Production and utilization of CO 3− produced by a corona discharge in air for atmospheric pressure chemical ionization

Abstract

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 CO 3 − or N 2O 2 −. The identity of this ion is important as it is a key to the ionization of analytes. It was determined here to be CO 3 − through the use of 18O labeled oxygen. Further confirmation was provided through MS/MS studies. The ionization of nitroglycerine (NG) with CO 3 − produced the adduct NG·CO 3 −. This was compared to ionization with NO 3 − 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 CO 3 − has a relatively high electron affinity similar to that of nitrate.