Immunosensors act on the principle that the immune response of certain biological species (usually bacteria) to contaminants will produce antibodies, which in turn can be measured. To reduce the cost and time required for the accurate analysis of field samples of water and soil contaminated with explosive compounds, such as trinitrotoluene (TNT) and Royal Demolition Explosive (RDX), two immunosensors were developed. They are the fiber-optic biosensor and the continuous flow immunosensor for on-site screening and monitoring of contaminants. Both sensors determine the level of contamination by measuring the level of fluorescent activity caused by the introduction of a biological sample to the system. The fiber-optic biosensor works when contaminant molecules compete with fluorescent antibodies on the sensor. A decrease in fluorescent activity caused by contaminants binding onto antibody sites corresponds to the level of contamination. The continuous flow immunosensor works when the contaminant molecules displace fluorescent antibodies that are placed on a solid support. When displaced antibodies are detected, they correspond proportionally to the level of contamination.
Limitations and Concerns
Methods using biosensors based on fluorescence immunoassay techniques to detect TNT and RDX had a large number of false positive values for the TNT assay.
Insufficient information is presented about these technologies to address fully limitations and concerns.
It is unclear whether these sensors are effective in detecting compounds other than RDX and TNT.
While the sensors can be applied to the screening of chemicals, it is not clear how they would be employed for monitoring. It appears that the contaminant must come into direct contact with the sensor. More information is needed on how the sensors can be arranged to serve a monitoring function.
These sensors are analytical tools to detect TNT and RDX in soil and groundwater. Both sensors are portable, quick (2–10 minutes per analysis), and sensitive (low parts-per-billion concentration detection).
Technology Development Status
The fiber-optic biosensor and the continuous flow immunosensor, developed at the Naval Research Laboratory (NRL) in collaboration with Research International, will be employed at a site for the detection of TNT and RDX. These sensors are considered pilot projects.
Other Resources and Demonstrations>
Extensive field trials (three for groundwater and one for soil) were conducted at several sites. The groundwater sites, the Bangor Naval Submarine Base (Washington), Umatilla Chemical Depot (Oregon), and the Crane Naval Surface Warfare Center (Indiana), are on the U.S. EPA National Priorities List (˝Superfundţ). Overall, results for the biosensors suggest that the instruments are promising field technologies that will require additional development before they are suitable for field use.
See http://www.clu-in.org/characterization/technologies/exp.cfm for a technical description of explosives in different media and the use of some analytical techniques.
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