THE ENVIRONMENTAL TECHNOLOGY VERIFICATION
PROGRAM
EPA
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The Business of Innovation
TECHNOLOGY TYPE: PARTICULATE METALS MONITOR
APPLICATION:
MONITORING OF METALS IN AEROSOL PARTICLES
IN AMBIENT AIR
TECHNOLOGY NAME: Xact 625
COMPANY:
ADDRESS:
WEB SITE:
E-MAIL:
Pall Corporation
Pall Membrane Technology Center PHONE: (850) 476-7974
8780 Ely Road
Pensacola, Florida 32514
http://www.pall.com/main/Home.page
Krag Peterson (Krag_Petterson@pall.com)
ETV Joint Verification Statement
The U.S. Environmental Protection Agency (EPA) has established the Environmental Technology Verification
(ETV) Program to facilitate the deployment of innovative or improved environmental technologies through
performance verification and dissemination of information. The goal of the ETV Program is to further
environmental protection by accelerating the acceptance and use of improved and cost-effective technologies.
ETV seeks to achieve this goal by providing high-quality, peer-reviewed data on technology performance to
those involved in the design, distribution, financing, permitting, purchase, and use of environmental
technologies. Information and ETV documents are available at www.epa.gov/etv.
ETV works in partnership with recognized standards and testing organizations, with stakeholder groups
(consisting of buyers, vendor organizations, and permitters), and with individual technology developers. The
program evaluates the performance of innovative technologies by developing test plans that are responsive to
the needs of stakeholders, conducting field and laboratory tests (as appropriate), collecting and analyzing data,
and preparing peer-reviewed reports. All evaluations are conducted in accordance with rigorous quality
assurance (QA) protocols to ensure that data of known and adequate quality are generated and that the results
are defensible.
The Advanced Monitoring Systems (AMS) Center, one of six verification centers under ETV, is operated by
Battelle in cooperation with EPA's National Risk Management Research Laboratory. The AMS Center
evaluated the performance of a field deployable X-ray fluorescence (XRF) analyzer for determining metals in
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particulate matter in ambient air. This verification statement provides a summary of the test results for Pall
Corporation's Xact 625 Particulate Metals Monitor.
VERIFICATION TEST DESCRIPTION
This verification evaluated the ability of the Xact 625 to provide reliable quantitative measurements of metals in
particulate matter having aerodynamic diameter less than 10 micrometers (i.e., PM10), during continuous
unattended operation. The verification was conducted over several weeks in the winter of 2011-2012 and
involved continuous operation of an Xact 625 unit at an existing ambient air monitoring site in Marietta, Ohio.
The verification was supported by EPA's Region 5 and Office of Air Quality Planning and Standards and was
carried out with the help of the Ohio Environmental Protection Agency. A total of 23 metals were reported
hourly by the Xact 625 over a field period of approximately 80 days. Daily averages of Xact 625 metals readings
that exceeded the daily quantitation limits (QLs) of the analyzer were compared to corresponding results
determined by EPA reference sampling and analysis by inductively coupled plasma mass spectrometry (ICP/MS).
Quantitative comparisons of Xact 625 results to reference results could be made for six metals [calcium (Ca),
copper (Cu), manganese (Mn), lead (Pb), selenium (Se), and zinc (Zn)], using reference measurements obtained
over approximately 65 days within the 80-day period of continuous Xact 625 operation.
The following are the parameters on which Xact 625 performance was evaluated:
Comparability - The comparability of Xact 625 results to reference results was determined for each metal by
examination of the slope and intercept of a linear regression of the data using the ICP/MS results as the
independent variable and the Xact 625 daily averages as the dependent variable.
Correlation - The degree of correlation between the Xact 625 results and the reference method results was
determined for each metal by the coefficient of determination (r2) of the linear regression between the
reference method results and the corresponding Xact 625 daily averages.
Bias - The bias of the Xact 625 readings was calculated as the percent difference of each daily average Xact
625 reading relative to the corresponding daily average reference method result.
Data Completeness - The completeness of Xact 625 data was calculated as the percentage of the field period
for which valid hourly data were reported, and as the percentage of all daily reference measurement periods
during which the Xact 625 reported at least 12 hours of monitoring data (i.e., produced data for at least half
of the reference monitoring period).
Operational Factors - Performance factors such as maintenance requirements, ease of use, and effectiveness
of data acquisition were assessed from observations by EPA and Ohio EPA staff.
Battelle and EPA QA staff conducted separate technical systems audits (TSAs) of the field operations, and
Battelle QA staff conducted a TSA of the reference analysis laboratory and a data quality audit of the test data.
This verification statement, the full report on which it is based, and the test/QA plan for this verification are
available at www.epa.gov/etv/centers/centerl.html.
TECHNOLOGY DESCRIPTION
The following description of the Xact 625 is based on information provided by the vendor and was not verified in
this evaluation: The Xact 625 determines metals in airborne PM10 by XRF, in which X-rays from a source cause
ejection of an electron from an inner electronic shell of a metal atom in a sample. The vacancy in the inner shell
is filled by an electron from an outer shell, with resulting emission of an X-ray of wavelength longer than that of
the original excitation and characteristic of the metal in question. The Xact 625 uses energy-dispersive XRF
(EDXRF) and a low power X-ray source. EDXRF provides rapid acquisition of the entire X-ray spectrum so that
many elements can be detected within a few seconds. To monitor metals in atmospheric PMi0, the Xact 625 uses
an automated moveable filter tape, in which sample air is drawn through a small spot on the tape, collecting and
concentrating PM10 onto that spot. The tape then advances, placing the collected sample spot in the X-ray
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excitation and analysis section of the monitor and initiating participate sampling onto a previously unexposed spot
on the tape. The sequence of sampling and analysis can continue automatically, limited only by the supply of
filter tape. The duration of sample collection at each spot can be set at a constant interval, or varied to maintain
detection performance when atmospheric PM10 levels vary. The Xact 625 samples ambient air at a constant flow
rate of 16.7 L/min (i.e., 1 m3/hr). The Xact 625's sample inlet is designed to provide uniform sample deposition,
and the instrument analyzes approximately 90% of the sample spot area to minimize effects of sample
inhomogeneity. The Xact 625 incorporates sensors for temperature and atmospheric pressure, and uses those data
to maintain a constant volumetric sample flow and consequently an accurate PM10 inlet size cut. For this
verification the vendor of the Xact 625 programmed the monitor to perform the following automatic internal
quality control (QC) checks on a daily basis to assure data quality:
• Internal energy alignment check, by XRF analysis of a Cu rod, conducted over a 15-minute period starting at
midnight each day,
• Upscale rod check, by XRF analysis of a metal rod containing chromium (Cr), Pb, and cadmium (Cd),
conducted once per day over a 15-minute period,
• Flow check, conducted at the same time as the upscale rod check, to determine the Xact 625 sample air flow
by insertion of a second mass flow meter into the flow path,
• Palladium rod stability check by XRF analysis of a palladium rod in every ambient sample analysis.
VERIFICATION RESULTS
Of the 23 ambient PMio metals determined by the Xact 625 in this verification, 19 were also determined
by the ICP/MS analysis of reference samples. Of those 19 metals, Xact 625 results for 12 metals were
almost always below the respective QLs of the Xact 625, and consequently no comparisons could be
made to the reference results. Also the Xact 625 reported a nearly constant and unrealistic ambient
concentration of molybdenum due to an incorrect energy window for that metal in the XRF analysis.
The vendor of the Xact 625 indicates that this problem can be avoided in the future by narrowing the
energy window. Table VS-1 presents a summary of the quantitative performance results of the Xact 625
for the remaining six metals, showing the performance parameters and resulting performance metrics.
Table VS-1 indicates that the daily average Xact 625 results were highly correlated and in close
quantitative agreement with ICP/MS analysis results for most of the six metals, and that the Xact 625
achieved data completeness of over 95%. The regression results for Cu reflect the fact that the ambient
Cu concentrations were often near the detection limit of the ICP/MS analysis and the QL of the Xact
625. In addition, investigations conducted after the verification test suggest that the regression results
for Cu and the relatively high bias results for Pb may both have been affected by the background levels
of these metals in the Xact 625's blank filter tape.
The Xact 625 required minimal operator attention during testing, with routine maintenance consisting of
changing the sampling tape approximately every 2 weeks. The analyzer conducted several automated
internal QC checks on a daily basis, and provided readily understandable data files that distinguished
QC from ambient monitoring results and included analyzer flow and internal readings. The internal QC
check results of the Xact 625 showed that the relative standard deviation of the palladium internal
standard readings determined in every Xact 625 analysis was 2.0%, and the instrument's average flow
error was -0.69% (± 0.004%) where the number in parentheses is the standard deviation of the daily
flow check results. The average accuracy relative to upscale rod check standards analyzed daily was
100.2% (± 0.004%) for Cr, 100.6% (± 0.013%) for Cd, and 99.8% (± 0.007%) for Pb, where accuracy of
100% indicates perfect agreement with the upscale rod check standard. However, the test results for Cu
and Pb strongly indicate that analysis of blank portions of the filter tape should be a component of the
Xact 625's automated internal QC checks.
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Table VS-1. Quantitative Performance Results for the Xact 625
Performance
Parameter
Comparability
Correlation
Bias
Data Completeness
Metal
Ca
Cu
Mn
Pb
Se
Zn
Ca
Cu
Mn
Pb
Se
Zn
Ca
Cu
Mn
Pb
Se
Zn
All
Metric
Slope
(± 95% CI)
0.82 (± 0.04)
0.30 (±0.17)
1.0 (±0.01)
1.1 (±0.07)
0.99 (±0.11)
0.97 (± 0.03)
Intercept
(± 95% CI)
(ng/m3)
-30.6 (± 11.9)
2.1 (±0.65)
-0.09 (±2. 13)
1.6 (±0.30)
0.01 (±0.22)
-3.0 (±0.98)
Coefficient of Determination
(r2)
0.979
0.341
0.999
0.943
0.926
0.988
Mean (± SD)
(%)
-3 1.3 (±9.5)
-5.6 (±22.1)
1.1 (±21.8)
74.8 (± 54.3)
-0.70 (±8.1)
-20.5 (± 15.4)
Hourly Data (%)
95.4 to 96.0
Median
(%)
-31.0
1.2
-0.60
61.9
-1.3
-17.9
Daily Averages
with > 12 Hours
(%)
96.9
CI = Confidence interval; SD = Standard deviation
Signed by Tracy Stenner
10/10/12
Date
Tracy Stenner
Manager
Environmental Solutions Product Line
Energy, Environment, and Materials Sciences
Battelle
Signed by Cynthia Sonich-Mullin
10/31/12
Date
Cynthia Sonich-Mullin
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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