United States
Environmental Protection
Agency
Environmental Monitoring and
Support Laboratory
Cincinnati OH 45268
Research and Development
EPA-600/S4-84-054 July 1984
&ERA Project Summary
EPA Method Study 29,
Method 624 — Purgeables
The work which is described in the
report was performed for the purpose of
validating, through an interlaboratory
study, proposed Method 624 for the
analysis of the volatile organic priority
pollutants. This method is based on
purging and concentration of the
various analytes on an adsorbent
followed by thermal desorption onto a
gas chromatographic column. A low
resolution mass spectrometer serves as
the measuring device.
Participating laboratories were se-
lected based upon technical evaluation
of proposals and upon the analytical
results of prestudy samples. The labora-
tories were supplied with ampuls
containing various concentrations of
the pollutant compounds. These solu-
tions were aliquoted into four different
water types which were subsequently
analyzed according to the appropriate
methods. In addition to the sample
concentrates, each laboratory was
supplied with an industrial effluent
which was known to contain various
pollutants. The purpose of this sample
was to ascertain the propensity of the
method of produce false positives and
false negatives.
The data obtained from the interlab-
oratory study were analyzed employing
a series of computer programs known
as the Interlaboratory Method Validation
Study (IMVS) system which was de-
signed to implement ASTM procedure
O2777. The IMVS analyses included
tests for the rejection of outliers (both
laboratory and individual), 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 report was submitted in partial
fulfillment of contract number 68-03-
3102 by Radian Corporation under the
sponsorship of the U.S. Environmental
Protection Agency. The report covers a
period from January, 1982 to June,
1983.
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
(USEPA) gather water quality data to
provide information on water resources,
to assist research activities, and to
evaluate pollution abatement activities.
The success of these pollution control
activities depends upon the reliability of
the data provided by the laboratories,
particularly when legal action is involved.
The Environmental Monitoring and
Support Laboratory — Cincinnati (EMSL-
Cincinnati), of the USEPA develops
analytical methods and conducts quality
assurance programs for the water labora-
tories. The quality assurance program of
EMSL is designed to maximize the
reliability and legal defensibility of all
water quality information collected by
USEPA laboratories. The responsibility
for these activities of EMSL-Cincinnati is
assigned to the Quality Assurance
Branch (QAB). One of these activities is to
conduct interlaboratory tests of the
methods. This study reports the results of
the validation effort on Method 624 for
the volatile organic compounds.
The interlaboratory study of USEPA
Method 624 consisted of three distinct
phases. Phase I involved the preparation
and ampuling of concentrates of the
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compounds. The prepared concentrations
were then verified using GC methods.
The second phase involved the selection
of participating laboratories. Solicitations
were made for both paid participants and
volunteer participants. Selection of
laboratories was based on experience,
facilities, quality control procedures, and
cost estimates received from laboratories.
Final selection of fifteen laboratories was
made after the successful analysis of a
performance sample. No laboratories
chose to participate in the study as
volunteers.
The third phase involved the conduct of
the study. The prepared ampuls were
distributed to each laboratory. Each
laboratory supplied the required four
water types into which the ampuls were
spiked. In addition, a single water sample
was supplied by Radian to evaluate the
method's tendencies for false positives
and false negatives. After analysis,
results were reported on standard data
sheets. Data were keypunched and
validated by Radian. The final step in the
study was to conduct an analysis of all
data obtained using USEPA's IMVS
computer programs.
Procedure
The design of the interlaboratory study
of Method 624 was based on the
technique described by W.J. Youden (1).
According to this technique, samples are
analyzed in pairs where the concentration
of each analyte in the sample pairs is
slightly different. The analyst is directed
to perform a single analysis and report
one value for each sample.
The samples were prepared as concen-
trates in sealed ampuls and shipped to
the participating laboratories. Each
laboratory was responsible for supplying
laboratory pure water, finished drinking
water, a surface water, and an industrial
effluent water for use in the study (two
laboratories, numbers 10 and 16 used
water treatment plant effluents which
may have had primarily municipal origins).
The analyst was required to add an
aliquot of each concentrate to a value of
water from each of the four water types
and subsequently to analyze the spiked
water samples.
Sample pairs for each method were
prepared at three concentration levels;
low, medium, and high, all of which were
within the linear range of the mass
spectrometer.
In addition to the sample ampuls, an
industrial effluent water selected by
Radian was furnished to each participating
laboratory for analysis. This sample was
known to contain a number of the priority
pollutants and was judged to be some-
what difficult to analyze. The purpose of
the industrial effluent sample was to
determine the propensity of the method
to produce false positives and false
negatives.
After all analyses were completed, the
results were subjected to statistical
analysis using USEPA's IMVS system to
determine the precision and accuracy of
Method 624.
Test Design
The following is a summary of the test
design used based on Youden's nonrep-
licate technique for samples.
1. Three Youden pairs of samples
were analyzed for each analyte
with the deviation from the mean of
each pair being at least 5% but not
more than 20%. The three pairs
were spread over a usable and
realistic range such that the lowest
pair was somewhat above the
minimum detection limit and the
upper pair was within the linear
range of the method.
2. The spiking samples were supplied
as liquid concentrates in organic
solvents sealed in glass ampuls.
Sufficient sample was provided to
allow withdrawal of the appropriate
amount of solution to spike one
water sample from each ampul.
3. Twenty-four volatile organic ampuls
were provided to each of the 15
laboratories.
4. The concentrates were spiked into
laboratory pure water, drinking
water, a surface water, and an
effluent waste water by the partici-
pants prior to analysis. In addition,
an industrial effluent sample was
supplied to each .laboratory by
Radian. This sample was analyzed
without addition of analyte con-
centrates.
5. Each of the 15 participating labora-
tories was furnished with the
following materials:
• Four Youden pair ampuls of
each of three concentration
levels for the volatile organics.
(A total of 24 spiking sample
ampuls.)
• Sufficient surrogate standard
solution to analyze all samples
and blanks.
• A1 liter sample of an industrial
effluent to be analyzed without
addition of spiking sample.
• Copies of Method 624.
• A questionnaire covering dif-
ficulties encountered with the
method and suggestions for m
improvements.
• Data report forms to be com-
pleted and returned to Radian.
• A set of instructions detailing
the method for spiking the
samples and the order in
which samples were to be run.
Results and Discussion
Method 624 is acceptable for the
analysis of purgeable priority pollutants.
The accuracy of the method is judged very
good while overall precision and single-
analyst precision are considered accept-
able. For most compounds, matrix does
not significantly affect the analysis.
Method 624 was characterized in terms
of accuracy, overall precision, single-
analyst precision, and the effect of water
type on accuracy and precision through
statistical analyses of 9,880 reported
values. Estimates of accuracy and
precision were made and expressed as
regression equations, shown in Table 1
for each compound. The equations were
based on the 8,446 data values remaining
after eliminating 1,434 values (approxi-
mately 15%) designated as outliers by the •
IMVS programs. The development and
interpretation of these regression equa-
tions are discussed in Section 5. To
facilitate the interpretation of these
equations. Table 2 was prepared. In Table
2, accuracy (percent recovery), overall
precision (percent standard deviation),
and single-analyst precision (percent
standard deviation) were computed
(using the regression equations) at a
concentration of 100 fjg/L.
Accuracy is obtained by comparing
the mean recovery to the prepared values
of the concentrations and computing the
percent recovery. Overall, recoveries for
the volatile organic compounds are very
good for all of the water matrices with an
average recovery of 100%. The mean
recovery statistics (at 100 /ug/L) for the
volatile organic compounds range from
68% fo'r bromomethane in the surface
water matrix to 123% for cis-1,3-
dichloropropene in the distilled water.
One-half of the mean recoveries are
between 94% and 105%, with one-fourth
of the mean recoveries above and below
these values. Recoveries for bromometh-
ane are consistently low (ranging from
68% to 75%) for all water matrices. Mean
recoveries for cis-1,3-dichloropropene
and 1,2-dichloropropane are high with
recoveries ranging from 116% to 123%,
while the recovery of trans 1,3-dichloro-
propene is uniformly low, averaging 83%.
It is known that the isomers of 1,3-
dichloropropene are relatively unstable
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Tablt 1 . Regression Equations for Accuracy and Precision
Water Type Benzene Bromodichloromethane
Applicable Cone. Range
Distilled Water
Single-Analyst Precision
Overall Precision
Accuracy
Tap Water
Single-Analyst Precision
Overall Precision
Accuracy
Surface Water
Single-Analyst Precision
Overall Precision
Accuracy
Industrial Effluent
Single-Analyst Precision
Overall Precision
Accuracy
(10.8 - 480.01
SR = 0.26X- 1.74
S =0.25X- 1.33
X = 0.930 + 2.00
SR = 0.20X - 0.24
S =0.22X-0,75
X = 0.9SC + 1.40
SR = 0.15X-0.60
S =0.23X- 1.02
X = 0.94C + 1.88
SR = 0. 14X - 0.91
S = 0.22X-0.86
X = O.S9C + 1.60
(8.0 - 480.0)
SR = 0.1 5X + 0.59
5 = 0.20X + 1. 13
X = 1.03C - 1.58
SR = 0.17X + 0.94
S = 0.20X + 3.76
X - 1.03C + 1.35
SR = 0. 18X + 0.43
S = 0.22X + 0.80
X = 1.00C - 1.02
SR = 0.23X-0.15
S = O.22X+1.01
X =0.940-0.93
Bromoform*
(9.0 - 400.0)
SR = 0.14X + 0.19
S = 0.20X + /. 18
X = 1.01C - 0.89
SR = 0.31 X + 1.36
S = 0.33X + 1.03
X =1. 13C - 1.07
SR = 0. 18X + 0.06
5 = 0.26X + 0.98
X =0.57C-0.67
SH = 0.28X - 0.02
5 = O.33 + 0.49
X = 0.95C - 1.65
Bromomethane
(9. 1 - 6O7.O)
SR = 0.27X - 0.50
S = 0.25X + 0.64
X =0.720-0.79
SR=0.29X -0.45
S = 0.34X + 0.57
X =0.690 - 1.14
SR=0.24X -0.15
S = 0.25X + 0.67
X =0.690-0.51
SR=0.37X -0.21
S = 0.41 X- 0.07
X =0.760-0.80
X = Mean Recovery
C = True Value for the Concentration
'Revised regression equations and estimates of accuracy and precision are given in Table 2
Water Type
Applicable Cone. Range
Distilled Water
Single-Analyst Precision
Overall Precision
Accuracy
Tap Water
Single-Analyst Precision
Overall Precision
Accuracy
Surface Water
Single-Analyst Precision
Overall Precision
Accuracy
Industrial Effluent
Single-Analyst Precision
Overall Precision
Accuracy
Carbon Tetrachloride*
(9.0 - 400.0)
SR = 0.11X^0.35
S = 0.14X + 0.17
X = 1.01C - 0.84
SR = 0.23X - 0.85
S = 0.24X - 0.87
X = 1.070 - 1.66
SR = 0. 16X + 0.98
S =0.19X^0.95
X = 1.010 - 0.22
SR = 0.20X - 0.29
S =0.20X^0.54
X =0.950-0.62
Chlorobenzane
(13.5 - 600.0;
Sfl = 0.;6X-0.09
S =0.26X-1.92
X =0.980 + 2.28
SR = 0.1 9X + 0.69
S = 0.22X - 0.30
X = 1.020 + 2.04
SR = 0.19X-0.81
S =0.29X-2.60
X =1.010 + 2.91
SR = 0.23X + 0. 13
S = 0.36X - 2.20
X =0.920 + 2.36
Chloroethane*
(7.3 - 488.0)
SR = 0.23X + 2.02
S =0.27X+1.95
X = 1.080 + 1.50
SR = 0.31 X- 0.71
S = 0.35X + 0.04
X =1.100 + 0.13
SR = 0.22X+ 1.63
S =0.28X+1.47
X = 1.090 + 1.83
SR = 0.32X + 0.25
S =0.38X-0.21
X =1. 120 + 0.44
Chloroform
(4.5 - 300.0)
SR=0.16X + 0.22
s =0. isx + o. re
X =0.930 + 0.33
SR = 0.23X + 0.42
S = 0.31 X + 5.58
X =0.870 + 5.78
SR = O.22X - 0.30
S =O.23X-0.08
X =0.910 + 0.65
SR=0.14X + 0.33
S =0.18X + 0.65
X =0.940 + 0.37
X = Mean Recovery
C = True Value for the Concentration
"Revised regression equations and estimates of accuracy and precision are given in Table 2.
Water Type
Chloromethane*
CIS-1,3,-Dichloropropene
Dibromochloromethane
Ethyl Benzene
Applicable Cone. Range
Distilled Water
Single-Analyst Precision
Overall Precision
Accuracy
Tap Water
Single-Analyst Precision
Overall Precision
Accuracy
Surface Water
Single-Analyst Precision
Overall Precision
Accuracy
Industrial Effluent
Single-Analyst Precision
Overall Precision
Accuracy
(7.O - 469.0)
SR = 0.41X+ 1.75
S =0.48X+1.21
X =0.940 + 2.37
SR = 0.43X + 0.09
S = 0.45X - 0.21
X =O.O9C + O.20
SR = 0.37X - 0.46
S =0.45X + 0.55
X =1.120 - 0.56
SR = 0.59X - 1.33
S =0.61X- 1.10
X = 1.020 - 0.38
(8.0 - 357.0)
SR = 0.19X +0.44
S = 0.24X + 0.07
X = 1.240 - 0.55
SR = 0.21 X +0.38
S = 0.27X + 0.55
X = 1.210 - 0.47
SR = 0.26X - 0.90
S =0.32X-0.33
X =1.160 + 0.18
SR = 0.15X +0.33
S =0.25X + 0.01
X = 1.20C - 0.44
(8.1 - 360.0)
SR = 0.17X-0.18
S =0.17X + 0.49
X =1.010-0.03
SR = 0.23X - 0.24
S = 0.26X + 0.88
X = 1.070 - 0.44
SR = 0.20X -0.39
S = 0.21 X - 0.18
X =1,010 + 0.10
SR = O.I8X-0.38
S = 0.26X - 0.87
X = 1.070 - 0.70
(15.O - 68O.O)
SR = 0.14X + 1.00
S =O.26X- 1.72
X = 0.98C + 2.48
SR = 0.22X + 0.90
S =O.24X-0.77
X =0.990 + 2.97
SR = 0.15X + 0.38
S =0.22X-1.25
X = 1.010 + 3.88
SR=0.24X + 0.03
S =0.29X- 1.27
X =1.010 + 3.73
X = Mean Recovery
C = True Value for the Concentration
^Revised regression equations and estimates of accuracy and precision are given in Table 2
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Table 1 (continued)
Water Type
Methylene Chloride'"
Tetrach/oroethene
Toluene
Trans- 1 ,2-Dichloroethene*
Applicable Cone. Range
Distilled Water
Single-Analyst Precision
Overall Precision
Accuracy
Tap Water
Single-Analyst Precision
Overall Precision
Accuracy
Surface Water
Single-Analyst Precision
Overall Precision
Accuracy
Industrial Effluent
Single-Analyst Precision
Overall Precision
Accuracy
(7.2 - 480.0)
SR = 0.19X+0.76
S =0.30X+4.09
X =0.810 + 2.31
SR = 0.26X+ 5.78
S =0.36X+5.37
X =0.730 + 5.97
SR = 0.16X+9.45
S =0.25X+7.91
X = 0.800 + 8.57
SR = 0.30X + 3.54
S =0.44X+ 1.94
X =0.710+3.15
(9.0 - 400.0)
SR = 0,13X -0.18
S = 0.16X-0.45
X = 1.060 + 0.60
SR = 0.23X + 0.04
S = 0.27X-0.64
X =0.980 + 0.71
SR = 0.18X -0.22
S = 0.25X - 1.16
X = 1.020 + 1.54
SR = 0.27X + 0.54
S = 0.31X - 0.15
X =0.870+1.62
(13.5 - 600.O)
SR = 0.15X- 0.71
S =0.22X- 1.71
X = 0.980 + 2.03
SR = 0.18 + 0.71
S =0.24X-0.66
X =0.980 + 2.76
SR = 0.15X - 0.03
S =0.23X- 1.67
X = 1.000 + 2.25
SR = 0.22X - 0.93
S =026X- 1.07
X =0.920 + 2.63
(4.5 - 300.0)
SR = 0.16X + 0.03
S =0.19X + 0.13
X =0.980 + 0.30
SR = 0.17X +0.20
S =0.17X + 0.52
X =1.050-0.17
SR = 0.16X + 0.10
S =0.16X + 0.37
X =0.980 + 0.26
SR =0.21 X -0.09
S =0.23X + 0.07
X =0.960 + 002
X = Mean Recovery
C = True Value for the Concentration
"Revised regression equations and estimates of accuracy and precision are given in Table 2
Water Type
Applicable Cone. Range
Distilled Water
Single-Analyst Precision
Overall Precision
Accuracy
Tap Water
Single-Analyst Precision
Overall Precision
Accuracy
Surface Water
Single-Analyst Precision
Overall Precision
Accuracy
Industrial Effluent
Single-Analyst Precision
Overall Precision
Accuracy
Trans-1,3-Dichloropropene
(9.4 -416.0)
SR = 0.20X - 0.53
S = 0.26X - 0.09
X = 0.800 + 0.22
SR = 0, 13X + 0.94
S = 0.25X + 0.23
X = 0.830 - 0.58
SR = 0. 15X + 0.03
S =0.24X + 0.18
X =0.890 + 0.69
SR = 0.18X -O.37
S =0.22X-0.48
X = 0.820 - 0.08
Trichloroethene
(5.4 - 360.0)
SR = 0.1 3X + 0.36
S = 0.1 2X + 0.59
X = 1.040 + 2.27
SR = 0.23X - 0.34
S =026X-0.28
X = 1.030 + 1.65
SR = 0. 14X + 1.05
S = 0.1 9X-+ 0.94
X = 1.030 + 2.91
SR = 0.22X + 0.75
S = 0.33X - 0.03
X =0.990 + 1.76
Trichlorofluoromethane"
(7.2 - 480.0)
SR = 0.31X- 1.34
S = 0.36X - 0.48
X = 0.920 + 0.83
SR = 0.18X + 0.66
S =0.31X-015
X = 0.980 + 0.34
SR = 0.28X - 0.30
S = 0.31 X + 0.02
X =0.850 + 0.70
SR = 0.24X - 1.36
S =0.28X-0.56
X = 1.OOC + 0.25
1. 1 -Dich/oroethane"
(10.8 - 480.0)
SR = 0. 15X - 0.22
S =0. 15X + 0.53
X =0.980 + 1.09
SR =0.16X -0.21
S =0.14X + 0.82
X =1.010 + 0.11
SR= 0.1 IX +1.07
S =0.12X+1.06
X =0.990+1.13
SR = 0.23X - 0.27
S = 0.24X + 0.84
X = 1.040 + 0.39
X = Mean Recovery
C = True Value for the Concentration
"Revised regression equations and estimates of accuracy and precision are given in Table 2
Water Type
Applicable Cone. Range
Distilled Water
Single-Analyst Precision
Overall Precision
Accuracy
Tap Water
Single-Analyst Precision
Overall Precision
Accuracy
Surface Water
Single-Analyst Precision
Overall Precision
Accuracy
Industrial Effluent
Single-Analyst Precision
Overall Precision
A ccuracy
1, 1 -Dichloroethene"
(7.2 - 480.0)
SR = 0.22X + 0.58
S = 0.37X + O.24
X = 1.010 + 1.43
SR = 0.16X+ 1.73
S =0.23X + 0.60
X = 0,940 + 2.07
SR = 0. 14X + 0.95
S - 0.21 X + 0.69
X =0.950 + 1.38
SR = 0.23X - 0.35
S = 0.23X + O.24
X =0.840+1.57
1, 1, 1 -Trichloroethane
(9.0-4000)
SR = 0. 12X - 0. 15
S = 0.21 X- 0.39
X =1.060 + 0.73
SR = 0.20X - 0.54
S =0.23X-0.22
X =1.110-0.53
SR = 0.23X - 0.27
S =0.28X-0.82
X =1.010 + 0.31
SR = 0. 18X - 0.81
S = 0.24X - 0.55
X =0.990 + 0.83
1, 1 ,2-Trichloroethane
(10.8 - 480.0)
SR = 0. 14X + O.02
S =0.18X + O.OO
X =0.950+1.71
SR = 0,12X+ 1.44
S = 0.15X + 0.74
X = 1.020 + 1.80
SR = 0.1 6X -0.27
S = 0.21 X - 0.84
X = 1.040 + 1.55
SR = 0.18X + O.05
S = 0.23X - 1.06
X = 1 000 + 1.04
1. 1,2.2-Tetrachloroethane
(15.O - 680.0)
SR=0.16X + 0.69
S =0.20X + 0.41
X =0.930+1.76
SR = 0. 16X + 0.30
S =0.25X-0.83
X = 0.920 + 0.94
SR = 0 14X+ 1.08
S = 0.20X + 1.53
X = 0.990 + 1.45
SR = 0.37X - 1.22
S =030X + 0.91
X =0.870+2.09
X = Mean Recovery
C = True Value for the Concentration
"Revised regression equations and estimates of accuracy and precision are given in Table 2
4
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Tahiti, (Continued/
Water Type 1,2-Dichlorobenzene/1,4-D 1,2-Dichloroethane
Applicable Cone. Range (16.O - 780.O)
Distilled Water
Single-Analyst Precision SR = 0.22X - 1.45
Overall Precision S -0.3OX-1.20
Accuracy X = 0.94C + 4.47
Tap Water
Single-Analyst Precision SR = 0.36X - 2.57
Overall Precision S -0.38X-1.56
Accuracy X = 0.98C+4.65
Surface Water
Single-Analyst Precision SR - 0.25X + 0.85
Overall Precision S = 0.30X + 1.48
Accuracy X = 0.97C + 6.92
Industrial Effluent
Single-Analyst Precision SR = Q.25X + 2.55
Overall Precision S = 0.29X + 4.32
Accuracy X =0.95C + 5.14
X = Mean Recovery
C = True Value for the Concentration
Table 2. Revised Regression Equations
Water Type
Applicable Cone. Range lug/L)
Distilled
Single-Analyst Precision
Overall Precision
Accuracy
Tap Water
Single-Analyst Precision
Overall Precision
Accuracy
Surface Water
Single-Analyst Precision
Overall Precision
Accuracy
Industrial Effluent
Single-Analyst Precision
Overall Precision
Accuracy
(9.9 - 440.0)
SR = 0.17X -0.32
S = 0.21X-0.38
X = 1.02C + 0.45
SR = 0.18X-0.21
S = 0.17X^0.14
X = 1.06C • 0.45
SR = 0. 15X + 1.01
S = 0.18X+1.69
X =1. 01C + 0.97
SR = 0. 14X + O.96
S = 0.18X+1.44
X = 1.01C • 0.28
lor Accuracy and Precision
Bromoform
(9.0 - 400)
SR = 0. 12X + 0.36
S = 0.17X+1.38
X =1. 18C - 2.35
SR = 0.23X + 2.06
S = 0.33X+1.01
X =1.320-2.74
SR = 0.1 4X + 0.38
S = 0.24X + 1.08
X = 1.10C- 1.80
SR = 0.18X + 0,65
S = 0.25X + 1.02
X = 1.06C - 2.67
1 ,2-Dichloropropane
(13.5 - 600.0>
SR = 0. 14X - 0.85
S = 0.17X-0.41
X = 1. 18C + 2.00
SR=0.10X + 0.95
S = 0. 13X + 0.53
X =1.16C+1.70
SR = 0.13X-0.52
S = 0.17X-O.33
X =1.18C + 2.89
SR = 0. 13X + 0.77
S =0. 18X + 0.53
X = 1.22C - 0.25
Carbon Tetrachloride
(9.0 - 400)
SR - 0. 12X + 0.25
S =0.1 IX + 0.37
X =1.100+1.68
SR = 0. 18X - 0.53
S =0.20X-0.61
X =1.180-2.66
SR = 0. 15X + 7.07
S =0.18X + 0.98
X =1.070-0.73
SR = 0. 19X - 0.23
S =0. 19X + 0.59
X = 1.OOC - 1.07
1. 3-Dichlorobemene
(7.2 - 480.0)
SR=0.14X-0.48
S = 0.1 8X- 0.82
X = 1.06C + 1.68
SR = 0.22X + 3.41
S = 0.24X + 2.34
X = 1.02C + 3.80
SR=0.15X + 1.44
S = 0.16X^1.72
X =1.1 1C + 1.90
SR = 0. 15X + 2.01
S = 0.17X^1.83
X =1.030 + 1.79
Chloroethane
(7.3 - 488)
SR=0.14X+2.78
S =0.29X+1.75
X =1.180 + 0.81
SR = 0.29X - 0.52
S = 0.34X + 0. 13
X =1.170-0.37
SR=O.25X+ 1.37
S = 0.28X + 1.46
X =1.120+1.63
SR = 0.32X + 0.25
S = 0.4OX - 0.37
X = 1.240 - 0.41
X = Mean Recovery
C = Prepared Concentration
Water Type
Chloromethane
Methylene Chloride
Trans-1,2-Dichloroethene
Applicable Cone. Range fag/L)
Distilled
Single-Analyst Precision
Overall Precision
Accuracy
Tap Water
Single-Analyst Precision
Overall Precision
Accuracy
Surface Water
Single-Analyst Precision
Overall Precision
Accuracy
(7.0 - 469)
SR = 0.37X + 2.14
S =0.58X + 0.43
X = 1.030 + 1.81
SR = 0.38X + 0.40
S =0.55X-0.79
X =0.960-0.20
SR = 0.32X - 0.05
S =0.49X + 0.27
X = 1.230 - 1.31
(7.2 - 480)
SR = 0.15X + 1.07
S =0.32X + 4.OO
X =0.870+1.88
SR = 0.2OX + 4.96
S =0.38X + 5.19
X =0.780 + 5.66
SR=0.27X + 8.17
S =0.29X+7.48
X = 0.830 + 8.40
(4.5 - 3OO)
SR = 0.14X + 0.09
S =0.19X + 0.17
X = 1. ISO + O.03
SR= 0.1 IX + 0.49
S =0.15X + 0.60
X =1.110-0.40
SR=0.17X
S =O.15X + 0.4O
X = 1.020 + 0.05
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Table 2, (continued)
Water Type
Chloromethane
Methylene Chloride
Trans-1,2-Dichloroethene
Industrial Effluent
Single-Analyst Precision
Overall Precision
Accuracy
SR = 0.61X- 1.43
S =0.58X-0.95
X = /. J3C - 1.23
SR = 0.30X + 3.56
S = 0.42X + 2.06
X =0.800 + 2.50
SR = 0.26X - 0.29
S = 0.19X + 0.22
X = 1.02C - 0.23
X = Mean Recovery
C = Prepared Concentration
Table 2. (continued)
Water Type
Trichlorofluoromethane
1,1 -Dichloroethane
1.1 -Dichloroethene
Applicable Cone. Range (fjg/L)
Distilled
Single-Analyst Precision
Overall Precision
Accuracy
Tap Water
Single-Analyst Precision
Overall Precision
Accuracy
Surface Water
Single-Analyst Precision
Overall Precision
Accuracy
Industrial Effluent
Single-Analyst Precision
Overall Precision
Accuracy
(7.2 - 480)
SR-0.33X- 1.48
S = 0.34X-0.39
X = 0.990 + 0.39
SR = 0.17X + O.80
S = 0.29X + O.04
X =1.050-0.19
SR = 0.33X -0.57
S = 0.31 X + 0.03
X =0.870 + 0.50
SR = 0.27X + 1.62
S =0.26X-0.43
X = 1.070 - 0.29
(10.8 - 480)
SR = 0.13X - 0.05
S = 0.16X + 0.47
X = 1.05C + 0.36
SR = 0.14X - 0.08
S =0.14X + 0.52
X = 1.070 - 0.53
SR = 0.11X + 1.08
S = 0.12X+1.12
X =1.020 + 0.76
SR = 0.23X -0.27
S = 0.21 X+ 1.12
X =1.090-0.12
(7.2 - 480)
SR=0.17X+ 1.06
S =0.43X-0.22
X = 1.120 + 0.61
SR = 0.12X + 2.08
S =0.24X + 0.53
X = 1.020 + 1.43
SR=0.16X + 0.87
S =0.24X + 0.51
X =1.010 + 0.91
SR = 0.24X - 0.39
S = 0.20X + 0.39
X = 0.930 + 0.94
X = Mean Recovery
C = Prepared Concentration
and may decompose to 1,2-dichloropro-
pane.
The overall standard deviation of the
analytical results is an indication of the
precision associated with the measure-
ment generated by a group of laboratories.
The percent relative standard deviation
(RSD) at 100 /t/g/L for the volatile organic
compounds range from 13% for trichloro-
ethene, 1,1-dichloroethane, and 1,2-
dichloropropane in the various water
matrices to 60% for Chloromethane in the
industrial effluent with a median value of
24%. Precision for Chloromethane is
relatively poor for all water matrices with
percent relative standard deviations
ranging from 45% to 60%. One-half of the
RSDs are between 20% and 29%. In 95%
of the cases the RSDs are less than 44%.
The percent relative standard deviation
for a single analyst (RSD-SA) indicates
the precision associated within a single
laboratory. The RSD-SA for samples at
100 /ug/L ranges from 11 % for carbon
tetrachloride (distilled water matrix) and
1,2-dichloropropane (tap water matrix) to
58% for Chloromethane in the industrial
effluent with a median RSD-SA of 19%.
Single-analyst precision for Chlorometh-
ane is relatively poor with RSD-SAs
ranging from 37% to 58%. One-half of the
RSD-SAs at 100 /jg/L are between 15%
and 23%. In 95% of the cases, the RSD-
SAs are less than 36%. Three compounds
used in this study, bromomethane,
Chloromethane and chloroethane, are
gases in pure form. Although there are no
clear trends for accuracy in the gaseous
species as opposed to less volatile
compounds, it is possible that the low
recovery observed for bromomethane
and the poor precision for all three
compounds may be due to inherent
difficulties in handling gaseous and
extremely volatile compounds during the
various preparation and analytical proce-
dures required in the method. Bromo-
methane is also known to be unstable,
which could also account for low recover-
ies.
The effect of water type was different
for the various volatile organic compounds.
For most compounds the water matrix
does not have a great effect on either the
accuracy or precision. Overall, recoveries
for the volatile organic compounds
averaged 100% in distilled water, 101%
in tap water and surface water, and 97%
in the industrial effluent matrix. Precision
(RSD and RSD-SA) for the volatile organic
compounds ranged from a median RSD of
21% and median RSD-SA of 16% for the
distilled water to a median RSD of 25%
and a median RSD-SA of 23% for the
industrial effluent matrix.
A trend toward higher recoveries
(above 100%) forthe lowest concentration
Youden pairs was observed for 10
compounds. One explanation could be
sample contamination from the presence
of these compounds in the laboratory.
Methylene chloride displayed the most
pronounced example with recoveries
averaging 142%, 76% and 83% for the
low, medium and high pairs respectively.
Low-level contamination may be respon-
sible for the 142% recovery of the low
pair. Blank concentrations were also
higher for methylene chloride than for
many of the other compounds, indicating
a greater likelihood of low-level sample
contamination. This explanation is less
clear for other compounds. For example,
the trend is more pronounced for the
chlorobenzenes than for benzene or
chloroform, yet the latter compounds
would be expected to be more ubiquitous
in a laboratory environment.
A review of the data remaining after the
IMVS outlier screening indicated some
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potential problems with the data for nine
of the volatile organic compounds. For
these compounds, results for ampul four
were out-of-line (usually due to extremely
low recoveries) with the remaining data.
It is suspected that during production of
ampul concentrate four, these volatile
compounds were lost. The data for these
medium level ampuls were eliminated,
and the equations revised. Table 2
presents the revised equations.
Four compounds in addition to those
listed in Table 2 had questionable
regression equations although the equa-
tions were not revised. These were
bromomethane, cis and trans 1,3-
dichloropropene and 1,2-dichloropropane.
Bromomethane exhibited poor recoveries
which may have been due to its extreme
volatility or to its reactivity. The dichloro-
propenes are known to be unstable and to
form dichloropropane upon decomposi-
tion. Problems with these compounds
were also encountered with USEPA
Quality Control Samples and in the
Interlaboratory Study for Method 601 —
Halogenated Purgeables by GC.
This Project Summary was authored by staff of Radian Corporation, P. 0. Box
9948. Austin. JX 78766
Raymond Wesselman and Bob Graves are the EPA Project Officers (see below).
The complete report, entitled "EPA Method Study 29, Method 624—Purgeables,"
(Order No. PB 84-209 915; Cost: $20.50, subject to change) will be 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
*USGPO: 1984-759-102-10632
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United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
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