Integrated Automated Analyzer for Monitoring of Explosives in Groundwater
NAVAL RESEARCH LAB WASHINGTON DC CHEMISTRY DIV
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The closure and remediation of former ammunition plants and military facilities requires accurate characterization of soil and groundwater contamination. Some of the pollutants found at these facilities are nitroaromatic and nitramine explosives and their biological and photolytic degradation products 1. It has been found that the distribution of contamination is often highly heterogeneous, requiring numerous samples and analyses for these sites to be adequately characterized 1. A number of different methods have been applied to the analysis of explosives, including gas 2, liquid 3-5, thin-layer chromatographies 6, Raman spectroscopy 7, electrochemical sensor 8, and immunoassay techniques 9. It would be highly advantageous to develop a field analyzer capable of reliable and cost-effective analysis of explosives in environmental samples. Groundwater in contaminated sites usually contains several related compounds and their degradation products 14 compounds in the U.S. Environmental Protection Agency EPA 8330 method. Therefore, simultaneous detection of these explosives in complex environmental matrixes by Raman spectroscopy, immunochemical sensors, or electrochemical sensors would be difficult and requires a chromatographic separation technique. The EPA specifies SW-846 Method 8330 for the trace analysis of explosive residues in water, soil, or sediment matrixes 10. Following sonication, extraction with acetonitrile, and preconcentration, analysis for 14 species is performed using high-performance liquid chromatography HPLC and ultraviolet UV absorption. Isocratic HPLC separations using commercially available C18 columns typically take over 30 minutes and are unable to separate the two aminodinitrotoluene isomers and two of the three dinitrotoluene isomers 11. To fully identify each of the 14 compounds, an additional HPLC run must be performed using a cyano column, leading to an increase in analysis time and sample handling complexity.
- Physical Chemistry
- Ammunition and Explosives
- Water Pollution and Control