Detection limits for GC/MS analysis of organic explosives

Method detection limits are determined and compared for analysis of liquid injections of organic explosives and related compounds by gas chromatography-mass spectroscopy utilizing electron impact (EI), negative ion chemical ionization (NICI), and positive ion chemical ionization (PICI) detection methods. Detection limits were rigorously determined for a series of dinitrotoluenes, trinitrotoluene, two nitroester explosives, and one nitramine explosive. The detection limits are lower by NICI than by EI or PICI for all explosives examined, with the exception of RDX. The lowest detection limit for RDX was achieved in the PICI ionization mode. Judicious choice of the appropriate ionization mode can enhance selectivity and significantly lower detection limits. Major ions are reported for each analyte in EI, PICI, and NICI detection modes.