DETECTION OF TNT IN WATER USING AN EVANESCENT-WAVE FIBEROPTIC BIOSENSOR

A general health hazard from explosive toxicity exists due to poor sto rage facilities for explosives and from contamination of soil and wate r with byproducts of explosive manufacture. To provide an effective me thod for monitoring water contamination, the Naval Research Laboratory 's fiber-optic biosensor was adapted for the detection of small molecu les such as explosives. A competitive immunoassay was developed for th e detection of the most widely used explosive, trinitrotoluene (TNT). Trinitrobenzenesulfonic acid (TNB), an analog of TNT, was labeled with a fluorophore and used as the analyte competitor. A solution containi ng 7.5 ng/mL sulfoindocyanine 5-ethylenediamine-labeled TNB (Cy5-EDA-T NB) was exposed to an antibody-coated optical fiber, generating a spec ific signal above background that corresponds to the 100% or reference signal. Inhibition of the 100% signal was proportional to the TNT con centration in the sample. Detection sensitivities of 10 ng/mL TNT (8 p pb) in buffer were achieved. Tests on river, harbor, and bilge water s amples spiked with TNT showed results similar to tests on laboratory ( buffer matrix) samples. To determine possible interferences, several s tructural analogs of TNT were tested.