Vapor sampling of ERCs for environmental assessment in atmospheric and soil settings

The existence of explosive related chemicals (ERCs) near the soil-atmospheric and other surfaces depend on their fate and transport characteristics within the environmental settings. Consequently, detection of ERC in environmental matrices is influenced by conditions that affect their fate and transport. Experimental work to study the fate and transport behavior of ERCs relies on proper temporal and spatial sampling techniques. Because the low vapor pressure of these chemicals and their susceptibility to adsorption and degradation, vapor concentrations in environmental matrices are very low. Depending on the environmental conditions, the amount of samples that can be withdrawn for analysis is also limited. It is, therefore, necessary to develop sampling technologies that can provide quantitative measures of ERC concentrations in limited sampling environments. This paper presents experimental work conducted to develop a sampling technique to quantify DNT and TNT vapor concentrations of low vapor-pressure ERCs in environmental setting having limited sampling volumes and large sample numbers. Two potential vapor sampling techniques, Solid phase Microextraction (SPME) and Solid Phase Extraction (SPE), were developed and evaluated. SPME sampling techniques are excellent to quantify for DNT and TNT at very low concentrations. Its passive sampling capabilities meet the requirement for low-volume environmental sampling, but measured concentrations may be lagged in time. SPMEs' requirements for immediate analysis after sampling limit the technique for continuous vapor sampling. SPE showed to be a sensitive and reproducible technique to determine vapor concentrations of TNT and DNT in atmospheric and soil setting having limited sampling volumes and large sample numbers. Smallvolume (600mL) air samples provide measurements in the mgL -1 concentration range using isoamyl acetate and acetonitrile as the solvents. Small extraction volumes make this technique cost efficient and attractive. Issues with extraction inefficiencies, however, were observed and are being investigated.