United States Office of Research and EPA/600/R-02/055
Environmental Protection Development September 2002
Agency Washington, D.C. 20460
v>EPA Environmental Technology
Verification Report
Lead in Dust Wipe Measurement
Technology
NITON Corporation
X-Ray Fluorescence Spectrum
Analyzer, XL-700
on\l
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
XL-700 Series XRF Spectrum Analyzer
NITON Corporation
900 Middlesex Turnpike, Bldg. 8 PHONE: +1(978) 670-7460
Billerica, MA 01821 FAX: +1(978) 670-7430
www.niton.com
sales@niton.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 six technology areas under ETV. In this verification test, ORNL
evaluated the performance of lead in dust wipe measurement technologies. This verification statement
provides a summary of the test results for NITON's XL-700 Series x-ray fluorescence (XRF) spectrum
analyzer.
EPA-VS-SCM-52
The accompanying notice is an integral part of this verification statement.
September 2002
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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 Capitol Community Technical College in Hartford, CT, from November 5
through November 9, 2001. The vendors of commercially-available, field portable technologies blindly
analyzed 160 dust wipe samples containing known amounts of lead, ranging in concentration from <2 to
1,500 |-lg/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 |_lg/ft2 for floors, 250 |_lg/ft2 for window sills,
and 400 |-lg/ft2 for window troughs. The samples included wipes newly-prepared and archived from the
Environmental Lead Proficiency Analytical Testing Program (ELPAT). These samples were prepared
from dust collected in households in North Carolina and Wisconsin. Also, newly-prepared 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
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. 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— NITON
Corporation, XL-700 Series X-Ray Fluorescence Spectrum Analyzer, EPA/600/R-02/055. NITON's XL-
300 Series XRF was also evaluated in the test and a separate report has been prepared (Environmental
Technology Verification Report: Lead in Dust Wipe Detection Technology— NITON Corporation, XL-
300 Series X-Ray Fluorescence Spectrum analyzer, EPA/600/R-02/059).
TECHNOLOGY DESCRIPTION
The XL-700 Series spectrum analyzer is an energy dispersive x-ray fluorescence (EDXRF) spectrometer
that uses one to three sealed, radioisotope sources 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. In this test, the exact model used was XL-723S with two
sources (10 mCi Cd-109 and 14 mCi Am-241). The Cd-109 source, the source which was used for the
lead analysis, was approximately 11 months old. The energy of each x-ray detected identifies a particular
element present in the sample, and 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, Big-Area Silicon
PIN-diode (BASF) detector. Signals from the BASF 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 XL-700 Series XRF spectrum analyzer reporting limits were
4.9 to 6.1 |_lg/wipe during the verification test.
VERIFICATION OF PERFORMANCE
The following performance characteristics of the XL-700 Series XRF were observed:
Precision: Precision, based on the average percent relative standard deviation (RSD), was 8% for both the
UC and ELPAT sample analyses. A technology's performance is considered very precise if the average
RSD is less than 10%, but acceptable as long as the average RSD is less than 20%.
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 107% for the UC samples and 119% for the ELPAT samples. The
high bias was statistically significant for both the UC and ELPAT samples, but it was well within the
acceptable bias range of 100% ± 25%. For the NLLAP laboratory results, the average percent recovery
EPA-VS-SCM-52 The accompanying notice is an integral part of this verification statement. September 2002
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values were 91% and 98%, respectively, for the UC and ELPAT samples. The negative bias for both
the UC and ELPAT samples was statistically significant.
Comparability: A comparison of the XL-700 results and the NLLAP-recognized laboratory
results was performed for all samples (ELPAT and UC) that were reported above 20 |_lg/wipe. The cor-
relation coefficient (r) for the comparison of the UC samples was 0.999 [slope (m) = 1.206, intercept =
-3.290], and for the ELPAT samples was also 0.999 [m = 1.112, intercept = 13.283]. While the
slopes for both the ELPAT and UC samples were statistically different than 1.00, correlation
coefficients greater than 0.990 indicate strong linear agreement with the NLLAP laboratory data.
Detectable blanks: All twenty samples, prepared at concentrations < 2 |_lg/wipe, were reported
correctly as less than reporting limits, with results reported by the XL-700 ranging from < 4.9 to < 6.1
|-lg/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 XL-700 reported 21 of a possible 34 fp results, while the NLLAP laboratory did not report any fp
results. For the ELPAT samples, the XL-700 reported 6 of a possible 12 fp results, while the NLLAP
laboratory reported two.
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 XL-700 reported 2 of a possible 26 m results, while the NLLAP laboratory reported 23 of a possible 30
m results. For the ELPAT samples, the XL-700 reported 2 of a possible 28 fn results, while the NLLAP
laboratory reported seven.
Completeness: Completeness is defined as the percentage of measurements that are judged to be usable
(i.e., the result is not rejected). An acceptable completeness rate is 95% or greater. The XL-700 Series
spectrum analyzer generated results for all 160 dust wipes samples, for a completeness of 100%.
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. A single analyst (a NITON expert) analyzed all
160 samples in four 12-hour days. Eight measurements were taken for each wipe, for a total of 320
measurements. For the first two days of testing, the analyst used a 60 second count time and analyzed
25 to 30 samples per day. For the last two days of testing, the analyst used a 30 second count time and
analyzed 50 to 60 samples per day. Replicate results analyzed using the two count times were not
statistically different.
EPA-VS-SCM-52 The accompanying notice is an integral part of this verification statement. September 2002
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Overall Evaluation: The overall performance was characterized as being biased slightly high (but
within the limits of acceptable bias), very precise, and in good linear agreement to an NLLAP-
laboratory results. The verification team found that the XL-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
clearance 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: EPA 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-52
The accompanying notice is an integral part of this verification statement.
September 2002
-------
EPA/600/R-02/055
September 2002
Environmental Technology
Verification Report
Lead in Dust Wipe Measurement
Technology
NITON Corporation
X-Ray Fluorescence Spectrum
Analyzer, XL-700
By
Amy B. Dindal
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
The U.S. Environmental Protection Agency (EPA), through its Office of Research and Development (ORD),
funded and managed, through Interagency Agreement No. DW89937854 with Oak Ridge National
Laboratory, the verification effort described herein. 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 2
Sample Analysis 2
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
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
Section 5 — Technology Evaluation 17
Objective and Approach 17
Precision 17
Accuracy 17
Comparability 18
False Positive/False Negative Results 19
iii
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Completeness 22
Sample Throughput 22
Ease of Use 22
Cost Assessment 22
XL-700 Series XRF Costs 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's XL-700 series XRF spectrum analyzer 2
2. Distribution of both UC and ELPAT sample concentrations 7
3. Plot of DataChem reported values versus estimated values, shown for concentrations less than 500
|-lg/wipe 12
4. False negative probabilities for DataChem average concentrations at a target concentration level of 40
|-lg/wipe 14
5. False negative probabilities for DataChem average concentrations at a target concentration level of
250 |_lg/wipe 15
6. False negative probabilities for DataChem average concentrations at a target concentration level of
400 |_lg/wipe 15
7. Plot of the average XL-700 concentration versus the average DataChem concentrations for all samples
(n=21), shown for ELPAT and UC concentrations less than 500 |_lg/wipe 19
8. Comparison of the false negative probabilities for the NITON XL-700 and DataChem average
concentrations at a target concentration level of 40 |_lg/wipe 20
9. Comparison of the false negative probabilities for the NITON XL-700 and DataChem average
concentrations at a target concentration level of 250 |_lg/wipe 21
10. Comparison of the false negative probabilities for the NITON XL-700 and DataChem average
concentrations at a target concentration level of 400 |_lg/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 XL-700 17
7. Accuracy of XL-700 17
8. Linear regression constants for the plots of the XL-700 versus the estimated values and versus the
DataChem average measurements 18
9. False Positive/False Negative Error Rates for XL-700 Measurements 20
10. Summary of the Linear Regression and Recovery Data for the XL-700 Response versus the
Estimated Concentrations 22
11. Estimated analytical costs for lead dust wipe samples 23
12. Performance Summary forNITON's XL-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: Patricia Lindsey, Capitol Community
Technical College, 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
John Schwemberger for serving as peer reviewers of this report. The authors also acknowledge the
participation of NITON Corporation, in particular, Mark Gardner, 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
Environmental Sciences Division Chemical Sciences Division
National Exposure Research Laboratory P.O. Box 2008
P.O. Box 93478 Oak Ridge, TN 37831-6120
Las Vegas, Nevada 89193-3478 (865) 574-4871
(702) 798-2332 jenkinsra(g),ornl.gov
koglin.eric@epa.gov
For more information on NITON's XL-700 Series XRF Spectrum Analyzer, contact:
Jonathan J. Shein
NITON Corporation
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
AMS Advanced Monitoring Systems Center, ETV
ASTM American Society for Testing and Materials
BASF Big-Area Silicon PIN-diode detector
CDC Centers for Disease Control and Prevention
CFR Code of Federal Regulations
CL clearance level for lead of 40, 250, or 400 |_lg/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
NERL National Exposure Research Laboratory, U.S. EPA
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
SD standard deviation
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 Hartford, Connecticut, from November
5 through November 9, 2001. The performance of
NITON's XL-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 performance of NITON's XL-300 Series XRF
has been reported in a separate verification report.
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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.
idit'lj:
tatfeB
K-Ii'H
General Technology Description
The XL-700 Series
spectrum analyzer is an ifTTTl
energy dispersive x-ray
fluorescence (EDXRF)
spectrometer that uses
one to three sealed,
radioisotope sources to
excite characteristic x-
rays of a test sample's
constituent elements.
These characteristic x-
rays are continuously
detected, identified, and
quantified by the
Figure 1. NITON's XL-
700 series XRF spectrum
analyzer.
spectrometer during sample analysis. In this test,
the exact model used was XL-723S with two
sources (10 mCi Cd-109 and 14 mCi Am-241),
although only the Cd-109 source (-11 months
old) was used for the analysis of lead. Stated
simply, the energy of each x-ray detected
identifies a particular element present in the
sample, and 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, Big-Area Silicon
PIN-diode (BASF) detector. Signals from the
BASF 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
For this verification test, the dust on the wipes had
to be distributed more evenly across the wipe prior
to analysis. This step is only required for
prepared samples where the lead loading is
clumped in discrete areas. The sample was then
folded five times such that it was the proper size
(1" x 1.5") for the XRF window.
For this test, the samples were dried for 20
minutes at 250 °F in a toaster oven prior to testing.
Alternatively, the sample could be exposed
overnight to ambient temperature and humidity,
but the toaster oven was used in this case to
expedite the process. After oven drying, the dried
sample sat in ambient air for at least 5 minutes
before reading.
The dried, folded wipe was placed in a 2" x 2"
plastic bag (NITON part number 187-471 or
equivalent) and labeled. (To eliminate the
potential for cross-contamination of samples,
plastic bags should never be re-used.) 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) and analyzed.
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.
The dust wipe was placed in the sample holder at
the number-one position and a 60 seoncd (s)
measurement was taken. The sample was then
placed in the number two position and another 60
s 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.
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For the first two days of testing, the sample samples 49-160 were analyzed using 30 second
analyses were taking longer than expected (25-30 count time. (See Appendix for data.)
samples per day). The NITON analyst believed
that the instrument could achieve adequate The sensitivity of the measurements is a function
sensitivity with a shorter count time, so he elected of the age of the detector source, so modification
to reduce the run-times to 30 seconds. Samples 1- of count times can be made, depending on the
48 were analyzed using 60 second count time, and user's needs.
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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 Capitol
Community Technical College in Hartford,
Connecticut. The test was conducted in the
basement of a classroom building. 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 68 °F and 32%, 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 |-lg/ft2 for floors, 250
|~lg/ft2 for window sills, and 400 |-lg/ft2 for window
troughs that are outlined in 40 CFR Part
745.227(e)(8)(viii) (CFR, 2001).
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 (described in
the next section), and (3) the logistical and
economic resources necessary to operate the
technology. Secondary objectives for this
verification were 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 the samples analyzed in this verification test
were prepared gravimetrically. At the time of the
test, both of the wipes utilized in the test
(PaceWipe™ and Aramsco LeadWipe™) were on
the list of wipes recommended for lead testing by
the American Society for Testing and Materials
(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, thereby
making it difficult to separate instrument/method
variability and sampling variability. The availability
of we 11-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
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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 were
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 |_lm. A PaceWipe™
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 PaceWipe was then transferred to a flat plastic
board to await the dust. After weighing a 0.1000 ±
0.0005 g portion of dust on weighing paper, the pre-
weighed dust was gently tapped out onto the
PaceWipe. 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
accredited 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 |_lg/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 |_lg/wipe samples, and NIST SRM 2710 was used
to prepare the 250 and 400 |_lg/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) were 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 for
Method 3 05 OB and Method 601 OB) 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 by the 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
- 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 these 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
A total of 160 samples were analyzed in the
verification test. Figure 2 is a plot containing the
distribution of the sample concentrations that were
analyzed in this study. Twenty samples were
prepared by the University of Cincinnati at +/- 10%
of each of the three clearance levels (3 test levels x
20 samples = 60 samples total). Research Triangle
Institute prepared 20 "blanks" at lead concentrations
< 2 |_lg/wipe. These samples are noted as such in
Figure 2. The remaining samples in Figure 2 are
ELPAT samples. For most of the ELPAT samples,
four samples were analyzed at each concentration
level (16 test levels x 4 samples each = 64 samples
total). There were two concentration levels (at 49
and 565 |_lg/wipe) where eight samples were
analyzed. While the set of samples at each
concentration level were prepared using
homogeneous source materials and an identical
preparation procedure, ELPAT samples cannot be
considered true "replicates" because each sample
was prepared individually. However, these samples
represent four samples prepared similarly at a
specified target concentration, with an estimated
value calculated from more than 100 analyses of
similarly prepared samples.
Sample Randomization
The samples were packaged in 20-mL plastic
scintillation vials and labeled with a sample
identifier. Each participant received the same suite
of samples, 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
-------
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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. Comparison to the gravimetric values
reveals 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). The field technology can still
have acceptable bias with an average percent
recovery in the interval of 75% to 125%. Bias
within the acceptable range can usually be corrected
to 100% by modification of calibration methods.
Comparability
Comparability refers to how well the field tech-
nology and conventional 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
were 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).
Acceptable r values are 0.990 or greater. 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
|J,g/wipe, below the anticipated reporting limits of
both the field technologies 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 (m) 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. For
example, if the technology reports the sample
concentration to be 35 |_lg/wipe, and the true
concentration of the sample is 45 |_lg/wipe, the
technology's result would be considered a m at the
40 |_lg/wipe clearance level. Accordingly, if the
technology reports the result as 45 |_lg/wipe and the
true concentration is 35 |_lg/wipe, the technology's
result would be a fp at the 40 |_lg/wipe clearance
level.
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
|J,g/wipe, and estimate the probability of the field
technology reporting a fp or fn result. For each
clearance level, the probabilities of fn 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/fn evaluation also included a comparison to
the ELPAT sample results. The "estimated" value
for the UC and ELPAT samples are defined
differently. 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/fn 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.
Completeness
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. Sample
throughput 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?
Cost
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.
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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
(|_lg/wipe)
<20
<20
41
44
190
210
440
450
<20
<20
25
38
150
200
250
310
Estimated
Cone
(|_lg/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.
The results are also shown graphically in Figure 3.
The average percent recovery for the ELPAT
samples was 98%, while the average for the UC
samples was 91%. Both Table 2 and Figure 3
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.
The negative bias observed with the UC and the
ELPAT samples was statistically significant. 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
|-lg/wipe), DataChem reported 71 (99%) within the
acceptable ranges of values.
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 |-lg/wipe. In addition, DataChem
reported seven of the eight samples with estimated
concentrations of either 16.9 |-lg/wipe or 17.6
|-lg/wipe as less than their reporting limit of 20
|-lg/wipe and only one was incorrectly reported as 30
|-lg/wipe.
11
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Table 2. Summary of DataChem Percent Recovery Values by Sample Source
Statistic
n a
average % recovery
standard deviation
minimum % recovery
maximum % recovery
ELPAT
72
98
9
81
143
uc
60
91
o
J
86
102
a excludes estimated values <20 |_ig/wipe (n=28)
S/j
s
500 n
400 -
300 -
200 -
6 100 -I
D
D ELPAT (n=72)
• Univ of Cinci (n=60)
100 200 300 400
Estimated value (ug/wipe)
500
Figure 3. Plot of DataChem reported values versus estimated values, shown for concentrations
less than 500 |ig/wipe.
Table 3. Summary of DataChem Precision Estimates by Sample Source
Sample Source
ELPAT
UC
UC preparation
n
18 a
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
c 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 |_lg/wipe, for a
total of 60 UC samples. The ELPAT samples
covered a wider range of concentrations. There was
a total of 40 ELPAT samples that 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. 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 4, 5, and 6 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
must be 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
|-lg/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 4, 5, and 6, 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 4, 5% FN probability (y = 0.05) corresponds
to a "true" lead concentration of 46 |_lg/wipe
(meaning if the true concentration of the sample is
46 |_lg/wipe, there is only a 5% chance/risk that
DataChem will report the value as < 40 |_lg/wipe.)
By plotting DataChem's measured values versus the
estimated concentrations, the equations of the linear
regression lines can be calculated for each of the
three CL. 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 |_lg/wipe is biased low and will have
a true concentration of > 40 (41.8 |_lg/wipe, using the
linear regression equation in Table 5). A true
concentration of 40 |_lg/wipe for a UC sample would
correspond to a reported value rounded to the nearest
whole number of 37 |_lg/wipe (see Table 5). For an
ELPAT sample, a true concentration of 40 |_lg/wipe
corresponds to a DataChem reported value of 40
|J,g/wipe, because the negative bias was not as large
for the ELPAT samples. Estimates of the reported
concentration at the 250 and 400 |_lg/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 a 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 |_lg/wipe
Oof 9
Oof 4
5 of 11
lof 12
250 |J,g/wipe
Oof 11
2 of 8
9 of 9
5 of 8
400 |J,g/wipe
Oof 10
OofOb
9 of 10
lof 8
Total
Oof 30
2 of 12
23 of 30
7 of 28
a CL = clearance level
b Because all eight ELPAT values were above 400 |_ig/wipe,
no samples were available to assess fp results at this level.
True Pb Concentration (ug/wipe)
Figure 4. 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 5. False negative probabilities for DataChem average concentrations at a target
concentration level of 250 |_ig/wipe.
0.0 -I
400
410 420 430 440 450 460 470 480 490 500
True Pb Concentration (ug/wipe)
Figure 6. False negative probabilities for DataChem average concentrations at a
target concentration level of 400 |ig/wipe.
15
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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 |_lg/wipe
UC
20
1.021
-3.673
0.884
93%
4%
37
l-ig/wipe
ELPAT
16
1.612
-6.182
0.840
101%
13%
40
l-ig/wipe
250 |J,g/wipe
UC
20
0.829
18.557
0.879
90%
3%
226
l-ig/wipe
ELPAT
16
0.578
90.826
0.549
96%
9%
234
l-ig/wipe
400 |J,g/wipe
UC
20
0.736
67.649
0.861
91%
3%
362
l-ig/wipe
ELPAT
8
2.394
-575.771
0.492
100%
5%
382
l-ig/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 XL-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 XL-
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 XL-700 reporting
limits (4.9 to 6.1 |_lg/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 XL-700's average
RSD value was 8%, with a range from 1 to 20%,
indicating that the XL-700 measurements were very
precise (Table 6). For the UC samples, 20 samples
were analyzed at three target concentration levels of
40, 250, and 400 |_lg/wipe. The average precision of
the UC sample measurements by the XL-700 was
8% RSD. With the expectation that UC was to
prepare the samples as close to the target
concentrations as possible, the allowable variability
was 10% RSD. The actual variability of the UC
preparation process was an average of 5% RSD.
Accuracy
Accuracy represents the closeness of the XL-700's
measured concentrations to the estimated content of
spiked samples. One measure of accuracy is the
number of results for the ELPAT samples that were
reported within the individual acceptance ranges that
have been established for those samples. Of the 80
ELPAT samples, the XL-700 reported 67 of the
results (84% of the total) within the acceptance
ranges. All 13 that were outside the range were
above the upper limit.
Table 6. Precision of the XL-700
Source
ELPAT
UC
UC prep c
No. of
sample
sets
20°
3*
3
RSD, %
Average
8
8
5
Min
1
7
4
Max
20
9
6
" 4 replicates in each sample set
6 20 replicates in each sample set
c precision of UC sample preparation process
The results reported by the XL-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. The results for the 80 ELPAT samples
reported by the XL-700 were biased high (Table 7).
The average percent recovery value of 119%, the
range of values was from 95 to 155%, and the
median value of 116%. The UC sample results were
lower, with an average percent recovery of 107%,
and a range of values from 89% to 122%. While
biased high, both average recovery values were
within the range of acceptable bias (100% ±25%).
Table?. Accuracy of XL-700
Statistic
na
average
standard deviation
minimum
maximum
% Recovery
ELPAT
80
119
14
95
155
UC
60
107
7
89
122
1 Excludes estimated values < 10 |_ig/wipe
Another way to assess accuracy is to plot the results
obtained with the XL-700 versus the estimated
values that are > 10 |_lg/wipe. The linear regression
constants for the plot of the ELPAT and the UC data
17
-------
are listed in Table 8. As expected, the slopes
indicate that the results are biased high, similar to
the above conclusions regarding the percent recovery
calculations. While the performance met the criteria
stated in accuracy in Section 4 is met (unbiased if the
average percent recovery is between 75 and 125%),
the XL-700 result generally was reported higher than
the estimated value.
Comparability
Comparability refers to how well the XL-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 XL-700 results and the laboratory
results was performed for all ELPAT and UC
samples that were reported above 20 |_lg/wipe. (Note:
Data was reported to 6 |_lg/wipe for the XL-700, but
the lab only reported to 20 |_lg/wipe.) Because each
wipe was prepared individually, a true one-to-one
matching of XL-700 and laboratory results can not
be performed. However, the average concentrations
of the samples prepared at specific levels can be
compared for the XL-700 and laboratory results.
The difference between the regression slopes (m =
1.206 for ELPAT and m = 1.112 for UC) and a slope
with a perfect agreement line (m = 1.000) is
statistically significant, but the correlation
coefficients (r = 0.999 for both ELPAT and UC)
show a strong linear relationship between DataChem
and XL-700 results (Table 8). To illustrate the strong
linear agreement between the XL-700 and NLLAP
laboratory results, Figure 7 is a plot of the average
XL-700 results versus the average DataChem results
for both ELPAT and UC data. For clarity, only those
values < 500 |_lg/wipe are shown.
Detectable Blanks
Of the samples that were prepared at <2 |_lg/wipe, the
XL-700 correctly reported all 20 as less than the
reporting limits. Reporting limits ranged from 4.9 to
6.1 |_lg/wipe, so no detectable blanks were reported.
Table 8. Linear regression constants for the plots of the XL-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
1.085
(0.015)
0.150
(3.962)
0.995
ELPAT
80
1.099
(0.009)
9.698
(3.918)
0.998
versus DataChem average concentrations
UC
3
1.206
(0.021)
-3.290
(5.195)
0.999
ELPAT
18
1.112
(0.011)
13.283
(5.257)
0.999
18
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|D 500 -,
~e 45° -
•| 400 -
| 350 -
I 30° -
8 250 -
| 200-
£ 150 -
ta 100 -
A/
50 -
0 -
X
0 50 100 150 200 250 300 350 400
DataChem average concentration (ug/wipe)
450
500
Figure 7. Plot of the average XL-700 concentration versus the average DataChem
concentrations 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
XL-700 relative to the estimated concentrations for
both the ELPAT and UC samples is summarized in
Table 9. For many cases where the estimated
concentration was less than the clearance level (CL),
the XL-700 reported a result that was greater than
the CL (21 of 34 possible fp results for the UC
samples, and 6 of 12 fp results for the ELPAT
samples at the three CLs). When the estimated
concentration was equal to or greater than the
clearance level, however, the XL-700 reported few
as less than the CL and nearly all of the results as
greater than the CL (2 of 26 possible fn results for
UC samples and 2 of 28 fn results for ELPAT
samples). These findings are not surprising, since the
accuracy results reported above indicated that the
XL-700 results were positively biased, or reported
more than the estimated values.
In Figures 8, 9, and 10, the false negative
probabilities at the three clearance levels are
compared for the DataChem and XL-700 results. In
these figures, the two-sided 90% confidence
intervals (not shown in the figures for clarity) are
used to express uncertainty on the false negative
curves. These confidence intervals overlap for
XL-700 and DataChem at the 40 |_lg/wipe clearance
levels (Figure 8) over the range of true lead
concentrations. The overlapping confidence
intervals indicate the two methods are comparable
when considering their uncertainty. In Figures 9 and
10, the 90% confidence intervals for the two
methods only overlap for part of the true lead
concentration ranges (greater than 268 |_lg/wipe for
the 250 |_lg/wipe clearance level and greater than
440 |_lg/wipe for the 400 |_lg/wipe clearance level).
These results indicate that the XL-700 appears to be
less prone to false negatives even when considering
the uncertainty of the two methods at the 250
|J,g/wipe and the 400 |_lg/wipe clearance levels.
Table 10 describes the linear regression constants for
XL-700 measured concentration versus estimated
concentration for the three CLs, average percent
recovery values and standard deviations, and an
estimate of the XL-700 reported concentration at
each clearance level. The average recoveries indicate
that the XL-700 results were positively biased for all
three clearance levels for both ELPAT and UC
samples. This is also apparent in the estimated
concentration that a user might require from the XL-
700 in order to be reasonably confident that the true
result is below the clearance level. For example, for
the DataChem results, the values should be 37, 226,
and 362 |_lg/wipe in order to be confident that the
result is below 40, 250, and 400 |_lg/wipe,
respectively. Since the XL-700 is positively biased, a
result produced at 42, 276, and 431 |_lg/wipe would
indicate levels that are very likely to be below the
respective CL. These levels are about 5-10% above
the clearance levels, so to be conservative, the user
19
-------
could feel relatively confident that a number
produced by the XL-700 at the actual clearance level
of 40, 250, and 400 |_lg/wipe will have a true lead
level below the CL.
Once again, the reader is reminded that the fp/fn
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 XL-700 Measurements
Evaluation Parameter
fp: # samples where XL-700
reported the result as > CLa of
the # samples where the
estimated concentration was <
CL
fn: # samples where XL-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 |_lg/wipe
4 of 12
Oof 4
Iof8
Oof 12
250 |J,g/wipe
10 of 12
6 of 8
Iof8
2 of 8
400 |J,g/wipe
7 of 10
OofOb
Oof 10
Oof 8
Total
21 of 34
6 of 12
2 of 26
2 of 28
a CL = clearance level
b Because all eight ELPAT values were above 400 |_ig/wipe,
no samples were available to assess fp results at this level.
'0.4-
DataChem
Nton XL-700. \
35
45
50
Tme Pb Concentration (ugA/vipe)
Figure 8. Comparison of the false negative probabilities for the
NITON XL-700 and DataChem average concentrations at a
target concentration level of 40 |ig/wipe.
20
-------
True Pb Concentration (ug/wipe)
Figure 9. Comparison of the false negative probabilities for
the NITON XL-700 and DataChem average concentrations at
a target concentration level of 250 |ig/wipe.
DataChem
Nton XL-700
275300325350375400425450475500525
True Pb Concentration (ug/wipe)
Figure 10. Comparison of the false negative probabilities
for the NITON XL-700 and DataChem average
concentrations at a target concentration level of 400
|ig/wipe.
21
-------
Table 10. Summary of the Linear Regression and Recovery Data for the XL-700 Response versus the
Estimated Concentrations
Evaluation Parameter
n
slope
intercept
correlation coefficient
average % recovery
SD of % recovery
Reported concentration at
theCL
40 |_lg/wipe
UC
20
1.234
-7.897
0.771
103%
6%
42
l-ig/wipe
ELPAT
16
1.5373
-12.083
0.869
124%
16%
49
l-ig/wipe
250 |J,g/wipe
UC
20
1.041
15.827
0.587
111%
7%
276
l-ig/wipe
ELPAT
16
0.560
125.062
0.606
112%
10%
272
l-ig/wipe
400 |J,g/wipe
UC
20
1.043
13.973
0.618
108%
6%
431
l-ig/wipe
ELPAT
8
8.431
-3000.69
0.969
117%
9%
372
l-ig/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, a single analyst (a NITON expert) analyzed
all 160 samples in four 12-hour days. Eight
measurements were taken for each wipe, for a total
of 320 measurements. For the first two days of
testing, the analyst used a 60 second count time, and
analyzed 25 to 30 samples per day. For the last two
days of testing, the analyst used a 30 second count
time, and analyzed 50 to 60 samples per day. The
change in procedure did not appear to affect the
results.
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 analyst who operated the
instrument during the verification test was a NITON
expert.
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 XL-700 Series 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
Instrument lease price
Reagents/supplies
Waste Disposal
XL-700 Series XRF
NITON
40 samples/day
Cost ($)
0
50-100/h per analyst
28,995
1,980 per week
5,190 per month
0.10 per sample
Ob
Analysis method:
NLLAP Laboratory:
Actual turnaround:
Cost category
Sample shipment
Labor
Overnight shipping
Labor
Rate
Equipment
Waste Disposal
EPASW8466010b
DataChem
18 working days
Cost ($)
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 NITON 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.
XL-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 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 XL-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.
Radioactive Source and Re-Sourcing
Description (provided by NITON): For the
analysis of lead, the instrument is supplied with
a sealed Cd-109 source of between 10-40mCi
strength. The half life of Cd-109 is 1.27 years.
This means that after 15 months, the source
strength is half of what is was at the beginning.
NITON recommends a source replacement every
2 years. This recommendation is made solely for
the benefit of speeding up the analysis, as
performance otherwise is not affected. The unit
uses a standard source decay algorithm to
determine the source activity and compensates
for the reduced activity by increasing the
analysis time accordingly. Thus, when the
instrument is first supplied, instrument time =
real time. At the end of 1.27 years instrument
time = 2 * real time. This has the benefit to the
end user, that as long as they always use the
same instrument analysis time, they will obtain
the same instrument performance in terms of
accuracy and precision. For the test, the Cd-109
source used in the XL-700 instrument was 11
months old.
23
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• Instrument purchase (provided by NITON): The
spectrum analyzer can be purchased for $28,995.
The spectrum analyzer can be calibrated for thin
sample, bulk sample, or both. In the simplest
version (XL-701S), the spectrum analyzer can
quantify lead as well as Cr, Mn, Fe, Co, Ni, Cu,
Zn, As, Se, Hg, Rb, Zr, and Mo. It can also be
upgraded for analysis of soil/bulk samples with
the same element suite and/or upgraded for
additional elements (Cd, Ba, Ag, Sn, Sb, K, Ti,
Sc, V). The purchase price includes shipping
and handling, two 8-hour NiMH (Nickel Metal
Hydride) battery packs; 110/220 VAC battery
charger with 12 volt DC adapter; waterproof,
crush-resistant carrying case with locks,
Windows™ compatible reporting software; and
an RS-232 cable for downloading data. The
spectrum analyzer configured as described above
can be rented from NITON for $1,980 per week
or $5,190 per month, subject to availability,
security deposit, and completed rental
agreement. Longer-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
rent 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 several options that
influence both the frequency and cost of re-
sourcing. These options will be explained with
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 quick turnaround was not
necessary for this test. 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, with a turnaround time of 18 working days.
Cost Assessment Summary
An overall cost estimate for use of the XL-700 Series
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 XL-700
Series XRF spectrum analyzer:
The spectrum analyzer required no electrical
power, as it was battery-operated. Two
(maximum 8-hour usage) batteries were used
throughout the 12-hour workday and recharged.
24
-------
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.
On the first two days of testing, the sample
analyses were taking longer than expected (25-
30 samples per day). The radioactive source in
the XL-700 spectrum analyzer was
approximately 11 months old. The NITON
analyst believed that the instrument could
achieve adequate sensitivity with a shorter count
time, so he elected to reduce the run-times to 30
seconds. (See Appendix. Samples 1-48 were
analyzed using 60 second count time, and
samples 49-160 were analyzed using 30 second
count time.) Replicate results analyzed using the
two count times were not statistically different
(see Appendix for data).
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.
The NITON analyst ran QC samples at the start
and periodically throughout the day to confirm
that the spectrum analyzer was working
properly.
The dust in the ELPAT sample was smoothed
out to a thin layer on the wipe. (This was not
done for the UC samples because the dust was
sprinkled rather than mounded.) All wipes were
folded so that it fit the size of the XRF window
and such that it was a flat as possible for the
most accurate reading.
On the last day of testing, 15 potential users
attending a nearby conference on lead-safe
housing observed the technology in operation
and completed a survey about its user
friendliness. In general, the observers reported
that the NITON XRF spectrum analyzer seemed
to be a very practical approach to lead testing.
Many of the observers had used or currently use
the spectrum analyzer for lead-based paint
testing, so the observers surmised that learning
to operate the spectrum analyzer for dust wipes
would be easily accomplished. The majority of
the participants (n=9) stated they would consider
purchasing or using this spectrum analyzer based
on their observations and felt a new user could
be trained in 2 to 4 hours.
The spectrum analyzer contains a radioactive
source. Licensing requirements vary by state
and NITON offers contact information and
guidance with spectrum analyzer purchase or
lease.
It is recommended that NITON be contacted
with any specific questions (such as
transportation issues) that a user might have.
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 XL-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 XL-700
was forty samples per day with a single operator.
The overall performance of the XL-700 for the
analysis of lead in dust wipe samples was
characterized as biased high but within acceptable
levels, very 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
clearance samples where required) need to be
followed.
25
-------
Table 12. Performance Summary for NITON's XL-700 Series XRF Spectrum Analyzer
Feature/parameter
Precision : average RSD
Accuracy: average % recovery
Positive results on "detectable
blank" samples (< 2 jag/wipe)
False positive results
False negative results
Comparison with slope
NLLAP -recognized
laboratory results
(excluding < 25 intercept
|ag/wipe samples)
correlation
coefficient
Overall evaluation
Completeness
Size and Weight
Sample throughput (1 analyst)
Power requirements
Training requirements
Cost
Waste generated
Performance summary
UC Samples
8%
107%
n/a
DataChem XL-700
Oof 30 21 of 34
DataChem XL-700
23 of 30 2 of 26
1.206
-3.290
0.999
- Statistically significant positive
bias but within the acceptable bias
range
- Very Precise
- Strong linear relationship to the
NLLAP lab results
- Higher number of fp results
- Few fn results
ELPAT Samples
8%
119%
0 of 20 samples
DataChem XL-700
2 of 12 6 of 12
DataChem XL-700
7 of 28 2 of 28
1.112
13.283
0.999
- Statistically significant positive bias
but within the acceptable bias range
- Very Precise
- Strong linear relationship to the
NLLAP lab results
- Higher number of fp results
- Few fn results
100% of 160 dust wipe samples
8.25" x 3" x 1.875"; 2.5 Ibs
Day #1 and 2: 25-30 samples/12-hr day
Day# 3 and 4: 50-60 samples/12-hr day
12V rechargeable battery (nickel metal hydride)
One (8-hr) day instrument-specific training
Purchase: $28,995
Lease: $1,980 per week; $5,190 per month
Reagents/Supplies: $0.10 per sample
none
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 El644: 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 XL-700 Series XRF Results Compared with Laboratory Results
Sample
Analysis
Order
94
51
134
102
60
84
28
114
109
78
67
4
6
105
155
118
106
80
36
112
99
76
147
19
39
66
101
71
5
149
7
83
Source
ELPAT
ELPAT
ELPAT
ELPAT
ELPAT
ELPAT
ELPAT
ELPAT
ELPAT
ELPAT
ELPAT
ELPAT
ELPAT
ELPAT
ELPAT
ELPAT
ELPAT
ELPAT
ELPAT
ELPAT
ELPAT
ELPAT
ELPAT
ELPAT
ELPAT
ELPAT
ELPAT
ELPAT
ELPAT
ELPAT
ELPAT
ELPAT
Rep
1
2
3
4
1
2
o
5
4
1
2
3
4
1
2
o
3
4
1
2
3
4
1
2
3
4
1
2
o
5
4
1
2
o
5
4
NITON XL-700 Series
Result
|ig/wipe
<5.7
<5.5
<5.8
<5.5
<5.7
<6.1
<5.0
<5.8
<6.0
<6.0
<5.7
<5.5
<4.9
<6.0
<5.8
<5.7
<6.0
<6.1
<6.0
<6.1
25.7
22.9
23.9
16.7
20.4
22.3
27.1
25.1
34.5
33.2
32.6
34.3
Estimated
|ig/wipe
.3
.3
.3
.3
.3
.3
.3
.3
.3
.3
.3
.3
.3
.3
.3
.3
.3
.3
.3
.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
|ig/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
|ig/wipe
.3
.3
.3
.3
.3
.3
.3
.3
.3
.3
.3
.3
.3
.3
.3
.3
.3
.3
.3
.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
25
55
98
96
62
141
52
107
88
47
10
104
143
136
38
128
122
8
93
20
138
33
87
23
131
150
160
130
73
117
75
120
154
15
14
37
Source
UCLAB
UCLAB
UCLAB
UCLAB
UCLAB
UCLAB
UCLAB
UCLAB
UCLAB
UCLAB
UCLAB
UCLAB
UCLAB
UCLAB
UCLAB
UCLAB
UCLAB
UCLAB
UCLAB
UCLAB
ELPAT
ELPAT
ELPAT
ELPAT
ELPAT
ELPAT
ELPAT
ELPAT
ELPAT
ELPAT
ELPAT
ELPAT
ELPAT
ELPAT
ELPAT
ELPAT
Rep
1
2
3
4
1
2
3
4
1
2
3
4
1
2
3
4
1
2
3
4
1
2
3
4
1
2
3
4
1
2
3
4
1
2
3
4
NITON XL-700 Series
Result
|ig/wipe
46.6
42.3
42.3
37.5
43.4
36.0
39.1
41.3
45.2
41.1
37.9
35.1
39.5
41.2
49.4
38.3
42.5
35.4
41.4
36.2
44.2
50.1
55.7
56.3
60.2
75.3
57.7
67.3
75.9
56.6
65.7
47.5
68.7
66.8
81.1
69.5
Estimated
|ig/wipe
42.1
39.5
41.1
39.0
40.3
37.5
37.8
40.0
37.2
39.2
38.0
35.2
40.8
41.0
45.9
36.1
40.9
37.3
38.6
38.3
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
|ig/wipe
33
32
31
29
32
38
37
36
37
37
33
41
32
38
30
35
36
31
34
34
37
42
44
41
43
52
49
48
70
54
48
44
64
55
56
52
Estimated
|ig/wipe
35.4
35.7
38.5
36.4
35.1
40.7
39.4
41.0
41.0
38.8
39.3
44.7
36.0
44.7
39.9
37.5
37.4
36.7
35.8
39.7
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
54
11
125
48
35
44
100
82
115
77
92
127
59
145
40
53
156
151
72
79
26
30
17
o
6
57
31
126
81
32
140
41
146
86
65
29
121
144
152
58
111
Source
ELPAT
ELPAT
ELPAT
ELPAT
ELPAT
ELPAT
ELPAT
ELPAT
ELPAT
ELPAT
ELPAT
ELPAT
ELPAT
ELPAT
ELPAT
ELPAT
ELPAT
ELPAT
ELPAT
ELPAT
UCLAB
UCLAB
UCLAB
UCLAB
UCLAB
UCLAB
UCLAB
UCLAB
UCLAB
UCLAB
UCLAB
UCLAB
UCLAB
UCLAB
UCLAB
UCLAB
UCLAB
UCLAB
UCLAB
UCLAB
Rep
1
2
o
5
4
1
2
o
5
4
1
2
o
5
4
1
2
o
J
4
1
2
3
4
1
2
3
4
1
2
o
6
4
1
2
3
4
1
2
o
3
4
1
2
3
4
NITON XL-700 Series
Result
|ig/wipe
102
89.7
93
111
141
148
165
149
178
193
191
197
261
227
251
227
273
254
270
294
289
278
272
255
263
261
287
275
275
255
315
281
304
247
243
223
261
303
265
265
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
263.3
236.8
252.3
230.1
244.5
226.8
241.2
241.7
230.1
244.0
267.7
254.5
269.4
240.6
231.8
250.0
236.2
252.8
251.2
234.6
DataChem
Result
|ig/wipe
82
83
79
100
120
120
120
110
150
160
150
160
200
190
200
220
230
250
250
230
210
250
230
230
200
240
210
210
220
220
230
170
190
210
210
250
220
210
210
220
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
244.0
274.4
252.8
258.9
241.7
274.9
244.5
236.2
244.0
242.3
260.0
228.5
242.3
267.2
236.2
275.5
262.2
226.3
227.4
243.4
30
-------
Sample
Analysis
Order
22
9
43
16
46
2
116
90
27
142
63
133
69
50
113
85
68
21
119
110
123
64
108
132
139
124
74
137
61
49
159
103
70
148
13
42
Source
ELPAT
ELPAT
ELPAT
ELPAT
ELPAT
ELPAT
ELPAT
ELPAT
UCLAB
UCLAB
UCLAB
UCLAB
UCLAB
UCLAB
UCLAB
UCLAB
UCLAB
UCLAB
UCLAB
UCLAB
UCLAB
UCLAB
UCLAB
UCLAB
UCLAB
UCLAB
UCLAB
UCLAB
ELPAT
ELPAT
ELPAT
ELPAT
ELPAT
ELPAT
ELPAT
ELPAT
Rep
1
2
o
5
4
1
2
o
5
4
1
2
o
5
4
1
2
3
4
1
2
o
3
4
1
2
3
4
1
2
o
3
4
1
2
o
J
4
1
2
3
4
NITON XL-700 Series
Result
|ig/wipe
298
245
262
294
277
248
280
299
467
389
472
431
447
412
425
451
390
474
407
424
414
473
409
423
439
385
431
417
450
449
446
435
541
513
510
533
Estimated
|ig/wipe
256.7
256.7
256.7
256.7
260.8
260.8
260.8
260.8
402.7
382.8
398.9
395.5
427.6
382.3
402.2
392.2
380.6
433.7
402.2
405.5
407.2
408.8
385.6
386.7
409.4
369.5
375.1
411.6
408.7
408.7
408.7
408.7
418.1
418.1
418.1
418.1
DataChem
Result
|ig/wipe
290
240
230
250
220
250
210
210
320
360
350
340
350
340
370
340
370
340
370
390
330
320
330
360
340
360
390
330
360
430
410
410
440
410
430
420
Estimated
|ig/wipe
256.7
256.7
256.7
256.7
260.8
260.8
260.8
260.8
377.8
395.0
399.4
385.0
395.5
382.8
413.8
374.0
426.5
378.9
401.1
423.2
372.9
362.9
384.5
411.0
397.2
393.3
437.6
375.1
408.7
408.7
408.7
408.7
418.1
418.1
418.1
418.1
31
-------
Sample
Analysis
Order
91
135
1
56
24
157
18
158
12
129
97
45
89
95
34
153
Source
ELPAT
ELPAT
ELPAT
ELPAT
ELPAT
ELPAT
ELPAT
ELPAT
ELPAT
ELPAT
ELPAT
ELPAT
ELPAT
ELPAT
ELPAT
ELPAT
Rep
1
2
3
4
1
2
3
4
1
2
o
5
4
1
2
o
5
4
NITON XL-700 Series
Result
|ig/wipe
629
665
690
565
709
587
654
669
803
855
925
906
1645
1625
1620
1630
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
|ig/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
------- |