United States
Environmental Protection
Agency
Environmental Monitoring and
Support Laboratory
Cincinnati OH 45268
Research and Development
EPA-600/S4-84-042 June 1984
&EPA Project Summary
EPA Method Study 25, Method
602, Purgeable Aromatics
Beverly J. Warner, Julie M. Finke, Roger C. Gable, John E. Strobel, Arthur
D. Snyder, and Carl R. McMillin
Described herein are the experimental
design and the results of an interlabora-
tory study of an analytical method for
detecting purgeable aromatics in water.
EPA Method 602, Purgeable Aromatics,
employs a purge-and-trap chromato-
graphic technique for determining
seven aromatic hydrocarbon analytes in
water matrices. Three Youden pairs of
spiking solutions were used and con-
tained benzene, chlorobenzene, 1,2-
dichlorobenzene, 1,3-dichlorobenzene,
1,4-dichlorobenzene, ethylbenzene, and
toluene., Six water types were used:
distilled water, drinking water, surface
water, and three wastewater samples
from industries employing or producing
aromatic hydrocarbons. Twenty labora-
tories participated and supplied their
individual distilled, drinking, and surface
water samples. Monsanto Company
supplied the three industrial waste-
water samples. The statistical analyses
and conclusions reached in this report
are based on the analytical data obtained
by the 20 participating laboratories.
Participating laboratories were selec-
ted based upon technical evaluation of
proposals and upon the analytical
results of prestudy samples. The data
obtained from the interlaboratory study
were analyzed employing a series of
computer programs known as the
Interlaboratory Method Validation
Study (IMVS) system, which was
designed to implement the concepts
recommended in ASTM Procedure D
2777. The statistical analyses included
tests for the rejection of outliers,
estimation of mean recovery (accuracy),
estimation of single-analyst and overall
precision, and tests for the effects of
water type on accuracy and precision.
This Project Summary was developed
by EPA's Environmental Monitoring and
Support Laboratory, Cincinnati, OH, to
announce key findings of the research
project that is fully documented in a.
separate report of the same title (see
Project Report ordering information at
back).
Introduction
The various analytical laboratories of
. the U.S. Environmental Protection Agency
(EPA) gather water quality data to provide
information on water resources, to assist
research activities, and to evaluate
pollution abatement activities. The success
of the Agency's pollution control activities,
particularly when legal action is involved,
depends upon the reliability of the data,
provided by the laboratories.
Under provisions of the Clean Water
Act, the EPA is required to promulgate
guidelines establishing test procedures;
for the analysis of pollutants. The Clean
Water Act Amendments of 1977 empha-
size the control of toxic pollutants and
declare the 65 "priority" pollutants and
classes of pollutants to be toxic under
Section 307(a) of the Act. This report is one
of a series that investigates the analytical
behavior of selected priority pollutants and;
suggests a suitable test procedure for
their measurement. The priority pollutants
to be analyzed by Method 602 covered by
this report are the following purgeable
aromatics:
benzene
chlorobenzene
1,2-dichlorobenzene
1,3-dichlorobenzene
1,4-dichlorobenzene
ethylbenzene
toluene
The Environmental Monitoring and
Support Laboratory - Cincinnati (EMSL-
Cl) of the EPA develops analytical
methods and conducts a quality assurance
program for the water laboratories. This
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program is designed to maximize the
reliability and legal defensibility of all
water quality information collected by
EPA laboratories. The responsibility for
these activities is assigned to the Quality
Assurance Branch (QAB), one of whose
activities is to conduct interlaboratory
tests of the methods. This report presents
the results of interlaboratory study 25 on
EPA Method 602, Purgeable Aromatics.
Procedure
The study consisted of three distinct
phases. Phase I involved the analysis of
the prestudy samples by 20 participating
laboratories. Two samples were analyzed
for each of the seven purgeable aromatics;
a medium concentration sample to be
analyzed in drinking water supplied by
the participating laboratories and a low
level sample to be analyzed in a wastewa-
ter sample supplied by Monsanto Com-
pany. The objective of Phase I was to
become familiar with the methodology
employed and to identify any potential
problems associated with the analytical
methodology. Accuracy was not as
important as familiarity with the method-
ology. A short report, including the data
obtained and any potential problems
encountered, was received by Monsanto
Company from each subcontracting
laboratory at the completion of Phase I.
Phase II consisted of a prestudy con-
ference held at EMSL-CI, Cincinnati,
Ohio. Each subcontracting laboratory
sent at least one participant to the meet-
ing. The analyst, or principal analyst if
more than one was involved, attended
this meeting, which was held after the
data from the prestudy had been
evaluated, and was designed to examine
the results of the prestudy and to discuss
any problems encountered in the
methodology.
Phase 111 consisted of the formal
interlaboratory study. Each of the seven
aromatic purgeables were analyzed at six
concentrations (three Youden pairs) in six
different watermatrices. Trie participatihcfr
laboratories each supplied its own
distilled water, drinking water and
surface water. Monsanto Company
supplied the three industrial wastewaters.
In addition, the participating laboratories
performed analyses of all water blanks
with no spiked compounds. Each partici-
pating laboratory then issued a report to
Monsanto Company containing all data
obtained, copies of all chromatograms,
and any comments.
The final step in the study was to
conduct a statistical analysis of all data
obtained. This analysis was conducted by
Battelle Columbus laboratories, Colum-
bus, Ohio under contract 68-03-2624
employing a system of computer programs
known as the Interlaboratory Method
Validation Study (IMVS) system.
Results and Discussion
The object of this study was to
characterize the performance of EPA
Method 602 in terms of accuracy, overall
precision, single-arialyst precision and
the effect of water types on accuracy and
precision. Through statistical analyses of
5,040 analytical values, estimates of
accuracy and precision wesre made and
expressed as regression equations.
Which are shown irrTable'-T:"31" "~—s~-».-.
The accuracy of the method is obtained
by comparing the mean recovery to the
true values of the concentration. Expressed
as percent recovery it ranges from 88% to
97% in distilled, tap, and surface water.
Excluding the values where large inter-
ferences entered into play, the accuracy
in wastewaters ranges ifrom 84% to
100%. Large interferences (background)
existed in wastewater 5 for chlorobenzene
and toluene. At the lowest concentration
levels, recoveries exceeding 500% were
reported. At the middle and high levels,
Table 1. Regression Equations for Accuracy and Precision
Water Type Benzene Chlorobenzene
1,2-Dichlorobenzene
1,3-Dichlorobenzene
Distilled Water
Single-Analyst Precision
Overall Precision
Accuracy
Tap Water
Single-analyst Precision
Overall Precision
Accuracy
Surface Water
Single-Analyst Precision
Overall Precision
Accuracy
Waste Water 1
Single-Analyst Precision
•. Overall Precision
Accuracy
Waste Water 2
Single-Analyst Precision
Overall Precision
Accuracy
Waste Water 3
Single-Analyst^ Precision
Overall Precision
Accuracy
SR = 0.09X + 0.59
S = 0.21 X +0.56
X =0.920 + 0.57
SR = 0.11 X-0.06
S = 0.22X+1.11
X =0.970 + 0.05
= 0.08X + O.17
=0.19X + 0.38
=0.930 + 0.37
SR = 0.13X +0.56
S =0.26X + 0.69
X =0.910 + 0.06
SR = 0.09X + 0.89
S = 0.25X + 0.97
X = 0.870 + 0.36
SR = 0.10X + 0.43
S = 0.25X + 0.58
X = 0.93C + 0.50
SR = 0.09X + 0.23
S = 0.17X + 0.10
X = 0.950 + 0.02
SR = 0.10X + 0.12
S =0.16X + 0.36
X = 0.940 + 0.12
SR = 0.08X + 0.14
S = 0.19X + 0.20
X = 0.920 - 0.14
SR = 0.08X + 3.02
S = 0.21 X +2.33
X = 0.930 + 1.85
SR = 0.09X+ 14.83
S =0.31X + 11.81
X =0.630+19.77
SR = 0.10X + 0.43
S = 0.16X + 0.85
X = 0.920 + 0.15
SR = 0.17X-0.04
S = 0.22X + 0.53
X = 0.930 + 0.52
SR = 0.10X + 0.42
S = 0.18X + 0.28
X =0.910 + 0.44
SR = 0.10X + 0.04
S =0.18X + 0.12
X =0.890+0.21
= 0.11X + 0.93
=0.25X + 0.37
=0.900 + 0.38
SR = 0.10X + 0.90
S =0.17X+1.12
X =0.950 + 0.69
SR = 0.15X + 0.14
S =0.18X + 0.51
X =0.880-0.39
SR = 0.15X - 0.10
S = 0.19X + 0.09
X = 0.960 - 0.04
SR = 0.08X + 0.33
S = 0.15X + 0.33
X =0.930 + 0.21
SR = 0.10X + 0.01
S = 0.18X + 0.80
X = 0.930 + 0.40
SR = 0.15X + 0.46
S =0.36X + 0.83
X = 1,000 + 3.36
SR = 0.10X + 0.52
S =0.19X + 0.79
X = 0.920 + 0.50
SR = 0.12X +0.29
S =0.16X + 0.43
X = 0.940 + 0.16
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average recoveries were 94% and 86%,
respectively, for chlorobenzene and
toluene.
The overall standard deviation indicates
the precision associated with measure-
ments generated by a group of laboratories.
The percent relative standard deviation
(%RSD) ranges from 9.9% to 39.8% for the
middle and high Youden pairs. The low
Youden pair ranges from 20.9% to 55% in
distilled, tap, and surface water..The
range in wastewater is 30.5% to 63.7%
excluding chlorobenzene and toluene. In
all cases, the highest %RSD (poorest
precision) was at the lowest Youden pair.
The single-analyst standard deviation
indicates the precision associated within
a single laboratory. The percent relative
standard deviation-for a single-analyst
(%RSD-SA) ranges from 6.1% to 31.8%
for the middle and high Youden pair. The
low Youden pair ranges from 9.0% to
33.7% for distilled, tap, and surface
water. The range in wastewaters is
20.9% to 43.5%, excluding chlorobenzene
and toluene. In all cases, the highest
%RSD-SA (poorest precision) was at the
lowest Youden pair.
A statistical comparison of the effect of
water type was performed indicating a
statistically significant difference for six
of the analyte/water matrix combinations.
Of these six cases, a practical significant
difference was established in only two
cases; chlorobenzene and toluene in
water 5.
Conclusions and
Recommendations
EPA Method 602 is recommended for
the analysis of purgeable aromatics in
munipipal and industrial wastewaters. The
accuracy and precision are acceptable,
while the matrix effects are significant
only at low concentration levels.
Because deposition of high-boiling
compounds and column bleed onto the
photoionization detector (PID) lamp
window causes a continual loss' of
detector response, frequent cleaning of
the lamp window is recommended. This
may be alleviated by not exceeding the
column temperature 90°C recommended
in EPA Method 602. Venting of the
column at higher temperature (e.g.,
150°C) through the detector can lead to
fouling of the detector window.
Potential carry-over problems from
contaminated water can be lessened or
eliminated by analyzing a blank sample
prior to the next water sample.
Care must be taken in the preparation
of laboratory pure water. Contamination
from solvents in the atmosphere is
common.
Teflon is not recommended for gas
lines. Methylene chloride permeates the
Teflon, and naphthalene, which is used
as a lubricant in the drawing of the
Teflon, responds to the PID. Cooper or
stainless steel gas lines are recommended.
Table 1. {continued)
Water Type
Distilled Water
Single-Analyst Precision
Overall Precision
Accuracy
1 , 4-Dichlprobenzene
SR = 0. 15X + 0.28
S = 0.20X + 0.41
X = 0.93C - 0.09
Ethylbenzene
SR= 0.1 7X + 0.46
S =0.26X + 0.23
X =0.940 + 0.31
Toluene
SR = 0.09X + 0.48
S =0.18X + 0.7J
X =0.940 + 0.65
Tap Water
Single-Analyst Precision
Overall Precision
Accuracy
Surface Water
Single-Analyst Precision
Overall Precision
Accuracy
Waste Water 1
Single-Analyst Precision
Overall Precision
Accuracy
Waste Water 2
Single-Analyst Precision
Overall Precision
Accuracy
Waste Water 3
Single-Analyst Precision
Overall Precision
Accuracy
SR = 0.09 X + 0.39
S =0.15X + 0.39
X =0.910 + 0.26
SR = 0.17X -0.06
S =0.17X + 0.55
X = 0.880 + 0.27
SR = 0.07X + 0.85
S =0.18X + 0.59
X =0.89C + O.54
SR = 0.10X + 0.88
S =0.17X + 0.49
X = 0.930 + 0.33
SR = 0.09X + 0.34
S =0.15X + 0.33
X =0.910 + 0.11
SR = 0.10X + 0.18
S =0.20X + 0.68
X = 0.970 + 0.41
SR = 0.08X + 0.33
S = 0.71 X +0.36
X = O.93C + 0.7O
SR = 0.12X + 0.38
S = 0.21 X + 0.40
X = 0.940 + 0.38
SR = 0.11X + 0.45
S = 0.250 + 0.53
X = 0.860 + 0.14
SR = 0.13X + 0.52
S =0.20X + 0.78
X =0.690 + 0.73
SR = 0.10X + 0.18
S = 0.21X + 0.16
X =0.94C + O.17
SR = 0.05X+O.18
S = 0.25X + 0.33
X =0.930 + 0.02
SR=0.11X + 1.05
S =0.24X + 0.67
X =0.870 + 0.99
SR=0.18X + 3.47
S =0.28X + 4.36
X =0.710 + 8.63
SR = 0.10X + 1.20
S = 0.21X + 1.55
X =0.910+1.01
X = Mean Recovery
0 = True Value for the Concentration
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Beverly J. Warner, Julie M. Finke, Roger C. Gable, John E. Strobel, Arthur D.
Snyder, and CarlR. McMillin are with Monsanto Company, Dayton, OH 45407.
Raymond Wessefman is the EPA Project Officer (see below).
The complete report, entitled "EPA Method Study 25, Method 602—Purgeable
Aromatics," (Order No. PB 84-196 682; Cost: $16.00, subjectto change) will be
available only from:
National Technical Information Service
5285 Port Royal Road
Springfield. VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Environmental Monitoring and Support Laboratory
U.S. Environmental Protection Agency
Cincinnati, OH 45268
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