United States
Environmental Protect
Agency
on
Environmental Monitoring and
Support Laboratory
Cincinnati OH 45268
Research and Development
EPA-600/S4-84-056 Aug. 1984
AEPA Project Summary
EPA Met
hod Study 16
Method 606 — Phthalate Esters
John D. Millar, Richard E. Thomas, and Herbert J. Schattenberg
This report describes the results
obtained and data ; nalysis from an
interlaboratory method study of EPA
Method 606 (Phthalate Esters). The
method is designed to analyze for six
phthalate esters: dimethyl phthalate,
diethyl phthalate, di-rji-butyl phthalate,
benzylbutyl phthalate' bis-2-ethylhexyl
phthalate, and di-n-oetyl phthalate, in
water and wastewater. As tested here,
the method utilizes three 60-mL extrac-
tions with dichloromethane, cleanup/
separation on a Florisil or alumina
column, and injection into a gas
chromatograph equipped with an elec-
tron capture detectorf
The study design required the analyst
to dose six waters with each of six
mixtures of the six phthalates. The six
dosing levels represented three Youden
pairs, one each at a low, an intermediate,
and a high level. The six waters used
were a laboratory pure water, a finished
drinking water, and a surface water, all
collected by the participant, and three
low-background industrial effluents
provided by the prime contractor. A
total of 16 laboratories participated in
the study. I
The method was studied to estimate
the accuracy* and precision that can be
expected, including effects on accuracy
and precision of analysis of different
matrices. In addition, results of method
detection limit and analytical curve
studies and qualitative assessments of
the method based upon comments by
the participating laboratories are in-
cluded.
This Project Summary was developed
by EPA's Environmental Monitoring
and Support Laboratory, Cincinnati,
Ohio, to announce key findings of the
research project tfit t is fully docu-
mented in a separate report of the same
title (see project report ordering infor-
mation at back).
Introduction
EPA first promulgated guidelines
establishing test procedures for the
analysis of pollutants in 1973, following
the passage of the Federal Water Pollu-
tion Control Act in 1972 by Congress.
Pursuant to the amendment and publica-
tion of these guidelines, EPA entered into
a Settlement Agreement—the Consent
Decree—which required the study and, if
necessary, regulation of 65 "priority"
pollutants and classes of pollutants of
known or suspected toxicity to the biota.
Subsequently, Congress passed the
Clean Water Act of 1977, mandating the
control of toxic pollutants discharged into
ambient waters by industry.
In order to facilitate the implementation
of the Clean Water Act, EPA selected, for
initial study, 129 specific toxic pollutants,
113 organic and 16 inorganic. The
organic pollutants were divided into 12
categories based on their chemical
structure. Analytical methods were
developed by EPA for these 12 categories
through in-house and contracted research.
These analytical methods may eventually
be required for the monitoring of the 113
toxic pollutants in industrial wastewater
effluents, as specified by the Clean Water
Act of 1977.
As a logical subsequence to that work,
an interlaboratory study was conducted
to obtain accuracy and precision state-
ments for Method 606 {Phthalate Esters)
based upon multilaboratory data. This
report describes the work performed,
presents the data acquired, and gives the
conclusions drawn from the collaborative
effort.
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The six compounds undergoing analy-
sis in the interlaboratory study were
dimethyl phthalate (DMP), diethyl phtha-
late (DEP), di-n-butyl phthalate (DBP),
benrylbutyl phthalate (BBP), bis-2-ethyl-
hexyl phthalate (2EHP), and di-n-octyl
phthalate (OOP).
The objective of this interlaboratory
study was to obtain information about the
accuracy and precision associated with
measurements generated by Method
606. This objective was met through the
use of statistical analysis techniques
designed to extract and summarize the
relevant information about accuracy and
precision from the data reported by the
participating laboratories.
The algorithms required to perform the
statistical analyses have been integrated
into a system of computer programs
referred to as IMVS (Interlaboratory
Method Validation Study). The analyses
performed by IMVS include several tests
for the rejection of outliers (laboratories
and individual data points), summary
statistics by concentration level for mean
recovery (accuracy), overall and single-
analyst standard deviation (precision),
determination of the linear relationship
between mean recovery and concentra-
tion level, determination of the linear
relationship between precision statistics
and mean recovery, and a test for the
effect of water type on accuracy and pre-
cision.
Procedure
The study design was based on Youden's
original plan for collaborative evaluation
of precision and accuracy for analytical
methods. According to Youden's design,
samples are analyzed in pairs where each
sample of a pair has a slightly different
concentration of the constituent. The
analyst is directed to do a single analysis
and report one value for each sample, as
if for a normal, routine sample.
In this study, samples were prepared as
concentrates in sealed glass ampules and
shipped to the analyst with portions of
final effluents from manufacturing plants
from three relevant industries. Each
participating laboratory was responsible
for supplying laboratory pure water, a
finished drinking water, and a surface
water, thus giving a total of six water
matrices involved in the study. The
analyst was required to add an aliquot of
each concentrate to a volume of water
from each of the six waters and submit
the spiked water to analysis. Three pairs
of samples were used. One pair contained
the substances at what was considered to
be equivalent to a low level for the
industrial effluents; a second pair con-
tained the substances at an intermediate
level; and the third pair contained the
substances at a high level.
Before the formal study began, each
participant was sent a pair of ampules
(not one of the pairs used in the study) for
a trial analysis by Method 606. After
submitting data from these analyses to
SwRI, all participants met in Cincinnati to
discuss problems encountered during the
trial run.
Results and Discussion
The accuracy of the method could
generally be expressed as a linear
function of the true concentration. The
regression equations are shown in Table
1.
The precision of the method could
generally be expressed as a linear
function of the mean recovery, both as
single-analyst and overall standard
deviations. These regression equations
are also shown in Table 1.
The percent recovery of the method
differed from that obtained during the
developmental phase, especially for DMP
and DEP. Recoveries at the midrange of
the concentrations studied ranged from
33 to 93%, with a median of 78.5.
Twenty-nine of the thirty-six recoveries
were at or above 70%.
There was considerable variability
among the results, especially for DMP,
DEP, and 2EHP. High relative standard
deviations were determined for both
2EHP and DOP in laboratory pure water.
Six water types were used in this study:
laboratory pure, finished drinking, sur-
face, and three relatively interference-
free industrial effluents. Differences in
variability were noted for DEP and 2EHP
and differences in mean recovery for DOP
as a result of the comparison across
water types. These differences were
noted in comparison with the values
obtained for laboratory pure water.
The principal problem for the collabora-
tors was in attaining a consistent
background and avoiding interferences,
especially in the elutioh regions of DMP,
DEP, and 2EHP. Other problem areas
noted included Kuderna-Danish concen-
tration, which some analysts believed to
be the principal source of analyte losses.
There was a high rate of rejection of
data due to missing results, values
reported as below the laboratory's
detection limit, and statistical outliers.
Overall, almost 22% of the analyses were
excluded from statistical treatment.
Conclusions and
Recommendations
Based on the results of this study.
Method 606 is a viable method for use in
water and wastewater analysis. How-
ever, the problem of interferences,
obtaining consistent blank values, and
separation of components from other
electron capture sensitive compounds
can be formidable. The accuracy and
precision statements presented earlier
apply only to the range of concentrations
studied and should not be extrapolated
beyond those limits.
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Table 1. Accuracy and Precision Equations
Dimethyl
Water tvn* phthalate
Range. /jg/L
Laboratory Pure
Accuracy »
Precision
Overall
Single analyst
Finished Drinking
Accuracy
Precision
Overall
Single analyst
Surface
Accuracy
Precision
Overall
Single analyst
Ind. Effluent 1
Accuracy
Precision
Overall
Single analyst
Ind. Effluent 2
Accuracy
Precision
Overall
Single Analyst
1.75-26.9
X = O.73c + 0.17
S = 0.44X + 0.31
SR = 0.26X + 0. 14
X = O.SSc - 0.08
S = 0.44X + 0. 18
SR = 0.30X + 0.30
X = 0.72c + 0.44
S = 0.38X + 0.24
SR = 0.35X - 0.03
X =0.66c + 0.30
S = 0.41X + 0.03
SR = 0.28X + 0.07
X =0.73c-0.23
S = 0.31 X + 0.29
SR = 0.27X + 0. 14
Diethyl
phthalate
1.70-27.4
X = 0.70c + 0.13
S = O.45X + 0.1 1
SR = 0.27X + 0.05
X = 0.72c + 0.29
S = 0.40X + 0.06
SR = 0.28X + 0.05
X = 0.77~c + 0.23
S = 0.42X + 0.46
SR = 0.26X + 0. 15
X = 0.86C + 0.36
S = 0.56X + 0.35
SR = 0.39 X - 0.09
X =0.77c-0.12
S = 0.48X + 0.28
SR = 0.31X + 0.07
i
~>i-n-butyl
ihthalate
2.48-34.9
x --
S -
SR =
X =
S =
SR =
X =
S =
SR-
X =
S =
S/? =
X -
S =
SR =
0.79C + 0.17
0.29X + 0.06
0.23X + 0.20
0.75C + 0.35
0.28X + 0.20
0.20X + 0.36
0.7SC + 0.40
0.31 X + 0.31
0.31X - 0.06
0.74C + 0.35
0.32X + 0.24
0.35X - 0.31
0.84c + 0.07
0.32X + O.55
0. J8X + 1. 10
Benzyl butyl
phthalate
0.70-12.2
X =0.82c + O.J3
S = O.25X + O.O7
SR = O.26X + 0.04
X = 0.92c + 0.07
. S =0.37X-0.01
SR = 0.32X - 0.03
X = 0.93c + 0.21
S = 0.30X + 0.07
SR = 0.32X - 0. 10
X =0.79c + 0.07
S = 0.34X^0.08
SR = 0.25X + 0. 12
X = O.SSc + 0.12
S = 0.23X + 0. 17
SR = 0.26X - 0.06
bis-2-Ethylhexyl
phthalate
5.07-55.6
X =0.53c + 2.02
S =0.73X-O.17
SR = O£OX - 2.54
X =0.74c+1.72
S = 0.48X + 0.97
SR = 0.36X + 0.46
X = O.SOc + 7. 12
S = 0.24X + 5.94
SR = -0.01 X + 9.71
X =0.68c + 3.32
S =0.41X^4.42
SR = 0. 15X + 6.94
X = 0.81 c + 2.73
S =0.64X-0.65
SR = 0.24X + 6.04
Di-n-octyl
phthalate
8.49-52. 1
X =0.35c-0.71
S =O.62X + O.34
SR = O.38X + 0.7J
X =0.76c + 0.65
S = O.43X + 7.45
SR = 0.20X + 5.44
X =0.69c-0.48
S =0.40X-0.11
SR = 0.26X - 0.64
X =0.64c-O.31
S = 0.44X - 0.53
SR = 0.29X - 0.48
X =0.66c-1.41
S = 0.36X + O.SO
SR = O.25X + 0.47
Ind. Effluent 3
Accuracy X = 0.69c + 0,22 X =0.87c-0.25 X -
Precision
Overall S = 0.44X + 0.45 S = 0.66X^0.03 S =
Single analyst SR = 0.26X + O.59 SR = 0.49X - 0.30 SR =
e - actual concentration
John D. Millar, Richard E. Thomas, and Herbert J. Sch
Southwest Research Institute, San Antonio, TX 78284.
Ft. L Graves and E. L. Berg are the EPA Project Officers (set
The complete report, entitled "EPA Method Study 16, Met!
Esters," (Order No. PB 84-21 1 275; Cost: $11.50. subjec
available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA22161
Telephone: 703-487-4650
The EPA Project Officers can be contacted at:
Environmental Monitoring and Support Laboratory
U.S. Environmental Protection Agency
Cincinnati. OH 45268
0.78C + 0.10 X =0.83c + 0.10 X = 0.47c+ 11.52 X =0.60c-/,66
0.34X^0.27 S =0.28X+0.06 S = -0.12X + 17.61 S = 0.37X + 1 .02
0.28X-0.13 SR = 0.27X SR = -0.23X + 17.79 SR = O.21X + 2.69
ittenberg are with
below).
tod 606— Phthalate
r to change) will be
U.S. GOVERNMENT PRINTING
OFFICE; 1984 — 759-015/7766
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