United Starts Office of Research and EPA 600/R-94/181
Environmental Protection Development September 1994
*9.ncy WMhiigton, DC 20460 EPA 600-R-94-181
An Evaluation of
Four Field Screening
Techniques for
Measurement of BTEX
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AN EVALUATION OF FOUR FIELD
SCREENING TECHNIQUES
FOR
MEASUREMENT OF BTEX
by
E.N. AMICK
and
J.E. POLLARD
LOCKHEED ENVIRONMENTAL SYSTEMS & TECHNOLOGIES COMPANY
980 KELLY JOHNSON DRIVE
LAS VEGAS, NEVADA 89119
WORK ASSIGNMENT MANAGER
K.E. VARNER
ENVIRONMENTAL MONITORING SYSTEMS LABORATORY
U.S. ENVIRONMENTAL PROTECTION AGENCY
944 E. HARMON
LAS VEGAS, NEVADA 89119
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NOTICE
The following commercial products (requiring Trademark*) are mentioned in this report:
Because of the frequency, of usage, the Trademark was not indicated. If it becomes necessary to
reproduce any segment of this document containing any of these names, this notice must be included
as pan of that reproduction.
Antox
Lab In A Bag
Microsensor Systems Inc. (MSI)
Draeger
Mention of these products does not constitute Air Force endorsement or rejection of this product,
and use of information contained in this document for advertising purposes without obtaining
clearance according to existing contractual agreements is prohibited.
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EXECUTIVE SUMMARY
A laboratory investigation of field-portable technology demonstrated that available
analytical methods for volatile aromatic hydrocarbons can produce data of known quality in a
timely, cost effective manner. Based on the results of a literature search, which was made to
identify current field analytical techniques for the detection of benzene, toluene, ethyl benzene,
and xylene (BTEX) in environmental samples, four promising technologies were selected for
laboratory evaluation. No single field methodology was found to be superior to others; each
method has advantages and disadvantages.
The Antox immunoassay test is simple to perform and can be used as a quick indicator of
BTEX contamination in water. This test provides a reliable, qualitative indicator for BTEX at
levels above 75 parts per billion (ppb). Although the manufacturer claims sensitivity to 25 ppb,
75 ppb appears to be a more practical method detection limit.
Detector tubes are simple to use and can provide a serai-quantitative determination for ,
BTEX in water. The lower detection level is 500 ppb.
The Lab In A Bag sample extraction system provides a reliable means to prepare water
and soil samples for volatile hydrocarbon analysis. Low detection limits (10 ppb in water and 40
ppb in soil) are achievable when used with a portable gas chromatograph.
The Microsensor Systems, Inc. (MSI) gas chromatograph provides accurate and precise
quantitation for BTEX. This instrument offers the advantage of providing quantitation for
individual target analytes.
All the methods investigated can be used with few or no modifications. This document
provides guidelines for choosing proper analytical methods for specific problems. Method
performance is presented along with advantages and limitations for the procedures investigated.
iii
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PREFACE
The research described in this report was carried out by Lockheed Environmental Systems
& Technologies Company, Las Vegas, Nevada, under Contract Number 68-CO-0049 with the U.S.
Environmental Protection Agency, Environmental Monitoring Systems Laboratory, Las Vegas.
Nevada.
The authors wish to acknowledge John Zimmerman. John Curtis, Patricia Fitzpatrick. and
Patricia Amick (Lockheed Environmental Systems & Technologies Company) for their diligent
laboratory work.
iv
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TABLE OF CONTENTS
Section Title Page
I INTRODUCTION 1
A. OBJECTIVE . 1
B. BACKGROUND 1
C. SCOPE/APPROACH 2
D. METHOD SELECTION 3
II METHOD DESCRIPTIONS 5
A. ANTOX 5
1. Theory of Operation 5
2. Characteristics and Costs 5
3. Limitations 7
4. Conclusions 7
B. DETECTOR TUBES 7
1. Theory of Operation 7
2. Characteristics and Costs 9
3. Limitations 9
4. Conclusions 9
C. LAB IN A BAG 9
1. Theory of Operation 10
2. Characteristics and Costs 10
3. Limitations 10
4. Conclusions 10
D. MSI-301A ORGANIC VAPOR MONITOR 11
1. Theory of Operation 11
2. Characteristics and Cost 11
3. Limitations
4. Conclusions 11
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TABLE OF.CONTENTS
(CONTINUED)
Section Title Page
III METHOD PROCEDURES 14
A. ANTOX IMMUNOASSAY 14
1. Materials 14
2. Procedure 14
3. Calibration 15
B. DETECTOR TUBES FOR ANALYSIS OF WATER
SAMPLES 15
1. Materials 15
2. Procedure 16
3. Calibration 16
C. LAB IN A BAG 17
1. Materials 17
2. Procedure 17
3. Calibration 18
D. MSI-301A ORGANIC VAPOR MONITOR .19
1. Materials 19
2. Warm Up and Blank Measurement 19
3. Calibration 19
4. Operation 20
IV METHOD PERFORMANCE 21
A. ANTOX IMMUNOASSAY 21
1. Method Detection Limit 22
2. Accuracy 23
3. Precision 27
4. Ruggedness 27
5. Training Required 27
6. Cost 28
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TABLE OF CONTENTS
(CONCLUDED)
Section Title page
IV B. DETECTOR TUBES FOR ANALYSIS OF WATER
SAMPLES 28
1. Method Detection Limits 28
2. Precision 29
3. Accuracy 30
4. Ruggedness 32
5. Training Required 32
6. Cost 32
C. LAB IN A BAG 34
1. Method Detection Limit 34
2. Precision 35
3. Accuracy 36
4. Ruggedness . 38
5. Training Required 44
6. Cost 44
D. MSI-301A ORGANIC VAPOR MONITOR 44
1. Method Detection Limits 45
2. Precision 45
3. Accuracy 46
4. Ruggedness 46
5. Training Required 52
6. Cost 52
V CONCLUSIONS 53
VI RECOMMENDATIONS 54
VII REFERENCES 55
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LIST OF FIGURES
Figure Title Page
1 Antox Immunoassay BTX Kit with Special Cuvettes
and Reagent Bottles 6
2 Detector Tubes with Charcoal Scrubbing Tube, Gas
Washing Column, Detection Tube, and Air Pump 8
3 Lab In A Bag and MSI-301A Portable Gas Chromatograph
Systems 13
4 Response of the Ahtox S/R Ratio at Increasing
Concentrations. An S/R ratio of <0.85 Indicates
a Positive Response 22
5 Antox S/R Ratio Compared to Total BTEX Concentration
Determined from Field Samples 26
6 Response of Detection Tube #800-23001 to Increasing
Concentrations of Toluene in Water 31
7 Response of Detection Tube #800-28561 to Increasing
Concentrations of Benzene in Water 33
8 Concentration in Lab In A Bag Headspace Samples
Versus Spiked Water Concentrations 39
9 Concentration in Lab In A Bag Headspace Samples
Versus Spiked Soil Concentrations 41
10 Effect of Stir Time on Water and Soil Samples Containing
Benzene 43
11 Daily Measurements of a 10 ppm Gas Standard Showing
Instrument Drift and Recalibration Points 48
12 Comparison of MSI-301A Versus HP5890 for BTEX in
Soil Gas 50
viii
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LIST OF TABLES
Table Title page
1 Field Analytical Methods Reviewed for Detecting
and Quantitating BTEX 3
2 Evaluation Criteria for BTEX Field Methods 21
3 Antox Laboratory Analyses of Water Spiked with
50 and 75 ppb Toluene 23
4 Antox Analyses of Field QA Water Samples Spiked
with 25 and 100 ppb Toluene 25
5 Detector Tube #800-23001 Response to Increasing Spiked
Concentrations of BTEX in Water 29
6 Replicate Determinations of Water Spiked with
0.075 ppm Benzene and 1.25 ppm Toluene 30
7 Measurements of Lab In A Bag Headspace Samples at
1 Increasing Concentrations in Water Using the
MSI Portable GC 34
8 Measurements of Lab In A Bag Headspace Samples at
Increasing Concentrations in Soil Using the
MSI Portable GC 35
9 Replicate Measurements of Lab In A Bag Headspace
Samples at Water Spike Levels of 5,10, and
500 ppb Using the MSI Portable GC 37
10 Replicate Measurements of Lab In A Bag Headspace
Samples at Soil Spike Levels 50 and 500 ppb Using the
MSI Portable GC 38
11 Replicate Measurements of BTEX at 10 ppm Gas Using
the MSI Portable GC 46
12 Comparison of Four Field Methods 53
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LIST OF ABBREVIATIONS
AC Alternating Current
BTEX Benzene, Toluene, Ethylbenzene, Xylene
BTX Benzene, Toluene, Xylene
CF Calibration Factor
cc Cubic Centimeter
cm Centimeter
cmVmin Cubic Centimeters Per Minute
°C Degrees Celsius
DC Direct Current
EMSL-LV Environmental Monitoring Systems Laboratory-Las Vegas, Nevada
EPA United States Environmental Protection Agency
FID Flame Ionization Detector
GC Gas Chromato graph
U Micron
MDL Minimum Detection Limit
MSI Microsensor Systems, Inc.
mg/L Milligram Per Liter
mL Milliliter
nm Nanometer
%RSD Percent Relative Standard Deviation
PID Photoionization Detector
ppb Parts Per Billion
ppm Parts Per Million
QA Quality Assurance
S/R Ratio Sample/Reference Ratio
SAW Surface Acoustical Wave
SITE EPA Superfund Innovative Technology Evaluation Program
TOVD Total Organic Vapor Detector
TRIS Tricyanoethoxypropane
VOA Volatile Organic Analysis
VOC Volatile Organic Compound
x
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SECTION I
INTRODUCTION
A. OBJECTIVE
The purpose of this study was to select, then evaluate, field methods for detecting and
measuring benzene, toluene, ethylbenzene, and xylene (BTEX) in soil, water, and gas samples.
For each field method selected for this study, accuracy and precision were compared to
standard laboratory methods. Methods were also evaluated based on ease of use, cost per sample
and/or cost of equipment, and minimum detection limits (MDLs). This report includes detailed
descriptions of each method (Section II), step-by-step descriptions of method procedures (Section
III), a discussion of method performance (Section IV), conclusions (Section V), recommendations
(Section VI), and a reference list (Section VII).
B. BACKGROUND
Aromatic hydrocarbons such as BTEX are common contaminants at military installations due
to spillage of hydrocarbon fuels and leakage of storage tanks. Cleanup of these contaminated areas
requires numerous chemical analyses for site characterization and remediation monitoring. The most
commonly used traditional techniques for measuring volatile compounds involve the collection of
field samples for shipment to an analytical laboratory. This process is time consuming and costly.
In addition, sample handling and transport increase the potential for error, especially for volatile
organic compounds (VOCs), which are easily lost during each manipulation of the sample. Field
screening and field analytical methods are faster and potentially more precise than traditional
techniques for gathering data to evaluate remediation efforts. Using state-of-the-science field
analytical techniques, remediation efforts can be monitored for a fraction of the cost of traditional
laboratory-based analytical techniques.
Many field analytical instruments are commercially available. However, reliable
performance data are lacking for many of these instruments. Available performance data are usually
provided by the manufacturer and support the manufacturer's claims about the device. These claims
are sometimes unrealistic. Many of these instruments and the data they produce have not been
thoroughly examined by the scientific community.
Total Organic Vapor Detectors (TOVDs) are commonly used for field analysis. A number
of hand-held portable detectors are available for the detection of BTEX vapors. Most of these units
use either a photoionization detector (PID) or a flame ionization detector (FID). The PID is quite
sensitive to aromatic hydrocarbons, but does not respond to light hydrocarbons such as methane.
The FID, although not as sensitive as the PID, is useful for applications in which measurement of
a broader range of analytes is desired. Gas Chromatography (GC) has also been extensively used
for field analysis of BTEX, and a number of field-portable GC units
I
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are available from various manufacturers. Chromatography offers the advantage of separating and
quantitating individual compounds. The TOVD and GC can be used to analyze water or soil samples
if a preparation procedure, such as a headspace technique, is used to transfer the volatile components
to the vapor phase.
Other methods are available for field BTEX detection. Many of these techniques are
established analytical methods recently adapted for field BTEX detection. For example,
immunoassay techniques, commonly used by medical technologists to monitor drug levels in clinical
patients, have recently been commercially introduced for analysis of environmental samples (I).
Detector tubes have been used for years to monitor ambient air for industrial hygiene. A simple
extraction apparatus allows detector tubes to be used for analysis of water samples (2,3,4). These
methods represent practical alternatives to more expensive laboratory methods for analysis of
environmental samples.
C. SCOPE/APPROACH
The first phase of the study involved identifying field analytical methods currently used and
available for investigators. Only methods applicable to BTEX were considered. A computer
literature search was conducted to gather information on the full scope of techniques now used for
BTEX analysis. Methods in the research phase and not ready for routine monitoring activities, such
as fiber optic chemical sensors, were not considered for this evaluation. Commercial vendors were
identified by scanning advertisements in trade journals and by contacting field investigators. Product
literature and specifications were obtained from vendors and reviewed for matrix applicability and
MDLs. A summary of currently available commercial methods, along with manufacturer's
specifications, is presented in Table 1.
Data generated by use of field screening methods were compared to laboratory data obtained
by using GC with a PID according to the U.S. Environmental Protection Agency (EPA) Method
8020 (5). All analytical techniques were conducted within standard quality assurance (QA)
guidelines.
A common problem in evaluating field detection methods is the natural variation in
contaminated sites. A single location can yield a wide variety of soil types and characteristics that
create a masking variation in samples used in the evaluation of a method. To better determine and
minimize matrix variability, some test procedures were performed on reconstituted soil columns and
in water matrices that were prepared in the laboratory. By using these relatively homogenous test
media, the investigator can usually determine subtle characteristics of a method without the
confounding influence of field variation.
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TABLE 1. FIELD ANALYTICAL METHODS REVIEWED FOR DETECTING AND
QUANTITATING BTEX
Method
Matrix
Minimum
Detection Limits
(ppb)
Total Organic Vapor Detector
Vapor
1,000
Water*
1,000
Soil"
5,000
Field Gas Chromatography
Vapor
5-500
Soil*
50
Water*
10
Immunoassay
Water
25
Detector Tubes
Vapor
5,000
Water*
1,000
Handby Procedure
Water
50
Soil
500
Thin Layer Chromatography
Water
2,000
Soil
5,000
Photoacoustic Spectroscopy
Vapor
40
Underground Storage Tank
Vapor
10,000
Sensors
UV-Visible Spectroscopy
Water
500
Abbreviations: ppb - parts per billion.
Matrix can be analyzed if sample preparation techniques are employed such as: static
headspace, dynamic headspace, thermal desorption, purge and trap, and solvent
extraction.
D. METHOD SELECTION
Methods were selected for evaluation if (1) the required equipment and supplies were
commercially available, (2) the procedure was cost effective, and (3) published performance
evaluations of the methodology were limited. In addition, an attempt was made to select a variety
of methods, ranging from simple, where ease of use is a more important criterion than precision and
accuracy, to more complex methods requiring some skill in instrumentation.
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Methods that can be used by a wide range of field investigators have greater utility- than
techniques requiring personnel with advanced, specialized knowledge of chemistry or electronics
For the purposes of this study, the ideal field method has a simple, easy to understand procedure, has
few mechanical or electronic components that can malfunction, is easy to calibrate, is specific and
sensitive to BTEX, is easy to operate, and is cost effective. Based on these criteria, four methods
were selected for evaluation: the Antox BTX water screen kit, detector tubes, the Lab In A Bag, and
the MSI-301A Organic Vapor Monitor. These methods are described in Sections II and III.
4
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SECTION II
METHOD DESCRIPTIONS
The field methods selected for this study are simpler, faster, and more economical than
conventional laboratory methods. Field screening methods can provide reliable analytical results
for a wide range of applications, including site characterization, remediation monitoring, and leak
detection. However, no single field method is best for ail applications. The strengths and limitations
of each technique are discussed in this section. The costs of the selected methods varied considerably
and can be presented in a variety of ways. Information is presented which will allow evaluation of
all methods on a cost per sample basis if analyst and standards costs are factored in. The major cost
for Antox and detector tubes is the kits, while the major cost for the MSI organic vapor monitor and
the Lab In A Bag is the equipment. The method descriptions presented below are in order of
increasing complexity and cost.
A. ANTOX
4
The Antox BTX Water Screen is an immunoassay for the detection of benzene, toluene, and
xylene (BTX) in water samples. The immunoassay kit contains reagents in dropper bottles with
special cuvettes (Figure 1).
1. Theory of Operation
The Antox BTX Water screen kit uses a test tube (cuvette) coated with rabbit
polyclonal antibodies that bind to and hold BTX compounds or other closely related hydrocarbons.
BTX or similar compounds in the sample will compete with the enzyme-activated analog of the
analyte for binding to the immobilized antibody: the more BTX in a sample, the less enzyme.
Substrate and chromogen are added to the cuvette and turn color in the presence of
the enzyme. This color, a pale yellow, can be measured on a photometer. The amount of BTX in
the sample is inversely proportional to the color development. By comparing each sample to a
reference sample of pure water, the relative concentration of BTX or similar compounds in the
sample can be determined.
2. Characteristics and Costs
The Antox procedure is useful for performing quick screening tests on water samples
for the determination of the presence or absence of BTX. The main advantage of the test is its ease
of use. Inexperienced operators should be able to leam the procedure with some training from an
experienced operator. The colorimetric nature of the test assures the operator that the procedure is
working properly, with only a minimum of quality control checks. As
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Figure 1. Antox immunoassay BTX Kit with Special Cuvettes and Reapent Bottles
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many as four water samples can be analyzed during the 30 minutes required to complete the anaJvsis
A single operator can comfortably process 64 samples in an 8-hour day. At present, the test can
reliably determine if BTX is present above 75 ppb. Future immunoassay kits may achieve a lower
detection limit. The cost of the equipment for this test is approximately $600.00. The cost per
sample for the test kits depends on the level of quality control, and can be as low as S9.15 if four
samples are analyzed with each control tube.
3. Limitations
The primary limitation of the test is a lack of quantitative information; the test can
only indicate if a contaminant is present, not precisely how much or exactly what compounds are
present. The test responds to aromatic hydrocarbons and other compounds containing carbon-carbon
double bonds, such as trichloroethylene and tetrachloroethylene. As a result, a positive test does not
necessarily prove the presence of BTX; rather, it indicates that some type of contamination is
present. For this reason, the test is most appropriate for screening or monitoring of BTX at sites
known to be contaminated with BTX.
4. Conclusions
Despite its limitations, the Antox procedure should be useful for many applications.
The presence of a contamination problem can be quickly determined at a field site. Screening many
samples at the field site can provide a cost-effective guideline for the selection of samples to be sent
for complete laboratory analysis. In addition, quick screening results can be used to assist a
laboratory in determining an appropriate dilution for a sample.
B. DETECTOR TUBES
Detector tubes are used to measure the concentration of a specific compound or group of
compounds in a gas sample. In the presence of the target compounds, the material in the tubes
gradually changes color or stains along the length of the tube. The longer the stain, the higher the
concentration of contaminant. Detector tubes have been used for years by industrial hygienists for
the analysis of ambient air. Using simple apparatus (Figure 2), these tubes can also be used for
analyzing water samples. The detector tubes used for this study were manufactured by DrSgerwerk
AG LObeck (Germany.) and obtained from SK.C WEST (parts # 800-28561 and # 800-23001).
1. Theory of Operation
Contaminant-bearing air is produced by bubbling scrubbed ambient air through a
water sample. Ambient air is pumped through a charcoal-filled scrubbing tube into the water sample
in a gas-washing column. The air then passes through a detector tube attached to the outflow of the
gas-washing column (See Figure 2). Chemicals in the detector tube react with
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I imne 2
I Meclor I iiIh-s with Charcoal Scruhhin|i I ubc. (las Washing Column. Detection I ube, and Air I'ump.
8
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a specific compound or group of compounds. This reaction causes the chemicals to change color
gradually from one end of the tube to the other. The length of the stain is compared to the calibration
markings on the tube to determine the approximate concentration of BTEX in the sample.
2. Characteristics and Costs
Detector tubes provide a quick and simple screening procedure for detecting volatile
organic compounds (VOCs) in water samples. The method can detect BTEX down to 0.5 mg/L
(parts per million; ppm) with a relative standard deviation of ± 20 to 30 percent. The procedure is
easy to lean and uses simple glassware apparatus. Since the tubes are precalibrated for air analysis,
a calibration curve must be prepared for comparing the detector tube reading with the concentration
of analyte in the water. A single operator can perform each test in approximately S minutes;
therefore, an operator can be expected to analyze approximately 100 samples in a standard working
day. The equipment required to run the test costs S890.00. The cost per sample is approximately
$20.
3. Limitations
The primary limitations of this method are potential interferences and temperature
effects. Compounds chemically similar to the component being tested can produce a color change
in the tube. The main interferences are other aromatic hydrocarbons. The tubes are calibrated for
one specific target analyte, although other aromatic hydrocarbons will also give a positive indication.
For example, a tube calibrated for toluene will respond to other volatile aromatic hydrocarbons, such
as xylene. Therefore, this method will provide an overall indication of aromatic hydrocarbon
contamination instead of levels for one specific analyte. This is a not a problem for screening
contaminated fuel sites, when the objective is to characterize the site for fuel contamination. In
addition, the temperature of the water sample can have a significant effect on the test results.
4. Conclusions
Detector tubes achieve a higher degree of quantification than the Antox method. The
operator must calibrate the method at the same temperature that the test will be run for optimum
results. Although this colorimetric method is not as sensitive or specific as instrumental analytical
methods, the simplicity of operation is a real advantage for field screening projects. The supplies
can be easily carried onto a site, with no electrical power required. The procedure is easy to
understand and learn for field technicians.
C. LAB IN A BAG
The Lab In A Bag is a sample preparation system for analyzing VOCs in the air (headspace)
above soil or water samples (Figure 3). This method provides controlled conditions for field analysis
without the need for additional equipment or supplies. The battery-powered unit and required
9
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supplies arc included in a carrying case that allows easy transportation to a field site. The Lab In A
Bag is a commercial analytical version of a Polyethylene Bag Sampling System (5,6).
1. Theory of Operation
The instrument inflates a 1-quart polyethylene bag, containing the sample, to a
specific volume with scrubbed air; the instrument then agitates the sample for a preset period
(between one to eleven minutes) to allow for the release of VOCs from the sample into the headspace
in the bag. A valve attached to the bag allows the headspace to be analyzed by a portable TOVD or
by a field-portable GC. The concentration of VOCs measured in the headspace is proportional to
the concentration of VOCs in the sample. The field-portable GC used in these evaluations was the
MSI-301A (see Subsection D).
2. Characteristics and Costs
The instrumentation provides a precise procedure for headspace analysis in the field.
The kit is lightweight, providing easy mobility to a field site. Suitable precision and accuracy can
be achieved for measuring BTEX in water samples when good operating techniques are used. The
performance for soil samples is not as good as for water due to soil matrix effects such as irreversible
binding, but the achievable data is suitable for many applications. The method is simple to perform
and includes an easy to understand operating manual. The total cost of the equipment for Lab In A
Bag is approximately $2,000.
3. Limitations
This method requires an instrument for measuring the concentration of analyte in the
headspace of the bag; therefore, it requires two calibration steps: one for the detection instrument
and one to correlate the headspace concentration to the concentration of analyte in the matrix.
Although a calibration curve can be prepared in a laboratory prior to analyzing samples in the field,
it is best to perform calibration in the field because field conditions can affect the response of the
instrument. The Lab In A Bag has no temperature control, so the method should be calibrated at the
same temperature as field measurements will be taken.
4. Conclusions
This device provides a simple, portable sample preparation capability for headspace
analysis. Headspace techniques are commonly performed in field screening studies, but usually with
little quality control. Typically, an organic vapor meter is waved over a sample in whatever
container (if any) is available. Lab In A Bag provides controlled conditions for headspace analysis
without the cost of laboratory-grade instrumentation. When used in conjunction with an appropriate
detector, water and soil samples can be analyzed at the low ppb levels.
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D MSI-301A ORGANIC VAPOR MONITOR
The MSI-301A Organic Vapor Monitor (Figure 3) is a field-portable, commercially available
GC for the analysis of specific VOCs. This model is designed to detect BTEX. The instrument
provides controlled conditions for field analysis of soil or water sample headspace or soil gas without
reqwnng any additional equipment or supplies. The unit can be operated on alternating current (AC)
or battery (DC) power and uses scrubbed ambient air as carrier gas.
1. Theory of Operation
A gas sample is injected into the GC. The sample passes through a heated column,
separating volatile compounds according to molecular weight: the lightest VOCs move the fastest
and reach the detector first. The vapors are detected at the output of the column using a solid-state
surface acoustical wave (SAW) detector. Each vapor is identified by its retention time (length of
time required to travel through the column) compared to the retention times of known standards of
the same compounds. The quantity of vapor is proportional to the signal produced by the detector.
2. Characteristics and Cost
This GC can provide reliable results for the analysis of BTEX in a field situation. The
GC uses ambient air for carrier gas, providing an advantage over field-portable GCs that require
compressed gas cylinders for operation. The MSI-GC operates on a 12-volt source (either a car
battery or a rechargeable battery pack), as well as on a 120-volt source. The laboratory-grade
instrument is easy to operate. The operating conditions, such as carrier flow rate and column
temperature, are pre-set and optimized for the analysis of BTEX. The operation is menu driven,
directing the operator in a step-wise fashion toward either instrument calibration or sample analysis.
An operator with little or no GC experience can analyze samples without extensive training. When
operated in conjunction with Lab In A Bag, a single operator can analyze 6-8 samples per hour or
48-64 samples in a standard working day. The instrument costs approximately S9,000.
3. Limitations
Because the system is specifically designed to detect BTEX, it lacks the versatility
of other GCs, which can be set up to analyze other compounds. Only vapor samples can be injected
into the instrument; water or soil samples require a sample preparation method, such as Lab In A
Bag.
4. Conclusions
This instrument offers the advantage of GC separations for BTEX using ambient air
as a carrier gas. The primary advantage of this instrument is its portability and ease of use.
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This instrument, when used in conjunction with a sample preparation technique such as Lab In A
Bag. provides precise, quantitative capabilities for measuring BTEX in the field. Compounds
chemically similar to BTEX may interfere with the analysis; therefore, the instrument is best used
at sites where BTEX is the known contaminant.
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"'^'"^'".1 MS,-.,„IA
" CI,r™>ialoj.ranl, Sysieins.
13
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SECTION III
METHOD PROCEDURES
This section provides a description of each method procedure. A guideline to the materials
required for each procedure is presented, along with step-by-step procedures.
A. ANTOX IMMUNOASSAY
1. Materials
The Antox immunoassay kit includes reagents and cuvette test tubes required to
perform the analysis. Five different reagents are included with the kit, each with color coded caps.
A spectrophotometer is required to measure absorbance. The spectrophotometer must have a cell
path of 1 cm, and must be capable of reading absorbance at 4S0 nm. Several models of field-
portable, battery-powered units are available, and one may be purchased from Antox. Other
materials required to perform this procedure, but not included in the kit include:
Volatile organic analysis (VOA) wwpling vials
Distilled water
200-mL liquid dispenser
Quality control samples
Minute timer
4-mL transfer pipettes
Ice chest
Cuvette holder
Test kit reagents should be stored at 2° to 8*C when not in use, except for the color
developer #2 (blue cap), which should be stored it room temperature. Before performing the test,
the color developer #1 (black cap) and the bagged cuvettes should be allowed to come to ambient
temperatures. The other reagents, including distilled water, are kept refrigerated or placed in an ice
chest cooled to near 4*C.
2. Procedure
For each set of sample analyses, a reference standard (blank distilled water) is
analyzed with the samples. As many as four samples can be analyzed, along with one reference
standard. Each reagent should be added to the reference cuvette, then the sample cuvette(s). The
elapsed time between adding reagents to each cuvette in a batch should be kept at a minimum to
avoid a variation in color development due to incubation times.
The antibody-coated cuvettes are labeled "R" for the reference and an appropriate
code (such as sample #1, sample #2, etc.) for the samples, and are set into a cuvette holder. A
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disposable syringe or transfer pipette is used to measure and dispense 4.0 mi of distilled water into
the "R" cuvette. The same technique is used to measure 4.0 mL of the sample into the appropriately
labeled cuvette. A clean pipette should be used for each sample to avoid cross-contamination.
Add 4 drops of the buffer solution (gray cap) to all cuvettes. Immediately add 4 drops
of the enzyme solution (red cap) to all cuvettes. Cap and invert cuvettes four times to evenly
distribute and mix samples. Incubate the tubes for 10 minutes in an upright position. Using distilled
water, wash and decant the cuvettes four times, discarding the contents of the cuvette after each
wash. Add 4 drops of color developer 1 (black cap) to each cuvette. Add 4 drops color developer
2 (blue cap) to each cuvette. Tap cuvettes gently to assure all solution is in the bottom of the
cuvettes. Allow tubes to sit for 5 minutes. Add 4 drops of the terminating solution (purple cap) to
each cuvette. Mix by swirling gently. The absorbance of each sample cuvette and the reference
cuvette is measured by the spectrophotometer at a wavelength setting of450 nm.
The absorbance of the sample is divided by the absorbance of the reference. If the
result is less than 0.85, the test is positive. For example, if the absorbance reading of the reference
is 1.0 and the absorbance reading of the sample is 0.5, the ratio is 0.5: the test is positive.
3. Calibration
The spectrophotometer must be properly calibrated to avoid false positive or false
negative results. The exact calibration procedure depends on the specific model of instrument;
however, this is a simple procedure for most field-portable units. A two-point calibration is required.
A zero point is set when no light is transmitted, and a 100% tranomittance point is set using pure
water.
B. DETECTOR TUBES FOR ANALYSIS OF WATER SAMPLES
1. Materials
Detector tubes are clear glass tubes filled with chemical reagents that react with a
specific compound or class of compounds. The tubes contain a scaled indicating section that
changes colors in die presence of the target compound. The length of the color change is proportional
to the concentration of the anaiyte.
The equipment required to perform this test is supplied in a kit available from
National Draeger, Inc. The tubes must be purchased separately. The equipment can also be
purchased separately, with the items specified as follow:
250-mL gas washing bottle with a frit porosity of 70-100^.
Hand-operated bellows pump. The pump should be the model specified by
the manufacturer of the detector tubw.
15
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Thin-walled glass tube, containing activated charcoal to purify the inlet air.
Thermometer to measure the ambient air and water sample temperatures.
A number of detector tubes for BTEX are commercially available. The
detector tubes used for this study were manufactured by Dr&gerwerk AG LUbeck (Germany) and
were obtained from SK.C WEST (parts # 800-28561 and # 800-23001). Pure distilled water is
required for method blanks and calibration samples.
2. Procedure
The basic principle of this method is the volatilization of the target analyte from its
aqueous solution by means of air purged through the sample, and simultaneous analysis of the
air/analyte mixture by a suitable detector tube.
First, a tube with activated charcoal is attached to the inlet port of the gas washing
bottle. The detector tubes are labeled by the manufacturer with an arrow indicating the direction of
the air flow. The end of the detector tube in the opposite direction of the arrow is opened and
attached to the outlet port of the gas washing bottle. The aqueous sample is then slowly poured into
the gas washing bottle to the 200-mL mark. The bottle is closed immediately after adding the sample
to avoid undue loss of volatile analyte. The end of the detector tube in the direction of the arrow is
opened and attached to the bellows pump. The pump is firmly squeezed the required number of
strokes (as specified by the manufacturer) for the particular detector tube. The concentration is read
as the length of color change on the detector tube scale.
3. Calibration
A calibration curve is required to determine the concentration of die target analyte
in water because the "ppm" scale on the detector tube measures concentration of the compound in
air, not water. A calibration curve is prepared for each individual gat washing bottle and for each
analyte with calibration standards at a minimum of three concentration levels. The calibration
standards are made up of water spiked with known amounts of the analyte. One of these external
standards should be near, but above, the method detection limit for the particular tube/anaiyte
combination. The concentration of the other standards should be prepared to correspond to the
expected range of concentrations of the analyte found in the samples.
16
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For each calibration standard, the ratio of concentration of analyte in the water to the
reading from the detector tubes is defined as the calibration factor (CF).
_ . ., „ Spike Concentration in Water Ug/mL)
Calibration Factor »
Detector Tube Reading
A daily calibration check is performed by analyzing a standard at a mid-range
concentration prior to the first and following the last sample of the day, whenever operating
conditions change, or whenever a change in detector tube performance is suspected.
C. LAB IN A BAG
The Lab In A Bag sample preparation procedure requires a detector to determine the
concentration of the compounds of interest When used with a portable GC, such as the MS1-301 A,
analytical results approach the precision and accuracy of laboratory methods and instruments. This
section covers the procedure for the Lab In A Bag, not the detection system.
1. Materials
The Lab In A Bag comes as a kit that includes many of the supplies required to
perform the sample preparation procedure. The kit includes a spring scale for weighing soil samples,
a graduated cylinder for measuring water samples, a micro-dispenser and glassware for preparing
standards, and miscellaneous items for collecting and analyzing the samples. The instrument and
the kit are well packaged in a rugged, air-tight carrying case suitable for shipping to remote sites.
The instrument operates on rechargeable batteries.
Other equipment and materials required to perform this procedure, but not included
in the kit, are listed below:
An organic vapor detector such as a portable GC, an FID, or a PID. This
detector must be connected to the Lab In A Bag with a connector tube.
One-quart heavy-duty polyethylene freezer bags with zipper-type closures.
Paper towels
Distilled water
2. Procedure
Use a 1-quart polyethylene freezer bag to analyze both soil and water samples.
Attach the bag to the instrument through a hole cut in the bag using the template and hole cutter
17
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provided with the instrument. Slip the bag onto a brass fitting on the instrument. A knurled nui wiin
a gasket on the brass fitting is tightened to provide the bag with an air-tight seal.
First inflate the bag while empty to pressure test the bag to ensure it does not leak,
then flush the bag and instrument pf any residual contaminants. Inflate the bag as follows:
a. Zip the bag closed.
b. Set the instrument controls as follows:
(1) Turn the toggle switch to ON.
(2) Turn the upper valve to VENT TO ATMOS.
(3) Turn the lower valve to PURGE OR FILL.
c. Push the FILL button and release. A red pilot lamp will light while the bag
is filling. This red light will turn off when the bag is sufficiently filled. If the
bag will not inflate within 1 minute, there is probably a leak in the bag.
Reseat the bag by removing it from the brass fitting and reattach it Open the
bag and zip it closed carefully. If the bag still will not inflate, it should be
discarded.
If the bag properly seals, the instrument is ready to analyze a sample. Reopen the bag
and quickly place the sample and a magnetic stir bar into the bag. For a water sample, use 100 ml.
For a soil sample, place 25 grams into the bag along with 100 ml of deionized water. Zip the bag
to close immediately after adding the sample and stir bar. Fill the bag with air by pushing the STIR
button. Care must be taken to assure the stir bar is property centered on the magnetic stir plate, or
the bar will not spin properly. Some manual manipulation for proper placement may be necessary.
The stir time and speed can be optimized for a particular sample type by using the optimization
procedure in the instruction manual. For most applications, a stir time of 5 minutes is sufficient
At the end of the stir cycle, a beeper sounds and a green light flashes. Turn the toggle
switch to OFF. Immediately turn the upper valve to SAMPLE to allow the headspace air to be
sampled and analyzed by the GC or TOVD.
3. Calibration
Calibrate the detector before calibrating the Lab In A Bag. The procedure for
calibrating the MSI (which was used in this analysis) is described in Subsection D-3.
The Lab In A Bag procedure is calibrated with external standards. A series of
standards at several concentrations are prepared in a matrix similar to that of the samples and
analyzed using the routine procedure for sample treatment. A calibration curve is prepared by
comparing the response of the detector with the concentration of the spiked standards.
18
-------
D. MSI-301A ORGANIC VAPOR MONITOR
The MSI-301A Organic Vapor Monitor is a field-portable, commercially available GC
designed for the analysis of specific VOCs. This model is set up for the detection of BTEX. The
unit can be operated on AC power or battery power. Scrubbed ambient air is used as the carrier gas.
1. Materials
The MSI-301A is a field-portable GC using a solid-state proprietary surface
acoustical wave (SAW) type detector. The carrier gas is ambient air passed through a charcoal
scrubber. The column is 1/8 of an inch by 43 inch 10 percent tricyanoethoxypropane ("TRIS") on
80/100 mesh Supelcoport The column is kept at an isothermal 65°C. The carrier flow rate is about
30 cm3/minute. The gas sample is first concentrated by the instrument using a Tenax trap. After
absorbing onto the Tenax at ambient temperature, the trap is heated to 140°C, desorbing the analytes
onto the column. These parameters cannot be changed by the operator. A charcoal filter that
attaches to the inlet port is supplied with the instrument for analyzing system blanks. The GC is
calibrated using gas standards, which can be commercially obtained. Analytical results are stored
on an internal data logger, which can be downloaded onto a serial printer or a computer.
2. Warm-Up and Blank Measurement
The GC must be allowed to wann-up for 30 minutes before operating to permit time
for the column oven to achieve the proper operating temperature. Before analyzing any samples, an
instrument blank and calibration standard are analyzed to insure that the instrument is operating
correctly. The instrument blank is analyzed by attaching the charcoal scrubber to the inlet of the
instrument and pressing " 1 "RUN" on the instrument keyboard. A system menu will guide the
operator with specific options, such as report type. Reports can be simple, including only the name
of the compound with the concentration, or more detailed with retention times and peak areas
included. The analysis takes about 6 minutes for a complete run. The results are displayed on the
from instrument display or on a printer, if attached. The blank sample should be zero or less than
the MDLs. Carryover from previous samples may prevent zero readings for the blank. For very low
detection limits (< 10 ppb), two blank runs are generally required to flush the system of any trace
amounts of BTEX normally present in the atmosphere.
3. Calibration
After a blank has been successfully analyzed, a calibration standard is run by pressing
"2-CALIB" on the keyboard. The menu will prompt the user to enter the concentration of the
standard calibration gas and to connect the gas standard to the instrument. After the calibration gas
has been analyzed, the operator is prompted with new calibration factors and instructed whether or
not to enter the new factors into the instrument. If the new factors vary significantly from the
previous factor* (i.e., a difference of greater than 25 percent), this may be an indication of a problem.
19
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In this case, the calibration standard should be reanalyzed. When duplicate calibration standards
produce response factors within 10 percent of each other, the system is ready to analyze samples.
4. Operation
Once the instrument has been calibrated, it can be used to measure vapor samples.
The samples can be introduced into the MSI directly from a headspace generator such as Lab In A
Bag. A direct injection can be made using a 10-mL syringe or smaller, or an internal pump can be
used to automatically pull in a sample from a port on the front of the panel. The system queries the
operator for the desired selection. Calibration must be performed using the same technique as the
injection mode. For example, the same size syringe must be used for calibration as for sample
injection.
20
-------
TABLE 3.
ANTOX LABORATORY ANALYSES OF WATER SPIKED WITH 50 AND 75
ppb TOLUENE
SAMPLE #
S/R RATIO 50 Dob
FLAG
S/R RATIO 75 oob
flag
1
0.886
-
0.752
+
2
0.850
+
0.725
+•
3
0.929
-
0.691
+
4
0.905
-
0.786
+
5
0.923
-
0.777
+
6
0.855
-
0.811
7
0.790
+
0.761
+
8
0.786
+
0.873
m
9
0.910
-
0.696
+
10
0.863
•
0.754
+
11
0.916
-
0.658
+
12
0.819
+
0.692
+
Abbreviations: ppb * parts per billion; S/R ratio * Sample/Reference ratio; -» S/R ratio of
>0.85 a negative test; + - S/R ratio of <0.85 a positive test
for toluene than the manufacturer's claim of 25 ppb. The achievable detection limit probably
depends on the individual operator, due to the timing and hand-operated measurements required of
this procedure. A person with good physical dexterity, patience, and composure will excel in
performing this procedure. In addition, the model of spectrophotometer used and environmental
conditions at the site will affect detection limits. The MDL should be verified by analyzing a spiked
standard at the desired detection limit prior to analyzing samples.
2. Accuracy
The accuracy of the method was determined by analyzing field samples, contaminated
with hydrocarbon fuels, by both the Antox test and by a laboratory GC method (6), then comparing
the results. The majority of the field samples and results were obtained from an EPA Superfund
Innovative T echnology Evaluation Program (SITE) study conducted through the EPA Environmental
Monitoring Systems Laboratory at Las Vegas (EMSL-LV) Immunochemistry Program (8). The
SITE study of the Antox kit was conducted at the same time as the evaluations for this study. The
SITE demonstration was designed to investigate the ability of the immunoassay to perform as a
portable, on-site screening method for BTX-contaminated groundwater samples. The Las Vegas
23
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Valley of Nevada provided a range of concentration levels for gasoline-contaminated groundwater.
Sample splits were analyzed on-site using the BTX immunoassay, and in the laboratory by analysis
using GC. Additional findings with respect to the BTX immunoassay evaluation may be found in
a recent EPA internal report (9).
The concentration of BTX in the environmental samples, as determined by the
laboratory GC method, is compared to the Antox results in Figure 5. Samples were analyzed in
duplicate by the Antox test, and both points were plotted separately. Sample points below the
horizontal line on Figure 5 are positive results according to the Antox tests (an S/R ratio less than
0.8S). Most of these points were measured at greater than 25 ppb with the GC method (the vertical
line on Figure 5). Likewise, most of the samples with negative Antox results show less than 25 ppb
with the GC method. A few samples show GC concentrations above 25 ppb that were not detected
by the Antox method, agreeing with the detection limit data in Tables 3 and 4.
This again indicates that the lower detection limit of the Antox test should be greater
than the 25 ppb level specified by the manufacturer. The GC concentration is a sum of the BTEX
concentrations in the water sample expressed in parts per billion. The Antox results for field samples
were rather scattered. Samples with a GC concentration near 1,000 ppb were all detected above the
lower detection limit with the Antox test with an S/R ratio varying between 0.1 to 0.7. These results
show that the method is useful as a field screening qualitative test to identify which water samples
are contaminated with BTX, but accurate quantitation is not possible.
24
-------
TABLE 4. ANTOX ANALYSES OF FIELD QA WATER SAMPLES SPIKED WITH 25 AND
100 ppb TOLUENE.
SAMPLING DATE
S/R RATIO
25 PPB
FLAG
S/R RATIO
100 PPB
FLAG
1/22/92
0.79
+
0.50
+
2/24/92
1.02
0.83
2/25/92
1.40
0.95
-
2/25/92
1.02
0.84
+
1/22/92
0.98
0.72
+
2/24/92
0.69
0.51
+
1/23/92
0.95
0.66
+
1/23/92
0.92
0.81
+
2126192
0.93
0.72
+
2/27/92
0.87
0.65
+
2/28/92
1.06
0.85
+
2/25/92
0.93
0.80
+
2am
1.00
0.72
+
2/27/92
0.91
0.68
+
2121192
0.87
m
0.68
+
Abbreviations: ppb * ports per billion; S/R ratio ¦ Sample/Reference ratio; + * S/R ratio of
<0.85 a positive test; - - S/R ratio of >0.85 a negative test.
25
-------
B 0.6
10 100 1000
GC Concentration (ppb)
Figure 5.
Antox S/R Ratio Compared to Total BTEX Concentration Determined from Field Samples.
26
-------
3. Precision
Method precision was measured at 50 and 75 ppb in the laboratory and 25 and 100
ppb in the field (Tables 3 and 4). The flag indicates an S/R ratio of <0.85, or a positive test,
while the flag indicates a negative test. The range of S/R ratios from laboratory tests at 50 ppb
was 0.929 to 0.786 (0.143 range). At 75 ppb, the range was 0.873 to 0.658 (0.215 range). Field QA
tests at 25 ppb had an S/R range of 0.69-1.40 (0.71 range); field QA tests at 100 ppb had an S/R
range of 0.50-0.95 (0.45 range). This indicates a fairly large range of response in S/R ratios to a
given concentration of toluene under field conditions. Analysis of field samples agreed with these
data.
4. Ruggedness
For each test, the sample tube was compared to a reference tube containing distilled
water, A few times the reference tube failed: the reading on the spectrophotometer was too low
(<1.0). The exact cause of this failure was not determined; however, it could have resulted from
either operator error or a bad tube. The reference tube should have an absorbance reading of between
1.0 to 1.9 absorbance units. If not, the test should be re-run. For the best reliability, the test should
be run twice for each sample, and each test should be run with a separate reference tube.
The reading of the spectrophotometer may be affected by ambient light. In other
words, direct sunlight on the instrument may produce erroneous results. A cover should be placed
over the cuvette to prevent stray light from entering the light path of the instrument. Some portable
photometers have such a cover, but others do not A tight cover should be ensured to reduce the
potential for error.
Temperature may influence the results of the test. The manufacturer recommends that
for ambient temperatures of greater than 24°C, several steps should be performed in an ice water
bath. The effect of temperature on the results of this test has not been fully investigated in this
evaluation. All laboratory tests were run between 21°C and 24°C. Field tests were performed
between 18°C and 32°C. To guarantee quality results, water spiked with toluene (or the site-specific
analyte) at the desired detection limit should be analyzed at the field site.
5. Training Required
The test is simple to learn, and easy to perform. The manufacturer includes a five-
page instruction manual with each shipment of test kits. These instructions are brief but contain
sufficient detail to properly instruct the user. Only a few hours of training should be required.
However, the operator should be aware that certain steps are critical to the successful completion of
the test Four drops, no more or less, of each reagent are required at specific times. If more drops
are added by accident the test should be discarded and repeated with new tubes. The
27
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timing of the steps is also important. As with any procedure, the test should be practiced in a
laboratory setting prior to being used at a field site.
6. Cost
The cost of performing the Antox tests depends on how the test is performed. If each
test tube is measured against a separate reference tube, the test is most reliable, but also the most
costly. The manufacturer recommends no more than four test tubes be run in conjunction with a
single reference tube. During our tests, four tubes were used with each reference tube, resulting in
a per sample materials cost of approximately $9.00 per sample. If a single test had been run with
each reference, the cost would have increased to approximately $15.00 per test. The cost for an
analyst will vary with experience, but can be factored into a cost estimation by adding the analyst's
daily wages to the cost of producing 64 tests (a typical daily number of runs). The cost of the
spectrophotometer required for the test is approximately $600.00.
B. DETECTOR TUBES FOR ANALYSIS OF WATER SAMPLES
Detector tubes have been used for years for the analysis of ambient air in industrial hygiene
applications. Using simple apparatus, these tubes can also be used for analyzing water samples
(2,3,4). Using a hand-operated pump, ambient air is purged through a water sample into a detector
tube, which changes color in proportion to the concentration of the specific analyte in the water.
This method has been reported to work for soil samples (3); however, soil was not tested for this
study, as a protocol has not yet been developed for soil samples. The concentrations of spiked water
samples for all analyses performed below were verified using an HP5890 GC and EPA Method 8020
for analysis (5).
1. Method Detection Limits
Two different tubes were evaluated in this study: Draeger tube #800-23001 calibrated
for detection of toluene, and Draeger tube #800-28561 calibrated for detection ofbenzene. The tube
evaluated for toluene is the one recommended by Draeger for water analysis. The manufacturer
claims this tube can detect toluene in water from 1 to 10 mg/L (ppm) and can detect ethylbenzene
and xylene in water at approximately the same range. However, benzene is not detected with this
sensitivity. Instead, Draeger now recommends tube #800-01231 for detecting benzene in water, with
a range from 0.5 to 5 mg/L (ppm). At the time this study was conducted, this particular tube was not
being marketed by Draeger specifically for water analysis, and was not evaluated. Tube #800-28561
was selected for use in this study because it has a lower reported detection limit for air analyses, and
was evaluated to determine if these lower detection limits could be achieved in water samples. If
successful, this tube would provide a more sensitive screening test than the tube currently
recommended by the manufacturer.
The toluene tube was found to meet the manufacturer's specifications (Table 5).
Toluene was detected from 0.625 ppm to 10 ppm in spiked water samples. Ethylbenzene was
28
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detected down to 0.625 ppm and o-xylene was detected down to 0.5 ppm using this tube.
Ethylbenzene, o-xylene, and benzene were only tested near the manufacturer's reported detection
limits and not above 1.25 ppm. Further testing of this tube with benzene was not considered useful
because the manufacturer's claims of reduced sensitivity were substantiated. Ethylbenzene and
xylene were not evaluated for linearity of response (see Section B-3) because their response at low
levels was very similar to toluene, and the manufacturer indicates that these three chemicals will
react very similarly with this tube.
TABLE 5. DETECTOR TUBE #800-23001 RESPONSE TO INCREASING SPIKED
CONCENTRATIONS OF BTEX IN WATER.
DETECTION TUBE READINGS
Spiked
Cone,
(ppm)
Toluene
Ethylbenzene
o-Xylene
0.5
—
—
40
0.625
32.5
25
—
1.25
47.5
60
65
2.5
77.5
—
—
5.0
150.0
—
—
10.0
345.0
—
—
Abbreviations: ppm ¦ parts per million; — ¦ not determined.
The benzene tube evaluated in this study stowed good sensitivity to benzene in
spiked water, ranging from 0.02S to 0.5 ppm. Although this tube has better sensitivity than the tube
recommended by Draeger, other observations suggest this tube may not be appropriate for field use
(as shown in Subsections 3 and 4, following).
2. Precision
The precision of the method was good, with the %RSD for replicate analyses below
15 percent (Table 6). Replicate analyses were performed with water spiked at 1.25 ppm of toluene
for tube #800-23001 and 0.075 ppm of benzene for tube #800-28561. The precision of reading for
the tubes is limited by the sharpness of color response within the incremental scale on the tube. The
reading on the tube should be recorded as the nearest scale line. It is possible, but difficult to
estimate, the reading between scale markings. The color stain sometimes does not have a sharp
boundary. In addition, various operators may record the measurement differently, depending on
one's interpretation of where the limit of the color stain is, further decreasing the precision of the
method.
29
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TABLE 6. REPLICATE DETERMINATIONS OF WATER SPIKED WITH-0.075 ppm
BENZENE AND 1.25 ppm TOLUENE.
Run #
Benzene Readings
Tube #800-23001
Tube Scale Reading
Toluene Readings
Tube #800-28561
Tube Scale Reading
1
4
60
2
4
50
3
3
40
4
3.5
50
5
3.5
45
6
4
50
MEAN
3.7
49.1
STANDARD
DEVIATION
0.41
6.6
%RSD
11.1
13.5
Abbreviations: ppm - parts per million; %RSD - percent relative standard deviation.
3. Accuracy
Accuracy was evaluated as a proportional response to a known spiked concentration
in a sample (e.g., see Table 5). All readings were performed in duplicate, and the linear response
plotted against concentration. If the response is linear, then the concentration in the sample can be
reliably predicted by the detector tube reading. Hie toluene tube was found to have a linear response
to increasing analyte concentration spiked in water (Figure 6). The points on this plot fall very near
a straight line. A simple linear regression could be effectively used to convert the tube readings into
concentration in ppm.
The benzene tube did not show good linearity, as shown in Figure 7. This lack of
linearity under controlled laboratory conditions suggests quantitative data could not be obtained
under field conditions. While the shape of the curve in Figure 7 could be fit to a nonlinear regression
model, this increases the complexity of analysis and would not lend itself to typical field screening
procedures.
30
-------
Toluene Tub# #800-23001
350
300
* 250
200
I
150
100
8
4
6
10
2
0
Water Concentration (ppm)
Figure 6. Response of Detection Tube #800-23001 to Increasing Concentrations of Toluene in
Water.
31
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4. Ruggedtiess
The simplicity of the method is an advantage, because minimal equipment is required.
All the supplies for the method can be carried in a carrying case. The glassware is somewhat fragile,
and care must be exercised to avoid breakage in the field.
The results of the method can be affected by the temperature of the water sample.
Method calibration should be performed at the same temperature as the water samples.
Not all types or brands of tubes are suitable for field screening tests. For example,
rubes in which high moisture content can adversely affect the color indicator are not suitable. One
of the tubes evaluated in this study (Draeger Benzene tube #800-28361) did not have a linear
response to increasing concentrations in water. The color change was hard to detect, probably due
to the effect of the high moisture content of the purged headspace. This effect could easily be
worsened in the field under variable lighting and temperature regimes. The other tube evaluated
(Draeger Toluene tube #800-23001) performed much better, although not with the sensitivity of the
Benzene tube. It is important, therefore, to use tubes specified by the kit manufacturer, or to test
tubes for linearity in a laboratory before using them in the field.
5. Training Required
The procedure is quick and simple to leam; only a few hours of training should be
required, depending upon the attitude and motivation of the trainee. Although a chemistry
background is not required to learn this procedure, some knowledge of chemicals and familiarity
with measuring processes (such as following recipes) would be helpful.
6. Cost
The cost of Draeger tubes is approximately $20.00 per test. As with the Antox test,
the cost of an analyst's wages should be added to the number of samples that can be run in a typical
day. In our tests, approximately 100 samples per day could be completed. The approximate cost
of the equipment required to the run the test is $890.
32
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Benzene Tub* #800-28561
7 ¦
¦
6
•
1
5 •
*
4 «
¦
2
s
3 •
*
£
2 ¦
1 ¦
A i
¦
«
0 •
0 0.1
0.2 0.3
0.4
0.5
Water Concentration (ppm)
Figure 7. Response of Detection Tube #800-28561 to Increasing Concentrations of Benzene
in Water.
33
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C. LAB rN A BAG
Lab In A Bag is a sample preparation method for analyzing water or soil samples for VOCs.
The Lab In A Bag is a low-cost instrument designed to use the polyethylene bag sampling system
as a headspace method (6,7). The concentration of all samples reported in this section were verified
using an HP5890 GC and EPA Method 8020 for analysis (5).
1. Method Detection Limit
This method provides relatively high sensitivity for a field method. The method was
found to provide gas headspace that allowed detection of 10 ppb BTEX in water samples (Table 7)
and 40 ppb BTEX in soil samples (Table 8). This detection limit was achieved when using the Lab
In A Bag with the MSI-301A GC (see Subsection D). The detection limit should be lower for the
more volatile analytes. The more volatile the compound, the more it will move into the bag
headspace. Some of the analytes could not be detected reliably at the low ppb levels; notably, xylene
was not detected until SO ppb in water and 200 ppb in soil. At these low levels, the analytes are
probably irreversibly absorbed into the polyethylene bag or complexed within the soil matrix. The
results for ethylbenzene are somewhat erratic near the detection limit. This may be due to
contamination present in the bags or in the water used for the experiment
TABLE 7. MEASUREMENTS OF LAB IN A BAG HEADSPACE SAMPLES AT
INCREASING CONCENTRATIONS IN WATER USING THE MSI PORTABLE
GC.
MSI Headspace Concentration (ppm)
Spike Concentration
in Water (ppm)
Benzene
Toluene
Ethylbenzene
o-Xylene
0.0
0.012
0.003
0.071
0.000
0.003
0.071
0.010
0.055
0.001
0.0075
0.125
0.021
0.000
0.001
0.010
0.19S
0.044
0.146
0.007
0.050
1.054
0.464
0.811
0.211
0.200
4.41
2.36
1.99
1.53
0.500
10.52
546
4.16
361
Abbreviations: ppm ¦ para per million.
34
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TABLE 8. MEASUREMENTS OF LAB IN A BAG HEADSPACE SAMPLES AT
INCREASING CONCENTRATIONS IN SOIL USING THE MSI PORTABLE GC.
Headspace Concentration (ppm)
Spike Concentration
tn Soil (ppm)
Benzene
Toluene
Ethylbenzene
o- Xylene
0.000
0 008
0.001
0.090
0000
0.040
0.041
0.014
0.125
0.003
0.200
1.153
0.492
0.722
0.233
0.800
4.847
3.082
4.865
3.704
2.000
10.882
6.191
5.961
4.596
3.000
14.622
8.316
7.431
6.153
4.000
18.249
10.163
9.311
7 854
Abbreviation*: ppm * parts per million.
As a comparison to the Lab In A Bag procedure, the laboratory method using purge-
and-trap technology can achieve detection limits of 0.2 ppb in soil and water (S). The achievable
detection limits for the Lab In A Bag method will vary with the matrix type, especially for soil. The
organic content, soil type, and sampling methods can affect the sensitivity of the method. Before
analyzing samples, the detection limit should be verified by spiking a contaminant-free matrix at a
level near the desired detection limit, then analyzing the spiked samples.
2. Precision
The method can provide good precision for water samples, as shown in Table 9,
which lists the results of replicate water samples spiked at 5 ppb, 10 ppb, and 500 ppb. At the 500
ppb spike level, the precision was less than or very close to 5 percent for all analytes. The precision
is best for the more volatile analytes, with benzene showing less than a one %RSD at 500 ppb.
Precision was also good at the 10 ppb level for water (near detection limit) with the exception of
xylene (the least volatile component), which showed a 49 %RSD. Benzene, the most volatile
component, shows a %RSD of less than 10 percent, which was similar to ethy(benzene (11.5
percent). Toluene was somewhat intermediate in precision with a %RSD of 27.
The precision of the method for soil samples was not as good as for water samples
(Table 10). The precision ranged between 4.7 percent and 38 percent, but was not dramatically
better at high concentrations (500 ppb), as compared to near detection limit concentrations.
Ethylbenzene appears to have a somewhat higher detection limit in our soil matrix than the other
compounds (Table 10). Results for this compound were also somewhat erratic in water samples near
the detection limit (see Tables 7 and 9).
35
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3, Accuracy
In a similar manner as detector tubes, the accuracy of the Lab In A Bag procedure
depends on the concentration of the volatile compounds in the bag headspace (gaseous phase) being
proportional to the original concentration in the sample. If the sample and headspace volatile
concentration is directly proportional, then the method accuracy should be high.
The linearity of the Lab In A Bag method was evaluated in the laboratory by
analyzing water and soil spiked with increasing levels of BTEX. Water was spiked at four different
levels; the results are illustrated in Figure 8. Soil was spiked at six different levels, and the results
are shown in Figure 9. The water samples show good linearity of matrix concentration with Lab In
A Bag headspace concentration. This linearity is similar to that of the laboratory purge-and-trap
method (5). The linearity using soil samples was not as good as for water samples. This was
probably a function of soil matrix effects, which will reduce the accuracy of headspace sample
analyses.
36
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TABLE 9. REPLICATE MEASUREMENTS OF LAB IN A BAG HEADSPACE SAMPLES
AT WATER SPIKE LEVELS OF 5, 10. AND 500 ppb USING THE MSI
PORTABLE GC.
MSI HEADSPACE CONCENTRATION (ppm)
Spike Cone,
(ppb)
Benzene
Toluene
Ethylbenzene
o-Xylene
5
0.067
0.009
0.000
0.000
5
0.097
0.013
0.164
0.002
5
0.070
0.009
0.000
0.001
MEAN
0.078
0.010
0.055
0.001
%RSD
17.3
18.2
141.4
81.6
10
0.206
0.071
0.185
0.014
10
0.161
0.045
0.150
0.006
10
0.188
0.031
0.138
0.005
10
0.188
0.038
0.135
0.006
10
0.197
0.040
0.138
0.007
10
0.221
0.044
0.133
0.005
10
0.202
0.038
0.142
0.003
MEAN
0.195
0.044
0.146
0.007
%RSD
8.9
27.1
11.5
49.4
500
10.580
5.538
4.331
3.945
500
10.601
5.280
3.89
3.346
500
10.458
5.330
4.074
3.553
500
10.431
5.606
4.364
3.884
500
10.532
5.570
4.151
3.679
MEAN
10.52
5.46
4.16
3.68
%RSD
0.6
2.4
4.2
Abbreviations:
ppb * parts per billion; ppm *
standard deviation.
parts per million; %RSD
* percent relative
37
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table 10.
REPLICATE MEASUREMENTS OF LAB IN A BAG HEADSPACE SAMPLES
AT SOIL SPIKE LEVELS OF SO AND 500 ppb USING THE MSI PORTABLE GC.
MSI HEADSPACE CONCENTRATION (pprn)
Soil Cone,
(ppb)
Benzene
Toluene
Ethylbenzene
o-Xylene
50
0.241
0.071
0.000
0.020
50
0.162
0.057
0.000
0.015
50
0.257
0.063
0.000
0.027
50
0.226
0.052
0.000
0.021
50
0.312
0.078
0.000
0.030
MEAN
0.240
0.064
0.000
0.023
%RSD
20.3
14.3
0.0
23.2
500
1.921
0.408
0.415
0.124
500
1.449
0.262
0.098
500
1.331
0.164
0.070
500
3.193
0.359
0.466
0.208
500
2.572
0.355
0.444
0.184
MEAN
2.093
0.310
0.442
0.137
%RSD
34.6
28.0
4.7
38.1
Abbreviations: ppb * parts per billion; ppm * parts per million; %RSD ¦ percent relative
standard deviation.
4. Ruggedness
The operator should be confident that the analytes in the bag have reached
equilibrium between the liquid and vapor phase before analyzing. The manual suggests that the
operator determine the proper stirring time for a particular standard substance or site contaminant
by running a series of identical samples through the Lab In A Bag, using different stirring times for
each sample. Figure 10 is a graph of instrument response versus stirring time for a water sample and
for a soil sample spiked with benzene. Other analytes (toluene, ethylbenzene, and o-xylene) showed
similar curves. These results show that a stir time of 5 minutes resulted in a stable gas-phase sample
for our experimental conditions.
38
-------
Benzant
100 200 300
Watar Concentration Ippb)
400
500
Toiuen*
100 200 300
Water Concentration (ppb)
400
500
Figure 8. Concentration in Lab In A Bag Headspace Samples Versus Spiked Water
Concentrations (Continued).
39
-------
Ethyl Benzene
200 300
Water Concentration (ppb)
o-XyJene
200 300
Water Concentration (ppb)
Figure 8. Concentration in Lab In A Bag Headspace Samples Versus Spiked Water
Concentrations (Concluded).
40
-------
Benzene
1.5 2 2.5
Soil Concentration (ppm)
3.5 4
Toluene
Soil Concentration (ppm)
Figure 9. Concentration in Lab In A Bag Headspace Samples Versus Spiked Soil
Concentrations (Continued).
41
-------
Ethyl Banzane
1.5 2 2.5
Soil Concentration (ppm)
o*Xyi«n»
0 0.5 1 1.5 2 2.5 3 3.5 4
Soil Concentration (ppm)
Figure 9. Concentration in Lab In A Bag Headspace Samples Versus Spiked Soil
Concentrations (Concluded).
42
-------
Lab In A Bag Stir Times
•— Watar Spikad At 1 ug/mL
Soil Spikad At 2 ug/mL
Figure 10. Effect of Stir Time on Water and Soil Samples Containing Benzene.
43
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Sample carry-over can be a problem when analyzing low-level contaminated samples
immediately after analyzing a high-level sample. A blank sample should be analyzed after a high-
level sample to guarantee that the system is completely flushed of contaminant.
Temperature fluctuation can have an adverse affect on the analytical results. Wanner
temperatures will cause more of the volatile compounds to move into the bag headspace than would
be present at cooler temperatures. The instrument has no temperature control. For the most accurate
results, calibration standards should be run at the same temperature as samples.
Sometimes the bags leak. If the bag does not appear to be fully inflated after the stir
equilibrium time, the bag may have leaked and the sample should be discarded. This problem may-
be avoided by checking for bag leakage prior to analysis by pressure testing the bag using the
procedure presented in Section III C. 2. Soil samples can be more of a problem than water samples.
Soil particles can prevent a tight seal of the bag. Sometimes it is difficult to start the stir bar spinning
in the soil sample. If this happens, the bag must be manipulated, mixing the soil and water enough
to allow for proper stirring. Manipulation of the bag may increase the chances of creating a leak in
the bag.
5. Training Required
The operator's manual included with Lab In A Bag is very simple and easy to use.
Each step of the procedure is accompanied by a photograph. In addition to the step-by-step
procedures for analyzing soil and water, the manual includes a discussion of the theory of operation
and helpful hints on sampling and calibration. Though the test is simple to perform, an operator
should spend several days in a laboratory setting to become familiar and confident with the operation
of the system. This will maximize the reliability of field results obtained.
6. Cost
The system costs approximately S2,000. Other costs associated with this technique
include standards and analyst's time. Costs of standards are quite variable, depending on the analyte
and the purity requested. In our experience, a headspace sample can be prepared in approximately
5 minutes. Depending on the experience of the laboratory analyst, 6-8 samples per hour can be
prepared and analyzed. As with detector tubes, the cost per sample using Lab In A Bag and a
suitable detector could be estimated by factoring the cost of an analyst into the number of samples
that can be processed per day (48-64 samples per day).
D. MSI-301A ORGANIC VAPOR MONITOR
The MSI-301A Organic Vapor Monitor is a field-portable, commercially available GC
designed for the analysis of specific VOCs. This model is set up for the detection of BTEX. The
instrument provides controlled conditions for field analysis of soil-gas or water and soil headspace
44
-------
without requiring large amounts of equipment or supplies. The unit can be operated on AC power
or battery power using scrubbed ambient air as carrier gas.
1. Method Detection Limits
The instrument is quite sensitive to BTEX, with a lower detection limit of 1 ppb (by-
volume) in air. The accuracy of measurements in the low ppb range is hard to verify because
accurate gas standards are difficult to prepare and verify in this range. However, the instrument
reliably measures relative levels of BTEX in ambient air present in the low ppb range. The upper
measurement limit of this device is about 100 ppm. Higher concentrations of BTEX could foul the
detector and should not be introduced into the instrument, as recommended by the manufacturer.
2. Precision
Instrument precision was found to be quite good for analyses performed within the
same day (see Tables 9 and 10). The results of replicate gas standard samples at 10 ppm analyzed
with the MSI-301A displayed %RSD for all analytes of less than 5 percent, comparing quite
favorably to laboratory-grade GC instrumentation (Table 11).
Day-to-day measurements had greater variability than within-day measurements.
Benzene was quite reproducible from one day to the next; toluene and ethylbenzene showed up to
20 percent variation from one day to the next, and o-xylene showed up to 40 percent change within
one day (Figure 11). The detector can change its sensitivity depending on how long the instrument
is left on. This change of sensitivity is not a problem if the instrument is calibrated on at least a daily
basis.
45
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TABLE 11. REPLICATE MEASUREMENTS OF BTEX AT 10 ppm GAS USING THE MSI
PORTABLE GC.
MSI CONCENTRATION (ppm)
MEAN
°/«RSD
Benzene
Toluene
Ethylbenzene
o-Xylene
11.29
10.04
10.31
10.31
10.67
10.02
10.23
10.05
10.13
9.60
9.73
9.51
10.23
9.82
9.90
9.64
10.24
10.27
10.57
10.45
10.16
10.00
10.12
9.83
10.15
10.38
10.78
11.01
10.10
10.04
10.19
10.02
10.13
9.91
10.04
9.82
10.19
10.10
10.37
10.26
10.20
10.14
10.35
10.24
10.02
10.02
10.27
10.08
10.29
10.03
10.24
10.10
3.3
1.9
2.6
3.8
Abbreviations: ppm * parts per million; %RSD ¦ percent relative standard deviation.
3. Accuracy
The accuracy of the MSI was determined by analyzing replicate samples of a gas
standard (Table 11) and samples taken from a soil column and analyzed on both the MSI and a
laboratory GC (Hewlett-Packard 5890). As seen in Table 11, the mean values for measurements of
the gas standards on a single day were close to 10 ppm with little variance. This demonstrates that
once calibrated to a known gas standard, the instrument reliably reproduced those measurements
during a single days' operation.
A soil column was built for this project to provide a homogeneous soil matrix for
analysis. The column was spiked by flowing a gas-phase standard containing 10 ppm BTEX through
the column. While the column was being spiked with BTEX, the soil gas was monitored by the MSI
and the HP5890 at the same time until the column had become saturated. The two GCs showed very
good correlation (Figure 12). The diagonal line in Figure 12 represents an ideal correlation (i.e., the
46
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results from the two instruments are exactly the same). Most of the points for benzene and toluene
fall close to this line. The spread of difference between the two instruments was larger as the
concentration approached 10 ppm. The cause of the differences cannot be determined from this
experiment because the true value of gas concentration within the columns was not known. The
ethylbenzene and o-xylene generally fall above the ideal line (i.e., the MSI reading was higher than
the HP-5890). This may indicate a bias toward slightly higher readings for the MSI.
4. Ruggedness
The MSI-301A is designed for hands-on operation for personnel without extensive
experience in analytical instrumentation; therefore, it is simpler to operate than most GCs. The
instrument was transported by airplane for demonstration, and was moved and recalibrated numerous
times. It appears to be quite well suited for field work. Most of the instrument conditions are pre-set
for BTEX analysis, thus requiring very little extra work on the field analyst's part. An extensive
manual is included with the instrument, which can provide help in troubleshooting the instrument
if a problem develops.
47
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Benzene
2-06 2-12 2-13 2-18 2-20 2-20 2-21 2-24 2-25 2-25 2-26 2-26 2-27
Data
Toluene
u
13
I 12
i 11
1 10
S 9
1 8
e
* e • *
" * ¦ ¦ ¦
¦ ¦
¦
7
m
6 4
2-06 2-12 2-13 2-18 2-20 2-20 2-21 2-24 2-25 2-25 2-26 2-26 2-27
Data
Figure 11. Daily Measurements of a 10 ppra Gas Standard Showing Instrument Drift and
Recalibration Points (Continued).
48
-------
Ethyl Benzene
2-06 2-12 2-13 2-18 2-20 2-20 2-21 2-24 2-26 2-25 2-26 2-26 2-27
Date
o-Xyl«nt
i
14
13
12 ¦
11
10
9
8
7
¦ •
2-06 2-12 2-13 2-18 2-20 2-20 2-21 2-24 2-2S 2-25 2-26 2-26 2-27
Data
Figure 11. Daily Measurements of a 10 ppm Gas Standard Showing Instrument Drift and
Recalibration Points (Concluded).
49
-------
Benz«n«
35
2
4 6 8
HP S890 Concentration (ppm)
HP 5890 Concentration (ppm)
Figure 12. Comparison of MSI-301A Versus HP5890 for BTEX in Soil Gas. The Diagonal
Line on the Plot Represents an Ideal Perfect Correlation Between the Two
Instruments (Continued).
50
-------
Ethyl Benzene
s
55
2
4 6 8
HP 5890 Concentration Ippm}
10
12
o-Xylene
4 6
HP 5890 Concentration (ppm)
10
Figure 12. Comparison of MSI-301A Versus HP5890 for BTEX in Soil Gas. The Diagonal
Line on the Plot Represents an Ideal Perfect Correlation Between the Two
Instruments (Concluded).
51
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5. Training Required
Some background in instrumentation would probably be helpful in learning to operate
this instrument However, the instrument is simple enough to operate that no extensive background
in chromatography or instrumental analysis is required. Carefully studying the instruction manual,
along with two or three days of hands-on experience, should be sufficient training for the operation
of this instrument.
6. Cost
The instrument costs approximately $9,000. Other major costs and potential costs
are the same as those described for Lab In A Bag, including standards and analysts time. Depending
on the experience of the analyst, six to eight samples per hour can be prepared and analyzed. The
cost per sample could be estimated by factoring the cost of an analyst into the number of samples
that can be processed per day.
52
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SECTION V
CONCLUSIONS
The Antox immunoassay test is simple to perform and can be used as a quick indicator
of BTEX contamination in water. This test provides a reliable, qualitative indicator for BTEX at
levels above 75 ppb. Although the manufacturer claims sensitivity to 25 ppb, 75 ppb appears to
be a more practical method detection limit.
Detector tubes are simple to use and can provide a semi-quantitative determination for
BTEX in water.
The Lab In A Bag sample extraction system provides a reliable means to prepare water
and soil samples for volatile hydrocarbon analysis. Low detection limits (10 ppb) are achievable
when used with a portable GC.
The MSI GC provides accurate and precise quantitation for BTEX. This instrument
offers the advantage of chromatography, allowing quantitation for individual target analytes.
Table 12 provides a summary which compares the techniques evaluated in this study.
TABLE 12. COMPARISON OF FOUR FIELD METHODS.
Method
Method Detection
Limit
Precision and
Accuracy
Training
Required
Equipment
Cost
Cost of Supplies (per
analysis)
Antox
Immunoassay
75 ppb (water)
Qualitative
Several
hours
$600.00
$9.00
Defector
Tubes
500 ppb (water)
Semi-
quantitative
Several
hours
SS90.00
$20.00
LabmaBag
10 ppb (water)
40 ppb (soil)
Quantitative
Several
days
$2,000.00
$2.00
MSI
1 ppb (air)
Quantitative
Several
days
$9,000.00
$2.00
53
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SECTION VI
RECOMMENDATIONS
All the methods investigated can be used as presently available with few or no
modifications; however, further investigations should be undertaken using these procedures under
field conditions at actual contaminated sites. Most of the data generated during this study was
produced under laboratory conditions. This data provides information as to the potential
performance of the method, although performance may vary under field conditions. Until additional
field performance data become available, the results of these field methods should be confirmed with
the results of laboratory analysis of split samples.
Calibrations should be performed on-site, as site-specific variables, such as temperature,
may alter a calibration curve from one site to another. Personnel performing the procedure should
be well versed in the method techniques prior to arrival at a field site.
These methods are best suited for use as screening procedures at sites where BTEX is a
known or likely contaminant Chemicals similar to BTEX may interfere with specific quantification.
It is recommended that samples taken from sites with unknown contaminants be initially
characterized using more exhaustive analytical approaches, such as mass spectrometry. However,
at sites with known BTEX contamination, these field screening techniques offer distinct advantages:
the lower cost allows • larger number of samples to be analyzed than could be achieved using more
refined laboratory methods, providing more thorough site characterization. Additionally, the quick
turnaround time obtained through use of these methods allows priorities to be set at a site in a more
expedient manner.
54
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SECTION VII
REFERENCES
1. Van Emon, J.M. and Mumma, R.O., eds., ImmtinochemicaJ Methods for Environmental
Analysis. ACS Symposium Series 442, American Chemical Society, Washington, DC,
1990.
2. Amick, E .N. and Zimmerman, J. H., "Evaluation of Detector Tubes for Determination of
Volatile Organic Compounds in Water," presented at Pittcon 1992, New Orleans,
Louisiana, March 1992.
3. Mussmann, B., "Analysis for Environmental Protection - Measurement of Chemical
Contaminants in Soil and Water Samples by Means of Draeger Tubes," Dracfcr
Review. Vol. 51, pp. 17-19, April 1983,
4. Bather, W., "The Draeger Air Extraction Procedure - A Rapid Test to Determine
Pollutants in Water," Draeyer Review. Vol. 61, pp. 9-17, September 1988.
5. U.S. Environmental Protection Agency, Teat Methods for Evaluating Solid Waste, pp.
8080-1 to 8010-13 and 8020-1 to 8020-14, SW-846,1986.
6. U.S. Environmental Protection Agency, Office of Underground Storage Tanks, Field
Measurements - Dependable Data When You Need It, pp. 22-28, EPA/530/UST-90-003,
September 1990.
7. Robbins, G.A., Bristol, R.D., and Roe, V.D., "A Field Screening Method for Gasoline
Contamination Using a Polyethylene Bag Sampling System," Ground Water Monitoring
Review, pp. 87-97, Fall 1989.
8. Gerlach, R.W., White, RJ., OXeary, N.F.D., and Van Emon, J.M., "Superfund
Innovative Technology Evaluation (SITE) Program Evaluation Report for Antox BTX
Water Screen (BTX Immunoassay)," EPA/540/R-93/518, U.S. Environmental
Protection Agency. (June 1993 pre-issue).
9. White, RJ., and Gerlach, R.W., "An Immunoassay for Detecting Gasoline
Components," Internal Report, U.S. Environmental Protection Agency, Fall, 1992.
55
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