EPA/600/R-14/308S
February 2014
THE ENVIRONMENTAL TECHNOLOGY VERIFICATION
PROGRAM
Al PA FT\y Baltelle
* JL*l JL \S The Business
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sampling intervals throughout the testing period, from approximately 7:00 am to 7:00 pm and from approximately
7:00 pm to 7:00 am daily. The reference samples were collected and analyzed by Desert Research Institute for
organic carbon (OC) and elemental carbon (EC) using the Interagancy Monitoring of PROtected Visual
Environments (IMPROVE) thermal/optical reflectance (TOR) and thermal/optical transmittance (TOT) protocols.
Note that in this report the filter samples will be referred to as "reference samples". However, it should be noted
that the IMPROVE method is not a true Reference Method in that it is not recognized as an absolute standard.
Nonetheless, it is used within the IMPROVE network as the standard method for EC analysis. Thus the method
was used in this test as an analytical technique used for comparison to the BC monitors. Other thermal/optical
reference methods such as the NIOSH 5040 method may result in different results. The comparability and
correlation of the monitoring technology was determined through comparisons to the collocated reference method
samples. The precision of the Model 4 analyzers was determined from comparisons of paired data from the
duplicate units (identified as "RT3218" and "RT3219". Other performance parameters such as data
completeness, maintenance requirements, ease of use, and consumable use were assessed from observations by
the Battelle field testing staff. This test was not intended to simulate long-term performance of anlayzers at a
monitoring site.
QA oversight of verification testing was provided by Battelle and EPA. Battelle technical staff conducted a
performance evaluation audit, and Battelle QA staff conducted a technical systems audit and a data quality audit
of 10% of the test data. This verification statement, the full report on which it is based, and the test/QA plan for
this verification test are all available at www.epa.gov/etv/centers/centerl.html.
TECHNOLOGY DESCRIPTION
The following description of the Model 4 anlayzer is based on information provided by the vendor. This
technology description was not verified in this test.
Sunset Laboratory's semi-continuous Model 4 OC-EC Field Analyzer has been developed as a field deployable
alternative to integrated filter collection with subsequent laboratory analysis. This instrument can provide time-
resolved analyses of OC and EC in airborne particulate matter (PM) on a semi-continuous basis, with OC-EC
results comparable to the recognized NIOSH Method 5040 and other thermal optical carbon aerosol methods
currently in use. As currently performed, a quartz filter disc is mounted in the oven within the instrument, and
samples are collected for the desired time period. Once the collection is complete, the oven is purged with
helium, and a stepped-temperature ramp increases the oven temperature to 850 °C, thermally desorbing organic
compounds and pyrolysis products into a manganese dioxide (MnO2) oxidizing oven. As the carbon fragments
flow through the MnO2 oven, they are quantitatively converted to carbon dioxide (CO2) gas. The CO2 is swept
out of the oxidizing oven with the helium stream and measured directly by a self-contained non-dispersive
infrared (NDIR) detector system. A second temperature ramp is then initiated in an oxidizing gas stream and
any elemental carbon is oxidized off the filter and into the oxidizing oven and NDIR. The EC is then detected
in the same manner as the OC.
The Sunset Laboratory thermal/optical method uses the high light absorbance characteristic of EC to correct for
the pyrolysis-induced error. This is done by incorporating a tuned diode laser (red, 660 nm), focused through
the sample chamber such that the laser beam passes through the mounted filter in the sample oven. Initial
absorbance of the modulated laser beam is recorded. As the oven ramp proceeds, the laser absorbance is
monitored continuously by the data system. Any charring of the OC results in an increase in absorbance of the
laser. After the initial temperature ramp, when the helium purge is switched to a He/O2 mixture, all of the EC is
oxidized off and the laser absorbance is reduced to the background level. When the resulting NDIR data are
reviewed with an overlay of the laser absorbance, the point in the second phase oxidizing ramp at which the
laser absorbance equals the initial laser absorbance is the split point. Any EC detected, before this point, was
formed pyrolytically by charring of the OC. This carbon is subtracted from the EC area observed during the
oxidizing phase of the analysis and is assigned as OC. The primary assumption, for this correction, is that the
particulate bound EC and the pyrolytically formed EC have the same absorption coefficient. Carefully prepared
standard samples suggest that this correction is satisfactory.
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VERIFICATION RESULTS (An unexplained anomaly in the signal of one of the duplicate Model 4
analyzers was discovered during data processing. Results presented here include both uncorrected and
corrected values.)
Comparability-
Regression analysis
comparison to
reference samples
Analyzer/Mode
RT3218 Thermal
RT3219 Thermal
RT3219 Corrected
Thermal
RT3218 Optical
RT3219 Optical
TOR
Slope
0.797 (0.044)
0.903 (0.063)
0.819(0.043)
0.656 (0.034)
0.701 (0.034)
Intercept
0.280 (0.028)
0.346 (0.040)
0.290 (0.027)
0.134(0.021)
0.140(0.022)
TOT
Slope
1.057(0.053)
1.215(0.073)
1.080(0.053)
0.874 (0.036)
0.934(0.038)
Intercept
0.293 (0.025)
0.355 (0.035)
0.306 (0.025)
0.143 (0.017)
0.150(0.018)
Analyzer/Mode
RPDa
Comparability- Calculation of Relative
Percent Difference (RPD) between
Model 4 OC-EC results and reference
method results
TOR
RT3218 Thermal
RT3219 Thermal
66.2%
RT3219 Corrected Thermal
45.7%
RT3218 Optical
-3.7%
RT3219 Optical
2.1%
TOT
80.6%
101.4%
77.6%
23.6%
31.2%
Analyzer/Mode
TOR
Correlation - Regression analysis
comparison to reference samples
RT3218 Thermal
0.854
RT3219 Thermal
0.783
RT3219 Corrected Thermal
0.865
RT3218 Optical
0.878
RT3219 Optical
0.882
TOT
0.876
0.827
0.878
0.910
0.914
Precision - Comparison of
results from duplicate
monitoring systems
Uncorrected
Corrected
RPD (# of Observations)
Thermal
2-hour
19
(N=
9%
168)
12
(N=
4%
157)
12-hour
14.3%
(N=38)
9.7%
(N=36)
Optical
2-hour
(N=91)
12-hour
6.3%
(N=16)
Mode
Precision - Regression
analysis of results from
duplicate monitoring
systems
Thermal
Uncorrected
Thermal
Corrected
Optical
Period
2-hour
12-hour
2-hour
12-hour
2-hour
12-hour
Slope
1.075 (0.021)
1.104(0.055)
1.000(0.016)
0.980 (0.036)
1.057(0.002)
1.065(0.004)
Intercept
0.064 (0.017)
0.044 (O.Q40)
0.024(0.013)
0.035 (0.027)
0.002(0.001)
-0.001 (0.002)
0.880
0.872
0.912
0.925
0.999
0.999
Analyzer
Period
Data Completeness
RT3218
RT3219
2-hour
12-hour
2-hour
12-hour
Total Periods
Valid
Measurements
%
Complete
378
372
98%
63
378
63
62
372
62
98%
98%
98%
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VERIFICATION RESULTS (Cont.)
Maintenance
Consum ables/waste
generated
Ease of use
• Routine maintenance consisted of replacing filters approximately weekly.
• Three different compressed gas cylinders required to operate the units
• Internal filters replaced weekly.
• Installation of two Model 4 units with inlets completed in ~4 hours.
• Calibration of units completed in -3-4 hours, after allowing the units to operate
overnight.
• Routine operation required no effort other than brief daily instrument checks
and approximately weekly data downloads.
• Data processed using vendor software to generate csv data files.
For these calculations, reference method results below twice the method detection limit were excluded. For perfect agreement
between the Model 4 analyzers and the reference method results, the RPD would be zero. In general, the measured concentrations
from the Model 4 analyzers were higher than those from the reference method resulting in positive RPD values. It should be
noted that only about two thirds of the TOR reference method results and fewer than half the TOT reference method results were
above twice the detection limit.
Signed by Spencer Pugh
Spencer Pugh
General Manager
Energy & Environment Business Unit
Energy, Health & Environment
Battelle
4/17/14 Signed by Cynthia Sonich-Mullin 5/7/14
Date Cynthia Sonich-Mullin Date
Director
National Risk Management Research Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
NOTICE: ETV verifications are based on an evaluation of technology performance under specific,
predetermined criteria and the appropriate quality assurance procedures. EPA and Battelle make no expressed or
implied warranties as to the performance of the technology and do not certify that a technology will always
operate as verified. The end user is solely responsible for complying with any and all applicable federal, state,
and local requirements. Mention of commercial product names does not imply endorsement.
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