United States
                     Environmental Protect
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-
                       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).

                    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

  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-
  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
  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
  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.

Table 1. Accuracy and Precision Equations
Water tvn* phthalate
Range. /jg/L
Laboratory Pure
Accuracy »
Single analyst
Finished Drinking
Single analyst
Single analyst
Ind. Effluent 1
Single analyst
Ind. Effluent 2
Single Analyst

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

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

x --

S -
SR =

X =

S =
SR =

X =

S =

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

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

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
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 -
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
tod 606— Phthalate
r to change) will be

                         OFFICE; 1984 — 759-015/7766

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