United Stales
Environmental Protection
Agency
Environmental Monitoring Systems
Laboratory
Research Triangle Park IMC 27711
Research and Development
EPA-600/S4-84-002 Jan. 1984
Project Summary
Stability of Organic Audit
Materials and Results of Source
Test Analysis Audits—Status
Report #5
R. K. M. Jayanty, W. F. Gutknecht, C. E. Decker, J. E. Knoll, and D. J.
von Lehmden
A repository of 42 gaseous com-
pounds including hydrocarbon, halo-
carbon, and sulfur species has been
established under contract with the
U.S. Environmental Protection Agency
(EPA). The main objectives of this on-
going project are (1) to provide gas
mixtures to EPA, state/local agencies,
or their contractors, as performance
audits to assess the accuracy of source
emission measurements in certain or-
ganic chemical manufacturing indus-
tries, (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, 20 compounds have been
used to conduct 106 different audits.
The results of these audits and a descrip-
tion of the experimental procedures
used for analyses and available stability
data are presented in the status report.
Seventy percent of the audit results are
within 10 percent of the expected
values.
Compound stabilities have been deter-
mined through multiple analyses of the
cylinders containing them. Stability
values for all compounds are expressed
as percent change per month. Calcu-
lated changes are typically found to be a
few tenths of one percent per month,
though many of these changes may not
be significantly different from zero.
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 in-
formation at back).
Introduction
Accurate measurement of hydro-
carbons, halocarbons, and sulfur contain-
ing compounds in ambient and source
samples 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 standard gaseous com-
pounds. These standards 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.
The RTI repository currently contains
42 different compounds based on antici-
pated needs of EPA. Table 1 lists the
compounds, the concentration ranges of
each compound, and the number of
cylinders of each compound. Additional
compounds are obtained as needed.
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Table 1. Audit Materials Currently Held in the Repository
Low Concentration Range
No. of Concentration Cylinder
Compound Cylinders Range (ppm) Construction''
Benzene
Ethylene
Propy/ene
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 -Dichloroethylene
1,2-Dibromoethylene
Perchloroethylene
Vinyl Chloride
1,3-Butadiene
A crylonitrile
"Aniline
Methyl Isobutyl Ketone
""Paradichlorobenzene
""Ethylamine
** Formaldehyde
Methylene Chloride
Carbon Tetrachloride
Freon 1 13
Methyl Chloroform
Ethylene Oxide
Propy/ene Oxide
Allyl Chloride
Acrolein
Chlorobenzene
Carb on Disulfide
""Cyclohexanone
""EPA Method 25 Gas
14
4
4
-
4
2
4
2
2
2
2
4
2
4
-
1
1
2
2
2
2
2
9
1 '
3
1
1
2
2
-
1
1
1
1
1
1
1
1
1
-
1
3
8-13
5-20
5-20
—
5-20
5-20
5-20
5-20
5-20
5-20
5-20
3-70
20-50
5-20
—
30-50
30-50
5-20
5-20
5-20
5-20
5-20
5-30
5-30
5-20
5-20
5-20
5-20
5-20
—
5-20
5-20
5-20
5-20
5-20
5-20
5-20
5-20
5-20
—
5-20
700-200
S
Al
Al
-
Al
S
Al
S
S
S
S
Al
Al
Al
-
S
Al
Al
Al
Al
Al
S
S
LS.AI
Al
Al
S
Al
-
Al
Al
Al
Al
Al
Al
S
Al
Al
Al
Al
Al
High Concentration Range
No. of Concentration Cylinder
Cylinders Range (ppm) Construction''
17
4
6
4
4
4
2
2
2
2
2
2
-
2
4
1
-
-
2
2
2
2
2
-
-
3
-
7
-
-
-
-
-
-
-
-
7
7
-
-
7
-
3
60-400
300-700
3000-20,000
300-700
1000-6000IM).
200-700/EI
300-700
300-700
300-700
300-700
300-700
300-700
700-300
—
7000-3000
700-600
50-200
—
—
300-700
700-600
700-600
700-600
300-700
—
—
300-700
—
75
—
—
—
—
—
—
—
—
75-200
75-200
—
___
75-200
—
750-2000
Al. S
Al
Al
Al
Al
Al
S
Al
LS
S
S
S
-
LS
Al
S
-
-
LS
Al
Al
Al
LS
-
-
LS.AI
-
Al
-
-
-
-
-
-
-
-
Al
S
-
-
Al
-
Al
"Cylinder construction: Al - Aluminum. S = Steel, LS = Low Pressure Steel.
"Cylinders are no longer available in the repository since the compounds are found to be unstable in the cylinders.
"""The gas mixture contains an aliphatic, an aromatic and carbon dioxide in nitrogen. Concentrations^ shown are reported in ppmC.
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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 standard
gas during performance audits. The com-
pressed gas cylinder is especially suitable
as an audit device because of its simpli-
city, portability, low cost, flexibility in
analyte delivery over a broad concentra-
tion range, reliability, and ruggednessfor
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-
SRM's), commercial permeation tubes,
and/or reagent grade pure liquids as
standards. The permeation rate 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 important.
Along with acquisition of new compounds
and verification of their concentrations,
an extensive stability study is 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 iscontactedtodetermine
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 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. The cylinder
contents are then analyzed one month
after acquisition, two months after acqui-
sition, and one year after acquisition. The
cylinder contents are also analyzed 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. 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.
NBS-SRM's methane and propane are
used as standards for the measurement
of methane and propane audit materials.
These same gases are used to calibrate
the chromatographic system for measure-
ment of ethylene and propylene, assum-
ing the FID response per carbon is
constant for 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.
Audit requests are directed to RTI
through the EPA Project Officer. The
cylinder and a regulator are then shipped
by a freight carrier to the laboratory being
audited. A letter is also included with the
cylinders which provides general instruc-
tions for performance of the audit. The
audit concentrations 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 and regulator back to RTI.
Results and Discussion
To date, 106 individual audits have
been initiated, and 102 are complete. The
results obtained for a few typical per-
formance audits are shown in Table 2 and
Table 2. Typical Audit Results
the rest are given in the full report.
Generally, the results of the audits show
close agreement (+10%) with the actual
cylinder concentrations measured prior
to shipment.
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. An estimate of stability has been
made for each cylinder that has been
analyzed at least three times. This esti-
mate is a calculation of percent change in
concentration per month over the period
that RTI has performed analyses of the
cylinder contents. The calculation in-
volves a linear regression analysis of the
concentration of the analyte versus time
in days. The slope and intercept deter-
mined by this regression analysis are
then used to calculate percent change per
month by the relationship
% change/month = — x 100 x 30
y intercept
Examples of stability data are shown in
Table 3. Changes are noted for each
compound, although these changes may
not be significantly different from zero. As
the numbef of analyses per cylinder
increases, additional statistical analyses
will be performed.
Industry
Maleic anhydride
production
Vinyl chloride
production
Vegetable oil plant
Degreasing vent
Audit Material
Benzene in N2
1,2-Dichloroethane
in N2
Hexane in N2
Trichloroethylene
in N2
Cylinder
Concentration
(ppm)
138
300
9.3
462
82.2
1982
14.9
566
Client Audit
Bias 1%)
-9.4
+4.7
+6.0
+3.7
+5.6
+3.0
-0.4
-8.7
Table 3. Typical Stability Results
Compound
Benzene
Benzene
Hydrogen sulfide
1,2 Dichloroethane
Perchloroethylene
Acrylonitrile
Chloroform
Propylene
Concentration Period of Cylinder
(ppm) Analyses (Months)
12.2
296
9.15
439
13.0
20.1
348
14.8
25
27
37
28
13
28
33
25
% Change/Month
-0.15
0.01
-0.05
-O.JO
-0.23
-1.07
-0.20
0.06
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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 reportedfor
the performance audits conducted during
source testing. The interlaboratory bias
determined has been generally within 10
percent for both low and high concentra-
tion gases.
Thirty-seven out of 42 gaseous com-
pounds have demonstrated sufficient
stability in cylinders for use as audit
materials. Five compounds (ethylamine,
paradichlorobenzene cyclohexane, form-
aldehyde and aniline) are not recom-
mended as audit materials for various
reasons as discussed in the full report.
The estimates of stability are reported in
terms of percent change per month.
Detailed statistical analyses which would
separate statistical deviations from true
concentration change with time for 14
compounds have been recently published
in a journal publication and statistical
analyses for the remaining compounds
are in progress and will be presented in
the final report.
R. K. M. Jayanty, W. F. Gutknecht, and C. E. Decker are with Research Triangle
Institute. Research Triangle Park, NC 27709.
J. E. Knoll and D. J. von Lehmden are the EPA Project Officers (see below).
The complete report, entitled "Stability of Organic Audit Materials and Results of
Source Test Analysis Audits—Status Report #5," (Order No. PB 84-128 578;
Cost: $11.50. 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
*U.S. GOVERNMENT PRINTING OFFICE: 1984-759-015/7
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
Official Business
Penalty for Private Use $300
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