EPA/600/A-92/252
DEVELOPMENT OF AN ANALYSIS METHOD FOR TOTAL
NONMETHANE VOLATILE ORGANIC CARBON EMISSIONS
FROM STATIONARY SOURCES
Merrill D. Jackson, Joseph E. Knoll, and M. Rodney Midgett
Methods Research and Development Division
Atmospheric Research and Exposure Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
Samuel C Foster II, James F. McGaughey, and Raymond G. Merrill Jr.
Radian Corporation
P.O. Box 13000
Research Triangle Park, North Carolina 27709
ABSTRACT
The accurate measurement of the total nonmethane volatile organic carbon emissions from
stationary sources is critical to characterizing of many industrial processes and for regulating
according to the Clean Air Act. Current methods are difficult to use and the ability to do
performance audits has been marginal, especially at low concentrations (50 parts per million of
carbon, ppmc).
One of the key elements for an ideal measurement technique would be a detector that
responds to all classes of organic compounds equally, based on the number of carbon atoms
present. A commercially available catalytic flame ionization detector (CFID) has shown promise
in this area. Laboratory studies with a CFID were performed to determine the response of
compounds with various functional groups. These classes included brominated, chlorinated,
nitrogenated, oxygenated, aromatic, and non-aromatic compounds. The response of each
compound is compared to the response of an alkane with the same number of carbon atoms. This
paper will discuss this phase of the experimental work. Future work with this detector will
incorporate an approach for sampling, sample recovery, and field tests for comparison to the EPA
Method 25.
INTRODUCTION
The accurate measurement of the total nonmethane volatile organic carbon emissions from
stationary sources is critical to the characterization of many industrial processes. Current methods
are difficult to use especially at low concentrations (50 ppmc). One of the key elements for an
ideal measurement technique would be a detector that responds to all classes of organic
compounds, equally based on the number of carbon atoms present. The flame ionization detector
(FID, the detector of choice for most of the analytical methods) responds to unsubstituted alkanes
in this manner. However, when functional groups are added or when the structure (aromatic or
cyclic) changes, the response no longer follows this pattern. A commercially available catalytic
flame ionization detector (CFID) has shown promise in this area.
The CFID uses a ceramic source coated with a nickel/aluminum oxide to act as a
combination ignitor, polarizer, and catalytic surface in an H2/air flame environment. The CFID
ceramic catalyst temperature is controlled through a power supply that is adjustable from 0.0 to 4.0
amperes (amps). Increasing the current to the catalyst raises the source temperature. A balance
between the catalyst temperature and the detector temperature is essential to the complete
combustion of organic compounds. Generally, the catalyst temperature can be varied from 400 to
800°C, and the detector temperature can be varied between 100 to 400°C.1
The detector's performance was evaluated by analyzing organic compounds with various
functiopal groups (halogen, oxygen, nitrogen, and aromatic). Functional groups were evaluated at
different currents and fuel ratios until an optimal current and fuel ratio was found that gave a
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universal response. Once the optimal conditions were determined, the performance of the CUD
was compared to the performance of an FID. The overall performance of the CFID was evaluated
by analyzing 61 organic compounds. The response ratio for each compound was compared to the
response ratio of straight-chained alkanes. All of the response ratios are based on the number of
nanomoles (nmoles) that were injected on column.
EXPERIMENTAL METHOD
A CFID and power supply available from DETector Engineering & Technology, Inc. (DET)
was installed on a Varian 3600 gas chromatograph (GC). The power supply current was variable
from 0.0 to 4.0 amps. The FID was a Varian FID installed on a Varian 3400 GC. Tht analytical
column, used for all analyses, was a DB-5,0.54 millimeter x 30 meter, fused silica capillary column.
A PE Nelson 3000 series Chromatography Data System was used for data acquisition and
processing.
The detector tower temperature was set at 310eC for all of the experiments. The
temperature limit for the column, as indicated by the manufacturer, was 350°C. The operating
conditions were well below the limits of the column.
The fuel/air ratio, as recommended by DET for the CFTD, was a 1:10 mix of hydrogen and
air. To minimize source deterioration, DET recommended that the flow of hydrogen not exceed
25 mL/min and the flow of air not exceed 250 mL/min. The maximum flows were chosen for the
initial studies, and a different ratio was later evaluated.
A mix of four aliphatic hydrocarbons was prepared at a concentration of 1.0 millimoles
(mmolc) each in dichloromethane. This mix was used as the baseline for evaluating the detector
response to the number of carbon atoms present. A solution of dichloromethane, trichJoromethane,
and tetrachloromethane (single carbon chloroalkanes) in nonanewas prepared with each compound
at 0.12 mmol. The chloroalkane solution was analyzed on the CFID with the current setatO.O and
on the FID for comparison. The chloroalkane solution was then analyzed on the CFID at six
different currents: 0.0,2.0,2.4,2,8,3.2, and 3.6 amps, to find the optimal current for the chlorinated
compounds, A mix of six aliphatic hydrocarbons was prepared at a concentration of 0.013 mmol
in dichloromethane.
Different mixtures containing compounds of specific functional groups were then prepared.
The standards were prepared at a nominal concentration of 500 pg/ml. An internal standard (IS),
nonane, was added to each solution at a concentration of 115 pg/ml. The standards were analyzed
at the optimal current, and at a higher current to determine the effects on the different functional
groups.
The response factor (RF) for each compound was calculated using equation 1. The response
factor to nmol was plotted against the number of carbons in each compound.
RF *= (Compound area/IS area) * (1/nmoles of compound injected) (1)
A "least-squares-fit" was applied to the data points from each functional groups with the slope,
intercept, and correlation coefficient calculated for each of the generated fines. The linear
regression information was compared to the results for the aliphatic hydrocarbons. The number of
carbons that each compound deviated from the aliphatic line was calculated using equation 2.
No. Carbons Deviated = No. of carbons in compound - (2)
I(RF of compound - intercept of base line)/(slope of base line))
The average number of deviated carbons was calculated for each class of compounds for
comparison to the aliphatic hydrocarbons.
RESULTS AND DISCUSSION
A mixture of four straight-chained alkanes (heptane, octane, nonane, and decane) was
analyzed on the CFTD and compared to the FID as a preliminary test of detector linearity. The
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CFID was comparable to the FED, with both detectors showing linearity with increasing carbon
number for the aliphatic hydrocarbon mix.
Chlorinated compounds were chosen for the initial experiments because of their low response
on FID, as compared to alkanes. Single carbon compounds (dichloromethane, trichloromethane,
and tetrachJoromethane) were selected so that the only difference between the compounds was the
number of chlorines present. With 0.0 amps of current applied to the detector, the chloroalkanes
responded simHarly,on a molar basis, when analyzed on the CFID. When the chloroalkanes were
analyzed on the FID, the response decreased as the number of chlorines increased. The
chloroalkane standard was then analyzed at 0.0, 2.0, 2.4, 2.8, 3.2, and 3.6 amps to determine the
optimal current for this class of compounds. As the current was increased, the sensitivity increased,
but the baseline became increasingly noisy. The best compromise between sensitivity, uniform
response, and baseline stability was found to be at a current setting of 2,4 amps.
A mixture of six aliphatic hydrocarbons (hexane, heptane, octane, decane, tetradecane,
hexadecane) was prepared from stock standards four times and analyzed in duplicate using the
CFID with the current set at 2.4 amps (Figure 1). The RFs were averaged and a "least-squares-fit"
was applied to the data points (Table I). The aliphatic hydrocarbons responded linearly on the
CFID with a correlation coefficient of 0.992, and the resulting line was used as the baseline for
comparison with the other compound classes.
Separate mixtures of compounds from five functional groups (aromatic, brominated,
chlorinated, nitrogenated, oxygenated) with nonane as the IS were prepared and analyzed at 2.4
amps. The RF for each compound was compared to the RF for the aliphatic hydrocarbons. Some
of the compounds could be placed in several of the functional groups, but they were grouped
together based on the predominate functional group. Additional studies were performed at higher
currents for the aliphatic, aromatic, chlorinated and oxygenated compounds In an attempt to
improve linearity and sensitivity.
Figures 1 through 6 provide a graphical representation of the CFID response versus carbon
number for the six functional groups studied at 2.4 amps. For comparison purposes, a least-
squares-fit" was performed on each data set that generated a value for the slope and correlation
coefficient. The two values for each data set were compared to those generated for the aliphatics
compounds, which was used as the target or theoretical situation. The data from the "least-squares-
fit" for the aliphatic compounds and the RF calculated for each compound associated with the
other functional groups were used to calculate the number of carbon atoms for each compound.
This experimentally determined value for the number of carbon atoms was then compared to the
actual number of carbon atoms in each compound (Table I).
The plotted slopes for the nitrogenated and oxygenated compounds (Figures 5 and 6) are similar
to that for the aliphatic compounds, which indicates that the responses increase with the number
of carbon atoms (as expected for normal alkanes). However, the magnitude of the responses was
less than that for the aliphatics, making the experimentally determined carbon number for the
nitrogenated compounds, on the average, low by approximately 0.5 carbon and the oxygenated
compounds low by approximately 1 carbon.
The slopes for the aromatic and brominated (Figures 2 and 3) compounds were greater than
that for the aliphatics. This shows that the CFID response increases as carbon numbers increase
but at a greater magnitude than for aliphatic compounds. The experimentally determined carbon
number for the aromatics was found to be high, on the average, at 0.4 carbons, whereas, the
experimental number of carbons for the brominated compounds was found to be equal to the
number of actual carbons.
The slope for the chlorinated compounds was less than for the aliphatics, indicating that the
CFID response increases as the number of carbons increase, but at a magnitude less than that for
the aliphatics. The experimentally determined number of carbons was high, on the average, by 0.4
carbons. The correlation coefficients were all greater than 0.93. This indicates that all of the data
points lay on or near the resulting line.
Several functional groups were analyzed at a higher current to possibly improve linearity and
sensitivity. Aliphatic, aromatic, oxygenated, and chlorinated compounds were analyzed at 32 amps.
Table II shows the resulting linear regression data for the compounds that were analyzed. Linearity
-was not improved with the correlation coefficients less than 0.96. Sensitivity toward increasing
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carbon numbers increased slightly for the oxygenated compounds, compared to the slope of the
lines at 2.4 amps and 3.2 amps, and the experimentally determined number of carbons, on average,
increased by 0.4 carbons. Sensitivity did not increase for the chlorinated compounds, with the slope
increasing and the experimentally determined number of carbons, on average, increased to 2
carbons.
The oxygenated compounds were of special interest, since they are a major component of
many Method 25 analyzes. They showed a reduced response, as compared to the aliphatic
hydrocarbons, therefore it was important to closely examine this class of compounds. As noted
above, increasing the current did not change the overall response of the compounds. The fuel-gas
mixture was changed to 40 mL/min for hydrogen and 250 mL/min for air. The CFID did not
behave well at this fuel ratio. The baseline was erratic, and the signal dropped below the baseline
after the solvent peak passed through the column. The CFID behaves better at a 1:10 gas ratio;
therefore the ratio cannot be changed to achieve better sensitivity towards a functional group.
As a confirmation of the response of the CFID toward the oxygenated compounds, the
oxygenated compounds were analyzed with aliphatic hydrocarbons on the CFID at 2.4 amps and
the FID. The CFID response to the oxygenated compounds was the same as the FID response.
Table III lists the compounds analyzed and the response on the CFID and the FID. The number
of carbons deviated from the target aliphatic line was calculated and the results are listed in Table
III. The average number of carbons deviated from the target response was -1.25 for both the CFID
and the FID.
There were 61 compounds analyzed on the CFID. Figure 6 shows all of the compounds
analyzed on the CFID, and Table IV lists all of the compounds that were analyzed in order of
increasing response factor. The compounds show that the CFID response increased as the number
of carbons increased. The response for the compounds that are showing a low response are only
low, on average, by 1 carbon atom,
CONCLUSIONS
The CFID is a detector that acts as a carbon counter, in that the response to compounds
increases linearly as the number of carbons increases. Oxygenated compounds did not respond
as well as the other functional groups but did respond linearly with increasing carbon number. For
halogenated compounds, the CFTD out performed the FID with a response that was unaffected by
the number of chlorine atoms and responded linearly with increasing carbon number. The CFID
at 2.4 amps results averaged one carbon number or less deviation when compared with aliphate
compounds. The CFID has remained stable after over 6 months of continuous use. The CFID is
a versatile detector that is able to overcome some of the selectivity problems of the FID. The
CFID appears to be a good choice as a universal detector that may increase the overall detection
limit of current stationary source analyses methods.
DISCLAIMER
The information in this document has been funded wholly or in part by the United States
Environmental Protection Agency (EPA) under contract 68-Dl-OOiO to Radian Corporation. It has
been subjected to Agency review and approved for publication. Mention of trade names or
commercial products does not constitute endorsement or recommendation for use.
REFERENCES
1. Theory and Operation of the TTD / CFID Detectors. FTP Detector. Remote FID Detector.
Tandem TIP Detector. FID Detector: DETector Engineering & Technology, Inc., 1991, pp 1-2 -
1-6.
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Table I. Linear Regression for Compounds at 2.4 amps.
Functional No. Slope Intercept
Group Compounds
Analyzed
Con. Avg Deviation
Coef. From Target
( No. Carbons }
Aromatic
Brominated
Chlorinated
Aliphatic
Nitrogenated
Oxygenated
7
3
20
6
8
17
0.0611
0.0501
0.0401
0.0435
0.0477
0.0456
.1028
-0.0011
0.0461
0.0154
0.0380
0.0349
0.9872
0.9990
0.9642
0.9964
0.9771
0.9711
0.41
0.07
0.40
0.01
030
-0.90
Table D. Linear Regression for Compounds at 32 amps.
Functional No. Slope Intercept
Croup Compounds
Analyzed
Aromatic
Chlorinated
Aliphatic
Oxygenated
7
15
3
4
0.0453
0.0328
0.0155
0.0490
0.0159
0.1345
03*47
0.0293
Corr. Avg Deviation
Coef. From Target
( No. Carbons )
0.9284
0.8968
0.9538
0.7969
OJ3
1.99
0.10
-0.49
Table HI. CHD at 2.4 amps vs FID for Oxygenated Compounds.
Compound
4-Methyl-2-Pentanone
p-Tolualdehydc
2-Butanonc
Acetone
Ethyl Ether
Methanol
Propanol
Ethyl Acetate
RF
CFID
0.1482
03234
0.1438
0.0898
0.1410
0.0394
0.1114
0.1253
RF CFID DEV.
FID CARBONS
0.1479
03291
0.1457
0.0902
0.1480
0.0363
0.1075
0.1215
-3.0
0.9
-1.1
-13
-1.1
05
-0.8
-15
FID DEV.
CARBONS
-3.0
-0.8
1.0
-13
-1.0
05
-0.9
.1.6
Table IV. Organic Compounds Analyzed on CFID.
Aliphatic Aromatic Brominated
Chlorinated
Nitrogenated
Oxygenated
Hexane
Heptane
Octane
Decane
Tetradecane
Hexadecane
Benzene Dibromomethane
Toluene 1,2-Dibromoetbane
o-Xylene Bromobenzene
Etbylbeazene
m-Xylene
p-Xylene
Methylene chloride 4-Nitrophenol
Chloroform 2,4-Duutroaniline
Carbon tetrachloride 2,4-Dinitrotoluene
1,1-DicWoroethylene 4-Nitroaniline
1,2-DickIoroethanc 1,4-DinJtrobenzene
1,1,2-Trichloroethane 2,6-DinitrotoIuenc
1,1,2,2-Tetrachlorocthanc 1-Nitronapbtbalene
Trichloroethylene Diphenylamine
TetrachJoroetbylene
1,2-Dichloropropane
1,2,3-TricUoropropaae
Hexachlorocyclopentadiene
2-Chlorophenol
1,2,4-Trichlorobenzene
Dichlorobenzene
4-Chloro-3-melhyl-phenol
o-Chloropbenol
1,4-Dichlorobenzene
4-Chlorotoluene
ChJorobenzene
Methanol
n-Propyl Alcohol
Acetone
Methyl ethyl ketone
Ethyl acetate
Ethyl ether
2-Butanone
Valeraldehyde
Hexanal
1-Butanol
Phenol
4-Methyl-2-pentanone
Bcnzalocbydc
p-ToIualdehyde
Acetophenone
1-Octanal
Isopborone
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TECHNICAL REPORT DATA
I, REPORT BO.
EPA/600/A-92/252
2.
*. TITLE AND SUBTITLE
5.REPORT DATE
Development of an Analysis Method for Total
Nonmethane Volatile Organic Carbon Emissions from
Stationary Sources
S.FERFORMIHG ORGANIZATION CODE
7. AUTOBUS)
e.PERFCKCHG ORGANIZATION REPORT HO.
Merrill Jackson, Joseph Knoll, Rodney MIdgett,
Samuel Foster, James McGaughey & Raymond Merrill
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Radian Corporation
P.O. Box 13000
Research Triangle Park, NC 27709
10.PROGRAM ELEMEHT BO.
11. COHTRACT/GRAKT HO.
68-D1-0010
12. SPONSORING AGENCY RAHE AND ADDRESS
US EPA
ORD, AREAL, MRDD, SMRB
Research Triangle Park, NC 27711
13.TYPE OF REPORT AND PERIOD COVERED
. SPONSORING AGEHCY CODE
15. SOTFLEHENTARY NOTES
16. ABSTRACT
The accurate measurement of the total nonmethane volatile organic carbon
emissions from stationary sources is critical to characterizing of many industrial
processes and for regulating according to the Clean Air Act. Current methods are
difficult to use and the ability to do performance audits has been marginal,
especially at low concentrations (50 parts per million of carbon, ppmc). One of
the key elements for an ideal measurement technique would be a detector that
responds to all classes of organic compounds equally, based on the number of carbon
atoms present. A commercially available catalytic flame ionization detector (CFID)
has shown promise in this area. Laboratory studies with a CFID were performed to
determine the response of compounds with various functional groups. These classes
included brominated, chlorinated, nitrogenated, oxygenated, aromatic, and non-
aromatic compounds. The response of each compound is compared to the response of
an alkane with the same number of carbon atoms. This paper will discuss this phase
of the experimental work. Future work with this detector will incorporate an
approach for sampling, sample recovery, and field tests for comparison to the EPA
Method 25.
17.
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Unclassified
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Unclassified*
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