Gas chromatography positive chemical ionization and tandem mass spectrometry for the analysis of organic high explosives

Talanta. 2005 Aug 15;67(2):430-6. doi: 10.1016/j.talanta.2005.01.035.


The characteristic ions or the parent ion resulting from ionization can be isolated in an ion trap and subjected to further fragmentation during a gas chromatography-tandem mass spectrometry (GC/MS/MS) experiment. This approach can improve the selectivity and sensitivity of explosive compounds over gas chromatography-mass spectrometry (GC/MS) by improving the differentiation of the target compounds from interfering and co-eluting compounds and reducing the background noise within an explosive debris sample. The optimization of the operating parameters for GC/MS and GC/MS/MS experiments with an ion trap mass spectrometer were conducted using a mixture of explosive compounds and 3,4-dinitrotoluene as an internal standard. The level of detection (LOD) and limit of quantitation (LOQ) for these compounds was determined by GC/MS with electron ionization, GC/MS with positive chemical ionization, and GC/MS/MS with positive chemical ionization. The LOD range was found to be 3.6pg for 2,4-dinitrotoluene to 2.23ng for hexahydro-1,3,5-trinitro-s-triazine (RDX) using GC/EI/MS; 0.4pg for 2,4-dinitroltoluene to 19.0pg for 1,3,5-trinitrobenzene using GC/PCI/MS; and 0.5pg for 4-nitrotoluene to 41.4pg for RDX using GC/PCI/MS/MS. The LOD results for GC/PCI/MS and for GC/PCI/MS/MS are very similar for most of the compounds except the GC/PCI/MS LOD results are lower for RDX and 1,3-dinitrobenzene while the GC/PCI/MS/MS LOD results are lower for 1,3,5-trinitrobenzene. The GC/PCI/MS/MS method offers improved selectivity when analyzing real world samples containing interfering products and matrix noise thereby improving sensitivity for complex samples.