United States Office of Research and EPA/600/R-03/087
Environmental Protection Development September 2003
Agency Washington, D.C. 20460
&EPA Environmental Technology
Verification Report
Lead in Dust Wipe Measurement
Technology
NITON LLC
X-Ray Fluorescence Spectrum
Analyzer, XLt 700 Series
onvl
Oak Ridge National Laboratory
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THE ENVIRONMENTAL TECHNOLOGY VERIFICATION
PROGRAM
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Oak Ridge National Laboratory
Verification Statement
TECHNOLOGY TYPE:
APPLICATION:
TECHNOLOGY NAME:
COMPANY:
ADDRESS:
WEB SITE:
E-MAIL:
X-RAY FLUORESCENCE
MEASUREMENT OF LEAD IN DUST WIPES
XLt 700 Series XRF Spectrum Analyzer
NITON LLC
900 Middlesex Turnpike, Bldg. 8 PHONE: +1(978) 670-7460
Billerica, MA 01821 FAX: +1(978) 670-7430
www.niton.com
sales(S)Tiiton.com
The U.S. Environmental Protection Agency (EPA) has created the Environmental Technology
Verification Program (ETV) 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 substantially 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.
ETV works in partnership with recognized standards and testing organizations and stakeholder groups
consisting of regulators, buyers, and vendor organizations, with the full participation of 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 or laboratory tests (as
appropriate), collecting and analyzing data, and preparing peer-reviewed reports. All evaluations are
conducted in accordance with rigorous quality assurance protocols to ensure that data of known and
adequate quality are generated and that the results are defensible.
Oak Ridge National Laboratory (ORNL) is one of the verification organizations operating under the
Advanced Monitoring Systems (AMS) Center. AMS, which is administered by EPA's National Exposure
Research Laboratory (NERL), is one of seven technology areas under ETV. In this verification test,
ORNL evaluated the performance of lead in a dust wipe measurement technology. This verification
statement provides a summary of the test results for NITON's XLt 700 Series x-ray fluorescence (XRF)
spectrum analyzer.
EPA-VS-SCM-55
The accompanying notice is an integral part of this verification statement.
September 2003
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VERIFICATION TEST DESCRIPTION
This verification test was designed to evaluate technologies that detect and measure lead in dust wipes.
The test was conducted at the EPA Region 1 Laboratories in North Chelmsford, MA, from January 6
through January 9, 2003. This ETV performance test was an extension of those conducted in 2001 and
2002 using the same experimental design. The vendor of this commercially-available, field portable
technology blindly analyzed 160 dust wipe samples containing known amounts of lead, ranging in
concentration from <2 to 1,500 |j,g/wipe. The experimental design was particularly focused on important
clearance standards, such as those identified in 40 CFR Part 745.227(e)(8)(viii) of 40 |ig/ft2 for floors,
250 |J.g/ft2 for window sills, and 400 |ig/ft2 for window troughs. The samples analyzed in this verification
test were archived from the original test in 2001. The test included samples from the Environmental Lead
Proficiency Analytical Testing Program (ELPAT), which were prepared from dust collected in
households in North Carolina and Wisconsin. Also, samples were acquired from the University of
Cincinnati (UC). The UC dust wipe samples were prepared from National Institute of Standards and
Technology (NIST) Standard Reference Materials (SRMs). The integrity of the archived samples was
confirmed by independent analysis prior to the tests described here. The results of the lead analyses
generated by the technology were compared with results from analyses of similar samples by
conventional laboratory methodology in a laboratory that was recognized as proficient by the National
Lead Laboratory Accreditation Program (NLLAP) for dust testing. Quality assurance (QA) oversight of
verification testing was provided by ORNL and EPA. EPA and ORNL QA staff reviewed and approved
the test plan. ORNL staff conducted a data quality audit of 100% of the test data (both laboratory and
vendor), and a technical systems audit of the procedures used during this verification. In addition, ORNL
QA staff also conducted an independent technical systems audit at the test site. Details of the test,
including a data summary and discussion of results, may be found in the report entitled Environmental
Technology Verification Report: Lead in Dust Wipe Detection Technology— NITONLLC, XLt 700 Series
X-Ray Fluorescence Spectrum Analyzer, EPA/600/R-03/087.
TECHNOLOGY DESCRIPTION
The following description of the XLt 700 was provided in part by the vendor (NITON) and does not
represent verified information.
The XLt 700 analyzer is an energy dispersive x-ray fluorescence (EDXRF) spectrometer that uses a low
power miniature x-ray tube with a silver transmission target to excite characteristic x-rays of a test sample's
constituent elements. These characteristic x-rays are continuously detected, identified, and quantified by
the spectrometer during sample analysis. The energy of each x-ray detected identifies a particular element
present in the sample. The rate at which x-rays of a given energy are counted provides a determination of
the quantity of that element that is present in the sample. Detection of the characteristic lead x-rays is
achieved using a highly-efficient, thermo-electrically cooled, solid-state detector. Signals from the detector
are amplified, digitized, and then quantified via integral multichannel analysis and data processing units.
Sample test results are displayed in total micrograms of lead per dust-wipe. NITON's XLt 700 Series XRF
spectrum analyzer reporting limit was 10 [ig/wipe during the verification test.
VERIFICATION OF PERFORMANCE
The following performance characteristics of the XLt 700 Series XRF were observed:
Precision: Precision—based on the average percent relative standard deviation—was 11% for the UC
samples and was 11% for the ELPAT samples.
EPA-VS-SCM-55 The accompanying notice is an integral part of this verification statement. September 2003
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Accuracy: Accuracy was assessed using the estimated concentrations of the UC and ELPAT samples. The
average percent recovery value for all samples reported above the upper bound of the reporting limits
observed in this evaluation was 97% for the UC samples and 101% for the ELPAT samples. A regression
line fitted to the XLt 700 results versus the estimated concentrations showed slopes with slightly low
biases that were statistically significant for both the UC and ELPAT samples. However, the average
percent recovery values were well within the acceptable bias range of 100% ± 25%. In contrast, for
results from the NLLAP laboratory-based analysis of these same samples, the average percent recovery
values were 91% and 98%, respectively, for the UC and ELPAT samples. The regression analyses also
exhibited slopes that were negative biases for both the UC and ELPAT samples and were statistically
significant.
Comparability: A comparison of all samples (ELPAT and UC) was performed for cases where both the
XLt 700 and the NLLAP-recognized laboratory results were above 20 |j,g/wipe (the reporting limit for the
laboratory) . The correlation coefficient (r) for the comparison of the UC samples was 0.999 [slope (m) =
0.995, intercept = 4.775], and for the ELPAT samples was also 0.999 [m = 0.977, intercept = 3.076].
Although the slope for the ELPAT samples (but not UC samples) was statistically different than 1.00,
both sample sets have correlation coefficients that show a strong linear agreement with the NLLAP
laboratory data.
Detectable blanks: All twenty blank samples, prepared at concentrations < 2 |J,g/wipe, were reported
correctly as less than reporting limits, with results reported by the XLt 700 as less than 10 |j,g/wipe.
False positive results: A false positive (fp) result is one in which the technology reports a result that is
above the clearance level when the true (or estimated) concentration is actually below. For the UC
samples, the XLt 700 reported 8 of a possible 37 fp results, while the NLLAP laboratory did not report
any fp results. For the ELPAT samples, the XLt 700 reported 1 of a possible 12 fp results, while the
NLLAP laboratory reported 2 of 12 fp results.
False negative results: A false negative (fn) result is one in which the technology reports a result that is
below the clearance level when the true (or estimated) concentration is actually above. For the UC
samples, the XLt 700 reported 10 of a possible 23 m results, while the NLLAP laboratory reported 23 of
a possible 30 fn results. For the ELPAT samples, the XLt 700 reported 8 of a possible 28 m results, while
the NLLAP laboratory reported 7 of 28 fn results.
Completeness: The XLt 700 Series spectrum analyzer generated results for all 160 dust wipes samples,
for a completeness of 100%.
Sample Throughput: Two analysts (NITON experts) analyzed all 160 samples in 32.75 hours over 3.5
calendar days. Eight measurements were taken for sample wipe, unless the vendor, based on an initial
evaluation of a non-detectable instrument response, believed the test sample to be a blank. In such cases,
the vendor performed four measurements on those samples, for a total of 1200 measurements.
EPA-VS-SCM-55 The accompanying notice is an integral part of this verification statement. September 2003
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Overall Evaluation: The overall performance was characterized as being biased slightly low (but within
the limits of acceptable bias), precise, and in good linear agreement to an NLLAP-laboratory results. The
verification team found that the XLt 700 was relatively simple for the trained analyst to operate in the
field, requiring less than an hour for initial setup. As with any technology selection, the user must
determine if this technology is appropriate for the application and the project data quality objectives.
Additionally, ORNL and ETV remind the reader that, while the ETV test provides valuable information
in the form of a snapshot of performance, state, tribal, or federal requirements regarding the use of the
technologies (such as NLLAP recognition for analysis of samples where required) need to be followed.
For more information on this and other verified technologies, visit the ETV web site at
http: //www. epa. gov/etv.
Gary J. Foley, Ph.D.
Director
National Exposure Research Laboratory
Office of Research and Development
W. Franklin Harris, Ph.D.
Associate Laboratory Director
Biological and Environmental Sciences
Oak Ridge National Laboratory
NOTICE: ETV verifications are based on evaluations of technology performance under specific, predetermined criteria and appropriate
quality assurance procedures. EPA and ORNL 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 or
recommendation.
EPA-VS-SCM-55
The accompanying notice is an integral part of this verification statement.
September 2003
-------
EPA/600/R-03/087
September 2003
Environmental Technology
Verification Report
Lead in Dust Wipe Measurement
Technology
NITON LLC
X-Ray Fluorescence Spectrum
Analyzer, XLt 700 Series
By
Charles K. Bayne, Ph.D.
Roger A. Jenkins, Ph.D.
Oak Ridge National Laboratory
Oak Ridge, Tennessee 37831-6120
Eric N. Koglin
U.S. Environmental Protection Agency
Environmental Sciences Division
National Exposure Research Laboratory
Las Vegas, Nevada 89193-3478
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Notice
This work was funded by the U.S. Environmental Protection Agency's (EPA) Office of Research and
Development (ORD), through a contract with Battelle Memorial Institute and EPA's OPPT contract with
Battelle under contract number 68-W-99-033. Battelle funded and managed the work performed at Oak
Ridge National Laboratory through contract ERD-97-XN035. This report has been peer and administratively
reviewed and has been approved for publication as an EPA document. Mention of trade names or commercial
products does not constitute endorsement or recommendation for use of a specific product.
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Table of Contents
Notice ii
List of Figures v
List of Tables vi
Acknowledgments vii
Abbreviations and Acronyms viii
Section 1 — Introduction 1
Section 2 — Technology Description 2
General Technology Description 2
Sample Preparation 2
Calibration 3
Sample Analysis 3
Section 3 — Verification Test Design 4
Objective 4
Testing Location and Conditions 4
Drivers and Objectives for the Test 4
Summary of the Experimental Design 4
ELPAT and Blank Sample Description 4
University of Cincinnati Sample Description 5
Distribution and Number of Samples 6
Sample Randomization 6
Description of Performance Factors 6
Precision 6
Accuracy 7
Comparability 8
Detectable Blanks 8
False Positive/Negative Results 8
Completeness 9
Sample Throughput 9
Ease of Use 9
Cost 9
Miscellaneous Factors 9
Section 4 — Laboratory Analyses 10
Background 10
NLLAP Laboratory Selection 10
Laboratory Method 10
Laboratory Performance 11
Section 5 — Technology Evaluation 17
Objective and Approach 17
Precision 17
Accuracy 17
hi
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Comparability 18
Detectable Blanks 18
False Positive/False Negative Results 19
Completeness 22
Sample Throughput 22
Ease of Use 22
Cost Assessment 22
XLt 700 Series XRF Costs 23
Labor 23
Equipment 23
Laboratory Costs 24
Sample Shipment 24
Labor, Equipment, and Waste Disposal 24
Cost Assessment Summary 24
Miscellaneous Factors 24
Summary of Performance 25
Section 6 — References 27
Appendix 28
IV
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List of Figures
1. NITON XLt 700 series XRF spectrum analyzer and optional notebook computer 2
2. Schematic diagram of recommended folding procedure for dust wipes 3
3. Distribution of both UC and ELPAT sample concentrations 7
4. Plot of DataChem reported values versus estimated values, shown for concentrations less than 500
[ig/wipe 12
5. False negative probabilities for DataChem average concentrations at a target concentration level of 40
[ig/wipe 14
6. False negative probabilities for DataChem average concentrations at a target concentration level of
250 |j,g/wipe 15
7. False negative probabilities for DataChem average concentrations at a target concentration level of
400 [ig/wipe 15
8. Plot of the average XLt 700 concentration versus the average DataChem concentrations for all samples
shown for ELPAT and UC concentrations less than 500 [ig/wipe 19
9. Comparison of the false negative probabilities for the NITON XLt 700 and DataChem average
concentrations at a target concentration level of 40 |j,g/wipe 20
10. Comparison of the false negative probabilities for the NITON XLt 700 and DataChem average
concentrations at a target concentration level of 250 |j,g/wipe 21
11. Comparison of the false negative probabilities for the NITON XLt 700 and DataChem average
concentrations at a target concentration level of 400 |j,g/wipe 21
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List of Tables
1. Summary of DataChem Pre-Test Results 11
2. Summary of DataChem Percent Recovery Values by Sample Source 12
3. Summary of DataChem Precision Estimates by Sample Source 12
4. False Positive/False Negative Results for DataChem Measurements of UC Samples 14
5. Summary of the Linear Regression Constants and Recovery Data for DataChem's Measurements
Versus the Estimated Concentrations at the Clearance Levels 16
6. Precision of the XLt 700 17
7. Accuracy of XLt 700 17
8. Linear regression constants for the plots of the XLt 700 versus the estimated values and versus the
DataChem average measurements 18
9. False Positive/False Negative Error Rates for XLt 700 Measurements 20
10. Summary of the Linear Regression and Recovery Data for the XLt 700 Response versus the
Estimated Concentrations 22
11. Estimated analytical costs for lead dust wipe samples 23
12. Performance Summary for NITON's XLt 700 Series XRF Spectrum Analyzer 26
VI
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Acknowledgments
The authors wish to acknowledge the support of all those who helped plan and conduct the verification test,
analyze the data, and prepare this report. In particular, we recognize: Paul Carroll (EPA/Region 1), for
providing a site for the verification test; Sandy Roda (University of Cincinnati) and Laura Hodson (Research
Triangle Institute) for coordination of sample preparation; the inorganic analytical laboratory in EPA/Region
1 (North Chelmsford, MA) for the analysis of quality control samples; and the expertise of the technical
advisory panel, including Kenn White (American Industrial Hygiene Association), John Schwemberger, Dan
Reinhart, Oksana Pozda, and Darlene Watford (EPA/Office of Pollution Prevention and Toxics), Paul Carroll
(EPA/Region 1), Sharon Harper (EPA/Research Triangle Park), Peter Ashley, Warren Friedman, Gene
Pinzer, and Emily Williams (U.S. Department of Housing and Urban Development); Paul Halfmann and
Sharon Cameron (Massachusetts Childhood Lead Poisoning Prevention Program), Kevin Ashley (National
Institute for Occupational Safety and Health); Walt Rossiter and Mary McKnight (National Institute of
Standards & Technology); Bill Gutknecht (Research Triangle Institute), and Bruce Buxton (Battelle Memorial
Institute). The authors would specifically like to thank Paul Halfmann and Richard Baker for serving as peer
reviewers and John Schwemberger as Work Assignment Manager for their careful reading of this report. The
authors also acknowledge the participation of NITON LLC, in particular, Dave Mercuro, Debbie Schatzlein,
and Jon Shein.
For more information on the Lead in Dust Wipe Measurement Technology Verification contact:
Eric N. Koglin Roger A. Jenkins
Project Technical Leader Program Manager
Environmental Protection Agency Oak Ridge National Laboratory
National Homeland Security Chemical Sciences Division
Research Center P.O. Box 2008
P.O. Box 93478 Oak Ridge, TN 37831-6120
Las Vegas, Nevada 89193-3478 (865) 574-4871
(702) 798-2332 ienkinsra@,ornl.gov
koglin.eric@epa.gov
For more information on NITON's XLt 700 Series XRF Spectrum Analyzer, contact:
Jonathan J. Shein
NITON LLC
900 Middlesex Turnpike, Building 8
Billerica, MA01821
+1(978)670-7460
sales@niton.com
www.niton.com
vn
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Abbreviations and Acronyms
AIHA American Industrial Hygiene Association
AMT Advanced Monitoring Technology Center, ETV
ASTM American Society for Testing and Materials
CDC Centers for Disease Control and Prevention
CL Clearance level for lead of 40, 250, or 400 jig/wipe
EDXRF energy dispersive x-ray fluorescence
ELPAT Environmental Lead Proficiency Analytical Testing program
EPA U. S. Environmental Protection Agency
ETV Environmental Technology Verification Program
ETVR Environmental Technology Verification Report
fn false negative result
fp false positive result
ICP-AES Inductively coupled plasma-atomic emission spectrometry
NIOSH National Institute for Occupational Safety and Health, CDC
NIST National Institute of Standards & Technology
NLLAP National Lead Laboratory Accreditation Program, U.S. EPA
OPPT Office of Pollution Prevention and Toxics, U.S. EPA
ORNL Oak Ridge National Laboratory
QA quality assurance
QC quality control
RSD relative standard deviation
RTI Research Triangle Institute
SRM Standard Reference Material
UC University of Cincinnati
XRF x-ray fluorescence spectrum analyzer
Vlll
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Section 1 — Introduction
The U.S. Environmental Protection Agency (EPA)
created the Environmental Technology Verification
Program (ETV) 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 substantially
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.
ETV works in partnership with recognized standards
and testing organizations and stakeholder groups
consisting of regulators, buyers, and vendor
organizations, with the full participation of
individual technology developers. The program
evaluates the performance of innovative
technologies by developing verification test plans
that are responsive to the needs of stakeholders,
conducting field or 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.
ETV is a voluntary program that seeks to provide
objective performance information to all of the
participants in the environmental marketplace and to
assist them in making informed technology
decisions. ETV does not rank technologies or
compare their performance, label or list technologies
as acceptable or unacceptable, seek to determine
"best available technology," or approve or
disapprove technologies. The program does not
evaluate technologies at the bench or pilot scale and
does not conduct or support research. Rather, it
conducts and reports on testing designed to describe
the performance of technologies under a range of
environmental conditions and matrices.
The program now operates six centers covering a
broad range of environmental areas. ETV began with
a 5-year pilot phase (1995-2000) to test a wide
range of partner and procedural alternatives in
various technology areas, as well as the true market
demand for and response to such a program. In these
centers, EPA utilizes the expertise of partner
"verification organizations" to design efficient
processes for conducting performance tests of
innovative technologies. These expert partners are
both public and private organizations, including
federal laboratories, states, industry consortia, and
private sector entities. Verification organizations
oversee and report verification activities based on
testing and QA protocols developed with input from
all major stakeholder/customer groups associated
with the technology area. The verification described
in this report was administered by the Advanced
Monitoring Systems (AMS) Center, with Oak Ridge
National Laboratory (ORNL) serving as the
verification organization. (To learn more about ETV,
visit ETV's Web site at http://www.epa.gov/etv.)
The AMS Center is administered by EPA's National
Exposure Research Laboratory (NERL).
The verification of a field analytical technology for
measurement of lead in dust wipe samples is
described in this report. The verification test was
conducted in North Chelmsford, MA, from January
6 through January 9, 2003. The performance of
NITON's XLt 700 Series X-Ray Fluorescence
(XRF) spectrum analyzer was determined under
field conditions. The technology was evaluated by
comparing its results to estimated concentration
values and with results obtained on similar samples
using a recognized laboratory analytical method.
The performances of NITON's XL-700 and XL-300
Series XRFs have been reported in separate
verification reports.
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Section 2 — Technology Description
In this section, the vendor (with minimal editorial changes by ORNL) provides a description of the technology
and the analytical procedure used during the verification testing activities.
General Technology Description
In Figure 1 is portrayed the XLt 700 Series
analyzer and supporting notebook computer. The
sample analyzer is an energy dispersive x-ray
fluorescence (EDXRF) spectrometer that uses a
low power miniature x-ray tube with a silver
transmission window to excite characteristic x-
rays of a test sample's constituent elements. These
characteristic x-rays are continuously detected,
identified, and quantified by the spectrometer
Figure 1. NITON XLt 700 series XRF spectrum
analyser with optional notebook computer.
during sample analysis. The energy of each x-ray
detected identifies a particular element present in
the sample. The rate at which x-rays of a given
energy are counted provides a determination of the
quantity of that element that is present in the
sample.
Note that the XLt 700 series instrument employs
an x-ray tube source for x-ray generation, rather
than a radioactive isotopic source. Each one of
these approaches has its strengths and limitations.
For example, tube-based x-ray sources offer a)
potentially faster analysis (x-ray flux can be higher
than most isotope based sources), b) can be used
over a wider range of excitation energies,
eliminating the need for multiple isotopic sources
to produce x-rays over the entire excitation
spectrum, c) no drop off in excitation power with
the age of the tube, and d) fewer requirements for
transporting sources outside the State in which the
source is licensed. However, tube based sources
are somewhat less rugged than isotopic sources,
and tend to be slightly larger and heavier. In
addition, they typically require more external or
battery power. Most isotopic x-ray sources tend to
have a diminishing flux output over their lifetime,
which requires longer counting times for analysis.
Detection of the characteristic lead x-rays is
achieved using a highly-efficient, thermo-
electrically cooled, solid-state detector. Signals
from the detector are amplified, digitized, and then
quantified via integral multichannel analysis and
data processing units. Sample test results are
displayed in total micrograms of lead per dust
wipe.
Sample Preparation
The following is the procedure that was used to
prepare the samples for analysis during the
verification test.
The dust wipe samples were unfolded and the dust
samples were distributed across the surface of the
wipe using a spatula or equivalent tool. The tool
was cleaned in between each sample preparation
by wiping with a damp paper towel. Next, the
sample was folded five times, as specified in the
schematic in Figure 2, such that it was neatly
folded to the proper size (1 x 1.5 inches).
The sample was dried prior to testing, because the
addition of this step has been found to improve the
accuracy and precision of dust wipe
measurements. Typically, moisture will reduce the
readings on the instrument, i.e., elements will read
lower than the actual value. In addition, the
presence of water has the effect of scattering more
of the x-rays (Compton scatter). The detection
limit will become slightly worse as the
background increases. As the moisture content
varies from wipe to wipe, it is not possible to
assume that the "offset" is the same for all
samples, so drying provides a practical alternative.
In this case, the sample was dried for 20 minutes at
250° F. in a toaster oven, and then allowed to cool
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at ambient conditions for 5 minutes prior to
measurement. (The vendor states that, if
accelerated drying is not practical, allowing the
re-folded wipe to stand at ambient temperature and
relative humidity overnight should result in an
adequately dried wipe.)
After drying, the wipe sample was placed in a 1.5
x 2 inch, 1.5 mil thick plastic bag (NITON part
number 187-471 or equivalent) and labeled. A
fresh bag was used for each sample to eliminate
the potential for cross-contamination of samples.
Finally, the wipe sample in its plastic bag was
positioned within the frame of the metal dust wipe
holder (NITON part number 180-407 or
equivalent).
Calibration
The instrument is factory calibrated. For the
verification test, the instrument performance was
verified at the start and end of each day's analyses
by analyzing samples of known quantity.
Sample Analysis
The following is the procedure that was used to
analyze the samples during the verification test.
Note that eight sample measurements were taken
to insure that the entire area of the folded dust
wipe sample was properly measured by the
spectrometer. However, when it was observed that
there was virtually no response to the wipe for
lead, the vendor assumed that the test sample was
a blank, and truncated the number of
measurements at four.
1.
The dust wipe was placed in the sample holder at
the number-one position and a 60 second (s)
measurement was taken. The sample was then
placed in the number two position and another 60s
reading was taken. The wipe was rotated 180
degrees (without turning the sample holder upside-
down), and placed in the number one position for a
third 60 s measurement. Finally, the wipe was
measured in the number two position for a fourth
reading. The four readings were averaged and
represented the concentration measured on the
"front" of the wipe. The wipe was then flipped
over and the procedure repeated to obtain four
measurements on the "back" of the wipe. The
average concentration from the "front" was
averaged with the average concentration from the
"back" readings to produce the final result.
The x-ray tube in the XLt 700 spectrum analyzer
was approximately 3 months old. However, decay
and half-life time corrections are not relevant
factors for an x-ray tubes. Time to complete each
individual measurement was 60 seconds.
5,
Di.'sl wipe fofdrf. Start at top lift, ami |:ira«-cd as sliown.nrakina
Figure 2. Schematic diagram of recommended folding procedure for dust
wipes. (Not to scale.) 3
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Section 3 — Verification Test Design
Objective
The purpose of this section is to describe the
verification test design. It is a summary of the test
plan (ORNL 2001).
Testing Location and Conditions
The verification of field analytical technologies for
lead in dust wipes was conducted at the EPA/Region
1 Laboratories in North Chelmsford, Massachusetts.
The test was conducted in one particular laboratory.
The temperature and relative humidity were
monitored during field testing, but remained fairly
constant. The average temperature and relative
humidity over the four days of testing were 71 °F
and 40%, respectively.
Drivers and Objectives for the Test
The purpose of this test was to evaluate the
performance of field analytical technologies that are
capable of analyzing dust wipe samples for lead
contamination. This test provides information on the
potential applicability of field technologies to EPA
standards for dust clearance testing. The
experimental design was designed around the three
clearance standards of 40 |ig/ft2 for floors, 250 |ig/ft2
for window sills, and 400 |ig/ft2 for window troughs
that are outlined in 40 CFR Part 745.227(e)(8)(viii)
(CFR2001).
The primary objectives of this verification were to
evaluate the field analytical technologies in the
following areas: (1) how well each performs relative
to a conventional, fixed-site, analytical method for
the analysis of dust wipe samples for lead; (2) how
well each performs relative to results generated in
previously rounds of ELPAT testing, and (3) the
logistical and economic resources necessary to
operate the technology. Secondary objectives for
this verification are to evaluate the field analytical
technology in terms of its reliability, ruggedness,
cost, range of usefulness, sample throughput, data
quality, and ease of use. Note that this verification
test does not provide an assessment of the selection
of locations for dust samples in a facility or an
assessment of the way that dust samples are
collected. The planning for this verification test
follows the guidelines established in the data quality
objectives process.
Summary of the Experimental Design
All of samples analyzed in this verification test were
archived from the original verification test in 2001.
In August, 2002, a suite of 16 samples from these
lots were shipped to the reference laboratory,
DataChem (Cincinnati, OH), and analyzed, in order
to confirm that the lead concentrations on the sample
wipes had not changed. Based on the values
reported by DataChem, there was no evidence to
suggest that there had been any demonstrable change
in the lead levels on the tested sample wipes. For
this particular test, the samples prepared in the fall of
2001 had been stored at -22° C since receipt.
All of the samples used in this verification test were
prepared gravimetrically. The wipes utilized in the
test (PaceWipe™ and Aramsco Lead Wipe™) met
the specifications of the American Society for
Testing and Materials requirements for lead testing
(ASTM 1996). Initial consideration was given to
conducting the test in a real-world situation, where
the technologies would have been deployed in a
housing unit that had been evacuated due to high
levels of lead contamination. In addition to the
safety concern of potentially subjecting participants
to lead exposure, the spatial variability of adjacent
samples would have been expected to be so great
that it would be much larger than the anticipated
variability of these types of technologies, therefore
making it difficult to separate instrument/method
variability and sampling variability. The availability
of well-characterized samples derived from "real-
world" environments made the use of proficiency
testing samples (so-called "ELPAT" samples) and
other prepared samples an attractive alternative.
ELPAT and Blank Sample Description
In 1992, the American Industrial Hygiene
Association (AIHA) established the Environmental
Lead Proficiency Analytical Testing (ELPAT)
program. The ELPAT Program is a cooperative
effort of the American Industrial Hygiene
Association (AIHA), and researchers at the Centers
for Disease Control and Prevention (CDC), National
Institute for Occupational Safety and Health
(NIOSH), and the EPA Office of Pollution
Prevention and Toxics (OPPT). The ELPAT
program is designed to assist laboratories in
improving their analytical performance, and
therefore does not specify use of a particular
-------
analytical method. Participating laboratories are
sent samples to analyze on a quarterly basis. The
reported values must fall within a range of
acceptable values in order for the laboratory to be
deemed proficient for that quarter.
Research Triangle Institute (RTI) in Research
Triangle Park, NC, is contracted to prepare and
distribute the lead-containing paint, soil, and dust
wipe ELPAT samples. For the rounds of testing
which have occurred since 1992, archived samples
are available for purchase. Some of these samples
were used in this verification test. Because the
samples have already been tested by hundreds of
laboratories, a certified concentration value is
supplied with the sample. This certified value
represents a pooled measurement of all of the results
submitted, with outliers excluded from the
calculation.
The following description, taken from an internal
RTI report, briefly outlines how the samples are
prepared. RTI developed a repository of real-world
housedust, collected from multiple homes in the
Raleigh/Durham/Chapel Hill area, as well as from an
intervention project in Wisconsin. After collection,
the dust was sterilized by gamma irradiation and
sieved to 150 jam. A Pace Wipe™ was prepared for
receiving the dust by opening the foil pouch,
removing the wet folded wipe and squeezing the
excess moisture out by hand over a trash can. The
wipe was then unfolded and briefly set on a
Kimwipe to soak up excess moisture. The
Pace Wipe was then transferred to a flat plastic board
to await the dust. The weighing paper containing
the pre-weighed dust was then removed from the
balance, and 0.1000 ± 0.0005 g portion of dust was
gently tapped out onto the Pace Wipe. The wipe was
then folded and placed in a plastic vial, which was
then capped. All vials containing the spiked wipes
were stored in a cold room as a secondary means of
retarding mold growth until shipment.
Before use in the ELPAT program, RTI performed a
series of analyses to confirm that the samples were
prepared within the quality guidelines established
for the program. The data quality requirements for
the ELPAT samples were: 1) the relative standard
deviation of the samples analyzed by RTI must be
10% or less; 2) the measured concentrations must be
within 20% of the target value that RTI was
intending to prepare; and 3) analysis by an off-site
laboratory must yield results within ± 20% of the
RTI result. Ten samples were analyzed by RTI and
nine samples were sent to the Wisconsin
Occupational Health Laboratory for independent,
confirmatory analysis. All ELPAT samples used in
this test met the data quality requirements described
above. The estimated concentration for an ELPAT
sample used in this evaluation was the certified
("consensus") value (i.e., an analytically derived
result).
RTI prepared the blank samples using the same
preparation method as the ELPAT samples, but the
concentration of lead was< 2 jig/wipe, well below
the expected reporting limits of the participant
technologies.
University of Cincinnati Sample
Description
The ELPAT samples consisted of dust mounded in
the center of a PaceWipe. The University of
Cincinnati (UC) prepared "field QC samples" where
the dust was sprinkled over the wipe, more similar to
how a wipe would look when a dust wipe sample is
collected in the field. In a typical scenario, UC sends
these control samples to a laboratory along with
actual field-collected samples as a quality check of
the laboratory operations. Because the samples are
visually indistinguishable from an actual field
sample, are prepared on the same wipe, and are
shipped in the same packaging, the laboratory
blindly analyzes the control samples, which provides
the user with an independent assessment of the
quality of the laboratory's data.
A cluster of twenty UC samples prepared at the key
clearance levels were added to the experimental
design, primarily so that an abundance of data would
exist near the clearance levels, in order to assess
false positive and false negative error rates. The UC
samples were prepared on Aramsco Lead Wipes™
(Lakeland, FL). The UC wipe samples were
prepared using National Institute of Standards &
Technology (NIST) Standard Reference Materials
(SRMs). NIST SRM 2711 was used to prepare the
40 [ig/wipe samples, and NIST SRM 2710 was used
to prepare the 250 and 400 |j,g/wipe samples. Both
SRM 2711 and SRM 2710 are Montana Soil
containing trace concentrations of multiple elements,
including lead. Some NIST SRM materials that are
spiked on dust wipes are known to have low
extraction recoveries when prepared by standard
analytical methods (e.g., lead silicates cannot be
extracted unless hydrofluoric acid is used) (Ashley
et al. 1998). These particular SRMs are not known to
contain lead silicates or to give lower lead
-------
recoveries. However, it is important to note the
possibility of such when using NIST SRMs for lead
dust wipe analysis, since similar SRMs (e.g., Buffalo
River sediment from Wyoming) do show recoveries
in the low 90% range (Ashley et al. 1998).
Because accurate and precise estimated
concentrations for the UC samples were imperative,
ORNL imposed the following data quality
requirements for the UC-prepared wipe samples: 1)
each estimated concentration had to be within a 10%
interval of the target clearance level; 2) additional
quality control (QC) samples (at least 5% of the total
samples ordered) were to be prepared and analyzed
by UC as a quality check prior to shipment of the
samples; and 3) the relative standard deviation of the
QC samples had to be < 10%. It is important to note
here the reason why the data quality requirements
between the UC and ELPAT samples were different.
The data quality requirements for the ELPAT
samples (i.e., ± 20% of the target value) was
established by the ELPAT program. Since archived
samples were being used, the ELPAT data quality
requirements could not be changed.
As a quality check of the sample preparation
process, UC prepared an additional 24 samples (5%
of the total number ordered). UC extracted and
analyzed the samples following internal procedures
(nitric/hydrochloric acid extraction, followed by
atomic absorption spectrometry - see EPA 1996) and
provided those results to ORNL. For the 24 samples
(eight at each of the three clearance levels), the
average percent recovery (i.e., UC measured
concentration/UC estimated concentration x 100%)
was 97% (median value = 96%, standard deviation =
3%, range = 93% to 102%). Additionally, 42
randomly-selected samples (14 at each of the three
clearance levels) were analyzed an by EPA Region 1
laboratory in North Chelmsford, MA, as an
independent quality control check of the accuracy
and precision of UC's sample preparation procedure
(nitric acid digestion followed by ICP/AES analysis
- see EPA 1996). The average percent recovery
(EPA Region 1 reported concentration/UC estimated
concentration x 100%) was 90% (median 89%,
standard deviation = 2%), with a range of values
from 86% to 93%. The average recovery determined
from the EPA Region 1 analyses (90%) was lower
than that which was determined by UC (102%), but
both values were within the data quality requirement
of 100 ± 10%. Based on this data, ORNL
determined that the UC sample preparation process
met the established data quality criteria and was
deemed acceptable for use in the determination of
false positive/false negative error rates.
Distribution and Number of Samples
Figure 3 portrays the distribution of the sample
concentrations that were analyzed in this study. A
total of 160 samples were analyzed in the
verification test. For the ELPAT samples, four
samples were analyzed at each of 20 test levels (20
test levels x 4 samples each = 80 samples total).
While the set of four samples were prepared using
homogeneous source materials and an identical
preparation procedure, they cannot be considered
true "replicates" because each sample was prepared
individually. However, these samples represent four
samples prepared in the same batch of ELPAT
samples. Twenty samples were prepared near each
of the three clearance levels (3 test levels x 20
samples = 60 samples total) by UC, and RTI
prepared 20 "blanks" at lead concentrations < 2
[ig/wipe. In Figure 3, the clearance levels are
denoted as horizontal lines.
Sample Randomization
The samples were packaged in 20-mL plastic
scintillation vials and labeled with a sample
identifier. The participant received the same suite of
samples as used in previous tests, but in a
randomized order. The samples were distributed in
batches of 16. Completion of chain-of-custody forms
documented sample transfer.
Description of Performance Factors
In Section 5, technology performance is described in
terms of precision, accuracy, completeness, and
comparability, which are indicators of data quality
(EPA 1996). False positive and negative results,
sample throughput, and ease of use are also
described. Each of these performance characteristics
is defined in this section.
Precision
Precision is the reproducibility of measurements
under a given set of conditions. Standard deviations
estimated at each concentration level can be used to
establish the relationship between the uncertainty
and the average lead concentration. Standard
deviation (SD) and relative standard deviation
(RSD) for replicate results are used to assess
precision, using the following equation:
RSD = (SD/average concentration) x 100% .
(Eq. 1)
-------
8.
j*
=
"3
a
0
2
a
8
a
0
u
1400 -
1200 -
1000 -
800 -
600 -
200 -
(
v'V
^i /
I
) 5
'
•
clearance levels
•
_ •• _ •
•••""
10 15 20 25 30 35 4
Number of Concentration Levels
0
Figure 3. Distribution of both UC and ELPAT sample concentrations. Four replicates
were analyzed at each concentration level.
The overall RSD is characterized by two summary
values:
mean — i.e., average;
• range — i.e., the highest and lowest RSD values
that were reported.
The average RSD may not be the best representation
of precision, but it is reported for convenient
reference. An average RSD value less than 10%
indicates that the measurements are very precise.
RSDs greater than 20% should be viewed as
indicators of larger variability and possibly non-
normal distributions. The uncertainty in the
analytical measurements will include influences
from both the preparation (i.e., extraction) and
measurement steps.
Accuracy
Accuracy is a measure of how close the measured
lead concentrations are to estimated values of the
true concentration. The estimated values for the
ELPAT samples are the certificate values that are
reported on the certificate of analysis sheet provided
with the samples. The ELPAT certificate values
represent an average concentration determined by
more than 100 accredited laboratories that
participated in previous rounds of ELPAT testing.
The UC estimated value is the concentration
reported by UC for individual samples, calculated by
the amount of NIST-traceable material loaded on the
dust wipes. The accuracy and precision of the UC
value was assessed by an independent laboratory
analyzing randomly selected QC samples. An EPA
laboratory in Region 1 analyzed 10% of the total
number of samples prepared by UC at each of the
three concentration levels and confirmed that the
process used to prepare the samples met the pre-
determined data quality objective of accuracy within
a ± 10% interval of the estimated value.
Accuracy of the field technology measurements was
statistically tested using t-tests or non-parametric
tests at the 5% significance level. These statistical
tests compared the average results with the overall
estimated values using the precision of the sample
measurements. Bias was quantified by computing
the percent recovery for four similar samples or a
single sample using the equation:
percent recovery = [measured amount(s)/estimated
value] x 100% (Eq. 2)
Accuracy was assessed using both the ELPAT and
UC estimated concentrations. The comparison to the
ELPAT value represents how close the technology
reported results to the consensus value, which
represents the amount of "recoverable" lead in the
sample. Because the UC samples were prepared
gravimetrically from samples of known lead content,
the comparison to the UC samples represents how
-------
close the technology reported results to an absolute
lead value. Such would reveal any bias imposed by
the tested sampling and analytical method.
The optimum percent recovery value is 100%.
Percent recovery values greater than 125% indicate
results that are biased high, and values less than 75%
indicate results that are biased low. A small but
statistically significant bias may be detectable for a
field technology if precision is high (i.e., low
standard deviation). Bias within the acceptable
range can usually be corrected to 100% by
modification of calibration methods. But the field
technology can still have acceptable bias with an
average percent recovery in the interval of 75% to
125%.
Comparab///fy
Comparability refers to how well the field tech-
nology and the NLLAP-recognized laboratory data
agree. The difference between accuracy and
comparability is that accuracy is judged relative to a
known value, comparability is judged relative to the
results of a laboratory procedure, which may or may
not report the results accurately. Because true
"replicates" were not available for use in this study,
the averages from similar samples measured by the
technology was compared with corresponding
averages measured by the laboratory for all target
concentration levels.
A correlation coefficient quantifies the linear
relationship between two measurements (Draper and
Smith 1981). The correlation coefficient is denoted
by the letter r; its value ranges from -1 to +1, where
0 indicates the absence of any linear relationship.
The value r = -1 indicates a perfect negative linear
relation (one measurement decreases as the second
measurement increases); the value r = +1 indicates a
perfect positive linear relation (one measurement
increases as the second measurement increases). The
slope of the linear regression line, denoted by the
letter m, is related to r. Whereas r represents the
linear association between the vendor and laboratory
concentrations, m quantifies the amount of change in
the vendor's measurements relative to the
laboratory' s measurements. A value of+1 for the
slope indicates perfect agreement. Values greater
than 1 indicate that the vendor results are generally
higher than the laboratory, while values less than 1
indicate that the vendor results are usually lower
than the laboratory.
Detectable Blanks
Twenty samples in the test were prepared at <2
[ig/wipe, below the anticipated reporting limits of
both the field technology and the laboratory. Any
reported lead for these samples is considered a
"detectable blank".
False Positive/Negative Results
A false positive (fp) result is one in which the
technology detects lead in the sample above a
clearance level when the sample actually contains
lead below the clearance level (Keith et al. 1996). A
false negative (fh) result is one in which the
technology indicates that lead concentrations are less
than the clearance level when the sample actually
contains lead above the clearance level (Keith et al.
1996). For example, if the technology reports the
sample concentration to be 35 |j,g/wipe, and the true
concentration of the sample is 45 [ig/wipe, the
technology's result would be considered a fh.
Accordingly, if the technology reports the result as
45 |j,g/wipe and the true concentration is 35 |j,g/wipe,
the technology's result would be a fp.
A primary objective for this verification test was to
assess the performance of the technology at each of
the three clearance levels of 40, 250, and 400
[ig/wipe, and estimate the probability of the field
technology reporting a fp or fh result. For each
clearance level, the probabilities of fh were
estimated as curves that depend on a range of
concentrations reported about the clearance level.
These error probability curves were calculated from
the results on the 60 UC samples at concentrations ±
10% of each clearance level. In order to generate
probability curves to model the likelihood of false
negative results, it was assumed that the estimated
concentration provided by UC was the true
concentration. However, this evaluation did not
include the gravimetric preparation uncertainty in
the UC estimated concentration. This error is likely
to be much smaller than other sources of
measurement error (e.g., extraction efficiency and
analytical).
The fp/fh evaluation also included a comparison to
the ELPAT sample results. The "estimated" value
for the UC and ELPAT samples are defined
differently (Recall that the UC value is based on
weight of the NIST-traceable material, while the
ELPAT estimated value is the average analytical
reported value from more than 100 accredited
laboratories.) The UC sample estimated lead content
-------
is determined gravimetrically, which should be
closer to the "true" concentration than an analytical
measurement that includes preparation and
instrumental errors. In contrast, determining the
technology's fp/fh error rates relative to the ELPAT
estimated concentrations represents a comparison to
typical laboratory values. One limitation of using the
ELPAT sample is that concentrations covered a
wider overall distribution of lead levels. Thus, the
availability of sample concentrations that were
tightly (i.e., +/- 10%) clustered about the clearance
levels was limited. In order to perform a broader
fp/fn analysis, the range of lead levels in the ELPAT
samples that bracketed the pertinent clearance levels
was extended to ± 25% of the target concentration.
Comp/efeness
Completeness is defined as the percentage of
measurements that are judged to be usable (i.e., the
result is not rejected). An acceptable completeness is
95% or greater.
Sample Throughput
Sample throughput is a measure of the number of
samples that can be processed and reported by a
technology in a given period of time. This is
reported in Section 5 as number of samples per day
per number of analysts.
Ease of Use
A significant decision factor in purchasing an
instrument is how easy the technology is to use.
Several factors are evaluated and reported on in
Section 5:
What is the required operator skill level (e.g.,
technician or advanced degree)?
How many operators were used during the test?
• Could the technology be run by a single person?
How much training would be required in order
to run this technology?
• How much subjective decision-making is
required?
Cosf
An important factor in the consideration of whether
to purchase a technology is cost. Costs involved with
operating the technology and a typical laboratory
analyses are estimated in Section 5. To account for
the variability in cost data and assumptions, the
economic analysis is presented as a list of cost
elements and a range of costs for sample analysis.
Several factors affect the cost of analysis. Where
possible, these factors are addressed so that decision
makers can independently complete a site-specific
economic analysis to suit their needs.
Miscellaneous Factors
Any other information that might be useful to a
person who is considering purchasing the
technology is documented in Section 5 under
"Observations". Examples of information that might
be useful to a prospective purchaser are the amount
of hazardous waste generated during the analyses,
the ruggedness of the technology, the amount of
electrical or battery power necessary to operate the
technology, and aspects of the technology or method
that make it user-friendly or user-unfriendly.
-------
Section 4 — Laboratory Analyses
Background
EPA regulations (40 CFRPart 745.227(e)(8)(vii))
specify that residences and child occupied facilities
built before 1978 that have undergone an abatement
must pass clearance testing (CFR 2001). These EPA
regulations also state in, 40 CFR Part 745.227(f)(2),
that dust samples for clearance must be analyzed by
a laboratory recognized by EPA (CFR 2001). Many
EPA-authorized state and tribal lead programs have
the same or similar requirements. EPA's vehicle for
recognizing laboratory proficiency is the National
Lead Laboratory Accreditation Program (NLLAP).
Although the NLLAP was initially designed to
accredit fixed site laboratories, in August 1996, the
NLLAP was modified so that mobile laboratory
facilities and testing firms operating portable testing
technologies could also apply for accreditation.
Despite this modification, the NLLAP list of
accredited laboratories has almost exclusively
consisted of fixed site laboratories. One possible
outcome of this ETV test is that more mobile
laboratory facilities and testing firms operating
portable testing technologies will apply for NLLAP
accreditation. In order to assess whether the field
portable technologies participating in this
verification test produce results that are comparable
to NLLAP-recognized data, an NLLAP-recognized
laboratory was selected to analyze samples
concurrently with the field testing.
NLLAP Laboratory Selection
NLLAP was established by the EPA Office of
Pollution Prevention and Toxics under the
legislative directive of Title X, the Lead-Based Paint
Hazard Reduction Act of 1992. In order for
laboratories to be recognized under the NLLAP they
must successfully participate in the ELPAT Program
and undergo a systems audit. The acceptable range
for the ELPAT test samples is based upon the
reported values from participating laboratories.
Acceptable results are within three standard
deviations from the consensus value. A laboratory's
performance is rated as proficient if either of the
following criteria are met: (1) in the last two rounds,
all samples are analyzed and the results are 100%
acceptable; or (2) three fourths (75%) or more of the
accumulated results over four rounds are acceptable.
The NLLAP required systems audit must include an
on-site evaluation by a private or public laboratory
accreditation organization recognized by NLLAP.
Some of the areas evaluated in the systems audit
include laboratory personnel qualifications and
training, analytical instrumentation, analytical
methods, quality assurance procedures, and record
keeping procedures.
The list of recognized laboratories is updated
monthly. ORNL obtained the list of accredited
laboratories in July 2001. The list consisted of
approximately 130 laboratories. Those laboratories
which did not accept commercial samples and those
located on the U.S. west coast were automatically
eliminated as potential candidates. ORNL
interviewed at random approximately ten
laboratories and solicited information regarding cost,
typical turnaround time, and data packaging. Based
on these interviews and discussions with technical
panel members who had personal experience with
the potential laboratories, ORNL selected DataChem
(Cincinnati, OH) as the fixed-site laboratory. As a
final qualifying step, DataChem blindly analyzed 16
samples (8 ELPAT and 8 prepared by UC) in a pre-
test study. As shown in Table 1 below, DataChem
passed the pre-test by reporting concentrations that
were within 25% of the estimated concentration for
samples above the reporting limit.
Laboratory Method
The laboratory method used by DataChem was hot
plate/nitric acid digestion, followed by inductively
coupled plasma-atomic emission spectrometry (ICP-
AES) analysis. The preparation and analytical
procedures, as supplied by DataChem, can be found
in the test plan (ORNL 2001). To summarize the
procedure, the wipe was digested in 2 mL of nitric
acid, heated in a hotblock for 1 hour at 95 °C,
diluted to 20 mL with distilled water, and analyzed
by ICP-AES. DataChem's procedures are
modifications of Methods 3 05 OB and 601 OB of EPA
SW-846 Method Compendium for the preparation
and analysis of metals in environmental matrices
(EPA 1996). Other specific references for the
preparation and analysis of dust wipes are available
from the American Society for Testing and Materials
(ASTM 1998).
10
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Table 1. Summary of DataChem Pre-Test Results
Sample
Type
ELPAT
ELPAT
ELPAT
ELPAT
ELPAT
ELPAT
ELPAT
ELPAT
UC
UC
UC
UC
UC
UC
UC
UC
DataChem
Reported Cone
(US/wipe)
<20
<20
41
44
190
210
440
450
<20
<20
25
38
150
200
250
310
Estimated
Cone
(US/wipe)
2.12
2.12
41.3
41.3
201.6
201.6
408.7
408.7
10.3
5.9
29.9
44
172.4
237.5
327.3
379
Percent
Recovery
n/a
n/a
99%
107%
94%
104%
108%
110%
n/a
n/a
84%
86%
87%
84%
76%
82%
Analysis
Order
16
12
6
3
15
9
2
13
4
1
14
10
11
7
5
8
Laboratory Performance
ORNL validated all of the laboratory data according
to the procedure described in the verification test
plan (ORNL 2001). During the validation, the
following aspects of the data were reviewed:
completeness of the data package, correctness of the
data, correlation between "replicate" sample results,
and evaluation of QC sample results. Each of these
categories is described in detail in the verification
test plan. An evaluation of the performance of the
laboratory results through statistical analysis of the
data was performed and is summarized below. (See
Section 3 for a detailed description of how the
performance factors are defined and the calculations
that are involved.)
In Table 2, DataChem's reported values are
compared to the estimated values to determine
percent recovery (i.e., accuracy of the DataChem
results) for both the ELPAT and the UC samples. A
line fitted to the data using both data sets is shown
graphically in Figure 4. The average percent
recovery for the ELPAT samples was 98%, while
the average for the UC samples was 91%. Both
Table 2 and Figure 4 indicate that the analytical
results from the University of Cincinnati wipe
samples were generally reported lower than the
estimated value, while the results for the ELPAT
samples were closer to the estimated value. The
better agreement with the ELPAT samples is not
unexpected, given that the ELPAT estimated
concentrations represent analytical consensus values
that include typical extraction inefficiencies and
instrumental error. A regression analysis of the
individual data sets shows that both the negative bias
for the UC and the slightly negative bias for the
ELPAT samples were statistically significant (i.e.
slope not equal to 1.0). The cause of the negative
bias for the UC samples could be related to: 1)
extraction inefficiencies (due to the use of NIST
SRMs that contain lead that is unrecoverable with
the extraction procedure which was used) and/or, 2)
typical analytical variation due to preparation and
measurement errors. Another indication of accuracy
is the number of individual ELPAT results which
were reported within the acceptance ranges that have
been established for those samples. For the 72
ELPAT samples (> 20 jig/wipe), DataChem reported
71 (99%) within the acceptable ranges of values.
(see Appendix).
The precision assessment presented in Table 3
indicates that the analyses were very precise. The
average RSD for the ELPAT samples was 7%, while
the average RSD for the UC samples was 8%. The
variability of the UC sample preparation process,
provided for reference of the minimal achievable
RSD for the UC samples, was 6%. A single estimate
of the ELPAT variability was not determined, since
the ELPAT samples were comprised of 20 different
batches of samples. DataChem reported all 20
detectable blank samples correctly as < 20 jig/wipe.
In addition, DataChem reported seven of the eight
samples with estimated concentrations of either 16.9
[ig/wipe or 17.6 |j,g/wipe as less than their detection
limit and only one was incorrectly reported as 30
[ig/wipe.
11
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Table 2
. Summary of DataChem Percent Recovery Values by Samp
Statistic
n a
average % recovery
standard deviation
minimum % recovery
maximum % recovery
ELPAT
72
98
9
81
143
uc
60
91
3
86
102
1 excludes estimated values <20 p,g/wipe (n=28)
le Source
•
e«
0
500 -,
400 -
300 -
200 -
100 -
0 -
D ELPAT (n=72)
• Univ of Cinci(n=60)
0 100 200 300 400
Estimated value (ug/wipe)
500
Figure 4. Plot of DataChem reported values versus estimated values, shown for concentrations
less than 500 jig/wipe. This figure indicates that UC-prepared wipes were generally reported
lower than ELPAT samples.
Table 3. Summary of DataChem Precision Estimates by Sample Source
Sample Source
ELPAT
UC
UC preparation
n
0.25
3b
3C
average RSD
7
8
6
Min RSD
2
6
6
Max RSD
21
9
7
" 4 replicates in each sample set
b 20 replicates in each sample set
: This value represents the variability in the sample preparation process.
12
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An important evaluation parameter for the analysis of
dust wipe samples is how the method performs at the
clearance levels and the method's likelihood of
reporting false positive (fp) and false negative (fn)
results. Recall from the experimental design that 20
UC samples were prepared at ± 10% of each
clearance level of 40, 250, and 400 jig/wipe, for a
total of 60 UC samples. The ELPAT samples
covered a wider range of concentrations. A total of
40 ELPAT samples fell within a ±25% interval of the
target values that could be used for the fp/fn
assessment. The number of false negative and false
positive results reported by DataChem relative to the
UC and ELPAT estimated concentrations is
summarized in Table 4. There are a specific number
of possible fp and fn results. For example, if the
estimated lead level on the wipe is less than the
clearance level (CL), then it is not possible to
produce a false negative result; only a false positive
(i.e., > 40) result is possible. As shown in Table 4,
for the UC samples, in every case where the
estimated concentration was less than the CL,
DataChem reported a result for that was also less
than the CL, indicating no fp results at any of the
three CL. DataChem reported two fp results for the
ELPAT samples out of a possible 12. When the
estimated concentration was above the clearance
level, however, DataChem sometimes reported
results as less than the clearance level. DataChem
reported a higher rate of fn results for the UC
samples than the ELPAT samples (23 of 30 vs 7 of
28 possible fn results, respectively). This finding is
not surprising, since the results reported above
indicated that DataChem's results were negatively
biased, or reported lower than the estimated values
for the UC samples. As stated in Section 3, it is
important to note that in this evaluation, the
estimated concentration of the UC samples is
assumed to be the "true"concentration, and the
uncertainty in gravimetric preparation for the UC
estimated concentration is not considered in the
evaluation.
Figures 5, 6, and 7 show models of the likelihood of
DataChem reporting a false negative result at each of
the clearance levels versus the true concentrations of
the UC samples. Note that only the UC samples are
used in generation of probability curves because
these estimated values are a closer representation of
the true lead concentration than the ELPAT
estimated concentration. (Song et al. 2001) These
figures indicate that the likelihood of DataChem
reporting false negative results for the UC samples at
the exact clearance level is high, near 100% in all
three cases. This means, for example, that if
DataChem reported a value as exactly 250 |j,g/wipe,
the probability that the true concentration is >250 is
essentially 100%. Again, this is due to the negative
bias that was observed in the measurement of the UC
samples. The plots also demonstrate that, due to the
relatively high level of precision of results reported
by DataChem, the performance is very minimally
impacted by performing replicate analyses, as the
distribution of false negative probabilities is very
similar whether 1 or 5 measurements (in Figures 5, 6,
and 7, delineated as N = 1, N = 2, etc.) are
performed. The interpretation of these curves for use
in a "real-world" situation can be demonstrated by
the following example. Suppose that a user decides
that an acceptable level of risk for having false
negative results is 5%. Using Figure 5,5% FN
probability (y = 0.05) corresponds to a "true" lead
concentration of 46 [ig/wipe (meaning if the true
concentration of the sample is 46 |j,g/wipe, there is
only a 5% chance/risk that DataChem will report the
value as < 40 |j,g/wipe.)
When the DataChem measured values versus the
estimated concentrations for each of the three CL, the
equation of the linear regression lines can be
calculated. The slope, intercept, and correlation
coefficient for the ELPAT and UC samples are
presented in Table 5. The user might like to know at
what reported value (and at what associated
probability) will DataChem be likely to report a
"clean" sample (i.e., there is a high probability that
the true concentration is < CL). For example, for the
UC samples, we know that a value reported by
DataChem as 39 jig/wipe is biased low and will have
a true concentration of > 40 (41.8 |j,g/wipe, using the
linear regression equation in Table 5). A true
concentration of 40 |j,g/wipe for a UC sample would
correspond to a reported value rounded to the nearest
whole number of 37 |j,g/wipe (see Table 5). For an
ELPAT sample, a true concentration of 40 [ig/wipe
corresponds to a DataChem reported value of 40
|j,g/wipe, because the negative bias was so small for
the ELPAT samples. Estimates of the reported
concentration at the 250 and 400 [ig/wipe levels are
reported in Table 5. In both cases, the reported
concentrations for the ELPAT samples are higher
(i.e., closer to the clearance level) than those of the
UC samples.
The user is reminded that the data obtained during
this verification test represent performance at one
13
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point in time. The data produced by DataChem at
some other time after the writing of this report may
or may not be similar to what has been produced
here. To understand a method's performance at
critical clearance levels, it is recommended that the
user perform their own assessment of the method's
performance by including samples of known
concentration (at or near the clearance levels) along
with the analysis of "real-world" samples.
Table 4. False Positive/False Negative Results for DataChem Measurements of UC Samples
Evaluation Parameter
fp: # samples where
DataChem reported the result
as > CL of the # samples
where the estimated
concentration was < CL
fn: # samples where
DataChem reported the result
as < CL of the # samples
where the estimated
concentration was > CL
Sample
Source
UC
ELPAT
UC
ELPAT
Number of Samples
40 jig/wipe
Oof 9
Oof 4
5 of 11
lof 12
250 jig/wipe
Oof 11
2 of 8
9 of 9
5 of 8
400 jig/wipe
Oof 10
OofOa
9 of 10
lof 8
Total
Oof 30
2 of 12
23 of 30
7 of 28
a Because all eight ELPAT values were above 400 |ig/wipe,
CL = clearance level
no samples were available to assess fp results at this level.
True Pb Concentration (ug/wipe)
Figure 5. False negative probabilities for DataChem average concentrations at a target
concentration level of 40 |ig/wipe.
14
-------
250
260
270
280
290
300
310
320
True Pb Concentration (ug/wipe)
Figure 6. False negative probabilities for DataChem average concentrations at a target
concentration level of 250 jig/wipe.
o.o ^
400 410 420 430 440 450 460 470 480 490 500
True Pb Concentration (ug/wipe)
Figure 7. False negative probabilities for DataChem average concentrations at a
target concentration level of 400 |ig/wipe.
15
-------
Table 5. Summary of the Linear Regression Constants and Recovery Data for DataChem's
Measurements Versus the Estimated Concentrations at the Clearance Levels
Evaluation Parameter
n
slope
intercept
correlation coefficient
average % recovery
SD of % recovery
Reported concentration at
theCL
40 jig/wipe
UC
20
1.021
-3.673
0.884
93%
4%
37
jig/wipe
ELPAT
16
1.612
-6.182
0.84
101%
13%
40
jig/wipe
250 |ig/wipe
UC
20
0.829
18.557
0.879
90%
3%
226
jig/wipe
ELPAT
16
0.578
90.826
0.549
96%
9%
234
jig/wipe
400 jig/wipe
UC
20
0.736
67.649
0.861
91%
3%
362
jig/wipe
ELPAT
8
2.394
-575.771
0.492
100%
5%
382
jig/wipe
16
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Section 5 — Technology Evaluation
Objective and Approach
The purpose of this section is to present a statistical
evaluation of the XLt 700 XRF data and determine
the technology's ability to measure lead in dust wipe
samples. This section includes an evaluation of
comparability through a one-to-one comparison with
NLLAP-recognized laboratory data. Other aspects of
the technology (such as accuracy, precision, cost,
sample throughput, hazardous waste generation, and
logistical operation) are also evaluated in this
section. The Appendix contains the raw data
provided by the vendor during the verification test
that were used to assess the performance of the XLt
700.
Precision
Precision is the reproducibility of measurements
under a given set of conditions. Precision was
determined by examining the results of blind
analyses for replicate samples with estimated
concentrations greater than the XLt 700 reporting
limit (10 |j,g/wipe). For the ELPAT samples,
precision was measured on each set of four samples
from a particular round of archived samples. For the
20 sets of ELPAT samples, the results in Table 6
demonstrate that the XLt 700's average RSD value
was 11%, with a range from 2 to 26%, indicating that
the XLt 700 measurements were precise. For the UC
samples, 20 samples were analyzed at three target
concentration levels of 40, 250, and 400 |j,g/wipe.
With the expectation that UC was to prepare the
samples as close to the target concentrations as
possible, the allowable laboratory variability was
10% RSD. As presented in Table 6, the actual
laboratory variability of the UC preparation process
was an average of 5% RSD. The average precision
of the UC sample measurements by the XLt 700 was
11% RSD.
Accuracy
Accuracy represents the closeness of the XLt 700's
measured concentrations to the estimated content of
spiked samples. A practical measure of accuracy is
the number of results for the ELPAT samples that
were reported within the acceptance ranges that have
been established for those samples. Of the 80 ELPAT
samples, the XLt 700 reported 71 of the results (89%
of the total) within the acceptance ranges. For those
values outside of the acceptance range, 2 values were
below the lower limit and 7 values were above the
upper limit.
Table 6. Precision of the XLt 700
Source
ELPAT
UC
UC prep c
No. of
sample
sets
0.33333
3*
o
6
RSD, %
Average
11
11
5
Min
2
10
4
Max
26
12
6
" 4 replicates in each sample set
b 20 replicates in each sample set
0 precision of UC sample preparation process
The results reported by the XLt 700 can also be
compared to the ELPAT certificate value, i.e., the
average concentration reported by 100+ laboratories
who participated in previous rounds of ELPAT
testing. These results are presented in Table 7.
Table 7. Accuracy of XLt 700
Statistic
na
average
standard deviation
median
minimum
maximum
% Recovery
ELPAT
80
101
14
99
77
151
UC
60
97
12
97
74
145
a Excludes estimated values < 10 p,g/wipe
The results for the 80 ELPAT samples reported by
the XLt 700 had an average percent recovery value
of 101%, the range of values was from 77 to 151%,
and the median value was 99%. The UC sample
results were slightly lower, with an average percent
recovery of 97%, and a range of values from 74% to
145%. Both average recovery values were within the
range of acceptable bias (100% ± 25%).
17
-------
Another way to assess accuracy is to perform a
regression analysis for the results obtained with the
XLt 700 versus the estimated values that are > 10
|j,g/wipe (without constraining the intercept of the
regression to pass through zero). The linear
regression constants for the line fitted to the ELPAT
and the UC data are listed in Table 8. That the slopes
are statistically (at the 5% significance level) less
than 1.00, indicates that the results are biased slightly
low. The fact that this small bias is statistically
significant indicates that the precision on the slope
measurement is exceptional and thus small
differences from the ideal slope of 1.00 can be
detected. While the performance met the criteria
stated for accuracy in Section 4 (unbiased if the
average percent recovery is between 75 and 125%),
the XLt 700 result generally were reported
significantly less than the estimated value.
Comparability
Comparability refers to how well the XLt 700 and
the NLLAP-recognized laboratory data agreed. In
this evaluation, the laboratory results are not
presumed to be the "correct" answers. Rather, these
results represent what a typical fixed laboratory
would report for these types of samples. A direct
comparison of the XLt 700 results and the laboratory
results was performed for all ELPAT and UC
samples that were reported above 20 |j,g/wipe. (Note:
Data were reported to 10 |j,g/wipe for the XLt 700,
but the lab only reported to 20 jig/wipe.) Because
each wipe was prepared individually, a true one-to-
one matching of XLt 700 and laboratory results can
not be performed. However, the average
concentrations of the samples prepared at specific
levels can be compared for the XLt 700 and
laboratory results. In Table 8, the regression
constants for the average XLt 700 results versus the
average DataChem results for both the ELPAT and
UC values are presented. The differences between
the regression slopes (m = 0.977 for ELPAT and m =
0.995 for UC) and a slope with a perfect agreement
line (m = 1.000) are not statistically significant, and
the correlation coefficients (r = 0.999 for both
ELPAT and UC) show a strong linear relationship
between DataChem and XLt 700 results. To illustrate
the strong linear agreement between the XLt 700 and
NLLAP laboratory results, Figure 8 is a plot of the
average XLt 700 results versus the average
DataChem results for both ELPAT and UC data. For
clarity, only those values < 500 [ig/wipe are shown.
Detectable Blanks
Of the samples that were prepared at <2 |j,g/wipe, the
XLt 700 correctly reported all 20 as less than the
reporting limits. The reporting limit was < 10
|j,g/wipe, so no detectable blanks were reported.
Table 8. Linear regression constants for the plots of the XLt 700 versus the estimated values and
versus the DataChem average measurements
Statistic
n
slope
(standard error)
intercept
(standard error)
r
versus estimated values
UC
60
0.909
(0.019)
5.817
(5.111)
0.988
ELPAT
80
0.963
(0.012)
1.434
(5.516)
0.994
versus DataChem average concentrations
UC
3
0.995
(0.010)
4.775
(2.478)
0.999
ELPAT
18
0.977
(0.011)
3.076
(5.000)
0.999
18
-------
500 -i
,—. 45° '-
§_ 400 :
'^ 350 -
"S) 300 -
-5- 250 -i
200 ^
150 :
100 -
50 -
0
o
0
50
100 150 200 250 300 350 400 450 500
DataChem Avg (ug/wipe)
Figure 8. Plot of the average XLt 700 concentration versus the average DataChem
concentration for all samples (n=21), shown for ELPAT and UC concentrations less than
500 |ig/wipe.
False Positive/False Negative Results
Similar to the evaluation described and presented in
Section 4 for DataChem, the number of false
negative and false positive results reported by the
XLt 700 relative to the estimated concentrations for
both the ELPAT and UC samples are summarized in
Table 9. For many cases where the estimated
concentration was equal to or greater than the
clearance level (CL), the XLt 700 reported a result
that was less than the CL (10 of 23 possible fn results
for the UC samples, and 8 of 28 fn results for the
ELPAT samples at the three CLs). When the
estimated concentration was less than the clearance
level, however, the XLt 700 reported a lower
percentage as greater than the CL (8 of 37 possible
fp results for UC samples and 1 of 12 fp results for
ELPAT samples). These findings are not surprising,
since the accuracy results reported above indicated
that the XLt 700 results were slightly negative
biased, or reported less than the estimated values.
In Figures 9, 10, and 11, the false negative
probabilities at the three clearance levels are
compared for the DataChem and XLt 700 results.
Ideally, a symmetric distribution of results about the
clearance level would give a fn probability of 0.5.
The XLt 700 results are closer to this ideal for all
clearance levels but have a larger spread over the true
concentration range. In these figures, the two-sided
90% confidence intervals (not shown for clarity) are
used to expressed uncertainty on the false negative
curves. These confidence intervals overlap for the
XLt 700 and DataChem for the 40 |j,g/wipe clearance
levels over the range of 38 to 55 jig/wipe shown in
the Figure 9. The overlapping confidence intervals
indicate the two methods are comparable when
considering their uncertainty. In Figures 10 and 11,
the 90% confidence intervals for the two methods
overlap in the ranges of 243 to 355 |J,g/wipe and 379
to 500 |j,g/wipe for the 250 |j,g/wipe and 400 |j,g/wipe
clearance levels, respectively. Again, the
overlapping confidence intervals indicate the two
methods are comparable when considering their
uncertainty.
Table 10 describes the linear regression constants for
XLt 700 measured concentration versus estimated
concentration for the three CLs, average percent
recovery values and standard deviations, and an
estimate of the XLt 700 reported concentration at
each clearance level. The average recoveries in Table
10 indicate that the XLt 700 results were negatively
biased for the two highest clearance levels for both
ELPAT and UC samples. This is also apparent in the
estimated concentration that a user might require
from the XLt 700 in order to be reasonably confident
that the true result is below the clearance level. For
samples with actual CL concentrations, the expected
DataChem results would have to be 37, 226, and 362
|j,g/wipe, respectively, to provide confidence that
sample concentrations with reported results at or
above the CL concentrations are really greater than
40, 250, and 400 jig/wipe. The XLt 700 is also
negatively biased for samples with the two highest
CL concentrations with expected reporting results of
232, and 371 jig/wipe. Reported XLt 700 results at
19
-------
or greater than the two highest CL concentrations
would likely indicate sample values greater than the
respective CL. For the 40 |j,g/wipe CL, the expected
XLt 700 result is 42 [ig/wipe. Therefore, reported
results below 40 |j,g/wipe (e.g., 36 to 39 |j,g/wipe)
may indicate samples with concentrations at or
greater than the CL.
Once again, the reader is reminded that the fp/fh
evaluation reported herein is based on the
instrument's performance during this verification
test. Results produced under different conditions and
with different samples may or may not be similar.
Regardless of analytical technique, there is some
uncertainty in assessing false positive and false
negative error rates around critical action levels due
to "normal" levels of variability (Song et al. 2001).
Analytical values falling near the level of interest
should be interpreted with care for both fixed-
laboratory and field-based analytical methods.
Table 9. False Positive/False Negative Error Rates for XLt 700 Measurements
Evaluation Parameter
fp: # samples where XLt 700
reported the result as > CL of
the # samples where the
estimated concentration was <
CL
fn: # samples where XLt 700
reported the result as < CL of
the # samples where the
estimated concentration was >
CL
Sample
Source
UC
ELPAT
UC
ELPAT
Number of Samples
40 jig/wipe
6 of 12
Oof 4
2 of 8
lof 12
250 jig/wipe
2 of 14
lof 8
3 of 6
5 of 8
400 jig/wipe
Oof 11
OofOa
5 of 9
2 of 8
Total
8 of 37
lof 12
10 of 23
8 of 28
a Because all eight ELPAT values were above 400 |ig/wipe,
CL = clearance level
no samples were available to assess fp results at this level.
1.0
0.9
0.8 -
0.7
0.6
v
1
Q.
0.1 H
o.o
10
DataChem
NITON XLt 700
15
20
25
30
35
40
45
50
55
True Pb Concentration (ug/wipe)
Figure 9. Comparison of false negative probabilities for the XLt 700
and DataChem average concentrations at a target concentration of 40
fig/ wipe.
20
-------
225
250
275
300
325
350
375
400
425
True Pv Concentration (ug/wipe)
Figure 10. Comparison of the false negative probablilites for the XLt 700
and DataChem average concentrations at a target concentration of 250
fig/wipe.
o.o
375
400
425
450
475
500
True Pb Concentration (ug/wipe)
Figure 11. Comparison of the false negative probabilities for the XLt
700 and DataChem average concentrations at a target concentration
level of 400 fig/wipe.
21
-------
Table 10. Summary of the Linear Regression and Recovery Data for the XLt 700 Response versus
the Estimated Concentrations
Evaluation Parameter
n
slope
intercept
correlation coefficient
average % recovery
SD of % recovery
Reported concentration at
theCL
40 |ig/wipe
UC
20
0.76
11.964
0.406
107%
12%
42
jig/wipe
ELPAT
16
1.1
-1.704
0.81
106%
15%
42
jig/wipe
250 |j,g/wipe
UC
20
0.705
55.608
0.434
93%
8%
232
jig/wipe
ELPAT
16
0.557
94.643
0.567
96%
9%
234
jig/wipe
400 jig/wipe
UC
20
1.157
-91.326
0.616
92%
85
371
jig/wipe
ELPAT
8
4.92
-1606.641
0.834
103%
6%
361
jig/wipe
Completeness
Completeness is defined as the percentage of
measurements that are judged to be usable (i.e., the
result was not rejected). Valid results were obtained
by the technology for all 160 dust wipe samples.
Therefore, completeness was 100%.
Sample Throughput
Sample throughput is representative of the estimated
amount of time required to prepare and analyze the
sample and perform the data analysis. Operating in
the field, two analysts (NITON experts) analyzed all
160 samples in 32.75 hours over 3.5 calendar days.
Eight measurements were taken for each sample
wipe and four for each blank, for a total of 1,200
measurements. One analyst prepared the sample and
the other analyst measured and recorded the data.
Ease of Use
The technology can be operated by a single person.
Users unfamiliar with the technology should attend a
one-day training course provided by NITON. No
particular level of educational training is required for
the operator. The analysts who operated the
instrument during the verification test were NITON
experts.
Cost Assessment
The purpose of this economic analysis is to estimate
the range of costs for analysis lead in dust wipe
samples using the NITON XLt 700 XRF and a
conventional analytical laboratory method. The
analysis was based on the results and experience
gained from this verification test, costs provided by
NITON, and representative costs provided by the
laboratory to analyze the samples. To account for the
variability in cost data and assumptions, the
economic analysis is presented as a list of cost
elements and a range of costs for sample analysis by
the XRF spectrum analyzer and by the laboratory.
Costs were prepared at the time this report was
written and are subject to change.
Several factors affected the cost of analysis. Where
possible, these factors were addressed so that
decision makers can complete a site-specific
economic analysis to suit their needs. The following
categories are considered in the estimate:
sample shipment costs,
• labor costs, and
equipment costs.
Each of these cost factors is defined and discussed
and serves as the basis for the estimated cost ranges
presented in Table 11. This analysis assumed that the
individuals performing the analyses were fully
trained to operate the technology. Costs for sample
acquisition and pre-analytical sample preparation,
tasks common to both methods, were not included in
this assessment.
22
-------
Table 11. Estimated analytical costs for lead dust wipe samples
Analysis method:
Analyst/manufacturer:
Sample throughput:
Cost category
Sample shipment
Labor
Rate
Equipment
Instalment purchase price
Reagents/supplies
Waste Disposal
XLt700 XRF
NITON
45 - 50 samples/day
Cost ($)
0
50-100/h per analyst
$20,000 - $40,000
0.10 per sample
Ob
Analysis method:
NLLAP Laboratory:
Actual turnaround:
Cost category
Sample shipment
Labor
Overnight shipping
Labor
Rate
Equipment
Waste Disposal
EPASW8466010b
DataChem
1 8 working days
Cost ($)
100-200
50-100
30 per sample
Included "
Included
""Included" indicates that the cost is included in the labor rate.
b There was no cost to dispose of hazardous waste from the verification test because ORNL elected to keep the "used" wipes
since the analysis is non-destructive. However, in a real-world situation, the user would have the option of sending the
wipes to an NLLAP laboratory for secondary analysis, archiving the samples, or disposing of the wipes as waste.
XLt 700 Series XRF Costs
The costs associated with using the spectrum
analyzer included labor and equipment costs. No
sample shipment charges were associated with the
cost of operating the spectrum analyzer because the
samples were analyzed on site.
Labor
Labor costs included on-site labor to perform the
analyses. The cost of the on-site and/or local labor
was estimated at a rate of $50-100/h, depending on
the required expertise level of the analyst. This cost
element included the labor involved during the entire
analytical process, comprising sample preparation,
sample management, analysis, and reporting. If the
user would have to travel to the site, the cost of
mobilization and demobilization, travel, and per
diem expenses should also be considered. However,
in a typical application where the XLt 700 might be
used, the analysis would usually be carried out by a
person located on site.
Equipment
Equipment costs included purchase of equipment,
and the reagents and other consumable supplies
necessary to complete the analysis.
• X-ray tube Description (provided by NITON):
For the analysis of lead, the instrument is
supplied with a low power miniature x-ray tube
that utilizes a silver anode transmission window.
A tube-excited instrument does not experience
the loss of measurement speed over time that is
common with most radioisotope-based
instruments, so the measurement time is equal to
the real time for the life of the x-ray tube. This
means that the end user will always experience
the same instrument performance in terms of
precision and accuracy in the same amount of
time. Miniature x-ray tubes have been in
commercial use for only about a year at the time
of this evaluation, so no data exists to confirm
the life expectancy of them in a portable
analyzer. The use of low power x-ray tubes in
bench-top analyzers has shown a life expectancy
of 3-5 years under less rugged conditions, but
reliability data must be generated over time to
make similar predictions for portable analyzers.
Replacement of the x-ray tube and associated
power supply is $5000, and includes the software
updates, re-calibration, and replacement of the
internal battery.
23
-------
Instrument purchase (provided by NITON):
NITON instruments, with the capability of the
XLt 700 series unit used in this evaluation (XLt
791), are available for dust wipe analysis in
various configurations. Pricing ranges from
approximately $20,000 to $40,000 with the
differences between analyzers existing in both
the range of elements and the matrices they are
capable of analyzing. The spectrum analyzer can
be calibrated for thin sample, bulk sample, or
both. In the simplest version, the spectrum
analyzer can quantify lead as well as Cr, Mn, Fe,
Co, Ni, Cu, Zn, As, Se, Hg, Rb, Sr, Y, Zr, and
Mo. It can also be upgraded for analysis of
soil/bulk samples with the same element suite.
The purchase price, irregardless of configuration,
includes the following:
• Shipping and handling
Test stand and holder for simple and
convenient dust wipe measurement
Two rechargeable lithium-ion battery packs
with 6-8 hour use (maximum depends on
platform and duty cycle)
110/220 VAC battery charger
Waterproof, crush-resistant carrying case
with locks
• Windows™ compatible NDT reporting
software with an RS-232 cable for
downloading data and spectra and
remote control of instrument.
Long term leases are available for periods
ranging from one through five years via NITON
Financial Services. NITON provides training for
all users, regardless of whether they lease or
purchase the instruments. The full-day (8-hr)
class covers both radiation safety and instrument
operation and is conducted in metropolitan areas
across the country on an ongoing basis. This
training is offered at no charge, and is available
for both customers, as well as those interested in
learning more about the technology. Additional
on-site operational training is available at no
charge for customers from local Sales Offices
upon instrument delivery. NITON offers various
extended warranty options that can be discussed
with NITON or your local NITON representative
at the time of the instrument purchase.
Reagents and supplies. The only consumable
supply is the sample baggie, which NITON sells
for $0.10 each. NITON used a toaster oven (<
$100) in the test to dry the samples.
Laboratory Costs
Sample Shipment
The costs of shipping samples to the laboratory
included overnight shipping charges as well as labor
charges associated with the various organizations
involved in the shipping process.
• Labor. This cost element included all of the tasks
associated with shipping the samples to the
NLLAP laboratory. Tasks included packing the
shipping coolers, completing the chain-of-
custody documentation, and completing the
shipping forms. The estimate to complete this
task ranged from 2 to 4 h, at $50 per hour.
• Overnight shipping. The overnight express
shipping service cost was estimated to be $50 -
100 for two boxes of samples.
Labor, Equipment, and Waste Disposal
The labor quotes from commercial analytical
laboratories that offered to perform the analysis for
this verification test ranged from $20 to $30 per
sample, with turnaround time estimates ranging from
7 to 14 days. (Some laboratories can provide a 1-2
day turnaround, but the data report is limited and the
cost is usually higher.) The quotes were dependent
on many factors, including the perceived difficulty of
the sample matrix, the current workload of the
laboratory, data packaging, and the competitiveness
of the market. This rate was a fully loaded analytical
cost that included equipment, labor, waste disposal,
and report preparation. The cost for DataChem to
analyze samples for this verification test was $30 per
sample.
Cosf Assessmenf Summary
An overall cost estimate for use of the XLt 700
spectrum analyzer versus use of the NLLAP-
laboratory was not made because of the extent of
variation in the different cost factors, as outlined in
Table 11. The overall costs for the application of any
technology would be based on the number of
samples requiring analysis, the sample type, and the
site location and characteristics. Decision-making
factors, such as turnaround time for results, must also
be weighed against the cost estimate to determine the
value of the field technology's providing immediate
answers versus the laboratory's provision of
reporting data within 18 days of receipt of samples.
Miscellaneous Factors
The following are general observations regarding the
field operation and performance of the XLt 700 XRF
24
-------
spectrum analyzer:
The spectrum analyzer is provided with two
rechargeable lithium-ion batteries. The batteries
were swapped every 4 hours and recharging the
battery took approximately 2 hours.
The NITON analyst was ready for the first set of
samples within 30 min of arriving on site.
• The NITON analyst took four readings on the
front and back of each dust wipe, for a total of
eight readings per wipe. The average
concentration from the four readings on the front
of the wipe were averaged with the average of
the four readings on the back of a wipe to give
the final result. NITON recommends performing
all eight readings for the most accurate results.
Fewer measurements may be sufficient for initial
screening if time is an issue. However, such was
not verified in this round of testing.
• This spectrum analyzer can be used to detect and
quantify multiple metals, although the spectrum
analyzer's performance for lead is the only metal
that was verified in this test.
• While the x-ray tube in the XLt 700 spectrum
analyzer was approximately 3 months old, decay
and half-life time corrections are not relevant
factors for an x-ray tubes. Time to complete each
measurement was 60 seconds.
The NITON analyst ran QC samples at the start
and periodically throughout the day to confirm
that the spectrum analyzer was working within
normal parameters. The samples were part of a
suite provided by ORNL as part of the pre-test.
They were the same samples that were used as
test samples in the study and can be obtained
directly from the American Industrial Hygiene
Association (AIHA), for a price of $200 per
group of four samples. More information can be
obtained by contacting the ELPAT Program,
Laboratory Accreditation Department, at AIHA;
(703) 849-8888
The dust in all samples was smoothed out to a
thin layer on the wipe. All wipes were folded
and dried (toaster oven at 250° F for 20 minutes)
so that they fit the size of the sample holder and
such that it was a flat as possible for the most
accurate reading.
The spectrum analyzer contains an x-ray tube.
Though regulatory demands are reduced as
compared to those encountered with
isotope-based systems, x-ray source registration
is still typically required and varies by state.
NITON offers contact information and guidance
with spectrum analyzer purchase or lease.
Summary of Performance
A summary of performance is presented in Table 12.
Note that performance is based on the specific
protocols employed for this verification test. If
different testing protocols are used, different
performance results may be obtained.
The verification test found that the XLt 700 spectrum
analyzer was relatively simple for a trained analyst to
operate in the field, requiring less than an hour for
initial setup. The sample throughput of the XLt 700
was 45-50 samples per day with two operators. The
overall performance of the XLt 700 for the analysis
of lead in dust wipe samples was characterized as
slightly biased low but within acceptable levels,
precise, and in good linear agreement with the
NLLAP laboratory data.
ORNL and ETV remind the reader that, while the
ETV test provides valuable information in the form
of a snapshot of performance, state, tribal, or federal
requirements regarding the use of the technologies
(such as NLLAP recognition for analysis of samples
where required) need to be followed.
25
-------
Table 12. Performance Summary for NITON's XLt 700 XRF Spectrum Analyzer
Feature/parameter
Precision : average RSD
Accuracy: average % recovery
Positive results on "detectable
blank" samples (< 2 ^g/wipe)
False positive results
False negative results
Comparison with slope
laboratory results intercept
jig/wipe samples) correlation
coefficient
Overall evaluation
Completeness
Size and Weight
Sample throughput (2 analysts)
Power requirements
Training requirements
Cost
Waste generated
Performance summary
UC Samples3
11%
97%
n/a
DataChem
Oof 30
(0%)
DataChem
23 of 30
(77%)
0.995
XLt 700
8 of 37
(22%)
XLt 700
10 of 23
(43%)
4.775
0.999
- Statistically significant negative
bias but within the acceptable bias
range
- Precise
- Strong linear relationship to the
NLLAP lab results
- Higher number of fn results
- Few fp results
ELPAT Samples
11%
101%
0 of 20 samples
DataChem
2 of 12
(17%)
DataChem
7 of 28
(25%)
XLt 700
lof 12
(8%)
XLt 700
8 of 28
(29%)
0.977
3.076
0.999
- Statistically significant negative
bias but within the acceptable bias
range
- Precise
- Strong linear relationship to the
NLLAP lab results
- Higher number of fn results
- Few fp results
100% of 160 dust wipe samples
9.75" x 10.5" x 3.75"
, 3.0 Ibs
45 - 50 samples/day
7 V rechargeable battery (Lithium-ion)
One day instrument-specific training including radiation safety.
Purchase: $20,000 - $40,000
Reagents/Supplies: $0.10 per sample
none
(a) DataChem Laboratories and XLt 700 measured two different sets of UC samples. Both sets have 20 samples
for each of the three target levels of 40, 250 and 400 ^g/wipe with sample concentrations distributed above and
below the target levels. The concentration distributions are different for the DataChem and Xlt 700 analyzed
samples.
26
-------
Section 6 — References
American Society for Testing and Materials. 1996. "Specification E1792-96a: Standard Specification for
Wipe Sampling Materials for Lead in Surface Dust" in ASTM Standards on Lead Hazards Associated with
Buildings. ASTM: West Conshohocken, PA.
American Society for Testing and Materials. 1998. "Practice E1644: Standard Practice for Hot Plate
Digestion of Dust Wipe Samples for the Determination of Lead" in ASTM Standards on Lead Hazards
Associated with Buildings. ASTM: West Conshohocken, PA.
Ashley, K., K. Mapp, and M. Millson. 1998. "Ultrasonic Extraction and Field-Portable Anodic Stripping
Voltammetry for the Determination of Lead in Workplace Air Samples." AIHA Journal. 59(10), 671-679.
Code of Federal Regulations. 2001. "Identification of Dangerous Levels of Lead", Final Rule, 40 CFR Part
745, January.
Draper, N. R., and H. Smith. 1981. Applied Regression Analysis. 2nd ed. John Wiley & Sons, New York.
EPA (U.S. Environmental Protection Agency). 1996. "Method 3050B-1: Acid Digestion of Sediment, Sludge,
and Soils." In Test Methods for Evaluating Solid Waste: Physical/ Chemical Methods, Update II. SW-846.
U.S. Environmental Protection Agency, Washington, D.C., December.
EPA (U.S. Environmental Protection Agency). 1996. "Method 6010B-1: Inductively Coupled Plasma-Atomic
Emission Spectrometry." In Test Methods for Evaluating Solid Waste: Physical/ Chemical Methods, Update II.
SW-846. U.S. Environmental Protection Agency, Washington, D.C., December.
Keith, L.H., G. L. Patton, D.L. Lewis and P.O. Edwards. 1996. Chapter I: Determining What Kinds of
Samples and How Many Samples to Analyze, pp. 19. In Principles of Environmental Sampling. Second
Edition. Edited by L. H. Keith, ACS Professional Reference Book, American Chemical Society, Washington,
DC.
ORNL (Oak Ridge National Laboratory). 1998. Quality Management Plan for the Environmental Technology
Verification Program's Site Characterization and Monitoring Technologies Pilot. QMP-X-98-CASD-001,
Rev. 0. Oak Ridge National Laboratory, Oak Ridge, Tenn., November.
ORNL (Oak Ridge National Laboratory). 2001. Technology Verification Test Plan: Evaluation of Field
Portable Measurement Technologies for Lead in Dust Wipes. Chemical Sciences Division, Oak Ridge National
Laboratory, Oak Ridge, Tenn., November.
Song, R., P. Schlecht, and K. Ashley. 2001. "Field Screening Test Methods: performance criteria and
performance characteristics." Journal of Hazardous Materials. 83, 29-39.
27
-------
Appendix
NITON'S XLt 700 XRF Results Compared with Laboratory Results
Sample
Analysis
Order
106
138
101
25
129
100
137
84
72
111
91
121
32
102
125
132
55
54
35
150
110
82
145
73
124
8
61
40
65
148
11
159
Source
EL PAT
EL PAT
EL PAT
EL PAT
EL PAT
EL PAT
EL PAT
EL PAT
EL PAT
EL PAT
EL PAT
EL PAT
EL PAT
EL PAT
EL PAT
EL PAT
EL PAT
EL PAT
EL PAT
EL PAT
EL PAT
EL PAT
EL PAT
EL PAT
EL PAT
EL PAT
EL PAT
EL PAT
EL PAT
EL PAT
EL PAT
EL PAT
Rep
1.2346+31
NITON XLt 700 XRF
Result
Hg/wipe
<10.0
<10.0
<10.0
<10.0
<10.0
<10.0
<10.0
<10.0
<10.0
<10.0
<10.0
<10.0
<10.0
<10.0
<10.0
<10.0
<10.0
<10.0
<10.0
<10.0
21.3
16.3
24.3
17. 7
14.6
26.5
16.9
20.3
30.8
34.0
25.3
30.5
Estimated
|ig/wipe
1.3
1.3
1.3
1.3
1.3
1.3
1.3
1.3
1.3
1.3
1.3
1.3
1.3
1.3
1.3
1.3
1.3
1.3
1.3
1.3
16.9
16.9
16.9
16.9
17.6
17.6
17.6
17.6
29.8
29.8
29.8
29.8
DataChem
Result
Hg/wipe
<20
<20
<20
<20
<20
<20
<20
<20
<20
<20
<20
<20
<20
<20
<20
<20
<20
<20
<20
<20
<20
<20
<20
<20
30
<20
<20
<20
33
26
28
28
Estimated
Hg/wipe
1.3
1.3
1.3
1.3
1.3
1.3
1.3
1.3
1.3
1.3
1.3
1.3
1.3
1.3
1.3
1.3
1.3
1.3
1.3
1.3
16.9
16.9
16.9
16.9
17.6
17.6
17.6
17.6
29.8
29.8
29.8
29.8
-------
Sample
Analysis
Order
156
107
47
45
87
58
51
86
67
13
60
135
139
6
41
77
109
152
154
10
2
14
5
93
20
66
142
134
43
105
76
21
28
89
23
143
Source
UC LAB
UC LAB
UC LAB
UC LAB
UC LAB
UC LAB
UC LAB
UC LAB
UC LAB
UC LAB
UC LAB
UC LAB
UC LAB
UC LAB
UC LAB
UC LAB
UC LAB
UC LAB
UC LAB
UC LAB
EL PAT
EL PAT
EL PAT
EL PAT
EL PAT
EL PAT
EL PAT
EL PAT
EL PAT
EL PAT
EL PAT
EL PAT
EL PAT
EL PAT
EL PAT
EL PAT
Rep
1.2346+35
NITON XLt 700 XRF
Result
|lg/wipe
42.3
44. 0
38.7
39.8
38.4
37.1
41.5
32 . 7
37.1
50.8
48.4
33.4
35.3
44. 0
47. 7
43.2
44.2
45.4
42 .2
44. 9
33.1
53.7
50.4
46.6
46.4
50.5
64.5
56.9
43.8
50.6
46.2
53.7
57. 9
55.0
50.3
60.3
Estimated
|ig/wipe
37.9
42.2
36.8
40.6
41.4
36.4
37.9
36.8
35.2
35.1
39.6
35.4
37.6
41.3
39.9
41.6
41.6
40 .4
37 .2
44 . 0
41.3
41.3
41.3
41.3
49.0
49.0
49.0
49.0
49. 1
49.1
49. 1
49.1
58.6
58.6
58.6
58.6
DataChem
Result
|j,g/wipe
3 . 9416 + 71
Estimated
|ig/wipe
40.4
44.3
43.1
38.3
37.8
38.7
38.9
38.9
42.3
36.4
36.8
41.4
38.2
45.8
45. 7
41. 1
41. 1
44.3
40.2
38.1
41.3
41.3
41.3
41.3
49.0
49.0
49.0
49.0
49. 1
49. 1
49. 1
49. 1
58.6
58.6
58.6
58.6
29
-------
Sample
Analysis
Order
26
122
78
15
119
56
146
3
92
114
71
147
127
96
75
12
97
64
36
59
80
95
44
33
103
90
136
34
88
48
52
9
16
85
42
115
151
27
70
50
Source
EL PAT
EL PAT
EL PAT
EL PAT
EL PAT
EL PAT
EL PAT
EL PAT
EL PAT
EL PAT
EL PAT
EL PAT
EL PAT
EL PAT
EL PAT
EL PAT
EL PAT
EL PAT
EL PAT
EL PAT
UC LAB
UC LAB
UC LAB
UC LAB
UC LAB
UC LAB
UC LAB
UC LAB
UC LAB
UC LAB
UC LAB
UC LAB
UC LAB
UC LAB
UC LAB
UC LAB
UC LAB
UC LAB
UC LAB
UC LAB
Rep
1.2346+39
NITON XLt 700 XRF
Result
|lg/wipe
90.3
86.8
75.6
88.7
139.0
122 . 0
112.0
139.0
152.0
159.0
142 . 0
158.0
208.0
204.0
221. 0
200.0
217.0
244. 0
188.0
251.0
251.0
259.0
208.0
237.0
243.0
218.0
228.0
240.0
188.0
189.0
227. 0
222.0
265.0
225.0
209.0
265.0
250.0
231.0
214. 0
223.0
Estimated
|ig/wipe
88.0
88.0
88.0
88.0
117. 0
117. 0
117. 0
117. 0
162.3
162.3
162.3
162.3
201.6
201.6
201.6
201.6
239.0
239.0
239.0
239.0
265.5
260.6
234.6
272.7
249.5
265.5
237.9
236.2
252.8
226.3
242 .3
248.9
244. 0
242 .3
234.6
270.5
233.5
237.9
234.0
244. 5
DataChem
Result
|j,g/wipe
82
83
79
100
120
120
120
110
150
160
150
160
200
190
200
220
230
250
250
230
230
220
220
210
230
230
220
240
240
210
210
220
210
240
210
240
240
240
220
200
Estimated
|ig/wipe
88.0
88.0
88.0
88.0
117. 0
117. 0
117. 0
117. 0
162.3
162.3
162.3
162.3
201.6
201.6
201.6
201.6
239.0
239.0
239.0
239.0
256.7
226.8
237.9
242.9
255.6
260.0
242.3
262 .2
258.3
236.8
225.2
247.3
232.9
266.1
242.3
273.8
258.3
258.3
246. 7
228.5
30
-------
Sample
Analysis
Order
37
131
1
158
144
62
157
68
30
113
141
79
118
108
22
53
57
4
38
155
130
29
153
149
39
7
112
49
81
128
17
63
83
31
133
104
Source
EL PAT
EL PAT
EL PAT
EL PAT
EL PAT
EL PAT
EL PAT
EL PAT
UC LAB
UC LAB
UC LAB
UC LAB
UC LAB
UC LAB
UC LAB
UC LAB
UC LAB
UC LAB
UC LAB
UC LAB
UC LAB
UC LAB
UC LAB
UC LAB
UC LAB
UC LAB
UC LAB
UC LAB
EL PAT
EL PAT
EL PAT
EL PAT
EL PAT
EL PAT
EL PAT
EL PAT
Rep
1.2346+35
NITON XLt 700 XRF
Result
|lg/wipe
257.0
227.0
217. 0
228.0
239.0
218.0
253.0
276.0
430.0
313.0
359.0
423.0
335.0
337.0
316.0
347.0
333.0
412 . 0
323.0
386.0
381.0
336.0
370.0
392.0
412.0
383.0
297.0
360.0
392.0
409.0
435.0
381.0
445.0
463.0
446. 0
448. 0
Estimated
|ig/wipe
256.7
256.7
256.7
256.7
260.8
260.8
260.8
260.8
411.0
370.6
422.1
428.2
403.8
366.8
366.8
391.1
415. 5
408.8
377.3
383.9
414. 9
370.6
385.0
402.2
406.0
384.5
373.4
361.2
408. 7
408. 7
408.7
408. 7
418. 1
418. 1
418. 1
418. 1
DataChem
Result
|j,g/wipe
2.906+107
Estimated
|ig/wipe
256.7
256.7
256.7
256.7
260.8
260.8
260.8
260.8
414. 9
399.4
432.0
435.9
374.0
392.8
369.0
400.0
365.7
386.1
403.3
400.5
427. 1
377.3
359.6
417. 1
419. 9
408.8
375.6
395.0
408. 7
408. 7
408.7
408. 7
418. 1
418. 1
418. 1
418. 1
31
-------
Sample
Analysis
Order
116
98
140
69
117
18
120
19
99
123
126
46
94
160
24
74
Source
EL PAT
EL PAT
EL PAT
EL PAT
EL PAT
EL PAT
EL PAT
EL PAT
EL PAT
EL PAT
EL PAT
EL PAT
EL PAT
EL PAT
EL PAT
EL PAT
Rep
1.2346+15
NITON XLt 700 XRF
Result
|lg/wipe
629.0
491.0
513.0
506.0
562.0
447 . 0
607.0
451.0
708.0
797.0
623.0
770 . 0
1387.0
1545 . 0
1377.0
1523.0
Estimated
|ig/wipe
561.9
561.9
561.9
561.9
564.7
564.7
564. 7
564.7
805.1
805.1
805.1
805.1
1482.6
1482.6
1482.6
1482.6
DataChem
Result
|j,g/wipe
580
540
560
540
560
560
570
530
760
770
760
740
1500
1500
1500
1400
Estimated
|ig/wipe
561.9
561.9
561.9
561.9
564.7
564.7
564 .7
564.7
805.1
805.1
805.1
805.1
1482.6
1482.6
1482.6
1482.6
32
------- |