&EPA
         UnrtedStates
         EnviionnwntBi Protection
               Afrnoapheric Research and Exposure
               AssMSfiMnt L&boFBtofy
               RMMR*) Tnangk. Park, NC 27711
January 1994
         Research and Dovdopment
                                EPA 600/R-94/016
A Preliminary Evaluation of the
Scitec MAP-3, Warrington
Microlead I, and Princeton
Gamma-Tech XK-3 Portable X-Ray
Fluorescence Spectrometers

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                                                   January 1994
                                      U.S. EPA
                                      OPPTS Chemical Library
                                      EPA West Room 3379 MC7407T
                                      1200 Pennsylvania Ave. NW
                                      Washington DC 20460-000!
       A Preliminary Evaluation of the
   Scitec MAP-3, Warrington Microlead I,
      and Princeton  Gamma-Tech XK-3
Portable X-Ray Fluorescence Spectrometers
                       Prepared by

                        E. D. Estes
                      D. L. Hardison
                      C. O. Whitaker
                       J. D. Neefus
                      W. F. Gutknecht

   Center for Environmental Measurements and Quality Assurance
                  Research Triangle Institute
        Research Triangle Park, North Carolina 27709-2194

                 EPA Contract No. 68-D1-0009
                 RTI Project No. 91U-6960-187
                       Prepared for

         Ms. Sharon Harper, Work Assignment Manager

    Atmospheric Research and Exposure Assessment Laboratory
              Office of Research and Development
             U.S. Environmental Protection Agency
          Research Triangle Park, North Carolina 27711

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                               DISCLAIMER

      The information in this document has been funded wholly or in part by the
United States Environmental Protection Agency (USEPA) under EPA Contract No. 68-
Dl-0009 to the Research Triangle Institute. It has been subjected to the Agency's peer
and administrative review, and  it has been approved for  publication as an  EPA
document.  Mention of trade names  or commercial products does not constitute
endorsement or recommendation for use.

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                          ACKNOWLEDGEMENTS

      This  document was prepared under the direction of Ms. Sharon L. Harper,
Atmospheric  Research   and  Exposure  Assessment  Laboratory  (AREAL),  U.S.
Environmental Protection Agency (USEPA), Research Triangle Park, NC.
      Special acknowledgement is given to Mr. Jack Suggs, AREAL/USEPA, Research
Triangle Park, NC, Mr. John Scalera, Office of Pollution Prevention and Toxics, U.S.
Environmental Protection Agency, Washington, DC and Dr. Mary McKnight, National
Institute of Standards and Technology, Gaithersburg, MD, for their  careful review.
                                     n

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                            EXECUTIVE SUMMARY

       The potential impact on health from environmental lead has resulted in increased
 interest in lead exposure by Federal, State and local government agencies. As a result,
 programs committed to sampling and analysis of lead are increasing nationwide.  Public
 housing authorities are required, by 1994, to randomly inspect all their housing projects
 for lead-based paint.  Currently, the most common approach to screening housing for
 the presence of lead in paint is the use of the portable X-ray fluorescence (XRF) detector,
 which is relatively inexpensive (0.1 - 0.2 hours/test for labor), gives rapid results, and
 can be used with minimal damage.  Inconclusive XRF measurements must be confirmed
 with field-collected samples back in the laboratory using a more accurate analytical
 method  such as atomic absorption spectrometry (AAS) or inductively coupled plasma
 emission spectrometry (ICP).
       The accuracies and precisions of portable XRF instruments for measurements of
 lead-in-paint  concentrations  near  the  U.S. Department  of Housing  and  Urban
 Development  (HUD) action  level  for abatement  (1.0 mg/cm2) have not been well
 established.  Therefore, at  the request of  the U.S. Environmental Protection Agency
 (USEPA), the Research Triangle Institute (RTI) performed a limited evaluation of three
 portable XRFs currently being used for field measurements:  the Scitec MAP-3,  the
 Warrington Microlead I, and  the Princeton Gamma-Tech (PGT) XK-3. The purpose of
 the evaluation was to compare these very different,  commercially available portable
 XRFs, on as equal a basis as possible, for their biases and precisions when measuring
 lead in paint films at concentrations ranging  from  0 to 7.16 mg/cm2.
      Each instrument was  used to make a series of measurements  in order to
 determine the effects of sample concentration and  substrate on the precision and bias.
The samples chosen for the study were standard latex and oil-based  paint films prepared
by RTI.  The lead concentrations of the seven paint films ranged from nominally 0 to
7.16 mg/cm2 as confirmed  by digestion using a modification of NIOSH Method 7082
and analysis by inductively coupled plasma emission spectrometry.  Eight different
substrates of varying densities were chosen to represent the types of building materials
likely to be encountered in  the field.  The measurement  plan  called for  triplicate
                                       111

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measurements of each paint film on each substrate using each of the three portable XRF
instruments according to the manufacturer's instructions. The order of measurement for
the Warrington and PGT instruments followed a randomized test matrix.  Because of the
availability of the instrument, the measurements for the Scitec XRF were completed
before the test matrix was developed and therefore were not performed in the same
order.
      Based upon the data collected  during this limited evaluation, it appears that all
three instruments measure lead in paint more accurately (as determined by inspection
of bias) on 1/2" plasterboard than on the other substrates tested. Predicted biases for
the Scitec XRF across the test sample concentration range varied from -0.6 mg/cm2 at
1.6 mg/cm2 for 5"  concrete to 3.3  mg/cm2 at 0.3 mg/cm2  for solid tinderblock
Predicted biases for the  Warrington XRF ranged from -0.03 mg/cm2 at 1.6 mg/cm2 for
plasterboard to 1.1 mg/cm2 at 0.3 mg/cm2 for concrete. Predicted biases for the PGT
XRF  ranged from 0.1 mg/cm2 at 0.3 mg/cm2 for 4" cinderblock to -0.9 mg/cm2 at 1.6
mg/cm2 for 1/8" aluminum.
                                     IV

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                              TABLE OF CONTENTS

Section                                                                        Page

Disclaimer 	i
Acknowledgements  	 ii
Executive Summary	iii
Table of Contents  	 v
List of Tables  	  vii
List of Figures	ix

1.0   Introduction  	 1
      1.1    Background  	 1
      1.2    Objectives/Purpose of the Study 	 2
      1.3    Study Design 	 2

2.0   Overview of the Portable XRF  	 5
      2.1    Instrument Basics  	 5
      2.2    Available Instruments  	 7

3.0   Laboratory Tests of the Portable XRF Units	 9
      3.1    Introduction  	 9
      3.2    Scitec Map-3 	 9
             3.2.1  Description	 9
             3.2.2  Experimental Procedure	   11
      3.3    Warrington Microlead I	   11
             3.3.1  Description	   11
             3.3.2  Experimental Procedure	   11
      3.4    Princeton Gamma-Tech XK-3	   12
             3.4.1  Description	   12
             3.4.2  Experimental Procedure	   13

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                        TABLE OF CONTENTS (continued)

Section                                                                        Page

4.0   Results and Discussion	  14
      4.1    Experimental Precision and Bias	  14
      4.2    Linear Regression Analyses  	  14
             4.2.1  Hypothesis Testing	  18
             4.2.2  Confidence Intervals	  27
      4.3    Predicted Bias at Selected Lead Concentrations	  27
      4.4    Scitec Map-3	  31
      4.5    Warrington Microlead 	  31
      4.6    Princeton Gamma-Tech XK-3	  32

5.0   Conclusions and Recommendations	  33
      5.1    Conclusions  	  33
      5.2    Recommendations	  33

6.0   References	  35
Appendix A:  XRF Data
                                        VI

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                                  LIST OF TABLES

Table                                                                             Page

  1     Randomized test matrix - order (1-56) for testing each combination of
       sample and substrate 	  3

  2     Test procedures	  4

  3     Portable XRF characteristics	  10

  4     Relative standard deviations and percent differences for triplicate measurements
       of lead in paint films using portable XRF: Scitec  	  15

  5     Relative standard deviations and percent differences for triplicate measurements
       of lead in paint films using portable XRF: Wanington	  16

  6     Relative standard deviations and percent differences for triplicate measurements
       of lead in paint films using portable XRF: PGT  	  17

  7     1/2" Plasterboard	  19

  8     3/4" Plywood  	  20

  9     1/8" Aluminum	  21

 10     1/8" Steel	  22

 11    4" Cinderblock  	23

 12    Solid cinderblock	  24
                                          vn

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                          LIST OF TABLES (continued)





Table                                                                       Page





 13   Brick	  25





 14   5" Concrete	  26





 15   HUD Guidelines for Pb testing using portable XRF instrumentation  	  29
                                      Vlll

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                                LIST OF FIGURES




Figure                                                                        Page




  1    Comparison of experimentally generated slopes for portable XRF/substrate
                                                                  *y
      combinations across the lead concentration range of 0 to 7.16 mg/cm  	  28




  2    Comparison of predicted biases at 1 mg Pb/cm2 for portable XRF/substrate

      combinations	  30
                                         IX

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                                  SECTION 1
                                INTRODUCTION

 1.1    BACKGROUND
       The  adverse  health  effects  resulting  from exposure  of  young  children  to
 environmental lead have caused increased public concern in recent years. Studies have
 shown that chronic exposure even to low levels of lead can result in impairment of the
 central nervous system, mental retardation, and behavioral disorders.1'2 Although young
 children are at the greatest risk, adults may suffer harmful effects as well.3
       Numerous programs involving research on the toxicity and bioavailability of lead,
 the environmental monitoring of lead, lead abatement, and clearance testing of housing
 are currently active. Examples of past projects include the U.S. Department of Housing
 and Urban Development  (HUD)  National Survey,4  the Urban Soil Lead Abatement
 Demonstration  Project5  and  method  evaluation  studies  sponsored by the U.S.
 Environmental Protection Agency (EPA), and  abatement  programs  carried  out by
 Maryland, Massachusetts, and many other groups.
       The major sources of exposure to lead in housing units are paint, dust, and soil.
 Currently, lead-based paint is receiving emphasis by HUD6 as the  principal source for
 lead  contamination  and  exposure.   House dust  contaminated  with  lead  from
 deteriorating interior paint and from tracked-in exterior paint has been implicated as the
 most common route of exposure for young children.7  It is particularly hazardous when
 painted walls, woodwork, and furniture are accessible to young children to touch and
 to chew.
       Public housing authorities  are required, by 1994, to  randomly inspect all their
 housing  projects for lead-based paint.8  Currently, the most common approach  to
 screening housing for  the presence of lead in paint is the use of the portable X-ray
 fluorescence (XRF) detector, which  is relatively inexpensive (0.1  - 0.2 hours/test for
 labor), gives rapid results, and can be used with minimal damage.9'10 Inconclusive XRF
measurements must be confirmed with field-collected samples back in the laboratory
using a more accurate analytical method such as atomic absorption spectrometry (AAS)
or inductively coupled plasma emission spectrometry (ICP).6

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1.2   OBJECTIVES/PURPOSE OF THE STUDY
      The biases and precisions of portable XRF instruments for measurements of lead-
in-paint concentrations near the HUD action level for abatement (1.0 mg/cm2)6 have not
been well established. Therefore, at the request of the EPA,  the Research Triangle
Institute (RTI) has evaluated three of the portable XRFs currently being used for field
measurements:  the Scitec MAP-3, the Warrington  Microlead I, and the Princeton
Gamma-Tech (PGT), XK-3.  The purpose of the evaluation was  to compare these very
different, commercially available portable XRFs, on as equal a basis as possible, for their
biases and precisions  when measuring lead in paint on particular substrates.  Biases
were calculated by comparing lead concentrations of the standards as measured by each
XRF to the lead concentrations measured by digestion/ICP analysis.11
       Another goal of the project was to  determine a mechanism  or protocol  for
comparison and evaluation of current and future portable XRFs on as equal a basis as
possible.

1.3   STUDY DESIGN
      RTI's evaluation of portable XRF technology  was performed  using a phased
approach.  When the experiments were  begun in 1990, the Scitec MAP-3 was  the
portable XRF that was most widely used for field measurements of  lead in paint at
"scattered-site" housing.  However, at that time, no paint film reference materials were
available for testing the responses  of the  XRF  to  various concentrations of lead.
Therefore, RTI developed a procedure for preparing standard latex and oil-based paint
films containing known amounts of lead.12 The lead concentrations of the paint films
that were prepared ranged from nominally 0 to 7.16 mg/cm2 as confirmed by digestion
using a modification  of  NIOSH Method 708211  and analysis  by ICP.   This range
represents that typically encountered in actual field measurements.4 Different substrates
of varying densities  were chosen to represent the types of building materials likely to
be encountered in housing units. A Scitec MAP-3 portable XRF rented  from Scitec
Corporation was used   to  make triplicate measurements for  the various paint
film/substrate combinations.

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      In 1992, two additional instruments, the Warrington Microlead I and the Princeton
Gamma-Tech XK-3, were available to RTI for testing. Using the information gained in
the Stitec evaluation, a measurement plan was developed for these two.XRFs to collect
data that would allow comparison of the three instruments.  Mr. William Boyce of Scitec
Corporation had observed a hysteresis effect when the XRF was used to measure lead
in paint on a low density substrate after it was  used to measure lead in paint on a high
density substrate.  Hysteresis effects  also may be observed when painted  surfaces
containing low levels of lead are measured immediately following the measurement of
surfaces containing high levels of lead.13 Therefore, the measurement sequence was not
ordered by lead concentration or substrate density. Instead, a randomized test matrix,
presented in Table 1, was developed to determine the order of the measurements so that
the hysteresis effects, if present, would be  randomized.  No tests were performed to
determine the presence or the magnitude of the hysteresis effects.  The measurement
plan called for triplicate measurements of each combination of paint film and substrate
for the Warrington and PGT instruments. In order to perform a measurement, the test
            Table 1. Randomized Test Matrix - Order (1-56) for Testing
                     Each Combination of Sample and Substrate
Paint Sample ID (cone., me/cm2)
Substrate

1/2" Plasterboard
3/4" Plywood
Cinderblock, Std
1/8" Steel
1/8" Aluminum
5" Concrete
Brick
Cinderblock, Solid
20D1
(7.16)
18
24
17
41
18
27
34
3
20D2
(6.20)
48
5
54
20
43
14
13
4
20B2
(1.27)
37
35
40
26
2
29
28
50
20A2
(0.52)
44
32
10
9
22
23
8
6
17B
(0.00)
7
30
16
47
55
53
33
56
120-2-B
(0.07)
12
52
39
36
45
21
42
46
120-5-B
(4.%)
51
15
1
38
11
25
49
31

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paint film was placed against the substrate, and an attempt was made to position the
XRF probe on  the  center of the film so that the measurement would be made on
nominally  the  same area  each time.   The triplicate  measurements  were made
consecutively with no repositioning of the instrument between readings.
      A "measurement" for each particular instrument was performed as defined in
Table 2.  Scitec recommends a 60-second reading for a "test" and a 240-second reading
for "confirmation".14 For this study, an intermediate measurement time of 120 seconds
was chosen because a previous study indicated that there were no significant differences
in the biases and precisions for 60- and 120-second reading  times.15  The 4-minute
reading would only be performed in the field to confirm levels  within the action range.
The manufacturer's  instructions for Warrington XRF defines a measurement  as  the
average value for the lead concentration that is displayed when the trigger is depressed
for three read cycles (approximately 15 to 20  seconds for  a  new source).   The
manufacturer recommends that at least three measurements per test location should be
made before any conclusions are drawn concerning the presence  or absence of a lead
hazard.16 The PGT manufacturer recommends that a measurement be made by taking
three readings  (15 to 20 seconds each for a new source), recording  the values,  and
manually averaging them.17
            Table 2. Test Procedures
           Instrument
           Scitec
           Warrington
           PGT
            new
Measurement Procedure
Take one 120 sec reading
Take one 3-cycle reading
(15-20 sec)*, temporarily
halting after each cycle to
record the value displayed;
manually average
Take 3 readings (15-20 sec each)*,
record values and manually average
# of Measurements
      3
                    excitation source

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                                   SECTION 2
                       OVERVIEW OF THE PORTABLE XRF

 2.1    INSTRUMENT BASICS
       The portable XRF consists of an excitation source, a detector, and some means of
 specifically determining the lead X-rays emitting from the sample.18 Characteristics of
 the three portable XRFs used in the study described in this report are summarized in
 Table 3, Section 3.  The excitation source for portable units consists of a radioactive
 source.  Examples of source materials include 241Am, 109Cd,  244Cm, 57Co, and 55Fe.
 These emit X-rays or gamma rays of sufficient energy to cause excitation of the target
 atoms. Different isotopes are preferred for different ranges of elements because of the
 need to match the energy of the excitation source emission with the energy needed to
 cause excitation and X-ray emission (fluorescence) from the element of interest. 55Fe, for
 example, is well suited for the light elements Al - V (K-shell X-rays) and Nb - Sb (L-shell
 X-rays). 109Cd is well  suited for excitation of lead L-shell X-rays, while 57Co is well
 suited for both lead K-  and L-shell X-rays. (The K and L designations describe X-rays
 produced from electron transitions between the K and L shells, respectively, and the
 higher level shells; the L X-ray is of lower energy while the K X-ray is of higher energy
 and therefore can penetrate deeper.)19
       Several  types of  detectors are available.19  The solid-state detector used in the
 Scitec XRF consists of the semiconductor material SiLi.  When an X-ray passes through
 the material, the X-ray  creates free electrons  and "holes." When  a voltage is applied
 across this detector,  and an X-ray passes  through the detector, a pulse of current flows
 across  the  detector.   The number of  free  electrons  and  "holes"  produced, and
 subsequently the magnitude of this current pulse, is a function of the energy of the X-
ray, which, in  turn, is specific to  the emitting element.  Specific detection of lead is
accomplished by measurement of the magnitude of the current pulse and relating this
pulse magnitude to a standard.  This is done with a pulse height  analyzer, that is,
complex electronic circuity which differentiates current pulses by their magnitude, deals

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with overlapping pulses, and keeps track of the number of pulses of each magnitude.
The number of pulses at a particular magnitude is directly related to the concentration
of the fluorescing element.
      The Warrington XRF uses a scintillation counter composed of a cesium thallium
iodide doped crystal to convert the X-ray photon into a light photon. When radiation
interacts with the crystal, the transmitted energy excites the iodine atom and raises it to
a higher energy state.  When the iodine atom returns to its ground electronic state, the
energy is re-emitted as a light pulse in the ultraviolet region which is then absorbed by
the thallium atom and re-emitted as fluorescent light.  The light is detected by a 1/2"
photomultiplier tube.
      The detector for the PGT XRF is a proportional counter.  This is a xenon-filled
tube across which a high voltage potential is applied. When an X-ray enters the tube,
the xenon gas is ionized, producing ion pairs. The charged particles migrate toward the
appropriate electrodes under the voltage gradient.  Each electron acquires  sufficient
energy to  produce another ion pair upon collision with another xenon atom.  This
process is repeated many times so that each original X-ray entering the counter results
in a large  number of  electrons traveling toward the anode.  An electronic pulse is
produced  that  is proportional  to the number of electrons reaching the anode and,
accordingly, the energy of the X-ray.
      The  simpler XRF units are preset to count only pulses equivalent to lead X-ray
energies; these are called "direct reading" instruments. The more complex instruments,
called "spectrum analyzers," take and store the entire range of X-ray emissions in a small
on-board computer that performs  the task of relating current  pulse amplitude and
numbers of pulses to information  stored from standards.   This computer  will
automatically identify the elements and determine their concentrations.
      A major limitation of XRF is that the efficiency of production of the fluorescing
X-rays is very dependent upon  the paint matrix and the substrate. The numbers of X-
rays produced  will depend  upon (1) the ability  of the exciting or source  X-rays to
penetrate the matrix and reach the atoms of interest; (2) secondary X-rays (created from
the interaction  of the primary  excitation X-rays with other elements in the sample)
reaching and causing fluorescence of the element of interest; (3) primary excitation X-

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rays being scattered by matrix and substrate components so as to hit the atoms of
element of interest from all angles; and (4) the ability of the X-rays emitted from the
atoms of interest to escape from the matrix and reach the detector without being
electromagnetically reabsorbed or scattered by the matrix. In the laboratory, great care
is taken to match the matrix of the standards and unknowns. This is very difficult in
the field, and impossible with instruments used  to perform direct readings off walls,
floors, etc.
       Two principal approaches  are being taken to deal with this  substrate problem
when analyzing lead-containing  paint.   In  the  first, which provides for a partial
correction, a  reading of the surface is taken.  Then the paint is scraped off the surface
and a second reading is taken to obtain a background reading, which is subtracted from
the first.  This substrate correction approach was applied  for the Warrington Microlead
I and Princeton Gamma-Tech XK-3 instruments.  In the second approach, information
is taken from the total X-ray emission  spectrum, and, using proprietary software, a
substrate correction is calculated.  The  software  includes mathematical variables
determined from measurement of standard paint films placed on different substrates,
e.g., wood, plasterboard, metal, etc.  The  Scitec  MAP-3  instrument evaluated in this
study uses this second approach.

2.2   AVAILABLE INSTRUMENTS
      At the time of  these  evaluations in  1992, three manufacturers were widely
recognized as having commercially available XRFs designed for in-situ paint testing.
The instruments that were tested  by RTI and addresses of these manufacturers are as
follows:
             Princeton Gamma-Tech XK-3          Princeton Gamma-Tech Inc.
                                                 1200 State Road
                                                 Princeton, NJ  08540
                                                 (609) 724-7310
             Warrington Microlead I               Warrington Corporation
                                                 2205 West Braker Lane
                                                 Austin, TX 78758
                                                 (800) 233-9491

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Scitec MAP-3                        Scitec Corporation
                                    1029 Kellogg Street
                                    Kennewick,WA  99336
                                    (509) 783-9850
                          8

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                                  SECTION 3
                         LABORATORY TESTS OF THE
                            PORTABLE XRF UNITS

 3.1    INTRODUCTION
       The Scitec, Warrington, and PGT portable X-ray fluorescence units (XRF) were
 employed to measure lead in paint using standard paint films and selected substrate
 materials.  These instruments were pre-calibrated by the manufacturer and were not
 recalibrated by RTL  The paint films, containing known concentrations of lead, were
 prepared by RTI  from new latex and oil-based paints  and pure lead salts.  The
 concentration of lead in each paint film was  confirmed by digestions  using  a
 modification of NIOSH Method 708211 and ICP spectrometry. The characteristics of the
 three XRFs are discussed in the following sections and summarized  in Table 3.

 3.2    SCITEC MAP-3
       3.2.1   Description
       The Scitec X-ray fluorescence unit consists of the Ambient Scanner and the MAP-3
 Console with battery power and cable.  The MAP-3 Console is basically a portable
 computer that contains the calibration data and has memory for more than 1000 entries,
 including measurement values, identification numbers, analysis times and methods
 chosen.  The data can be retrieved by connecting the console to an IBM PC-XT. The
 Ambient Scanner houses the radioactive 57Co source. The system should be returned
 to Scitec once a year for source replacement and recalibration.
      After connection of the Ambient Scanner to the console, the appropriate values
for calibration program, identification number, and analysis time may be chosen. The
surface to be analyzed is positioned against the rubber boot and shutter of the scanner.
The shutter then is opened to expose the sample to the source,  and the analysis  is
controlled from the console.

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Table 3. Portable XRF Characteristics

Type
Source
(Halflife: Days)
Decay Compensation
Detector
Shell detected
(KeV)
Substrate Correction
Potential Interferences
Range of Calibration
Substrates Used for Calibration
Calibration Materials
Strength of Source Used for
Study (Original Strength)
Recommended Source
Replacement
Scitec Warrington
MAP-3 1 Microlead 1
Spectrum Analyzer
57Co
(276)
—
SiLi
K (74.96)
L (10.55)
Proprietary Algorithm
K=Au, Bi, Hg, Tl
L=As, Cd, Cu, Mo, Zn
0 - 6.19 mg/cm2
>30
Old HUD/NIST & RTI
prepared
37.8 mCi
(40 mCi)
Once /year
Direct Reader
57Co
(276)
Source date in software
Scintillation Counter
K
(74.96)
Scrape
K, same
0.6 - 2.00 mg/cm2
up to 15
Old HUD/NIST
3.4 mCi
(10.4 mCi)
Once/ 14 months
PGT
XK-3
Direct Reader
57Co
(276)
Ta foil internal ref
Xe gas, prop, counter
K
(74.96)
Scrape
K, same
0.6 - 2.99 mg/cm2
none
Old HUD/NIST
9.1 mCi
(10.4 mCi)
Once/year

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       3.2.2  Experimental Procedure
       The Scitec MAP-3  unit used by RTI in this evaluation contained a new 57Co
 source and had been calibrated by the manufacturer over the range of 0 to 6.19 mg/cm2
 of lead using films prepared by RTI and the old HUD/NIST films. The XRF was used
 in the "universal" substrate correction mode to make three 120-second measurements
 each of selected  paint films placed one at a time on selected substrates.  The Scitec
 measurements were made prior to the development of the randomized test matrix (Table
 1) and,  therefore, were not made  in the order specified in the matrix.  In addition,
 several paint film/substrate combinations specified in the matrix (Table 1) had not been
 made when the Scitec system was being evaluated.  Measurement data are reported in
 Appendix A.

 3.3    WARRINGTON MICROLEAD I
       3.3.1  Description
       The Warrington Microlead I is a portable, microcomputer-based XRF with a 57Co
 source.  The  instrument has built-in "Zero Standard" and "Lead Standard" functions so
 the user can  establish a zero reference using a "standard" substrate and check that the
 analyzer reads the lead concentration correctly with a "standard" paint film provided by
 Warrington.   The background density  is displayed  with each reading to alert the
 inspector to changes in substrate that might affect the accuracy of the lead reading. Up
 to 1000 pieces of information (lead readings, project numbers, apartment numbers, times
 and  dates, for example) can be stored  and subsequently printed on a  portable printer.
 Warrington recommends that the source be changed every 14 months.
       The probe  is placed against the test surface and the trigger is pulled until the
 analyzer beeps and displays  the  lead  reading.   Successive readings  are averaged
 automatically.  Warrington recommends that the trigger be depressed  through three
 successive cycles to obtain a lead measurement.

      3.3.2   Experimental Procedure
      The Warrington XRF used  in  this evaluation was borrowed from Dr. Mary
McKnight of  the National Institute of Standards and Technology.  It contained a used
                                      11

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source with a strength of -3.4 mCi. Some measurements were performed in the "auto"
mode (by depressing the trigger through three read cycles to obtain an automatically-
calculated average) prior to the development of the randomized test matrix.  In a
memorandum dated 3/26/92 to the RTIXRF team, the EPA Work Assignment Manager
recommended that the randomized tests be performed in the "manual" mode (i.e., the
trigger would be released after each read cycle so that the lead concentration read
during that cycle could be recorded and an average of the three readings be calculated
manually to represent one measurement). The reason for this modified procedure was
that Warrington's definition of a single reading was interpreted to be three count cycles
while PGT's single reading is one count cycle. This "halted" reading procedure would
allow comparison of the XRFs on a more equal basis.
       When the analyst began to work through the randomized test matrix, he made
the decision to omit film/substrate combinations that had already been measured in the
automatic mode. However, since these measurements were made at a different time and
in a different mode than the randomized measurements, they were not included in this
evaluation and do not appear in the Warrington data presented in Appendix A.
       A discussion with a representative of Warrington corporation revealed that the
precision obtained using the automatic mode will be better than the precision obtained
using the manual mode.20 When the  trigger is depressed through three read cycles, a
"running average" is generated continuously. When the trigger is released after each
cycle, the data from the previous cycle is not included in the following cycle.  In
addition to the paint film/substrate measurements, measurements were made of each
substrate alone so that the randomized data could be corrected for substrate effects. The
"zero standardize" procedure described in the  user's manual was performed at the
beginning, middle, and end of each analysis day.

3.4    PRINCETON GAMMA-TECH XK-3
      3.4.1  Description
      The Princeton Gamma-Tech XK-3 utilizes a 57Co scintillation source  with a
tantalum foil internal reference device to automatically correct for source decay. The
instrument's internal programming determines exposure time by referring to the count
                                      12

-------
for the 73Ta foil. When the 73Ta counter discriminator/channel is full, the instrument
triggers a shutter release.  One charge of the battery pack will provide 8 hours of
operation. The manufacturer recommends that the source be changed once a year at the
PGT factory.
      The  user  presses the face-plate  of the instrument against  the surface  to  be
analyzed, pushing down firmly on the handle. Depression of the spring-loaded handle
opens the shutter. After 15 to 20 seconds, a reading appears on the digital display. PGT
recommends taking three successive readings and manually averaging the results to
obtain a lead measurement.

      3.4.2  Experimental Procedure
      The PGT XRF used in this evaluation was borrowed from Mr. Jim Hayes of the
North Carolina State Government Health  Services Section.  The 57Co source had been
replaced by Warrington Corporation and was new (first half-life). Mr. Hayes reported
that replacements had been made by Warrington previously and that the XRF performed
properly each time such a replacement  was made.21  Three  readings were  taken
manually and averaged to obtain one  lead measurement.  In addition to the paint
film/substrate measurements, measurements were made of each substrate alone so that
the randomized  data could be corrected for substrate effects.  Measurement data are
reported in Appendix A.
                                      13

-------
                                  SECTION 4
                          RESULTS AND DISCUSSION

 4.1    EXPERIMENTAL PRECISION AND BIAS
       Data from the triplicate measurements of each paint film/substrate combination
 using each of  the three XRFs  are presented in Appendix A.  The effects of lead
 concentration and substrate on the precision and bias of XRF measurements can be
 determined by examination of the data presented in Tables 4 through 6. The tables are
 ordered by decreasing lead concentration in the paint films and by increasing substrate
 density as determined by the Warrington XRF.  The relative standard deviation (RSD)
 of each set of triplicate measurements, an indicator of precision, is calculated as
                              RSD = (SD/x) x 100
            where X is the average value of the three measurements and
                           SD =
                                 N
      The percent difference  (% Diff) of the XRF measured  value  from the ICP
 measured value, an indicator of bias, is calculated as
                        % Diff
                                  ICP value - x
                                    ICP value
                                               /
x 100
      The  data show that, in general,  precision and  bias  improve  as  the  lead
concentration in the paint film increases.  No trend with respect to substrate was
apparent from visual inspection of the data; no statistical tests for substrate effects were
performed.

4.2    LINEAR  REGRESSION ANALYSES
      Linear regression analyses  were performed on  the experimental  XRF  data
presented in Appendix A using a standard linear calibration computer program.22
                                      14

-------
Table 4.   Relative standard deviations and percent differences for triplicate measurements of lead in paint films using
           portable XRF: Scitec
ICP
Anal.
mg/cm
7.16
6.20
4.96
1.27
0'.52
0.0
I/
Plaste
RSD
8.7
15.1
NA
10.0
35.3
—
2"
rboard
%
Diff
-3.2
11.3
NA
-21.3
-16.7
—
3/
Plyv
RSD
9.2
4.9
5.0
24.1
33.3
—
4"
rood
%
Diff
-5.0
-4.3
-38.2
-50.1
-42.3
—
I/
Alum
RSD
8.0
9.1
NA
14.3
20.0
—
8"
inum
%
Diff
6.1
20.4
NA
-16.0
-3.8
—
I/
St<
RSD
3.7
11.6
NA
20.8
17.3
173
8"
:el
%
Diff
0.6
18.3
NA
15.5
28.2
—
4
Cinde
RSD
5.6
3.7
NA
142
40.0
63.0
it
rblock
%
Diff
-5.5
8.6
NA
-79.0
-3.8
—
Sc
Cinde
RSD
1.4
4.0
NA
8.5
56.8
5.1
)lid
.rblock
%
Diff
15.0
28.5
NA
275
451
—
Br
RSD
5.6
12.9
NA
173
173
—
ick
%
Diff
-10.6
3.8
NA
-92.1
-93.6
—
e
Con
RSD
18.0
16.3
NA
96.6
—
—
>"
crete
%
Diff
-29.7
-13.4
NA
-63.3
-100
—

-------
Table 5.    Relative standard deviations and percent differences for triplicate measurements of lead in paint films using
           portable XRF: Warrington
ICP
Anal.
mg/cm
7.16
6.20
1.27
0.52
0.07
0.0
I/
Plaste
RSD
0.8
2.3
1.4
18.6
NA
1530
2"
rboard
%
Diff
-9.2
-4.1
0.0
24.4
NA
—
3/
Plyv
RSD
0.6
1.0
8.2
16.5
NA
28.9
4"
wod
%
Diff
-10.8
-4.6
11.5
23.1
NA
—
I/
Alum
RSD
1.7
1.9
9.3
42.4
NA
31.4
8"
inum
%
Diff
-3.6
2.6
11.0
75.0
NA
—
I/
St
RSD
2.5
0.3
6.0
10.1
22.3
32.9
8"
eel
%
Diff
1.7
4.0
55.1
176
1267
—
4
Cinde
RSD
1.0
1.3
22.7
—
13.7
30.3
M
rblock
%
Diff
-1.7
2.7
27.8
—
424
—
Sc
Cinde
RSD
2.5
3.8
12.1
45.5
149
13.9
did
rblock
%
Diff
-5.4
0.8
5.8
42.9
105
—
Br
RSD
2.0
2.6
6.4
8.2
31.5
28.2
ck
%
Diff
-5.5
6.1
40.9
101
467
—
<
Con
RSD
6.1
0.0
7.7
5.7
12.2
12.2
>"
crete
%
Diff
-6.1
11.9
74.8
235
1362
—

-------
Table 6.  Relative standard deviations and percent differences for triplicate measurements of lead in paint films using
          portable XRF: PGT
ICP
Anal.
mg/cm
7.16
6.20
4.96
1.27
0.52
0.07
0.0
I/
Plaste
RSD
5.8
6.3
5.5
16.5
5.9
32.9
—
2"
rboard
%
Diff
-15.1
-10.6
11.3
-3.9
-1.9
424
—
3/-
Plyw
RSD
1.0
4.9
3.4
25.8
54.1
24.7
68.7
4"
/ood
%
Diff
-20.8
-16.5
-39.2
-48.3
3.2
-300
—
I/
Alum
RSD
1.7
5.3
6.8
67.9
NA
20.1
163
8"
inum
%
Diff
-27.1
-26.2
-17.9
-65.1
NA
-976
—
I/
St<
RSD
1.3
2.0
6.7
14.6
243
8.2
2.3
8"
:el
%
Diff
-18.8
-6.8
8.3
-68.8
-103
1110
—
4
Cinde
RSD
NA
2.6
3.2
37.8
71.6
82.0
86.7
it
rblock
%
Diff
NA
-21.6
23.6
-23.4
10.3
224
—
Sc
Cinde
RSD
2.4
7.7
3.9
41.4
32.8
208
456
>lid
.rblock
%
Diff
-21.3
-26.9
9.2
-38.8
-46.8
-243
—
Br
RSD
6.6
7.9
10.9
28.2
39.3
121
24.2
ick
%
Diff
-26.2
-28.5
-26.9
-16.8
-42.3
-371
—
<
Con
RSD
0.6
3.9
10.2
29.3
6.0
4015
17.2
>"
crete
%
Diff
-34.6
-28.9
-6.3
-24.7
-44.2
114
—

-------
 Regression parameters were calculated for each substrate for each portable XRF using
 the model y = a + bx, where a is the intercept and b is the slope. The data were entered
 as x,y pairs where  x  is  the lead concentration  of the paint film  measured in the
 laboratory using acid digestion/ICP and y is the  concentration measured by XRF.  A
 least squares analysis assumes that the independent variable, x, is measured without
 error.  The laboratory analysis of the paint films showed some variability.  However,
 least squares analysis can be used if the error of x is less than one-tenth of the average
 scatter of the x's from their mean.23  Examination of the paint film laboratory analysis
 results revealed that this condition was met.  Results of the linear regression analyses
 are presented in Tables 7 through 14.

       4.2.1   Hypothesis Testing
       After the regression values were computed, tests were performed to determine
 slopes that are statistically equal to one at the 95 percent confidence level according to
 the following:
b = 1 if
b-1
(se)b
< t, /i
1 - a/2, n-.,
                     where b = slope, (se)b = standard error of the slope and
                     ti-^/2, n.2 = critical value with (n-2) degrees of freedom.
       Similarly, tests were performed to determine intercepts that are statistically equal
to zero at the 95 percent confidence level according to the following:
a = 0 if
a
fee).

< *1 - a/2,n - 2
                 where a = intercept, (se)a = standard error of the intercept and
                 *!—12, n-2 = critical value with (n-2) degrees of freedom.
      Slopes that are statistically equal to one and intercepts that are statistically equal
to zero are indicated by asterisks in Tables 7 through 14.
                                         18

-------
                                               Table 7. %" Plasterboard

No. of Data Pairs
Slope
SDslope
Intercept
SD
•-^intercept
Corr. Coef.
Residual Variance, %
Standard Error of Estimate
of X from Y
Estimated
bias* and
95%
confidence
interval
at:"
0.3 mg/cm2
0.8 mg/cm2
1.0 mg/cm2
1.3 mg/cm2
1.6 mg/cm2
Scitec
15
1.043*
0.051
-0.108**
0.216
0.9851
2.96
0.539
-0.09 ± 1.35
-0.07 ± 1.34
-0.06 ± 1.34
-0.05 ± 1.33
-0.04 ± 1.33
Warrington Warrington
(uncorrected) || (corrected)
15
0.915
0.014
0.413
0.060
0.9985
0.30
0.172
+0.39 ± 0.37
+0.34 ± 0.37
+0.33 ± 0.37
+0.30 ± 0.37
+0.28 ± 0.37
15
0.915
0.014
0.103**
0.060
0.9985
0.30
0.172
+0.08 ± 0.37
+0.04 ± 0.37
+0.03 ± 0.37
-0.01 ± 0.37
-0.03 ± 0.37
PGT
(uncorrected)
21
0.812
0.032
0.386
0.129
0.9859
2.80
0.494
+0.33 ± 0.91
+0.24 ± 0.91
+0.20 ± 0.90
+0.14 ± 0.90
+0.09 ± 0.90
PGT
(corrected)
21
0.812
0.032
0.096**
0.129
0.9859
2.80
0.494
+0.04 ± 0.91
-0.05 ± 0.91
-0.09 ± 0.90
-0.15 ± 0.90
-0.20 ± 0.90
\D
    * Slope (b) = 1 at the 95% level of confidence
    ** Intercept (a) = 0 at the 95% level of confidence
 a
(se).
t
 1 - afZ, n - 2
    f Bias is calculated as XRF predicted value minus the known concentration of the paint film.

    ft  Lead concentraUons chosen by reference to HUD Guidelines (see Table 15).

-------
                                                 Tables.  3/4" Plywood

No. of Data Pairs
Slope
SDslope
Intercept
sn
JLJ intercept
Corr. Coef.
Residual Variance, %
Standard Error of
Estimate of X from Y
Estimated
bias* and
95%
confidence
interval
at:"
0.3 mg/cm2
0.8 mg/cm2
1.0 mg/cm2
1.3 mg/cm2
n
1.6 mg/cm
Scitec
18
0.934*
0.056
-0.341**
0.248
0.9721
5.5
0.689
-0.36 + 1.53
-0.39 + 1.52
-0.41 + 1.51
-0.43 + 1.50
-0.45 + 1.50
Warrington
(uncorrected)
15
0.873
0.014
0.651
0.060
0.9983
0.34
0.182
+0.61 + 0.38
+0.55 + 0.38
+0.52 + 0.37
+0.49 + 0.37
+0.45 + 0.37
Warrington
(corrected)
15
0.873
0.014
0.301
0.060
0.9983
0.34
0.182
+0.26 + 0.38
+0.20 + 0.38
+0.17 + 0.37
+0.14 + 0.37
+0.10 + 0.37
PGT I PGT
(uncorrected) || (corrected)
21
0.799
0.031
0.231**
0.125
0.9863
2.72
0.487
+0.17 + 0.88
+0.07 + 0.88
+0.03 + 0.87
-0.03 + 0.87
-0.09 + 0.87
21
0.799
0.031
-0.199**
0.125
0.9863
2.72
0.487
-0.26 + 0.88
-0.36 + 0.88
-0.40 + 0.87
-0.46 + 0.87
-0.52 + 0.87
N>
O
    * Slope (b) = 1 at the 95% level of confidence
                                                b - 1
                                                (se)b
      Intercept (a) = 0 at the 95% level of confidence  —
                                                   (se)
                                                     ll - «/2. n - 2
                                                       t
                                                        1 - «/2. o -2|




f Bias is calculated as XRF predicted value minus the known concentration of the paint film.



ft Lead concentrations chosen by reference to HUD Guidelines (see Table 15).

-------
                                            Table 9. 1/8" Aluminum

No. of Data Pairs
Slope
SDslope
Intercept
SDintercept
Corr. Coef.
Residual Variance, %
Standard Error of Estimate
of X from Y
Estimated
biast and
95%
confidence
interval
at:ft
0.3 mg/cm2
0.8 mg/cm2
1.0 mg/cm2
1.3 mg/cm2
1.6 mg/cm2
Scitec
15
1.137
0.044
-0.117**
0.186
0.9906
1.87
0.428
-0.08 + 1.17
-0.01 + 1.16
+0.02 + 1.15
+0.06 + 1.15
+0.10 + 1.14
Warrington Warrington
(uncorrected) | (corrected)
15
0.931
0.020
0.267
0.086
0.9970
0.60
0.243
+0.25 + 0.54
+0.21 + 0.53
+0.20 + 0.53
+0.18 + 0.53
+0.16 + 0.53
15
0.931
0.020
1.387
0.086
0.9970
0.60
0.243
+0.37 + 0.54
+0.33 + 0.53
+0.32 + 0.53
+0.30 ± 0.53
+0.28 + 0.53
PGT
(uncorrected)
18
0.773
0.031
0.188**
0.136
0.9875
2.48
0.476
+0.12 + 0.86
+0.01 + 0.85
-0.04 + 0.85
-0.11 + 0.85
-0.18 + 0.84
PGT
(corrected)
18
0.773
0.031
-0.492
0.136
0.9875
2.48
0.476
-0.56 + 0.86
-0.67 + 0.85
-0.72 + 0.85
-0.79 + 0.85
-0.86 + 0.84
* Slope (b) = 1 at the 95% level of confidence
                                            b  -  1
                                             (se)h
** Intercept (a) = 0 at the 95% level of confidence
                                                  a
                                                (se).
ll - «/2, n - 2
    - a/2. n - 2
f Bias is calculated as XRF predicted value minus the known concentration of the paint film.




ft Lead concentrations chosen by reference to HUD Guidelines (see Table 15).

-------
                                                  Table 10. 1/8" Steel

No. of Data Pairs
Slope
SDslope
Intercept
"^intercept
Corr. Coef.
Residual Variance, %
Standard Error of Estimate
of X from Y
Estimated
biast and
95%
confidence
interval
at:ft
0.3 mg/cm2
0.8 mg/cm2
1.0 mg/cm2
1.3 mg/cm2
1.6 mg/cm2
Scitec
15
1.064*
0.046
0.115**
0.199
0.9879
2.41
0.486
+0.13 ± 1.24
+0.17 + 1.23
+0.18 + 1.23
+0.20 + 1.22
+0.22 + 1.22
Warrington
(uncorrected)
18
0.893
0.013
-0.575
0.051
0.9983
0.34
0.177
-0.61 + 0.36
-0.66 + 0.36
-0.68 + 0.36
-0.71 + 0.36
-0.75 + 0.36
Warrington
(corrected)
18
0.893
0.013
0.895
0.051
0.9983
0.34
0.177
+0.86 + 0.36
+0.81 + 0.36
+0.79 + 0.36
+0.76 + 0.36
+0.72 + 0.36
PGT
(uncorrected)
21
0.917*
0.043
0.484
0.175
0.9797
4.02
0.591
+0.46 + 1.24
+0.42 + 1.23
+0.40 + 1.23
+0.38 + 1.22
+0.35 + 1.22
PGT
(corrected)
21
0.917*
0.043
-0.756
0.175
0.9797
4.02
0.591
-0.78 ± 1.24
-0.82 + 1.23
-0.84 + 1.23
-0.86 + 1.22
-0.89 + 1.22
N)
N)
    * C
Slope (b) = 1 at the 95% level of confidence
    ** Intercept (a) = 0 at the 95% level of confidence
                                                         ll - a/2. n - 2
                                                    (se).
                                                      t
                                                       1 - a/2, n - 2
   f Bias is calculated as XRF predicted value minus the known concentration of the paint film.


   ft Lead concentrations chosen by reference to HUD Guidelines (see Table 15).

-------
                                               Table 11. 4" Cinderblock

No. of Data Pairs
Slope
SDslope
Intercept
"^intercept
Corr. Coef.
Residual Variance, %
Standard Error of Estimate
of X from Y
Estimated
biast and
95%
confidence
interval
at:ft
0.3 mg/cm2
0.8 mg/cm2
1.0 mg/cm
1.3 mg/cm2
1.6 mg/cm2
Scitec
15
1.017*
0.055
-0.155**
0.236
0.9814
3.69
0.601
-0.15 + 1.48
-0.14 + 1.47
-0.14 + 1.46
-0.13 + 1.46
-0.13 + 1.45
Warrington Warrington
(uncorrected) | (corrected)
15
0.929
0.019
1.796
0.082
0.9972
0.56
0.239
+1.77 + 0.53
+1.74 + 0.52
+1.72 + 0.52
+1.70 + 0.52
+1.68 + 0.52
15
0.929
0.019
0.486
0.082
0.9972
0.56
0.239
+0.46 + 0.53
+0.43 + 0.52
+0.41 + 0.52
+0.39 + 0.52
+0.37 + 0.52
PGT
(uncorrected)
18
0.717
0.028
0.405
0.091
0.9883
2.33
0.388
+0.32 + 0.64
+0.18 + 0.64
+0.12 + 0.64
+0.04 + 0.63
-0.05 + 0.63
PGT
(corrected)
18
0.717
0.028
0.155**
0.091
0.9883
2.33
0.388
+0.07 + 0.64
-0.07 + 0.64
-0.13 + 0.64
-0.21 + 0.63
-0.30 + 0.63
NJ
OJ
    * Slope (b) = 1 at the 95% level of confidence
b - 1

 (se)b
    ** Intercept (a) = 0 at the 95% level of confidence  —5-
                                                   y(se)B
ll - «/2. n - 2
           ll - a/2. n -2
    f Bias is calculated as XRF predicted value minus the known concentration of the paint film.


    ft  Lead concentrations chosen by reference to HUD Guidelines (see Table 15).

-------
                                              Table 12.  Solid Cinderblock

No. of Data Pairs
Slope
SDslope
Intercept
"^intercept
Corr. Coef.
Residual Variance, %
Standard Error of Estimate
of X from Y
Estimated
biast and
95%
confidence
interval
at:ft
0.3 mg/cm2
0.8 mg/cm2
1.0 mg/cm2
1.3 mg/cm2
*+
1.6 mg/cm
Scitec
15
0.697
0.075
3.434
0.321
0.9323
13.08
1.132
+3.34 + 2.01
+3.19 + 1.99
+3.13 + 1.99
+3.04 + 1.98
+2.95 + 1.97
Warrirtgton Warrington
(uncorrected) | (corrected)
18
0.934
0.020
1.851
0.078
0.9964
0.72
0.260
+1.83 + 0.56
+1.80 + 0.55
+1.79 + 0.55
+1.77 + 0.55
+1.75 + 0.55
18
0.934
0.020
0.251
0.078
0.9964
0.72
0.260
+0.23 + 0.56
+0.20 + 0.55
+0.19 + 0.55
+0.17 + 0.55
+0.15 + 0.55
PGT
(uncorrected)
21
0.749
0.032
0.401
0.130
0.9832
3.33
0.539
+0.33 + 0.92
+0.20 + 0.91
+0.15 + 0.91
+0.07 + 0.91
0.00 + 0.91
PGT
(corrected)
21
0.749
0.032
-0.189
0.130
0.9832
3.33
0.539
-0.26 + 0.92
-0.39 + 0.91
-0.44 + 0.91
-0.51 + 0.91
-0.59 + 0.91
NJ
     Slope (b) = 1 at the 95% level of confidence
b - 1
 (se)b
      Intercept (a) = 0 at the 95% level of confidence
                                                     a
                                                    (se).
- «/2, n - 2
           ll - «/2. n - 2
   f Bias is calculated as XRF predicted value minus the known concentration of the paint film.

   ft Lead concentrations chosen by reference to HUD Guidelines (see Table 15).

-------
                                                    Table 13.  Brick

No. of Data Pairs
Slope
SDslope
Intercept
SDintercept
Corr. Coef.
Residual Variance, %
Standard Error of Estimate
of X from Y
Estimated
biast and
95%
confidence
interval
at:"
0.3 mg/cm2
0.8 mg/cm2
1.0 mg/cm2
1.3 mg/cm2
«
1.6 mg/cm
Scitec 1 Warrington
1 (uncorrected)
15
1.019*
0.056
-0.495**
0.238
0.9812
3.72
0.604
-0.49 + 1.49
-0.48 + 1.48
-0.48 + 1.47
-0.47 + 1.47
-0.46 + 1.46
18
0.918
0.021
2.118
0.081
0.9959
0.82
0.276
+2.09 + 0.58
+2.05 + 0.58
+2.04 + 0.57
+2.01 + 0.57
+1.99 + 0.57
Warrington
(corrected)
18
0.918
0.021
0.528
0.081
0.9959
0.82
0.276
+0.50 + 0.58
+0.46 + 0.58
+0.45 + 0.57
+0.42 + 0.57
+0.40 + 0.57
PGT
(uncorrected)
21
0.721
0.036
0.373
0.146
0.9772
4.51
0.627
+0.29 + 1.03
+0.15 + 1.03
+0.09 + 1.03
+0.01 + 1.02
-0.07 + 1.02
PGT
(corrected)
21
0.721
0.036
-0.227**
0.146
0.9772
4.51
0.627
-0.31 + 1.03
-0.45 + 1.03
-0.51 + 1.03
-0.59 + 1.02
-0.67 + 1.02
N)
Ul
    * Slope (b) = 1 at the 95% level of confidence
                                                b  -  1
                                                 (se)b
    ** Intercept (a) = 0 at the 95% level of confidence
                                                      a
                                                    (se).
- a/2. n - 2
ll - a/2. n - 2
     Bias is calculated as XRF predicted value minus the known concentration of the paint film.


     t  Lead concentrations chosen by reference to HUD Guidelines (see Table 15).

-------
                                                 Table 14. 5" Concrete

No. of Data Pairs
Slope
SDslope
Intercept
^intercept
Corr. Coef.
Residual Variance, %
Standard Error of Estimate
of X from Y
Estimated
biast and
95%
confidence
interval
at:ft
0.3 mg/cm2
0.8 mg/cm2
1.0 mg/cm2
1.3 mg/cm2
1.6 mg/cm
Scitec
15
0.809
0.058
-0.279**
0.248
0.9682
6.26
0.783
-0.34 ± 1.55
-0.43 + 1.54
-0.47 + 1.54
-0.53 + 1.53
-0.58 + 1.53
Warrington
(uncorrected)
18
0.854
0.030
2.288
0.119
0.9901
1.97
0.430
+2.24 + 0.85
+2.17 + 0.84
+2.14 + 0.84
+2.10 + 0.84
+2.05 + 0.84
Warrington
(corrected)
18
0.854
0.030
1.098
0.119
0.9901
1.97
0.430
+1.05 + 0.85
+0.98 + 0.84
+0.95 + 0.84
+0.91 + 0.84
+0.86 + 0.84
PGT
(uncorrected)
21
0.669
0.030
0.370
0.120
0.9820
3.57
0.557
+0.27 + 0.85
+0.11 + 0.84
+0.04 + 0.84
-0.06 + 0.84
-0.16 ± 0.84
PGT
(corrected)
21
0.669
0.030
-0.150**
0.120
0.9820
3.57
0.557
-0.25 + 0.85
-0.41 + 0.84
-0.48 + 0.84
-0.58 + 0.84
-0.68 + 0.84
K)
    * Slope (b) = 1 at the 95% level of confidence
                                          b  -  1
                                           (se)b
ll - «/2, n - 2
Intercept (a) = 0 at the 95% level of confidence
                                                     a
                                                    (se).
                                                           t
                                                            1 - a/2, n - 2 I
   f Bias is calculated as XRF predicted value minus the known concentration of the paint film.

   tf Lead concentrations chosen by reference to HUD Guidelines (see Table 15).

-------
 4.2.2  Confidence Intervals
       The slopes of the calibration curves with their 95 percent confidence intervals are
 plotted in Figure 1 for each portable XRF and each substrate. The graph shows that the
 slopes  are  not significantly different  from  one  for the Scitec  XRF  on  plywood,
 plasterboard, 4" cinderblock, brick and steel and for the PGT XRF on steel. However,
 the standard deviations for PGT and Scitec XRFs generally are greater than the standard
 deviations for the Warrington XRF. Also, the PGT and Scitec XRFs show more scatter
 in the slopes for the various substrates than does the Warrington.
       If the confidence interval of a given slope overlaps the center estimate of another
 slope, there is probably no difference between the two slopes. However, overlapping
 of intervals where neither interval overlaps the center estimate of the other is not a
 strong indication that the slopes are equivalent24

 4.3   PREDICTED BIAS AT SELECTED LEAD CONCENTRATIONS
       The linear regression equations were used to calculate predicted values for y (the
 lead concentration measured by XRF) at various observed values of x (the "true" lead
 concentration of a paint film as measured by ICP). The values of x were chosen by
 reference to the HUD Guidelines6 as summarized in Table 15.
      The predicted values were used to  estimate the biases,  and their 95 percent
 confidence intervals,  of the lead concentrations as measured by  XRF compared to the
 laboratory analyzed concentrations.  A negative bias indicates that the concentration
 measured by XRF is predicted to be lower than the "true" lead concentration in the paint
 film; conversely, a positive bias indicates that the  concentration measured by the XRF
 is predicted to be higher than the "true" lead concentration.
      The  estimated biases and their 95 percent  confidence  intervals for each
 XRF/substrate  combination at 1 mg  Pb/cm2 are plotted in Figure 2.  This lead
 concentration level was chosen  because it  is the HUD level of hazard.   The biases
include zero for all combinations except the Warrington XRF on steel and concrete and
the Scitec XRF on solid  cinderblock.  The 95 percent confidence intervals for both the
Scitec and PGT XRFs  are generally larger than those for the Warrington XRF.
                                       27

-------
   PGT
                                    H  Plywood
                                    —i  Plasterboard
                                    Aluminum
                              4" Cinderblock
                              i  Brick
                                 i	•-
                 -•	1  Concrete
                    i	•	1   Solid Cinderblock
Steel
   Warrington
                                           Plywood
                                       i—•—i  Plasterboard
                                       i	•	1  Aluminum
                                       i	•	1 4" Cinderblock
                                      i	•	1   Brick
                                     i—•—i Steel
                                   -•	1 Concrete
                                       i	•	1  Solid Cinderblock
   Scitec
                                                      H  Plywood
                                                                 1  Plasterboard
                                                                       Aluminum
                                                               -" 4" Cinderblock
                                                                  Brick
                                                                  1  Steel
                                              Concrete
                                       Solid Cinderblock
                                         i	i
0.5       0.6       0.7      0.8       0.9        1         1.1        1.2
               Slope of Calibration Curve (with 95% Confidence Interval)
                          1.3
     Figure 1.    Comparison of experimentally generated slopes for portable
                  XRF/substrate combinations across the lead concentration range
                  of 0 to 7.16 mg/cm2.
                                        28

-------
  Table 15.  HUD Guidelines for Pb Testing Using Portable XRF Instrumentation
Type of
Dwelling
Multi-family
Multi-family
Scattered Site
Scattered Site
XRF Type
Direct Reading*
Spectrum
Analyzer
Direct Reading*
Spectrum
Analyzer
XRF Measured
Pb Level Considered
Negative (mg/cm2)
<0.5
<0.8
**
<0.3
XRF Measured
Pb Level Requiring
Abatement (mg/cm2)
>1.6
> 1.3
> 1.6
> 1.3
* Concentrations are substrate corrected.



  Pb levels of 1.5 mg/cm2 or less require confirmatory testing.
»*
                                      29

-------
          -2
                  -1
    -  1/2' Plasterboard
                   Ph
                        Wl
               Sh
                                                      P = PGT
                                                      W = Warrington
                                                      S = Scitec
    -  3/4' Plywood
                 Ph
                         W
           Sh
      1/8" Aluminum
              PI	•-
                  Sh
0)
O
8
0>
      1/8' Steel
          PI—
                              W|
    -  4' Cinderblock
                     Ph
                               -•	1
             Sh
      Solid Cinderblock
               PI
                        Wh
                                     Sh
   -  Brick
             Ph
                         W|
          Sh
   •  5* Concrete
               Ph
                           Wh
         Sh
         -2        -1
                   Bias (with 95% Confidence Intervals), mg/cm2
  Figure 2.     Comparison of predicted biases at 1 mg Pb/cm2 for portable
                XRF/substrate combinations.
                                       30

-------
       Again, if the interval of a given bias overlaps the center estimate of another bias,
 there  is probably no difference between the two  biases.   However, overlapping of
 intervals where neither interval overlaps the center estimate of the other is not a strong
 indication that the biases are equivalent.

 4.4    SCITEC MAP-3
       The Scitec instrument was evaluated using the "universal" calibration installed by
 the manufacturer to cover the range from 0 to 6.19 mg/cm2.  In an  earlier study, to
 determine whether the Scitec results  could  be improved  by applying a substrate
 correction, the Scitec  was used to measure the bare  substrate alone  for wood,
 plasterboard, 4" cinderblock, brick, aluminum siding and 1/8"  steel.15 All substrates
 gave readings very  dose to 0 mg/cm2 (0.00 to 0.03 mg/cm2). Therefore, no substrate
 correction was applied for this evaluation. The standard paint films yielded correlation
 coefficients ranging  from 0.93 for solid cinderblock to 0.995 for 1/8" steel.  The standard
 error of the estimate of x from y ranged from 0.30 mg/cm2 for 1/8" steel to 1.13 mg/cm2
 for solid cinderblock.  The bias of the predicted values ranged from -0.6 mg/cm2 at 1.6
 mg/cm2 for  5" concrete to 3.3 mg/cm2 at 0.3 mg/cm2 for solid cinderblock. The bias
 of the predicted values for solid cinderblock is nearly an order of magnitude greater
 than the bias for any other of the substrates tested. With the exception of 4" cinderblock,
 all substrates showed a change in predicted bias with a change in concentration of lead;
 the predicted bias for 4" cinderblock was nearly constant at -0.15 to -0.13 mg/cm2 over
 the range  0.3 to 1.6 mg/cm2.  The  data in Table 4 show that, in general, the Scitec
 precision improves as the lead  concentration in the  paint film increases; no  trend with
 respect to substrate was observed.

 4.5     WARRINGTON MICROLEAD I
       The Warrington  instrument  was  evaluated by first measuring  the lead
 concentration in the paint films placed on the various substrates and then measuring the
 "apparent lead concentration" of the substrates alone so that a substrate correction could
be applied. The correlation coefficients were consistent, ranging  from 0.990 for concrete
to 0.998 for plasterboard, plywood and steel.  The standard error of the estimate of x
                                       31

-------
from y was nearly constant, ranging from 0.2 mg/cm2 for plasterboard, plywood and
steel to 0.4 mg/cm2 for concrete. The data that had not been corrected for substrate
effects showed a positive predicted bias for all substrates except 1/8" steel. Application
of a substrate correction decreased the magnitude of the predicted bias for all substrates
except 1/8" aluminum and 1/8" steel.  For 1/8" steel, the substrate correction changed
the sign of the predicted bias from negative to positive (from -0.68 mg/cm to +0.79
mg/cm2 at 1.0 mg/cm2). The largest predicted biases observed were for the more dense
substrates cinderblock (4" and solid), brick and concrete.  The predicted biases ranged
from -0.03 mg/cm2 at 1.6 mg/cm2 for plasterboard to  1.1 mg/cm2 at 0.3 mg/cm2 for
concrete and were found to change with a change in concentration for all substrates.
The data in Table 5 show that, in general, the Warrington precision improves as the lead
concentration  in the  paint  film increases;  no trend with respect to substrate was
observed.

4.6   PRINCETON GAMMA-TECH XK-3
      The PGT instrument was evaluated using the same substrate correction procedure
as described in Section 4.5 for the Warrington XRF. The correlation coefficients were
consistent, ranging from 0.977 for brick to 0.988 for 1/8" aluminum and 4" cinderblock.
The standard  error of the estimate of  x from y ranged from 0.39  mg/cm2 for 4"
cinderblock to 0.63 mg/cm2 for brick.  Application of a substrate correction  generally
changed the sign of the predicted bias  from positive to negative and increased the
magnitude of the bias. The predicted bias after correction ranged from 0.1 mg/cm2 at
0.3 mg/cm2 for 4" cinderblock to -0.9 mg/cm2 at 1.6 mg/cm2 for 1/8" aluminum; The
predicted bias was found to change with a change in concentration for all substrates; the
largest changes were  observed for concrete and 4" cinderblock.  The data in Table 6
show that, in general, the PGT precision improves as the lead concentration in the paint
film increases; no trend with respect to substrate was observed.
                                      32

-------
                                  SECTION 5
                   CONCLUSIONS AND RECOMMENDATIONS

 5.1    CONCLUSIONS
       Based upon the data collected during this limited  evaluation of the Scitec,
 Warrington, and  Princeton  Gamma-Tech  portable  XRFs, using  the  experimental
 conditions and  test design  described in Section 1.3, it appears that all instruments
 measure lead in paint films more accurately (as determined by inspection of bias) on
 1/2" plasterboard than on the other substrates tested. The Warrington XRF gave a lower
 standard error of the estimate of x from y and a lower residual variance than the Scitec
 and PGT instruments for each of the eight substrates.  Also, the standard deviations of
 the slope and intercept for the Warrington XRF were lower than those for the Scitec and
 PGT XRFs for all substrates, with one exception; the Warrington and PGT XRFs had the
 same standard deviation of the  slope for 5" concrete.
       The predicted biases for the three instruments on each of the eight substrates are
 not significantly different except for two cases: (1) the bias of the Scitec XRF is predicted
 to be significantly higher than  the biases of the PGT and Warrington XRFs on solid
 cinderblock and (2) the bias of the Warrington XRF is predicted to be higher than that
 of the PGT XRF on 1/8" steel and 5" concrete.
      The data show that, in general, precision  and bias improve as the  lead
 concentration in the paint film increases.  No trend with  respect to substrate was
 apparent from visual inspection of the data.

 5.2   RECOMMENDATIONS
      The data  presented in this report should be considered preliminary.  Several
 improvements have been made  to the  portable XRFs and their calibration procedures.
 It is recommended that the evaluation be repeated with care being taken to ensure that
 the instruments  are compared on as equivalent a basis as  possible with a minimum
number of tests.  This would include the following:
      1)    Careful selection of instruments so that source age is similar for XRFs from
            each of the three manufacturers.
                                      33

-------
2)    Testing of multiple XRFs (at least 3) from each manufacturer to obtain
      more representative data.

3)    Careful definition of "measurement" so that each XRF is being  used as
      intended by the manufacturer to obtain data that are directly comparable.

4)    Following a randomized matrix, in the order specified, for each XRF.

5)    Using the new NIST-certified standard paint films (SRM-2759) and any
      other characterized research materials that have become available since this
      limited evaluation was performed.

6)    Refining the test matrix to minimize the number of substrates tested.
                               34

-------
                                  SECTION 6
                                 REFERENCES
 1.     Agency for Toxic Substances and Disease Registry.  The Nature and Extent of
       Lead Poisoning in Children in the United States:  A Report to Congress, U.S.
       Department of Health and Human Services.  1988.

 2.     Grand, L.D. and J. M. Davis. Effects of Low Level Lead Exposure on Pediatric
       Neurobehavioral  Development:  Current  Findings and Future Direction.  In:
       Smith, M.S.,  L.D.  Grant,  and A.I.  Sors, eds.  Lead Exposure  and Child
       Development:  An International Assessment.   London.   Kluwer Academic
       Publishers, pp. 49-115,1989.

 3.     Goyer, R.A.  Toxic Effects of Metals.  In: Klassen, CD., M.O. Amdur, and J.
       Doull, eds., Casarett and Doull's Toxicology, Third Edition, Macmillan, New York.
       1986.

 4.     U.S. Department of Housing and Urban Development.  Comprehensive and
       Workable Plan for the Abatement  of Lead-Based Paint in Privately  Owned
       Housing, A Report to Congress. Washington, D.C., December 1990.

 5.     Elias, Robert.  Overview  of the  Urban Soil Lead Abatement Demonstration
       Project. In Proceedings  of U.S. EPA Symposium on Urban Soil Lead Abatement,
       Research Triangle Park, NC, August, 1992. (in preparation)

 6.     Lead-Based Paint:  Interim Guidelines for Hazard Identification and Abatement
       in Public and Indian Housing, Office of Public and Indian Housing, Department
       of Housing and Urban Development, April 1,1990.

 7.     Abbritti, G., G. Muzi, C. Cicioni, M.P. Accattoli, T. Fiordi, and P. Morucci. Effects
       of Low Doses of Lead on Children's Health.  In: Caroli, S., G.V. lyenzar, and H.
      Muntau, eds., Bioelements: Health Aspects, Ann. Inst. Super. Sanita. 25(3): 437-
      488,1989.

8.    Lead-Based Paint  Poisoning Prevention Act, 42 U.S.C. 4822 (d)(2)(A), 1971.
      Amended 1991.
                                      35

-------
9.    McKnight, M.E., W.E. Byrd, and W.E. Roberts, Measurine Lead Concentration in
      Paint Using a Portable Spectrum Analyzer X-Rav Fluorescence Device. National
      Institute of Standards and Technology, NISTIR W90-650, May 1990.

10.   Estes, E.D., and W.F. Gutknecht. Workshop Report: Identification of Performance
      Parameters for Portable X-Ray Fluorescence Measurement of Lead in Paint.  EPA
      600/R-93/130, U.S.  Environmental Protection Agency, Research Triangle Park,
      North Carolina, 1993.

11.   Binstock,  D.A., D.L. Hardison, P.M. Grohse, and W.F. Gutknecht.  Standard
      Operating Procedures for Lead in Paint by Hotplate- or Microwave-based Acid
      Digestions and Atomic Absorption or Inductively Coupled Plasma Emission
      Spectrometry.   EPA 600/8-91/213, U.S. Environmental  Protection Agency,
      Research  Triangle Park, North Carolina, 1991 (19 pp). Available from NTIS,
      Springfield, VA; NTIS PB92-114172.

12.   Gutknecht, W.F., L.L. Hodson, H.H. Dutton, and D.A. Binstock. Preparation of
      Lead-in-Paint  Standard Films.   EPA  Contract  No.  68-D1-0009,  Report in
      preparation.

13.   International  Organization of  Legal  Metrology.   First  Preliminary  Draft
      Recommendation   on  Portable  and   Transportable  X-Ray  Fluorescence
      Spectrometers for Field Measurements of Hazardous Elemental Pollutants. OIML
      Reporting Secretariat PS17/RS5: U.S.A., October 1992.

14.   Scitec MAP-3  Operator's Manual.  Available from Scitec Corporation,  1029
      Kellogg Street, Kennewick, Washington  99336. Tel. No. (509) 783-9850.

15.   Hardison, D.L., Whitaker, C.O., Neefus, J.D.,  Estes, E.D., and Gutknecht, W.F.,
      "Evaluation of Portable X-Ray  Fluorescence Spectrometer  for Measurement of
      Lead in Paint, Soil and Dust, EPA 600/A-92/245, U.S. Environmental Protection
      Agency, Research Triangle Park, NC1992. Available from NTIS, Springfield, VA;
      NTIS PB93-121010.

16.   Warrington Microlead  I Operator's  Manual.    Available from Warrington
      Corporation, 2205 West Braker Lane, Austin, Texas 78758. Tel. No. (800) 233-9491.
                                      36

-------
17.   Princeton Gamma-Tech XK-3 Operator's Manual.  Available from Princeton
      Gamma-Tech Inc., 1200 State Road, Princeton, New Jersey  08540.  Tel.  No.
      (609 724-7310.

18.   Woldseth, R. X-Ray Energy Spectrometry. Kevex Corporation, Burlingame, CA
      1973.

19.   Willard, H.  H., L. L. Merritt, Jr., J. A. Dean, and F. A. Settle, Jr. Instrumental
      Methods of Analysis, Sixth Edition. D. Van Nostrand Company, New York, NY,
      10020, 1981 (pp. 249-260).

20.   Personal Communication with Gary Stafford, Warrington, Corporation, Tel. No.
      (512) 251-7771.  December 20,1993.

21.   Personal Communication with Jim Hayes, State of North Carolina Environmental
      Health Services Section, Tel. No. (919) 733-2884. June 4, 1993.

22.   Hartley, T. F. Computerized Quality Control. John Wiley & Sons, New York, NY,
      1987 (pp. 16 - 28).

23.   Daniel, C, F. S. Wood and J. W. Gorman. Fitting Equations to Data, Computer
      Analysis of Multifactor Data for Scientists and Engineers. Wiley-Interscience, New
      York, New York, 1971 (p. 32).

24.   Nelson, Lloyd S. Evaluating Overlapping Confidence Intervals. Tournal of Quality
      Technology, 21(2): 140-141, 1989.
                                      37

-------
      APPENDIX A

        XRF DATA:

           Scitec
   Warrington Uncorrected
Warrington Substrate Corrected
      PGT Uncorrected
   PGT Substrate Corrected


-------
                                                           Scitec
                                                          mg/cm2
Sample ID


20D1


20D2


120-5-B


20B2


20A2


120-2-B

17B


ICP
Analyzed
Cone
7.16


6.20


4.96


1.27


052


0.07

0.00


1/2"
Plasterboard

7.0
6.3
75
5.7
75
75

N/A

0.9
1.1
1.0
0.3
0.4
0.6

N/A
0
0
0
3/4"
Plywood

6.1
7.0
73
6.1
6.1
5.6
2.9
3.2
3.1
05
0.6
0.8
0.2
0.4
0.3

N/A
0
0
0
1/8"
Aluminum

8.3
72
7.3
6.7
8.0
7.7

N/A

1.1
1.2
0.9
05
0.4
0.6

N/A
0
0
0
1/8"
Steel

7.5
7.1
7.0
6.5
73
82

N/A

1.2
1.4
1.8
0.6
0.6
0.8

N/A
0.1
0
0
4"
Cinderblock

7.2
6.6
65
7.0
65
6.7

N/A

0.1
0
0.7
0.3
05
0.7

N/A
05
0.5
0.1
Solid
Cinderblock

8.3
8.3
8.1
8.1
7.6
8.2

N/A

4.7
5.2
4.4
4.0
3.6
1.0

N/A
3.7
4.1
3.9
Brick


6.8
63
6.1
6.7
7.1
55

N/A

03
0
0
0
0
0.1

N/A
0
0
0
5"
Concrete

4.9
42
6.0
6.1
4.4
5.6

N/A

0.9
05
0
0
0
0

N/A
0
0
0
N/A - Not Analyzed

-------
                                    Warrington Randomized Test - Unconnected Data
                                                      mg/cm2
Sample ID


20D1


20D2


20B2


20A2


120-2-B


17B


ICP
Analyzed
Cone
7.16


6.20


1.27


052


0.07


0.00


1/2"
Plasterboard

6.87
6.80
6.77
6.23
6.13
6.40
1.60
157
157
0.97
0.83
1.07

N/A

0.10
0.50
0.37
3/4"
Plywood

6.70
6.73
6.77
6.33
6.23
6.23
1.93
1.67
1.70
0.87
1.03
1.07

N/A

0.80
0.77
0.60
1/8"
Aluminum

6.90
6.77
6.67
6.13
6.23
6.37
1.43
1.27
1.17
0.87
1.13
0.37

N/A

0.40
0.43
0.17
1
1/8"
Steel

5.93
5.90
5.60
5.00
4.97
4.97
0.40
0.47
0.63
0.03
-0.20
0.07
-0.27
-0.60
-0.67
-0.30
-0.63
-0.87
4"
Cinderblock

8.27
8.40
8.37
7.77
7.60
7.67
333
2.60
2.87

N/A

1.67
1.73
1.63
1.93
1.83
2.23
Solid
Cinderblock

853
8.40
8.20
7.87
7.60
8.07
2.83
2.87
3.13
220
2.73
2.10
150
1.83
1.90
2.00
2.07
2.13
1
Brick


823
850
833
837
8.07
8.07
337
350
327
2.60
2.73
257
1.93
1.90
2.13
220
1.97
227
5"
Concrete

837
757
7.80
8.13
8.13
8.13
323
3.43
357
2.83
3.03
2.93
227
2.07
230
220
2.00
220
A - Not Analyzed

-------
                                   Warrington Randomized Test - Substrate Corrected Data
                                                         mg/cm2
Sample ID


Substrate
only
20D1


20D2


20B2


20A2


120-2-B


17B



ICP
Analyzed
Cone
_

7.16


6.20


1.27


052


0.07


0.00



1/2"
Plasterboard

0.31

6.56
6.49
6.46
5.92
5.82
6.09
1.29
1.26
1.26
0.66
052
0.76

N/A

-0.21
0.19
0.06

3/4"
Plywood

0.35

6.35
6.38
6.42
5.98
5.88
5.88
158
1.32
1.35
052
0.68
0.72

N/A

0.45
0.42
0.25
1/8" I! 1/8"
Aluminum Steel
|
-0.12

7.02
6.89
6.79
6.25
6.35
6.49
155
139
1.29
0.99
1.25
0.49

N/A

052
055
0.29

-1.47

7.40
7.37
7.07
6.47
6.44
6.44
1.87
1.94
2.10
150
127
154
1.20
0.87
0.80
1.17
0.84
0.60

4"
Cinderblock

1.31

6.96
7.09
7.06
6.46
6.29
636
2.02
1.29
156

N/A

0.36
0.42
0.32
0.62
052
0.92

Solid
Cinderblock

1.60

6.93
6.80
6.60
6.27
6.00
6.47
1.23
127
153
0.60
1.13
050
-0.10
0.23
030
0.40
0.47
053

Brick


159

6.64
6.91
6.74
6.78
6.48
6.48
1.78
1.91
1.68
1.01
1.14
0.98
034
031
054
0.61
038
0.68
5"
Concrete

1.19

7.18
638
6.61
6.94
6.94
6.94
2.04
124
238
1.64
1.84
174
1.08
0.88
1.11
1.01
0-81
1.01

N/A - Not Analyzed

-------
                                         PGT Randomized Test - Unconnected Data
                                                        mg/cm2
Sample ID



20D1

20D2


120-5-B


20B2


20A2


120-2-B


17B


ICP
Analyzed
Cone
7.16


6.20


4.96


1.27


052


0.07


0.00


1/2"
Plasterboard

6.77
6.20
6.13
6.03
5.43
6.03
3.77
3.73
3.43
153
1.70
1.30
0.77
0.80
0.83
0.77
0.67
0.53
0.07
0.30
0.50
3/4"
Plywood

6.07
6.17
6.07
5.50
5.43
5.90
3.33
3.47
353
0.90
1.13
1.23
0.83
0.77
1.30
0.33
0.27
0.27
0.10
0.23
0.37
1/8"
Aluminum

5.93
5.80
5.97
5.07
553
5.17
3.47
3.60
3.23
1.47
0.93
0.97

N/A

-0.07
0.17
0.10
0.43
0.40
0.80
1/8" Steel


7.10
6.97
7.10
7.03
6.90
7.13
3.73
4.07
4.00
1.67
1.67
157
1.20
1.20
1.27
050
0.60
050
050
050
0.47
4"
Cinderblock


N/A

5.17
5.20
4.97
353
3.73
3.70
1.40
0.80
1.47
1.17
0.93
037
0.27
053
0.63
0.40
0.70
033
Solid
Cinderblock

6.37
6.10
6.20
4.77
5.13
5.47
330
3.47
327
1.03
1.67
1.40
0.80
0.97
0.83
0.73
037
037
0.10
0.63
0.80
Brick 5" Concrete

1
5.90
553
6.23
5.00
4.70
5.40
2.93
3.40
2.93
150
1.47
2.00
0.77
0.93
1.00
033
0.23
0.67
020
0.07
027


5.17
520
523
5.13
4.83
4.83
333
2.83
2.97
133
130
1.80
0.80
0.83
0.80
0.97
033
023
0.07
020
0.10
N/A - Not Analyzed

-------
                                       PGT Randomized Test - Corrected Substrate Data
                                                          mg/cm2
Sample ID


Substrate
only
20D1


20D2


12Q-5-B


20B2


20A2


120-2-B


17B


ICP
Analyzed
Cone
	

7.16


6.20


4.96


1.27


0.52


0.07


0.00


1/2"
Plasterboard

0.29

6.48
5.91
5.84
5.74
5.14
5.74
3.48
3.44
3.14
1.24
1.41
1.01
0.48
0.51
0.54
0.48
0.38
0.24
-0.22
0.01
0.21
3/4"
Plywood

0.43

5.64
5.74
5.64
5.07
5.00
5.47
2.90
3.04
3.10
0.47
0.70
0.80
0.40
0.34
0.87
-0.10
-0.16
-0.16
-0.33
-0.20
-0.06
1/8"
Aluminum

0.68

5.25
5.12
5.29
4.39
4.85
4.49
2.79
2.92
2.55
0.79
0.25
0.29

N/A

-0.75
-0.51
-0.58
-0.25
-0.28
0.12
1/8" Steel


1.24

5.86
5.73
5.86
5.79
5.66
5.89
2.49
2.83
2.76
0.43
0.43
0.33
-0.04
-0.04
0.03
-0.74
-0.64
-0.74
-0.74
-0.74
-0.77
4"
Cinderblock

0.25


N/A

4.92
4.95
4.72
3.28
3.48
3.45
1.15
055
1.22
0.92
0.68
0.12
0.02
0.28
0.38
0.15
0.45
0.08
Solid
Cinderblock

059

5.78
551
5.61
4.18
454
4.88
2.71
2.88
2.68
0.44
1.08
0.81
021
0.38
024
0.14
-0.22
-0.22
-0.49
0.04
021
Brick


0.60

5.30
4.93
5.63
4.40
4.10
4.80
233
2.80
233
0.90
0.87
1.40
0.17
033
0.40
-0.27
-0.37
0.07
-0.40
-053
-0.33
5" Concrete


052

4.65
4.68
4.71
4.61
431
431
2,81
231
2.45
0.81
0.78
128
028
031
028
0.45
-0.19
-029
-0.45
-032
-0.42
N/A - Not Analyzed

-------