&EPA
United States
Environmental Protection
Agency
Office of Research and
Development
Washington DC 20460
EPA/600-R-95/518
August 1995
Innovative Technology
Verification Report
Clor-N-Soil PCB Test Kit Dexsil
Corp
VDSX
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UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
Office of Research and Development
Washington, DC 20460
Clor-N-Soil Test Kit Dexsil Corp.
Executive Summary
This innovative technology evaluation report (ITER) presents information on the demonstration and evaluation
of two field screening technologies for determining poly chlorinated biphenyl (PCB) contamination in soil.
The demonstration was conducted by PRC Environmental Management, Inc. (PRC), under contract to the
Environmental Protection Agency's (EPA) Environmental Monitoring Systems Laboratory-Las Vegas
(EMSL-LV). The demonstration was developed under the Monitoring and Measurement Technologies Program
(MMTP) of the Superfund Innovative Technology Evaluation (SITE) Program.
The two technologies selected for this demonstration and evaluation were the Clor-N-Soil Test Kit and the
L2000 PCB/Chloride Analyzer, both developed by the Dexsil Corporation. They were demonstrated and
evaluated in August 1992 in Kansas City, Missouri. The demonstration and evaluation of these two innovative
technologies were conducted in conjunction with the demonstration and evaluation of two other field screening
methods, the EnviroGard PCB Test produced by Millipore , Inc., and the Field Analytical Screening
Program PCB Method developed during the Field Investigative Team Contract under the EPA Superfund
Program. The demonstration and evaluation of these two other technologies are discussed in separate ITERs.
The findings of the demonstration of the two technologies
manufactured by Dexsil are summarized below.
Clor-N-Soil Test Kit
The Clor-N-Soil Test Kit is designed to quickly provide semiquantitative results for PCB concentrations
in soil samples. The test kit used for this demonstration provides a greater than or less than 50 milligrams per
kilogram (mg/kg) result using the principle of total organic chlorine detection. Compounds containing organic
chlorine, such as PCBs, are extracted from the soil sample using an organic solvent. Then, through a
series of chemical steps, the chloride ions are stripped from the PCB compound and transferred to an aqueous
solution. The extract is then mixed with a reagent to induce a color change that corresponds to the number of
chloride ions in the sample. Assuming that all chloride ions detected in the sample come from PCBs, it is
possible to determine whether PCBs are present at concentrations above a particular level. Because the test
kit reacts to all sources of organic chlorine, the presence of chlorine-containing compounds other than PCBs will
cause the kit to produce false positive results. The presence of sulfur in samples may produce the same
result.
The Clor-N-Soil Test Kit is portable, easy to operate, and useful under limited site conditions.
Depending on how the test kit is ordered from the developer, the cost of this technology ranges from $ 10
to $14 per analysis. The average time required to perform one analysis during the demonstration was
found to be 11 minutes.
To ensure that the test kit always produces a positive result for samples containing at least 50 mg/kg of PCBs,
the kit is designed with a correction factor. This correction factor accounts for any losses of chloride during its
extraction from the sample. Because of this correction factor, the test kit is likely to produce a high number of
false positive results when PCBs are present at concentrations below, but near, the detection level. During this
demonstration, the test kit produced 87 correct assays, 58 false positives, and 1 false negative.
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The false negative occurred when the test kit determined that less than 50 mg/kg of PCBs was present
in the sample, but the confirmatory laboratory indicated that the sample contained 293 mg/kg. Despite sample
homogenization, though, the confirmatory laboratory indicated a level of 1.77 mg/kg in a field duplicate of
that sample. This single false negative occurred from the analysis of a sample that appears as an outlier in all
other technology data evaluations.
Because the Clor-N-Soil Test Kit reacts with the chlorine in PCBs, it will produce different responses to
individual Aroclors, each of which contains a different percentage of chlorine. Because of this, the test kit will
produce false negative results for samples containing Aroclors 1016, 1221, and 1232, which contain lower
percentages of chlorine than Aroclor 1260, the Aroclor the kit is designed to detect.
PRC evaluated the test kit's precision by analyzing duplicate samples. Thirty-two field duplicate samples
were analyzed by the Clor-N-Soil Test Kit during the demonstration. The results indicated that the test kit was
able to duplicate its results 81 percent of the time. A review of the results that did not match showed that the
Clor-N-Soil Test Kit appeared to have more difficulty duplicating its results when the PCB concentrations were
near 1 mg/kg.
To evaluate the test kit's accuracy, PRC determined whether each confirmatory laboratory result was above or below
50 mg/kg. The test kit's results and the confirmatory laboratory's results were then evaluated using a 2 by 2
contingency table and the Fisher's Test statistic. Results from this analysis indicated that there was no correlation
between data from the test kit and data from the confirmatory laboratory. This suggests that the Clor-N-Soil Test Kit
is not accurate. However, this absolute assessment of accuracy may not affect the test kit's usefulness. The test kit's
inaccuracies were primarily the result of false positive results, and this type of inaccuracy would, at worst, result in
the misidentification of clean material as contaminated. To eliminate the effects of false positive and false negative
results, all critical samples should be confiied using EPA approved methods.
L2OOO PCB/Chloride Analyzer
The L2000 PCB/Chloride Analyzer is designed to quickly provide quantitative results for PCB concentrations
in soil samples. Like the Clor-N-Soil Test Kit, the analyzer uses the principle of total organic chlorine
detection. The principal difference between the Clor-N-Soil Test Kit and the L2000 PCB/Chloride Analyzer
is the way total organic chlorine is detected after the sample is extracted. The analyzer uses a chloride-
specific electrode to measure the amount of total organic chlorine in the extract and displays the results on a
screen. The analyzer also is capable of electronically converting the chloride concentration to produce quantitative
results for two different Aroclors. Like the Clor-N-Soi 1 Test Kit, the L2000 PCB/Chloride Analyzer
reacts to all sources of organic chlorine, and the presence of chlorine-containing compounds other than PCBs
will cause the analyzer to produce false positive results.
The analyzer is very portable, although electricity is required to operate it. It is easy to operate. During this
demonstration, the analyzer often needed to be recalibrated, particularly when analyzing samples with
high PCB concentrations. The analyzer is sold with enough reagents to perform 200 analyses at a cost of
$3,500. Additional reagents also can be purchased. Depending on the quantity ordered, the cost of additional
reagents ranges from $8 to $10 per analysis. The amount of time required to perform one complete sample
analysis during the demonstration averaged nine minutes. The detection limit of the analyzer is reported by its
developer to be 5 mg/kg, although a detection limit of 2 mg/kg was used during this demonstration.
Because the L2000 PCB/Chloride Analyzer reacts with the chlorine in PCBs, it will produce various
responses to individual Aroclors. The analyzer has a high likelihood of producing false negative results for
samples containing Aroclors 1016, 1221, and 1232, which contain lower percentages of chlorine than the
Aroclors the analyzer is set to detect. If, however, the Aroclor type is known prior to analysis, the L2000
PCB/Chloride Analyzer can be set to "total chlorine" and the result divided by the appropriate factor (0.21 for
Aroclor 1221, 0.32 for Aroclor 1232, and so forth.)
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To assess the analyzer's precision, PRC evaluated its performance in analyzing both laboratory and field
duplicate samples. The L2000 PCB/Chloride Analyzer had 18 sample pairs in which both the sample and its
duplicate had positive results. PRC used the data from the duplicate analyses to establish precision control
limits. The determination of precision was based on the percentage of duplicate sample pairs that had relative
percent differences (RPD) within these control limits. The precision control limits were set at 0 and 77.4
percent RPD. All but one of the 18 sample pairs' RPDs fell within the control limits. This one failure caused the
analyzer's overall precision to be 94.5 percent. The goal for precision for this evaluation was between 95 and 100
percent. While the 94.5 percent is not between 95 and 100 percent, the analyzer could not have come closer to
100 percent without every sample pair falling within the control limits; therefore, the precision was considered
acceptable.
To evaluate the analyzer's accuracy, PRC used a linear regression approach to compare the analyzer's
data to the corresponding confiitory laboratory's data. This analysis was based on 47 matched pairs of positive
sample results. For this regression analysis, the t n factor was 0.86, indicating that a relationship existed between
the two data sets. The analysis defined a regression line
with a y-intercept of 26.6 mg/kg and a slope of 0.84. These results indicate that the analyzer is not accurate,
but can be corrected mathematically. In addition to the regression approach, PRC used a nonparametric test
statistic, the Wilcoxon Signed Ranks Test, to verify the regression evaluation. It also indicated, at a 95 percent
confidence level, that the analyzer's data was significantly different from that of the confiiatory
laboratory.
Based on these results, the L2000 PCB/Chloride Analyzer's results should not be expected to be the same
as those from a confirmatory laboratory. However, if 10 to 20 percent of the samples collected also are sent to
a confirmatory laboratory, then the results from the other 80 to 90 percent can be corrected. This may result
in a significant savings in analytical costs.
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