United States
Environmental Protection
Agency
Environmental Sciences Division
P.O. Box 93478
Las Vegas, NV 89193-3478
March 1999
OFFICE OF RESEARCH AND DEVELOPMENT
TECHNOLOGY SUPPORT PROJECT
v>EPA Immunochemisty for
Environmental
Monitoring
Introduction
Background
Field Use
Advantages and
Limitations
The Environmental Sciences
Division (ESD) in Las Vegas is
pioneering an investigation into
the usefulness of several
immunochemical techniques for
monitoring the extent of
contamination in various
environmental and biological
matrices. Immunochemistry
includes all methods of sample
preparation and analysis that
incorporate antibodies that have
been developed for specific
analytes or groups of analytes.
Enzyme-based immunochemical
techniques have been in use
since the '70s and more recent
efforts have focused on their
applicability to the complex
matrices that face environmental
scientists. The ESD has
developed and demonstrated
several immunochemical
techniques and believes that
these methods hold great
promise for the quantitative
analysis of target analytes for use
in ground-water surveillance, in
situ hazardous waste site
monitoring, and assessment of
human exposure. Current work
involves the analysis of
chemicals, like PCBs,
nitroaromatics, and certain
pesticides, that are difficult to
analyze by other analytical
methods.
Immunochemistry includes
techniques such as
immunoaffinity and immunoassay.
Immunoaffinity is a sample
preparation procedure that takes
advantage of the attraction
between an antibody and a
specific analyte. Immunoaffinity
preparations have great potential
for cleanup of complex samples
like dioxins. By rinsing a sample
over an antibody-treated surface,
scientists can isolate particular
compounds in the sample that
adhere to the antibody. The
isolated compound is then eluted
from the immobilized antibody
and is ready for analysis by
chromatography or
immunoassay. One common
immunoassay is the enzyme-
linked immunosorbent assay
(ELISA). The specificity of the
antibody for the analyte and the
resultant immune complex is the
basis for the specificity of
immunoassays. Most field
immunoassays are colorimetric
analytical methods that quantify
compounds of interest. A sample
is spiked with a known amount of
a labeled analyte. The label is
typically an enzyme. A
chromogenic substrate is added
to serve as an indicator of
compound concentration in the
sample. Laboratory-based
immunoassays include
fluorescent and radioactive
methods that have greater
sensitivity but are less portable.
Immunoassays are portable,
rugged, and inexpensive. Their
use at hazardous waste sites has
been investigated by the ESD.
The results of Superfund
Innovative Technology Evaluation
(SITE) studies indicate a strong
correlation between field
immunoassays, laboratory
immunoassays, and gas
chromatography/mass
spectrometry. The only
equipment needed is a
spectrophotometer, various
microtiter plates or test tubes,
precision pipets, and
immunologic reagents. The 96-
well microtiter plate is
approximately 3" x 6" and has 96
depressions, each capable of
holding about 250 uL liquid.
Smaller microtiter strips are
available that can be assembled
to form modular sections for
individual analytes. These plates
and test tubes are available
precoated with the antibody base.
Another field use of
immunochemistry is being
explored at the ESD. This use
may revolutionize safety and
exposure precautions used by
workers who deal with hazardous
chemicals. Dosimeter badges
with an immunochemical twist are
available for pentachlorophenol
and nitroaromatics. These
personal exposure monitors
(PEMs) are lightweight,
inexpensive, can be analyzed
quickly, and provide real time
indication of exposure. These
badges employ a microdialysis
tubing containing an immobilized
antibody phase. Immediate
identification of high exposure
levels is critical to the conduct of
safe site characterization.
The use of immunochemical
techniques is gaining acceptance
in the area of environmental
science. One need that is being
addressed is that of specificity.
Frequently, immunoassays are
available for a class, like PCBs.
Specific quantitation for each
component would be difficult.
197CMB98.FS-23 • Rev. 5/13/99
-------
Advantages and
Limitations
Continued
Advantages
Limitations
Future
Reference
For Further
Information
PEMs are available for
pentachlorophenol and are being
developed for parathion and
chlorpyrifos. The development of
PEMs must address the question
of diffusion of chemicals through
the dialysis tubing, the optimum
concentration of the antibody,
detection limits and quantitation
of the badge, the efficiency of the
antibody in capturing the analyte,
and the capacity of the device.
Field portable
User friendly
Quick and inexpensive
Potential for wide range of
analytes
Useful for many matrices
Low detection limits
Separate immunoassay
needed for each analyte
More complex analysis
required for quantitation of
specific analytes
Long development time for
new antibodies and methods
The ESD is active in the
development of all
immunochemical methods that
have potential for Agency use.
One new avenue of investigation
is the use of antibody-coated
fiber optic immunosensors.
Another application is the
integration of robotics capability
for high sample throughput and a
tiered analytical approach, i.e.,
biological and environmental
samples, biomarkers, target
analytes, and degradation
products. This system of
analytical procedures will enable
scientists to measure
contamination at the source,
follow the fate and transport of
residual amounts, and assess
human exposure.
Multi-analyte immunoassays that
can identify several analytes
simultaneously are expected to
expand the desirability of
immunoassay technology for
environmental use. Work in this
area is already underway at the
ESD.
Immunochemical Methods for Environmental Analysis, J. M. Van Emon and Mumma, R. O., eds., ACS
Symposium Series 442, ACS, Washington, DC, 229pp. 1990.
For further information about immunochemistry for
environmental monitoring, contact:
Dr. Jeanette Van Emon
Immunochemistry Program
U.S. Environmental Protection Agency
National Exposure Research Laboratory
Environmental Sciences Division
P.O. Box 93478
Las Vegas, NV 89193-3478
Tel: (702)798-2154
Fax: (702)798-2243
For information about the Technology Support
Center at the ESD, contact:
Mr. J. Gareth Pearson, Director
U.S. Environmental Protection Agency
National Exposure Research Laboratory
Environmental Sciences Division
P.O. Box 93478
Las Vegas, NV 89193-3478
Tel.: (702)798-2270
The Technology Support Center fact sheet series is developed and written by Clare L. Gerlach, Lockheed
Martin, Las Vegas.
------- |