United States
Environmental Protection
Agency
Environmental Monitoring
Systems Laboratory
Las Vegas, NV 89193-3478
Research and Development
EPA/540/SR-94/519 December 1994
EPA Project Summary
A Field Screening Method for
Polychlorinated Biphenyl
Compounds in Water
Shen Lin, Edward J. Poziomek, and William H. Engelmann
The U.S. Environmental Protection
Agency (EPA) has been exploring the
complexation of silver ions with cer-
tain organic pollutants as part of a
search for alternative low-cost, rapid
field screening methods. The effort has
resulted in a rapid, easy, and inexpen-
sive procedure for determining poly-
chlorinated biphenyls (PCBs) in water.
Based on previous testing of samples
by General Electric Corporate Research
and Development, a cosponsor of this
project, there was a special interest in
developing a field-screening procedure
of PCB aqueous extracts performed
from a current soil remediation proce-
dure in which the extractant contained
1-3% surfactant by weight to enhance
solubility of PCBs. A test was devel-
oped, based on forming complexes of
PCBs with silver ions, which was fol-
lowed by ultraviolet (UV) irradiation to
yield metallic silver. The appearance of
a gray-to-brown color, depending on
PCB concentration, was used to signal
the presence of PCBs. This method
allows the test color to be directly com-
pared with color charts to estimate the
PCB concentration without the need
for instrumentation. In addition to soil
remediation monitoring, potential ap-
plications include well monitoring,
wellhead protection monitoring, post-
closure monitoring, and rapid labora-
tory screening.
For soil remediation monitoring, it
was found that several varieties of fil-
ter paper or solid phase extraction
(SPE) membranes could be used in a
dipstick mode, followed by spraying
with methanolic silver nitrate solution
and irradiation with 254 nm light from a
hand-held UV lamp to provide a color
spot test. The detection range was 1-
500 ppm in the presence of either 3%
Renex KB™* or Neodol (R) 1-7™, sur-
factants currently being examined in
soil remediation.
This Project Summary was developed
by EPA's Environmental Monitoring Sys-
tems Laboratory, Las Vegas, NV, to an-
nounce key findings of the research
project that is fully documented In a
separate report of the same title (see
Project Report ordering information at
back).
Introduction
The overall challenge of field screening
involves dealing with numerous pollutants
within many classes (organic, inorganic,
biomarker, and radionuclide), across vari-
ous media, and in complex mixtures. The
detection limits of field methods are not
always as low nor as reliable and accu-
rate as laboratory methods. However, the
data quality objectives in a particular sce-
nario may allow field methods to be used.
For example, less accurate methods can
be used to screen environmental samples
prior to confirmatory laboratory analyses.
A cost advantage results by reducing the
number of required laboratory analyses.
Field screening methods may provide
rapid performance at low cost to allow
determination of whether a parameter of
interest is present or absent, above or
' Mention of trade names or commercial products does
not constitute endorsement or recommendation for
Printed on Recycled Paper
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below a predetermined threshold at a given
site, or at a concentration within a prede-
termined range of interest. Field screen-
ing methods can also be used in the field
to identify the nature and extent of con-
tamination at individual sites. A few field
screening methods are currently available
and additional ones are being developed.
The most mature methods are based on
gas chromatography and X-ray fluores-
cence. One of the clear trends is to minia-
turize. Methods that are still in various
stages of development include the use of
fiber optic sensors and chemical
microsensors, such as piezoelectric quartz
microbalances and surface acoustic wave
probes. The technologies developed as
field screening methods conform to the
monitoring and measurement needs_of
many EPA programs.
The need for field screening of ground
water relates to protecting public water
supply wells and well fields, following
remediation efforts, and post-closure moni-
toring of hazardous waste disposal sites,
as examples. Ground water contains many
natural constituents, with the various spe-
cies and concentrations depending on fac-
tors such as the specific geochemical
environment and the source of ground
water. The major anions that are usually
analyzed for general water quality include
bicarbonate, chloride, nitrate, and sulfate.
Other general indicators include electrical
conductivity, temperature, pH, dissolved
oxygen, biochemical oxygen demand,
chemical oxygen demand, total organic
carbon, oxidation-reduction potential, total
suspended solids, total dissolved solids,
and turbidity.
The present research, described in the
full report (based on the Master of Sci-
ence thesis of Shen Lin, first author of this
project summary), describes the develop-
ment of a new concept for field screening
that emphasizes speed, ease of applica-
tion, tow cost, and in situ water monitoring
for following PCB soil remediation.
The central idea brought forward in this
research was to form silver complexes
with RGBs directly in the environmental
samples and to display their comparative
concentration levels through rapid devel-
opment of a gray-to-brown coloration of
finely-divided silver on SPE or filter paper
substrates using a brief UV irradiation or
sunlight. In other words, this new process
combines development of a photo-gray or
photo-brown coloration on various sub-
strates and relates the color or shading to
a color chart produced from known silver
concentrations, and therefore PCB levels,
in the environmental sample.
Approach
A preliminary step was to devise a con-
venient method for extracting and con-
centrating PCBs from the aqueous
environmental samples. This was followed
by the development of a chemical reac-
tion or molecular association effect that
could provide a visual signal for the pres-
ence of PCBs.
While liquid-liquid extraction can be used
to separate organic components from
aqueous solutions, the process is slow,
labor intensive, and requires large vol-
umes of solvents. The latter creates an-
other potential pollution problem. With
rising waste disposal costs, laboratory
technologists today are turning to the use
of SPE membranes._to,«adso.rb anoLcon.-_
centrate the organic compounds directly
from the water sample, avoiding the need
for organic solvents. Filtering the solution
through a SPE disk concentrates the sol-
ute through adsorption on the silicate ma-
trix. Their specific adsorbing power is
generally sufficient to allow SPE material
to be cut into small tabs and used in a
"dipstick" mode with the water sample.
The SPE disk or tab, exposed to PCBs
in solution, generally shows no color
change (other than possibly some colora-
tion from suspended matter in the sample).
The early literature (1970s) of thin-layer
chromatography provided insight into pos-
sible visualization agents for the adsorbed
PCBs on the SPE disks or tabs: PCBs
can be reacted with silver nitrate to yield
silver-PCB complexes. These complexes
are not stable and UV irradiation from
sunlight or other source rapidly breaks
down the silver-organic complex. Free sil-
ver, in finely divided form, appears on the
substrate as a gray-to-brown coloration.
Based on the literature references, the
decision was made to exploit this reaction
and optimize the performance to provide
adaptation for environmental monitoring.
It was also found in the early experiments
that if the PCB concentration is high
enough, preconcentration, using SPE tech-
niques, is not necessary. Filter paper can
be spotted with this test solution directly,
or a filter paper tab can be dipped into the
solution.
Experimental
Two test formats were chosen for
sample collection. One used small tabs,
cut from SPE material or filter paper, and
exposure to the water samples in a "dip-
stick" manner for several minutes. In a
second test format, test solution was
placed dropwise directly on the SPE or
filter paper tabs. Other test formats, such
as filtering the test solutions through the
SPE or filter paper disks, could have been
used but at a loss of ease for use in the
field. It was decided to place developmen-
tal emphasis on the dipstick test format
because of its simplicity and retained ef-
fectiveness.
When PCBs contaminate soil, they raise
a specific environmental challenge in that
they become firmly bound to the soil ma-
trix because of their high molecular weight
and low water solubility.
However, the presence of surfactants
may increase the solubility of PCBs in
water. The use of surfactants such as
Renex™ and Neodol (R) 1-7™ (both non-
ionic compounds) is being examined by
others- Jn ^PCB ., so.il,-washing ... and.
remediation processes.
The development of a PCB detection
test in the presence of these surfactants
would serve to provide a very useful moni-
toring scheme to follow the soil-washing
procedure. Surfactants such as these in-
crease the solubility of PCBs to the 500
ppm range. At high concentration levels,
the use of SPE techniques would not seem
necessary. However, experiments using
SPE membranes to concentrate PCBs fur-
ther were included to increase the appli-
cability of the test to other field screening
scenarios.
Test solutions of the PCBs were pre-
pared in methanol and diluted with deion-
ized water, either with or without surfactant.
Control solutions also contained surfac-
tants, if used in the tests.
The SPE tabs (1x1 cm) were condi-
tioned by dipping into methanol just be-
fore use; this allowed them to be wet
easily by the aqueous test solutions. Tabs
were either suspended in the various PCB
test solutions for 30 minutes or dipped
and quickly removed. They were then
sprayed with 0.059 M silver nitrate in
methanol. Irradiation followed with a UV
lamp (254 nm) for 1-3 minutes. The UV
lamp was held 1.5 cm from the tabs. The
development of color, relative to a control
tab after 1 minute, signaled the presence
of PCBs.
Filter paper tabs (1 x 1 cm) were dipped
into the PCB test solution, removed,
sprayed with 0.059 M silver nitrate in
methanol, and exposed for 3 minutes in
the same manner as above. For simplicity
in field testing and to avoid the need for
instrumental readings, Ameritone™ paint
color chips were used as standards for
defining the exact color and intensity. All
results were based on at least duplicate
runs, with some being taken in triplicate.
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Results and Discussion
Tests with SPE membranes (1-hour pas-
sive immersion), followed by silver nitrate
visualization, detected PCBs at the 0.5-
1.0 ppm level in the absence of surfac-
tant; at 22-24 hours there was no
improvement, but shortening the exposure
time to 30 minutes raised the detection
level to 5 ppm. SPE membranes were
also used to extract PCBs from aqueous
solution containing surfactant by exposing
the tabs for 30 minutes. The detection
limit varied from 0.5-5 ppm, depending
on the type of PCB.
Tests with filter paper tabs (Whatman
541™) involved dipping and immediate
removal, spraying with silver nitrate solu-
tion,, and irradiating, with., UV Jight. ,The^
PCB solutions contained either Renex
KB™ or Neodol 1-7™ surfactants. The
results show that PCBs can be readily
detected on Whatman 541 filter paper in
the presence of these surfactants. The
colors differed somewhat from SPE tabs,
depending on the PCB and surfactant type.
At the high PCB level of 500 ppm, the
test colors were not gray but brown with a
trace of gray. The control tabs showed
very little color even though the solutions
contained 3% surfactant.
It is also interesting to note that dipping
the Whatman 541 filter paper tabs and
quickly removing them is about as sensi-
tive as the technique in which SPE tabs
(in the presence of surfactant) were al-
lowed to stand for 30 minutes. It is sug-
gested that the surfactant may be
competing with the PCBs for adsorption
onto the SPE medium.
As for possible interferences, it was ex-
pected that chloride ions would interfere
in the visualization reaction since silver
chloride, which is extremely sensitive to
light, would be formed. The sensitivity for
chloride ion was found to be 1 ppm in the
absence of surfactants; no color was ob-
served with 0.5 ppm. Positive tests were
found with PCBs at 0.5 ppm, but the higher
sensitivity is understandable since equiva-
lent chloride would be available from the
PCBs. The colors matched closely those
obtained using PCBs, i.e., very light gray
at 1 ppm and brown at the highest con-
centrations, i.e., 1000 ppm chloride ion.
The chloride ion interference could be
eliminated by adding a few granules of
anion exchange resin (AG 1-X2™), lightly
agitating, and continuing with the test in
the usual manner. Results remained nega-
tive, up-to 1000 ppm chloride ion. ._ ... ,
Summary and Conclusions
The objective was to develop a simple,
alternative, and inexpensive test proce-
dure for field screening PCBs in water.
There was a special interest to determine
whether the test would work well in the
presence of 1-3% surfactants in order to
follow the progress of washing or
remediation of soils contaminated with
PCBs.
A visual test requiring no instruments
was developed based on forming silver
ion complexes of PCBs from silver ni-
trate, followed by brief UV irradiation to
form finely divided silver metal. The lat-
ter appeared as a gray or brown colora-
tion, depending on PCB concentration.
The test color can be easily compared
to standard color charts or paint chips
to give an estimate of the PCB level. In
addition to soil-remediation monitoring,
potential applications include well moni-
toring, wellhead protection monitoring,
post-closure monitoring, and rapid
screening of laboratory samples.
A number of factors were found to af-
fect the sensitivity of the visualization re-
action, including choice of test matrix,
nature of the surfactant, wavelength and
intensity of the light, and presence of pos-
sible interferences. These are described
in more detail in the full report.
As expected, chloride ion was found to
interfere. The chloride sensitivity was found
to be 1 ppm in the presence of surfac-
tants. The colors closely matched those
obtained using PCBs. However, the chlo-
ride ion interference was eliminated by
adding a few granules of an anion ex-
change resin to the test solution.
The potential of exploiting the results
for a PCB field screening test is judged to
be high. The findings can be used as a
basis to further improve the PCB detec-
tion test and to develop new field screen-
ing methods for other pollutants.
A promising area for further research is
the use of a catalyst for the dechlorination
of PCBs (and other organohalogen com-
pounds) that do not photosensitize silver
ion reduction.
Also, a detailed examination of the
chemistry of photography, including color
photography, may identify other opportu-
nities for enhanced sensitivity and selec-
tivity. The use of indicators presorbed onto
SPE membranes, which can both extract
and detect pollutants in either water or air,
appears to be a promising area to ex-
plore.
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Shen Lin and Edward J. Poziomek are with University of Nevada, Las Vegas, NV
89154-4009. The EPA author, William H. Engelmann, (also the EPA Project
Officer, see below) is with the Environmental Monitoring Systems Laboratory,
Las Vegas, NV 89193-3478.
The complete report, entitled "A Field Screening Method for Polychlorinated
B'phenyl Compounds in Water," (Order No. PB95-129078; Cost: $ 17.50, subject
to change) will be available only from
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at
Environmental Monitoring Systems Laboratory
U.S. Environmental Protection Agency
Las Vegas, NV 89193-3478
United States
Environmental Protection Agency
Center for Environmental Research Information
Cincinnati, OH 45268
Official Business
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EPA
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EPA/S40/SR-94/519
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