A miniaturized field-portable immunosensor (FAST 2000) was field tested at former military munitions sites for the detection and quantitation of TNT and RDX in groundwater. Developed by the Naval Research Laboratory (NRL) and engineered by Research International, Inc. (Woodinville, WA), the immunosensor performed on-site analysis of contaminated groundwater at three military bases identified by the U.S. Environmental Protection Agency (EPA) as priority Superfund cleanup sites. The locations were Naval Submarine Base, SUBASE Bangor, Bangor, WA; Umatilla Army Depot Activity, Umatilla, OR; and Naval Surface Weapons Center, Crane, IN. The immunosensor uses an antibody as the recognition element for the explosive molecule in a displacement assay format. Detection of the explosive molecule contained in groundwater is confirmed by an increase in fluorescence over background from the displaced cyanine-labeled explosive analogue. At each site, groundwater samples containing unknown concentrations of explosives were collected from monitoring wells and analyzed on-site by the portable immunosensor with no sample pretreatment or concentration. Groundwater samples were split and shipped to an independent certified U.S. EPA laboratory for analysis using SW-846 Method 8330 (HPLC). Statistical analysis based on linear regression curves comparing the immunosensor and the HPLC method showed good correlation, although site-dependent problems were encountered with some samples. The immunosensor required small sample volumes (150 μL/test) and less than 3 min to analyze samples with a method detection limit of 10μg/L in the laboratory-spiked samples. The results from this field demonstration show the viability of the immunosensor for on-site analysis of explosives to assist in environmental remediation and monitoring efforts.
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