NBS SPECIAL PUBLICATION 260-45

QC

100

lASl

H73

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U.S.

EPARTMENT

OF

COMMERCE

National

Bureau

of

Standards

Standard Reference Materials:

DEVELOPMENT OF

NBS STANDARD REFERENCE MATERIAL:

NO. 1579

POWDERED LEAD-BASED PAINT
The National Bureau of Standards1 was established by an act of Congress March 3, 1901. The Bureau's overall goal is to strengthen and advance the Nation's science and

technology and facilitate their effective application for public benefit. To this end, the Bureau conducts research and provides: (1) a basis for the Nation's physical measure- ment system, (2) scientific and technological services for industry and government, (3) a technical basis for equity in trade, and (4) technical services to promote public safety. The Bureau consists of the Institute for Basic Standards, the Institute for Materials Research, the Institute for Applied Technology, the Center for Computer Sciences and

Technology, and the Office for Information Programs.

THE INSTITUTE FOR BASIC STANDARDS provides the central, basis within the United States of a complete and consistent system of physical measurement; coordinates

that system with measurement systems of other nations; and furnishes essential services leading to accurate and uniform physical measurements throughout the Nation's scientific community, industry, and commerce. The Institute consists of a Center for Radiation Research, an Office of Measurement Services and the following divisions: Applied Mathematics — Electricity — Mechanics — Heat — Optical Physics —

Linac Radiation 2 — Nuclear Radiation 2 — Applied Radiation 2 — Quantum

Electronics — Electromagnetics :i — Time and Frequency 3 — Laboratory

Astrophysics •"• — Cryogenics 3

. THE INSTITUTE FOR MATERIALS RESEARCH conducts materials research lead- ing to improved methods of measurement, standards, and data on the properties of

well-characterized materials needed by industry, commerce, educational institutions, and

Government; provides advisory and research services to other Government agencies;

and develops, produces, and distributes standard reference materials. The Institute consists of the Office of Standard Reference Materials and the following divisions: Analytical Chemistry—Polymers—Metallurgy—Inorganic Materials—Reactor

Radiation—Physical Chemistry.

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upon request. The Institute also monitors NBS engineering standards activities and

provides liaison between NBS and national and international engineering standards

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divisions and offices: Engineering and Product Standards—Weights and Measures—Invention and

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THE INSTITUTE FOR COMPUTER SCIENCES AND TECHNOLOGY conducts re- search and provides technical services designed to aid Government agencies in improving cost effectiveness in the conduct of their programs through the selection, acquisition,

and effective utilization of automatic data processing equipment; and serves as the principal focus within the executive branch for the development of Federal standards for automatic data processing equipment, techniques, and computer languages. The Center

consists of the following offices and divisions: Information Processing Standards—Computer Information—Computer Services —Systems Development—Information Processing Technology.

THE OFFICE FOR INFORMATION PROGRAMS promotes optimum dissemination and accessibility of scientific information generated within NBS and other agencies of

the Federal Government; promotes the development of the National Standard Reference Data System and a system of information analysis centers dealing with the broader

aspects of the National Measurement System; provides appropriate services to ensure

that the NBS staff has optimum accessibility to the scientific information of the world,

and directs the public information activities of the Bureau. The Office consists of the following organizational units: Office of Standard Reference Data—Office of Technical Information and

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1 Headquarters and Laboratories at Gaithersburg, Maryland, unless otherwise noted ; mailing address Washington, D.C. 20234.

2 Part of the Center for Radiation Research.

3 Located at Boulder, Colorado 80302.

4 Part of the Center for Building Technology.
National Bureau of Standards APR 2 9 1374

Standard Reference Materials:

Development of

NBS Standard Reference Material No. 1579

Powdered Lead-Based Paint

B. Greifer, E. J. Maienthal

,

T. C. Rains, and S. D.Rasberry

Analytical Chemistry Division

Institute for Materials Research

National Bureau of Standards

Washington, D.C. 20234

U.S. DEPARTMENT OF COMMERCE, Frederick B. Dent, Secretary

NATIONAL BUREAU OF STANDARDS, Richard W. Roberts, Director

Issued March 1973
Library of Congress Catalog Card Number: 73-600016

National Bureau of Standards Special Publication 260-45

Nat. Bur. Stand. (U.S.), Spec. Publ. 260-45, 31 pages (Mar. 1973) CODEN: XNBSAV

For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402.

Price $0.50 domestic postpaid or $0.35 G. P.O. Bookstore.
PREFACE

Standard Reference Materials (SRM's) as defined by the

National Bureau of Standards are "well-characterized materials, produced in quantity, that calibrate a measurement

system to assure compatibility of measurement in the nation."

SRM's are widely used as primary standards in many diverse

fields in science, industry, and technology, both within the

United States and throughout the world. In many industries

traceability of their quality control process to the national

measurement system is carried out through the mechanism and

use of SRM's. For many of the nation's scientists and technologists it is therefore of more than passing interest to

know the details of the measurements made at NBS in arriving

at the certified values of the SRM's produced. An NBS series

of papers, of which this publication is a member, called the

NBS Special Publication - 260 Series is reserved for this

purpose

This 260 Series is dedicated to the dissemination of

information on all phases of the preparation, measurement,

and certification of NBS-SRM's. In general, much more detail will be found in these papers than is generally allowed,

or desirable, in scientific journal articles. This enables

the user to assess the validity and accuracy of the measurement processes employed, to judge the statistical analysis,

and to learn details of techniques and methods utilized for

work entailing the greatest care and accuracy. It is also'

hoped that these papers will provide sufficient additional

information not found on the certificate so that new applications in diverse fields not foreseen at the time the SRM

was originally issued will be sought and found.

Inquiries concerning the technical content of this

paper should be directed to the author(s). Other questions

concerned with the availability, delivery, price, and so

forth will receive prompt attention from:

Office of Standard Reference Materials

National Bureau of Standards

Washington, D.C. 20234

J. Paul Cali, Chief

Office of Standard Reference Materials

iii
CONTENTS

PAGE

I. INTRODUCTION 1

II. OBJECTIVE 2

III. RATIONALE FOR PAINT STANDARD REFERENCE

MATERIAL (SRM) 2

A. Form of SRM 2

B. Desirable Characteristics of SRM 3

C. Choice of SRM Materials 3

IV. COLLECTION AND PREPARATION OF PAINT MATERIAL 5

V. TESTING OF PAINT MATERIAL, 6

VI. ANALYSIS OF PAINT MATERIAL 8

A. Design of Experiment 8

B. Atomic Absorption Spectrometry (AAS) . . . 9

C. Polarography 1Q

D. Calculation of Combined Data 13

VII. MISCELLANEOUS ANALYSES 14

A. Electrolytic Deposition. 15

B. Neutron Activation Analysis 16

VIII. SUMMARY AND CONCLUSIONS 16

IX. RECOMMENDATIONS FOR FUTURE WORK 17

X . REFERENCES 17

APPENDIX A 19

APPENDIX B 20

APPENDIX C 21

iv
LIST OF TABLES

PAGE

Table No .

1. Homogeneity Testing of Powdered Paint by

X-Ray Fluorescence Spectrometry 7

2. Latin Square Design for Analysis of Four

Bottles 65, 233, 376, 444 9

3. Lead Determination by Atomic Absorption

Spectrometry 11

4. Lead Determination by Polarography 12

5. Lead Content of Powdered Paint: Summary

of Results 14

6. Lead Determination by Electrolytic Deposition 15

v
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N

vi
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vii

DEVELOPMENT OF NBS STANDARD REFERENCE MATERIAL: 1579

POWDERED LEAD -BASED PAINT*

Bernard Greifer, E. June Maienthal , Theodore C. Rains,

and Stanley D. Rasberry

Institute for Materials Research

National Bureau of Standards

Washington, D. C. 20234

The development of NBS Standard Reference

Material 1579, Powdered Lead-Base Paint is

described. This SRM is intended for use in

the calibration of apparatus and methods

used in determining lead in paint removed

from old housing.

Paints scraped from the interior surfaces

of old housing were collected, blended, homogenized, and characterized for lead content.

The average lead concentration was found to

be 11.87 percent +0.04 percent lead by weight

determined by atomic absorption spectrometry

and by differential cathode-ray polarography

.

The analytical procedures involved sample

dry ashing in a furnace at 450-550 °C followed

by exhaustive extractions of the insoluble

residue with acids and with ammonium acetate

solution.

Key words: Analytical standard; atomic

absorption spectrometry; differential

cathode-ray polarography; electrodeposition

;

lead-based paint; neutron activation analysis;

x-ray fluorescence spectrometry; Standard

Reference Material.

I. INTRODUCTION

This report describes the development of Standard

Reference Material 1579, Powdered Lead-Based Paint developed

as part of the Lead Paint Poisoning Project by the Analytical

Chemistry Division, Institute for Materials Research. The

Department of Housing and Urban Development, Washington, D.C. 20410

1
material is intended for use in the calibration of apparatus

and methods used in the determination of lead in paint

removed from the interior surfaces of old housing. It is

representative of the types of samples collected in the

field, and its homogeneity and proven lead content of 11.87

percent make it useful for comparing the performance of

different analytical procedures, or for evaluating the

measurements of different laboratories.

II. OBJECTIVE

The objective of this project task was the development

of a standard reference material of known lead content which

would represent the types of paint samples collected in the

field from old housing, and which could provide a calibration

capability to increase the reliability of lead determinations

in dry, aged paint chips and scrapings.

III. RATIONALE FOR PAINT STANDARD REFERENCE

MATERIAL (SRM)

A. Form of SRM

Originally, six types of materials were considered as

possible Standard Reference Materials: (1) dried paint

chips finely ground and sieved, mixed thoroughly to a homogeneous state for general laboratory use; (2) liquid paints

formulated specifically for the desired lead content; (3)

cast films of paint on suitable substrates for subsequent

removal and analysis as free paint films; (4) dry paint

powders such as the electrostatic spray powder paints; (5)

pure pigments diluted to desired lead concentrations; and

(6) painted panels suitably protected from abrasion by

sophisticated packaging, for calibration of portable x-ray

fluorescence instruments used in the field.

2
B. Desirable Characteristics of SRM

The material chosen to be a Standard Reference Material

must be a paint of certified lead content which can be used

to calibrate analytical instruments and techniques in a useful range of lead concentrations. It is desirable that this

material be homogeneous, stable, and representative of samples

taken for analysis. These characteristics are described

quantitatively as follows:

1. Homogeneity: the sample-to-sample variation (i.e.,

bottle-to-bottle, panel-to-panel, etc.) should not

exceed one percent of the total lead content.

2. Stability: the lead content should not change

significantly with storage over a one-year period.

3. Representative of Field Samples: the material

should have the same chemical properties as dried,

aged (40-year old) lead-based paints overlayed with

younger titanium-oxide paints.

4. Calibration Within Useful Range: the SRM should

permit calibration in the expected range of lead

concentrations (i.e., zero to 30 weight percent

2 lead in loose paint chips or zero to 30 mg/cm

lead in paint in situ) , with special consideration

given to calibration near the legally significant

concentrations 1.0 weight percent lead (or 1.0

2 mg/cm lead in situ)

C. Choice of SRM Materials

Freshly prepared paint materials including liquid

paints, cast dried films, and pure pigments differ from

aged paint chips removed from the interior walls of old

housing. For example, the lead-based pigments in fresh

paints are easily soluble in acids or ammonium acetate

solutions and can be analyzed by many methods in the laboratory II] . On the other hand, dried aged paints are less

soluble in acids (including nitric acid + perchloric acid

mixtures) and may give erroneous results due to the diffi3
culty of extracting the lead from the paint matrix. In at

least this one important respect it is clear that freshly

prepared paint standards do not resemble the materials they

are meant to simulate.

Liquid paints are difficult to maintain in a stable

state after the containers are opened. Pigments can be

expected to settle, surface skins form, and volatiles

evaporate over a period of time, causing changes in the

analysis. Dry paint powders of the type used for electrostatic spray painting would be more stable; these could

be doped with lead-based pigment to suitable concentration

levels, and blended to give homogeneous mixtures. However,

no dry powder paints could be found to simulate linseed

oil-based paints. Available materials such as epoxy-based

dry powder paints did not resemble old paint samples sufficiently to be considered as Standard Reference Materials.

2 Painted panels containing zero to 30.0 mg/cm

lead were considered as a Standard Reference Material for

calibration of portable x-ray fluorescence spectrometers

used for field detection of lead on painted walls. However,

the preparation of uniform panels posed considerable

difficulty. After conversations with specialty painting

contractors and painting equipment manufacturers it was

concluded that the required degree of sample -to- sample

uniformity could not be achieved either by paint spraying,

dipping, or draw-down with a film applicator. In addition,

a survey of six principal brands of portable x-ray fluorescence instruments for lead analysis revealed that while

2 they were able to measure zero to 30.0 mg/cm lead concentrations in coatings on walls and woodwork, the measurements

of low lead concentrations were not reliable; the errors were

2

as high as 5 0 percent at the 1.0 mg/cm lead level [2] . If

uniform panels could have been prepared, they would not have

been useful for calibrating portable x-ray fluorescence

2 spectrometers at or below the 1.0 mg/cm lead level. For

these two reasons, consideration of painted panels was deferred.

4
Dried paint chips collected from the old housing had

the desirable properties of stability (already being 30 to

50 years old) ; they were truly representative of material

collected in the field, and they could be made homogeneous

with careful preparation. The paint chips had the disadvantage that their lead content probably was not near the

legally significant 1.0 percent lead by weight. The material

could not be diluted to a lower lead value because any diluent

(e.g. titanium oxide) would have to be added in such a heavy

quantity (e.g. 10 times the weight of paint) that its properties would override the characteristics of the paint. The

best diluent, dried paint chips from housing free of leadbased paint, was not obtainable. Nevertheless, the potential

advantages of using lead-based paint from old housing were

considered to be great enough to warrant accepting the

ambient lead value, knowing that solutions prepared from

the material could be diluted to the desired concentrations

during the course of the chemical analyses

IV. COLLECTION AND PREPARATION OF PAINT MATERIAL

The paint for this standard reference material was

collected by the staff of the Philadelphia, Pennsylvania

Department of Public Health from the interior surfaces of

dwellings undergoing renovation. The paint was softened

with a hand torch and scraped from the plaster and wood

substrates of walls and woodwork, and collected in plastic

bags as a heterogeneous mixture of many different kinds of

paints. In the laboratory, non-paint ingredients such as

metal and plastic objects, glass, and wood shavings were

removed, and the mixture ground in a disk mill to produce

a material suitable for feeding into a jet mill. The paint

was milled in a jet mill operating at 100 psi air pressure,

then it was passed through a 100-mesh vibrating screen to

5
remove the coarse non-grindable fraction, mostly wood

shavings. Two additional passes through the jet mill at 97

to 107 psi gave a powder whose final retention on a 325 mesh

screen was less than 0.69 weight percent. A total of 125

pounds was prepared.

Four hundred and seventy-five bottles , numbered one

through 475 were prepared from one drum of material, loading

from the top down through about 100 pounds of material. The

remaining 25 pounds were reserved for future use.

V. TESTING OF PAINT MATERIAL

Sample homogeneity was investigated by x-ray fluorescence analysis (XRF) for lead content on 17 bottles chosen

at random from the total lot. The bottles were numbered

one through 475 with increasing numbers representing successive layers (slices) from the top to the bottom of the drum

of powdered paint. The random selection chose bottles

numbered 19, 39, 65, 107, 131, 172, 207, 233, 258, 271, 315,

346, 376, 419, 444, 472, and 473.

X-ray fluorescence spectrometry gives very precise results which are ideal for homogeneity testing but it cannot

determine accurately the amount of lead without suitable

calibration. For determining the homogeneity of a material

it is common to accept the readings in uncalibrated arbitrary

units since only the variation of the readings from sample

to sample is of interest.

Two samples from each bottle were poured into spectrocups which were fitted with mylar windows. Each of the 34

samples thus obtained was analyzed four times with a generalpurpose single- channel x-ray fluorescence spectrometer. The

results of the tests in terms of averages of four measurements

are shown in Table 1. The lead content is expressed in a

scale of arbitrary units which has been normalized so as to

give an overall average value of 10.00 units. In this

arbitrary scale the data ranged between 9.95 and 10.05 units.

6
Table 1. Homogeneity Testing of Powdered Paint

by X-Ray Fluorescence Spectrometry

Measured Lead Content3

(arbitrary units)

Bottle

Order

Sample

1

Sample

2

1 10.00b 10.02b

2 10 .00 10 .04

3 9.99 10.04

4 10.04 10.02

5 10.01 10 .00

6 10.02 10.02

7 10.02 10 .00

8 10.02 10 .05

9 10.01 10 .00

10 10.00 10 .02

11 9.99 10.00

12 9.97 9.98

13 9.98 9.97

14 9.98 10 .00

15 9.98 9.98

16 9.96 9.99

17 9.95 9.96

Average: 10.00 units

The analysis measures the lead content in arbitrary units

and shows the bottle-to-bottle variation among 17 randomly

selected samples of dry powdered paint, in descending order

from top to bottom in the bulk material.

Values in this column are averages of 4 measurements

7
A trend may be observed, showing lower values for samples

originating from the lower part of the bulk material container.*

A statistical analysis of the data calculated from all

136 measurements (rather than the 34 averages of four measurements listed in Table 1) lead to the following conclusions:

a) The standard deviation of measurement error (i.e.,

of variability among replicate measurements made on

the same sample) was 0.0 34 unit.*

b) No evidence of heterogeneity of the material within

bottles was detected.

c) A significant amount of bottle-to-bottle variability

was found, as evinced by the trend shown by the

averages in Table 1. However, the magnitude of this

variability was small; expressed as a standard

deviation among bottles it was equal to 0.02 unit.*

The material was considered to be sufficiently homogeneous for use as a Standard Reference Material.

VI. ANALYSIS OF PAINT MATERIAL

A. Design of Experiment

The chemical analysis for lead was carried out on 16

bottles arranged in a four-by-four Latin Square design

experiment in which four samples were taken at random from

each of four randomly selected bottles. The four bottles for

analysis were chosen by a double randomization process from

the series of bottles used for homogeneity testing (the order

of the 17 bottles was randomized and bottles numbered 65, 233,

376, and 444 were chosen at random, from this random listing).

The design of the Latin Square experiment is shown in Table 2.

Subsequent chemical analysis showed the paint to contain

11.87 percent lead by weight. The XRF measurements, converted to percent lead by multiplying by the factor 11.87/10.00,

fall between 11.81 and 11.9 3 percent lead; the standard

deviation of measurement error is 0.0 4 percent lead; and the

bottle-to-bottle variation is 0.02 percent lead.

8
Because of the great variety of paint pigments

expected in the samples, some of them insoluble in acids

(e.g. PbSO^) special care was taken to insure that all the

lead in the material was dissolved completely. As a special

precaution the insoluble residues from both the atomic

absorption spectrometry and the polarographic dissolution

procedures were spot checked by emission spectrographic

analysis to make sure that they did not contain a significant

quantity of lead.

Table 2. Latin Square Design for Analysis of Four

Bottles 65, 233, 376, 44^

Order Bottle Number

Within Analysis Analysis Analysis Analysis

Analysis 1 2 3 4

1 233 376 65 444

2 65 444 233 376

3 376 233 444 65

4 444 65 376 233

B. Atomic Absorption Spectrometry (AAS)

Lead was determined by atomic absorption spectrometry

in duplicate determinations on the 16 bottles , according to

the experimental design shown in Table 2.

1 . Analytical Procedure for AAS

Transfer 0.5 g of sample to a porcelain crucible

and ignite in furnace at 550 °C for 6 hours. Cool and

transfer the test portion to a 250-ml Vycor beaker. Add

10 ml of high-purity HN0

3 [3] and 10 ml of high-purity HC1

[3] and digest for 2 hours, or until the sample volume is

approximately 3 ml. Transfer the sample to a 50-ml centrifuge tube and centrifuge at 2500 rpm for 10 minutes . Decant

the supernatant solution into a 100-ml volumetric flask.

Wash the solids with 15 ml of 1:10 HNO^ and centrifuge at

2500 rpm for 10 minutes. Decant the supernatant solution

into the volumetric flask. Repeat the washings of solids

two additional times. Combine the washings with the sample

9
solution and dilute to the calibrated volume. Determine

lead by atomic absorption spectrometry at a wavelength of

283.3 nm using a slightly fuel-rich acetylene-air flame.

Calibrate the instrument with a series of solutions prepared from lead of high purity (e.g. NBS SRM 49e).

2 . Results of AAS Analyses

The results are shown in Table 3. The average of 32

determinations was 11.84 percent lead by weight. A statistical analysis of the data in accordance with the Latin

Square design led to the following conclusions:

a) The standard deviation of measurement error (exclusive of bottle-to-bottle variability and of systematic run- to-run shifts) was 0.13 percent lead.

b) A small amount of bottle-to-bottle variability was

noted; the standard deviation of variability among

bottles was an additional 0.13 percent lead.

c) A significant but small systematic shift was observed

between the two series of AAS measurements . This

shift, averaged over all determinations, was 0.009

percent lead.

In addition to the 32 analyses reported in Table 3,

four additional lead determinations were carried out on

samples numbered 65, 233, 376, and 444 as a part of Analysis

number 4. These results, reported in Appendix A, were not

a part of the Latin Square experiment and were not included

in the statistical calculations leading to the certified

value for lead.

C . Polarography

Lead was determined by polarographic analysis of 16

samples taken from the same bottles used for AAS analysis.

The samples were analyzed singly according to the same

experimental design, Table 2.

10
Table 3. Lead Determination by Atomic Absorption

Spectrometry

Analysis Number Bottle Number Lead, wt. Percent

Run 1 Run 2

1 233 11.99 12. 12

DO 11 O "3 11 . J

11 on ii . yy

376 11.66 11. 69

444 11.78 11.68

2 376 11. 87 11. 86

A A A -L ± . / D 11 Q 1 233 11.98 12 .07

65 11.93 12 .14

3 65 11. 79 11.96

233 11.76 11. 93

444 11.64 11. 70

376 11.70 11.65

4 444 11.57 11. 80

376 11.80 12.13

65 11.78 11.74

233 11.93 11.98

Average of 32 determinations: 11.84% lead by weight

1 . Analytical Procedure for Polarography [4]

Shake the bottle for one minute, then weigh 100

milligram portions into a Vycor crucible and ignite for

2 hours at 450 °C. Treat the ash with 2 ml high purity

HC1 [3] , 5 ml high purity HNO^ [3] , and 5 drops high purity

HF [3] and evaporate to dryness. Add 5 ml HNO^ and evaporate

to dryness. Evaporate to dryness twice more with the

addition of 2 ml HC1 each time. Treat the solids with 30

ml of acetic acid - ammonium acetate solution (100 ml acetic

acid + 95 ml NH^OH + 100 ml 1^0) , cover, and heat for several

hours just below boiling. Decant the supernatant solution

into a 400-ml beaker. Add 25 ml more of the acetic acid - ammonium acetate solution to the solids in the crucible

and heat again just below boiling. Combine all the crucible

contents with the original solution, rinsing the crucible

well with water. Heat the combined solution just below

11
boiling for about one hour, cool, and transfer quantitatively

to a 200-ml volumetric flask. Dilute to calibrated volume.

Transfer a 5.0 ml portion to a polarographic cell,

deaerate, and measure the lead reduction peak at about -0.7

volts against a mercury pool anode, with a differential

cathode ray polarograph against a blank in the second cell

which has been carried through the entire procedure. Standard

solutions prepared from melting point lead (NBS SRM 49d) are

carried through the procedure to establish a calibration

curve

.

2 . Results of Polarographic Analyses

The results are shown in Table 4. The average of

16 determinations was 11.9 3 percent lead by weight. The

"standard deviation of measurement error, exclusive of possible

bottle-to-bottle variability, was calculated to be 0.13

percent lead.

No bottle-to-bottle variation in lead content was

detected by polarography

.

Table 4. Lead Determination by Polarography

Analysis Bottle Lead

Number Number Wt. Percent

1 233 11.91

65 11.99

376 12.08

444 11.93

2 376 12.00

444 11.83

233 11.74

65 11.99

3 65 11.98

233 11.65

444 11.99

376 12.02

4 444 12.02

376 11.68

65 12.00

233 12.05

Average of 16 determinations: 11.93% lead by weight

12
In addition to the 16 analyses reported in Table 4, four

additional lead determinations were carried out on sample

number 65 before the beginning of the Latin Square experiment.

These results, reported in Appendix B, were not included in

the statistical calculations leading to the certified value

for lead.

D . Calculation of Combined Data

The results of 32 AAS and 16 polarographic analyses are

summarized in Table 5. The difference between the AAS results

(11.84 percent lead) and the polarographic results (11.9 3

percent lead) was determined to be on the borderline of

significance by a t-test calculation (t = 2.26), using

the estimates of the standard deviations of measurement error

obtained from the two Latin Square experiments

The average value, weighted for 32 AAS determinations

and 16 polarographic determinations was 11.87 percent lead

by weight. The standard error of the weighted average was

0.02 percent, hence the approximate 9 5 percent confidence

interval for the average was + 0.04 percent lead by weight.

The average value of lead for the entire lot was taken

to be

11.87 percent + 0.04 percent lead by weight.

13
Table 5. Lead Content of Powdered Paint:

Summary of Results 3

Bottle

Number

65

233

376

444

, Weight Percent Lead , AAS POL

32 Determinations 16 Determinations

11. 88

11.97

11.80

11.73

11.99

11. 84

11.94

11.94

Average

Standard deviation

for an individual a measurement : c

11.84

= 0.13% lead

11.93

a = 0.13% lead

Standard error of

averages

t test:

= 0.023% lead = 0.032% lead

t = 2.26

Weighted average value:

Standard error of

weighted average : Approximate 95 percent

confidence interval :

11.87% lead

0.02% lead

11.87 + 0.04% lead

These are the results of 48 lead determinations carried

out according to the experimental design shown in Table 2.

The results of 56 lead determinations are summarized in

Appendix C.

Sample averages calculated from data in Tables 3 and 4. cEstimates of standard deviations of measurement error

obtained from Latin Square experiments.

VII. MISCELLANEOUS ANALYSES

The powdered lead-based paint was analyzed by electrolytic deposition and by neutron activation analysis as a

further check on the lead content.

14
A. Electrolytic Deposition

Follow the AAS dissolution procedure to the point where

the solution is ready to be measured. Take 25 ml aliquots

of this solution and evaporate to dryness with HNO^, twice,

to destroy the HC1. Dissolve the solid residue in 3 percent

HN0

3 (10 ml HN0

3 + 325 ml H

2 0) and electrolyze with platinum

electrodes at 0.4 ampere for at least 5 hours , or for overnight if more convenient. After electrolysis remove the

platinum anode, dry for one hour at 135 °C, cool and weigh.

The weight increase is calculated as PbC^*

The results are summarized in Table 6. The average

value of lead in 3 bottles was 11.9 2 percent by weight.

Table 6. Lead Determination by Electrolytic Deposition

Lead, Weight Percent

Bottle

Number

5-Hour

Electrolysis

Overnight

Electrolysis

233

376

444

12.13

11.69

11.93

12.06

11. 83

11. 86

Average of all results: 11.9 2% lead by weight

0.40 ampere, platinum electrodes.

15
B . Neutron Activation Analysis

Neutron activation analysis was carried out on 4 samples

taken from the bulk material remaining after bottling. The

204 204m procedure that was used employed the Pb (n,n') Pb

reaction. Four samples, 1.6 g each and four standards,

reagent grade lead acetate were irradiated for 2 hours with

252

a 600-microgram Californium source. The gamma ray

doublet of 2Q4mPb (half -life 6 7 minutes) at 0.91 MeV was

counted for 100 minutes using a 60 ml Ge(Li) detector.

The results for 4 samples were: 10.7, 10.6, 11.7 and

11.4 percent lead by weight. The average value was 11.1

percent lead.

VIII. SUMMARY AND CONCLUSIONS

The development of Standard Reference Material 1579,

Powdered Lead-Based Paint is described. This SRM is intended

for use in calibration of apparatus and methods used in

determing lead in paint from old housing. The certificate

issued with the material is reproduced in Appendix c. Paints scraped from the interior surfaces of houses undergoing renovation have been collected, blended, homogenized,

and characterized for lead content. The average lead concentration is 11.87 percent + 0.0 4 percent lead by weight,

as analyzed by atomic absorption spectrometry and polarography and corroborated by electrolytic deposition and by neutron

activation analysis.

The uncertainty expressed in the above result is the

half -width of the 95 percent confidence interval, based on

a total of 48 measurements. Analysis by x-ray fluorescence

spectrometry showed the homogeneity of the material with

respect to lead to be within the certification limits.

16
This material is considered to be more representative

of old, dried-out, intractable paints collected in the

field than freshly prepared paint formulations containing

precisely measured amounts of lead as a single pigment

or a mixture of pigments. Two recommended sample dissolution

procedures involve dry ashing in a furnace at 450 to 550 °C

followed by digestion of the ash with HCl-HNO^ mixtures, and

exhaustive extraction of the insoluble residue with either

dilute HNO^ (AAS analysis) or with HC1 and with ammonium

acetate solutions (polarographic analysis).

IX. RECOMMENDATIONS FOR FUTURE WORK

The powdered lead-based paint may contain traces of

toxic heavy metals other than lead. Some metals of concern

which should be investigated in future work are antimony,

arsenic, cadmium, mercury, selenium, and soluble barium.

The search for a suitable diluent, in the form of dried,

old, lead-free paint chips should be continued with the

thought of blending the as-received lead based paint to a

lower lead concentration in the 1.0 percent or the 0.06

percent range. This could increase the SRM's value to the

analytical chemist.

The search for a procedure to prepare uniform standard

reference painted panels should be continued, against the

time when portable x-ray fluorescence spectrometers may be

improved to where they can be calibrated at the 0.06 to

2 1.0 mg/cm lead level.

X . REFERENCES

[1] Welcher, F. J., Editor, Scott's Standard Methods of

Chemical Analysis , Sixth Edition, IIB, pp. 1680-1719,

D. Van Nostrand, New York, (1963).

[2] Rasberry, S. D. , personal communication

17
[3] Kuehner, E. C. , Alvarez, R. , Paulsen, P. J. , and Murphy,

T. J., High-Purity Acids Purified by Sub-Boiling Distillation, Anal. Chem. 44, (12), 2050-2056 (1972).

[4] Maienthal, E. J., Polarographic Analysis, in Electrochemical Analysis Section Summary of Activities , July

1970 - June 1971, R. A. Durst, Editor, U.S. National

Bureau of Standards Technical Note 583, U. S. Government Printing Office, Washington, D. C. 20234 (1972).

Sample Collection was handled by Mr. Edward Wiener, Assistant Chief, Accident Control Section, Department of Public

Health, City of Philadelphia, 500 South Broad Street,

Philadelphia, Pa. 19146.

Sample Grinding was carried out by Frank and James Albus

,

Alnort, Inc., 2430 Broadway, Camden, N. J. 08104.

Homogeneity determination was carried out by X-ray Fluorescence: S. D. Rasberry, Analytical Chemistry Division.

Analyses for lead were carried out by the following methods:

Atomic Absorption Spectrometry: T. C. Rains and T. A. Rush,

Analytical Chemistry Division.

Polarography : E. J. Maienthal, Analytical Chemistry Division.

Electrolytic Deposition: R. K. Bell, Analytical Chemistry

Division

.

Neutron Activation: G. J. Lutz , Analytical Chemistry

Division

.

Statistical calculations were carried out by J. Mandel,

Institute for Materials Research.

18
APPENDIX A.

LEAD DETERMINATION BY ATOMIC ABSORPTION SPECTROMETRY:

Results of 36 determinations

Analysis Number Bottle Number Lead, Wt. Percent

Run 1 Run 2 Run 3

233 11.99 12.12

65 11.83 11.89

376 11 . 66 11. 69

AAA 1 1 7ft X X . D O

376 11.87 11. 87

444 11.76 11.91

233 11.98 12.07

D O 11 Q "3 ii.y j

1 O 1/1

65 11.79 11.96

233 11.76 11.93

444 11.64 11.70

376 11.70 11.65

444 11.57 11.80 11.53

376 11.80 12.13 11.74

65 11.78 11.74 11.66

233 11.93 11.98 11.77

Average of 36 determinations: 11.83% lead by weight

Results of 4 extra measurements , not a part of the Latin

Square experiment, and not included in the statistical

calculations leading to the certified value for lead.

19
APPENDIX B. LEAD DETERMINATION BY POLAROGRAPHY

Results of 20 determinations

Analysis Number Bottle Number Lead, Wt. Percent

65 12 04a

65 12 09 a

65 11 95 a

65 11.98a

1 233 11 91

65 11 99

376 1l • UO

444 11.93

2 37fi 19 no 444 1 t: *i 11

9^ J-1 J-T . 74/ 4

65 11.99

•? •J 11 9 8

233 11 fi R 444 "T "1 "3 11 99

376 12.02

A lift 1l. 1 9 D9uz 376 11.68

65 12.00

233 12.05

Average of 20 determinations

11.95% lead by weight

Results of 4 extra measurements, not a part of the Latin

Square experiment, and not included in the statistical

calculations leading to the certified value for lead.

20
U. S. Departi Petertlto/of Commerce APPENDIX C

(33seterson TM

Rational ^Bureau of ji»tandartb

(Certificate of JVnalgsts

Standard Reference Material 1579

Powdered Lead Based Paint

This Standard Reference Material is intended for use

in the calibration of apparatus and methods used in the

determination of lead in paint removed from the interior

surfaces of old housing. The certified value is based on

at least a 100 milligram sample of the as -received, total

material

The certified value of 11.87% lead is the weighted

average value determined by a statistical analvsis of the

results of 32 determinations by atomic absorption spectrometry

(average 11.84% lead, s = 0.13% lead), and 16 determinations

by polarography (average 11.9 3% lead, s = 0.13% lead). The

standard error of the weighted average is 0.02% lead, and

the half -width of the 9 5% confidence interval is taken to

include ± 0.0 4% lead by weight.

X-ray fluorescence spectrometry showed the bottle-tobottle inhomogenei ty of the material with respect to lead

content to be no greater than 0.0 2% lead; no within -bottle

inhomogenei ty was detected.

Analyses for lead and determinations of homogeneity

were carried out in the NBS Analytical Chemistry Division

by the following persons:

X-Ray Fluorescence: S. D. Rasberry

Atomic Absorption Spectrometry: T. C. Rains and T. A. Rush

Polarography: E. J. Mai en thai

Statistical calculations were carried out by J. Mandel

of the NBS Institute for Materials Research.

The overall direction and coordination of the technical

measurements leading to this certificate were performed under

the chairmanship of B. GreiferThe technical and support aspects involved in the

preparation, certification, and issuance of this Standard

Reference Material were coordinated through the Office of

Standard Reference Materials by T. W. Mears

Washington, D.C. 20234 J. Paul Cali , Chief

September 29, 1972 Office of Standard Reference Materials

Lead Content 11.87 ± 0.0 4 Weight Percent

(over)

21
Preparation, Testing, and Analysis

Collection

The paint for this Standard Reference Material was collected by the staff of the Philadelphia Department of

Public Health from the interior surfaces of dwellings

undergoing renovation. The paint was softened with a hand

torch, scraped from the plaster and wood substrates, and

collected in plastic bags as a heterogeneous mixture of

many different kinds of paints. In the laboratory, non-paint

matter such as bits of metal, plastic, glass, and wood were

removed and the paint mixture was ground in a disk mill

to produce a material suitable for feeding into a jet mill.

The paint was comminuted in a jet mill operating at 100 psig

air pressure, then sieved through a 100-mesh vibrating

screen to remove the coarse, non-grindable fraction. Two

additional passes through the jet mill at 97 to 107 psig gave

a fine powder with 99.31 weight percent passing through a 325 mesh sieve.

Homogeneity

Sample homogeneity was ascertained by x-ray fluorescence

analysis for lead content on 1 7 samples chosen at random

from the total lot. A statistical analysis of the data from

136 observations showed the bottle-to-bottle variability

among the samples to be no greater than 0.02% lead. No

wi thin-bottle variation with respect to lead was detected.

Dissolution

A procedure used to dissolve the sample is summarized

briefly: dry ash the weighed paint for 2 hours at 450 °C,

digest with 2:5 HCI-HNO3 containing HF, evaporate to dryness;

treat with HNO3 , evaporate to dryness; treat twice with HC1

and evaporate to dryness each time. Extract the solids

twice with portions of acetic acid - ammonium acetate solution,

heating for several hours just below boiling. Combine the

extracts and heat the mixture (including solids) for one hour,

just below boiling. Cool the mixture and determine lead in

solution. (The solids need not be removed for polarographic

analysis .

)

An alternate procedure for sample dissolution is: dry

ash the weighed paint for 6 hours at 500 °C, cool, then digest

for 2 hours in 1:1 HCl-HNO^. Separate the insoluble solids

from the solution by centri f uging , and wash 3 times with

1:10 HNO3 combining the rinsings with the principal solution.

Determine lead in solution.

Details of the dissolution procedures, the analytical

procedures, and results will be published in the 260 series

of NBS Special Publications.

<r U. S. GOVERNMENT PRINTING OFFICE :1973—511-324 (197)
Iform NBS-114A (i-7i) U.S. DEPT. OF COMM. 1. PUBLICATION OR REPORT NO. 2. Gov't Accession

BIBLIOGRAPHIC DATA |\jB$ SP 260-45 N°' SH E E T

3. Recipient's Accession No.

4. title and subtitle standard Reference Materials:

Development of NBS Standard Reference Material No. 1579

rOWUcrcU LcaU-DdocU raiiit

5. Publication Date March 1973

6. Performing Organization Code

7. AUTHOR(S)

B. Greifer, E. J. Maienthal, T. C. Rains, & S. D. Rasberry

8. Performing Organization

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 Address Department of Housing and Urban Development

WasHnpton D C 2 0410

13. Type of Report & Period Covered

Final

14, Sponsoring Agency Code

15. SUPPLEMENTARY NOTES

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

bibliography or literature survey, mention it here.)

The development of NBS Standard Reference Material No. 1579, Powdered Lead-Based Paint

is described. This SRM is intended for use in the calibration of apparatus and methods

used in determining lead in paint removed from old housing.

Paints scraped from the interior surfaces of old housing were collected, blended,

homogenized, and characterized for lead content. The average lead content was found

to be 11.87% + 0.04% lead by weight determined by atomic absorption spectrometry and

by differential cathode ray polarography.

The analytical procedures involved sample dissolution by dry ashing in a furnace at

450-550 °C followed by exhaustive extractions of the insoluble residue with acids

and with ammonium acetate solution.

17. key words (Alphabetical order, separated by semicolons) Analytical standard; atomic absorption spectrometry; differential cathode ray polarography; electrodeposition; lead-based paint;

neutron activation analysis; x-ray fluorescence spectrometry; Standard Reference Material

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