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

Two primary explosives involved in groundwater contamination, 2,4,6-trinitr otoluene (TNT) and hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), were dete cted 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 biosen sor on-site and using U.S. EPA SW-846 Method 8330 (reverse-phase high perfo rmance liquid chromatography) in an off site laboratory. The Analyte 2000, a multifiber probe fluorimeter, was coupled to a fluidics unit for semiauto mated 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 bo th TNT and RDX. In addition to the field samples, extensive laboratory anal yses were performed to determine cross-reactivity, matrix effects, and fals e positive/negative rates.