United States
Environmentai Protection
Agency
Soiid Waste And
Emergency Response
{05-420}
EPA/530/UST-9Q-OQ3
September 1990
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This manual was prepared for the U. S. Environmental Protection Agency's (EPA) Office of
Underground Storage Tanks (OUST) under EPA Contract Numbers 68-01-7383 and 68-WO-
0015. OUST wishes to thank project team members who contributed to the development,
contribution made by team members who provided technical guidance and review over the
The practitioners and researchers who were interviewed for this document provided
information that was essential to the development and completion of the project. The
technical information and comments provided by these individuals (who are identified at the
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Protection Agency policy and approved for publication. Mention of trade
names or commercial products does not constitute EPA's endorsement or
recommendation for use. Other field measurement procedures may currently
exist or bi
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Page
I. INTRODUCTION .......................................... 1
II. . OVERVIEW OF FIELD MEASUREMENT PROCEDURES ............ 5
III. FIELD MEASUREMENT PROCEDURES ......................... 13
General Headspace Analysis of Soil and Water ...................... 13
Headspace Analysis of Soils and Water Using
the Polyethylene Bag Sampling System ........................... 22
Draeger Liquid Extraction for Analysis
of Water ................................................. 29
Hanby Procedure for Soil and
Water Analysis ........................................... 34
Soil Vapor Sampling and Analysis .............................. 43
IV. ANALYTICAL FIELD INSTRUMENTS .......................... 61
Flame lonization Detectors .................................... 64
Photoionization Detectors ..................................... 67
Gas Chromatographs 72
Colorimetric Detector Tubes 75
Calibration ........................................... 78
V. MANUFACTURERS AND DISTRIBUTORS
OF FIELD EQUIPMENT ............................ ..... 81
VI. GLOSSARY .............................................. 87
in
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Figure 1 Organization of Document ............................... 3
Figure 2 General Headspace Analysis of Soil or Water .................. V
Figure 3 Diagram of Static Headspace Apparatus Setup Using
Figure 4 Headspace Analysis of Soil or Water Using the
Polyethylene Bag Sampling System (PBSS) . .
Figure 5 Apparatus Setup for the Polyethylene Bag Sampling System ....... 25
Figure 6 Draeger Liquid Extraction Analysis of Water .................. 30
Figure 7 Draeger Liquid Extraction Apparatus ........................ 31
Figure 9 Hanby Procedure: Colorimetric Analysis of Water .............. 36
Figure 10 Soil Vapor Sampling and Analysis ......................... 44
Figure 11 Collection and Analysis of Soil Vapor in a Borehole
Figure 13 Soil Vapor Collection by Syringe and Analysis by GC
Figure 14 Collection of Soil Vapor in a Bag for Analysis
By Portable GC, FID, or PID ..................
Figure 15 Soil Vapor Collection and Analysis Directly
from a Vapor Probe .................................... 50
Figure 16 Soil Vapor Sampling Probe .............................. 54
IV
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Table 1
Applications of Field Measurement Procedures ...,..........'... 6
Table 3 Analytical Methods and Device Performance .................. 8
I- Summary of Analytical Device Performance ................... 9
Table 5 Optimum Colors and Concentration Ranges for Qualitatively
Identifying Types of Compounds ................„'......... 39
Table 6 Lower Detection Limits for Petroleum Hydrocarbon
Contaminants in Soil and Water ........................... 41
Table 7 Summary of Analytical Device Performance ................... 62
Table 8 Relative Response for OVA Calibrated to Methane .............. 65
Table 9 Operating Specifications of PID Instruments ................... 68
Table 10 PID Response to Different Hydrocarbon Groups ................ 69
Table 11 PID Response at Different Concentration Ranges ............... 70
Table 12 Selected Performance Characteristics of Colorimetric
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Hundreds of thousands of underground storage tank (UST) sites will need to be
Investigated over the next few years to determine if a release has occurred or to find
c< t/
out how much a release has spread. To protect ground-water resources and public
health, state and local UST personnel must evaluate these sites to determine as quickly
as possible whether corrective action must be taken. Many methods commonly used
to evaluate the degree and extent of contamination can be time consuming (as in the
use of laboratory analyses) or may not provide sufficiently accurate information for
decisionmaking (as in the use of sight-and-smell field observations). Field
measurement procedures provide an advantageous alternative to these more commonly
used site assessment methods.
Field measurement procedures result in better protection of ground-water resources by
dramatically reducing the time required to conduct a site assessment at an UST
facility. Field measurement procedures Immediately provide accurate, on-slte
information about the severity and extent of contamination. This information can be
effectively used to direct additional investigations, determine where to place-
monitoring wells, and make wise cleanup decisions.
Currently, many states and consultants stress accuracy over speed, choosing to perform
laboratory analyses of soil and water samples collected at UST sites. The results may
take as long as 45 days to come back from the laboratory, and they frequently indicate
the need for additional site sampling work. It is not unusual for this type of site
Investigation to take several months, which can unnecessarily delay the start of site
Delaying cleanup can cause significant environmental damage and make recovery of
released product more difficult with each passing day. Although the use of sight-and-
smell field observations also produces immediate measurements, these measurements
are considerably less accurate than field measurement techniques or laboratory
analyses. In addition, signt-and-smell methods pose direct health risks to the people
making the field observations.
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advantages over laboratory analyses. In many cases they may be more accurate than
laboratory analyses, which can suffer from loss of contaminants due to biodegradation
and volatilization during sample holding. For example, EP/
in the range of 10 to 35 percent can occur during a 2- to 5-'
benzene, toluene, ethylbenzene, and xyienes (BTEX) in water samples. Also, the
lower cost of field measurements can reduce the cost of investigation and allow more
extent of a release, which results in better cleanup decisions.
Currently, investigators are using a variety of field measurement techniques and
procedures to assess contamination at UST sites. This guide presents information on
field measurement procedures currently used for UST site investigations and identifies
applications and limitations of those procedures. This information is organized as
A comparative overview of the most common field measurement
procedures (Section II);
Descriptions of two general procedures and three specific procedures
Descriptions of the field instruments used in most of these proced
(Section IV);
9 A list of manufacturers and distributors of field sampling and
equipment (Section V); and
e A glossary of terms used in this document (Section VI).
Figure 1 on the next page is a flow chart illustrating how this document is orj
As you read the descriptions of the general and specific procedures, you will
of this flow chart reproduced in the left hand margins to help guide you during
of the document.
2
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The analytical field procedures described in this document represent the general types
of procedures currently being used or developed for on-site evaluation of petroleum
contamination at suspected UST release sites. Descriptions of the procedures are
based on information obtained from individuals experienced in conducting them and
who have helped develop them. There are a wide variety of field procedures currently
being used. Some procedures are very simple to conduct and are used as a quick
indicator of contamination, while other procedures are used to quantify the magnitude
of contamination. The advantages and disadvantages of each field procedure are
highlighted in this section. The information presented below will allow the reader to
compare the application, operation, and performance of each procedure relative to one
another. For detailed descriptions of each field measurement procedure, see Section
A qualitative evaluation of the performance of each procedure for different field
applications is presented in Table 1. This qualitative evaluation is based on
discussions with practitioners and, where available, on performance data. It should be
noted that documented performance data has been identified for only a few of the
procedures (e.g., dynamic headspace analysis using a polyethylene bag). Known
detection limits and performance factors for each procedure are presented in Tables
2 and 3. Procedures with little or no performance data have been evaluated
subjectively. A more quantitative or objective evaluation of these procedures can be
made when additional data become available. Table 4 summarizes performance
•factors for each analytical device.
This procedure involves collecting a soil or water sample, placing it in an air-tight
container, and then analyzing the headspace vapor using a portable analytical
instrument. Some investigators agitate the sample prior to analysis to facilitate
volatilization of organic compounds into the headspace immediately above the sample.
This is referred to as a "dynamic" headspace analysis. Other investigators conduct a
"static" headspace analysis; instead of agitating the sample, the sample is kept still (or
static) for a period of time to allow volatile compounds to collect in the container
headspace.
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(3)
Soil,
Water
Soil,
Water
Water
Soil,
Water
Soil
Vapor
'' The information presented above reflects the applications
reported by investigators interviewed tor this document
(2}
1' The VOA vial procedure developed by G. Rabbins for water
analysis performs very well in these applications.
(3> Dynamic and Static Heaefepace Analysis
O Low
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(11
(S)
So//,
So//
Yes
Vas
V '' A
(3)
reported by investigators interwiewed for this document
Dynamic and Static Headspace Analysis
High degree of interference with the Static Headspace Analysis
<4> Limited lab and field cone/a tion data a vailable
High
Medium
Low
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00
General (1)
n&ia(J&pisU&
Analysis
Polyethylene Bag
Sampling Systom
Draeger Liquid
Extraction
Hanby
Soil Vapor
FID/PI D/Colorimetric
Detector Tuba
GC
FID/PID/Colorimetric
Detector Tube
GC
Color/metric Detector
Tube
'/i//////
f/ftftffff
//////////
t////////.
//////////
FID/PID/Colorimetiic
Detector Tube
GC
W's-100's
ppb
1
ppb
Water: 0.5
Soil: 1
Water: 0. 1
/ . / / / / .
/ , / / / / /
. //•///
t / / / / f t
t f / t f /
t / / / / / /
i t t t i t f
T^TTy
r~7y~7~7™;
^Z/xLZ^L,
' / ' ' / /
'///-'A
K///X-
/ / ' ' '
• / / ' ' f
''/tt
/ / / / /
''////
f / / f t
f / / / /
ft/ /ft
'/////
/ / e / t
t t / t t i
'/////
t / f / /
fO's-tOO's
ppb
10-20
20
10-20
20
15
Soil: 45-60
Water: 10-15
10-30
15-35
Dynamic and Static Headspace Analysis
Not Applicable
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(1)
ANALYTICAL
Operational Factors
FID
Portable
PID
GC
Hanby
Colorimelric
Detector Tubes
Medium
Msdium
High
Medium
Low
1-3 times
every day
1-3 times
every day
Every
5 to 10
samples
None
None
Easy
Very
Easy
Difficult
Minimal
Maintenance
No
Maintenance
8 Detects methane
e Low oxygen levels cause flame out
8 Ambient air must be >4f/F
8 Requires battery recharga every 8 hours
8 Restricted flow rate may produce unreliable readings
® Photoionization lamp requires periodic cleaning/charging
e High relative humidity (>90%) "quenches" signal
e Interference from dust particles, nearby AC or DC Unas,
high voltaga radio wave transmitters
e Less accurate when detecting concentrations >150 ppm
e Operates under limited tamparatur@ range
8 High clay content increases sample preparation time
8 Residual water on glassware consumes catalyst
® Sunlight degrades reaction
9 Limited shall life
e High humidity' can reduce sensitivity
(1)
See Section IV A for more detais.
<2> On-site routine maintenance by the operator
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The static headspace procedure yields results that are likely to be less sensitive man
results obtained from dynamic headspace analysis. Agitating a sample will facilitate
volatilization of light hydrocarbons into the headspace of the container.
The dynamic and static headspace procedures are very simple and can be conducted
qualitative and can be used as an indicator of contamination. Limited performance
data are available for both of these genera! headspace procedures. Data that are
available indicate significant interferences from soil matrix effects.
Field analyses using the Polyethylene Bag Sampling System (PBSS) involve collecting
a soil or water sample, placing it in a reclosable freezer bag, agitating the .sample to
release vapors in the bag, and then measuring the concentration of these vapors using
an analytical field instrument. This field procedure is relatively straightforward and
easy to perform once the practitioner has been properly trained and is familiar with
the operational concepts and equipment. The procedure includes generating a
calibration curve with field standards, which is used to determine sample
concentrations and as a quality control check of analytical results.
The quality of data (precision and accuracy) obtained with this procedure is very good
for both water and soil analyses (see Tables 2 and 3). Performance data obtained
using this procedure (shown in Table 3) indicate that volatile petroleum products can
be measured in soil and water at relatively low concentrations.
Compared to most other field procedures, the PBSS
reproducible results for soil analyses. This is acco:
to the soil sample, which breaks up the soil and facilitates
organics from the soil sample into the bag headspace.
procedure provides more
by adding distilled water
This extraction procedure for field analysis of water samples involves passing a fixed
volume of air through the sample. Volatile contaminants are "extracted" from the
sample and quantified using colorimetric detector tubes. This procedure is easy to use,
gives rapid measurement, and requires only the equipment
manufactured kit.
10
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"OVERVIEW*
The volatile compounds that can be measured using this procedure depend on the type
of detection tube selected. The typical range of relative standard deviations is +20-30
percent and the procedure can measure some contaminants (e.g., benzene) at
concentrations less than 1 ppm.
Hanby Procedure for Soil and Water Analysis
«/ «/
The Hanby procedure involves extraction of aromatic compounds from soil or water
samples and colorimetrically indicates the concentration and type of contaminants
present. The color of the reacted extract solution indicates the type of compound
(gasoline, diesel, solvent), and the intensity of the color indicates the concentration of
the compound. Training and "hands-on" experience are necessary to accurately
perform these analyses and to interpret the results.
This procedure provides quantitative results with high levels of precision and accuracy
(see Tables 2 and 3). However, some practitioners have indicated that soil analysis
(especially samples containing fine clays and silts) takes longer to conduct and the
results are not as accurate as water analysis.
This procedure generally involves measuring the volatile hydrocarbon concentrations
in a soil vapor sample collected in situ by pumping (i.e., active transport) the sample
to a field instrument for analysis. There are several procedures for collecting soil
vapor samples: 1) drilling or augering a borehole and inserting the analytical
instrument probe directly into the borehole; 2) driving a hollow steel probe into the
subsurface and collecting a sample with a gas-tight syringe; 3) driving a hollow steel
probe into the subsurface and collecting a sample in a collapsible bag; or 4) driving
a hollow steel probe into the subsurface and sampling directly from the probe using
a portable analytical field instrument. Sample analysis can be conducted using a
variety of portable field instruments such as gas chromatographs and photoionization
detectors. The skill level required to perform the procedure depends greatly on the
analytical instrument selected. For example, an operator using a gas chromatograph
(GC) with a driven probe will require more training than one using a photoionization
field instrument (PID) inserted in a borehole.
Soil vapor procedures are used for a variety of applications. They are used primarily
to provide an indirect estimate of the vertical and lateral extent of contamination, to
identify areas of potentially high contamination, and to determine locations for
11
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to determine the concentration of contaminants in soil or ground water,
provide qualitative information on contaminant concentrations in soil
should be interpreted by evaluating the level of contamination relative f
results
and
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Each of the field measurement procedures is described in detail in this section.
Specific applications and performance information are presented for each
procedure. The information presented below does not critically evaluate these
procedures, but simply describes how they are conducted and presents
performance data as reported by the practitioners and researchers.
Overview
Headspace analysis is a field measurement procedure that involves collecting
a soil or water sample, placing it in an air-tight container, and withdrawing a
vapor sample for analysis using a portable field instrument. (The area between
the sample and the top of the container is the "headspace" where vapors
originating from the sample collect.) There are two general types of headspace
analysis methods: "static" and "dynamic." In the "static" method, the sample
is kept stationary for a period of time to permit volatilization of organic
compounds prior to' analysis. In some cases the sample is heated in a water
bath to promote volatilization. The "dynamic" method involves agitating the
sample container to facilitate volatilization of organic compounds present in the
e.
On the next page, Figure 2 depicts the general steps involved in conducting
both static and dynamic headspace procedures. These general steps are
described on pages 15-20. Also, detailed description of a specific type of
dynamic headspace procedure that uses a polyethylene freezer bag begins on
page 22.
As indicated in Table 1, dynamic and static headspace procedures are most
applicable for confirming the presence of petroleum contamination. The
procedures are also used to determine the source of contamination, the
placement of monitoring wells, and the limits of soil excavation. Compared
to most of the other procedures described in this document, the general
headspace procedure is not as reliable for quantifying contamination levels or
for measuring progress of ground-water and soil remediation. It is used as a
screening tool to indicate relative levels of contamination between sample
ic site.
13
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- Place in 40 ml vial
- Place in 8 to 32 oz. jar
- Fill 1/2 to 2/3 container volume
- Seal container with aluminum foil,
Teflon ™ sheet, and / or airtight lie
A!low sample to equilibrate for 5 -10
minutes out of the sun to reach ambient
- Agitate sample 15 seconds to 2 minutes
Puncture aluminum foil or other seal
and insert instrument probe 1/2 the
depth ,.
Portable field instrument (PID, FID)'
or eoSorimetric tube for detection
Record highest meter response
Puncture viaS septum with syringe and
remove headspace sample ^j
Inject sample into portable GC
Analysis time 3-15 minutes
- TOV in ppm levels for headspace
- Range of specific VOCs
(1) Precleansed and decontaminated between samples if reused.
(2) More contaminant may volatilize if the sample is allowed a longer equilibration time
(1-2 hours), or if the sample is placed in a hot water bath for 5 minutes.
(3) Calibration of instrument performed prior to beginning sample analysis.
14
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SAMPLE COLLECTION - Soils
1. The
conditions. Soil samples
a soil sample is
using any of the
by .site
.g types of
A hand auger or trowel can be used for collecting surface samples
5 of stockpiled soils;
o A split spoon sampler can be used when drilling well boreholes.
and constructing depth profiles; and
A backhoe can be used for collecting samples from the excavation
area.
2. The sample is placed in a glass container such as a Mason jar or laboratory
vial. Sample containers are cleaned prior to use and decontaminated between
samples if they are reused (as described in step 4 below). After placing the
sample in the container, the container is quickly covered and sealed with one
or more sheets of aluminum foil or Teflon sheeting (~2 mm thick) and an air-
tight, screw-on lid.
Investigators reported using containers varying in size from 8 to 32 ounces
(approximately 250 to 1000 ml). Polyvinyi chloride or acrylic bottles can be
used; however, glass containers are preferred. The type and size of sample
containers and the amount of sample placed in the containers should be
consistent for all samples taken at a particular site.
3. One-half to two-thirds of the container volume is filled with the sample.
Most investigators stated that they visually estimate the amount of sample
placed in the container and do not weigh an exact amount. One investigator
reported that 16- to 32-ounce containers filled one-half to two-thirds full with
sample yield consistent results (in terms of precision and accuracy). Another
investigator allows the headspace volume to be roughly 10 percent of the
container volume, or less if the sample is slightly heated.
15
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4. Sample containers can be
rinsing with water or rnethanol, followed by single or multiple rinses with
1. Ground-water samples are obtained from monitoring wells using a clean
used to collect ground-water samples, it is securely attached to clean nylon
cord and slowly lowered into the well. Care must be taken to avoid creating
additional turbulence in the well when sampling. When the bailer is filled with
water, it is removed from the well and the contents are poured into the sample
reuse sample jars. Surface water samples can be obtained using a glass
container.
2. The water sample is placed in a glass container such as a volatile organic
acid (VOA) bottle with a Teflon-lined lid containing a septum, or a Mason jar.
Practitioners reported using containers such as 40-ml VOA vials, or 8- to 32-
ounce (approximately 250 to 1000 ml) glass containers. Containers are
thoroughly cleaned (as described in step 4 below) prior to use. After the
sample is placed in the container, the container is sealed with one or more
sheets of aluminum foil or Teflon sheeting, and a snap-on or screw-on, air-tight
lid. Containers can be designed with'a stopcock attached to the cap. The
analytical instrument probe is connected to the stopcock with tubing to allow
direct measurement of headspace vapor from the container. Sample containers
constructed of polyvinyl chloride (PVC) or an acrylic compound can also be
used; however, glass is preferred because it is more inert than PVC or acrylic
materials, which reduces the risk of sample carryover if containers are reused.
3. The sample container is filled one-half to two-thirds with the water sample.
investigator fills the container to 99 percent of the total volume allowing 1
percent headspace. The type and size of the sample container and the amount
of sample placed in the container should be consistent for samples collected at
the same site.
4. Sample collection equipment and containers can be decontaminated by a
methanol rinse followed by single or multiple rinses of distilled water.
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SAMPLE PREPARATION AND ANALYSIS - Soil and Water
Static Headspace Analysis
1. Prior to analysis, the sample is allowed to sit for 5 to 10 minutes to reach
ambient temperature. Samples are not allowed to sit so long that condensation
forms in the container. [T. Holbrook allows samples to sit out of the sun for
at least 1 hour and not more than 2 hours. D. Jermakian places samples in a
70T (21°C) water bath for 5 minutes.]
2. Samples are analyzed using either a portable photoionization detector (FED),
portable flame ionization detector (FID), portable gas chromotograph (GC), or
colorimetric detector tubes.
3. The aluminum foil or Teflon sheet covering the sample container is pierced
with the instrument probe (refer to Figure 3). [D. Jennakian files the tip of the
instrument probe into a chiseled point to minimize the size of the hole created
during insertion.] Sample analysis is conducted just long enough for the
instrument to respond to volatile organic vapors, but not so long as to draw in
ambient air from outside of the container.
Dynamic Headspace Analysis
L Prior to analysis, the sample is manually shaken or agitated for 15 to 20
seconds. [M. Leavitt agitates the sample for 2 minutes.] The agitation period
should be consistent for samples collected at the same site. If the ambient
temperature is below 32°F (0°C), the sample should be placed in a heated
vehicle or building during agitation and analysis. A hot water bath, 75 - SOT
(24 - 27°C)S can also be used to warm the sample prior to analysis.
2. Some investigators reported allowing a period of time for development of
headspace vapors after the sample has been agitated. [J. Fitzgerald agitates for
15 seconds both at the beginning and end of the headspace development
agitation. The practice selected should be consistent for all samples taken at
site.
3. Afters
is removed
instrument
puncture the
expose the aluminum foil or Teflon seal. When the field
is re
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PI Dor FID
SAMPLING LINE
VAPOR
ALUMINUM FOIL
GLASS JAR-
VAPOR
FLOW
PID or FID
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it to a
uptake of soil
is not
one-half of the headspace depth. Exercise care to avoid
or water into the instrument probe. The instrument
Investigators who use VGA bottles obtain a vapor sample by inserting a
syringe through the vial septum, withdrawing the sample from the bottle
headspace, and injecting it into a portable GC for analysis.
METHOD RESULTS AND CALIBRATION
1. Investigators record the instrument readings using one of two methods: the
highest meter response observed within, the first 5 to 10 seconds on the
analytical field instrument is recorded; or instrument readings are taken at
certain time intervals over a set time period (usually 2 to 5 minutes), and then
the recorded instrument measurements are averaged. Results obtained from
portable field instruments are reported as total organic volatiles (TOV) in either
ppm levels or as "instrument units." If outside air is inadvertently drawn into
the sample container, vapors in the headspace will be diluted and instrument
2. Instruments are calibrated at least once a day prior to beginning sample
analysis. Some investigators calibrate instruments several times a day.
3. The time that it takes to collect a headspace sample depends on the
technique used but, generally, is in the range of 5 to 15 minutes. An additional
5 to 10 minutes as needed to perform each analysis. Sample analysis using a
portable PID or portable FID can be completed in under 5 minutes. GC
sample analysis usually takes less than 10 minutes, depending on the
compounds being identified.
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Environmental factors that adversely influence the performance of this method
include: 1) high soil moisture, 2) high organic and clay levels in soil, 3)
dissolved organics in water, and 4) the age or degree of weathering of the
the sample into the headspace. These factors influence sample analysis by
High soil moisture and high organic and clay levels in soil can limit the
amount of volatile contaminants that will volatilize into the container
headspace. The presence of dissolved organics in water can also reduce
volatilization of contaminants. Contaminants that are weathered contain fewer
volatile constituents because they have already volatilized to varying degrees
over time and, therefore, volatile contaminant concentrations will be lower than
would be expected with a fresh product release.
Little information is available on the reproducibility for this method. One
investigator reported that results for split samples analyzed using the same
instrument agreed to within ± 20 percent. The degree of soil heterogeneity in
the sample can affect sample results by an additional + 10 percent.
20
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The individuals listed below were contacted to obtain information on the
procedure that they use to collect and analyze soil and water samples. This list
Jeff Billings
John Fitzg<
Tim Holbrook
David A. Jermakian
New Mexico Environmental
Emily Pimentel
PRC Environmental Management, Inc.
PRC Environmental Management, Inc.
21
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In general, the polyethylene bag sampling system (PBSS) involves collecting
a soil or water sample, placing it in a reclosable bag, agitating the sample to
release vapor from the sample to the headspace of the bag, and measuring the
headspace vapor concentration using an analytical field instrument. Distilled
water is added to soil samples to facilitate partitioning of volatile organics from
the soil sample into the bag headspace. The reclosable bag provides a
chart depicting the general steps involved in this procedure is presented in
This headspace analysis procedure provides a means to make immediate
if contamination issues
Confirming the presence of contamination to help set priorities on
the need for more detailed contamination investigations;
.g contamination levels for
remediation, and for
samples
assess
USTs:
health and safety
of suspected leaking
determine the release source and to delineate subsurface leakage
e Determining the extent of soil excavation during tank closures or
other corrective actions.
22
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Trowel
•If
- Glass container
- 100 -300 ml of
sample water
- 25 g with 100-300 ml
Three-way valve is attached to bag through a
premade hole and sealed using Buna-N gaskets
and nuts 2 inches down from the reclosabte end
Close bag, inflate with a bicycle pump and observe
for leakage
- Sample placed in bag and inflated until taut
- Agitate 4 minutes
• magnetic stirring
• manual rocking motion
- Secure valve and bag on ringstand with clamps
- Attach instrument probe to bag valve
- Portable field instrument (PID, FID) ^or
colorimetric tubes for detection
- Portable GC syringe injection (2)
- Record highest meter response after 5 seconds
- instrument analysis time 5 - 30 seconds
- Purge valve system and check with portable field
instrument (replace tubing if carryover is detected)
- TOV in ppm levels for soil or water from calibration
curve
- Concentration range of specific VOCs
(1) Calibration curves are determined for soil and water samples prior to analysis of unknown site samples.
(2) Calibration of instrument performed prior to beginning sample analysis.
23
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OVERVIEW
PROCEDURE
DESCRIPTION
PERFOFWANCE
PRACTITIONERS
CONTACTED
Procedure Description
SAMPLE COLLECTION
The container used for preparation and analysis of both soil and water samples
preference for using Ziploc-brand freezer bags.) A hole is made in one side
of the bag, approximately 2 inches down from the reclosable end of the bag.
A three-way valve is attached to the bag and sealed using Buna-N gaskets and
lamp nuts on both sides of the hole. Figure 5 shows the components of the
bag and valve system. Before the sample is collected, the bag seal should be
leak tested by inflating the bag with ambient air (using a hand pump attached
to the valve system) until taut, and isolating the inflated bag by closing the
valve. If leakage is observed, discard the bag.
Soil
1. Before a soil
are placed into a leak-tight freezer bag
2. A soil sample can be obtained using any of several methods depending on
site conditions and depth of sample collection: hand corer or auger, power
auger, backhoe, split spoon sampler (when drilling a well borehole), or air
rotary cuttings.
3. A 25-g sample of soil is weighed out and placed in a polyethylene freezer
bag equipped with a valve system; the bag is sealed. The exact amount of
sample collected is not as important as assuring that the amount collected is
consistent for all analyses conducted at a site. The soil sample should be
collected and sealed in the bag as quickly as possible to avoid loss of volatile
constituents.
Water
1. Water samples are collected using
the sample. Ground-water samples are
a bailer which is cleaned prior to sample
be obtained directly from well pumps.
that is
from
to the source of
g wells using
samples also may
24
-------
3 - Way Ball Valve
w/1/8"NPT fittings
Valve
Handle
1/4" OD Metal
tubing •~~~~~
DUD
1/4" OD Metal tubing
Silicon or Tygon
Connectors
(1/8"NPTto 1/4"
compression fittings)
25
-------
"-DYNAMIC HEADSPACE - POLYETHYLENE BAG*
sample bag using a volumetric flask. Sample volumes of 300 ml tend to yield
more consistent results than 100 ml samples. Samples larger than 300 ml may
prove to be difficult to agitate. The sample volume used should be consistent
for all samples analyzed at a site to ensure comparable results.
1. Immediately after sample introduction, the bag is inflated using an air pump
until just taut. The bag is then isolated by closing the valve. Following
isolation, the sample bag is manually agitated with a rocking motion or agitated
with a magnetic stirrer for 4 minutes.
2. Following agitation, the instrument probe (e.g., portable PID, FID, or GC)
that detects total organic volatiles (TOY) is attached to the bag valve system
using polyethylene tubing. The valve is then opened, and the vapor
prevents accidental introduction of water into the detector and facilitates
3. The sample bag and its contents should be properly disposed of following
each analysis. Buna-N gaskets may be reused many times without cross-
contamination from one sample to another; however, the valve system should
is then checked with the field instrament to determine the effectiveness of the
purging. In the event of residual contamination, tubing attached to the valve
RESULTS AND CALIBRATION
1. This method provides relatively high sensitivity for detecting volatile
organic compounds (VOC) in the ppm range.
2. Field instruments are calibrated prior to taking sample measurements.
Single-constituent and multi-constituent standards may be used to develop
calibration curves depending on the preference of the investigator. Several
approaches are used for developing field calibration curves:
26
-------
A single component standard (e.g., xylene) is used to develop a
calibration curve. Results are reported for other petroleum
components as an equivalent of the standard.
A second approach involves the serial dilution of a water sample
that is spiked with a field standard. A relative concentration
calibration curve is developed by plotting the results of the serial
dilution analyses which can later be semi-quantified by a
laboratory analysis of the same samples.
A third alternative specifies that a multi-component standard with
the same constituents in proportions similar to those of the
contaminated water may be used to generate a calibration curve.
A final approach i
headspace readings
wells where the
generating a calibration curve based on
water samples obtained from several
of contaminants have been
sis.
Performance
ENVIRONMENTAL INFLUENCES
The salinity and dissolved organic content of water samples can affect field
standards, resulting in the development of misleading calibration curves. When
an unknown mixture of multiple constituents is analyzed, non-linear responses
result from concentration variations of different components in the mixture.
Variations in the organic content of the soil can also result in lower total
readings due to sorption and dissolution effects.
OPERATIONAL AND EQUIPMENT FACTORS
This procedure provides a well-controlled physical system, permits field
calibration and performance testing, and can produce results within a few
minutes. Studies of the differences in analytical results between samples
analyzed using the PBSS and those analyzed using other analytical procedures
have been initiated but the results are not yet available.
27
-------
of this procedure is usually within + 10 to
limit for this procedure is dependent on the an;
Table 3). For gasoline in soil and
used (see
in the
in
is greater than for gasoline by at least an order of magnitude.
Practitioners Contacted
The individuals listed below were contacted to obtain information on
procedure that they have used for analysis of soil and water samples. This
represents the principal practitioners involved in this type of work.
Gary Robbins
University of Connecticut
Peter Zack
Connecticut Department of
Robbins, G., R. Bristol, and M. Temple. "A Manual for Conducting Field
Screening for Subsurface Gasoline Contamination at Service Stations." U.S.
Environmental Protection Agency, Environmental Monitoring Systems
-------
The Draeger Liquid Extraction Kit (DLE Kit) uses colorimetric detector tubes
to quantitatively measure the amount of contaminant in water samples. The
basic principle of the procedure is the extraction of volatile contaminants by
drawing a stream of air through the sample.
measurement of water samples and requires only the equipment contained in
the kit and the specific detector tubes for the contaminants of concern. Figure
6 is a flowchart that shows the steps involved in performing this procedure.
7
This procedure can be used for a variety of applications. It can be used to
confirm the presence of contamination, determine the source of a release by
identifying areas with the highest levels of contamination, and help in the
placement of ground-water monitoring wells. Because the procedure provides
reliable quantifiable results, it is also a good procedure for measuring progress
of ground-water cleanup during corrective action.
Procedure Description
SAMPLE PREPARATION AND ANALYSIS
The principle components of the DLE Kit are:
1. Calibrated wash bottle - used to contain 200 ml of the sample for testing.
The bottle includes a fritted bubbler tube which enables the contaminant in the
water to enter into the gaseous phase for measurement with the detector tube.
2. Draeger gas detector pump - used to draw 100 ml of air per stroke through
the water sample and detector tube simultaneously.
-------
Pump
Sample bottle
Measuring cup
Calibrated wash bottle with fritted
bubbler tube
Sample size: 200 ml
- Slowly pour 20G-mi sample into calibrated wash
bottle to avoid volatile loss
- Insert thermometer into sample 2 inches below
blue line for 30 seconds and record temperature
- insert the fritted bubbler Into the wash bottle
- Open tube at each end and insert the appropriate
detector tube between the connecting hose of
calibrated'wash bottle and the Draeger Gas
Detector Purnp
- Firmly squeeze the hand bellows purnp the
required number of strokes for the detector tube
- Record concentration based on the length of
color stain in the detector tube
- Calculate concentration from test protocol sheet
- Concentration in ppm
30
-------
RUBBER HOSE
rnnn
DRAEGER DETECTOR TUBE
HEADSPACE
250 ml GAS WASHING BOTTLE
FRITTED BUBBLER
DRAEGER GAS DETECTOR PUMP
-------
of the concentration of contaminant in units of mg/1.
To perform the test, 200 ml of a water sample is placed in a calibrated wash
bottle. A hand bellows pump provided with the kit is used to pass a specified
volume of air through the sample and into the detector tube.
If the contaminant is present at concentrations within the sensitivity limits of
the system, a colored stain is created on the reagents contained in the detector
tube. The value on the tube that corresponds to the stain is recorded. A
calculation is performed to obtain the concentration of the contaminant in units
Performance
The selection of an appropriate detector tube depends on the contaminant to be
dependent upon the volume (number of strokes), the experimentally determined
system constants, and the sample temperature. The manufacturer has
determined calibration curves for a number of detector tubes including tubes
for benzene, total petroleum hydrocarbons (TPH), and toluene. The range of
concentrations that can be detected with these tabes is between 0.5 mg/1 (for
benzene) and 30 mg/1 (for TPH). The typical range of relative standard
deviations for measurements that are performed with the DLE method is +20
to 30 percent.
-------
ENVIRONMENTAL FACTORS
The temperature of the extraction
on the test results if it is within
temperature of the extraction
accounted for by using
water can affect test results; however, it is
calibration constants based on
Compounds that are chemically similar to the contaminant being tested will
often produce a color change of the detector tube. This is known as cross
sensitivity. The characteristic of cross-sensitivity is variable and has been
determined only for selected interferents by the manufacturer. This information
is on the instruction sheet provided for each type of detector tube.
EQUIPMENT FACTORS
When using the DLE Kit, care should be taken to keep the calibrated wash
bottle and fritted bubbler system as clean as possible to prevent cross-
contamination of samples and to ensure that an even flow of air is delivered
to the sample bottle. All points of connection within the DLE sampling system
should be tight so that the correct volume of air is delivered to the system.
At the time of this writing, the DLE Kit has not been placed on the market for
use by investigators. Information presented above was obtained from the
r, W,
Determine
Draeger Air
in Water."
33
-------
The Hanby Field Test Kit is a procedure for
hydrocarbons over a wide range of
is of petroleum
in water and
extraction
Figures 8
;asoline, diesel, etc.). The soil procedure requires two
§ the water procedure involves one extraction step.
the process of sample preparation and analysis for soil
This field procedure is being used by investigators to assess the presence of
determine the extent of contaminant plumes. As noted in Table 1, this
procedure can be used in other
installation of ground-water
, including selecting locations for
wells, determining limits of soil
SAMPLE COLLECTION - Soil and Water
1. Samples may be collected by a number of conventional methods. Soil
samples can be- obtained using a trowel, backhoe, auger, or split spoon sampler.
Water samples may be obtained using pumps, bailers, or sample bottles.
2. Minimize mixing, aerating, heating, or otherwise disturbing the sample to
prevent loss of any volatile organic compounds.
3. Decontaminate sampling and testing equipment between each sample
analysis to prevent cross-contamination. This can be accomplished using clean
water to thoroughly rinse all apparatus.
34
-------
- Split spoon sampler
Pour 100 g of soil into jar
Add 1 packet clarification reagent to jar
Add 500 ml of water to jar
to 30 minutes
Pour mixture into Imhoff cone
Let clarify for 15 to 20 minutes
Decant 250 ml of clear water (top) layer
into separately funnel
Add 5 ml of extraction reagent to
separatory funnei
Extract (swirl) separatory funnel for
minutes
Let liquids separate for 2 minutes
Drain extractant (lower) layer into
Shake tube for 30 seconds
Compare to color chart provided
Analysis time < 1 minute^ '
- Multiply test results by 20
(use provided worksheet)
- Concentration in pprn
Keep out of directsunlight: colorimetric reaction wili be degraded by
sunlight in as little as 2 minutes.
35
-------
Pour 500-m! sample into separatory funnel
Add 5 ml of extraction reagent to funnel
Agitate funne! for 2 minutes
Let liquids separate for 2 to 3 minutes
Drain extractant (lower) layer into test tube
Add contents of catalyst vial to test tube
Agitate test tube for 30 seconds
Compare to color chart provided with kit
Analysis time < 1 minute
- Concentration in ppm
Keep out of direct sunlight: colorimetric reaction will be degraded by
sunlight in as little as 2 minutes.
36
-------
SAMPLE PREPARATION AND ANALYSIS
The Hanby Field Test Kit provides the reagents and equipment necessary for
the extraction and colorimetric analysis of arornatics from contaminated soil
and water. This kit includes: a 500-ml separatory funnel, a tripod ring stand,
reagent vials, six 15-ml test tubes with rack, safety glasses, vinyl gloves, and
a color chart depicting test results at various concentrations of eleven aromatic
containing substances. A soil accessory kit contains an Imhoff cone and 30
packets of clarifying reagent. The following items are needed to perform soil
tests but are not provided in the Test Kit: quart jars with air-tight, screw-on lids
(e.g., glass canning jars) and a balance or scale accurate to 0.1 g.
Extraction of Soil
1. A soil sample of 100 grams and one packet of clarification rea,
placed into a 1-quart jar. Next, 500 ml of distilled water is added to
reagent mixture.
2. The jar is sealed with the lid;
intermittently for 20 to 30 minutes
3. The soil-water mixture is poured into an Imhoff cone and allowed to settle
for 15 to 20 minutes. Fine clays may take as long as 30 to 60 minutes to
settle.
4. After settling, 250 ml of the clear water layer is carefully decanted into the
separatory funnel. After the stopcock and glass stopper are closed, the
separatory funnel is gently swirled for 5 minutes while the glass stopper is held
in place. The runnel is periodically inverted and vented by opening the
Extraction of Water
[e of
.". M. A. «?
5-rnl ampule of extractant reagent is added to the separatory funnel, and the
water-reagent mixture is agitated for 2 minutes.
37
-------
Analysis of Soil and Water
1. The liquid in the separator^ funnel will form two layers. After the contents
of the separatory funnel are allowed to settle for 2 to 3 minutes, the lower
layer into the test tube (water consumes the catalyst making the colorimetric
visible moisture from the stem of the funnel. Empty the test tube into the 10-
ml graduated cylinder to measure the amount of extraction reagent recovered.
shaken for 30 seconds. Care should be taken to keep the test tube out of direct
sunlight once the catalyst has been added. Sunlight reverses the colorimetric
reaction in as little as 2 minutes.
3. The color of the test tube contents is compared to the color chart provided
with the test kit.
Note: To obtain aromatic concentration in ppm in soil, multiply test results
by 20. Use the worksheet provided by the manufacturer for soil samples to
arrive at the final concentration (mg/kg) in the sample. For heavily
contaminated soils (>400 ppm), water leaching (soil extraction steps 1-4) may
grams of soil and extracting for 2 minutes. After transferring 4.2 ml of clear
liquid to a test tube, follow step 2 (analysis of soil and water) above. Multiply
test results by 200 to obtain aromatic concentration in ppm.
METHOD RESULTS
The Hanby procedure is a colorimetric test that provides qualitative and
quantitative identification of the presence of petroleum compounds in soil or
water. Table 5 provides a summary of the optimum range of colors and
concentrations that can easily be determined for each compound, and a
reference for identifying the type of contaminant present.
-------
Toluene, Ethylbenzene, Orange-Yellow (1 ppm) to Burnt
Xylenes - - Oraiig<
Naphthalene Light Violet (0.1 ppm) to Blue
A mixture of different compounds will result in a color somewhere between the
colors shown on the chart. For example, gasoline, which yields a rust test color,
includes a mixture of benzene (yellow) and substituted benzenes (toluene,
ethylbenzene, xylenes) (orange).
This procedure provides a quantitative measurement from the shade or intensity
of the color, which corresponds to the concentration of the detected aromatic
compound. Generally, an optimum contaminant concentration range of 1 to 5
ppm is necessary to clearly distinguish the different colors on the Hanby color
chart. Distinctions can be made with increasing difficulty down to 0.05 ppm.
Although precise color identification is- not possible, discoloration of the test tube
contents with respect to a blank sample will be apparent to anyone with normal
vision. For instance, at 0.05 ppm it may not be possible to determine that the
light hue is benzene, TEX, or gasoline; however, it is clearly not naphthalene.
39
-------
Naphthalene or polynuclear aromatics produce a stronger color intensity at this
ration level,
of their large
ies and 15 minutes
together, the time
water samples. When several analyses are
to perform each analysis decreases.
compounds. It can permit quantitative assessment of the level of aromatic
contamination, and depending on concentration, can permit qualitative
identification of a particular compound or class of compounds. Practitioners
.g aromatic contamination.
ENVIRONMENTAL INFLUENCES
Top soil and humics containing natural aromatics can interfere with this
method when the heavily contaminated soil test method (>400 ppm) is used on
soils containing less than 400 ppm aromatics. Some practitioners have
indicated that soils containing fine clays and silts take an inordinate amount of
time to settle in step 3 of the soil extraction. The clarification reagent was
recently reformulated to address this problem.
REPRODUCIBILITY
The developer of this test kit, John Hanby, claims that the Hanby procedure is
comparable in reproducibility to purge-and-trap GC methods. This
approximately corresponds to a variation in accuracy of 10 percent, which
reportedly has been confirmed with split samples analyzed both by purge-and-
-------
One source of error In reproducibility of the procedure Is the draining of the
lower layer from the separatory funnel. The procedure specifies draining the
lower layer until it reaches the portion of the stem just above the stopcock,
leaving 0.8 ml in the separatory funnel (this specification Is to minimize the
likelihood that water will be drained as well.) Because the method is calibrated
to draining exactly 4.2 ml, the amount drained in the first analysis step must
be measured and corrected (if not 4,2 ml) by using the worksheet provided
with the kit. If this correction is not made, the contamination may be
overstated by as much as 16 percent.
The developer of the test kit
limits can be achieved when
that the following minimum detection
the least visible color changes to a
Although the compound or class of compounds may not be identified, the test
provides visible evidence of aromatic contamination as shown in Table 6
BTEX
0.05
0.5
-------
*HANBY METHOD*
The following individuals were contacted to obtain information on the Hanby
Billings & Associates, Inc.
Jeff Billings
John
Rick
Frank
Seneca Environmental Services
Hanby Analytical Labs
Vector Engineering
Environmental Conservation
-------
This procedure involves collecting a vapor sample from the subsurface and
transporting it to either an analytical instrument via a pump or to a container
for subsequent analysis by a portable analytical instrument. Figure 10 is a
process flow diagram showing the major steps in conducting soil vapor
sampling and analysis. The flow diagram is based 'on information received
Investigators contacted for information regarding this procedure reported that
they are conducting soil vapor sampling and analysis for a variety of reasons:
1) to confirm the presence of contamination; 2) to quantify the level of
contamination to provide an estimate of the degree and extent of a contaminant
plume; 3) to help -isolate the area(s) of highest contamina-tion and to identify
the source of a release; 4) to locate ground-water monitoring wells; and 5) to
assist in the selection of remedial technologies for site cleanup. The results
from soil vapor surveys are frequently used to develop contour maps of the
vapor plume. Contour maps of single or multiple constituents can be
generated, depending on the type of analytical results obtained.
Two basic procedures were identified for collection of soil vapor:
1) A borehole is made manually or mechanically in the subsurface, and
.the analytical field probe is inserted in the hole to directly withdraw and
analyze a vapor sample. This is graphically shown in Figure 11; and
2) A hollow steel probe is driven into undisturbed ground or inserted
into a borehole, and a vapor sample is withdrawn through the probe
(refer to Figure 12). Techniques used to collect and analyze soil vapor
are
-------
- Gas
- Interval can range from 10-100 ft.
- Based on site size, hydrogeology,
soil characteristics
- Can be accomplished using:
- manual or mechanically driven rod
0.5 - 4.0 inch diameter
- Probe Design:
- steel (galvanized, stainless, hardened)
Drive probe into smaller borehole or into
undisturbed ground (2 - 20 feet deep)
Probe Screen Design:
- perforated,
-open ended
44
-------
- Vacuum pump
Determine Soil Permeability
iTM.Ii
field instalment
, or
Manually recorded
Recorded on strip chart
(e.g., GC)
(continued)
45
-------
Ground Surface
Sampling Line
SOIL
STEP 1. INSTALL A BOREHOLE
STEP 2. INSERT INSTRUMENT PROBE
INTO BOREHOLE
-------
Tubing
Ground Surface
' B Borehole '
Perimeter
- SOIL
STEP 1. INSTALL A BOREHOLE
Vapor Probe
t Vapor Screen
SOIL
STEP 2. INSERT A VAPOR PROBE
IN THE BOREHOLE
Ambient Air
SOIL
STEPS. PURGE AMBIENT AIR
FROM VAPOR PROBE
-------
SOIL
Microliter Syringe
Perimeter
W VAPORS
Microliter Syringe
1. SAMPLE COLLECTION WITH A SYRINGE
2. SAMPLE ANAL YS1S BY GC
-------
SAMPLE ANALYSIS
SAMPLE COLLECTION
VAPORS *
COLLAPSIBLE BAG
VAPORS
P&iirmtef
VAPORS
SOIL
Collect Sample in a Collapsible
Microliter Syringe
SAMPLE BAG
0 0
Microliter Syringe
GAS
CHROMATOGRAPH
(PIO OR FID)
ALTERNATIVE I. Withdraw a Vapor Sample from Bag
Syringe and Analyze on the GC
PORTABLE FID OR PID
SAMPLE BAG
FID OR PID
SAMPLING LINE
ALTERNATIVE II. Analyze Soil Vapor Directly from Bag with a
Portable FID or PID
-------
VsporFlow
VAPOR
GAS
CHROMATOGRAPH
(PID OR FID)
SOIL
ALTERNATIVE I. SOIL VAPOR COLLECTION AND ANALYSIS USING A GC
Tutxi
FID OR PID
SAMPLING TUBE
Portafete
FID or PID
VAPORS
SOIL
ALTERNATIVE II. COLLECTION AND ANALYSIS USING A FID OR PID
-------
*SOIL VAPOR*
Procedure Description
LOCATE UTILITIES
All subsurface utilities are identified and marked prior to conducting soil vapor
sampling. Examples of underground utilities that may be present are electrical,
telephone, sewer, gas, and water lines. The location of underground storage
tanks and their associated piping should also be determined.
DETERMINE SAMPLE LOCATIONS
Sample locations can be determined by one of two general procedures: 1) lay
out a grid onsite, or 2) select locations based on site-specific conditions.
Grid Layout. Investigators reported using a grid spacing ranging from
10 to 100 feet. The length of the interval between sample points depends on
the size of the site and tank field; site hydrogeology; and the number of
samples to be collected. For example, at sites with relatively impermeable
soils, released product will probably not migrate far from the tank. Therefore,
it is preferable to sample locations placed close together (e.g., 10- to 20-foot
intervals).
Site Specific. When a grid is not used, sample points can be
located close to the known or suspected source of the release, or close to a
suspected receptor. To delineate the extent of a contaminant plume when the
source is known, vapor samples are taken in close proximity to the source. If
contamination is detected at the Initial sample points, another vapor sample is
collected farther away from the previous sample location. This procedure is
repeated until contamination is no longer observed at a sample point. •
BOREHOLE DESIGN AND INSTALLATION
s
A borehole is created in the subsurface to allow for sampling of soil vapors
either directly from the borehole (see Figure 11) or from a vapor probe inserted
into the borehole (see Figure 12).
51
-------
specific and depends on the soil type, depth to ground water, and size and
A borehole can be installed by a variety of methods including a steel hand
auger or corer, drill rig or rotary impact hammer, or b;
boreholes; a drill rig is needed for sampling at depths greater than 10 to 15
feet.
A vapor probe is inserted into the subsurface to provide access to a specific
sample interval. Probes are small-diameter, hollow cylinders with openings at
the sampling end to allow movement of vapor into the probe.
(hardened, stainless, or galvanized). PVC should be used only when inserting
a probe in a pre-made borehole. Most steel probes can be driven directly into
the subsurface; however, some materials are not as durable as others.
Diameter. A small-diameter probe (0.375 to 1.25
diameter) is preferable to minimize purge time and to
in
installation in
Length. Probes can be designed as a single unit (e.g., 4 to 7 feet
in length), which would limit the depth of
constructed in sections (e.g., 24 inches or 30
connected with threaded nipples.
They can
in length)
horizontal slots or small holes. The length of the screen depends on the sample
interval that is desired; most investigators reported using a screen length of 4
to 6 inches. A well point is attached (via a threaded nipple) to the end of the
probe screen to facilitate insertion of the probe into the ground and to prevent
the end of the probe from clogging. One investigator reported
52
-------
inserting an open-ended probe into a borehole; the end of the pipe serves as the
vapor screen.
Another investigator places a loose-fitting well point
After the probe has been driven down to
out approximately 6 inches. Whei
remains at the bottom of the hole and
to allow sampling of vapors.
is
end of
in the end of the probe.
depth, it is pulled back
back, the well point
sampling probe is open
Vapor Probe Installation. Vapor probes are installed in the
subsurface either by inserting them into predrilled boreholes (see Figure 12) or
by driving a probe directly into undisturbed ground (see Figure 11)0 Probes
can be directly driven into the ground manually using a slide hammer that
travels along a guide bar attached to the top of the probe, or mechanically
using a portable impact hammer or vehicle-mounted hydraulic hammer.
PROBE PURGING
After the probe, has been driven to the desired sampling depth, it is purged
(evacuated) to remove ambient air (see Figure 12). Purging can be
accomplished using either a hand pump, peristaltic pump, or vacuum pump
attached to the top of the probe via PVC or polyethylene tubing. Purge time
is based on the volume of the probe sampling system, and most investigators
reported purging long enough to remove 1 to 5 casing volumes of air from the
system. Purge times reported by the investigators ranged from 1 to 10 minutes.
G. Robbins purges at low gauge pressure (2 to 3 inches water), removing 2 to
5 probe volumes. Air flow gauges are attached to the probe and are followed
by a vacuum gauge to measure soil permeability. A valve follows the vacuum
gauge to regulate air flow and pressure, isolate the system for sampling (when
a syringe is used to collect a sample), and to isolate the system for tightness
testing. A paniculate filter is placed between the probe and flow gauge to
prevent damage to the gauges and pump.
EA Engineering and G. Robbins both
permeability of soils surrounding the probe
EA Engineering attaches a vacuum gauge
(see Figure 16). When a vacuum source is
that they 'evaluate the
to collecting a vapor sample.
valve to the sampling system
applied to purge the system (with
53
-------
Vacuum
Gauge
Septum Sampling Port
,or-
-Tight Valve
Ground Surface
Extender Tuba
Slotted Sampling Point
Soures: EA Engineering, Science, and Teehnslegy, inc.
54
-------
*SOIL VAPOR*
the valve shut off), the gauge is observed to determine if the system returns to
atmospheric pressure. If the vacuum gauge has not returned to atmospheric
permeability soils), and a sample is not collected at that location.
Described below are four procedures that investigators currently use to collect
and'analyze soil vapor. These procedures are illustrated in Figures 11 through
15.
1. After the vapor probe is purged, a vapor sample is obtained by inserting a
microliter syringe through a septum port or tubing attached to the probe, and
withdrawing vapor from the system. Sample volumes used by investigators
range from 100 to 1,000 ml. The sample is immediately injected into a mobile
GC for identification and quantification of the constituents (see Figure 13). [G.
Robbins inserts the syringe needle into a piece of silicon tubing or septa
immediately after sample collection to prevent any leakage prior to sample
analysis.]
2. A vapor sample is collected in a container (e.g., a Tedlar bag or a 40-ml
glass vial with a Teflon-lined screw cap) using a pump. The sample may be
analyzed directly from the container using a portable field instrument (i.e.,
withdrawn from the container with a glass microliter syringe and directly
injected into a mobile GC (see Figure 14). Sample containers to be reused
should be purged and tested for residual contamination between samples. (The
sample may need to be diluted to obtain accurate readings with PID and FID
instruments; see
3. The analytical instrument is directly connected to the vapor probe with
analysis (see Figure 15). Analysis with a mobile GC would require the use of
a pump (e.g., peristaltic pump) to transport the vapor sample through the
-------
Some investigators do not recommend in-line sampling and analysis of soil
vapor. This procedure may produce inaccurate results for the following
the flame In an FID, resulting in flame-outs (refer to Section IV); and 2) low
soil permeability conditions may restrict or prevent the rate of air flow to the
4. Some investigators do not use a vapor probe for sample collection. The
analytical field instrument or tubing attached to the instrument is inserted into
the borehole immediately after the borehole has been made. A vapor sample
instrument probe or tubing to minimize dilution of vapors with ambient air (see
Figure 11).
Sample Depth. The depth of sample collection can range from 2
to 20 feet below ground surface. Many investigators reported sampling at more
UUUJUJl WAJLV 'U-'H-'p'ftJLl &18- -a/~-
below the clay layer, but not in the layer.
cleaned between every sample. At a minimum, this should involve wiping or
washing the outside of the probe to remove any soil that is present. The (vapor
screen) slots or perforations should be cleared with a brash to ensure that the
openings are not clogged. Probes that are constructed in sections should be
through the slots/perforations.
Sampling Time. The time that it takes to collect a soil vapor
collection times ranging from 5 to 25 minutes. Sample analysis using a
portable PID or FID can be completed in under 5 minutes. GC sample analysis
usually takes less than 10 minutes depending on the compounds being
-------
GC analysis of soil vapor
typically at the ppm. level.
identification of specific compounds
most commonly analyzed for at
Results of soil vapor samples analyzed by a portable PID or FID are reported
as total organic volatiles (TOY), in "instrument units," or in ppm. The result
reported is either the highest concentration observed, or is the average
concentration based on readings taken over a specific time interval. Some
is
Several investigators stated that the results obtained from soil vapor
sampling/analysis should not be used to quantitatively assess levels of
contamination in the soil or ground water (regardless of the instrumentation
One investigator (M. Favero) reported observing a correlation between
constituent concentrations in soil vapor and concentrations of similar
constituents in ground water. The correlation was stronger the closer to the
ground-water table that the vapor sample was taken.
Performance
presence of impermeable materials, such as clays and fine silts, and by high
soil moisture. Both of these factors reduce vapor movement in the subsurface
and may prevent the collection of a representative sample. M. Favero stated
that soil being sampled for volatile organics should have a soil air-pore volume
of approximately 5 percent.
57
-------
REPRODUCIBILITY
compounds and for volatile halogenated compounds -such as TCE and
methylene chloride.
EA Engineering reported that it has compared the results obtained from a
mobile GC analysis to other laboratory analytical techniques; in general, similar
compounds were detected though the contaminant concentrations varied,
sometimes by several orders of magnitude. It reported that the mobile GC
provides good reproducibility of results. M. Favero of Tracer Research stated
that variation of results between split samples analyzed by independent labs is
generally within 25 percent. Because Tracer uses a standardized procedure to
collect soil vapor samples, it does not believe that reproducibility of the results
will be affected by the use of different technicians.
sample" and should be taken into consideration. Tracer has reproduced results
at specific sites using the same equipment under similar environmental
The individuals listed below were contacted to obtain information on the
procedure that they use to collect and analyze soil vapor samples. This list
represents only a small subset of the practitioners involved in this type of work.
Tracer Research Corporation
Storcfa Engineers
New Mexico Environmental
Division
Marcy Leavitt
-------
Mary McAuliffe Florida Department of Environmental Regulation
Gloria McCleary EA Engineering, Science, and Technology, Inc.
Frank Peduto New York Department of Environmental
-------
Analytical field instruments are an integral part of the field procedures 'described in this
document. The quality of the data obtained from a particular field procedure may be affected
by the analytical instrament used. Therefore, when selecting or applying a field procedure
at an UST site, an investigator must select a analytical field instrument that is appropriate.
The purpose of this section is to provide information on the operation, application and
performance considerations for each of the most commonly used types of analytical field
instruments. Investigators can use this information to select the instrament that is appropriate
to the type of investigation and field procedure being used to evaluate contamination.
Several types and specific models of analytical field instruments are available. The four most
common types of analytical instruments, which are described in this section, are:
• Flame lonization Detectors (FIDs);
Photoionization Detectors (PIDs);
Gas Chromatographs (GCs); and
Colorimetric Detector Tubes.
Table 7 presents performance information on each instrument type including the lowest
detection limit that has been reported for various procedures using different analytical field
instruments.
This section describes each type of analytical field instrament including a brief summary of
operation and performance considerations. In some cases, operations specifications are
summarized for different models of a particular type of field instrument, such as
photoionization detectors, to help the investigator choose an appropriate instrament. A list
of manufacturers' names and addresses is presented in Section V for reference and for
additional information on specific instruments.
-------
NJ
Portable
FID
Portable
PID
Medium
Medium
1-3 fr'mes
every day
1-3 times
every day
Easy
Very
Easy
8 Detects methane
® Low oxygen levels cause flame out
9 Recommended ambient air temperature is >40"F
(4-C)
9 Requires battery recharge every 8 hours
s Hydrogen gas is required
» Flow rate below 1.2 liter/min can yield inaccurate
results
8 Complete destruction of sample does not allow
further analysis
8 Detects the total concentration of many organic
vapors and gases (alkanes and aromatics)
® Photoionization lamp requires periodic
cleaning/changing
® Moist atmospheric conditions (e.g., rain) and high
relative humidity (>90%) in the sample can
"quench" the signal resulting in low readings
8 Dust particles may absorb ultraviolet energy and
cause erratic responses in PIDs that do not have
filters
8 Responses may be affected by power lines,
transformers, or radio wave transmitters
9 For concentrations > 150ppm TOV, the PID may
provide non-linear or erratic responses
8 Does not detect methane or other alkanes, thus
eliminating anomalous methane contributions
to total concentration readings
Qn-site routine maintenance by the operator
(continues on next page)
-------
to obtain accurate readings
Pump that draws a specific volume
the lube should be checked for
Ofj-s/fe routine maintenance by the operator
-------
A flame ionization detector (FID) is an instrument commonly used to detect and measure the
presence of many organic gases and vapors. The FID uses a hydrogen flame to ionize
molecules of volatile organic constituents present in the vapor sample. The ionized molecules
produce a current that is proportional to the total volatile organic vapor concentration in the
sample. The FID is useful for detecting most organic gases and vapors (e.g., alkanes and
aromatic hydrocarbons). The FID does not respond to ambient gas such as CO and CO2.
Table 7 lists the performance factors for FID instruments.
The Century Organic Vapor Analyzer (OVA), which is a commonly used portable FID, will
be used as an example for discussing the operation of FIDs. The OVA can be operated in
two modes: a survey mode, which detects total organic volatile compounds (TOVs); or a gas
chromatograph (GC) mode, which identifies and measures specific constituents (GCs are
described on page 72).
When the OVA is operated in the survey mode, the sample is delivered continuously to the
detection chamber by an internal diaphragm pumping system at a flow rate of 2 liters per
minute. The sample is ionized in the detection chamber, and the resulting signal is translated
as TOVs on the instrument meter. The instrument meter registers the concentration level of
the response. The OVA is internally calibrated for methane gas, and all survey responses are
expressed in methane equivalent (see Table 8).
The response time to obtain a reading in survey mode is 2 seconds or less. Many
investigators record the highest reading or take several readings over a specified period. The
operation time for the OVA is limited primarily by the charge on the battery, which usually
is 8 hours.
-------
*FLAME IONIZATION*
Compound -Response
Benzene 150%
Toluene 110%
Methane 100%
Ethane 90%
Propane • 64%
Ethanol 25%
Source: Product Literature, Century Organic Vapor Analyzer, Foxboro, 1985.
Performance Considerations
A number of environmental and equipment factors can influence FID performance. These
factors are briefly discussed below.
ENVIRONMENTAL FACTORS
FIDs detect methane and may yield high readings (false positives) when evaluating petroleum
releases in situations where methane is present (e.g., wetlands, sewers, septic fields, and
decaying organic matter). A colorimetric detector tube specific for methane can be used in
conjunction with an FID to evaluate methane concentrations (colorimetric tubes are discussed
on page 75).
In general, the FID exhibits no sensitivity changes due to slight variations in relative
humidity. FID instruments are less sensitive than PID instruments to environmental effects
such as temperature and high moisture. However, high winds may extinguish the flame in
an FID.
65
-------
*FLAME IONIZATION*
EQUIPMENT FACTORS
A portable FID is intended to provide relative concentrations of total organic volatiles
(TOVs); the values should not be considered absolute or representative of the actual
contaminant concentration level in a soil or water sample. The overall precision of an FID
when analyzing a known analyte is +10 percent. The range of detection for an OVA is from
0.2 to 10,000 ppm.
The FID requires a relatively high sample flow rate for reliable readings. Restricting the flow
rate may cause erratic responses and may extinguish the flame. Because of this limitation,
an FID will not provide reliable readings when it is used to draw soil vapor directly out of
a soil probe. The soil vapor must first be drawn into a Tedlar bag, and the FID can then
draw a fixed volume of vapor at a constant flow rate from the bag to determine the vapor
concentration.
The amount of oxygen in the sample can also influence the instrument response. If the
oxygen in the sample is below the level necessary to support the hydrogen flame in the
detection chamber, the flame will be extinguished and an audible or visual signal will indicate
the flame is out. Soil vapor often does not contain enough oxygen to support a flame. This
problem can be resolved by diluting the sample with a known quantity of air.
The FID should not be shipped when it is charged with hydrogen; many airlines do not allow
shipment of flammable gas. The hydrogen cartridge should be refilled after approximately
8 to 10 hours of operation. The battery usually needs to be recharged before the hydrogen
needs to be refilled. A source for hydrogen gas for refilling the gas cartridge may not always
be readily available in the field.
66
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Operating Principles and Specifications
A photoionizatlon detector (PID) is an instrument similar to the FID in that ionization is used
to detect and measure the presence of organic vapors. The PID uses a lamp that emits
ultraviolet light (UV) to ionize organic vapor molecules. During ionization of volatile organic
constituents, free electrons are generated that produce a current proportional to the number
of ions present, and the resulting signal is translated as total organic vapor concentration. The
instrument ionizes constituents with ionization potentials that are lower than the energy of the
lamp used. The PID does not ionize compounds found in ambient air (O2, N2, CO, CO2).
Interchangeable ultraviolet lamps that emit different energy levels of UV light can be used
to analyze constituents with different ionization potentials, thus allowing some degree of
selectivity. Table 7 lists the performance factors for PID instruments.
Operating specifications for PID instruments manufactured by HNU, Photovac, and Thermo
Environmental are given in Table 9. .The HNU line of field instruments consists of the base
model, which has recently been modified to be more moisture resistant, and an intrinsically
safe model that can be used in an explosive environment. One Photovac model (the
MicroTIP) has recently been upgraded and reduced in size. Thermo Environmental also
produces a PID model called an organic vapor monitor (OVM), which is moisture resistant.
The response time from these PID instruments ranges from <2 to 5 seconds (except for the
intrinsically safe HNU), which is comparable to the response time of an FID instrument. The
sample flow rate for a PID, however, is significantly less than that of an FID (0.3-0.5 liters
per minute for a PID versus 2 liters per minute for an FID), and may be useful in situations
where the flow rate is restricted. In general, PID instruments will operate in oxygen-deficient
atmospheres. The operation time for PID instruments on a single battery charge ranges from
3 to 10 hours and must be considered when evaluating the operational time required onsite.
Many of the portable PID instruments have been designed to minimize the effects of moisture
on instrument response (see Table 9).
Portable PID instruments can use different UV lamps to detect different volatile constituents.
The highest energy lamp (11.7 ev) detects-the widest range of volatile constituents, but
requires frequent replacement. The intermediate and lower energy lamps (10.2 ev and 9.5
ev) can detect many compounds without frequent lamp replacement. The lamp that is used
depends on the ionization potential of the analyte.
67
-------
a\
e©
Battery
Recharge/ Response
Operating Time Time
Instrument (hours) (seconds)
1.HNU P-101 14/10 <5
IS-101 14/10 <7
HW-101 14/10 <5
2. Photovac
TIP I 16/3 <3
MicroTIP 8/6 <3
Sample
Flow Rate
0/min)
<0.5
<0.5
<0.5
0.275
0.540
Filter
(microns)
none
none
0.5
15
2
Minimize;
Moisture
Effects
No
No
Yes
No
Yes ,
10
Yes
-------
*PHOTOIONIZATION DETECTORS*
Table 10 provides an example of PID lamp response to different hydrocarbons. PID
instruments are best suited for detecting aromatic nag compounds. This, is shown in Table
10 by the high response of the HNU to aromatic compounds. PIDs will detect the heavier
paraffins found in gasoline or other fuels, but do not detect light paraffins (alkanes) such as
methane. Thus, PIDs can be useful in detecting aromatic constituents released from USTs
in areas where "natural" methane may exist (e.g., septic fields, sewer lines, decomposing
Photoionization Response
Chemical Group
9.5-ev
.2-ev
11.7-ev
Aromatics
(e.g., benzene, toluene)
Paraffins (C5-C7)
(e.g., pentane, hexane, heptane)
Paraffins (CrC4)
(e.g., methane, ethane)
H
H: High response
L: Low response
NR: No response
The detection range for portable PID instruments is -0.2 to 2000 ppm. The accuracy varies
with the concentration level being measured. Table 11 provides an example of how
measurement accuracy decreases at concentration levels >100 ppm.
-------
PID Response at Different Concentration Ranges
1 to 10 ppm
10 to 100 ppm
±2 ppm or ±10%
whichever is greater
+15%
Portable PID instruments are being improved. The newer models, in particular, have software
features that store readings, time, and location of readings and can determine minimum,
maximum, and average concentrations.
Performance Considerations
A number of environmental and equipment factors affect the performance of PID instruments.
These factors have been experienced by several practitioners and are briefly discussed below.
ENVIRONMENTAL FACTORS
and high relative humidity (e.g., >90%) in the sample or ambient air. These moist conditions
essentially "quench" or decrease the signal and can cause erratic meter response, and thereby
decrease the accuracy level of the instrument readings. The PID is considered to be more
sensitive to humidity than the FID. Sensitivity to humidity is a very important consideration
-------
when testing soil vapor, which often has high humidity. In addition, if the ambient
temperature is less than the soil temperature, water vapor can condense in the PID ion
chamber. Ideal conditions for conducting PID analyses are dryweather and temperatures
>50°F
Dust will affect the response of the PID by "blocking" or "absorbing" the ultraviolet light,
which reduces the energy emitted. Constituents, if any, in the dust will ionize and cause
erratic responses. Instrument responses may also be altered by interference from nearby AC
or DC power lines, transformers, high-voltage equipment, or radio wave transmitters.
EQUIPMENT FACTORS
A portable PID provides relative concentrations of total organic volatiles (TOVs); the meter
values should not be considered to be representative of actual contaminant concentrations in
the sample. The readings obtained with the PID may not be considered entirely accurate for
mixtures of constituents and high concentration levels. Responses to gases or vapors may
change rapidly if mixtures are present. The PID has a highly variable response for each
compound. Some investigators report that for concentration levels >150-200 ppm, the
response of the PID is not as accurate as concentration levels <150 ppm. In addition,
sampling from a fixed- or limited-volume source will resMct the instrument air flow and
provide anomalously low instrument readings.
PIDs are relatively easy to transport and, unlike the FIDs, do not require flammable gases for
their operation. Caution should be exercised during transport and use to avoid breaking the
fragile and sensitive detector lamps.
71
-------
Operating Principles and Specifications
Portable gas chromatographs (GCs) utilize a separation column in conjunction with a
detection system (either a PID or FID) to isolate and analyze specific constituents in either
a liquid or vapor phase. GCs may be used for analyzing ambient air, soil vapor, and water.
Various models are made by a host of manufacturers, and to discuss all models would be
beyond the scope of this document. Thus, operational and performance information that is
GCs are used to determine the concentration of a wide range of individual hydrocarbon
constituents. Some investigators claim that the degree of contaminant weathering or loss of
volatiles can be determined by examining a chromatogram to identify the peaks present, and
evaluate the patterns of peaks, or the relative peak intensities or heights.
A portable GC consists of a sample injection system, a separation column, an output detector,
and a detection system. If the GC operates with an FID system, it will also contain a
combustible gas supply for the flame. A GC with a PID system contains an ultraviolet lamp.
Although the detection method may differ for these two types of GCs, the separation of
multiple constituents in chromatograph columns is similar.
The sample is injected using a syringe or is pumped into the GC and is carried through the
sample column by an inert carrier gas (if a liquid has been injected, it is vaporized by the
heat source). To analyze water samples using a portable GC, the contaminant must be
extracted before injection and analysis. As the sample constituents move through the
chromatograph column, they are separated based on their interaction with the column. Most
organic compounds elute from the column at different, though reproducible, rates. As the
individual compounds present in the sample are sequentially eluted from the column, they are
exposed to either a PID or FID. The ions produced are collected, forming a small electric
current which is amplified and measured using a potentiometric recorder/integrator. Principles
of the PID and FID systems are described previously in this section. Because the PID
process is nondestructive, the gas sample can be directed to an additional detection system
following PID analysis. The FID system, however, destroys the sample and does not allow
The combination of separation and ionization permits detection of the presence of numerous
organic constituents. The lighter contituents will elute first, followed by the heavier, less-
volatile constituents. As the constituents leave the column, they are carried to the detector
and registered on a linear meter and a chart recorder to produce a "chromatogram." The time
measured from the moment of sample injection until the compound of interest exits
72
-------
*GAS CHMOMATOGRAPHS*
the column is known as the retention time and serves to identify the constituent (field
calibration is discussed on page 78).
Constituents present in the sample can be identified by either comparing chromatograms to
reference standards or isolating individual constituent peaks. The concentration of a
constituent in the sample is proportional to the area under the peak in the chromatogram. The
area is determined by integration programs that are available from the manufacturer. The
chromatogram will consist of several dozen peaks, each representing a constituent present in
the sample.
Portable GCs have limited temperature and carrier gas controls as contrasted with laboratory
GCs, which can be programmed to vary the column temperature and carrier gas flow rate
throughout a sample analysis. Some portable field GCs offer options to maintain constant
temperatures in 10 or 20°C increments.
Performance Considerations
Performance of the portable GCs is greatly influenced by the operator's capabilities; these
instruments require a substantial level of skill to operate and interpret results. A number of
environmental and equipment factors can influence the results and can be interpreted
incorrectly by an inexperienced operator. These factors are briefly discussed below.
ENVIRONMENTAL FACTORS
Temperature fluctuations can cause erratic retention times and may lead to anomalous
readings for instruments without temperature control The ideal performance condition for
gas chromatograph operations is dry weather with small temperature changes. It is important
to calibrate the instrument under conditions that are similar to field conditions.
EQUIPMENT FACTORS
The response of the gas chromatograph varies with the type of detection method used (FID;
PID). The portable GC is not well suited for detection of high and low concentrations of two
constituents simultaneously, or for the separation of components with a wide range of
volatility. The portable GC cannot identify an "unknown" without some preliminary
identification of the sample, and detection of constituent concentration levels less than 10
73
-------
*GAS CHROMATOGRAPHS*
ppm can be difficult. For known analytes, the lower detection limit can be <5 ppb.
retention times and inadequate separation of constituents can occur in portable GCs because
they have limited column temperature controls, which can result In interferences that affect
the identification of peaks of individual constituents. Peaks may overlap and interfere with
each other and, thus, may not allow resolution and identification of a specific constituent.
74
-------
Coiorimetric detector tubes are used to measure a specific vapor or gas in air. These tubes
are often used for analysis of specific constituents or of a group of constituents (e.g.,
aromatics), or as a preliminary indicator of contamination prior to FID, PID5 or GC analysis.
Different types- of tubes are available for different volatile compounds (see Table 12).
Performance factors for coiorimetric detector tubes are presented in Table 7. In addition,
may interfere with other analytical field techniques. Coiorimetric detector tubes are relatively
inexpensive. The accuracy and detection ranges of a specific tube are stated in the
manufacturer's technical literature.
Coiorimetric detector tubes contain a chemical reagent impregnated on a porous carrier
material. A chemical reaction of the volatile compound inside the tube produces a color
change or stain, A known volume of the contaminated air sample is pulled through the tube
the tubes it reacts with the detector reagents to produce a stain. For most of the detector
tabes that are used for petroleum release site investigations (see Table 12 for an example),
the length of the stain in the tube is proportional to the concentration of the contaminant.
Usually the scale is graduated in parts per million (pprn) markings. The most commonly used
pump is a hand-operated bellows pump that delivers a volume of 100 cubic centimeters
through the tube with each stroke.
Performance Considerations
Minimal operator training is required for successful operation of coiorimetric detector tubes.
The accuracy and sensitivity of a particular tube is' determined and described for each tube
primarily by the manufacturer's specifications. However, several environmental and
equipment factors affect the performance of the detector tubes. These factors are briefly
discussed below.
ENVIRONMENTAL FACTORS
Coiorimetric detector tube results can be affected by high moisture content and humidity.
The manufacturer's instruction sheet provided for each tube should be consulted to determine
the amount of water vapor that will affect it. Tubes exposed to direct sunlight or
temperatures >86°F (SOT) for a period of time can give inaccurate readings.
-------
Selected Performance Characteristics of Colorimetric Detector Tubes (1)
Formula Dateeilon Hang®
Delation (2)
Gross
Benzene 0.5 a Comparison CgHe 0.5 to 10 ppm
Benzene 5 a Companson CgHg 5 to 40 ppm
Benzene 5 b Scale CgHg 5 to 50 ppm
Benzene 0.05 Comparison CgHg 15 to 420 ppm
Toluene 5/a Scale CgHgCHa 5 to 400 ppm
40 to 2
15 to 2
20
20 to 2
5
30 to 20%
30 to 20 %
15to 10%
30 to 20%
15 to 10%
Pale reddish
Other aromatic compounds are indicated
with approximately the same sensitivity as benzene
and can interfere or yield anomalously high results.
The predeanse layer absorbs interfering
components which give a reddish brown color.
With high concentrations of interfering substances,
the entire predeanse layer changes color and may
extend into the indicating layer. Determination of
Brownish
green
Brown
Brown
Other aromatic compounds and
petroleum hydrocarbons.
Same as "Benzene 5 a"
If mixtures of toluene and benzene are
present, more toluene is indicated than
is actually present. Xylene is indicated
with lower sensitivity than toluene Petroleum
hydrocarbons give a pale reddish brown
indication.
Toluene 25/a Scale
o-Xylene 10/a Scale
Petroleum Scale
Hydrocarbons
100/a
CgHgCHa 25 to 1 860 ppm 1 0
CsHgtCHala 10 to 400 ppm 5
100 to 2500 ppm 2
10 to 100 ppm 10
15 to 10% Brownish
violet
20 to 15% Reddish
brown
15 to 10% Brownish
green
Benzene gives a yellowish brown discoloration
which does not affect the detection of toluene
Xylene is indicated with the same sensitivity as
toluene. Other aromatic compounds can interfere
with detection of toluene.
Toluene, ethyl benzene can interfere (e g. 200 ppm
ethyl benzene can yield an indication of 350 ppm
with a brown indication).
Cg- Cg, benzene, toluene, jcylene
carbon monoxide, hydrogen sulfide.
Calibrated for n-octane.
(iy These specifications are from National Draeger, Inc..
Specifications from other manufacturers of detector tubes may vary from these.
(2) All left- and right-hand numerical values in the referenced columns are related.
(e.g. For benzene concentrations of 0.5 ppm, 40 strokes are required to attain that level of accuracy
with a standard deviation ef 30%).
-------
If more than one contaminant is present in a mixture of gases, those gases with similar
chemical structures may interfere with the contaminant of concern. This is referred to as
"cross-sensitivity." A preeleanse layer in the tube or a separate precleanse tube can serve as
a filter to selectively retain interfering compounds. The vapor sample to be measured flows
through the precleanse layer without restriction and then reacts, as intended, with the
indicating layer. It is, however, possible to exhaust the capacity of the precleanse layer when
high concentrations of interfering compounds are present.
Colorimetric detector tubes should not be used past their expiration dates or if the tubes have
been previously opened. One manufacturer date stamps the tubes for a 2-year shelf life and
stores the stamped tubes at 77°F (25°C) or below. Detector tubes should be handled gently
to prevent shattering glass. Tubes should not be exposed to heat sources or sunlight for
extended periods of time (i.e., do not store in vehicle). Check the manufacturer's instructions
to determine if the tube can be used again after obtaining a negative result. Manufacturer's
instructions should be consulted when using the Colorimetric detector tubes.
77
-------
Analytical field instruments should be calibrated at least once a day prior to beginning sample
analysis. Some investigators conduct instrument calibration at several intervals throughout
the day and also ran duplicate samples to evaluate the precision of the instrument
measurement. The FID, PID, and GC instruments are calibrated by a commercial gas
standard or using an appropriate field standard according to the manufacturers' recommended
procedures. These procedures, as well as field standard preparation, are discussed below.
Instrument Standards
FID INSTRUMENTS
The FID instrument that investigators reported using is the Century OVA. It is factory
calibrated to methane. Periodic calibration checks can be performed using commercially
available methane gas standards or standards that have been developed for volatile organic
compounds of concern. Manufacturer calibration procedures should be consulted for each
individual instrument used.
PID INSTRUMENTS
Most PID instruments are calibrated at the factory to either benzene or isobutylene. These
instruments may be calibrated by a background gas, a zero gas, or a field standard.
Calibrating a PID to a background gas is the least accurate. The presence of ionizable
constituents will give an inaccurate calibration. The PID can be calibrated to a field standard
by adjusting the digital readout or meter response to match the concentration of the
appropriate standard. Some PIDs display step-by-step calibration instruction to the user on
the digital readout. Manufacturer calibration procedures should be consulted for each type
of instrument used.
GAS CHROMATOGRAPH
The portable GC is typically calibrated at the beginning of the day and at intervals throughout
the day. A known amount of a compound or mixture of compounds is injected into the GC.
Known calibration samples should be injected under similar conditions as fieldsamples.
Ambient conditions can affect instrument performance if the GC is not calibrated under
similar conditions. Consult manufacturer calibration procedures.
-------
*F1ELD CALIBRATION*
COLORIMETRIC DETECTOR TUBES
A colorimetric detector tube is calibrated by the
concentration varies with different tube types. The
ranges from 10 to 30 percent.
; however, the measured
deviation for a detector tube
Field Standards
After the field instrument is calibrated, field standards can be prepared for developing single
or multiple constituent calibration curves. Calibration curves can be used to indicate the
"actual" concentration in the sample based on equivalent instrument readings.
There are several approaches for preparation of water and soil field standards. These include
the following:
8 Standards can be prepared using different concentrations of a single constituent
(e.g., benzene) or of a multi-constituent (e.g., gasoline or diesel);
e Serial dilution of water or vapor samples may be used to develop a relative
concentration calibration curve;
8 A multi-constituent standard that has the same constituents in a similar
• proportion as that of the sample may be used;
« Calibration curves can be generated based on headspace readings from water
or soil samples.
A minimum of three standard concentration should be used to generate a calibration curve
(e.g., background soil samples spiked at concentrations between 10 and 500 ppm of gasoline).
-------
Combustible Gas Indicators (Explosimeters)
ERDCO Engineering Corp.
Evanston, IL 60204
312/328-0550
600 Perm Center Blvd.
Pittsburgh, PA 15235
412/273-5000
Industrial Scientific Devices
355 Steubenville Pike
1792 Highland Ave.s NE
Hickory, NC 28603
800/338-9869
Coiorimetric Detection Tubes
Mine Safety Appliance
Pittsburgh, PA 15235
412/273-5000.
-------
* ANALYTICAL HELB INSTRUMENTS*
30 Seaview Drive
Box 1587
Secaucus,NJ 07094
National Draeger, Inc.
Pittsburgh, PA 15230
12345 Starkey Rd.
Largo, FL 33543
813/530-3602
- Suite 3
2175 W. Park Ct.
P.O. Box 1959
Stone Mountain, GA 30086
404/469-2720
2021 GW Commonwealth
Fullerton, CA 92633
714/992-2780
Flame lonization Detectors
Foxboro Analytical
330 Naponset Ave.
Foxboro, MA 02035
82
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Photoionization Detectors And Portable Gas Chromatographs
Analytical Instruments Development, Inc.
Route 41 and Newark Road.
215/268-3181
Newton, MA 02161
Photovac, Inc.
134 Doncastor Ave.
Canada L3T1L3
416/881-8225
6862 Huyvanhurst Ave.
Van Nuys, CA 91406
League City, TX 77573
713/332-2484
Sentex Sensing Technology Inc.
553 Broad Street
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Environmental Instrumentation
2170 Commerce Ave., Units
Concord, CA 94520
4565 Highway 93 North
Golden, CO 80403-8097
Westinghouse Groundwater Recovery
Atlanta, GA 30360
404/449-9411 800/922-9497
P.O. Box 489
Roanoke, IN 46783
Enviroscan Inc.
303 W. Military Road
Rothschild, WI 34474
800/338-7226
Geoprobe Systems
607 Barney
Salina, KS 67401
913/825-1842
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"ANALYTICAL FIELD INSTRUMENTS*
KVA Analytical Systems
281 Main Street
Falmouth, MA 02541-9981
508/540-0561
Soilmoisture Equipment Corp.
P.O. Box 30025
Santa Barbara, CA 93105
805/964-3525
Miscellaneous - Hydrocarbon Detector
Adsistor Technology Inc.
P.O. Box 51160
Seattle, WA 98115
206/368-9110
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Accuracy - The extent to which the results of a calculation or the readings of an instrament
approach the true values of the calculated or measured quantities, and are free from error.
Air Rotary Getting - Soil samples collected from a borehole when using an air rotary
drilling rig.
Alkanes (Paraffins) - A compound consisting of hydrogen and carbon with straight or
branched single carbon-carbon bonds having the empirical formula CnH2n+2 (e.g., ethane,
propane). Most alkanes have high vapor pressures and are therefore easily volatilized. Vapor
pressure of alkanes decreases as the size of the molecule increases. Aikanes as a category
are generally flammable or combustible. They have low solubility in water.
Aromatic Hydrocarbons - A compound whose molecule contains one or more benzene
rings; many of these compounds have a recognizable odor (e.g., xylenes, naphthalene). The
light aromatics (benzene, toluene, xylenes, ethylbenzene) have the highest solubilities of the
hydrocarbon constituents of gasoline. They are relatively volatile.
Bailer - A long, cylindrical sampling device lowered into a well on a rope or cable and filled
with a ground-water sample.
BTEX - Benzene, toluene, ethylbenzene, and xylenes.
BTX - Benzene, toluene, and xylenes.
Catalyst - Substance that affects the rate of a reaction without being used up itself.
Chromatogrami = A plot displaying peaks for the constituents detected by a gas
chromatograph. The concentration of a constituent is determined from the relative peak
heights compared to a standard' of known concentration.
Colorimetric - Describes any technique by which an unknown color is visually evaluated in
terms of standard colors. The concentration of a compound can be measured quantitatively
from the shade or intensity of, the test color or the length of the test color stain in a scaled
vessel.
Dissolution - The process where a material passes into solution with a liquid.
87
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•"GLOSSARY*
Distilled Water - Water purified by distillation; specifically by the process of first heating
a mixture to separate the pure water vapor from impurities, and then cooling and condensing
the resulting vapor to produce more nearly pure water.
Draeger Tube - A particular brand of colorimetric detector tubes used to analyze volatile
constituents.
EStition - The removal or separation of adsorbed species from a chromatographic column by
means of a stream of liquid or gas.
Extraction - Process where materials are separated using physical or chemical means.
FID - Flame ionization detector; an instrument used to measure the presence of organic-
volatile compounds by ionization using a hydrogen flame. A current is produced in
proportion to the number of ions present.
Field Standards - Samples of known concentrations that are used in the field for calibration
and comparison with unknown samples.
Flux - Rate of flow.
GC - Gas chromatograph; an instrument where samples are separated based on the weight
and polarity of the molecules into specific constituents and are detected using PID, FID, or
ECD. A chart recorder plots results as a "chromatogram" displaying peaks for constituents
GC-PID - Gas chromatographic instrument utilizing a photoionization detector.
GC/MS - A laboratory instrument that performs both gas chromatographic and mass
spectrometric analyses.
Graduated Cylinder - A cylindrical vessel that is calibrated in fluid ounces or milliliters or -
both; used to measure the-volume of liquids.
HNU - Trade name for a portable photoionization detection instrument.
Imhoff Cone - A cone shaped graduated vessel used to measure the volume of solids that
will settle out of a liquid.
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Immiscible - Incapable of mixing or blending; not soluble.
Impermeable. - Media through which substances cannot be diffused at any measurable rate.
In Situ - Within place; commonly used to refer to the location of activities (e.g., in situ soil
vapor measurements).
Inert - Exhibits no chemical reactivity.
lonizatiois - A process by which a neutral molecule loses or gains electrons, thereby
acquiring a net charge and becoming an ion. It occurs as a result of the dissociation of a
molecule in solution or of a gas in an electrical field.
IS - Intrinsically safe; designation that a company, HNU, has assigned for a portable
photoionization instrument used in explosive environments.
Isomap - A contour map delineating points having the same value (e.g., contaminant
concentration, ion flux concentration).
Leaching - Action whereby soluble constituents migrate through permeable media due to the
vertical percolation/infiltration of a liquid.
Microliter Syringe - A device consisting of a narrow tube fitted at one end with a rubber
bulb or piston by means of which a liquid can be drawn into the tube and then ejected from
the tube; calibrated to deliver one-millionth of a liter (i.e., 1 microliter).
Monitoring Well - A hollow, perforated cylinder inserted into a boring in the ground for the
purpose of obtaining ground-water samples.
Naphthalene - A compound with the molecular formula C10H8, It is a polynuclear aromatic
hydrocarbon (PNA), structurally represented as two benzene rings fused together.
Naphthalene is an organic compound with a relatively high molecular weight and low vapor
pressure.
Operation Time - The period during which the instrument is in use, beginning with the time
it is turned on and continuing until it is turned off.
OVA - Organic Vapor Analyzer, trade name of a portable flame ionization detector (FID)
produced by Century, Inc.
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OVM - Organic Vapor Meter, trade name of a portable photoionization detector (PID)
constituents and the properties of the substances with
Compounds having high vapor pressures are easily volatilized
more soluble a compound is in water, the less volatile it is.
come in contact.
ition off as vapor. The
PBSS - Polyethylene bag sampling system.
contact with pump parts.
PID - Photoionization detector; an instrument used
by ionization using UV radiation. A current is
present.
measure organic volatile compounds
in proportion to the number of ions
PPM - Part per million.
Precision - The extent to which the result of a set of calculations or the readings of an
Qualitative - Analytical results presented on a relative or comparative basis.
Quantitative - Analytical results presented on a measured scale.
Reagent - A substance used in a chemical analysis because of the
environmental media contaminated by underground storage tank products.
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Remediation - The process of implementing available cleanup technologies appropriate for
mitigating contamination at a site.
Reproducibility - The precision and/or accuracy with which a method can duplicate its
results.
Retention Time - The period of time during which a sample resides in an instrument before
identification of the constituent.
Salinity - A measure of the concentration of dissolved salts in a liquid.
Septum Port - A membrane opening in some instruments through which a substance can be
injected with a syringe.
Septum Vial - Small containers having a membrane in the cap through which a substance
can be injected or withdrawn with a syringe.
Serial Dilution - Performing a series of dilutions on a substance to generate a calibration
curve or to reduce the concentration of a substance to the measurable level of the instrument
ring used.
Sorption - The process of substances (e.g., benzene, toluene) being taken up and held by
another substance (e.g., soil) by either adsorption or absorption.
Split Spoon Sampler - Soil sampling device used during drilling of boreholes for obtaining
soil samples at specific depths.
TCE - Trichloroethylene.
Tedlar Bag - Brand name for a collapsible container equipped with a resealable valve and
used to store gas samples.
Teflon - Brand name for a manufactured material that is resistant to many hydrocarbon
cc
TEX - Toluene, ethylbenzene, and xylenes.
Thermal Desorption - Use of heat to remove volatile organic compounds from a solid
sorbent matrix.
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*GLOSSARY*
TIP - The trade name for a portable photoionization analyzer that provides a measurement
of volatile organic constituents.
TOV - Total organic volatiles.
TPH - Total petroleum hydrocarbons.
Tygon - Brand name of a manufactured, inert plastic material frequently used for tubing.
UST - Underground storage tank.
Vapor Headspace - The gas that collects above a solid or liquid sample and below the
container lid.
Vapor Probe - That portion of an analytical instrument that is used to collect a gas; often
inserted into contaminated soil.
VOC - Volatile organic compounds; compounds that readily vaporize at normal temperatures
and pressures.
Volatilization - The conversion of a chemical substance from a liquid or solid state to a
gaseous or vapor state by raising the vapor pressure of the substance. The vapor pressure of
a substance is strongly influenced by increasing temperatures. Also known as vaporization.
Ziploc Bag - Brand name of a reclosable freezer bag generally used in polyethylene bag
sampling systems.
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