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.