®EPA
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4
technical BRIEF
Detecting Chemical Agents and Pesticides in Water,
Using Enzymatic Test Kits
Four enzymatic test kits evaluated for determining the presence of chemical
warfare agents in water
In the past, people in the United States have largely taken the convenience of potable municipal
water for granted. However, the threat of intentional
contamination of our water supplies is becoming a
concern because of a rise in the number of terrorist
acts around the world. As a result, there is much
interest in technologies that can be used to detect a
contamination event as well as dispel or confirm the
credibility of a threat. Such technologies include
enzymatic test kits, which are generally designed to
be handheld and portable. These kits can detect the
presence of chemical agents, carbamate pesticides,
and/or organophosphate pesticides through a
cholinesterase enzyme reaction. Under contaminant-
free conditions, the enzyme reacts with other
reagents present in the test kit. However, the presence of contaminants from one or more of the
above chemical classes causes the enzyme activity to be inhibited. Inhibition is indicated by a
color change.
In late 2005 and early 2006, EPA evaluated four enzymatic test kits:
Eclox™-Pesticide Strips (Severn Trent Services)
•	Neuro-IQ Tox Test Kit™ (Aqua Survey, Inc.)
•	OP-Stick Sensor (Protein-Biosensor)
•	Organophosphate/Carbamate Screen Kit (Abraxis LLC)
EPA tested each enzymatic test kit to determine the responsiveness to specific toxic
compounds as well as to possible interfering compounds and matrices. Because enzymatic test
kits are anticipated to serve mainly as screening tools in water monitoring scenarios, this testing
produces only qualitative results (i.e., results indicate only the presence or absence of a
contaminant). The kits cannot distinguish between contaminants; however, some can indicate
the concentration range of contaminants (high, medium, low). Each kit was specifically
evaluated for:
•	Accuracy
•	Precision
•	False positive/negative rates
•	Matrix and interference effects
•	Operational factors
U.S. EPA's Homeland Security Research Program
(HSRP) develops products based on scientific
research and technology evaluations. Our products
and expertise are widely used in preventing,
preparing for, and recovering from public health and
environmental emergencies that arise from terrorist
attacks. Our research and products address
biological, radiological, or chemical contaminants that
could affect indoor areas, outdoor areas, or water
infrastructure. HSRP provides these products,
technical assistance, and expertise to support EPA's
roles and responsibilities under the National
Response Framework, statutory requirements, and
Homeland Security Presidential Directives.
This document does not constitute nor should be construed as an EPA endorsement of any particular product,
service, or technology.

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Test Design
Table 1 identifies the enzymatic test kits that were tested using various water types fortified
(spiked) separately with contaminants and interfering compounds.
Table 1. Technologies, Contaminants, and Interfering Compounds
Technologies
Contaminants (test range
concentration, mg/L)
Interfering
Compounds
Eclox™-Pesticide Strips
VX (0.021-2.1)
Sarin GB (0.02-20)
Soman GD (0.0014-1.4)
Aldicarb (0.026-260)
Dicrotophos (0.14-1,400)
Humic Acid
Fulvic Acid
Calcium
Magnesium
Neuro-IQ Tox Test Kit™
OP-Stick Sensor
Organophosphate/Carbamate
Screen Kit
Three types of water samples were tested in these evaluations: performance test (PT), drinking
water (DW), and quality control (QC). PT samples were prepared with deionized (Dl) water and
fortified with the contaminant only, the interferent only, or both the contaminant and interferent.
Contaminant-only PT samples were tested in a series of concentrations that included the
accepted lethal dose concentration and dilutions at approximately 10; 100; 1,000; and 10,000
times less than the lethal dose.
DW samples were tested to determine the effects of matrix-specific characteristics (e.g.,
location, filtering) on the technology being evaluated. DW samples were collected from four
geographically diverse municipal sources that varied in source (ground water or surface water),
treatment (filtered or unfiltered), and disinfection process (chlorination or chloramination). DW
samples were either not spiked or spiked with a contaminant at a single concentration level 10
times more dilute than the lethal dose.
All PT and DW samples were analyzed in triplicate. The result of each replicate sample set was
reported as a ratio of the number of positive results to the total number of replicates (e.g., 0/3,
1/3). Method blank QC samples consisted of 10% of all samples. The method blanks were not
considered in evaluations of the various test parameters.
Performance and Results
The accuracy of the enzymatic kits was determined by dividing the number of positive
responses by the overall number of spiked contaminant-only PT samples. The precision of the
technologies was determined by calculating the number of consistent responses for ail sample
sets.
Responses were considered consistent if all three replicates had similar results. A false positive
rate was reported as the frequency of positive results out of the total number of unspiked
samples. A false negative rate was reported as the frequency of negative results out of the total
number of spiked PT (contaminant and interferent) samples and spiked DW samples. Table 2
summarizes the results of the evaluation parameters for each technology.
June 2008
EPA/600/S-08/010
This document does riot constitute nor should be construed as an EPA endorsement of any particular product,
service, or technology.

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Table 2. Summary of Results
Technologies
Contaminant"
Accuracy
Precision
Total False
Positives
Total False
Negatives
Number
of Matrix
Effects
Number of
Interferent
Effects

VX
100%
100%
0/24
0/30
0
0

GB
100%
100%
0/24
0/36
0
0
Edox™-Pesticide Strips
GD
78%
95%
0/24
0/33
0
0

aldicarb
50%
100%
0/24
6/36
0
0

dicrotophos
100%
95%
0/24
20/30
9
11

VX
100%
90%
13/24
1/39
6
8

GB
93%
90%
13/24
1/39
6
7
Neuro-IQ Tox Test Kit™
GD
87%
90%
13/24
2/39
6
7

aldicarb
67%
95%
3/24
8/39
0
6

dicrotophos
44%
90%
3/24
7/33
0
5

VX
33%
62%
0/24
7/39
0
3

GB
60%
71%
0/24
2/30
0
0
OP-Stick Sensor
GD
27%
57%
0/24
2/39
0
0

aldicarb
100%
95%
1/24
0/27
0
1

dicrotophos
100%
100%
0/24
0/33
0
0

VX
100%
90%
3/24
0/33
1
2
Organophosphate/
Carbamate Screen Kit
GB
100%
90%
3/24
0/39
1
2
GD
100%
90%
3/24
0/36
1
2
aldicarb
100%
86%
4/24
0/39
0
4

dicrotophos
100%
81%
5/24
5/39
1
9
*'VX = VX nerve agents, GB = sarin, and GD = soman
The following is a summary of the testing of the 20 kit and contaminant combinations:
•	100% accuracy was achieved in 11 instances.
•	Minimum accuracy across all contaminants was one instance of 27%.
•	100% precision was exhibited in four instances, while the minimum precision was
57%.
•	There were no false positive results in 9 instances.
•	Three of these combinations produced false positive results in 13 out of 24 replicates
of unspiked DW or interferent PT samples.
•	In one dicrotophos instance, 20 of 30 spiked samples were determined to be falsely
negative due to matrix and interference effects. However, in most cases, the number
of false positives and negatives was much lower.
•	100% accuracy, 100% precision, no false positives, and no false negatives were
achieved for three combinations of kits and contaminants (Eclox™-Pesticide Strips
and VX, Eclox™-Pesticide Strips and GB, OP-Stick Sensor and dicrotophos) .
June 2008
EPA/600/S-08/010
This document does riot constitute nor should be construed as an EPA endorsement of any particular product,
service, or technology.

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Note that the total number of matrix and interferent effects did not always equal the total number
of false negatives and false positives because some false negatives occurred with contaminant-
only PT samples.
CONTACT INFORMATION
For more information, visit the EPA Web site at www.epa.gov/nhsrc.
Technical Contact: Eric Koglin (koglin.eric@epa.gov)
General Feedback/Questions: Kathy Nickel (nickel.kathy@epa.gov)
June 2008
EPA/600/S-08/010
This document does not constitute nor should be construed as an EPA endorsement of any particular product,
service, or technology.

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