Immunoassay
Analysis
Description
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.
Applicability
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.
Web
Links
http://www.serdp-estcp.org/content/download/3607/58263/file/CU-199713-CP.pdf
http://www.frtr.gov/site/6_2_20.html
http://clu-in.org/characterization/technologies/immunoassay.cfm
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.
See http://tools.niehs.nih.gov/srp/researchbriefs/view.cfm?Brief_ID=216
.
See http://clu-in.org/characterization/technologies/exp.cfm#86
for a technical description of explosives in different media and the
use of some analytical techniques.
See https://ert2.navfac.navy.mil/printfriendly.aspx?tool=energeticconstituents
for sampling of energetic constituents.