Immunoassay tests are designed to detect specific chemicals by measuring the chemicals' response to specific antibodies. Antibodies are developed specifically to bind with organic compounds [e.g., polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), and pesticides]. The antibodies do not respond to dissimilar substances. For example, antibodies may be coated inside a test tube. A sample is added to the test tube followed by a chemical that reacts with enzymes released by the antibodies. This chemical changes color in response to the enzymes. Color change in an extracted solution is related to specific contaminant concentration.
The tests can be conducted in laboratory settings or in the field. The immunoassay analyses referred to here were conducted in the field to provide real-time data. However, the actual assay techniques were not described. Immunoassay analyses reduce costs by providing real-time data, thus reducing the time spent waiting for analytical results and the amount of material that has to be excavated.
Limitations and Concerns
There may be false readings if a number of contaminants are found in the same sample.
When immunoassay is used as a screening tool, it will not pick up chemicals that are not suspected of being there. It is not appropriate if quantitative results are required
It cannot differentiate among types of PCBs.
The technology has been tested and verified for PCBs, fuels, and PAHs. There is not enough information to assess limitations with regards to metals and explosives.
This process is very sensitive to the type of matrix. For example, it may not be good to use it in heavy clay soils where the chemical is bound to clay particles.
If multiple, similar compounds are present, there is a risk of interference.
It may produce a secondary waste that must be disposed of.
Immunoassay kits have been developed to rapidly screen for fuels, semi-volatile organic compounds, pesticides, and some metals, in soil and sediment, in groundwater and in surface water. Enzyme immunoassay (EIA) test kits are also available for RDX and TNT. It has also been used to screen a site for site closure. Perhaps its best use, however, is to confirm basic site conceptual models and develop a more elaborate sampling approach.
Technology Development Status
Immunoassay methods are common and commercially available. They have been used frequently for PCB detection. However, this method should not be considered an approved application for verifying conditions for site closure.
Other Resources and Demonstrations
The U.S. Army Corps of Engineers' (USACE) Sacramento District has removed a 5-mile-long fuel oil distribution system and 250 underground storage tanks from the Presidio of San Francisco in California. The Regional Water Quality Control Board (the agency in California that is authorized to enforce actions that affect surface and groundwater)) accepted the use of immunoassay analysis for the site closure of fuel-contaminated soil. Immunoassay has been used as a screening tool at many sites, including Hunter's Point Naval Shipyard
In San Francisco and across the San Francisco Bay at Alameda Naval Air Station, the U.S. EPA has also tested the immunoassay method for specific compounds in its Environmental Technology Verification program.
The U.S. Army Corps of Engineers' Nashville District used immunoassay kits at Campbell Army Air Field, located at Ft. Campbell, Kentucky, to determine the extent of PCB contamination at various sites around the facility. Preliminary samples were collected on the first day of sampling and analyzed that evening in the field laboratory. Results obtained were then used to plan the next day's sampling. This second day of sampling defined the extent of the contamination.
for a technical description of explosives in different media and the
use of some analytical techniques.