Characterization of ammonium nitrate by electrospray ionization tandem mass spectrometry

Mass spectra of ammonium nitrate were recorded in both positive‐ and negative‐ion mode by electrospray ionization mass spectrometry (ESI‐MS) and electrospray ionization tandem mass spectrometry with collision‐induced dissociation (ESI‐MS/MS‐CID). Characterization of ammonium nitrate by a series of typical cluster ions was further confirmed by using isotopically labeled ammonium nitrate (ammonium‐ 15 N, nitrate‐ 15 N, nitrate‐ 18 O) and deuterated water. It was found that, at heated capillary temperatures in the range 55–150 °C, in the positive‐ion mode, cluster ions of the type [(NH 4 NO 3 ) n NH 4 ] + (n = 1–3) were dominant in the mass spectrum, which enables the characterization and identification of the integral ammonium nitrate molecule.