MASS-SPECTRA OF 2,4-DINITROIMIDAZOLE AND ITS ISOTOPOMERS USING SIMULTANEOUS THERMOGRAVIMETRIC MODULATED BEAM MASS-SPECTROMETRY

The ET mass spectrum of 2,4-dinitroimidazole (2,4-DNI) was studied at 20 and 70 eV ionizing energy using simultaneous thermogravimetric modu lated beam mass spectrometry, Product ion formulas and their origin fr om within the 2,4-DNI molecule were identified from the evaluation of perdeuterated and various N-15-labeled 2,4-DNI mass spectra, The molec ular ion (M(+.); m/z 158) is present in all the spectra and the NO+ io n (m/z 30) is the major primary product ion, The base peak is formed b y the M(.+) ion at 20 eV and by the NO+ ion at 70 eV. Other primary pr oduct ions are NO2+ (m/z 46), CH2N+ (m/z 28) and CHN2O2+ (m/z 73), Fra gmentation pathways are postulated based on the identity and relative abundance of the product ions, and on the change in relative abundance of the ions as a function of ionizing energy. Comparisons of the 70 e V mass spectra of 2,4-DNI, 4,5-dinitroimidazole (4,5-DNI) and 1,4-dini troimidazole (1,4-DNI) show that the fragment product ions have the sa me m/z values in the three spectra but differ in their relative abunda nce and in the ion that forms the base peak. The base peak for 2,4-DNI and 4,5-DNI is formed by the ion at m/z 30 (NO+) and for 1,4-DNI, the ion at m/z 46 (NO2+). This difference is probably due to the nitramin e functionality of 1,4-DNI.