Characterization of Explosives and Associated Residues in Environmental and Forensic Media

The ECMS group has performed a number of studies involving ultra-high sensitivity detection and quantification of explosives and explosive residues in environmental matrices. These have involved sea water, compositing bioreactors, digestive gases of bees, and blast debris. Interest in these matrices arise from, respectively, potential toxicity to marine life, composting and bioreactors offering less-costly alternatives to incineration of explosive contaminated soil, use of insects as dispersed sampling units, and forensic applications. For these approaches, a number of new sampling and analysis methods have been developed. For the compositing studies, mixed-mode HPLC on a C18-anion exchange column provided good resolution and quantization of all the explosives and their known microbial metabolites and environmental transformation products. Bacterial mutagenicity on two Salmonella strains and aquatic toxicity to Ceriodaphnia dubia of the pure explosives, their metabolites and samples of the composts and slurry bioreactor products were investigated. Both processes effectively reduced explosives concentrations and toxicity.

Negative ion chemical ionization based GC/MS analysis has proved to be a very useful tool. With the support of several sponsors, the methodology was developed at ORNL by Mike Sigman (now with the Chemistry Department of the University of Central Florida), Jan Ma (now with Fluor Hanford) and Ralph Ilgner.

The key to any analytical methodology, of course, is getting the tiny amounts of explosives to the analysis system. We have employed everything from Teflon wipes for solids, Solid Phase Micro-Extraction (SPME) fibers for aqueous solutions, and multi-sorbent air sampling traps for airborne species. Thermal desorption of these sampling media maximizes the sensitivity of the analysis. For example, the collection of unexploded ordinance (UXO)-related species using an SPME fiber followed by negative ion chemical ionization gas chromatography/ion trap mass spectrometry (GC/ITMS-NICI) frequently proved to be the easiest to perform while simultaneously achieving comparable sensitivity and superior recoveries compared to the SPE/HPLC-based method.

For more information, contact Ralph Ilgner or Wayne Griest.