Mass spectrometric decomposition of [Mn+(NO3−)n+1]− anions originating from metal nitrates M(NO3)n

• ESI-CID-MS/MS spectra of [Mn+(NO3−)n+1]− anions (M stands for a metal) are discussed.
• Loss of NO2 molecules may lead to the oxidation of metal to its highest oxidation state.
• Oxygen oxidation may lead to the formation of dioxygen or peroxide molecules.
• If charge density on the metal is low the only decomposition may be formation of NO3−.
• If metal is prone to be reduced, the extensive loss of NO3
• radical occurs.

ESI-CID-MS/MS spectra of [Mn+(NO3−)n+1]− anions (M stands for a transition metal, for a metal from group 2 or 13 of the periodic table), thus composed only of a metal and nitrate groups, are discussed in details. Decomposition of [Mn+(NO3−)n+1]− ions consists in (i) formation of fragment ion NO3−, (ii) loss of NO3
• radical, (iii) loss of NO2, sometimes also NO, molecule(s). Process (iii) is the most interesting, as for example it may lead to the formation of fragment ions containing metal at the highest, possible oxidation state (e.g. [Mn(NO3)3]- → MnO4− + 2NO2 + NO, anion MnO4− contains MnVII) or to the formation of oxygen molecule (e.g. [Ni(NO3)3]− → [NiNO3]− + 2NO2 + O2). Process (i) is trivial and it is the dominant, sometimes the only, decomposition pathway of anions [Mn+(NO3−)n+1]− which contain metal of low charge density. Process (ii) is the decomposition pathway characteristic of anions [Mn+(NO3−)n+1]− which contain metal prone to be reduced (e.g. [Tl(NO3)4]− → [Tl(NO3)2]− + 2NO3−).

CID-MS/MS spectrum of anion [Mn(NO3)3].Figure optionsDownload high-quality image (149 K)Download as PowerPoint slide