United States
Environmental Protection
Agency
Atmospheric Research and
Exposure Assessment Laboratory
Research Triangle Park NC 27711
Research and Development
EPA/600/S3-89/017Aug. 1989
&EPA Project Summary
Status Report #10Stability of
Parts-Per-Million Organic
Cylinder Gases and Results of
Source Test Analysis Audits
G. B. Howe, J. R. Albritton, S. B. Tompkins, R. K. M. Jayanty, and
C. E. Decker
The U.S. Environmental Protection
Agency (EPA) has evaluated the suit-
ability of 45 gaseous compounds in-
cluding hydrocarbons, halocarbons,
oxygenated, and sulfurous species
for use as standards for measuring
stationary source emissions. The
main objectives of this on-going pro-
ject 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 chemical manufactur-
ing industries, (2) to corroborate the
vendor's certified analysis of the gas
mixtures by in-house analysis, (3) to
determine stability of the gas
mixtures with time by in-house analy-
sis, and (4) to explore the feasibility
of new audit materials as requested
by EPA.
Thus far, 31 compounds have been
used to conduct 232 different audits.
The results of these audits, a de-
scription of the experimental proce-
dures used for analyses, and avail-
able stability data are presented in
the full status report.
Compound stabilities have been
determined through multiple analy-
ses of the cylinders containing them.
Stability data for up to 9 years is
available for many compounds and
over 6 years for most compounds.
Compounds that are unstable and not
suitable for use as an audit material
are identified.
This Project Summary was devel-
oped by EPA's Atmospheric Research
and Exposure Assessment Laboratory,
Research Triangle Park, NC, to an-
nounce 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 sam-
ples is essential to any environmental
monitoring program. The potential for
achieving acceptable accuracy is enhanc-
ed by the availability of reliable standards
which 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 Pro-
tection 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 measurements in certain
organic manufacturing industries.
Currently 45 different compounds have
been investigated as audit materials
(Table 1). Six of these gaseous com-
pounds 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
source testing. Additional compounds are
procured, as needed.
The gaseous compounds are acquired
from commercial suppliers in compres-
sed gas cylinders; these same cylinders,
along with an appropriate delivery sys-
tem, are used directly as sources of the
gaseous compounds during performance
audits. The compressed gas cylinder is
especially suitable as an audit device be-
cause of its simplicity, portability, low
cost, flexibility in analyte delivery over a
broad concentration range, reliability, and
ruggedness for interstate shipping. The
accuracy of the supplier-reported levels
of these compounds are verified through
measurement using National Bureau of
Standards - Standard Reference Materi-
als (NBS-SRMs), commercial permeation
tubes, and/or reagent grade pure liquids
as standards. The permeation rates of the
commerically available tubes are verified
by RTI before use.
Requests for audit cylinders are di-
rected to RTI thorugh the EPA Project
Officer. Audit cylinders are then shipped
by a freight carrier to the laboratory/con-
tractor being audited. A letter that pro-
vides general instructions for perform-
ance of the audit is also included with the
cylinders. The audit concentrations are
provided to the requesting agency audit
coordinator. After the laboratory/contrac-
tor being audited has analyzed the con-
tents of the cylinder, the audit coordinator
reports the value(s) to RTI, which in turn
reports both the audit value and RTI
measured concentrations to the EPA Pro-
ject Officer. The laboratory/contractor
being audited then is responsible for
shipping the cylinder back to RTI.
Results and Discussion
To date, 232 induvidual audits have
been initiated, and 207 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 audit results show
close agreement (±15%) with the actual
cylinder concentrations measured by
RTI.
The accuracy of the "known" cylinder
concentrations and the stability of the
compounds in the cylinders are impor-
tant. Along with acquisition of new com-
pounds and verification of their concen-
trations, an extensive stability study is
being performed. This study involves
periodic analyses of the contents of each
of the cylinders.
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 man-
ufacturer prepares the cylinder gases and
determines the concentration of the
analyte in the cylinder. The cylinder is
sent to RTI where its contents are anal-
yzed usually within seven days of its ar-
rival. 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 acqui-
sition, and one year after acquisition.
All analyses are performed using gas
chromatography. The column and detec-
tor 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
materials. 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
chromatographic system for measure-
ment of ethane, ethylene and propylene,
assuming 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
that are volatilized in a clean glass bulb
or stainless steel sphere.
Most of the cylinder gases are ana-
lyzed 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 fo
ten halocarbons and eight other organic:
are presented in two journal publication:
(1,2) and the statistical analyses for thi
remaining compounds will be presentee
in a future report.
Conclusions
Cylinder gases of hydrocarbons, halo
carbons, and sulfur species have beer
used successfully to assess the accuracy
of gas chromatographic systems used t(
measure organic compounds in source
emissions, Absolute accuracy has no
been determined because of lack o
standard reference materials; msteac
mterlaboratory bias has been reported fo
the performance audits conducted durinc
source testing. The interlaboratory bia:
determined has been generally within 15
percent for both low and high concentra
tion gases.
Thirty-nine of the 45 gaseous com-
pounds have demonstrated sufficient sta-
bility in cylinders for use as audit materi-
als. Six compounds (ethylamme, paradi-
chlorobenzene, cyclohexanone, formalde-
hyde, 1,2-dibromoethylene and aniline,
are not recommended as audit materials
for various reasons as discussed in the
full status report. Detailed statistical ana-
lyses which would separate statistical de-
viations from true concentration changes
with time for 18 gaseous compounds
have been published in a journal publica-
tion and statistical analyses for the re-
maining 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," Environmental Science
and Technology, 17 (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).
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Table 1. Audit Materials Currently Available
Low Concentration Range
High 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"
Perchloroethy/ene
Vinyl Chloride
1 ,3-Butadiene
Acrylon/trile
Aniline"
Methyl Isobutyl Ketone
Para-dichlorobenzene""
Ethylamine""
Fomaldehyde"
Methylene Chloride
Carbon Tetrachloride
Freon 113
Methyl Chloroform
Ethylene Oxide
Propylene Oxide
A/lyl Chloride
Acrolein
Chlorobenzene
Carbon Bisulfide
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
5
3
1
-
-
4
4
1
1
5
1
1
1
3
2
-
5
2
1
Concentration
Range
5-20
5-20
5-20
-
5-20
5-20
5-50
5-20
5-20
5-20
5-20
3-10
20-90
5-20
-
5-50
30-80
3-20
5-20
5-20
-
5-20
5-30
5-60
5-20
5-20
-
-
1-20
5-20
5-20
5-20
5-20
5-20
5-20
5-20
5-20
5-20
-
100-200
5-20
5-20
Cylinder
Construction
S
Al
At
-
Al
Al
Al
S
S
S
Al
Al
Al
Al
-
Al
A!
Al
Al
Al
-
S
S
Al
Al
Al
-
-
Al
Al
Al
Al
Al
Al
S
Al
Al
Al
-
Al
S
S
No. of
Cylinders
10
4
3
4
3
4
6
2
2
1
3
-
-
3
1
-
2
2
2
-
2
-
-
1
-
-
-
-
-
-
-
1
1
1
1
-
5
2
Concentration
Range
60-400
300-700
3,000-20,000
300-700
1000-9000(M)
200-800(E)
300-700
1000-20.000
100-700
100-700
300-700
300-700
300-700
100-400
-
-
1 00-600
80-200
-
300-700
/ 00-600
700-600
-
300-700
-
300-500
-
-
-
-
-
75-200
75-200
/ 00-600
75-200
-
750-2000
50-300
Cylinder
Construction
S
Al
Al
Al
Al
Al
Al
LS
Al
LS
S
S
Al
-
-
Al
Al
-
Al
Al
Al
-
i.S
-
Al
-
-
Al
S
Al
_
Al
Al
S
"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, and carbon dioxide in nitrogen.
Concentrations are shown in ppmC.
-------
Table 2. Typical Audit Results
Industry Audit Material
Cylinder
Concentration (ppm) Client Audit Bias (%)
Maleic anhydride
production
Vinyl chloride
production
Vegetable oil plant
Degreasing vent
Benzene in N2
1,2-Dichloroethane
in N2
Hexane in N2
Trichloroethylene
in N2
138
300
9.3
462
82.2
1982
14.9
566
-9.4
+ 4.7
+ 6.0
+ 3.7
+ 5.6
+ 3.0
-0.4
-8.7
G. B. Howe, J. R. Albritton, S. B. Tompkins, 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
Atmospheric Research and Exposure Assessment Laboratory, Research Triangle
Park, NC 27711.
The complete report, entitled "Status Report #70Stability of Parts-Per-Million
Organic Cylinder Gases and Results of Source Test Analysis Audits," (Order No.
PB 89-155 261/AS; Cost: $21.95, 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:
Atmospheric Research and Exposure Assessment Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
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