Characterization of cyclotrimethylenetrinitramine (RDX) by N,H isotope analyses with pyrolysis–atmospheric pressure ionization tandem mass spectrometry

Pyrolysis-atmospheric pressure chemical ionization was used to study the thermal decomposition of the energetic material cyclotrimethylenetrinitramine (RDX) and characterization of the individual molecular ion products was accomplished by tandem mass spectrometry. The analysis was aided with pyrolysis mass spectra of the (¹⁵N)- and perdeuterated RDX isotopes, and molecular formulae were derived for the m/z 46, 60, 74, 75, 85 and 98 molecular ions in the RDX pyrolysis mass spectrum. Equivalent fragments between the daughter ion mass spectra of the unlabeled and labeled RDX were determined in order to define a structure for each pyrolysis feature. Daughter ion mass spectra of pure reference compounds confirmed the identity of five of the six molecular ions. Perdeuterated RDX analyses provided evidence that m/z 74 and 75 are N,N-dimethylformamide and N-nitrosodimethylamine, respectively; m/z 46, 60 and 85 were identified as the protonated forms of formamide, N-methylformamide and dimethylaminoacetonitrile, respectively.