United States
Environmental Protection
Agency
Environmental Monitoring
Systems Laboratory
Research Triangle Park NC 27711
Research and Development
EPA/600/S4-88/002 Mar. 1988
oEPA Project Summary
Stability of Parts-Per-Million
Organic Cylinder Gases and
Results of Source Test Analysis
Audits—Status Report #9
G. B. Howe, J. R. Albritton, C. K. Sokol, R. K. M. Jayanty, C. E. Decker, and
D. J. von Lehmden
The U.S. Environmental Protection
Agency (EPA) has evaluated the suit-
ability of 45 gaseous compounds
including hydrocarbons, halocarbons,
oxygenated, and sulfurous species for
use as standards for measuring station-
ary source emissions. The main objec-
tives of this on-going project are (1) to
provide gas mixtures to EPA, state/
local agencies, or their contractors, as
performance audit standards to assess
the accuracy of measuring source
emissions from certain organic chem-
ical manufacturing industries, (2) to
corroborate 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, and (4) to explore the
feasibility of new audit materials as
requested by EPA.
Thus far, 31 mixtures have been used
to conduct 214 different audits. The
results of these audits, a description of
the experimental procedures used for
analyses, and available stability data
are presented in the full status report.
Compound stabilities have been
determined through multiple analyses
of the cylinders containing them.
Stability data for up to 8 years is
available for many compounds and over
5 years for most compounds. Com-
pounds that are unstable and not
suitable for use as an audit material are
identified.
This Project Summary was devel-
oped by EPA's Environmental Monitor-
ing Systems Laboratory, Research
Triangle Park, NC. 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
Accurate measurement of hydrocar-
bons, halocarbons, and sulfur-containing
compounds in ambient and source
samples is essential to any environmen-
tal monitoring program. The potential for
achieving acceptable accuracy is
enhanced 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 Monitor-
ing Systems Laboratory, U.S. Environ-
mental Protection Agency (EPA), has
responded to this need through the
development of cylinder gases for 39
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 mea-
surements in certain organic manufac-
turing industries.
Currently 45 different compounds
have been investigated as audit mate-
rials. Six of these gaseous compounds
have been found to be unstable in
cylinders and not suitable as audit
materials. The other 39 gaseous com-
pounds in the repository are suitable for
conducting performance audits during
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source testing. Table 1 lists the 45
compounds, the concentration ranges for
each compound, the number of cylinders
of each compound, and the cylinder
construction material. Additional com-
pounds are procured, as needed.
The gaseous compounds are acquired
from commercial suppliers in com-
pressed gas cylinders; these same
cylinders, along with an appropriate
delivery system, are used directly as
sources of the gaseous compounds
during performance audits. The com-
pressed gas cylinder is especially suit-
able as an audit device because of its
simplicity, portability, low cost, flexibility
in analyte delivery over a broad concen-
tration range, reliability, and ruggedness
for interstate shipping. The accuracy of
the supplier-reported levels of these
compounds are verified through meaj
surement using National Bureau of
Standards - Standard Reference Mate-
rials (NBS-SRMs), commercial perme-
ation 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
Table 1. A udit Materials Currently in the Repository
Low Concentration flange
High Concentration flange
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
J, 3 -Butadiene
Acrylonitrile
Aniline**
Methyl Isobutyl Ketone
Paradichlorobenzene * *
Ethylamine**
Formaldehyde**
Methyl Chloride
Carbon Tetrachloride
Freon 113
Methyl Chloroform
Ethylene Oxide
Propylene Oxide
Ally 1 Chloride
Acrolein
Chlorobenzene
Carbon Disulfide
Cyclohexanone * *
EPA Method 25 Mixture***
Ethylene Dibromide
Tetrachloroethane
No. of
Cylinders
7
3
3
-
3
4
6
2
2
4
1
3
2
4
--
4
1
2
2
2
--
2
8
3
3
--
1
—
--
--
4
4
1
1
5
1
1
1
3
--
--
6
2
1
Concentration
Range Ippm)
5 -
5 -
5 -
--
5 -
5 •
5 -
5 -
5 -
5 -
5 -
3 -
20 -
5 -
--
5 -
30 -
3 -
5 -
5 -
--
5 -
5 -
5 -
5 -
--
5 -
--
--
--
1 -
5 -
5 -
5 -
5 -
5 •
5 -
5 -
5 -
--
--
100 -
5 •
5 -
20
20
20
20
20
SO
20
20
20
20
10
90
20
50
80
20
20
20
20
30
60
20
20
20
20
20
20
20
20
20
20
20
200
20
20
Cylinder
Construction*
S
Al
Al
--
Al
Al
Al
S
S
S
Al
Al
Al
Al
-
S
Al
Al
Al
Al
—
S
S
Al
Al
--
Al
—
-
-•
Al
Al
Al
Al
Al
Al
S
Al
Al
--
--
Al
S
S
No. of
Cylinders
10
4
6
3
4
3
4
4
7
2
2
1
4
--
--
4
1
--
--
2
2
2
--
2
-•
--
/
--
--
--
--
--
--
--
--
--
/
7
;
--
1
--
4
2
--
Concentration Cylinder
Range fppm) Construction*
60
300
3,000
300
1.000 -
200 -
300
- 400
- 700
- 20.000
- 700
9,000(M),
800(E)
- 700
1.000-20.000
100
100
300
300
300
100
100
80
300
100
100
300
300
75
75
100
75
750
50
- 700
- 700
- 700
- 700
- 700
- 400
--
- 600
- 200
--
-.
- 700
- 600
- 600
--
- 700
-
--
- 500
--
--
--
--
--
--
--
--
--
--
- 200
- 200
- 300
--
- 200
--
- 2,000
- 300
"
S
Al
Al
Al
Al
Al
Al
LS
Al
LS
S
S
Al
--
--
Al
Al
--
Al
Al
Al
--
LS
--
--
Al
--
--
--
--
--
--
--
--
--
—
Al
S
Al
--
Al
—
Al
S
"
*AI = 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, and carbon dioxide in nitrogen. Concentrations shown are
in ppmC.
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compounds in the cylinders are impor-
tant. 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 con-
tents of each of the cylinders in the
repository.
Procedure
Once a compound is chosen, a com-
mercial supplier is contacted to deter-
mine if a cylinder containing that com-
pound can be prepared. If so, the
manufacturer prepares the cylinder
gases and determines 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 acquisition, two months after
acquisition, and one year after
acquisition.
All analyses are carried out using gas
chromatography (GC). The column and
detector are chosen so as to be optimum
for the compound being measured. Three
types of standards are used to generate
gas concentrations for calibration of the
GC for the measurement of audit mate-
rials. 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 chroma-
tographic system for measurement of
ethane, ethylene and propylene, assum-
ing the FID response per carbon is
constant from compound to compound.
In a few others (e.g., vinyl chloride,
ethylene oxide) gaseous standards are
generated using permeation tubes. The
standards for most of the other audit
materials are prepared using pure liquids
which 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 that provides general instruc-
tions for performing the audit is included
with the cylinders. The audit concentra-
tions are provided to the requesting
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, 214 individual audits have
been initiated and 194 are complete. The
results obtained for a few typical
performance audits are shown in Table
2 and the rest are given in the fall status
report. Generally, the results of the
audits show close agreement (± 15%)
with the actual cylinder concentrations
measured by RTI.
Most of the cylinder gases are analyzed
at least four times to determine the
stability of these compounds; some are
analyzed as many as nine times. Abso-
lute accuracies for the cylinder analyses
have not been determined due to lack
of NBS standards for most of the organic
gas mixtures above one ppm. An exam-
ination of the analysis data shows values
for individual cylinder analyses usually
vary by less than ten percent for four to
nine analyses over two to seven years.
As the number of analyses per cylinder
increases, detailed statistical analyses
will be performed. Statistical analyses for
ten halocarbons and eight other organics
are presented in two journal publica-
tions1'2 and the statistical analyses for
the remaining compounds will be pres-
ented 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
Table 2. Typical Audit Results
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 concen-
tration 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,
formaldehyde, 1,2-dibromoethylene and
aniline) are not recommended as audit
materials for various reasons as dis-
cussed in the full status report. Detailed
statistical analyses which would separ-
ate statistical deviations from true
concentration changes with time for 18
gaseous compounds have been pub-
lished in a journal publication and
statistical analyses for the remaining
compounds will be presented in a future
report.
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," Environmetnal 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 Selection Gaseous
Halocarbons for Use in Source Test
Performance Audits," J. of Air
Pollution Control Association,
33(9):823-826(1983).
Industry
Maleic anhydride
production
Vinyl chloride
production
Vegetable oil plant
Degreasing Vent
Audit Material
Benzene in /V2
7 ,2 -Dichloroethane
inNz
Hexane in N2
Trichloroethylene
inNi
Cylinder
Concentration
(ppm)
138
300
9.3
462
82.2
1982
14.9
566
Client Audit
Bias (%)
-9.4
+4.7
+6.0
+3.7
+5.6
+3.0
-0.4
-8.7
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G. B. Howe. J. R. Albritton, C. K. Sokol. R. K. M. Jayanty. and C. E. Decker
are with Research Triangle Institute. Research Triangle Park, NC 27709.
DarrylJ. von Lehmden is the EPA Project Officer (see below).
The complete report, entitled "Stability of Parts-Per-Million Organic Cylinder
Gases and Results of Source Test Analysis Audits—Status Report #3," (Order
No. PB 88-158 761 /AS; Cost: $14.95, 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 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 S300
EPA/600/S4-88/002
I ,.. i.ico ,, n / y
* : -. U .(. £
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CHICAGO
•ft-U.S GOVERNMENT PRINTING OFFICE 1988— 548-013/
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