Negative- and positive-ion chemical ionization mass spectra of aromatic amines: Surface-assisted reactions involving oxygen

✍ Scribed by Elizabeth A. Stemmler; Michelle V. Buchanan

• Publisher: John Wiley and Sons
• Year: 1993
• Tongue: English
• Weight: 844 KB
• Volume: 28
• Category: Article
• ISSN: 1076-5174
• DOI: 10.1002/oms.1210280905

✦ Synopsis

The 0,-N, and 0,-Ar negative-ion chemical ionization mass spectra of aromatic amines show a series of unusual ions dominated by an addition appearing at [ M + 141-'. Other ions are observed a t IM -121 -', [ M + Sj-., [ M + 121-', [ M + 28]-' and [M + 30]-'. Ion formation was studied using a quadrupole instrument equipped with a conventional chemical ionization source and a Fourier transform ion cyclotron resonance (FTICR) mass spectrometer. These studies, which included the examination of ion chromatograms, measurement of positive-ion chemical ionization mass spectra, variation of ion source temperature and pressure and experiments with '*O,, indicate that the [ M + 141 -. ion is formed by the electron-capture ionization of analytes altered by surfaceassisted reactions involving oxygen. This conversion is also observed under low-pressure conditions following source pretreatment with 0,. Experiments with I "Nlaniline, [ 2,3,4,5,6-*H,] aniline and [ '3C,]aniline show that the [M + 141-' ion corresponds to [ M + 0 -2H]-', resulting from conversion of the amino group to a nitroso group. Additional ions in the spectra of aromatic amines also result from surface-assisted oxidation reactions, including oxidation of the amino group to a nitro group, oxidation and cleavage of the aromatic ring and, at higher analyte concentrations, intermolecular oxidation reactions.