On-site detection of explosives in groundwater with a fiber optic biosensor

Two primary explosives involved in groundwater contamination, 2,4,6-trinitrotoluene (TNT) and hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), were detected on-site at low ppb levels with a semiautomated fiber optic biosensor. Validation of the Analyte 2000 (manufactured by Research International Inc., Woodinville, WA) for TNT and RDX detection was performed at two Superfund sites, Umatilla Army Depot and Naval Surface Weapons Center Crane. Samples from monitoring wells were split for analysis using the fiber optic biosensor on-site and using U.S. EPA SW-846 Method 8330 (reverse-phase high performance liquid chromatography) in an off site laboratory. The Analyte 2000, a multifiber probe fluorimeter, was coupled to a fluidics unit for semiautomated operation. The fiber optic biosensor assay is based on a competitive fluorescent immunoassay performed on the silica core of a fiber probe. From these studies, the limit of detection was determined to be 5 mu g/L for both TNT and RDX. In addition to the field samples, extensive laboratory analyses were performed to determine cross-reactivity, matrix effects, and false positive/negative rates.