminary research on the characterisation of the reactant ion peaks associated with the use of this ionisation source was undertaken by assembling a pulsed corona discharge ionisation switchable high-resolution ion mobility spectrometer-mass spectrometer to enable the mobility spectra, atmospheric chemical ionisation mass spectra and selected-mass mobility spectra to be obtained. With ammonia doping at 2.39 mg m⁻³ in air and a water content of approximately 80 mg m⁻³ in the positive mode the observed response was attributable to the formation of [(H₂O)_nNH₄]⁺ and [(H₂O)_n(NH₃)NH₄]⁺ in the reaction region. The observed responses in the negative mode were more complex with evidence for the formation [(H₂O)_nO₂]⁻, [(H₂O)_nCO₃]⁻, [(H₂O)_nHCO₃]⁻, [(H₂O)_nCO₄]⁻ and [(H₂O)_nNO₃]⁻. The responses due to these species were clearly discernible in the resultant mobility spectra, with enough oxygen-based species formed to support analytically useful responses.