"
United States
Environmental Protection
Agency
Environmental Monitoring
Systems Laboratory
Research Triangle Park NC 27711
Research and Development
EPA/600/S2-86/117 Apr. 1987
&EPA Project Summary
Stability of Parts-Per-Million
Organic Cylinder Gases and
Results of Source Test Analysis
Audits: Status Report #8
G. B. Howe, R. K. M. Jayanty, C. E. Decker, and D. J. von Lehmden
,\
A repository of 45 gaseous com-
pounds including hydrocarbons, halo-
carbons, oxygenated, and sulfurous
species has been established under
contract with the U.S. Environmental
Protection Agency (EPA). The main ob-
jectives 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 chemical
manufacturing industries, (2) to cor-
roborate 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 176 different audits. The
results of these audits, a description of
the experimental procedures used for
analyses, and available stability data
are presented in this status report.
Generally the audit results are within
15 percent of the expected values.
Compound stabilities have been
determined through multiple analyses
of the cylinders containing them. Sta-
bility data for up to seven years is avail-
able for many compounds and over
four years for most compounds. Com-
pounds that are unstable and not suit-
able for use as an audit material are
identified.
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 Protect Report ordering In-
formation at tack).
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 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
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 certain
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
audits during 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
compounds are procured, as needed.
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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
**}.2-Dibromoethy/ene
Perchloroethylene
Vinyl Chloride
1 ,3-Butadiene
Acrylonitrile
**Aniline
Methyl Isobutyl Ketone
**Para-dichloroben2ene
**£thylamine
"Formaldehyde
Methylene Chloride
Carbon Tetrachloride
Freon 1 13
Methyl Chloroform
Ethylene Oxide
Propylene Oxide
Ally/ Chloride
Acrolein
Chlorobenzene
Carbon Disulfide
* *Cyclohexanone
***EPA Method 25 Mixture
Ethylene Dibromide
Tetrachloroethane
No. of
Cylinders
7
3
3
3
4
7
2
2
4
1
3
2
4
7
7
2
2
2
2
8
3
3
/
3
4
1
J
5
/
7
/
3
6
2
7
Concentration
Flange Ippm)
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
30-80
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
100-200
5-20
5-20
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
High Concentration Range
No. of
Cylinders
10
4
6
3
4
3
4
4
7
2
2
1
4
7
4
1
2
2
2
2
7
7
7
7
7
2
2
Concentration
Range (ppm)
60-400
300 - 700
3000 - 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
700-400
7000 - 3000
100-600
80 - 200
300-700
100-600
700-600
300-700
300-500
75-200
75-200
700 - 300
75-200
75O - 2OOO
50-300
Cylinder
Construction*
S
Al
Al
Al
Al
Al
Al
LS
Al
LS
S
S
Al
LS
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.
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 concen-
tration range, reliability, and ruggedness
for interstate shipping. The accuracy of
the supplier-reported levels of these
compounds 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 in the cylinders are im-
portant. Along with acquisition of new
compounds and verification of their con-
centrations, an extensive stability study
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Table 2. Typical Audit Results
Industry
Maleic anhydride
production
Vinyl chloride
production
Vegetable oilplant
Degreasmg Vent
Audit Material
Benzene in N2
1 , 2-Dichloroethane
mN2
Hexane in N2
Trichloroeth ylene
mN2
Cylinder
Concentration
(ppm)
138
300
93
462
822
1982
14.9
566
Client Audir
Bias 1%)
-9.4
+4.7
+6.0
+3.7
+5.6
+3.0
-0.4
-8.7
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 m
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, two months after acquisition, and
one year after acquisition.
All analyses are carried out using gas
chromatography 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 materials
National Bureau of Standards - Standard
Reference Materials (NBS-SRMs) of
methane and propane are used as stan-
dards for the measurement of methane
and propane audit materials. Propane is
used to calibrate the chromatographic
system for measurement 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 which are volatilized in
a clean glass bulb or stainless steel
sphere.
Audit requests are directed to RTI
through the EPA Proiect 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 con-
centrations are provided to the requesting
agency audit coordinator. After the lab-
oratory being audited has analyzed the
contents of the cylinder, the audit co-
ordinator 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, 176 individual audits have
been initiated, and 166 are complete.
The results obtained for a few typical
performance 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 deter-
mine the stability of these compounds;
some are analyzed as many as eight
times Absolute 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
examination of the analysis data shows
values for individual cylinder analyses
usually vary by less than ten 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 ten halocarbons and eight
other organics are presented in two
journal publications (1,2) and the statis-
tical analyses for the remaining com-
pounds 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 stan-
dard reference materials; instead inter-
laboratory 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,
formaldehyde, 1,2-dibromoethylene and
aniline) are not recommended as audit
materials for various reasons as discussed
in the full status report. Detailed statistical
analyses which would separate statistical
deviations from true concentration
changes with time for 18 gaseous com-
pounds have been published in a journal
publication and statistical analyses for
the remaining compounds will be pre-
sented 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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G. B. Howe, 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 #8." {Order
No. PB 87-141 461/AS; Cost: $13.95, 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 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/S2-86/117
0000329 PS
U S ENVIR
CHICAGO
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