Field Portable Biosensors for the Detection of Explosives in Groundwater

EXTENDED ABSTRACT Biosensors provide a sensitive, specific, rapid, portable, and inexpensive means to fulfill the need for rapid on-site determinations of hazardous pollutants (e.g., explosives). Recent advances in instrumentation at NRL have led to two methods for measuring TNT and RDX: the FAST 2000 and the Analyte 2000. Engineering and design of both instruments was performed by Research International, Inc. (Woodinville, WA). These optical biosensors employ fluorescence immunoassay techniques on solid supports and are interfaced to portable computers for instrument control and data analysis. Each biosensor is portable, and easily set up within 30 minutes. The Fast 2000, a continuous flow immunosensor based on a displacement immunoassay, can quantify water samples (150 μl) with minimal sample preparation and reagent addition. Analysis is complete within five minutes with the fluorescent signal being proportional to the analyte concentration in the sample. The Analyte 2000 is a fiber optic biosensor based on a competitive fluoro-immunoassay and capable of simultaneously monitoring four optical probes. A fluorescent molecule similar to the analyte competes with the analyte for binding sites on immobilized antibodies on the surface of an optical probe. In this format, the fluorescence signal is inversely proportional to the amount of analyte in the sample (1.4 mL per four fiber probes). Results are determined in 7-12 minutes depending on the analyte concentration. Recently, extensive field trials designed to demonstrate the performance of these methods for on-site analysis were conducted at several geologically diverse sites. The sites, SUBASE Bangor (Washington), Umatilla Army Depot (Oregon), and NSWC Crane (Indiana) are all on the U.S. EPA Superfund list. Comprehensive laboratory data obtained with the FAST 2000 and the Analyte 2000 for spiked laboratory buffered samples and field data from groundwater samples was examined to determine detection limits, linear regression (correlation to EPA accepted SW846 Method 8330), bias, waste generation and cost analysis.