United States
Environmental Protection
Agency
Environmental Monitoring Systems
Laboratory
Research Triangle Park NC 27711
Research and Development
EPA/600/S4-85/064 Jan. 1986
Project Summary
Stability of Organic Audit
Materials and Results of Source
Test Analysis Audits—Status
Report #7
J. Sokash, G. B. Howe, R. K. M. Jayanty, C. E. Decker, and D. J. von Lehmden
A repository of 45 gaseous com-
pounds including hydrocarbon, halo-
carbon, and sulfur species has been
established under contract with the U.S.
Environmental Protection Agency
(EPA). The primary objectives of this
on-going project are (1 j to provide gas
mixtures to EPA, state/local agencies.
or their contractors for use in perform-
ance audits to assess the accuracy of
source emission measurements in cer-
tain organic chemical manufacturing
industries, (2) to examine the vendor's
certified analysis of the gas mixtures by
in-house analysis, (3) to determine the
stability of the gas mixtures with time
by in-house analysis, «md (4) to develop
new audit materials as requested by
EPA.
To date, 21 compounds have been
used to conduct 149 different audits.
The results of these audits and a des-
cription of the experimental procedures
used for analyses and available stability
data are presented in this status report.
Generally, the results of the audits show
close agreement (plus or minus fifteen
percent) with the audit material con-
centrations measured by Research Tri-
angle Institute.
Compound stabilities have been de-
termined through multiple analyses of
the cylinders containing them. Of the
45 gaseous compounds studied or
currently under study, 39 have demon-
strated sufficient stability in cylinders
to be used further as audit materials.
This Project Summary was developed
by EPA's Environmental Monitoring
Systems Laboratory, Research Triangle
Park, NC, to announce key findings of
the research project that is fully docu-
mented in a separate report of the same
title (see Project Report ordering infor-
mation at back).
Introduction
Accurate measurement of hydrocar-
bons, halocarbons, and sulfur-containing
compounds in ambient and source sam-
ples is essential to any environmental
monitoring program. The potential for
achieving acceptable accuracy is en-
hanced by the availability of reliable
standards that can be used to check or
validate the measurement process. The
Research Triangle Institute (RTI) under
contract to the Environmental Monitoring
Systems Laboratory, U.S. Environmental
Protection Agency (EPA), has responded
to this need by developing an extensive
repository of gaseous compounds. These
gaseous compounds are to be used in
performance audits as designated by the
EPA Project Officer. These performance
audits are to assess the accuracy of
source emission measurements in cer-
tain organic manufacturing industries.
Currently 45 different compounds have
been investigated as audit materials. Six
of these gaseous compounds have been
found to be unstable in cylinders and not
suitable as audit materials. The other 39
gaseous compounds in the repository are
suitable for conducting performance au-
dits during source testing. Table 1 lists
the 45 compounds, the concentration
-------
Table 1 . Audit Materials Currently in the Repository
Low Concentration Range
Compound
Benzene
Ethylene
Propylene
Methane/Ethane
Propane
Toluene
Hydrogen Sulfide
Meta-Xylene
Methyl Acetate
Chloroform
Carbonyl Sulfide
Methyl Mercaptan
Hexane
1 ,2-Dichloroethane
Cyclohexane
Methyl Ethyl Ketone
Methanol
1 ,2-Dichloropropane
Trichloroethylene
1, 1 -Dichloroethylene
1,2-Dibromoethylene"*
Perchloroethylene
Vinyl Chloride
1 ,3-Butadiene
Aery Ion it rile
Aniline**
Methyl Isobutyl Ketone
Para-dichlorobenzene * *
Ethylamine**
Formaldehyde**
Methylene Chloride
Carbon Tetrachloride
Freon 113
Methyl Chloroform
Ethylene Oxide
Propylene Oxide
Ally/ Chloride
Acrolein
Ch/orobenzene
Carbon Disulfide
Cyclohexanone**
EPA Method 25 Gas***
Ethylene Dibromide
Tetrachloroethane
No. of
Cylinders
7
4
3
-
4
5
7
1
2
2
1
3
2
4
-
1
2
2
2
2
-
2
9
1
1
--
7
--
--
--
3
7
7
7
5
7
7
7
3
--
-
6
2
1
Concentration
Range (ppm)
5
5
5
5
5
5
5
5
5
5
3
20
5
30
30
5
5
5
5
5
5
5
5
1
5
5
5
5
5
5
5
5
100
5
5
- 20
- 20
- 20
--
- 20
- 20
- 50
• 20
- 20
- 20
- 20
- 10
- 80
- 20
-
- 80
- 80
- 20
- 20
- 20
--
- 20
- 30
- 30
- 20
--
- 20
—
--
--
- 20
- 20
- 20
- 20
- 20
- 20
- 20
- 20
- 20
--
-
- 200
- 20
- 20
Cylinder
Construction*
S
Al
Al
-
Al
S
Al
S
S
S
S
Al
Al
Al
-
S
Al
Al
Al
Al
-
S
S
S
Al
--
Al
S
Al
-
Al
Al
Al
Al
Al
Al
S
Al
Al
Al
Al
Al
S
S
No. of
Cylinders
11
4
6
3
4
4
4
4
7
2
2
1
3
--
/
4
1
-
-
2
2
2
-
2
-
--
1
--
--
--
--
-
--
--
--
--
--
7
7
--
-
7
--
3
2
--
High Concentration Range
Concentration Cylinder
Range (ppm) Construction*
60
300
3000
300
WOO
200
300
1000
100
100
300
300
300
WO
WOO
WO
80
300
WO
WO
300
300
75
75
75
750
100
- 400
• 700
- 20,000
- 700
- 6000(M).
- 700 (E)
- 700
- 20,000
- 700
- 700
- 700
- 700
- 700
- 300
--
- 3000
- 600
- 200
--
--
- 700
- 600
- 600
--
- 700
-
--
- 500
--
--
--
--
--
--
-
--
--
--
- 200
- 200
--
--
- 200
--
- 2000
- 300
-'
S
Al
Al
Al
Al
Al
Al
LS
Al
LS
S
S
S
--
LS
Al
S
-
—
Al
Al
Al
-
LS
--
--
Al
--
-
-
--
-
-
-
-
-
-
Al
S
-
--
Al
-
Al
S
~~
'Cylinder construction: Al = Aluminum, S - Steel, LS = Low Pressure Steel.
**Cylinders are no longer available; the compounds were found to be unstable in the cylinders.
***The gas mixture contains an aliphatic hydrocarbon, an aromatic hydrocarbon, andcarbon dioxide in nitrogen. Concentrations shown are reported in
ppmC.
-------
ranges for each compound, the number of
cylinders of each compound, and the
cylinder construction material. Additional
compounds are procured, as needed.
The gaseous compounds are acquired
from commercial suppliers in compressed
gas cylinders; these same cylinders, along
with an appropriate delivery system, are
used directly as sources of the gaseous
compounds during performance audits.
The compressed gas cylinder is especially
suitable as an audit device because of its
simplicity, portability, low cost, flexibility
in analyte delivery over a broad concentra-
tion range, reliability, and ruggedness for
interstate shipping. The accuracy of the
supplier-reported levels of these com-
pounds are verified through measure-
ment using National Bureau of Standards-
Standard Reference Materials (NBS-
SRMs), commercial permeation tubes,
and/or reagent grade pure liquids as
standards. The permeation rates of the
commercially available tubes are verified
by RTI before use.
The accuracy of the "known" cylinder
concentrations and the stability of the
compounds inthecylindersare important.
Along with acquisition of new compounds
and verification of their concentrations,
an extensive stability study is being
performed. This study involves periodic
analyses of the contents of each of the
cylinders in the repository.
Procedure
Once a compound is chosen, a com-
mercial supplier is contacted to determine
if a cylinder containing that compound
can be prepared. If so, the manufacturer
prepares the cylinder gases and deter-
mines the concentration of the analyte in
the cylinder. The cylinder is sent to RTI
where its contents are analyzed usually
within seven days of its arrival. If the RTI
value varies from the manufacturer's
value by more than 10 percent, an
analysis is performed by a third party
(EPA or NBS). The cylinder contents are
then analyzed one month after acquisi-
tion. The cylinder contents are then
analyzed one month after acquisition,
two months after acquisition, and one
year after acquisition. The cylinder con-
tents are also analyzed usually before a
cylinder is sent out for an audit. This
preaudit analysis may substitute for the
annual analysis if it occurs within a month
of the normal analysis due date.
All analyses are carried out using gas
chromatography (GC). The column and
detector are chosen so as to be optimum
forthe compound being measured. Three
types of standards are used to generate
gas concentrations for calibration of the
GC for the measurement of audit mater-
ials. National Bureau of Standards-
Standard Reference Materials (NBS-
SRMs) of methane and propane are used
as standards for the measurement of
methane and propane audit materials.
Propane is used to calibrate the chromato-
graphic system for measurement of eth-
ylene and propylene, assuming the FID
response per carbon is constant for
compound to compound. In a few others
(e.g., vinyl chloride, ethylene oxide) gas-
eous standards are generated using
permeation tubes. The standards for most
of the other audit materials are prepared
using pure liquids that are volatilized in a
clean glass bulb or stainless steel sphere.
Audit requests are directed to RTI
through the EPA Project Officer. The
cylinder is then shipped by a freight
carrier to the laboratory being audited. A
letter is also included with the cylinders
which provides general instructions for
performance of the audit. The audit
concentrations are provided to the re-
questing agency audit coordinator. After
the laboratory being audited has analyzed
the contents of the cylinder, the audit
coordinator reports the value(s) to RTI,
which in turn reports both the measured
and accepted values to the Project Officer.
The laboratory being audited then is
responsible for shipping the cylinder back
to RTI.
Results and Discussion
To date, 149 individual audits have
been initiated, and 140 are complete. The
results obtained for a few typical per-
formance audits are shown in Table 2 and
the rest are given in the full status report.
Generally, the results of the audits show
close agreement (±15%) with the actual
cylinder concentrations measured by RTI.
Most of the cylinders in the repository
are analyzed at least four times to de-
termine the stability of these compounds;
Table 2. Typical Audit Results
some are analyzed as many as eight
times. Absolute accuracies for the cyl-
inder analyses have not been determined
due to lack of NBS standards for most of
the organic gas mixtures above one ppm.
An examination of the analysis data
shows values for individual cylinder anal-
yses usually vary by less than 10 percent
for four to eight analyses over two to six
years. As the number of analyses per
cylinder increases, detailed statistical
analyses will be performed. Statistical
analyses for 10 halocarbons and eight
other organics are presented in the
literature (1,2) and the statistical analyses
for the remaining compounds will be
presented in a future report.
Conclusions
Cylinder gases of hydrocarbons, halo-
carbons, and sulfur species have been
used successfully to assess the accuracy
of gas chromatographic systems used to
measure organic compounds in source
emissions. Absolute accuracy has not
been determined because of lack of
standard reference materials; instead
interlaboratory bias has been reported for
the performance audits conducted during
source testing. The interlaboratory bias
determined has been generally within 15
percent for both low and high concentra-
tion gases.
Thirty-nine out of 45 gaseous com-
pounds have demonstrated sufficient
stability in cylinders for use as audit
materials. Six compounds (ethylamine,
paradichlorobenzene, cyclohexanone, form-
aldehyde, 1,2-dibromoethylene and ani-
line) are not recommended as audit
materials for various reasons as dis-
cussed in the full status report. Detailed
statistical analyses which would separate
statistical deviations from true concentra-
tion changes with time for 18 gaseous
compounds have been recently published
and statistical analyses for the remaining
compounds will be presented in a future
report.
Industry
Maleic anhydride
production
Vinyl chloride
production
Vegetable oil plant
Degreasing Vent
Audit Material
Benzene in /V2
/ ,2 -Dichloroet hane
inN2
Hexane in N2
Jrichloroethylene
into
Cylinder
Concentration
(ppm)
138
300
9.3
462
82.2
1982
14.9
666
Client Audit
Bias(%)
-9.4
+4.7
+6.0
+3.7
+5.6
+3.0
-0.4
-8.7
-------
References
1. R. K. M. Jayanty, C. Parker, C. E.
Decker, W. F. Gutknecht, J. E. Knoll,
and D. J. von Lehmden, "Quality
Assurance for Emission Analysis
Systems," Environmental Science
and Technology, 77(6), 257-263A
(1983).
2. G. B. Howe, R. K. M. Jayanty, A. V.
Rao, W. F. Gutknecht, C. E. Decker,
and D. J. von Lehmden, "Evaluation
of Selected Gaseous Halocarbons
for Use in Source Test Performance
Audits," J. of Air Pollution Control
Association. 33(9) 823-826 (1983).
J. Sokash. G. B. Howe, R. K. M. Jayanty, and C. E. Decker are with Research
Triangle Institute, Research Triangle Park, NC 27709; the EPA author D. J. von
Lehmden (also the EPA Project Officer, see below) is with the Environmental
Monitoring Systems Laboratory, Research Triangle Park, NC 27711.
The complete report, entitled "Stability of Organic Audit Materials and Results of
Source Test Analysis Audits—Status Report #7," (Order No. PB 86-121
456/AS; Cost: $11.95, subject to 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 Systems Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
Official Business
Penalty for Private Use $300
EPA/600/S4-85/064
0000329 PS
U S ENVIR PROTECTION AGENCY
REGION 5 LIBRARY
230 S DEARBORN STREET
CHICAGO IL 60604
------- |