Mass spectrometric decomposition of [MNO3]+ cations, where M = Ca, Sr, Ba

ESI-CID-MS/MS spectra of [MNO3]+ ions (M stands for Ca, Sr, Ba), the simplest ionic species composed of a metal and a nitrate group, are discussed in detail. These ions decompose through the loss of an NO molecule (with the formation of the MO2+ fragment ion) and/or the loss of an NO2 molecule (with the formation of the MO+ fragment ion). The efficiencies of these processes strongly depend on the electrostatic attraction between the metal and the oxygen atoms of the nitrate group. For the [CaNO3]+ ion the loss of an NO molecule is the only decomposition observed, for the [SrNO3]+ ion both processes are observed and their efficiencies depend on the collision energy, and for [BaNO3]+ ion the loss of an NO2 molecule is the dominant process. Alkali earth metal cations are not prone to reduction (MII → MI), thus the formation of the M+ ion is a minor process.

Graphical abstractMass spectrometric decompositions of the [CaNO3]+, [SrNO3]+ and [BaNO3]+ ions consist of the loss of an NO molecule and/or the loss of an NO2 molecule. The efficiencies of these processes strongly depend on electrostatic attraction between the metal and oxygen atoms of the nitrate group.Figure optionsDownload full-size imageDownload as PowerPoint slide