Production and utilization of CO3− produced by a corona discharge in air for atmospheric pressure chemical ionization

Atmospheric pressure chemical ionization is a multistep ionization process used in mass spectrometry and ion mobility spectrometry. The formation of product ions depends upon interactions with the analyte and the reactant ion species formed in the ionization source. The predominant reactant ion observed in a point-to-plane corona discharge in air occurs at m/z 60. There have been multiple references in the literature to the identity of this ion with some disagreement. It was postulated to be either CO3− or N2O2−. The identity of this ion is important as it is a key to the ionization of analytes. It was determined here to be CO3− through the use of 18O labeled oxygen. Further confirmation was provided through MS/MS studies. The ionization of nitroglycerine (NG) with CO3− produced the adduct NG·CO3−. This was compared to ionization with NO3− and Cl− reactant ions that also formed adducts with NG. The fragmentation patterns of these three adducts provides insight into the charge distribution and indicates that CO3− has a relatively high electron affinity similar to that of nitrate.

The predominant ion in air occurring at 60 amu was shown to be CO3−. The use of 18O labeled oxygen produced an ion at 62 amu, C16O218O3−.Figure optionsDownload high-quality image (46 K)Download as PowerPoint slideResearch highlights▶ CO3− is the most prevalent anion produced in a point-to-plane corona discharge in air. ▶ The identity of CO3− was confirmed using 18O2 and was likely generated from the interactions between O3− and CO2. ▶ Nitroglycerine forms an adduct with CO3−. ▶ The fragmentation of this adduct yields CO3− and not NO3− indicating a relatively high electron affinity of CO3−.