NBSIR 78-1466

Evaluation of New Portable

X-ray Fluorescent Lead

Analyzers for Measuring Lead

in Paint

A. Philip Cramp

Harvey W. Berger

Center for Building Technology

National Engineering Laboratory

National Bureau of Standards

Washington, D C. 20234

May 1978

Sponsored by:

Office of Policy Development and Research

Department of Housing and Urban Development

Washington, D.C.

NBSIR 78-1466

EVALUATION OF NEW PORTABLE

X-RAY FLUORESCENT LEAD

ANALYZERS IFOR MEASURING LEAD

IN PAINT

A. Philip Cramp

Harvey W. Berger

Center for Building Technology

National Engineering Laboratory

National Bureau of Standards

Washington, D C. 20234

May 1978

Sponsored by:

Office of Policy Development and Research

Department of Housing and Urban Development

Washington, D.C. 20410

U.S. DEPARTMENT OF COMMERCE, Juanita M. Kreps, Secretary

Dr. Sidney Harman, Under Secretary

Jordan J. Baruch, Assistant Secretary for Science and Technology

NATIONAL BUREAU OF STANDARDS. Emeat Ambler. Director
TABLE OF CONTENTS

Page

LIST OF TABLES iv

LIST OF FIGURES v

SI CONVERSION UNITS vi

ABSTRACT viii

1. INTRODUCTION 1

1.1 NEED FOR NEW INSTRUMENTS 1

1.2 INITIATION OF NEW INSTRUMENT DEVELOPMENT 1

2. REPORT OBJECTIVES 2

3. DESCRIPTION OF THE NEW LEAD ANALYZERS 2

3.1 COLUMBIA SCIENTIFIC INDUSTRIES MODEL 750, LEAD ANALYZER 2

3.1.1 Calibration of CSI Model 750 3 3.1.2 Method of Operation of CSI Model 750 3 3.1.3 Calibration Module 3 3.1.4 Calibration of CSI Model, 750 6

3.1.5 Method of Operation of CSI, Model 750 6

3.2 PRINCETON GAMMA TECH INC. XK-3 9 3.2.1 Calibration of PGT XK-3 11

3.2.2 Method of Operation of PGT XK-3 11

4. PERFORMANCE REQUIREMENTS OF INSTRUMENTS 11

4.1 DEFINITIONS OF TERMS 14

5. EVALUATIONS 14

5.1 CSI MODEL 750 14

5.1.1 Preliminary Evaluations of CSI Model 750 14

5.1.2 Final Evaluations of CSI Model 750 15

5.1.3 Procedure for Determining Accuracy and Precision

of CSI Model 750 15

5.1.4 Comments on CSI Model 750 Performance 17

5.1.5 Compliance with the HUD Contact of CSI Model 750 17

5. 1.5.1 User Qualities - Portability, Ease of

Operation, and Aesthetics 19

5. 1.5. 2 Sensitivity and Precision 20

5.1.6 Conclusions 22

5.1.7 Comments by NBS Analytical Chemists 22

ii
5.2

PGT XK-3 23

5.2.1 Preliminary Evaluations 23

5.2.2 Final Evaluations 23

5. 2. 2.1 Task IIA, Minimum Requirements 23

5. 2. 2. 2 Task IIB, Optimum Performance Levels 30

5. 2. 2. 3 Detection of Lead on Thin Substrates 32

5.2.2. 4 Temperature Effects 33

5.2.3 Field Performance 33

5.2.4 Compliance with The HUD Contract 33

5. 2. 4.1 Minimum Requirements, Task IIA 33

5. 2. 4. 2 Optimum Performance Levels, Task IIB

Task IIB 34

6. DESCRIPTION OF THE ESTABLISHED COMMERCIAL XRF, LEAD ANALYZERS 34

6.1 Princeton Gamma Tech XK-2 34

6.2 Nuclear Chicago PB-3 35

6.2.1 Probe 38

6.2.2 Data Processor 38

6.2.3 Operation 38

7. COMPARISON OF THE PGT XK-3 PROTOTYPES WITH

THE COMMERCIAL LEAD ANALYZERS 41

7.1 PGT XK-2 41

7.1.2 Portability 41

7.1.3 Calibration 41

7.1.4 Speed of Analysis 41

7.1.5 Evaluation 41

7.1.6 Accuracy and Precision 41

7.2 NUCLEAR CHICAGO PB-3 42

7.2.1 Portability 42

7.2.2 Calibration 44

7.2.3 Speed of Analysis 44

7.2.4 Ease of Operation 44

7.2.5 Accuracy and Precision 44

8. COMMERCIAL VERSION PGT XK-3 44

9. CONCLUSIONS 47

10. ACKNOWLEDGEMENTS 48

11. REFERENCES ^9

iii
LIST OF TABLES

Page

1. Performance Evaluation Results

of CSI XRF Lead Analyzer No. 106 18

2. Performance Evaluation Results

of CSI XRF Lead Analyzer No. 107 19

3. Results from CSI Lead Analyzers on References

with Lead Contents of 0.7 mg/cm2 to 1.55 mg/cm2 21

4. Accuracy of PGT XK-3's at about the

1 mg/cnr Lead Level 25

5. Substrate Effects

(Combined Data for 3 Instruments) 26

6. Instrument Trends 26

7. Measurements Exceeding Reference values

by More than +0.3 mg/cnr 29

8. Measurement of Lead on Non-Planar (Trim) Surface 36

9. Measurement of Lead in Multi-Layered Paint

on 1/2 in Gypsum Wallboard 37

10. Accuracy of XK-3 Lead Detector in the

Range of 0.5 mg/cnr to 2.5 mg/cnr 39

2 11. Accuracy of XK-3 Lead Detector above 2.5 mg/cm 40

12. Lead in Paint Measurements on Thick Substrates 43

13. Comparison of Precision between PGT XK-2 and XK-3

Prototypes at the 0.5 mg/cm2 Lead Level 42

14. Comparison between Lead Analyzers for

Accuracy and Precision at about 1 mg/cm2 Level

Part 1 45

Part 2 46

iv
LIST OF FIGURES

Page

1. CSI Model 750 Lead Analyzer

(Probe and Electronic Unit)

Ready for Use 4

2. CSI Model 750 Calibrate Module 5

3. CSI Model 750 Lead Analyzer Being Calibrated 7

4. CSI Model 750 Lead Analyzer in Operation 8

5. PGT XK-3 Lead Analyzer

Ready for Use 10

6. PGT XK-3 Lead Analyzer in Operation 12

7. Measurement Position of the PGT XK-3

on Ornate Wood Trim Coated with Lead Paint 29

8. PGT XK-2 Lead Analyzer Ready for Use 36

9. PGT XK-2 Lead Analyzer in Operation 37

10. Nuclear Chicago PB-3 Lead Analyzer

Ready for Use 39

11. Nuclear Chicago PB-3 in Operation 40

12. PGT XK-2 and XK-3 Lead Analyzers

(Size Comparison) 43

v
SI Conversion Units

The conversion factors and units contained in this report are in accordance witl

the International System of Units (Abbreviated SI for Systeme International

d'Unites). The SI was defined and given official status by the 11th General

Conference on Weights and Measures which met in Paris in October 1960. For

assistance in converting U.S. customary units to SI units, see ASTM E 380, ASTM

Standard Metric Practice Guide, available from the American Society for Testing

Materials, 1916 Race Street, Philadelphia, PA. 19103. The conversion factors

for the units found in this standard are as follows:

Length

1 in - 0.0254* meter

1 ft = 0.3048* meter

1 mil = 0.001* in

Area

1 in 2 = 6.4516* x 10 ^ meter2

1 ft 2 = 0.9290* meter 2

Volume

1 in2 = 1.638 x 10 5 meter2

1 liter = 1.000* x 10

2 meter 2

Mass

1 grain = 6.479 x 10 2 kilogram

1 ounce-mass (avoirdupois) = 2.834 x 10 kilogram

1 pound-mass (avoirdupois) = 0.4535 kilogram

Pressure or Stress (Force/Area)

1 inch of mercury (60°F) = 3376 newt on/ me ter'

4

2 2

1 pound-force/inch (psi) = 6894 newton/meter

*Exact ly

and

vi
Energy

1 inch-pound-force (in-lbf) = 0.1130 joule

Plane Angle

2

1 degree (angle) = 1.745 x 10 radian

Power

1 watt = 1.000* x 10^ erg/second

Temperature

°C = 5/9 (Temperature °F - 32)

*E xa c 1 1 y VI 1
Evaluation of New Portable

X-Ray Fluorescent Lead Analyzers for

Measuring Lead in Paint

A. Philip Cramp and Harvey W. Berger

Abstract

Portable X-ray fluorescent lead analyzers offer the most cost-effective and

adaptable means for the non-destructive detection and measurement of lead in paint

in housing. However, commercially available portable lead analyzers have had poor

accuracy and precision below lead levels of about 3.0 milligrams of lead per

square centimeter of surface area. This is particularly serious because the current

operational criteria for lead paint hazard abatement, 1.5 or 2.0 mg lead/cm^

maximum (used in many communities), is in this range. They have also performed

relatively unsatisfactorily with regard to serviceability and maintenance.

Two new portable lead analyzers based on x-ray fluorescence developed elsewhere

under HUD contracts have been evaluated. One of the new devices was found

to be unacceptable for field use because the prototypes of it were all inaccurate

and imprecise, difficult to use and maintain. They were also very bulky and

heavy. Although prototypes of the other lead analyzer did not meet all the

requirements of the HUD contract, they showed considerable improvement over

all previously available instruments in terms of accuracy, precision, ease of

operation, and portability. They did, however, have some deficiencies which

are discussed in the report.

viii
Evaluation of New Portable X-Ray

Fluorescent Lead Analyzers for Measuring Lead in Paint

1. INTRODUCTION

1.1 NEED FOR NEW INSTRUMENTS

At the present time, portable X-ray fluorescent lead detectors offer the best

and most rapid method of insitu, non-destructive lead analysis of paint films on housing surfaces. Two models of this type of instrument, made by different

manufacturers, have been widely used by housing inspectors as part of lead

poisoning control programs throughout the country. These instruments are the

Princeton Gamma Tech (PGT) Model XK-2*, and the Nuclear Chicago (NC) Model PB-3.*

These particular instruments are fairly easily operated by semi-skilled personnel

and have rapid analysis rates. Although they have performed fairly well in screening

and survey activities, they have some serious deficiencies.

The most serious deficiency of these instruments is that they are inaccurate in

determining lead levels in paint in the range of zero to 3.0 mg/cm^. The

low accuracy in this range is particularly serious because the current operational

criteria for lead paint hazard abatement, 1.5 mg/cm and 2.0 mg lead/cm^ maximum,

(used in many communities) is in this range.

Another serious deficiency of the instruments is that they are easily damaged

when they are transported. Also, the instruments consist of two rather large

components which make them awkward to handle and tiresome when in use a full

working day

.

1.2 INITIATION OF NEW INSTRUMENT DEVELOPMENT

In 1972 Rasberry [l]'*' evaluated four different types of commercial portable

X-ray lead analyzers all being used in the field for lead paint analysis

at that time. They were all made by different companies. He found them all

to have, at best, only fairly good accuracy and precision. Because of an agreement

with the manufacturers, their names were not devulged in the report.

In May 1974, HUD issued a Request for Proposal (RFP) for the development of new

lead analyzers which would meet the attributes described in Task II of the RFP.

The specifications contained in the RFP require the new instruments to be much

more accurate and precise than the PGT XK-2 and NC PB-3, easier to calibrate, much

*In no case does such identification imply recommendation or endorsement by the

National Bureau of Standards (NBS), nor does it imply that these instruments

are necessarily the best available for the purpose.

1 Numbers in brackets refer to the references in section 11.

1
lighter in weight and much more compact. Other properties such as operational

safety, speed of analysis, length of continuous operation without battery charge

(if a battery is used) , retention of accuracy and precision under abnormal environmental conditions, durability, and cost per test were required to be at least

equal to those of the two existing XRF instruments.

The recipient of a HUD contract was required to submit 3 prototypes of the new

instrument to HUD for testing. NBS in turn was assigned the responsibility, by

HUD, for evaluating the prototype in accordance with a testing and evaluation

program devised by NBS for this purpose.

Of all the proposals submitted to HUD, those which seemed to have the best potential

were from Columbia Scientific Industries Corp. (CSI), Austin, Texas and Princeton

Gamma Tech Inc. (PGT), Princeton, New Jersey. Both firms proposed developing

portable X-ray fluorescent analyzers of new types.

HUD Contract Nos. H-2191R and H-2192R were issued to CSI and PGT respectively.

Subsequently, each of these firms delveloped new XRF lead analyzers, and submitted

3 prototypes of them to HUD, who in turn delivered them to NBS for evaluation.

The new CSI lead analyzer is called CSI model 750, Portable Lead Wallpaint

Analyzer; the new PGT instrument is called PGT XK-3 Lead Analyzer.

2. REPORT OBJECTIVES

The principal objectives of this report are:

1. To evaluate the physical properties and performance characteristics

of three prototypes of the two new lead analyzers compared to the required

and optimum performance levels required in the contracts under which

they were developed.

2. To compare the physical properties and performances of the above lead

analyzers to those of the most widely used existing portable XRF lead

analyzers; the Princeton Gamma Tech XK-2 and the Nuclear Chicago PB-3.

3. DESCRIPTIONS OF THE NEW LEAD ANALYZERS

3.1 COLUMBIA SCIENTIFIC INDUSTRIES MODEL 750, LEAD ANALYZER

The CSI Model 750 lead analyzer consists of 3 components, namely a measurement

probe, electronics unit and a calibrate module. The following is a brief

description of these components, their function, and their most important parts.

2
3.1.1

The Probe

The probe is a cylindrical unit 11 in (27.94 cm) long, with a diameter of 2-3/4 in

(6.99 cm) and weighing 3.0 lbs. (1.36 kg). It contains a 25 milliCurie, cadmium

109 Cd K hard X-ray source with a half life of 470 days. It has an "X-ray window" at

the forward end with a trigger operated fail safe shutter. It contains two detector

tubes (scintillation counters) fitted with appropriate X-ray filters for isolating

and measuring the radiation given off by the lead contained in the sample being

analyzed. The probe is connected to the electronics unit by an armored cable

which transmits the electronic signals from the detectors to the electronics unit

for processing. The minimum sample size required by the CSI Model 750 is about

1-1/2 in x 2-1/2 in (3.8 cm x 6.4 cm).

3.1.2

Electronics Unit

The electronics unit is 6 in x 9 in x 11 in (15.2 cm x 22.9 cm x 27.9 cm) and

weighs about 11 lbs (4.99 Kg). It contains:

°two analog preamplifiers for processing the signals from the detector tubes;

°a microprocessor for collecting and storing data;

°a panel visual display on which is displayed the results of determinations

in mg/cm^ of lead;

°a battery with enough capacity for at least 8 hours of operation, assuming

a 50% duty cycle of measurement time to idle time;

°signal tones for indicating the operational status of the lead analyzer, if

it is idle, measuring or malfunctioning, or if the battery is approaching

exhaustion.

The probe and electronics unit together constitute the lead analyzer. The combination

weighs 14 lbs (6.35 Kg). Figure 1 shows the combination ready for use.

3.1.3

Calibration Module

This component (see Figure 2) is used only when the lead detector (the probe and

electronics units combination) is being calibrated and the electronics unit's

battery is being charged. It would not normally be taken into the field.

Consequently, its dimensions and weight are not relevant to the performance and user characteristics of the lead detector during field use.

The calibration module consists of the following principal components:

°a keyboard for entering data into the instrument, and a clearing button for

removing the data when the instrument is being calibrated;

°indicator lights which lead the operator through the required calibration

sequence

;

3
Figure 1 - CSI Model 750 Lead Analyzer (Probe and Electronic Unit)

Ready for Use

4
Figure 2 - CSI Model 750 Calibrate Module

5
°three independent battery chargers to which three instruments can be connected

for simultaneous charging;

°a probe holder in which the probe is placed when the instrument is being

cal ibrated ;

2 °a set of calibration films with lead contents from zero to about 10 rag/cm , and a lead plate about 1/16 inch (1.6 mm) thick. The calibration films are thin polyethylene films intended to simulate paint films. They contain

paint pigments such as ZnO, CaCo^j Ti02> and PbO;

°a set of reference substrates for use in calibrating the instrument. They

include wood varying from 1/4 in (6.3 mm), to 4 in (101.6 mm) thick, 1/2 in

(12.7 mm) gypsum wall board, 1/8 in (3.18 mm) masonite, 1 in (25.4 mm) plaster,

and a clay building brick 2-1/4 in (57.0 mm) thick. These materials are intended

to represent the full range of painted substrates likely to be encountered in

the field. A 1/16 in (1.6 mm) thick lead plate is also included to provide

a common calibration point for the matrices developed in the instrument when

it is calibrated.

°an operation manual.

3.1.4 Calibration of CSI Model 750

The lead analyzer must be calibrated before use. The manufacturer states that

this is necessary every six months. Calibration is a relatively long and complicated

procedure. Figure 3 shows the lead analyzer being calibrated (the probe is clamped

in position in the calibrate module).

Basically, calibration requires that a series of mathematical matrices be developed

in the instrument representing the reflected fluorescent X-rays (photons) received

by the instrument from a series of films varying in lead content, placed on

a wide variety of substrates.

The calibration films and reference substrates described above are used for this

purpose. Sets of the films are placed successively on the desired substrates and,

by following the calibration procedure described in the operational manual, the

emitted X-rays received from them by the probe are processed in the probe and

electronics unit to generate the required matrices. According to the manufacturer,

after calibration the instrument should be ready to measure accurately the lead

content of any paint film on substrates not only for which the instrument is calibrated but also on any of the infinite number of substrates that yield data within

the range covered by the matrices stored in the memory of the instrument.

3.1.5 Method of Operation of CSI, Model 750

For determining the lead content of paint applications, the lead analyzer is detached

from the calibration unit. The lead analyzer can be carried conveniently by the

operator during field use by means of a harness provided for this purpose (see

Fi gure 4)

6
Figure 3 - CSI Model 750 Lead Analyzer Being Calibrated

7
Figure 4 - CSI Model 750 Lead Analyzer in Operation

8
The procedure to be followed in determining the lead content of a paint film is

briefly as follows:

The probe head is placed against the painted surface. The probe trigger switch is

depressed and a "ready to measure" tone is heard. The probe head is then pushed

in by pressing it against the surface being analyzed until it contacts an internal

microswitch. This initiates the "measuring period" and a "measuring tone" sounds

until this period is complete. When the "measurement complete" tone sounds, the

trigger is released and the measurement head is removed from the analyzed surface.

The result is then displayed in about 5 seconds.

3.2 PRINCETON GAMMA TECH INC., XK-3 LEAD PAINT ANALYZER

All the working parts of the PGT XK-3 lead analyzer are in a single case. The

power for most of its electronic system is provided by a nine volt rechargeable

nickel cadmium (NiCd) power pack in a separate case except for a small current

required to maintain instrumental calibration. The power pack is connected

to the lead analyzer by means of a detachable cable. Figure 5 illustrates

the lead analyzer attached to the power pack, ready for operation. Its carrying

case is in the background.

The dimensions of the lead analyzer are 9-1/2 in long, 7 in high, and 3-3/4 in wide

(24.1 cm x 17.8 cm x 9.5 cm). It weighs 5.4 lbs (2.45 Kg). The power pack is

2-1/4 in x 3-1/4 in x 6 in (5.7 cm x 9.5 cm x 15.2 cm), and weighs 1.45 lbs. (0.66 Kg).

The total weight of the power pack and connecting cord is 7.1 lbs (3.22 Kg).

The principal components of the Model XK-3 lead analyzer are:

°a 10 milliCurie Cobalt 57 Co K hard X-ray source. The source has a half

life of about nine months;

°a proportional counter tube which receives the reflected photons from the

material being analyzed and converts their energy into an ionic current;

°a trigger operated shutter through which the X-rays pass;

°a preamplifier for converting ionic current into voltage;

°a linear amplifier for both shaping the current from the preamplifier and

and increasing its power;

°a liquid crystal display (read out) system on which the lead analysis

results appear;

°a small rechargeable NiCd battery for supplying an extremely small current

for maintaining the instrumental calibration;

“an electrical cord for use in charging the batteries;

The XK-3 has a CMOS (complementary metallic oxide semiconductor) circuit which

requires an extremely small electric current to operate it. This current is

about 1/100 that required to operate the PGT XK-2 commercial XRF lead analyzer.

9
Figure 5 - PGT XK-3 Lead Analyzer Attached to Power

Pack Ready for Use

10
The minimum sample size required for analysis by the XK-3 is about 2 in x 2 in

(50.8 mm x 50.8 mm )

.

3.2.1 Calibration of PGT XK-3

Calibration is necessary before the XK-3 can be used. This must be done by the

manufacturer because it involves electronic adjustments requiring special expertise.

Calibrations are made o

1 .5 mg/cm , 3.0 mg/cm

gypsum wallboard and

low to high ranges in

2 2 O b'

, and 5.0 mg/cm of lead, placed successively on wood,

steel substrate. These substrates were chosen to represent

density, which might be found as painted substrates in housi ng.

3.2.2 Method of Operation of PGT XK-3

The operation of the XK-3 is very simple. First, the batteries should be charged

for about 8 hours. The battery pack is then attached to the lead analyzer, and

the instrument is ready for use. Attached to the battery pack is a metal clamp

for fastening it to the belt of the operator. A lock switch on the lead analyzer

is released to allow the instrument switch to be turned on. The lead analyzer is

then placed on the material to be analyzed and the handle depressed fully to set

the instrument in operation. The lead analysis takes about 30 seconds, and the

results appear on the liquid crystal display. If the battery pack power approaches

exhaustion, a warning signal of three dots appears on the display.

The highest reading this lead analyzer can indicate is 10.0 mg/cm . Any lead

content higher than this amount is recorded on the display as 10.0 mg/cm^. The

inability of the instrument to indicate lead contents higher than 10 mg/cm z is

not serious because any lead level over 2.0 mg/cm^ is generally regarded to be

hazardous. Figure 6 shows the XK-3 in operation.

4. PERFORMANCE REQUIREMENTS OF THE INSTRUMENT

The HUD contracts for both the Columbia Scientific and Princeton Gamma Tech

experimental XRF lead analyzers presented two sets of design specifications.

These are identical in each contract. The first set, as described in Task IIA

of the contracts are minimum performance levels that the instruments must meet

,

which are as follows:

1) Safety - if the detector system involves the use of radioactive materials,

it shall be fully shielded so as to protect occupants and/or operator.

2 2) Sensitivity and Precision - Minimum sensitivity 1.0 mg lead/cm . Precision ± 0.2 mg lead/cm^ at 1.0 mg/cm^.

3) Adaptability - shall measure 50% of the total lead through 20 coats of

paint on planar or curved surfaces.

11
Figure 6 - PGT XK-3 Lead Analyzer in Operation

12
4) Use - shall be readily operated by semiskilled personnel.

5) Cost per Detection - shall not cost more than $2.00 per analysis.

The second set of requirements, as described in Task IIB, are optimum performance

levels which the contractor is encouraged to use his best efforts to achieve.

Those optimum performance levels are as follows:

1)

Sensitivity, Accuracy and Precision - the system shall be capable of quantitative determinations to a lower limit of 0.5 mg lead/cm . For the range

of 0.5 to 2.5 mg/cm , the system shall measure lead within + 0.1 mg/cm^

for 9 out of 10 measurements and within + 0.2 mg/cm^ for 10 out of

10 measurements. In the range of 2.5 to 10 mg/cm z the system shall

be capable of measuring lead levels to within +10% for 9 out of 10

measurements and within +20% for 10 out of 10 measurements. In the “2

range of 0.1 to 0.4 mg/cm the system shall be able to detect the

presence of lead in 9 out of 10 measurements with no specific accuracy.

2)

Adaptability - the system shall be capable of detecting at least

80% of the total lead present in a coating of at least 20 layers of

paint

.

The contract described 10 additional attributes for which the prototype lead

detectors are intended to achieve specific performance levels. They are:

3) Service Life

4) Durability

5) Maintenance and Use

6) Sensitivity to Temperature

7) Sensitivity to Humidity

8) Cost per Detection and Measurement

9) Sample Requirement

10) Portability

11) Speed of Analysis

12) Aesthetics

The procedures used for evaluating the CSI and PGT prototypes are contained

in an NBS manual entitled "Manual for Evaluating Prototype X-Ray Fluorescent

Lead Detection Instruments for the Lead Paint Poisoning Project."

This report presents data and analyses resulting from an evaluation of the CSI

Model 750 and the PGT XK-3 prototype lead detectors relevant to both the minimum

performance levels and optimum performance levels, in the areas of sensitivity,

accuracy, precision, adaptability, and safety. It also includes evaluation of

13
the prototypes for optimum performance requirements selected by the HUD Lead

Paint Poisoning Project Manager from the above Task IIB list of requirements

name ly

1) Temperature

2) Sample Requirement

3) Portability

4) Speed of Analysis

5) Aesthet ics

4.1

DEFINITIONS OF TERMS

For the purpose of this report the following definitions will be used:

a. Sensitivity - a positive instrumental response to the presence of a predetermined level of lead. The response need not be reproducible nor accurate. It need only be a positive indication of the presence of lead.

b. Minimum Sensitivity - the limit of detection, or the lowest lead content

which will elicit a positive instrumental response to the presence of

lead

c. Accuracy - the degree to which the instrument measures a known amount

of lead in a reference material or other standard. The accuracy of an instrument may be determined as a function of either a single measurement

or as a function of the average of replicate measurements.

d. Precision - the degree of repeatability of replicate measurements on the same test sample. An instrument which has a high degree of repeatability

does not necessarily have good accuracy.

5. EVALUATIONS

5.1

CSI MODEL 750

5.1.1

Preliminary Evaluation

One of the 3 prototypes (No. 106) and the calibration module fabricated under

the HUD contract were first received at NBS in June 1976.

Firstly, the prototype was tested for radiation safety. The radiation levels

emitted by it were determined by the staff of the NBS Health Physics Laboratory.

14
Their findings were that the prototype exhibited "no significant" radiation

emission or radioactive contamination when exposed to both the Radiation Survey

Meter Test, and the Radiation Smear Test.

Attempts at NBS to calibrate instrument No. 106 failed and it was returned to

CSI along with the calibration module for some electronic modifications. Following

this, CSI calibrated it and the other two prototypes, No.'s 107 and 108, and sent

all three to NBS in October 1976 for evaluation.

During the period of October 7 to December 10, 1976, NBS evaluated the performance

of the three prototypes. Instruments 106 and 107 were very inaccurate and imprecise

while No. 108 was inoperable and had to be returned to CSI for repairs.

5.1.2 Final Evaluation of CSI Model 750 - Accuracy and Precision

During the period of December 15 to 17, 1976, 106 and 107 were evaluated at NBS

by NBS personnel assisted by a member of CSl's technical staff, after their

radiation safety had been assured.

No. 106 still had not been repaired at that time, so it was not evaluated.

Further evaluations of No.'s 106 and 107 were made by NBS personnel in January

and February, 1977.

5.1.3 Procedure for Determining the Accuracy and Precision of CSI Model 750's

The accuracy and precision of CSI lead analyzers No.'s 106 and 107 were determined,

using three series of reference materials of known lead levels: CSI references,

NBS reference coatings, and paper backed lead paint references (prepared for

HUD's use) on different substrates. The temperature of the test area was 73° F

+ 4°F, and the relative himidity 50% + 5%.

The following is a detailed description of the series of references and substrates

used in the evaluations of the CSI analyzers No.'s 106 and 107.

o 1) CSI References, lead content mg/cm

zero

0.69

1.55

3.11

6.69

As recommended by CSI, each reference used had a total thickness equivalent to

about 8 layers of paint. The references were made up of films containing

lead contents of the desired amount, and additional non-leaded films, as

15
necessary, p] aced on top of the leaded film to give the desired thickness. This

supposedly eliminated any effect reference thickness variation might have on instrumental accuracy or precision.

Each of the above references was placed on the following substrates for the

evaluations

1/8" plywood (unsealed)

1/2" gypsum wallboard

0.014" Mylar sheet

2) NBS References

o Lead Content (mg/cm ) Substrate

1.05 1/8" (3.18 mm) plywood (unsealed)

1.06 1/8" (3.18 mm) plywood (sealed)*

0.70 1/2" (1.27 mm) gypsum wallboard

0.82 0.014" (0.355 mm) Mylar sheet

0.88 0.035" (0.89 mm) steel sheet

The NBS references were used to determine not only how well the CSI analyzers performed, but also whether or not they met the HUD contract requirement that they be

capable of measuring within + 0.2 mg lead/cm^ of a nominal 1.0 mg/cm^ standard.

2 3) Paper backed lead paint references for field use, mg lead/cm

0.60

1.50

3.0

Each of the above references was placed on the following substrates for the

determinations

1/8" (3.18 mm) plywood (unsealed)

1/2" (12.7 mm) gypsum wallboard

0.014" (0.356 mm) Mylar sheet

Differences in the material composition of the table tops on which the determinations might be carried out were found to cause appreciable differences in the results.

*Sealed with a varnish primer

16
To eliminate this variable, all determinations were conducted on a 3/4" (19.1 mm)

thick wood pull-out writing board of a desk.

Ten replicate measurements of each CSI, NBS , and painted paper backed references,

on the substrates indicated, were made with each instrument. The results appear

in Tables 1 and 2.

The relative accuracy of the instruments is determined from the Difference

(Col. 4) between the Mean (Col. 2) and Standard Value (Col. 1) (D=M-SV). The precision is indicated by the standard deviation (Col. 3).

Column 5 lists the number of measurements departing from the mean (not the standard

value) by more than + 0.2 mg/cm. These data (in Col. 5) also give an indication

of the precision of the instruments and their conformance to the HUD contract

specification. 5.1.4 '

Comments on CSI Model 750 Performance

CSI No. 106

This analyzer generally exhibited poor accuracy and precision. For example,

the means of the determinations on all reference films and coatings with plywood

as substrate were significantly lower than the standard values of the references

and coatings. This was also true for the results with Mylar as the substrate,

except for one case where the result was considerably higher than the standard

value. The means of the determination with gypsum wallboard as the substrates

were too high except for two instances where the means were too low. The

determinations with steel as substrate were much too high.

CSI No. 107

This analyzer had the same shortcomings as No. 106 and was also generally

inaccurate and imprecise. The results from the determinations with steel and gypsum

as substrates resembled those from No. 106 in that they were generally higher

than the values of the references. With Mylar as substrate the results were too

high. This was a decided contrast to results from No. 106 which were too

low. The results with plywood as substrate ranged from lower to much higher than

the standard values fo the references. There were no definite error trends in

the results from either of the analyzers.

5.1.5 Compliance with the HUD contract

5. 1.5.1 User Qualities - Portability, Ease of Operation and Aesthetics

(a) Portability

The CSI XRF Model 750 lead analyzer consists of an electronic unit weighing

11.5 lbs. (5.23 kg) and a probe weighing 2.9 lbs. (1.31 kg) connected by an electrical cable. Thus, it weighs more than the 10 lb (4.5 kg) maximum weight

17
Table I Performance Evaluation Results

of CSI XRF Lead Analyzer No. 106

Response Time: 18 secs . (1) (2) (3) (4) (5)

Standard Mean Standard Difference Determination*

Value (SV) (m)

2 Deviat ion (D=M-SV) > ± 0.2

mg/cm^ lead mg/cni (SD) mg/cra^ mg/cm z mg/cni lead

CSI Reference films

1/8" plywood unsealed

0 0 0 0 0 0.69 0.56 0.22 -0.13 2 1.55 1.43 0.20 -0.12 3 3.11 2.44 0.31 -0.67 6 6.69 5.54 0.31 -1.15 5 1/2" Gypsum wallboard

0 0.21 0.21 0.21 4 0.69 1.06 0.28 0.37 4 1.55 2.24 0.35 0.68 5 3.11 3.65 0.38 0.54 7 6.69 6.87 0.43 0.18 6 0.014" Mylar sheet

0 0 0 0 0 0.69 0.08 0.11 -0.61 1 1.55 0.66 0.25 -0.89 3 3.11 2.26 0.27 -0.85 2 6.69 5.45 0.15 -1.24 1 NBS References

1/8" plywood (unsealed)

1.05 0.27 0.22 -0.78 4 1/8" plywood (sealed)

1 .06 0.26 0.23 -0.80 3 1/2" Gypsum wallboard

0.70 1 .17 0.29 0.47 4 0.014" Mylar sheet

0.82 1.48 0.28 0.66 5 0.035" Steel sheet

0.88 2.85 0.21 1 .97 3 Paper backed lead paint reference films

1/8" plywood (unsealed)

0.60 0.16 0.18 -0.44 2

1 .50 1.13 0.26 -0.37 5 3.00 2.59 0.34 -0.41 5 1/2" Gypsum wallboard

0.60 0.37 0.21 -0.23 3 1.50 1 .55 0.36 0.05 6 3.00 2.87 0.38 -0.13 4 0.014" Mylar sheet

0.60 0.16 0.21 -0.44 2 1.50 1.38 0.35 -0.12 5 3.00 2.40 0.22 -0.60 4

*No. of determinations exceeding M + 0.2

1 inch = 25.4 mm

18
Table 2 Performance Evaluation Results

of CSI, XRF Lead Analyzer No. 107

Response Time 20 secs.

(1)

Standard

Value (SV) O mg/cm lead

(2)

Mean

(M)

mg/cm^

(3)

St andard

Deviation

(SD) mg /cm 2

(4)

Difference

(D=M-SV)

mg/cm^

(5)

Determinat ions*

> ± 0.2 o mg/cm lead

CSI Reference films

1/8" plywood (unsealed)

0 0 0 0 0 0.69 0.52 0.59 -0.17 9 1.55 1.23 0.44 -0.32 5 3.11 3.37 0.35 0.26 5 6.69 7.59 0.20 0.90 2 1/2" Gypsum wallboard

0 0.48 0.24 0.48 3 0.69 1.16 0.56 0.64 5 1.55 2.02 0.39 0.47 5 3.11 3.44 1.29 0.33 7 6.69 7.63 0.58 0.94 8 0.014" Mylar sheet

0 0.32 0.31 0.32 4 0.69 0.76 0.35 0.07 4 1.55 1.44 0.35 -0.11 7 3.11 3.52 0.32 0.41 6 6.69 6.95 0.32 0.26 5 NBS References

1/8" Plywood (unsealed)

1.05 0.67 0.33 -0.38 8 1/8" Plywood (sealed)

1.06 1.07 0.31 0.01 6 1/2" Gypsum wallboard

0.70 1.78 0.24 1.08 3 0.014" Mylar sheet

0.82 1.37 0.29 0.55 3 0.035" Steel sheet

0.88 2.86 0.28 1.98 6 Paper backed lead paint references

1/8" plywood (unsealed)

0.60 1.76 0.34 1.16 4

1 .50 2.15 0.40 0.65 8 3.00 3.82 0.28 0.82 7 1/2" Gypsum wallboard

0.60 1.08 0.28 0.48 4 1.50 2.15 0.40 0.65 8 3.00 3.82 0.28 0.82 6 0.014" Mylar sheet

0.60 0.85 0.39 0.25 5 1.50 2.20 0.18 0.70 3 3.00 4.26 0.31 1.26 4

*No. of determinations exceeding M ± 0.2

1 inch = 25.4 mm

19
criterion in the HUD contract. In the opinion of a number of operators, the

analyzer is excessively heavy and bulky which makes it awkward to carry and

operate, especially for long periods of time.

Although the probe is rather light and easy to carry, a pushing force of about

8 lbs (3.63 kg) is required to depress its spring-loaded measurement head to

initiate measurement. The measurement head must be held in the depressed position during the measurement period of about 20 seconds. This is fatiguing to the

operator, especially if the measurement head binds when it is being depressed,

which occasionally happens.

(b) Ease of Operation

The operational procedure of the CSI lead analyzer is relatively easy. Consequently, it meers the minimum performance level requirement of the HUD specification which specifies that the instrument "shall be readily operated by

semiskilled personnel." However, the calibration procedure for this instrument

is complex and too difficult to be entrusted to semiskilled personnel. It would be necessary to send the lead analyzer to CSI for this purpose.

(c ) Aesthetics

The HUD contract requires that the instrument shall not emit "noxious fumes"

or loud noise, produce black marks, gouges or excessive holes on the surface

being examined.

The CSI lead analyzer does not emit fumes, but the tonal signal system (a

beeper") which indicates by means of pulsating tones what its operational

status of action is (i.e., measuring, turned on but not measuring, etc.) can

be annoying to the operator or other people in the vicinity.

The facing of the probe is steel and contains some recessed screws. The facing

frequently leaves grey-black marks on the surfaces being analyzed, and the screw

heads occasionally scratch them.

5. 1.5. 2 Sensitivity and Precision

The HUD contract requires the following performance of newly developed X-ray

Fluorescent lead detectors .

“Minimum sensitivity 1.0 mg lead/cm4

O n “Precision + 0.2 milligrams lead/cm at 1.0 mg/cnr

With regard to the requirement on precision, some interpretation is required. If

the word precision was intended in the original contract to be synonymous with

ccuracy with which the instrument measure the true lead content at a nominal

i mg lead/cm , with the deviation of + 0.2 rag/cmz from the true value, reference

to Table 3 (an abstract from Tables 1 and 2) shows that in only 5 out of 22 cases did the means of 10 repetitive measurements meet that requirement. Even

in those 5 cases, the number of single determinations that deviated from the

20
Table 3

Results

From

CSI

Lead

Analyzers

on

References

with

Lead

Contents

of

0.70

mg/cnr

to

1.55

mg/cra

k . . ... co

(0

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03 CM o C *<N

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13 13 00 a ^ S • r* 13 H a

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co

C XN

lj

u coa CM OO OO 40 OO 40O OC U 1 o CO <3" CO o o 40 ON CO NO r-- u £

|| Of o O

O o o o o O r**» y-4 o a 1 1 1 o • r4 Q Oz CM x c a u o o c CO on m co ON oo o 00

13 -X0 LJ Of <t CO CO CO CO CM CM CM co G 03 a

CO -H o o o O o o O

O o o o 3- AJ > /-s CO 13 Q

CO

Q CO c

Dl

a: CM

xi c ^ a co CM r- oo r"- n£> 40

O

03

XO CM o vO

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CO

X oo CM

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O

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O co o r-4 a; US'-. ^ li oc O o o O o o o o o o

4-4

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a 1 1 1 1 1 1 nOO Q Oz CM X C 0

4-1 34

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O c CO -H \ o in

m CM CO O' oo vO NO uo

R c 03

g CNJ CO CM CM CM CM CM CM CM CO co 3u O o o O O o O O O o o

44 CO

u

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03 S O CM kD CM CM *-4 00 3-i r— 40 CO

h4 13 CO £ 00 ,—(

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X 3- CO VCO CO 03 CO 13 CO o. CO CO a i; O 13 O 4- 13 o 4-i CO X 13 CO cO x> 13 13 X CO X 13 • r4 c 13 G 13 13 13 CO C 13 4-4 3 x 3 CO -G X 13 3 X

CO cn CO CO CO CO co CO X3 13 5 13 5 5

X) > 03

OX 3-uXX 3-

X

X

3- CO 13 c o CO

C o O

B CO 13 13 o CO 13 o 13 o P O 13 -X o

3- 3 40 c/3m So

m 3- 5 40 5 x co

O X. CM 4-< 00

U 5 o CO

O So

O

C 13CM 13 SO 40 cl

m S 40 13 so o SoO CL r- S co CO 00 CO Co 40 CL 40

X 40

CO 3 a 4-1 Sn • 44 >> • CQ Co • CL r- O r-4 1) CL i-4 CL r—J o o r o = o CL r-4 O r-4 CO at, <t OS 40 3- CO 13 a

1-4 00 CM o CO oo oo CM o CL OO o

CO CQ cO u ’-1 o z r-4 O o CL o

CMo

+1X

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13

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13

coco

cdc1

0)uX

M—I o

21

inch =

25.4
mean by more than + 0.2 mg/cm^ of the mean, then the standard deviations shown

in Table 4 indicate that in all cases but 2, the requirement was not met.

In short, by any reasonable definition or interpretation the performance of the

CSI instruments fail to meet the letter, or intent of the HUD requirements as expressed in the contract document.

In addition to their failure to accurately measure the lead contents of the three

series of reference materials, the two CSI instruments indicate severe limitations

with regard to consistency between themselves. For example, reference to Table 3 shows comparisons between instruments numbers 106 and 107 in measuring the paper

backed lead paint references. The differences ranged as high as about 1.8 mg/cm^

on identical reference panels.

Because the CSI Model 750 prototypes failed to meet the accuracy and precision

specifications of the HUD contract, and lesser requirements such as portability

and asesthetics, further testing as required by the HUD contract was abandoned

for these instruments.

5.1.6 Conclusions

As far as can be determined there are recalibrations will resolve the basic

instruments. There is no consistency

to preferential accuracy or precision

a position to comment on retention of

previous experience seems to indicate

no set patterns that indicate that mere accuracy and precision limitations of these

between the two instruments with regard

on any particular substrate. We are not in

the calibration of the instruments although

that that will be a rather frequent problem

HUD should consider the inaccuracy of the instruments, their generally unsatisfacto

user characteristics, the need for a calibration module and the apparent need for

continued developmental work, in making any further decisions with regard to these

instruments

5.1.7 Comments by NBS Analytical Chemists

Three analytical chemists from the Analytical Chemistry Division who have expertise

in X-ray fluorescent analyzers were asked for a critique of the CSI analyzers.

All believe that the principles by which the analyzers operate are technically

sound. However, it appeared to them that a considerable amount of research and

redesign on the analyzers might be necessary to bring their accuracy and precision

to an acceptable level.

22
5.2 PGT XK-3

5.2.1 Preliminary Evaluations

In all, three preliminary evaluations of the three PGT XK-3 prototypes. No.'s 101,

102, and 103 were conducted for radiation safety, and accuracy and precision by

NBS during the period of July 15, 1976 to January 31, 1977. Standard paint films

of precisely known lead contents on various substrates were used for these

evaluat ions

.

The first preliminary evaluation revealed that not only were all the prototypes

very inaccurate, but also the two small 9 volt alkaline nonrechargeable batteries

located in the instruments became exhausted after only 3 to 4 hours of use. Obviously, this cannot be tolerated in field service.

Consequently, PGT not only recalibrated the instruments, but also equipped them

each with a 12 volt rechargeable nickel cadmium (NiCd) power pack connected to

the XK-3 with a cable. One of the small 9 volt batteries was retained to supply

the minute amount of current required to maintain instrumental calibration.

The second evaluation revealed that the accuracy and precision of No. 101 were quite good, but were poor for the other two. It was decided by PGT that the

poor accuracy and precision may have been caused by the 12 volt power pack not

having sufficient storage capacity for use with the XK-3. Consequently, this

power pack was replaced by a 9 volt type with a much higher storage capacity.

The prototypes were then recalibrated and submitted to NBS for reevaluation.

5.2.2 Final Evaluation

In the final evaluation the prototypes were first submitted to appropriate test

methods in the "Manual for Evaluating Prototype X-ray Fluorescent Lead Detection

Instruments for the Lead Paint Poisoning Project" to determine whether they met

the requirements in Task IIA and B discussed in Section 4.0 of this report.

The following is a discussion of the results.

5. 2. 2.1 Minimum Requirements Task IIA

1 . Safety

The NBS Health Physics Laboratory found that the XK-3 prototypes exhibited

"no significant" radiation emission or radioactive contamination when exposed

to both the Radiation Survey Meter Test, and the Radiation Smear Test.

2 . Minimum Sensitivity

2 The minimum sensitivity required by the HUD contract is 1.0 mg lead/cm . The PGT XK-3 prototypes consistently gave a positive indication of the presence

23
2 of lead at a level of 1.0 mg/cm , on a variety of substrates such as wood,

gypsum board, Mylar and steel.

3 . Precision

2 The HUD specification requires a minimum precision of +0.2 mg lead/cm at

1.0 mg/cm . It is our interpretation that the word precision, as it is

used in the HUD specification, refers to what we have defined as accuracy,

(see section 4.1). Therefore, the following data is directed at presenting

the evaluation of the XK-3's with regard to their ability to accurately measure

lead in paint at or about 1.0 mg/cm“. If our interpretation is in error,

the following data is still appropriate for evaluating the repeatability of

the instruments in measuring lead at a nominal 1.0 mg/cmz level.

The data in Table 4 serve for several analyses. For example, column 3 shows

the difference between the known lead content of the reference materials prepared

by NBS and the averages of ten replicate measurements made with each of the

three prototype instruments on five different substrates. Of 15 series of

measurements, all the measurements but 5 exceeded a difference of + 0.2 mg lead/cm^

from the actual lead content. Furthermore, out of a total of 150 replicate measurements with the three detectors, 100 measurements exceeded + 0.2 mg/cm^ of the

actual lead contents of the reference materials. Using the averages of the observed

replicate measurements, 41 out of a total 150 measurements exceeded + 0.2 mg/cn/

of the observed average readings as listed in column 2 of Table 1. In summary,

therefore, if the required precision statement is taken to mean accuracy, only

50 of 150 measurements, on reference materials having a nominal value of approximately 1 mg/cm , were found to be within + mg/cm^ of the actual lead value.

The XK-3 lead detectors cannot be calibrated by the operator: the calibration

is accomplished by the manufacturer. As part of the calibration process, the

detectors are tuned to a particular substrate. X-ray fluorescent lead detectors

are supposedly sensitive to variation in substrates both with regard to the nature

of the substrate and substrate thickness. Table 5 presents a compilation of

the data in Table 4 in a manner intended to highlight the effects of the substrate

on the measurement capability of the XK-3 lead detectors.

The results for instrument No. 102 are clearly different from those of the other

two instruments. We believe that recalibration of instrument No. 102 would lead

to a substantial improvement in its accuracy, at least insofar as the average

of replicate measurements is concerned.

NBS was informed by Princeton Gamma Tech, Inc. that the limit of accuracy to be

expected of the XK-3 instrument is + 0.3 mg lead/cra^. Table 7 shows that 54

out of 150 measurements made with the three prototypes on the 5 substrates

shown in Table 4 exceed +0.3 mg/cm^ of the lead content of those reference materials.

24
Table 4 Accuracy of PGT XK-3’s at about the 1 mg/cm^ Lead Level

Substrate

(1)

Standard

Value (SV)

mg/cmz lead^ a '

(2)

Mean

(3)

Difference

(D=M-SV)

mg/ cm

z

(4)

Determinations

> + 0.2 mg/cm

of (1)

(5)

Determi nat Ions

> + 0.2 mg/cm

~of (2)

XK-3 No. 101

Unsealed wood 1.05 1.07 +0.02 5 b

Sealed wood 1.06 0.93 -0.14 5 5

Gypsum board 0.70 0.75 +0.05 3 0

Mylar 0.82 1.17 +0.35 9 1

Steel 0.88 0.91 +0.03 3 3

XK-3 No. 102

Unsealed wood 1.05 0.84 -0.21 7 2

Sealed wood 1.06 0.58 -0.48 10 2

Gypsum board 0.70 0.38 -0.32 10 0

Mylar 0.82 0.62 -0.20 6 5

Steel 0.88 0.55 -0.33 7 3

XK-3 No. 103

Unsealed wood 1.05 1.00 -0.05 7 3

Sealed wood 1.06 0.64 -0.42 9 1

Gypsum board 0.70 0.85 +0.15 4 3

Mylar 0.82 1.01 +0.19 7 4

Steel 0.88 1.08 +0.20 7 3

The lead contents of the reference materials used by NBS were determined by chemical

analysis using Atomic Absorption Spectrometry.

^

The average of 10 replicate measurements. The instruments read to 0.1 mg/cm^:

an additional calculated significant figure is used here for convenience.

23
Table 5 Substrate Effects (Combined data for 3 instruments)

Substrate

Lead

Content

(a)

Mg Lead/cm"

Gross

Average

(b) 1

Average

Difference

(a-b)

Unsealed wood 1.05 0.97 -0.08

Sealed wood 1.06 0.72 -0.34

Gypsum board 0.70 0.66 -0.04

Mylar 0.82 0.93 +0.11

Steel 0.88 0.85 -0.03

l Average of 3 averages in Column (2) Table 4.

The second column in Table 5 presents the gross averages of readings for all 3 lead detectors for each particular substrate. The average difference between the

actual lead content and the average of 30 replicate measurements is shown in the

third column of the table. The greatest difference is obtained for measurements

on sealed wood. There is no obvious reason for this effect especially since the

average difference obtained for measurements on unsealed wood is comparable to

the averages for gypsum wallboard, Mylar and steel. The data in Table 5 leads

us to conclude that the XK-3 lead detectors do not show extreme trends for particular

substrates. This conclusion is supported by the data in Table 6 (based on all

of the data in Table 4) which shows general trends in the measurement response

of the three instruments.

Table 6 Instrument Trends

O Mg Lead/cm^O Mg Lead/cm^

Arithmetic Sum Algebraic Sum

Instrument of Difference 1 of Differences

No. 101 0.6 +0.4

No. 102 1.5 -1.5

No. 103 1.1 +0.1

^Differences in Column (3) of Table 4.

26
Table 7 Measurements Exceeding Reference Values by More

than + 0.3 mg/cm^*.

XK-3 Prototype

Substrate 101 102 103

Unsealed wood l Sealed wood 3 Sypsum board 0

Mylar 6 Steel 3

3

9

54

4

172

33

. O Sum exceeding + 0.3 mg lead/cm 54 (out of 150 measurements)

*10 replicate measurements on each substrate using each instrument.

The distribution of differences between known lead values and observed averages

leads us to believe that instruments No. 101 and 103 cannot be significantly

improved by recalibration. Although we believe that instrument No. 102 can be improved, the overall accuracy or ability to read within + 0.2 mg of

a known value is not expected to increase significantly.

4. Adaptability

The performance requirements for adaptability relate to two essentially

different parameters. One is the ability to detect lead paint on nonplanar surfaces, such as ornate wood trim, and the second is the ability

to detect lead paint which has been covered by as many as 20 layers of nonleaded paint. The minimum performance requirement as stated in the HUD

contract is interpreted as requiring an instrumental capability to detect

50% of the total lead present in both multi-layer paints and in coatings on non-planar surfaces. Table 8 indicates the degree to which the XK-3 prototypes meet the requirements relating to measurement capability on non-planar

surfaces

.

27
Table 8 Measurement of Lead on Non-Planar (Trim) Surfaces*

Observed

Trim

Specimen Position

Measurement

Direction'*'

Lead Cont

(mg/ cm"

:ent Average

(mg/cin )

% Lead

Detected

1 a T 1.1 0.3 27

2 a T 3.0 3.8 > 100

2 b L 3.0 3.3 > 100

2 c L 3.0 1.4 47

2 c L 1.5 0.6 40

3 a T 3.0 2.6 87

3 b L 3.0 2.4 80

3 a T 1.5 1.4 93

3 b L 1.5 1.6 > 100

4 a T 17.2 10.0 58

''Transverse to trim (T) , Longitudinal to trim (L)

instrument No. 101

Measurements were made on ornate wood trim samples which are shown in crosssections in Figure 7. The placement of the lead detector obviously has a bearing

on the observed measurement. Surfaces which are parallel to the plane of the

instrument's window seem to produce more accurate measurements than skewed surfaces

even when they are displaced from the instrument by an air gap. The instrument

has a circular window 1.75 inches (4.45 cm) in diameter and is therefore bridging

a complex surface in most of the measurements on ornate wood trim. In the case

of the wood trim containing 17.2 mg lead/cm^ the instrument satisfactorily detected

the lead present by indicating 10.0 mg/cm^ (which is the highest reading the

instrument can make).

28
POSITION

A

TRIM SPECIMEN 1

POSITIONS

TRIM SPECIMENS 2 AND 4

POSITIONS

A B

\ I

TRIM SPECIMEN 3

Figure 7 - Measurement Positions of the PGT XK-3 on Ornate Wood

Trim Coated With Lead Paint

29
The performance of the XK-3 prototype in measuring and detecting lead in multi-layer

paint films is shown in Table 9 below.

Table 9 Measurement of Lead in Multi-Layered Paint* on 1/2 in Gypsum Wallboard

Number of Lavers

Lead Content

(mg/cnr)

Average Instrument

Reading (10 replicates)

Number of

Readings

< 50%

4 0.17 0.24 3 8 1.31 1.45 0

15 2.03 2.14 0

20 2.97 2.71 0

instrument No. 101

5. 2. 2. 2 Optimum Performance Levels Task IIB

1. Accuracy

The HUD Contract defines optimum performance levels for accuracy as follows:

2 For the range 0.5 to 2.5 mg lead/cm 4 + 0.1 mg/cmz for 9 out of 10 replicate measurements

+ 0.2 mg/cm^ for 10 out of 10 replicate measurements

2 For the range 2.5 to 10 mg/cm

+ 10% for the 9 out of 10 replicate measurements

+ 20% for 10 out of 10 replicate measurements

Table 10 presents the results of the evaluation of the XK-3 prototypes relative

to the accuracy requirements stated above. Reference materials containing 0.6,

1.5 and 2.1 mg lead/cm^ placed on wood, gypsum wallboard, and steel substrates

were used for this purpose. Ten replicate measurements were made for each instrument

using each of the three reference materials on each of the three substrates. The

data in Table 10 indicate that in no case did the XK-3 prototype instruments meet

the stated requirements for accuracy in the range 0.5 to 2.5 mg/cm . An inspection

of the data further indicates that instrument No. 102 is not operating as accurately

as instruments No. 101 and 103, as previously stated.

The results for instrument No. 101 seem to indicate a substrate effect such that

measurement accuracy on the steel substrate is not as high as for the wood and

gypsum wallboard substrates. However, the results for instrument No. 103 are contradictory and seem to indicate that the accuracy on the steel substrate is

better than that for the gypsum wallboard and wood. The overall conclusion that can be reached is that individual instruments may be substrate sensitive due to

their calibration or tuning.

30
Table 10 Accuracy of XK-3 Lead Detector in the Range 0.5 mg lead/cm^ to 2.5 mg/cm^

Reference

Material

Instrument Lead Content

Number of Measurements*

within + 0.1 mg/cm

Gypsum

Wood board Steel

Number of Measurements O within + 0.2 mg/cm

Gypsum

Wood board Steel

101

102

103

0.6 5 1.5 4 2.1 4

0.6 5 1.5 5 2.1 0

0.6 1 1.5 3 2.1 1

2

5

3

3

6

2

5

50

32

1

10

0

24

5

68

6

8

50

23

4

6

75

3

76

6

8

5

5

3

1

3

6

5

*10 replicate measurements for each reference material and substrate

Table 11 presents data directed at the requirement for accuracy in the range above

2.5 mg/cm . In no case did the instruments meet the requirements of falling within

+ 10% of the known value 9 out of 10 times when a reference material containing

3.0 mg/cnr was used. Using the second criterion of + 20%, instrument No. 103

satisfactorily met that requirement for both the wood and gypsum board substrates.

Table 11 Accuracy of XK-3 Lead Detector Above 2.5 mg lead/cm2

Instrument

Number of Measurements*

within + 10% of 3.0 mg/cm

Gypsum

Wood board Steel

2 Number of Measurements*

within + 20% of 3.0 mg/cm

Gypsum

Wood board Steel

101

102

103

4 3

0 0

6 8

9 8 8

0 7 0

10 10 9

*10 replicate measurements for each reference material and substrate

31

moo
2. Sensitivity

The minimum performance requirement for sensitivity states that the lead detectors

shall be capable of lead detection in the range of 0.1 to 0.4 rag lead/cin with

no particular degree of accuracy. On two series of measurements using 1/2 in

gypsum wallboard reference material containing 0.25 mg lead/cm , instrument No

101* failed to give a positive indication of the presence of lead in 20% of the

measurements

3. Adaptability

The minimum performance requirement for adaptability, states that the lead detectors

shall be capable of detecting 80% of the total lead present in a coating containing

20-layers of paint. In an evaluation of instrument No. 101,* using the reference

materials listed in Table 9, it was found that the instrument failed to detect

80% of the lead present in the 4-layer material 3 out of 10 times, in the 8-layer

material, in 1 of 10 measurements; and successfully detected at least 80% of the

lead in all cases for both the 15-layer and 20-layer reference materials. Thus,

the detection adaptability rating was the same for the 80% level as for the 50%

level

5. 2. 2. 3 Detection of Lead On Thin Substrates

Although no consistent trend was observed for substrate effects due to the use

of one type of substrate material or another, consistent substrate effects were observed relative to the thickness of the substrate being measured. These substrate

effects were apparently due to x-ray backscattering phenomena. Prototype No. 101

was used for their evaluation.

The data in Table 12 indicates what might occur in a practical field situation,

such as the measurement of lead on a gypsum wallboard or plaster on lath substrate.

If, for example, the measurement is made in a location between the supporting

2 in by 4 in (5.1 cm x 10.2 cm) wood studs, the measurement is likely to be

lower than one made in a location directly in front of such a supporting member.

Table 12 shows that, at lower lead levels, the observed readings with the XK-3

are consistently lower for thinner substrates. The results obtained with the gypsum

wallboard substrate placed on a 3-1/2 in (8.9 cm) thick wood backing (which is

comparable to either gypsum board or plaster on a wood stud) results in measurements

that are essentially satisfactory. Results obtained with the use of gypsum board

reference materials containing 1.83 mg lead/cm z indicate that the thin substrate

effects do not occur at higher lead contents.

instrument No. 101 only was evaluated for sensitivity and adaptability.

32
Table 12 Lead in Paint Measurements on Thick Substrates

Average Measurement (mg lead/cin )

Lead

Content

(mg/ cni ) of Reference

Gypsum

Board

(1/2")

Gypsum Board + 3/8" plywood

Gypsum Board

+ 3-1/2" wood

0 -0.25 -0.05 0.01

0.25 0.14 0.16 0.56

0.70 0.40 0.68 0.75

1.33 0.86 1.21 1.28

1.83 1.86 1.71 1.80

5. 2. 2. 4 Temperature Effects

An operational temperature susceptibility test was conducted in an environmental

chamber at temperatures between 20°F and 140°F (-6.7 °C and 60 °C) in increments

of 10°F (5.5 °C). The XK-3 was stored for 1 hour at each temperature, then removed

from the chamber briefly for testing. The operational characteristics were tested

by determining the lead content of reference materials of known lead content. The

XK-3 was found to be inoperable after storage at 25°F (-4 °C) and lower, and

135°F (57°C) and above but operated normally between 30°F (~1°C) and 130°F (54.5°C).

5.2.3 Field Performance

Periodically, HUD loaned the XK-3 prototypes to agencies conducting surveys of

housing for lead paint. This is presently being done both to field test the

prototypes and to assist agencies in their surveys.

5.2.4 Compliance With The HUD Contract

5. 2. 4.1 Minimum Requirements, Task IIA

The XK-3 prototypes meet the safety and use requirements in general but not the

sensitivity and precision specifications. No. 101 meets the adaptability specification except for multiple paint layers over a paint containing about 0.2 mg lead/cm"

or less. (No. 101 was the only prototype tested for adaptability).

33
5. 2.4.2 Optimum Performance Levels, Task IIB

The XK-3 meets the following requirements:

2 1. Sensitivity (i.e., can detect the presence of lead at levels of 0.1-0. 4 mg/cm

in 9 out of 10 cases with no specific accuracy)

2. Service life

3. Maintenance and Use

4. Temperature

5. Cost per detection and measurement (this was not calculated but the XK-3 should

meet this easily)

6. Sample requirement

7. Portability

8. Speed of analysis

9. Aesthetics

The XK-3 does not met the accuracy and precision requirements.

It does not meet the non-planar surface adaptability requirements, but does meet

those for multi-paint layers over lead paint.

6. DESCRIPTION OF THE ESTABLISHED COMMERCIAL XRF LEAD ANALYZERS

6.1 PRINCETON GAMMA TECH. XK~2

The PGT XK-2 consists of 2 units; a measuring head, and a control module fitted

with a shoulder sling. (See Figure 8).

The measuring head is rectangular and weighs 5.09 lbs (2.31 Kg). Its dimensions

are 3-3/4 in x 9-7/8 in x 5-1/8 in, (9.525 cm x 25.08 cm x 20.32 cm).

The chief components of the measuring head are:

°10 milliCurie cobalt 57 Co K hard X-ray source, having a half life of about

9 months (same source as that of the XK-3).

°a proportional counter tube

°a trigger operated shutter for passage of X-rays

°a "shutter open" indicator light

34
The measuring head is connected to the control module by a power cable

through which the current from the proportional counter passes to be processed in the control module.

Control Module

The control module contains:

“Electronic equipment for processing the current from the proportional

counter including analog and digital circuitry;

“Calibration controls;

“Modular rechargeable battery pack with battery charger;

“Single line lighted digital numerical display;

“Three indicator lights for indicating on/off, measure, and battery

charging modes of the instrument

;

“On/off switch;

“A battery charging cord.

Two standard references are provided with the XK-2 for use in calibrating it

They are both 1/2 in (12.7 mm) thick wooden blocks. One of these is a zero

lead reference while the other, which has a thin lead plate attached to it,

has a precisely known lead content rating of about 75 mg/cm^. They appear

in the foreground of Figure 8.

Operation of PGT XK-2

Firstly, the battery pack must be charged. This requires about 8 hours.

Secondly, the XK-2 must be calibrated. This is relatively easy and can

be done by the operator, by following instruction in the operations manual.

However, it is a fairly lengthy operation and can take as much as 45 minutes

To measure the lead content of a surface, the measurement head is placed

against it and the trigger is squeezed to open the shutter. The trigger is

held open until the result, in mg lead/cra^ appears in the lighted digital

numerical display. This takes 10-30 seconds, depending upon the age of

X-ray source. Figure 9 shows the XK-2 in field use.

6.2 NUCLEAR CHICAGO PB-3

The Nuclear Chicago (NC) PB-3 lead analyzer consists of two units, a hand held probe and a data processor - display unit. (See Figure 10).

35
36
Figure 9 - PGT XK-2 Lead Analyzer in Operation

37
6.2.1

Probe

The probe is cylindrical and has a pistol grip type of handle. It is 9 in (22.8

cm) long, 2-1/2 in (7.35 cm) in diameter and weighs 3 lbs (1.362 Kg). The handle

is 5-1/2 in (13.97 cm) long. The probe's principal components are a Cobalt 57,

Co K hard 2 milliCurie X-ray source, an X-ray detector system, and a shutter

controlled by a trigger recessed in the handle.

6.2.2

Data Processor

The data processor is rectangular and measures 6 in (15.2 cm) x 8 in (20.3

cm) x 4 in (27.9 cm). It weighs 12 lbs (5.45 Kg) and it contains the following

important components:

°analog and digital circuitry to normalize the data from the probe;

“rechargeable battery which is the source of power for both units,

and battery charger;

2 “lighted digital numerical display, showing lead content in mg/cm ;

°an on/off switch;

“battery condition indicator;

“cord for charging the battery;

“detachable carrying harness.

The instrument is provided with an operation manual and reference sample for checking

the calibration. It is calibrated by the manufacturer and must be returned to

him for recalibration. The battery must be charged prior to operation.

6.2.3

Operation

In brief, lead analysis is achieved by placing the probe against the painted surface

and depressing the shutter trigger (see Figure 11). At the end of the analysis

period, an audible signal is sounded and the result in mg/cm^ is displayed in

the data window. The analysis takes 10 to 20 seconds. The manufacturer states

that substrate effects are compensated for the instrument.

38
Figure 10 - Nuclear Chicago PB-3 Lead Analyzer Ready for Use

39

rrmm
Figure 11 - NC, PB-3 in Operation

40
7. COMPARISON OF THE PGT XK-3 PROTOTYPES WITH THE COMMERCIAL LEAD ANALYZERS

7.1 PGT - XK2

7.1.2

Portability

The XK-3 which weighs a total of only 7.1 lbs (3.22 kg) (lead analyzer plus power

pack) is easier to carry in the field than the PGT XK-2 which is very bulky and

weighs 12.7 lbs (5.67 kg). 7.1.3

Calibration

The XK-3 is factory calibrated and, barring damage, needs recalibration only when

the X-ray source is replaced (each 9-12 month period). By contrast the XK-2 needs

recalibration each time it is used. This requires more time than the accuracy

and precision check for the XK-3.

7.1.4

Speed of Analysis

The speed of analysis of the XK-3 prototypes at 35 to 40 seconds is slower than

the XK-2 speed of 10 to 30 seconds. However, a new commercial version of the

XK-3 has just been developed which has an analysis time of 10 to 15 seconds.

7.1.5

Evaluation

In order to perform a measurement, the XK-3 must be held against the test surface

and the handle/trigger mechanism is pressed toward the machine to actuate the trigger

mechanism. A force of about 23-1/2 lbs (10.7 kg) is required to depress the

handle of the instrument and we have found this level of pressure to be quite

fatiguing, especially when making a large number of replicate measurements. By

contrast, the small gun type trigger of the XK-2 requires very little effort to

operate. The XK-3 has a liquid crystal readout system which has permitted a significant weight reduction due to its much lower power requirement. However,

the liquid crystal readout cannot be seen in low light level situations. This

is a serious deficiency in field use since inspections are made quite frequently

in unlit houses.

7.1.6

Accuracy and Precision

The XK-3 prototypes generally exhibited a better accuracy than the XK-2, especially

for the range of 0 to 1.0 mg lead/cm^. However, we have found that XK-2 instrument

C141 has the best accuracy and precision of eleven of these instruments we have

worked with. Therefore, we can state that if the XK-3's are properly calibrated,

they should have better accuracy, consistently, than XK-2's.

The results in Table 13 show that the precision of the XK-3 prototypes is 2 to

3 times as good as that for the XK-2 in the 0.5 mg/cin range (see Table 14).

41
The spreads for the XK-3's were obtained by determining the maximum difference

from the mean for each of the 10 determinations done on each substrate in the

series, and doubling them.

The data in Table 13 further substantiates the above finding that the XK-3's have

better precision than the XK-2. The totals of measurements greater than + 0.2

mg lead/cm^ of the average determinations are all roughly half for each XK-3 than

the total for the XK-2.

Figure 12 shows the XK-2 and XK-3 lead analyzers side by side to illustrate how

much smaller the latter instrument is.

Table 13 Comparison of Precision between PGT XK-2 and XK-3 Prototypes

at the 0.5 mg/cm^ Lead Level

Range from 0.5 for

a single determinaInstrument tion,* mg lead/cm^

Spread

mg/ cm^

XK-2, C141 [ 2] -0.5 to +1.5 2.0

XK-3 No. 101 0 to 1.0 1.0

XK-3 No. 102 0.2 to 0.8 0.6

XK-3 No

103 0.1 to 0.9 0.8

Average of XK-3 spreads o 00

*The determinations selected were those farthest from the mean of 10

determinations

7.2 NUCLEAR CHICAGO PB-2

7.2.1 Portability

The NC PB-3 weighs a total of 15 lbs (6.8 kg), is bulky and like the PGT XK-2

is much more difficult to carry in the field than the PGT XK-3.

42
Figure 12 - PGT XK-2 and XK-3 Lead Analyzers

(Size comparison)

43
7.2.2

Calibration

Like the XK-3, the PB-3 is factory calibrated initially but must be recalibrated

periodically by the operator with a reference sample of known lead content, and

also one of zero lead content.

7.2.3 Speed of Analysis

At its normal speed of 8-10 seconds, it is faster in this respect than the XK-3.

7.2.4 Ease of Operation

It is easier to operate than the XK-2 because of its small gun trigger X-ray shutter

opening system.

7.2.5 Accuracy and Precision

It is not as accurate and precise as either the XK-3 or XK-2.

8. COMMERCIAL VERSION PGT XK-3

The commercial version XK-3 is an improved version of the prototypes. Through the use of an improved preamplifier and other electronic modifications, time required

for analysis in the commercial version was reduced to 10 to 15 seconds from 35

to 40 seconds for the prototypes.

Except for the above improvements, it was found that all other performance

characteristics of the commercial XK-3 were the same as those of the prototypes.

Table 14 shows that the accuracy and precision of the commercial XK-3 are comparable

with those of the best of the prototypes, No. 101.

44
Table

14

Comparison

Between

Lead

Analyzers

for

Accuracy

and

Precision,

at

about

1

mg/cm^

Lead

45

.
Table

14

(Continued)

Comparison

Betweeen

Lead

Analzers

for

Accuracy

and

Precision,

at

about

1

rag/cm

2

Lead
9. CONCLUSIONS

1. The CSI Model 750 lead analyzer is not suitable for field use because it is

inaccurate and imprecise, too difficult for semi-skilled personnel to use and

maintain, and is very bulky and heavy.

2. Although the XK-3 prototypes did not meet all the requirements of the HUD

contract, H-2192R, the XK-3 is a much better field instrument than either the

commercial lead analyzers, namely, the PGT XK-2 and the Nuclear Chicago PB-3 in

these very important respects:

(a) Accuracy

(b) Precision

(c) Portability and operation

Although the XK-3 is a definite improvement over the commercial predecessors, it

has several important deficiencies. The following is a discussion of them.

In order to perform a measurement, the XK-3 must be held against the test surface

and the handle/trigger mechanism pressed toward the machine to actuate the trigger

mechanism. A force of about 23-1/2 lbs (10.7 kg) is required to depress the

handle of the instrument and we have found this level of hand applied pressure

to be quite fatiguing especially when making a larger number of replicate measurements.

The XK-3 has a liquid crystal digital readout system which has permitted a significant weight reduction due to its lower power requirement. However, the

liquid crystal readout cannot be seen in low light situations. This is a serious

deficiency with regard to field operations since inspections are made quite

frequently in unlit houses.

A further disadvantage relates to calibrations. It is, in our opinion, very

unfortunate that the user of the instrument has no means for making simple

calibration adjustments but must send the instrument back to the manufacturer

for that purpose. In fact, the manufacturer recommends that the XK-3's be

recalibrated about every 9 to 12 months, or as often as a new Colbalt 57 source is

required

.

A redesign of the trigger mechanism (which would allow for a lower pressure

effort) would significantly enhance the usability of the instrument.

47
10. ACKNOWLEDGEMENTS

The authors would like to thank Mr. Herbert A. Jackson of the OHBT (CBT)

for his very valuable contributions in performing most of the evaluation

tests, his innovative and constructive suggestions and his help in data

interpretation

The authors would also like to thank Dr. Peter A. Pella, Dr. Dennis H. Brieter, and Dr. K. F. J. Heinrich of the Analytical Chemistry Division for

their technical critiques of the prototype X-ray fluorescent lead detectors

and helpful advice during our evaluation program.

48
11. REFERENCES

1. Rasberry, S.D., Investigation of Portable X-ray Fluorescence Analyzers for

Determining Lead Painted Surfaces; Applied Spectroscopy, Vol 27, No 2, 1973.

2. Spurgeon, Joe C., "Response Characteristics of a Portable X-ray Fluorescence

Lead Detector: Detector of Lead in Paint", National Bureau of Standards Report,

NBSIR 73-231.

49

NBS-1 14A (REV. t 1-77)

U.S. DEPT. OF COMM. BIBLIOGRAPHIC DATA

SHEET

1. PUBLICATION OR REPORT NO. NBSIR 78-1466

2. Gov’t Accession

No.

3. Recipient’s Accession No.

4. TITLE AND SUBTITLE

Evaluation of New Portable X-Ray Fluorescent Lead

Analyzers for Measuring Lead in Paint

5. Publication Date May 1978

6. Performing Organization Code

7. AUTHOR(S)

A. P. Cramp and H. W. Berger

8. Performing Organ. Report No.

9. PERFORMING ORGANIZATION NAME AND ADDRESS

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

10. Project/Task/Work Unit No.

11. Contract/Grant No.

12. Sponsoring Organization Name and Complete Address (Street, City, State, ZIP)

Department of Housing and Urban Development

451 7th Street, S. W. Washington, D. C. 20410

13. Type of Report & Period Covered

14. Sponsoring Agency Code

15. SUPPLEMENTARY NOTES

16. ABSTRACT (A 200-word or less lactual summary of most significant information. If document includes a significant

bibliography or literature survey, mention it here.)

Portable X-Ray fluorescent lead analyzers offer the most cost-effective and adaptable

means for the non-destructive detection and measurement of lead in paint in housing.

However, commercially available portable lead analyzers have had poor accuracy and

precision below lead levels of about 3.0 milligrams of lead per square centimeter

of surface area. This is particularly serious because the current operational

criteria for lead paint hazard abatement, 1.5 or 2.0 mg/cm of lead maximum (used in

many communities) is in this range. They have also performed relatively

unsatisfactorily with regard to serviceability and maintenance. Two new portable

lead analyzers based on x-ray fluorescence have been developed under HUD contracts.

The prototypes of one of these devices have shown considerable improvement over previously available instruments in terms of accuracy, portability, and user characteristics. This report discusses the performance and operating characteristics

of the new lead analyzers.

17. KEY WORDS (six to twelve entries; alphabetical order; capitalize only the first letter of the first key word unless a proper name; separated by semicolons)

Accuracy; calibration; evaluation; lead; paint; poisoning; portable; precision;

rflHlflfirui • rpfprpnrpo* cnKcfrof PC ? ‘v-— uorpcntm ±:

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