Comparison of VOA Compositing Procedures
September 1995
U.S. Environmental Protection Agency
Office of Water
Office of Science and Technology
Engineering and Analysis Division (4303)
401 M Street SW
Washington, DC 20460
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Comparison of VOA Compositing Procedures
Acknowledgments
This study described in this report was performed under the direction of William A. Telliard of
the Engineering and Analysis Division (EAD) within the U.S. Environmental Protection
Agency's (EPA's) Office of Water. This report was prepared under EPA Contract 68-C3-0337 by
DynCorp Environmental, with the assistance of Interface, Inc.
The authors wish to thank Pacific Analytical, Inc. for the isotope dilution GC/MS analyses and
Isco, Inc. and Associated Design and Manufacturing Co. for training and assistance in the use
of their automated samplers.
Disclaimer
This report has been reviewed and approved for publication by the Engineering and Analysis
Division of the U.S. Environmental Protection Agency. Mention of company names, trade
names, or commercial products does not constitute endorsement or recommendation for use.
Further Information
For further information, contact:
William A. Telliard
USEPA Office of Water
Engineering and Analysis Division (4303)
401 M Street SW
Washington, DC 20460
Phone: 202-260-7120
Fax: 202-260-7185
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Comparison of VOA Compositing Procedures
SUMMARY
This report provides results produced by VOA grab and composite sampling procedures in
studies conducted by the U.S. Environmental Protection Agency (EPA) in early 1994. In these
studies, four individual grab samples of real-world effluents were collected over the course of
a day. These samples were analyzed spiked or unspiked, composited and individually, by
isotope dilution GC/MS, using Revision C of EPA Method 1624. Both manual and automated
grab sampling procedures were employed. Compositing procedures employed included flask,
purge device, and continuous. Analytes spiked were the volatile organic GC/MS fraction of the
priority pollutants plus additional compounds routinely tested for in EPA's industrial surveys.
The objective of these studies was to compare the analytical results for manually collected
individual grab samples to the analytical results for composited samples and automatically
collected grab samples, to determine if bias occurred in the automated grab and compositing
processes. Several compositing methods were investigated including: flask compositing and
purge device compositing of automated and manual grab samples, and continuous compositing.
These tests showed that, for the samples tested, the mathematical average of the analytical
results for hand collected grab samples were higher than results for composited samples.
Conversely, mathematical averages of the analytical results for hand collected grab samples
were marginally lower than results of automated grab samples. The cause of these slight
differences is not known. However, the differences are not significant when compared to the
variability in the analytical technique. It is not likely that these differences would have been
found using a less sensitive analytical technique than isotope dilution GC/MS.
September 1995
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Comparison of VOA Compositing Procedures
Background
Volatile Organic Compounds (VOCs)
The Federal Water Pollution Control Act of 1972 (PL 92-500) required EPA to control the
discharge of toxic pollutants to the nation's waters. The act listed 65 compounds and compound
classes for regulation as toxic pollutants. This list was later refined into an initial list of 129
"priority pollutants" and then a final priority pollutant list containing 126 individual compounds
(Reference 1).
' For determination of the priority pollutants, EPA separated the list of 126 compounds into
groups based on the analytical technology that could be used to measure the pollutants. Those
organic pollutants that could be determined by gas chromatography combined with mass
spectrometry (GC/MS) were further categorized into volatile and acid/base/neutral extractable
fractions.
The volatile fraction, also called the "purgeable" fraction, contains those compounds that boil
below approximately 130 °C and that are capable of being purged from water using a flowing gas
stream (Reference 2). Analysis of this fraction is termed a "volatile organic analysis" (VOA) and
the compounds in this fraction are termed "volatile organic compounds" (VOCs). Determination
of VOCs in the VOA fraction of the list of priority pollutants is the subject of this study.
Pollutant Lists
A list of VOCs analyzed in this study is provided in Table 1. This table also provides a list
of the stable isotopically-labeled analogs that were used for isotope dilution quantitation, and
information concerning whether a given analyte is a priority pollutant or other pollutant
associated with the 1976 Consent Decree (Reference 1). Chemical Abstracts Service Registry
Numbers for the pollutants and their labeled analogs are given, where available.
The VOCs listed in Table 1 are separated into two groups. The first group contains VOCs
that are determined by GC/MS using authentic standards; the second group contains VOCs
determined by "reverse search." These latter compounds are considered identified when the
chromatographic retention time and mass spectrum agree with those specified in the method.
When a match is found, the compound is quantitated based on a response factor also given in
the method. Although results produced by the reverse search technique are not as precise or
accurate as results produced using authentic standards, the technique is useful for screening
and provides approximate concentrations for VOCs in the reverse-search group. Furthermore,
reverse search is more accurate in identifying compounds than a forward library search in which
only the mass spectrum is tested against a large mass spectral file.
September 1995
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Comparison of VOA Compositing Procedures
Table 1
Volatile Organic Compounds Analyzed
Compounds Determined by Isotope Dilution or Internal Standard
Compound
Acetone
Acrolein
Acrylonitrile
Benzene
Bromodichloromethane
Bromoform
Bromomethane
Carbon tetrachloride
Chlorobenzene
Chloroethane
2-Chloroethylvinyl ether
Chloroform
Chloromethane
Dibromochloromethane
1,1-Dichloroethane
1,2-Dichloroethane
1,1-Dichloroethene
trans-1 ,2-Dichloroethene
1 ,2-Dichloropropane
trans-1 ,3-Dichloropropene
Diethyl ether
p-Dioxane
Ethylbenzene
Methylene chloride
Methyl ethyl ketone (MEK)
1 ,1 ,2,2-Tetrachloroethane
Tetrachloroethene
Toluene
1,1,1-Trichloroethane
1 ,1 ,2-Trichloroethane
Trichloroethene
Vinyl chloride
CAS Registry
67-64-1
107-02-8
107-13-1
71-43-2
75-27-4
75-25-2
74-83-9
56-23-5
108-90-7
75-00-3
110-75-8
67-66-3
74-87-3
124-48-1
75-34-3
1 07-06-2
75-35-4
1 56-60-5
78-87-5
10061-02-6
60-29-7
123-91-1
100-41-4
75-09-2
78-93-3
79-34-5
127-18-4
109-88-3
71-55-6
79-00-5
79-01-6
75-01-4
Labeled Compound
Analog
d6
d4
d3
d6
13C
13/^
\j
d3
,3C
d5
d5
13C
d3
13C
d3
d4
d2
d3
d6
d4
dio
d8
dio
d2
d3
d2
i3r>
02
d8
d3
13c2
13/^
O2
d3
CAS Registry
666-52-4
33984-05-3
53807-26-4
1076-43-3
93952-10-4
72802-81-4
1111-88-2
32488-50-9
3114-55-4
19199-91-8
31717-44-9
1111-89-3
93951-99-6
56912-77-7
17070-07-0
22280-73-5
42366-47-2
93952-08-0
93951-86-1
2679-89-2
17647-74-4
25837-05-2
1665-00-5
53389-26-7
33685-54-0
32488-49-6
2037-26-5
2747-58-2
93952-09-1
93952-00-2
6745-35-3
.Priority^
Pollutant
N
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
N
N
Y
Y
N
Y
Y
Y
Y
Y
Y
Y
September 1995
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Comparison of VOA Compositing Procedi
Compounds Determined by Reverse Search
Compound
Carbon disulfide
cis-1 ,3-Dichloropropene
2-Hexanone
4-Methyl-2-pentanone
Trichlorofluoromethane
Vinyl acetate
/n-Xylene
o- and p-Xylene
CAS Registry
75-15-0
10061-01-5
591-78-6
108-10-1
75-69-4
108-05-4
108-38-3
*
Priority Pollutant
N
Y
N
N
N
N
N
N
* O-xylene CAS Registry = 95-47-6
P-xylene CAS Registry = 106-42-3
In addition to the priority pollutant VOCs, EPA has regulated other VOCs under the Safe
Drinking Water Act (SDWA) and amendments, the Resource Conservation and Recovery Act
(RCRA) and amendments, the Clean Air Act (CAA) and amendments, and the Comprehensive
Environmental Response, Compensation, and Liability Act (CERCLA or Superfund) and
amendments. Although the VOCs listed in these lists are not identical to the list in Table 1,
many of the compounds found on these other lists are included in Table 1, and, therefore, the
results of this study are considered to be applicable to the VOCs found on these other list's.
"Gases" and "Water-Soluble" Compounds
Two groups of compounds present unique analytical problems in the determination of VOCs.
These groups are the "gases" and "water-soluble compounds." The priority pollutant gases are
chloromethane, bromometharie, chloroethane, and vinyl chloride. These gases boil below
approximately 15c C and are readily lost from aqueous solutions. These losses make the
analysis more variable than for compounds that are not lost as readily. Conversely, the water-
soluble compounds present a separate set of analytical problems because they are not readily
purged from water. In this study, the water-soluble priority pollutants tested are acrolein,
acrylonitrile, and 2-chloroethylvinyl ether. Non-priority pollutant water-soluble compounds
tested were acetone, 2-butanone (MEK), p-dioxane, and diethyl ether.
Control of Discharges
The Engineering and Analysis Division (EAD), within the Office of Science and Technology
in EPA's Office of Water, is responsible for promulgating regulations controlling the discharge
of pollutants to U.S. surface waters. EAD conducts surveys of the regulated industry to
establish the best pollutant control strategies within various categories and subcategories
September 1995
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Comparison of VOA Compositing Procedures
(Reference 3). In these surveys, EAD frequently samples and analyzes wastewaters to
determine the presence and concentration of pollutants. Although these studies primarily focus
on the 126 priority pollutants (40 CFR 423, Appendix A) and the five conventional pollutants
(40 CFR 401.16), other "non-conventional" pollutants may also be determined and subsequently
proposed for regulation.
In conducting these surveys, EPA collects aqueous samples in and around wastewater
treatment plants and other locations. Unless treatment system characteristics dictate
otherwise, VOA samples are composited to effect a cost savings over the analysis of individual
grab samples. Normally, four individual grab samples are collected at approximately equal time
intervals over the course of a 24-hour day. These samples are stored at 4 C, shipped under wet
ice to the testing laboratory and composited in the laboratory. Results of these analyses are
then used, in part, to develop, propose, and promulgate effluent guidelines and standards for
the appropriate industrial category at 40 CFR Parts 403 - 499.
September 1995
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Comparison of VOA Cc
Theoretical Considerations and Prior Work
VOA compositing is used extensively by EPA for data gathering in regulatory development
programs, and is used for compliance monitoring under EPA rules. The technical literature is
replete with theoretical discussions of the effects that compositing may have on data integrity
Book chapters on the subject by Gilbert (Reference 4) and by Garner et al. (Reference 5) provide
comprehensive evaluations of the concepts behind composite sampling and provide extensive
bibliographies referencing the technical literature on sample compositing and statistical
treatments of the compositing process.
Although the technical literature contains many theoretical discussions of VOA compositing
it is remarkably silent concerning data gathering designed to verify the theoretical work A
search of online databases revealed only one technical paper that presents actual results of a
VOA compositing study (Reference 6).
Variability of Individual and Composite Measurements
Any empirical measurement process has inherent variability, and the measurement of each
analyte in each analysis is accompanied by an analytical error. This error is normally
characterized by replicate measurements and is expressed as the standard deviation of the
concentration or is normalized to the concentration as the "relative standard deviation" or
"coefficient of variation." For example, the concentration of chloroform may be determined by
purge-and-trap GC/MS with a relative standard deviation of 10 percent.
The effect of measurement error on the result for a composite sample and on the average of
individual grab samples can be understood most easily if it is assumed that the concentration
of a pollutant is identical in all of the individual grab samples. Averaging the results for
analysis of four individual samples requires determination of the concentration four separate
tunes. Because measurement error is inversely proportional to the square root of the number
of measurements, the measurement error associated with the four individual grab samples will
be one-half of the error associated with any individual measurement. Because the
determination of concentration in a composite sample is an individual measurement the error
associated with the average of four individual grab samples will be one-half of'the error
associated with the measurement of a composite sample.
Therefore, the most precise and accurate results will be produced if the individual grab
samples are analyzed and the results averaged. The cost of analysis, however, will be four times
as great as the cost for analysis of a single composite sample. Similar accuracy and precision
could be achieved if the compositing process were replicated four times and the four composites
analyzed separately, assuming that no error occurred in the compositing procedure Pragmatic
•September 1995
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Comparison of VOA Compositing Procedures
considerations (e.g., cost and time) frequently outweigh the benefits acquired by measurement
of grab samples individually; so discussions of error become moot, and the error associated with
measuring concentration in a single composite sample becomes the only measurement error that
must be considered.
September 1995
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Comparison of VOA Compositing Procedures
Types Of Compositing
Time Compositing
Time compositing is the most common type of sample compositing. Samples are collected
from a fixed sampling point over some fixed period of time, usually a 24-hour period beginning
at midnight. Samples can be collected as discrete grab samples at intervals throughout the
fixed time period, or continuously over the period.
Transients
The objective of sampling over time, whether the sampling is grab or continuous, is to
attempt to capture the transient nature of compounds in the waste stream. Capture of
transients requires a knowledge of the flow characteristics of each individual stream: system
volumes, flow rates, and the nature of the transient wave. If the objective is to capture the
concentration maximum, the ideal scheme is to collect a grab sample at the apex of the wave.
Unfortunately, this scheme is frequently impractical. The next best scheme is to collect samples
at frequent enough intervals to assure that some fraction of the transient will be captured.
Although use of a continuous compositor will assure capture of the transient, the transient may
be diluted by the stream before and after the passage of the wave. Therefore, if monitoring of
transients in a waste stream is necessary to characterize treatment system operation, samples
should be collected over the wave to model the wave. After the wave characteristics are known,
the intervals for subsequent sampling can be determined.
Treatment System Detention Times
For treated effluents, a common mistake made by personnel unfamiliar with treatment
system operation is to require grab samples at intervals more frequent than the detention time
of the treatment system. For example, if the treatment system has a detention time of 6 hours,
sampling the effluent from the system more frequently than every few hours is unnecessary,
particularly if the samples are analyzed individually.
Spatial Compositing
Samples from different sampling points can be composited in an effort to save analysis costs.
If an analyte is present in a composited sample, each sampling point can then be sampled
individually to determine the point or points contributing to the level of the analyte in the
sample. Spatial compositing of up to five streams is allowed, at the discretion of the States,
under EPA drinking water regulations to reduce the total number of samples that small
drinking water treatment system operators must analyze [40 CFR 141.24(f)(14)]. However, the
analytical system must be capable of detecting one-fifth of the maximum contaminant level
(MCL) required for an individual sample. This requirement can usually be met by compositing
five 5-mL samples and purging a 25-mL composite, as suggested in the CFR.
September 1995
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Comparison of VOA Compositing Procedures
Flow or Volume Compositing
As the name implies, flow or volume compositing involves proportioning the sample
according to the flow rate or volume of the stream being sampled. The most common use of flow
compositing is in stormwater sampling pursuant to EPA's stormwater rules [40 CFR
122.21(g)(7); Reference 7]. These rules require that the composited sample proportionately
represent the runoff that occurs in a stormwater event. Because it is impossible to know
beforehand the total discharge volume during the event, individual grab samples must be
collected at time intervals throughout the event, and varying volumes from these individual
grab samples must be composited to reflect the flow during the entire stormwater event. The
details of stormwater sampling and analysis, along with an example of the compositing
associated with a stormwater discharge event, have been described by Stanko (Reference 8).
Problems Unique to VOA Compositing
The high vapor pressure of VOAs, and particularly of the volatile gases, makes these
analytes particularly susceptible to loss through evaporation during any manipulation, including
collection and compositing.
Headspace During Sampling
Analyte loss to the headspace of a container has been documented by Cline and Severin
(Reference 6). Therefore, it is imperative that headspace be eliminated during sampling and
sample shipment. In this study, the loss of volatiles was not critical because the objective was
to compare the results from analyses of individual grab samples with the results from analysis
of a composited sample. If the loss of VOCs from the individual grab samples and from the
samples that feed the composite are the same, there is no consequence to this loss.
Losses During Compositing
None of the existing compositing procedures requires that compositing be performed with
zero headspace, and such a system in a laboratory is difficult to envision. Because such a
system does not exist, exposure of the sample to the atmosphere can result in analyte losses
through evaporation. Loss can be minimized by cooling the sample and minimizing the exposure
time. In this study, all compositing (except continuous compositing) was performed rapidly with
the VOA vials chilled to 0 - 4 C.
Compositing Procedures
Definitions
Sample: The water collected in a sample jug from a specific location at a specific time.
Individual grab sample: An aliquot poured from the sample jug.
Duplicate grab sample: A second aliquot poured from the same sample jug.
10 September 1995
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Comparison of VOA Compositing Procedure
Replicate grab sample: Any aliquot poured from the sample jug.
Composite sample: The physical combination of four grab samples collected at different times
on the same day.
Mathematical composite: The mathematical average of the analytical results of four individual
grab samples.
Manual Compositing
Two types of manual compositing procedures were tested in this study: flask compositing
and purge device compositing. Each of these procedures is described below. A third procedure,
syringe compositing, is also described below but was not tested because of resource limitations!
Flask Compositing (44 FR 69555^
In the flask compositing procedure, a 300- to 500-mL round-bottom flask is immersed in an
ice bath. The individual VOA grab samples, maintained at 0 - 4°C, are slowly poured into the
round-bottom flask. The flask is swirled slowly to mix the individual grab samples. After
mixing, multiple aliquots of the composited sample are poured into VOA vials and sealed for
subsequent analysis. An aliquot can also be poured into a syringe for immediate analysis.
Purge Device Compositing [40 CFR 141.24(f)(1)(v)]
Equal volumes of individual grab samples are added to a purge device to a total volume of
5 or 25 mL. The sample is then analyzed.
Syringe Compositing [40 CFR 141.24(f)(14)(iv)]
In the syringe compositing procedure, equal volumes of individual grab samples at a
temperature of 0 - 4° C are aspirated into a 25-mL syringe while maintaining zero headspace
in the syringe. Either the total volume in the syringe or an aliquot is subsequently analyzed.
The disadvantage of this technique is that the individual samples must be poured carefully in
an attempt to achieve equal volumes of each. An alternate procedure uses multiple 5-mL
syringes that are filled with the individual grab samples and then injected sequentially into the
25-mL syringe.
Automated Collection and Compositing
Two types of automated equipment are available for sample collection and/or compositing.
These are: (1) automated grab collection; and (2) automated continuous collection/compositing.
These devices are described below.
September 1995 ,,
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Comparison of VOA Compositing Procedures
Automated Grab Collection
Automated grab collection can be accomplished using devices such as the Isco, Inc. Model
6000 automatic VOC sampler. With this system, a small bladder pump forces sample into a 40-
mL VOA vial after rinsing the vial with three vial volumes as required by the method. In
addition, the system overfills the vial to eliminate headspace. Up to 25 samples can be collected
at a minimum of 5-minute and a maximum of 10-hour intervals. Samples are maintained at 0 -
4 C during collection.
Automated Continuous Collection/compositing
An automated system such as the Associated Design and Manufacturing Co. (ADM)
automated continuous compositing system can be used to collect samples over a given sampling
period. Sample is pushed into a bubble trap in the sampler via a peristaltic pump. The sample
is then drawn into an air-tight glass syringe, the volume of which is controlled by a piston
connected to a timer. The timer, and therefore the sampling frequency, is set by the user, or can
be connected to a flow meter so that sampling frequency is dependent upon the flow rate. Upon
completion of the sampling event, the syringe is capped with a Luer-Lok™ closure, and the
entire syringe is delivered to the laboratory for sample analysis, thereby maintaining zero-
headspace conditions.
12 September 1995
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Comparison of VOA Compositing Procedures
Study Phases
The objective of these studies was to compare the analytical results for manually collected
individual grab samples to the analytical results for composited samples and automatically
collected grab samples, to determine if bias occurred in the automated grab or compositing
processes. Several compositing methods were investigated including: flask compositing and
purge device compositing of automated and manual grab samples, and continuous compositing.
The study reported here was divided into three phases: Phase I, a pilot phase with spiked
reagent water and an unspiked field sample; Phase II, which used spiked field samples to
compare flask or purge device compositing with mathematical compositing; and Phase III, which
used spiked field samples to compare purge device compositing, automated compositing,
automated grab collection, and mathematical compositing.
Sample Collection, Shipment, and Storage
All samples collected at industrial or municipal sites were preserved to pH < 2, refrigerated,
and shipped to the laboratory under wet ice via overnight courier. If free chlorine was present
in the sample, the sample was additionally preserved with sodium thiosulfate. Samples were
stored in the laboratory at 0 - 4° C from the time of collection until analysis. All analyses were
performed within the method-specified 14-day holding time.
Phase I and Phase II samples were collected by passage of a portion of the flowing sample
stream through a coil of pre-cleaned polytetrafluoroethylene (PTFE) tubing that was immersed
in a commercial picnic cooler filled with ice. This practice reduced the temperature of the
sample to 0-4° C, thus reducing the volatility of the VOCs. The stream from the PTFE tubing
was collected in a cooled one-liter glass jug. Samples were preserved to pH < 2 in this jug and
free chlorine was removed, as required, using sodium thiosulfate.
After preservation, samples were allocated from the one-liter jug into 40-mL VOA vials.
Vials were filled from the common jug, thus assuring that each replicate VOA vial in the set
contained identical samples. The vials were filled to overflowing, then capped with a PTFE-
faced silicone rubber septum. After capping, each VOA vial was inverted and inspected for an
air bubble. If a bubble was present, the vial was uncapped and refilled to overflowing and re-
capped until completely filled without an air bubble. Each vial was assigned a unique sample
number. Sampling times were at approximately 9 a.m., noon, 3 p.m., and 6 p.m. Collection
procedures for Phase III sampling are outlined in the Phase III study design section.
Analyses
All laboratory analyses were performed by Pacific Analytical, Inc., in Carlsbad, California.
A single laboratory was chosen to perform this work because EPA desired to minimize analytical
variability in order to increase the probability that differences between grab sampling and
compositing procedures would be detected.
September 1995 10
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Comparison ofVOA Compositing Procedures
Calibration
All analyses were performed by isotope dilution GC/MS using Revision C of EPA Method
1624. Revision C is an updated version of the method promulgated for use in water programs
(40 CFR 136, Appendix A). Revision C includes a "reverse-search" technique for identification
and quantitation of pollutants other than the priority pollutants. In the promulgated version
and in Revision C of Method 1624, the priority pollutants and certain additional compounds are
determined using a 5-point calibration for quantitation. Nominal calibration points are 10, 20,
50, 100, and 200 ug/L. In addition, the list of "reverse search" compounds is determined from
relative retention time data and response factors given in the method.
In this study, the method of quantitation was examined in relation to recovery of the VOCs
for which the instrument was calibrated. The calibration procedures in Method 1624 require
use of an average relative response or a calibration curve for isotope dilution calibration based
on the five calibration points. However, because the analytes were spiked at known
concentrations, it is possible to use the calibration point closest to each known concentration for
calibration. This technique was used for calculation of all concentrations in Phases II and III
of this study and reduced the analytical error to less than that obtained using the average of the
five calibration points or a calibration curve. This practice of using the closest calibration point
should only be employed when the concentration of a pollutant in a sample is known to be close
to the calibration point. For samples containing unknown concentrations, such as the unspiked
field samples in Phase I, the most accurate analyte concentrations will be found using the entire
5-point calibration curve.
Data Processing and Reporting
Data were received by the EPA Sample Control Center in the form of quantitation reports
on diskette. These data included quality control (QC) data for each analysis. The QC data
included recoveries for each labeled compound spiked. The QC data were tested against the QC
acceptance criteria in the method using a modified version of QA Formaster™ supplied by
Thermo-Finnigan Corp. Non-compliant data were resolved with the laboratory.
14 September 1995
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Comparison of VOA Compositing Procedures
Phase I
Study Design
Two types of samples were analyzed in Phase I: an unspiked field sample set, and two
spiked reagent water sample sets. Each set consisted of four aliquots representing a single
sampling point and time. Reagent water was used to test compositing effects in the absence of
matrix effects, and to eliminate any possible interference from native pollutants. Two
concentrations were used to test whether compositing effects were concentration dependent.
In order to ensure complete solubility, each of the four aliquots per set was spiked with one-
fourth of the total analyte list at either 100 ug/L or 600 ug/L , resulting in composite samples
with nominal concentrations of 25 ug/L and 150 ug/L , respectively. However, the 600 ug/L
individual aliquots exceeded the calibration range of the instrument, and so these aliquots were
diluted 1:3 (sample:reagent water) prior to analysis. The low concentration spiking scheme for
each aliquot is shown in Table 2. The analyte list was separated into the four groups on the
basis of solubility in water. After spiking, each aliquot was then split: one split to be physically
composited with splits from each of the other three aliquots, and one split to be analyzed
separately. Each analyte was present at full concentration in one of the four aliqouts, and not
present in the other three. This results in the analyte being present at the nominal
concentration in the composite. The results of the four individually analyzed splits were than
averaged to derive the mathematical composite value. If there were 100% recovery of the spike
in the individually analyzed splits, the average concentration of each analyte would be
iOQug/L+OMg/L + Oug/L
for the low concentration samples.
Table 2
Phase I VOC Spiking Groups*
Analyte
Carbon tetrachloride
Chlorobenzene
trans-1 ,3-Dichloropropene
1 ,2-Dichloroethane
Ethylbenzene
Tetrachloroethene
Cone. In
Aliquot 1
100pg/L
100 ug/L
100 ug/l_
100 ug/l_
loOpg/L
lOOpg/L
Cone. In
Aliquot 2
0
0
0
0
0
0
Cone. In
Aliquot 3
0
0
0
0
0
0
Cone. In
Aliquot 4
0
0 -
0
0
0
0
Cone. In
Composite
25 ug/L
25 ug/L
25 ug/L
25 ug/L
25 ug/L
25 ug/L
September 1995
15
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Comparison of VOA Compositing Procedures
Analyte
1 ,1 ,2-Trichloroethane
1,1-Dichloroethene
trans-1 ,2-Dichloroethene
1 ,2-Dichloropropane
Benzene
Bromodichloromethane
Bromoform
Dibromochloromethane
1 ,1 ,2,2-Tetrachloroethane
Toluene
1,1,1 -Trichloroethane
Trichloroethene
1,1-Dichloroethane
Methylene Chloride
Bromomethane
Chloroethane
Chloromethane
Vinyl chloride
Diethyl ether
Chloroform
Acetone
Acrolein
Acrylonitrile
2-Butanone
p-Dioxane
Cone. In
Aliquot 1
100 Mg/L
100 Mg/L
100|jg/L
100 Mg/L
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Cone. In
Aliquot 2
0
0
0
0
100 Mg/L
100 Mg/L
100 Mg/L
100 Mg/L
100 Mg/L
100 Mg/L
100 Mg/L
100 Mg/L
100 Mg/L
100 Mg/L
0
0
0
0
0
0
0
0
0
I
0
0
Cone. In
Aliquot 3
0
0
0
0
0
0
0
0
0
0
0
0
0
0
100 Mg/L
100 Mg/L
100 Mg/L
100 Mg/L
100 Mg/L
100 Mg/L
0
0
0
0
0
Cone. In
Aliquot 4
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
100 }ig/L
100 Mg/L
100 Mg/L
100 Mg/L
100 Mg/L
Cone. In
Composite
25 Mg/L
25 Mg/L
25 ug/l_
25 ug/l_
25 ug/l_
25 pg/L
25 ug/L
25 Mg/L
25 pg/L
25 Mg/L
25 Mg/L
25 Mg/L
25 Mg/L
25 Mg/L
25 Mg/L
25 Mg/L
25 Mg/L
25 Mg/L
25 Mg/L
25 Mg/L
25 Mg/L
25 Mg/L
25 Mg/L
25 Mg/L
25 Mg/L
*For the high concentration group, each compound was spiked at 600 Mg/L in the same pattern.
Composite concentrations were 150 Mg/L in each analyte.
16
September 1995
-------
Comparison of VOA Compositing Procedu
Statistical Analyses and Results
Spiked Reagent Water Samples
When averaged across all compounds, the physical composite of the low concentration splits
had 8% higher recoveries1 than the mathematical composite of the low concentration splits. The
physical composite of the high concentration splits had 17% higher recoveries than the
mathematical composite of the high concentration splits. Because there was only one sample
at each concentration, statistical analyses could not be performed. As both concentrations
behaved similarly, their results were combined to allow statistical analysis, and paired t tests
were performed for each analyte. Of the 29 analytes for which reliable data was received, a
significant difference between the mathematical composite and the physical composite was seen
for only one analyte. This result would be expected on the basis of chance alone, and therefore,
the results of the physical and mathematical composites are not statistically different.
Unspiked Field Samples
The physically composited sample had analyte concentrations that were 13% lower than
those for the mathematically composited sample. This result is the opposite of that seen in the
reagent water sample. However, due to the fact that there was only one unspiked field sample,
no statistical analyses could be performed, and therefore, the results cannot be considered
statistically significant. Despite the attempt to find an industrial source with high levels of
volatiles, only 10 analytes were present in measurable quantities. This lead to the decision to
spike field samples in future studies.
throughout this document, the term "recovery" refers to the percent of spike value
following correction for labelled compound recovery.
September 1995 , ~
-------
Comparison of VOA Compositing Procedures
Phase II
Study Design
Four samples were collected at different times over the course of a day from seven "real-
world" sites. These sites are described in Table 3. Information about each site was recorded
in an on-site log and included the EPA sample number, collection date and time, descriptions
of sample and sampling location, sample pH and temperature, and preservatives used, if any.
Table 3
Description of Sites and Samples
Episode
4559
4561
4563
4573
4575
4593
4595
Industrial Category
Organic Chemicals
Organic Chemicals
Drum Reconditioning
Shore Reception
Transportation
Transportation
MSW Landfill
Sampling Point
Primary Effluent
Primary Effluent
Scrubber Water
Oily Wastewater
Separator Effluent
Separator Effluent
Leachate
PH
8.8
7.3
8.6
5.6
6.0
6.8
6.8
Sample sites were selected based on the expectation that the effluents would contain volatile
organics. However, volatile organics were seldom found and, therefore, samples were spiked
with VOAs. All spiking solutions were prepared in the laboratory and all spiking was performed
in the laboratory. Samples from three episodes were flask composited and samples from four
episodes were purge device composited. Schematic diagrams of the flask and purge device
compositing procedures are shown in Figures 1 and 2, respectively. For the episodes that were
flask composited, the grab sample from the first sample time was analyzed unspiked to
determine the background concentrations of VOCs present. For the episodes that were purge
device composited, the grab samples from all four time points were analyzed unspiked to
determine the background concentrations present. This testing was done to determine the
constancy of the background throughout the sampling period, and to remove the influence of
background levels from statistical analyses.
Individual grab sample VOA vials from each of the four time points were spiked at
concentrations of 20, 40, 80, and 40 ug/L, respectively, to produce an average concentration of
45 ug/L. An aliquot from these spiked VOA vials was analyzed and two other aliquots were used
to make duplicate composites, thus assuring that the spike levels were identical for analyses
of the individual and composited samples.
18
September 1995
-------
Comparison ofVOA Compositing Procedure
T2 T3 T4
Key
a Unspiked
S 20 pg/L Spike
m 40 Mg/L Spike
• 80 MQ/L Spike
Figure 1. Flask Compositing Scheme
T1
T2
T3
T4
D
D
D
D
Key
D Unspiked
Q 20 M9/L Spike
0 40 |jg/L Spike
• 80 pg/L Spike
Figure 2. Purge Device Compositing Scheme
September 1995
19
-------
Comparison of VOA Compositing Procedures
Statistical Analyses And Results
Analytes Tested
Data were evaluated with respect to QC requirements and three analytes were dropped from
further analysis due to poor quantitation: 1,1,1-trichloroethane, 2-chloroethylvinyl ether, and
trans-l-2-dichloroethene. All other analytes met QC requirements and were included in all
statistical analyses.
Background Subtraction
The background level determined from the single, unspiked sample in each of the flask-
composited episodes was subtracted from the result of all grab and composite samples for that
episode. For each grab sample in the purge device-composited episode, the background level
from the sample collected at the same point and time was subtracted from the analytical result.
For each composite sample, the results of the four individual backgrounds were averaged, and
the resulting value was subtracted from the composite results.
Statistical Analyses
For each analyte in each episode, the percent recoveries in the four grab samples were
averaged, as were those of the two physical composites. The median recovery across all analytes
and episodes was calculated. In addition, the ratio of mathematical composite recovery to
physical composite recovery was calculated for each analyte in each episode, according to the
formula
^ t. Mean mathematical composite recovery
Ratio = ;—•
Mean physical composite recovery
A two-tailed Student's t test was performed to determine if this ratio was significantly
different from 1.0, at the 5% level. In addition, a two-tailed Student's t-test was performed to
determine if there were any differences between recoveries in samples composited in a flask and
recoveries in samples composited in the purge device. When the number of samples in the two
groups being compared are unequal, the Student's t test results are affected more severely by
unequal variances for the two groups (Reference 10, p. 230). Since the variance for flask-
composited samples was unequal to that for purge device-composited samples, and the sample
sizes differed between the two groups, Satterthwaite's correction for unequal variances was
applied to the t test calculations.
Results
The pollutants detected in the real-world samples were mainly the water-soluble compounds,
resulting in high analytical variability. Statistically significant differences between the
mathematically averaged results from analysis of the individual grab samples and the result
from analysis of the physically composited sample were identified for a number of analytes.
However, the size of the difference is small and may not be meaningful when compared to the
2Q September 1995
-------
Comparison of VOA Compositing Procedures
analytical variability. The two compositing methods, flask and purge device, provide analytical
results for all analytes that are not statistically different.
Comparison of Grab and Composite Results
Table 4 compares composite recovery with grab recovery. These tests show that, for the
analytes for which background subtraction was not required and from which the gases and
water-soluble compounds were excluded, the median result for grab samples was 12.2 percent
higher than the median result for the flask composites, and 7.3 percent higher than the median
result for the purge device composites.
Depending on the analyte and analytical conditions, between 16% and 62% of the analytes
show significantly lower concentrations in the composite samples than in the individual grab
samples. The number of analytes showing these effects is much greater than would be expected
by chance alone. In addition, the two compositing procedures show results in the same
direction. The size of the effect, as a percent of the grab concentration, ranges up to 21, with
the median across analytes showing the effect in the range of 6-13 percent. However, for
routine VOA analyses this effect may not be significant compared to other sources of analytical
variability.
Flask and Purge Device Compositing
Two-tailed Student's t-tests were used to determine the significance of differences between
the two techniques for each analyte. Only 1 out of 20 analytes showed a significant effect on a
two-tailed test at p=0.05; this could easily be due to chance variation. The two compositing
procedures, therefore, give consistent results. Analytes tested were those with data for at least
3 samples by each method.
September 1995 21
-------
Comparison ofVOA Compositing Procedures
Table 4
Comparison of Composite Recovery with Grab Recovery
Composite
Location
Flask
Purge
Device
Background
Excluded
Subtracted
Excluded
Subtracted
Gas/HoO
Solubfe
No
Yes
No
Yes
No
Yes
No
Yes
Analytes
Tested
26
11
23
9
25
11
25
11
Number
Signif.
16
5
12
4
9
5
4
5
Median
Effect*
12.2%
13.0%
12.3%
13.1%
7.3%
9.0%
6.2%
9.3%
Max.
Effect*
21.0%
16.1%
21.0%
16.1%
12.5%
15.3%
11.1%
15.3%
* Effect = 100 x (grab concentration - composite concentration)/grab concentration.
"Background" indicates whether analytes present prior to spiking were background-subtracted or
excluded from the analysis. Analytes tested were those with data for at least 3 samples;
significance was tested at the p=0.05 level, two-tailed. As stated above, all significant differences
were in the direction of lower composite concentration.
22
September 1995
-------
Comparison ofVOA Compositing Procedures
Phase
Study Design
The purpose of this study phase was to compare manual grab, automated grab,
mathematical compositing and automated compositing techniques. Two sites, with markedly
different effluent matrices, were chosen for sampling: a POTW and a bus maintenance facility.
Effluent from each site was collected, well mixed, and divided among four collapsible bags.
Collapsible bags were used to minimize the amount of head space created as samples were
withdrawn from the bags. Each bag was spiked with a different level of VOCs to simulate
collection at different times. The spiking levels used were the same as those used in Phase II.
Samples collected by all techniques at a single time were drawn from the same bag. The
automated composite was drawn for the same length of time from each of the four bags.
The sampling scheme for Phase III is shown in Table 5 and Figure 3. From each bag, two
grab samples were drawn manually and one drawn with an automated sampler. In addition,
one sample from each site was drawn by an automated compositor. The automated compositor
was set to draw a 0.3 mL sample every 40 seconds, until a total of approximately 10 mL was
drawn (34 samples over a 23 minute period). This procedure was repeated in each of the four
bags. One sample from each manually-drawn pair was assigned to the group to be analyzed
directly and mathematically composited. The second manual grab sample was assigned to the
group to be physically composited. Another single sample from each of the four bags was
manually drawn prior to spiking, and was analyzed individually to assess the background levels
of analytes present in the samples.
Phase
Table 5
Sampling Scheme
Bag
(Time)
1
2
3
4
Per Site
Samples
Manual
Grab
Manual
Grab
Manual
Grab
Manual
Grab
Mathematically
Composited
Automated
Grab
Automated
Grab
Automated
Grab
Automated
Grab
Mathematically
Composited
Manual
Grab
Manual
Grab
Manual
Grab
Manual
Grab
Physically
Composited
Back-
ground
Back-
ground
Back-
ground
Back-
ground
Automated
Composite
September 1995
23
-------
Comparison ofVOA Compositing Procedures
E33Manual Grab
HI Automated Grab
iBManual Composite
HH Automated Composite
O Unspiked
© 20 ug/L Spike
40 ug/L Spike
80 ug/L Spike
Figure 3. Phase III Compositing Scheme
Description of Sampling Equipment
Automated Grab Sampler
Automated grab samples were collected using an automated VGA sampler (Model 6000, Isco
Environmental Division, Lincoln, NE). Sample is collected via a bladder pump that pushes the
sample into the vial and does not expose the sample to a vacuum or partial vacuum. Prior to
collection, the Model 6000 rinses the sample line and overfills the VGA vial three times, as
required by the method and to eliminate headspace. The vials are filled via a syringe needle in
a 360 stream designed to remove any air bubbles that may cling to the vials. The vials are
covered with caps containing an air-tight valve that is opened for filling. When a vial is filled,
the valve is closed.
Automated composite samples were collected using an automated VGA compositing sampler
(AVOCS®-500, Associated Design and Manufacturing Co., Alexandria, VA). Sample is pushed
into a bubble trap in the sampler via a peristaltic pump. The sample is then drawn into an air-
24
September 1995
-------
Comparison ofVOA Compositing Procedures
tight glass syringe, the volume of which is controlled by a piston connected to a timer. The
timer, and therefore the sampling frequency, is set by the user, or can be connected to a flow
meter so that sampling frequency can be coupled to the flow rate. Upon completion of the
sampling event, the syringe is capped with a Luer-Lok™ closure, and the entire syringe is
delivered to the laboratory for sample analysis, thereby maintaining zero-headspace conditions.
Statistical Analyses and Results
Statistical Analyses
Analyte concentrations detected at each sampling time (bag) were background-corrected
using the concentrations found in the background sample for that time. For the automated
composite, the background value used for correction was the average of the background values
for each bag. For each analyte in each episode, the percent of spike recoveries in the manual
grab samples were averaged, as were those of the automated grab samples. A Dunnett's test
was performed using the mathematical composite of the manual grab as the control group. This
test allows comparison of multiple techniques to a single control group. In addition, for each
sampling technique, median and maximum effects were calculated. As in Phase II, effects are
in terms of the difference between grab recovery and recovery by a particular technique, as a
percentage of the grab recovery.
Results
The results are summarized in Table 6. For 11 of 30 analytes (37%), the physically
composited samples had significantly lower recoveries than the mathematical composite of the
manual grab samples. This percentage is far more than one would expect based on chance
alone. Neither the automated compositor nor the automated sampler produced results which
were statistically different from the mathematical composite of the manual grab sample for any
analyte.
Table 6
Comparison of Alternative Sampling Techniques
Sampling Technique
Automated Grab
Automated Composite
Physical Composite
Number of
Analytes
30
30
30
Number
Significantly
Different
0
0
11
Median
Effect*
/o/ \
(/o)
-4.6
8.1
15.0
Maximum
Effect*
(%)
-29.8
43.8
-42.0
* Effect = 100 x (Manual grab - technique) / Manual grab; a negative effect indicates that the
technique resulted in higher recoveries than the manual grab.
September 1995
25
-------
-------
Comparison of VOA Compositing Procedures
Conclusions and Discussion
Mathematical averages of the results from analyses of grab samples were found to be larger
than the result from the analysis of either flask- or purge device-composited samples, although
these differences are on the order of a few percent and would not be discernable except by
isotope dilution quantitation procedures. In addition, the number of samples tested in this
study (from 1 to 7, depending on the phase) was relatively small, even though the number of
analytes per sample (29-40) was large. Because the behavior of one analyte can be expected to
be correlated with that of other analytes in the sample, it is possible that the small number of
samples results in differences that would be negated or lost in a larger study. For example, it
is possible that the matrix for a particular sample contributed to the loss of analytes during
compositing. If the behavior of analytes is correlated, then similar losses would be expected for
many analytes in that sample. Because the primary metric in this study was the number of
analytes that showed significant loss, a large difference in one sample out of the small number
of samples could have a large impact on the study results. However, it is not know whether
matrices have a differential effect on analyte loss.
The recoveries for the composited samples using reagent water in Phase I were greater than
the average of the non-composited samples; in Phases II and III, the composited samples
produced recoveries lower than the average of the non-composited samples. The reasons for
these differences among the study phases are not known, but there are several possibilities.
First, the results of the Phase I reagent water were not statistically significant, in part due to
the small number of samples. Second, the individual reagent water aliquots were diluted 1:3
(sample:reagent water) while the composited reagent water aliquots were not. It is possible that
some loss of analytes occurred during the dilution procedure. Third, it is possible that field
samples have a greater loss of analyte during compositing due to the effects of the matrix or to
interference by native analytes. Last, it is possible that the differences are due to measuring
or compositing errors, even though calibrated syringes and volumetric glassware were used.
Compositing can be useful in some situations and will result in a cost savings over the
analysis of individual grab samples. However, compositing may introduce some small
systematic error in the analytical results. EPA plans to continue the use of VOA compositing
in its effluent guidelines program and, after further studies, may promulgate compositing
procedures for wastewaters.
September 1995 07
-------
-------
Comparison of VOA Compositing Procedures
References
1. Keith, L.H. and Telliard, W.A. Env. Sci. & Tech.. 1979, 13(4) 416 - 423.
2. Bellar, T.A., Lichtenberg, J.J., and Kroner,R.C. J. Am. Water Works Assoc.. 1974, 66,
703 - 706.
3. Telliard, W.A., Rubin, M.B., and Rushneck, D.R. J. Chromatog. Sci.. 1987, 25, 322 - 327.
4. "Compositing and Three-Stage Sampling", from Statistical Methods for Environmental
Monitoring. Gilbert, R.O. Editor, D. Van Nostrand, New York, 1987.
5. Garner, F.C., Stapanian, M.A., and Williams, L.R., "Composite Sampling for
Environmental Monitoring", from Principles of Environmental Sampling. Keith, L.H.
Editor, American Chemical Society, Washington DC, 1988.
6. Cline, S.M., and Severiri, B.F. Water Res.. 1989, 23(4) 407 - 412.
7. EPA 833-B-92-001, 1992
8. Stanko,G.H. Environmental Lab. 1994, 6(2) 10 - 15.
9. Hoaglin, D.C., Mosteller, F., and Tukey, J.S. Understanding Robust and Exploratory Data
Analysis. John Wiley and Sons, New York, 1983.
10. Snedecor, G.W. and Cochran, W.G. Statistical Methods (eighth edition). Iowa State
University Press, Ames, 1989.
September 1995 29
-------
-------
Appendix A
Phase I Data
-------
-------
Comparison of VOA Compositing Procedures
Phase I - Unspiked Field Sample Data
Analyte Concentration (jag/L)
ANALYTE
2-BUTANONE
2-PROPANONE
4-METHYL-2 -PENTANONE
CHLOROFORM
ETHYLBENZENE
ISOBUTYL ALCOHOL
M-XYLENE
0+P XYLENE
TETRACHLOROETHENE
TOLUENE
TRICHLOROFLUOROMETHANE
Mathematical
Composite
357.14
10744.84
105.78
180.08
22.74
26.30
41.82
29.94
45.82
181.85
32.90
Physical
Composite
178.53
7459.43
67.03
161.71
21.21
47.19
31.77
41.70
161.41
34.40
September 1995
A-l
-------
Comparison of VOA Compositing Procedures
Phase I - Spiked
Reagent Water
Data
Percent Recovery of Spikes
. ,
iiicfn C. oncent ration •
Mathematical
ANALYTE NAME
1,1, 1-TRICHLOROETHANE
1,1,2,2 -TETRACHLOROETHANE
1,1,2 -TRICHLOROETHANE
1 , 1-DICHLOROETHENE
1 , 2-DICHLOROETHANE
1 , 2-DICHLOROPROPANE
1,4-DIOXANE
2-BUTANONE
2-PROPANONE
2 -PRO PENAL
ACRYLONITRILE
BENZENE
BROMODICHLOROMETHANE
BROMOMETHANE
CHLOROBENZENE
CHLOROETHANE
CHLOROFORM
CHLOROMETHANE
DIBROMOCHLOROMETHANE
DIETHYL ETHER
ETHYLBENZENE
METHYLENE CHLORIDE
TETRACHLOROETHENE
TETRACHLOROMETHANE
TOLUENE
TRANS- 1, 2-DICHLOROETHENE
TRANS- 1 , 3-DICHLOROPROPENE
TRICHLOROETHENE
VINYL CHLORIDE
Composite
65.090
186.322
101.457
33.839
74.214
90.028
70.086
68.824
66.402
56.863
93.371
63.462
83.349
60.393
74.594
48. 000
78.140
51.208
87.038
86.957
66.712
79.693
63.577
48.719
76.557
36.805
8.392
86.775
38.895
Physical
Composite
84.630
104.438
112.564
71.735
81.336
101.859
98.706
82.143
82.180
65.999
92.072
78.418
97.070
58.326
86.913
38.372
71.504
38.725
96.361
84.197
87.389
97.755
78.527
96.309
94.174
50.857
7.890
120.956
21.150
A-2
September 1995
-------
Comparison of VOA Compositing Procedures
Phase I - Spiked Reagent Water Data
Percent Recovery of Spikes
ANALYTE NAME
1,1,1-TRICHLOROETHANE
1,1,2,2-TETRACHLOROETHANE
1,1,2-TRICHLOROETHANE
1,1-DICHLOROETHENE
1,2-DICHLOROETHANE
1,2-DICHLOROPROPANE
1,4-DIOXANE
2-BUTANONE
2-PROPANONE
2-PROPENAL
ACRYLONITRILE
BENZENE
BROMODICHLOROMETHANE
BROMOMETHANE
CHLOROBENZENE
CHLOROETHANE
CHLOROFORM
CHLOROMETHANE
DIBROMOCHLOROMETHANE
DIETHYL ETHER
ETHYLBENZENE
METHYLENE CHLORIDE
TETRACHLOROETHENE
TETRACHLOROMETHANE
TOLUENE
TRANS-1,2-DICHLOROETHENE
TRANS-1,3-DICHLOROPROPENE
TRICHLOROETHENE
VINYL CHLORIDE
. en u J. a u _Li_iii
Mathematical
Composite
33.288
167.883
106.369
45.451
77.358
91.312
76.002
80.217
90.481
64.039
99.959
48.498
80.002
50.303
78.741
35.325
69.5035
38.9250
82.1605
85.3305
74.1770
72.8565
70.4925
63.4920
57.1250
39.6740
10.7310
54.9185
23.0345
Physical
Composite
65
127
124
57
86
101
159
98
159
62
144
70
105
55
89
41
74
38
114
85
84
109
80
71
82
51
96
21
.347
.389
.057
.013
.549
.143
.430
.540
.593
.613
.573
.288
.830
.540
.123
.987
.761
.700
.159
.413
.400
.240
.151
.291
.931
.291
.264
.433
September 1995
A-3
-------
-------
Appendix B
Phase II Data
-------
-------
Comparison of VOA Compositing Procedures
Phase II Data - Percent of Spike Recoveries
JT -L d. o JS. ^ CJiUpCJ t> _L 1 — LI1CJ
Mathematical
EPISODE
4559
4561
4563
4559
4561
4563
4559
4561
4563
4559
4561
4563
4559
4561
4563
4559
4561
4563
4559
4561
4563
4559
4561
4563
4559
4561
4563
4559
4561
4563
4559
4561
4563
4559
4561
4563
4559
4561
4563
4559
4561
4563
4559
4561
4563
ANALYTE
1,1,2, 2 -TETRACHLOROETHANE
1,1,2, 2 -TETRACHLOROETHANE
1,1,2, 2 -TETPACHLOROETHANE
1,1,2 -TRICHLOROETHANE
1 , 1 , 2 -TRICHLOROETHANE
1,1, 2 -TRICHLOROETHANE
1, 1-DICHLOROETHANE
1, 1-DICHLOROETHANE
1, 1-DICHLOROETHANE
1, 1-DICHLOROETHENE
1 , 1-DICHLOROETHENE
1 , 1-DICHLOROETHENE
1 , 2 -DICHLOROETHANE
1 , 2 -DICHLOROETHANE
1 , 2 -DICHLOROETHANE
1 , 2 -DICHLOROPROPANE
1 , 2 -DICHLOROPROPANE
1 , 2 -DICHLOROPROPANE
2-HEXANONE
2-HEXANONE
2-HEXANONE
4 -METHYL- 2 - PENTANONE
4 -METHYL- 2 - PENTANONE
4 -METHYL- 2 - PENTANONE
ACETONE
ACETONE
ACETONE
ACROLEIN
ACROLEIN
ACROLEIN
ACRYLONITRILE
ACRYLONITRILE
ACRYLONITRILE
BENZENE
BENZENE
BENZENE
BROMODICHLOROMETHANE
BROMODICHLOROMETHANE
BROMODICHLOROMETHANE
BROMOFORM
BROMOFORM
BROMOFORM
BROMOMETHANE
BROMOMETHANE
BROMOMETHANE
Composite
99
104
102
103
105
103
108
106
103
124
101
100
100
102
100
106
104
99
1003
351
295
198
184
883
356
386
821
52
67
66
108
95
96
160
105
103
105
109
102
105
136
103
179
105
101
.4
.2
.8
.4
.9
.5
.4
.0
.6
.8
.9
.8
.3
.4
.6
.3
.9
.6
.2
.3
.1
.3
.8
.5
.6
.7
.6
.8
.3
.6
.1
.5
.0
.4
.0
.5
.7
.2
.8
.8
.5
.2
.7
.5
.8
Physical
Composite
109
102
90
109
102
96
101
95
91
113
90
86
101
99
92
101
99
91
987
311
266
199
173
781
371
418
668
65
76
64
120
104
100
130
93
90
107
103
91
105
127
98
171
91
86
.2
.0
.9
.6
.6
.1
.4
.9
.9
.7
.9
.7
.9
.9
.5
.0
.0
.4
.2
.3
.0
.9
.3
.3
.3
.1
.1
.5
.2
.4
.7
.2
.2
.5
.7
.5
.6
.8
.2
.8
.9
.7
.8
.3
.2
B-l
September 1995
-------
Comparison ofVOA Compositing Procedures
Phase II Data - Percent of Spike Recoveries
EPISODE
4559
4561
4563
4559
4561
4563
4559
4561
4563
4559
4561
4563
4559
4561
4563
4559
4561
4563
4559
4561
4563
4559
4561
4563
4559
4561
4563
4559
4561
4563
4559
4561
4563
4559
4561
4563
4559
4561
4563
4559
4561
4563
4559
4561
4563
4559
rj-dojs. ^uun_jus> j- u -Liiy \^^u
ANALYTE
CARBON DISULFIDE
CARBON DISULFIDE
CARBON DISULFIDE
CARBON TETRACHLORIDE
CARBON TETRACHLORIDE
CARBON TETRACHLORIDE
CHLOROBENZENE
CHLOROBENZENE
CHLOROBENZENE
CHLOROETHANE
CHLOROETHANE
CHLOROETHANE
CHLOROFORM
CHLOROFORM
CHLOROFORM
CHLOROMETHANE
CHLOROMETHANE
CHLOROMETHANE
CIS-1, 3-DICHLOROPROPENE
CIS-1, 3-DICHLOROPROPENE
CIS-1, 3-DICHLOROPROPENE
DIBROMOCHLOROMETHANE
DIBROMOCHLOROMETHANE
DIBROMOCHLOROMETHANE
DIETHYL ETHER
DIETHYL ETHER
DIETHYL ETHER
ETHYL BENZENE
ETHYL BENZENE
ETHYL BENZENE
M-XYLENE
M-XYLENE
M-XYLENE
METHYL ETHYL KETONE
METHYL ETHYL KETONE
METHYL ETHYL KETONE
METHYLENE CHLORIDE
METHYLENE CHLORIDE
METHYLENE CHLORIDE
0- + P-XYLENE
O- + P-XYLENE
0- + P-XYLENE
P-DIOXANE
P-DIOXANE
P-DIOXANE
TETRACHLOROETHENE
• i- ;
Mathematical
Composite
284.3
258.3
254.6
116.0
98.8
97.5
105.5
224.2
105.4
137.0
99.9
100.9
123.3
108.1
103.6
302.3
107.7
100.1
331.1
307.8
306.4
112.5
114.0
105.6
107.1
101.5
99.8
106.0
199.1
163.1
65.3
363.9
137.0
100.7
103.3
184.5
120.2
98.1
140.3
73.7
213.6
84.5
79.9
96.6
373 .0
115.0
Physical
Composite
251.8
226.4
198.0
101.1
92.6
78.6
100.3
183.1
94.6
116.3
86.9
82.9
116.0
99.4
88.1
286.6
93.5
84.5
336.9
298.9
261.6
112.2
108.7
97.0
110.4
101.5
93 .5
98.8
170.6
129.0
62.3
279.3
123.2
104.2
109.1
157.5
114.4
91.7
121.6
70.9
178.8
79.3
76.3
89.3
214.5
102.2
September 1995
B-2
-------
Comparison of VOA Compositing Procedures
Phase II Data - Percent of Spike Recoveries
Flask Compositing (Cont')
EPISODE ANALYTE
4561 TETRACHLOROETHENE
4563 TETRACHLOROETHENE
4559 TOLUENE
4561 TOLUENE
4563 TOLUENE
4559 TRANS-1,3-DICHLOROPROPENE
4561 TRANS-1,3-DICHLOROPROPENE
4563 TRANS-1,3-DICHLOROPROPENE
4559 TRICHLOROETHENE
4561 TRICHLOROETHENE
4563 TRICHLOROETHENE
4559 TRICHLOROFLUOROMETHANE
4561 TRICHLOROFLUOROMETHANE
4563 TRICHLOROFLUOROMETHANE
4559 VINYL CHLORIDE
4561 VINYL CHLORIDE
4563 VINYL CHLORIDE
Mathematical
Composite
108.0
105.6
110.3
104.7
121.6
102.0
93.8
95.6
118.6
163.2
105.4
77.5
63 .2
59.1
210.1
105.2
99.0
Physical
Composite
99.7
95.3
102.6
96.0
103.9
101.0
84.6
81.1
109.9
144.4
93.3
65.7
54.5
47.8
187.0
93.0
85.7
B-3
September 1995
-------
Comparison ofVOA Compositing Procedures
Phase II Data - Percent of Spike Recoveries
Purcfs Device Compositing —
Mathematical
EPISODE
4573
4575
4593
4595
4573
4575
4593
4595
4573
4575
4593
4595
4573
4575
4593
4595
4573
4575
4593
4595
4573
4575
4593
4595
4573
4575
4593
4595
4573
4575
4593
4595
4573
4575
4593
4595
4573
4575
4593
4595
4573
4575
4593
4595
4573
4575
ANALYTE
1,1,2, 2 -TETRACHLOROETHANE
1,1,2, 2 -TETRACHLOROETHANE
1,1,2, 2 -TETRACHLOROETHANE
1,1,2, 2 -TETRACHLOROETHANE
1,1, 2 -TRICHLOROETHANE
1,1, 2 -TRICHLOROETHANE
1,1, 2 -TRICHLOROETHANE
1,1,2 -TRICHLOROETHANE
1 , 1-DICHLOROETHANE
1, 1-DICHLOROETHANE
1 , 1-DICHLOROETHANE
1 , 1-DICHLOROETHANE
1 , 1-DICHLOROETHENE
1 , 1-DICHLOROETHENE
1 , 1-DICHLOROETHENE
1 , 1-DICHLOROETHENE
1 , 2 -DICHLOROETHANE
1 , 2 -DICHLOROETHANE
1 , 2 -DICHLOROETHANE
1 , 2 -DICHLOROETHANE
1 , 2 -DICHLOROPROPANE
1 , 2 -DICHLOROPROPANE
1 , 2 -DICHLOROPROPANE
1 , 2 -DICHLOROPROPANE
2-HEXANONE
2-HEXANONE
2-HEXANONE
2-HEXANONE
4 -METHYL- 2 - PENTANONE
4 -METHYL- 2 - PENTANONE
4 -METHYL- 2 -PENTANONE
4 -METHYL- 2 -PENTANONE
ACETONE
ACETONE
ACETONE
ACETONE
ACROLEIN
ACROLEIN
ACROLEIN
ACROLEIN
ACRYLONITRILE
ACRYLONITRILE
ACRYLONITRILE
ACRYLONITRILE
BENZENE
BENZENE
Composite
91
97
116
99
97
90
101
89
97
92
98
108
98
88
96
92
96
91
98
97
94
93
102
94
341
316
457
330
205
167
263
169
68
135
79
58
63
16
23
140
103
106
111
98
90
91
.5
.9
.6
.2
.5
.7
.2
.8
.1
.0
.7
.4
.3
.7
.8
.4
.3
.9
.4
.2
.5
.2
.6
.9
.9
.6
.8
.6
.5
.4
.6
.6
.2
.2
.2
.0
.5
.2
.3
.7
.4
.0
.3
.3
.5
.7
Physical
Composite
94
99
117
94
85
88
93
81
79
86
90
89
77
79
87
76
83
87
92
85
81
90
95
83
301
317
423
316
182
159
229
170
62
120
90
44
71
9
12
5
96
108
103
98
73
83
.4
.6
.6
.4
.1
.6
.7
.7
.3
.4
.4
.8
.1
.2
.0
.2
.0
.9
.4
.2
.0
.7
.8
.8
.8
.1
.7
.6
.6
.1
.2
.4
.3
.5
.8
.6
.9
.6
.2
.2
.2
.0
.9
.8
.0
. 6
September 1995
B-4
-------
Comparison ofVOA Compositing Procedures
EPISODE
4593
4595
4573
4575
4593
4595
4573
4575
4593
4595
4573
4575
4593
4595
4573
4575
4593
4595
4573
4575
4593
4595
4573
4575
4593
4595
4573
4575
4593
4595
4573
4575
4593
4595
4573
4575
4593
4595
4573
4575
4593
4595
4573
4575
4593
4595
Phase II Data - Percent of Spike
Purge Device Compositincj
ANALYTE
BENZENE
BENZENE
BROMODICHLOROMETHANE
BROMODICHLOROMETHANE
BROMODICHLOROMETHANE
BROMODICHLOROMETHANE
BROMOFORM
BROMOFORM
BROMOFORM
BROMOFORM
BROMOMETHANE
BROMOMETHANE
BROMOMETHANE
BROMOMETHANE
CARBON BISULFIDE
CARBON DISULFIDE
CARBON DISULFIDE
CARBON DISULFIDE
CARBON TETRACHLORIDE
CARBON TETRACHLORIDE
CARBON TETRACHLORIDE
CARBON TETRACHLORIDE
CHLOROBENZENE
CHLOROBENZENE
CHLOROBENZENE
CHLOROBENZENE
CHLOROETHANE
CHLOROETHANE
CHLOROETHANE
CHLOROETHANE
CHLOROFORM
CHLOROFORM
CHLOROFORM
CHLOROFORM
CHLOROMETHANE
CHLOROMETHANE
CHLOROMETHANE
CHLOROMETHANE
CIS-1, 3-DICHLOROPROPENE
CIS-1, 3-DICHLOROPROPENE
CIS-1, 3-DICHLOROPROPENE
CIS-1, 3-DICHLOROPROPENE
DIBROMOCHLOROMETHANE
DIBROMOCHLOROMETHANE
DIBROMOCHLOROMETHANE
DIBROMOCHLOROMETHANE
; Recover:
(Cont ' )
Mathemat:
ies
ical
Composite
98
90
92
92
97
92
99
98
101
113
97
94
110
101
240
217
241
225
101
94
99
198
115
94
131
95
98
88
96
104
97
83
103
91
102
95
105
101
317
280
292
296
96
89
97
97
.9
.4
.8
.6
.0
.1
.0
.7
.2
.3
.3
.7
.2
.2
.2
.7
.4
.0
.1
.9
.5
.6
.3
.4
.5
.9
.7
.2
.0
.5
.1
.9
.0
.2
.6
.6
.0
.4
.8
.0
.4
.0
.2
.2
.8
.0
Physical
Composite
92
76
80
83
89
81
89
77
74
83
83
86
97
83
183
196
221
185
81
81
87
181
82
86
118
83
79
82
88
86
78
78
95
78
80
81
95
82
271
259
247
255
84
84
89
87
.7
.2
.1
.7
.4
.8
.4
.9
.6
.7
.8
.6
.2
.4
.3
.9
.8
.9
.7
.7
.0
.7
.3
.6
.1
.0
.2
.2
.9
.2
.7
.8
.7
.6
.0
.7
.3
.3
.8
.5
.3
.2
.4
.4
.1
.3
B-5
September 1995
-------
Comparison ofVOA Compositing Procedures
EPISODE
4573
4575
4593
4595
4573
4575
4593
4595
4573
4575
4593
4595
4573
4575
4593
4595
4573
4575
4593
4595
4573
4575
4593
4595
4573
4575
4593
4595
4573
4575
4593
4595
4573
4575
4593
4595
4573
4575
4593
4595
4573
4575
4593
4595
4573
4575
4593
Phase II Data - Percent of Spi>
Purcfe Device Compositincf (
iy
ANALYTE
DIETHYL ETHER
DIETHYL ETHER
DIETHYL ETHER
DIETHYL ETHER
ETHYL BENZENE
ETHYL BENZENE
ETHYL BENZENE
ETHYL BENZENE
M-XYLENE
M-XYLENE
M-XYLENE
M-XYLENE
METHYL ETHYL KETONE
METHYL ETHYL KETONE
METHYL ETHYL KETONE
METHYL ETHYL KETONE
METHYLENE CHLORIDE
METHYLENE CHLORIDE
METHYLENE CHLORIDE
METHYLENE CHLORIDE
O- + P-XYLENE
O- + P-XYLENE
O- + P-XYLENE
O- + P-XYLENE
P-DIOXANE
P-DIOXANE
P-DIOXANE
P-DIOXANE
TETRACHLOROETHENE
TETRACHLOROETHENE
TETRACHLOROETHENE
TETRACHLOROETHENE
TOLUENE
TOLUENE
TOLUENE
TOLUENE
TRANS- 1, 3-DICHLOROPROPENE
TRANS- 1, 3-DICHLOROPROPENE
TRANS- 1, 3-DICHLOROPROPENE
TRANS- 1, 3-DICHLOROPROPENE
TRICHLOROETHENE
TRICHLOROETHENE
TRICHLOROETHENE
TRICHLOROETHENE
TRICHLOROFLUOROMETHANE
TRICHLOROFLUOROMETHANE
TRICHLOROFLUOROMETHANE
:e Recov<
iCont' )
lathemat
eries
ical
Composite
94
101
112
91
97
93
56
95
46
32
141
56
79
103
99
102
86
76
93
84
43
40
120
58
87
100
98
126
92
84
95
92
94
91
54
100
96
80
93
84
103
83
93
95
.6
.2
.8
.3
.7
.5
.3
.8
.8
.4
.5
.8
.1
.2
.8
.5
.0
.3
.8
.8
.3
.9
.9
.7
.1
.0
.7
.6
.4
.8
.3
.6
.8
.3
.7
.6
.4
.0
.1
.8
.2
.8
.6
.4
.
Physical
Composite
82
100
102
71
74
83
48
78
34
33
78
44
74
103
100
103
72
72
88
72
37
40
79
48
83
110
98
117
80
76
83
81
72
82
49
48
81
78
91
102
81
77
83
81
.9
.6
.0
.3
.6
.7
.8
.1
.1
.7
.9
.9
.3
.0
.8
.2
.4
.6
.1
.5
.5
.0
.4
.8
.0
.2
.7
.8
.4
.2
.6
.1
.1
.9
.5
.9
.1
.9
.1
.7
.6
.0
.1
.4
September 1995
B-6
-------
Comparison of VOA Compositing Procedures
Phase II Data - Percent of Spike Recoveries
EPISODE
4595
4573
4573
4575
4593
4595
Purge Device Compositing (Conf)
Mathematical
ANALYTE Composite
TRICHLOROFLUOROMETHANE
VINYL ACETATE
VINYL CHLORIDE
VINYL CHLORIDE
VINYL CHLORIDE
VINYL CHLORIDE
240.0
97.1
91.0
104.1
103.3
Physical
Composite
217.9
74.9
81.4
92.9
84.3
B-7
September 1995
-------
-------
Appendix C
Phase III Data
-------
-------
Comparison of VOA Compositing Procedures
EPISODE
4617
4618
4617
4618
4617
4618
4617
4618
4617
4618
4617
4618
4617
4618
4617
4618
4617
4618
4617
4618
4617
4618
4617
4618
4617
4618
4617
4618
4617
4618
4617
4618
4617
4618
4617
4618
4617
4618
4617
4618
4617
4618
4617
4618
4617
4618
4617
4618
4617
4618
4617
4618
4617
4618
4617
4618
4617
4618
4617
4618
Phase III Data
ANALYTE
1,1,1 -TRICHLOROETHANE
1,1,1 -TRICHLOROETHANE
1,1,2,2 -TETRACHLOROETHANE
1,1,2, 2 -TETRACHLOROETHANE
1,1,2 -TRICHLOROETHANE
1,1,2 -TRICHLOROETHANE
1 , 1-DICHLOROETHANE
1 , 1-DICHLOROETHANE
1 , 1-DICHLOROETHENE
1 , 1-DICHLOROETHENE
1 , 2 -DICHLOROETHANE
1 , 2 -DICHLOROETHANE
1 , 2 -DICHLOROPROPANE
1 , 2 -DICHLOROPROPANE
2-CHLOROETHYLVINYL ETHER
2-CHLOROETHYLVINYL ETHER
ACRYLONITRILE
ACRYLONITRILE
BENZENE
BENZENE
BROMODICHLOROMETHANE
BROMODICHLOROMETHANE
BROMOFORM
BROMOFORM
BROMOMETHANE
BROMOMETHANE
CARBON TETRACHLORIDE
CARBON TETRACHLORIDE
CHLOROBENZENE
CHLOROBENZENE
CHLOROETHANE
CHLOROETHANE
CHLOROFORM
CHLOROFORM
CHLOROMETHANE
CHLOROMETHANE
DIBROMOCHLOROMETHANE
DIBROMOCHLOROMETHANE
DIETHYL ETHER
DIETHYL ETHER
ETHYL BENZENE
ETHYL BENZENE
METHYL ETHYL KETONE
METHYL ETHYL KETONE
METHYLENE CHLORIDE
METHYLENE CHLORIDE
P-DIOXANE
P-DIOXANE
TETRACHLOROETHENE
TETRACHLOROETHENE
TOLUENE
TOLUENE
TRANS-1, 2-DICHLOROETHENE
TRANS- 1, 2-DICHLOROETHENE
TRANS-1 , 3 -DICHLOROPROPENE
TRANS-1, 3 -DICHLOROPROPENE
TRICHLOROETHENE
TRICHLOROETHENE
VINYL CHLORIDE
VINYL CHLORIDE
- Percent of Spike Recoveries
Mathematical Automated Automated
Composite
76.
67.
102.
107 .
86.
88.
79.
73 .
72.
66.
93 .
88.
83 .
78.
90.
101.
100.
110.
101 .
74.
72 .
89.
46.
89.
78.
79.
55.
66.
91.
79.
82.
78.
89.
83 ,
84,
80.
55,
85,
106
106
77
70
103
126
104
85
62
102
69
63
75
71
77
71
79
82
72
65
78
75
1
7
4
4
8
4
5
2
r
7
8
2
7
4
9
7
5
7
4
6
6
3
4
, 0
, 8
, 1
2
.2
. 5
. 0
. 5
. 6
2
. 5
.1
. 0
. 3
. 5
.6
. 2
.8
. 0
.6
. 8
.7
. 1
. 6
. 0
.9
.9
.2
. 1
. 3
.4
. 3
.6
.2
. 1
Sampler
78.
72.
115.
111.
93.
91.
80.
77.
79.
70.
95.
94.
81.
82.
117.
121.
109.
114.
107 .
77.
72.
92.
33 .
81.
81.
82.
56.
67.
95.
80.
88.
81.
97.
86.
91.
85.
54.
90.
112,
111.
81,
71
96,
125
101
90
52
108
74
62
77
73
92
75
83
82
69
67
85
79
9
4
9
4
7
1
7
3
4
6
5
1
6
0
3
0
5
1
4
8
7
5
7
5
3
9
0
2
9
1
.6
.9
.8
.1
.1
.3
.6
.7
.2
.2
.1
.3
.9
.1
.3
.4
.0
.0
.9
.8
.8
.8
.2
.0
.6
.1
.4
.1
.1
.0
Compositor
63 .
61.
87.
107 .
82.
90.
73 .
71.
62.
57.
87 .
88.
75.
78.
71.
113 .
96.
113 .
97 .
73 .
59.
85.
26.
97.
69.
77 .
38.
37 .
76.
63 .
75.
74.
91.
80.
80.
78.
36.
84.
106
111
60
55
120
128
93
86
57
101
52
40
54
60
68
68
54
71
55
51
68
69
9
4
7
1
0
5
0
3
4
7
6
7
3
0
8
3
6
2
3
1
.2
7
2
.5
.6
.2
.9
, 1
.1
.9
.7
.3
.4
.2
.1
.2
.4
.9
.8
.6
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.6
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. 6
.5
.3
.6
.4
.0
.6
.5
.1
.1
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.2
.7
.5
Physical
Composite
61.
55.
86.
106.
85.
77.
62.
61.
60.
52.
83.
85.
68.
70 .
112.
109.
106.
114 .
82 .
62.
61.
80 .
126.
64.
65.
48.
54.
78.
70.
66.
60.
75.
70.
67.
61.
55,
86.
92,
100,
72
59
92
132
91
73
73
109
69
49
48
58
66
58
71
65
61
51
60
57
4
5
4
8
8
3
8
9
6
5
2
0
5
9
6
6
5
8
8
5
2
2
8
2
.9
.2
.6
,2
.3
,3
.3
.4
.2
.3
.9
.3
. 6
.6
.0
.1
.7
.7
.0
.4
.8
.4
.9
.4
.7
.5
.9
.6
.4
.8
.1
.5
.7
.2
.9
C-l
September 1995
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