Application of a co-polymeric solid phase extraction cartridge to residues containing nitro-organic explosives

Abstract

A validated solid phase extraction (SPE) cleanup procedure utilizing Bond Elut NEXUS co-polymeric cartridges has been applied to soil and swab samples containing pre- and post-blast residues of nitro-organic explosives. In addition, simulated samples were also processed by SPE to evaluate matrix rejection and interferences. The matrices were extracted with acetone, diluted with deionized water, and processed by SPE. The final extracts were then analyzed by gas chromatography with electron capture detection (GC/ECD) to screen for the compounds of interest, which included ethylene glycol dinitrate (EGDN), dimethyl dinitrobutane (DMDNB), 4-nitrotoluene (4-NT), nitroglycerin (NG), 2,4-dinitrotoluene (DNT), 2,4,6-trinitrotoluene (TNT), pentaerythritol tetra-nitrate (PETN), cyclotrimethylene trinitramine (RDX), 2,4,6-trinitrophenylmethylnitramine (tetryl), cyclotetra-methylene tetranitramine (HMX), erythritol tetranitrate (ETN), and cyclotrimethylene trinitrosoamine (R-salt). The expected explosives were detected in 97% of cases after processing through SPE and analysis by GC/ECD. Approximately one-third of the samples that screened positive by ECD were subjected to confirmation testing by gas or liquid chromatography/mass spectrometry (GC/MS or LC/MS). The results from these matrices were compared to results obtained by syringe filtration. SPE produced equal or better results than syringe filtration in both the ECD screening and MS confirmation tests, including the ability to detect higher signals for more explosives in the post-blast residue samples. The confirmation results also show that all of the expected explosives could be confirmed after processing by SPE, whereas only 83% of them were confirmed after syringe filtration. This study demonstrates the successful application of a validated method to the cleanup of organic explosive residues in complex matrices.