In the summer of 1995, the EPA conducted a performance evaluation of several commercially available test kits and two prototype biosensor devices to determine if any of these technologies were feasible as an alternative to the standard EPA SW-846 Method 8330 test for explosives in aqueous samples. These on-site assays offer potential advantages in cost, assay time, and convenience over the traditional analysis via high-performance liquid chromatography (HPLC). The continuous flow immunosensor (CFI) was one of the biosensors participating in this trial, which took place at two Superfund sites located on military bases. The CFI uses a small column filled with plastic beads containing immobilized antibodies against the explosive being assayed and a fluorescent dye-labeled explosive analog. Detection occurs when the native explosive in the sample is swept into the column and displaces some of the dye-labeled analog, which is quantified via a fluorometer. Results from these tests showed that the CFI could produce data comparable to HPLC with no significant problems with cross-reactivity of the antibodies against other explosives or their breakdown products.

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A synthetic scheme has been developed for the preparation of a dye-labeled analog of polychlorinated biphenyls. The reaction of 2,3,5-trichlorophenol with 3-bromopropylamine hydrobromide under basic conditions was used to introduce a free primary amine group into the parent compound by formation of a stable ether linkage. Reaction of this amine with the succinimidyl ester of a sulfoindocyanine dye resulted in amide bond formation to produce a fluorescently-labeled product. The dye conjugate was used to charge a column containing immobilized antibodies against polychlorinated biphenyls. Upon application of samples containing various concentrations of polychlorinated biphenyls, the fluorescent analog was displaced from the column in amounts proportional to the concentration of analyte. Concentrations of polychlorinated biphenyl as low as 1 ppm were measurable using this system.

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