Interim Method for the Determination of Asbestos in Bulk Insulation Samples

-------

-------
TECHNICAL REPORT DATA
l^lcayt rtad Instructiuiit -vi ?hr r\.'*rnc bcfort
1. REPORT NO.
EPA-600/4-82-020
ORD -!eport
fCIPISNT'S ACCtSSION NO.
13364
4. TITLE AND SUBTITLE
INTERIM METHOD FOR THE DETERMINATION OF ASSLSTOS IN
BULK INSULATION SAMPLES
REPORT DATE
March 1982
«. PERFORMING ORGANIZATION CODE
43U-2069-74
8. PERFORMING ORGANIZATION REPORT NO
D.E. Lentzen, E.P. Brandy, Jr., K.U. Cold, and
L.E. Myers
9 PERFORMING ORGANIZATION NAME AND ADDRESS
Research Triangle Institute
P.O. Box 12194
Research Triangle Park, N.C. 27709
1O. PROGRAM ELEMENT NO.
11. CONTFtACtVdRANt NO.
EPA Contract 68-02-3431
12. SPONSORING AGENCY NAME AND AODRf SS
Environmental Monitoring Systems Laboratory
Research Triangle Park, NC 27711
Office of. Pesticides and Toxic Substances
Washington, D.C. 20460
13. TYPE Of REPORT AND PERIOD CO VI RED
Final, January-August, 1981
14. SPONSORING AGENCY CODE
EPA/600/0&
IS.
NOTES
16. ABSTRACT
The U. S. Environmental Protection Agency Asbestos-in-Schools Program was estab-
lished in March, 1979 to provide information and technical assistance to the public
for addressing problems presented by asbestos-containing insulation materials in
school buildings. Because there were no existing standard procedures for the quali-
tative and quantitative analysis of asbestos in bulk materials, the Office of Pesti-
cides and Toxic Substances, Washington, D.C., and the Environmental Monitoring
Systems Laboratory, Research Triangle Park, NC, Jointly sponsored an effort to
produce a standard analytical protocol. This report presents ir.formatlon on the
development and characterization of the standard procedures for analysis cf bulk
sanples with polarized light microscopy (PLM) and X-Ray diffraction (XRD), and
includes the Interim Method for the Determination of Asbestos in Bulk Insulation
Samples, (October, 1981). *.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.IDENTIFIERS/OPEN ENDED TERMS c. COSATI I ickVCroup
is. DISTRIBUTION STATEMENT

Release to Public
19. SECURITY CLASS iTtlil Krponj
Unclassified
21. NO OF PAGES
52
J20. SECURITY CLASS iTttlt pafff
Unclassified
22. PRICE
£PA F»»m 2720-1 (••*. 4-77) •wcviout COITIOK ••otifOicrc

-------
                      NOTICE

This document has been reviewed in accordance with
U.S. Environmental Protection Agency policy and
approved for publication.  Mention of trade names
or commercial products does not constitute endorse-
ment or recommendation for use.
                       ii

-------
FOREWORD

Measurement and monitoring research efforts are designed to anticipate
potential environmental problems, to support regulatory actions by develop-
ing an in-depth understanding of the nature and processes that impacc health
and the ecology, to provide innovative means of monitoring compliance with
regulations, and to evaluate the effectiveness of health ?.nd environmental
protection efforts through the monitoring of long-term trends. The Environ-
mental Monitoring Systems Laboratory, Research Triangle Park, North Caro-
lina, has responsibility for: assessment of environmental monitoring tech-
nology and systems; implementation of agency-wide quality assurance pro-
grams for air pollution measurement systems; and supplying technical support
to other groups in the Agency including the Office of A1r, Noise, and Radia-
tion, tha Office of Pesticides and Toxic Substances, and the Office of
Enforcement.
This report describes the development of
-------
ABSTRACT
The U.S. Environmental Protection Agency Asbestos-in-Schools Program
was established in March 1979 to provide information and technical assistance
to the public for addressing problems presented by asbestos-containing
insulation materials in school buildings. Because there WP^ no existing
standard procedures for the qualitative and quantitative analysis of asbestos
in bulk materials, the Office of Pesticides and Toxic Substances, Washington,
D.C., and the Environmental Monitoring Systems Laboratory, Research Triangle
Park, NC, jointly sponsored an effcrt to produce a standard analytical
protocol. This reoort presents information on the development and charac-
terization of the standard procedures, and includes the Interim Method for
the Determination of Asbestos in Bulk Insulation Samples. (October 1981).
This report is submitted in fulfillment of Contract No. 68-02-3431 by
Research Triangle Institute under the sponsorship of the l>.S. Environmental
Protection Agency. This report covers the period January 1, 1981, to
August 31, 1981, and work was completed as of October 15, 1981.
1v
-------
CONTENTS
Page
Foreword i i i
Abstract iv
Acknowledgment vi
1 Introduction 1
2 Summary 2
3 Development of the Interim Method 3
4 Overview of the Interim fiethod 5
4.1 Polarized Light Microscpy 5
4.2 X-Ray Powder Diffraction . . '. 6
References . 9
Appendix
Interim Method for the Determination of Asbestos in
Bulk Insulation Samples (October 1981) 10
-------
ACKNOWLEDGMENT

This method is based in part on contributions and review comments of
participants in the symposium "Methods Definition for the Polarized Light
Microscope and X-Ray Diffraction Analysis of Bulk Samples for Asbestos,"
U.S. Bureau of Mines, Avondale Research Center, Avondale, Maryland, October
23-24, 1979.
-------
SECTION 1
INTRODUCTION

In March 1979, the Environmental Protection Agency (EPA) established
the Asbestos-in-Schools Program to provide information and technical assist-
ance to the public for addressing the problems presented by asbestos-contain-
ing materials in school buildings (School Asbestos Program, 44 FR 54676).
Technical information concerning the identification and control of potential
exposures to asbestos fibers released from friable insulation materials is
available to states and local school districts. Information and assistance
are available through several channels, including EPA-designated Regional
Asbestos Coordinators, toll-free telephone numbers maintained by the Research
Triangle Institute and the EPA Office of Pesticides and Toxic Substances
(OPTS) Industry Assistance Office, and several guidance documents and pro-
gram reports published by EPA.1 2 3
Because there were no existing standard procedures for the analysis of
asbestos in bulk materials, the Office of Pesticides and Toxic Substances,
Washington, D.C., and the Environmental Monitoring Systems Laboratory, Research
Triangle Park, NC, jointly sponsored an effort to produce a practical and
objective analytical protocol. The Interim Method for the Determination
of Asbestos in Bulk Insulation Samples has been developed by the Research
Triangle Institute, on contract to EMSL and OPTS. The Interim Method
includes procedures for qualitative and quantitative analysis of bulk
samples by polarized light microscopy (PLM) and X-ray powder diffraction
(XRD). Limited characterization of the method has been obtained in an
interlaboratory study, the results of which nay be found in the EPA report
Bulk Sample Analysis for Asbestos Content: Evaluation of the Tentative
Method (October 1981). Revisions to the original draft of the method
based on the results of the evaluation testing have been incorporated into
this document. Further testing is anticipated; therefore, the appended
procedures are presented as an Interim Method and are subject to revision.
-------
SECTION 2
SUMMARY

An Interim Method has been developed for the determination of asbestos
in bulk samples by polarized light microscopy (PLtf) and X-ray powder diffrac-
tion (XRO). EPA sponsored development of the method as part of its As-
bestos- in- Schools Program.
Initial drafts of the method were based on information presented in a
symposium attended by representatives of public, private, and university
laboratories involved in the analysis of asbestos. Following review of the
draft by symposium attendees, an interlaboratory study was conducted to
collect data for the preliminary characterization of the method. Revisions
to the method were made pursuant to results of the study.
The Interim Method for the Determination of Asbestos in Bulk Insulation
Samples (October 1981) includes protocols for the qualitative and quanti-
tative analysis of bulk samples by PLM and XRD, and is appended to this
report.
-------
SECTION 3
DEVELOPMENT OF THE INTERIM METHOD

The Environmental Protection Agency recommended the use of polarized
light microscopy (PLM) and X-ray powder diffraction (XRD) for the analysis
of bulk samples in its initial guidance document1 for the Asbestos-in-
Schools Program. PLM was recommended as the primary analytical technique,
to be supplemented by XRD as necessary. Part I of the guidance document
included guidelines for PLM and XRD analysis, but noted the lack of a
standard protocol for bulk sample analysis. OPTS and EMSL asked the Research
Triangle Institute to develop a standard protocol for the qualitative and
quantitative analysis of asbestos in bulk samples.
The task was initiated by reviewing existing literature and conferring
with persons knowledgeable in techniques of mineral analysis. This initial
survey supported the finding that PLM and XRD were currently the most appro-
priate methods for use in the asbestos abatement program.
A symposium was organized for the discussion of techniques for sample
preparation and qualitative and quantitative analysis by PLM and XRD.
Representatives of the Federal government and analysts fron; pt'blic, private,
and university laboratories attended the symposium "Methods Definition for
the Polarized Light Microscope and X-Ray Diffraction Analysis of Bui1'.
Samples for Asbestos" held at the U.S. Bureau of Mines, Avondaie Research
Center, Avondaie, Maryland, October 23-24, 1979. Information presented at
the symposium was used in the preparation of an initial draft of the method.
The draft protocols were distributed to symposium participants ?.nrt
other interested parties for reviow. Revisions were made to the drafts
based on comments received in two rouncs of review, resulting *ri the
Tentative Method for the Detsrmlnation of Asbestifortp Minerals in Sulk
Insulation Samples (March 1980).
An interlaboratory study was conducted for the evaluation of the
Tentative Method. Results of the study are reported in the EPA report
-------
3ulk Sample Analysis for Asbestos Content: Evaluation of the Tentative
Method (October 1981). Results of trie interlaboratory study and comments
received from participate locoratories have been used to further revise
the protocols. Because d:-;a collected in the evaluation study indicate the
need for additional testing, the protocols have been designated an Interim
Method and are subject to revision. The Interim Method for the Detennination
of Asbestos in Bulk Insulation Samples (October 1981) is appended hereto.
-------
SECTION 4
OVERVIEW OF THE INTERIM METHOD

4.1 POLARIZED LIGHT MICROSCOPY
The PLM protocol specifies the use of classical petrographic techniques
:or the identification of asbestos fibers. Subsaipples of bulk materials are
prepared by appropriate techniques, immersed in an oil of known refractive
index, and examined with a light microscope using both single and crossed
polarizing filters. Asbestos fibers are positively identified by the obser-
vation of six optical properties: morphology, color and pleochroism, refrac-
tive indices (or dispersion staining colons), birefringence, extinction
characteristics, and sign of elongation.
There are several deterrents to the reliable quantisation of asbestos
in bulk samples by PLM, including the variability of interferences and
matrices, the small amount of sample examined, and variation in the
optical properties of asbestos minerals. Additionally, it is somewhat
difficult to apply the results of analysis by optical microscopy to the
current Federal regulations. In April 1973, EPA banned the spray appli-
cation of insulation products containing more than 1 percent asbestos by
weight (38 FR 8820). PLM methods measure tne relative area occupied by
asbestos fiber and matrix material within the microscope fields of view.
The relationship between the percent asbestos of a sample on a weight basis
and the percent asbestos by area as determined by PLM analysis cannot be
reliably characterized for bulk samples in general.
Quantisation is performed in the PLM procedure by a point counting
technique. Point sampling is used in variou? fields of study to determine
the relative area within specified boundaries occupied by a particular
subject (type of rock, soil, plant, etc.). Point counting is used in
petrography to determine relative areas of minerals in thin sections of
rock. The technique assumes that particles within the field of view are of
-------
equal thickness and are randomly oriented with respect to the microscope
light path.4 Testing has indicated that despite the violation of these
assumptions, point counting may be applied to the quantisation of asbestos
in bulk samples with less between-laboratory variability than the more
subjective estimation techniques currently in use.
Information that allows preliminary characterization of the PLM protocol
was obtained in an interlaboratory study.5 Samples analyzed in the study
consisted of a single type of asbestos, either chrysotile cr amosire, in a
relatively simple matrix consisting primarily of gypsura. The results of
quantitative analysis using the point counting procedure were more accurate
than those produced by other methods of PLM quantisation. This was particu-
larly true when PLM results were assumed to be a direct measure of the
amount of asbestos present (i.a., ignoring the problem of relating PLM area
percent results with the known weight percent values). Under the same assump-
tion, data produced by point counting and that produced by other methods
were similarly precise.
The relationship between the reported PLM data and the known values was
investigated with linear regression in natural logarithmic coordinates. The
principle sources of variance in the area-weight relationship were differences
among laboratories and differences between Asbestos types (chrysotile and
amosite). When variance due to these sources was removed, the residual
error of point counting data was less than that of data by other quantisation
procedures.
Sources of between-laboratory variance include differences in sample
preparation procedures, subsampling techniques, application of the point
counting procedure, quality of optical instruments, and level of training
and expertise of the analyst. Research is in progress on ways in which the
application of PLM procedures may be further standardized and the accuracy
of PLM data improved.
4.2 X-RAY POWDER DIFFRACTION
The XRO protocol specifies procedures for both the qualitative and
quantitative analysis of asbestos in bulk materials. Since XRD affords
information only on crystal lattice structure and not on gross crystal
-------
morphology, this technique cannot distinguish between the asbestos minerals
and their nonasbestiform varieties. Particle morphologies must be determined
by an optical technique such as PLM. Therefore, it is recommended that the
XRO method be used as a corroborative procedure with PLM and not as an inde-
pendent analytical method.
Qualitative analysis of bulk materials by XRO is performed with a
minimum of matrix reduction. Samples are initially scanned over limited
diagnostic peak regions for the serpentine and amphibole minerals, using
standard slow-scanning methods for bulk sample analysis. All samples that
exhibit diffraction peaks in the diagnostic peak regions for asbest;form
minerals are submitted to a full qualitative XRO scan. Sample constituents
are identified by comparison of the sample diffraction pattern with standard
reference powder diffraction patterns.6 When subsequent quantisation is
required, particular note is made of possible interferences.
The thin-layer procedure for quantisation of asbestos in bulk samples
by XRO is a modification of the NIOSH-recoaanended method for the analysis of
chrysotile in air samples.7 This procedure involves initial comminution of
the bulk material to approximately 10 urn by cryogenic milling techniques and
deposition of an accurately known amount of the sample on a silver membrane
filter. The mass of asbestos minerals is determined by measuring the inte-
grated area of the selected diagnostic peak, correcting for matrix absorption
effects, and comparing with suitable external standards. Although there is
ample evidence that this method is capable of measuring microgram quantities
of asbestos in relatively simple systems with reasonable accuracy, precision,
and speed,8 its reliability for quantitative analysis of asbestos minerals in
bulk samples has not been fully characterized.
Analytical problems and limitations of the method are clearly identified
in the protocol. These include problems of sample preparation, particle
size and preferred orientat-fon effects, matrix interference and absorption
effects, intraspecies interference by nonasbestos varieties of the asbestos
minerals, and problems associated with assuring that reference standards are
comparable to samples in chemical composition, particle size distribution, and
crystallinity.
A relatively snail number of laboratories provided XRO data in the
interlaboratory study. None of the laboratories that participated in the
-------
study followed the XRD protocol exactly. Some laboratories uued semiquanti-
tative thick-layer or bulk methods and ottiers used variations of the thin-
layer method. Because of the small number of laboratories that reported XRD
results, and the nonequivalence of the methods employed for quantisation, it
was not possible to draw any firm conclusions about tha accuracy and preci-
sion of the XRD protocol. However, the results of the study did indicate
that the bulk methods of analysis were at least as precise and accurate as
the more rigorous thin-layer methods as applied by participating laboratories.
Recent reports in the literature have also indicated that bulk methods
of analysis may provide reliable quantitative analysis of asbestos at low
concentrations in a variety of matrices.9 10 Since XRD analysis for asbestos
by bulk methods would be much less difficult and costly than thin-layer
methods, further research is being directed toward comparing these methods
and assessing their potential for satisfying current EPA requirements. At
this time, it appears that semi quantitative bulk methods of analysis for
asbestos may be acceptable as an alternative to the thin-layer method of
analysis detailed in the XRD protocol.
8
-------
REFERENCES

1. U.S. Environmental Protection Agency, Asbestos-Containing Materials
in School Buildings: A Guidance Document. Parts 1 and 2, EPA/OTS
No. C00090, March 1979.

2. D. Lucas, T. Hartwell, arid A. V. Rao, Asbestos-Containing Materials
in..^rfo?0J-BU:^]ngs: Guidance for Asbestos Analytical Programs,
EPA 560/13-80-017A, U.S. Environmental Protection Agency, December
1980, S6 pp.

3. E. P. Brantly, Jr., and D. E. Lentzen, Asbestos-Containing Materials
i-.^S-99J-^"J^Jn9s.: _ Bulk Sample Analysis Quality Assurance Program,
EPA 56J/13-80-23, U.S. Environmental Protection Agency, August 1980,
27 pp.

4. F. Chayes, Petrographic Modal Analysis: An Elementary Statistical
Appraisal, New York:John Wiley & Sens, 1956, 133 pp.

5. E. P. Brantly, Jr., K. W. Gold, L. E. Myers, and 0. E. Lentzen,
Bulk Sample Analysis for Asbestos Content: Evaluation of the
Tentative Method, U.S. Environmental Protection Agency, October
T95T

6. JCPDS-International Center for Diffraction Data Povder Diffraction
File, U.S. Department of Commerce, National Bureau of Standards,
IndJoint Committee on Powder Diffraction Studies, Swarthmore,
Pennsylvania.

7. NIOSH Manual of Analytical Methods, Volume 5, U.S. Department of
Health, Education and Welfare, August 1979, pp. 30S-1 to 309-9.

8. B. A. Lange and J. C. Haartz, Determination of microgram quantities of
asbestos by X-ray diffraction: Chrysotile in thin dust layers of
matrix material.'Anal. Chem., 51(4):520-525, 1979.

9. H. Dunn and J. H. Stewart, Jr., Quantitative determination of
Chrysotile in building materials, The Microscope, 29(1):39-45, 1981.

10. M. Taylor, Methods for quantitative determination of asbestos and
quartz in bulk samples using X-ray diffraction, The Analyst,
103(1231):1009-1020, 1978.
-------
APPENDIX
INTERIM METHOD FOR THE DETERMINATION OF ASBESTOS
IN BULK INSl'LATION SAMPLES
10
-------
INTERIM METHOD FOR THE UFTEf-MINATION OF ASBESTOS
IN BULK INSULATION SAMPLES
An interim method is carefully drafted from available source
information. This method is still under investigation and
therefore is subject to revision.
Prepared for

Office of Pesticides and Environmental Monitoring
Toxic Substances Systems Laboratory
U.S. Environmental Protection U.S. Environmental Protection
Agency Agency
Washington, DC Research Triangle Park, NC
20460 27711
October 1981
11
-------
SECTION 1
POLARIZED LIGHT MICROSCOPY

1.1 PRINCIPLE AND APPLICABILITY
Bulk samples of building materials taken for asbestos identification are
first examined for homogeneity and preliminary fiber identification at low
magnification. Positive identification Q* suspect fibers is made by analysis
of subsamples with the polarized light microscope.
The principles of optical mineralogy are well established.1 2 A light
microscope equipped with two polarizing filter» is used to observe specific
optical characteristics of a sample. The use of plane polarized light allows
the determination of refractive indices along specific crystallographic axes.
Morphology and color are also observed. A retardation plate is placed in the
polarized light path for determination of the sign of elongation using ortho-
scopic illumination. Orientation of the two filters such that their vibration
planes are perpendicular (crossed polars) allows observation of the birefring-
ence and extinction charsctaristies of anisotropic particles.
Quantitative analysis involves the use of point counting. Point counting
is a standard technique in petrography for determining the relative areas
occupied by separate urinerals in thin sections of rock. Background information
on the use of point counting2 and the interpretation of point count data3 is
available.
This method is applicable to all bulk samples of friable insulation
materials submitted for identification and quantisation of asbestos components.
1.2 RANGE
The point counting method may be used for analysis of samples containing
from 0 to 100 percent asbestos. The upper detection limit is 100 percent.
The lower detection limit is less than 1 percent.
12
-------
1.3 INTFRFERENCES
Fibrous organic and inorganic constituents of bulk samples may interfere
with the identification and quantisation of the asbestos mineral content.
Spray-on binder materials may coat fibers and affect color or obscure optical
characteristics to the extent of masking fiber identity. Fine particles of
other materials mey also adhere to fibers to an extent sufficient to cause
confusion in identification. Procedures that may be used for the removal of
interferences are presented in Section 1.7.2.2.
1.4. PRECISION AND ACCURACY
Adequate data for measuring the accuracy and precision of the method for
samples with various matrices are not currently available. Data obtained for
samples containing a single asbestos type in a simple matrix are available in
the EPA rapcrt Bulk Sample Analysis for Asbestos Content: Evaluation of the
Tentative Method.4
1.5 APPARATUS
1.5.1 Sample Analysis
A low-power binocular microscope, preferably stereoscopic, is used to
examine the bulk insulation sample as received.
Microscope: binocular, 10-45X (approximate).
Light Source: incandescent or fluorescent.
Forceps. Dissecting Needles, and Probes
Glassine Paper or Clean Glass Plate
Compound microscope requirements: A polarized light microscope complete
with polarizer, analyzer, port for wave retardation plata, 360° graduated
rotating stags, substage condenser, lamp, and lamp iris.
Polarized Light Microscope: described above.
Objective Lenses: 10X, 20X, and 40X or near equivalent.
Dispersion Staining Objective Lens (optional)
Ocular Lens: 10X minimum.
Eyepiece Reticle: cross hair or 25 point Chalkley Point Array.
Compensator Plate: 550 millimicron retardation.
13
-------
1.5.2 Sample Preparation
Sample preparation apparatus requirements will depend upon the type of
insulation sample under consideration. Various physical and/or chemical means
may be employed for an adequate sampla assessment.
Venf.1at.ed Hood or negative pressure glove box.
Microscope Slides
Covers lips
Mortar and Pestle: agate or porcelain, (optional)
Wylia Mill (optional)
Beakers and Assorted Glassware (optional)
Cent"ifuge (optional)
Filtration apparatus (optional)
Low temperature asher (optional)
1.6 REAGENTS
1.6.1 Sample Preparation
Distilled Water (optional)
Dilute CHaCOOH: ACS reagent grade (optional)
Dilute HC1: ACS reagent grade (optional)
Sodium metaphosphate (NaP03)8 (optional)
1.6.2 Analytical Reagents
Refractive Index Liquids: 1.490-1.570, 1.590-1.720 in increments of
0.002 or 0.004.
Refractive Index Liquids for Dispersion Staining: high-dispersion
series, 1.550, 1.605, 1.630 (optional).
UICC Asbestos Reference Sample Set: Available from: UICC MRC
Pueumoconiosis Unit, Llandough Hospital, Penarth, Glamorgan CF6 1XW,
UK, and commercial distributors.
Tremolite-asbestos (source to be determined)
Actinolite-asbestos (source to be determined)
1.7 PROCEDURES
NOTE: EXPOSURE TO AIRBORNE ASBESTOS FIBERS IS A HEALTH HAZARD. BULK
.SAMPLES SUBMITTED FOR ANALYSIS ARE USUALLY FRIABLE AND MAY RELEASE FIBERS
DURING HANDLING OR MATRIX REDUCTION STEPS. ALL SAMPLE AND SLIDE PREPARATIONS
14
-------
SHOULD 3E CARRIED OUT IN A VENTILATED HOOD OR GLOVE BOX WITH CONTINUOUS AIRFLOW
(NEGATIVE PRESSURE). HANDLING OF SAMPLES WITHOUT THESE PRECAUTIONS MAY RESULT
IN EXPOSURE OF THE ANALYST AND CONTAMINATION OF SAMPLES BY AIRBORNE FIBERS.
1.7.1 Sampling
Samples for analysis of asbestos content shall be taken in the manner
prescribed in Reference 5 and information on design of sampling and analysis
programs may be found in Reference 6. If there are any questions about the
representative nature of the sample, another sample should be requested before
proceeding with the analysis.
1.7.2 Analysis
1.7.2.1 Grass Examination—
Bulk samples of building materials taken for the identification and
quantisation of asbestos are first examined for homogeneity at low magnifica-
tion with the aid of a stereomicroscope. The core sample may be examined in
its container or carefully removed from the container onto a glassins transfer
paper or clean glass plate. If possible, note is made of the top and bottom
orientation. When discrete strata are identified, each is treated as a sepa-
rate material so that fibers are first identified and quantified in that layer
only, and then the results for each layer are combined to yield an estimate of
asbestos content for the whole sample.
1.7.2.2 Sample Preparation-
Bulk materials submitted for asbestos analysis involve a wide variety of
matrix materials. Representative subsamples may not be readily obtainable by
simple means in heterogeneous materials, and various steps may be required to
alleviate the difficulties encountered. In most cases, however, the best
preparation is made by using forceps to sample at several places from the bulk
material. Forcep samples are immersed in a refractive index liquid on a
microscope slide, teased apart, covered with a cover glass, and observed with
the polarized lighx microscope.
Alternatively, attempts may be made to homogenize the sample or eliminate
interferences before further characterization. The selection of appropriate
procedures is dependent upon the samples encountered and personal preference.
The following are presented as possible sample preparation steps.
15
-------
A mortar and pestle can sometimes be used in the size reduction of soft or
loosely bound materials though this may cause matting of some samples. Such
samples may be reduced in a Wylie mill. Apparatus should be clean and extreme
care exercised to avoid cross-contansination of samples. Periodic checks of
the particle sizes should be made during the grinding operation so as to
preserve any fiber bundles present in an identifiable form. These procedures
are not recommended for samples that contain amphibole minerals or veranculite.
Grinding of araphiboles may result in the separation of fiber bundles or the
production of cleavage fragments with aspect ratios greater than 3:1. Grinding
of vermiculite may also produce fragments with aspect ratios greater than 3:1.
Acid treatment may occasionally be required to eliminate interferences.
Calcium carbonate, gypsum, and bassanite (plaster) are frequently present in
sprayed or trowelled insulations. These materials may be removed by treatment
with warm dilute acetic acid. Warm dilute hydrochloric acid may also be used
to remove the above materials. If acid treatment is required, wash the sample
at least twice with distilled water, being careful not to lose the particulates
during decanting steps. Centrifugation or filtration of the suspension will
prevent significant fiber loss. The pore size of the filter should be 0.45 mi-
cron or less. Caution: prolonged acid contact with the sample may alter the
optical characteristics of chrysotile fibers and should be avoided.
Coatings and binding materials sunering to fiber surfaces may also be
removed by treatment nth sodium metaphosphate.7 Idd 10 ml of 10 g/L sodium
metaphosphate solution to a small (0.1 to 0.5 ml) sample of bulk material in a
15-mL glass centrifuge ti'^e. For approximately 15 seconds each, stir the
mixture on a vortex mixer, place in an ultrasonic bath and then shake by hand.
Repeat the series. Collect the dispersed solids by centrifugation at 1000 rpm
for 5 minutes. Wash the sample three times by suspending in 10 ml distilled
water and recentrifuging. After washing, resuspend tne pellet in 5 mL dis-
tilled water, place a drop of the suspension on a microscope slide, and dry
the slide at 110° C.
In samples with a large portion of cellulosic or other organic fibers, it
may be useful to ash part of the sample and view the residue. Ashing should
be performed in a low temperature asher. Asln'ng may also be performed in a
muffle furnace at temperatures of 500° C or lower. Temperatures cf F.jO° C or
higher will cause dehydroxylation of the asbestos minerals, resulting in changes

16
-------
of the refractive index and other key parameters. If a muffle furnace is to
be used, the furnace thermostat should be checked and calibrated to ensure
that samples will not be heated at temperatures greater than 550° C.
Ashing and acid treatment of samples should net be usc-d as starcJard
procedures. In order to monitor possible changes in fiber charaoceristics,
the material should be viewed sricroscopically before and afte;- any s*i.iple
preparation procedure. Use of these procedures on sample': to be used fcr
qu.ir'.itation requires a correction for percent weight loss.
1.7.2.3 Fiber Identification--
Positive identification of asbestos reqiri-es the determination of the
following optical properties.
Morphology
Color and pleochroism
RefractiV3 indices
Birefringence
Extinction characteristics
Sign of elongation
Table 1-1 lists the above properties for commercial asbestos fibers. Figure 1-1
presents a flow diagram of the examination procedure. Natural variations in
the conditions under which deposits of asbestiform minerals are formed will
occasionally produce exceptions tc the published values and difference; from
the UICC standards. The sign of elongation is determined by use of tiie com-
pensator plate and crossed polars. Refractive indices may be determined by
the Becke line test. Alternatively, dispersion staining may be used. Inexperi-
enced operators may find that the dispersion staining technique is more easily
letrned, and should consult Reference 9 for guidance. Central stop dispersion
staining colors are presented in Table 1-2. Available high-dispersion (HO)
liquids should be used.
1.7.2.4 Quantisation of Asbestos Content--
Asbestos qiHntitation is performed by a paint-counting procedure. An
ocular reticle (cross-hair or point array) is u«sd to visually superimpose a
point or points on the microscope field of view. Record the number of points
positioned dirtctly above each kind of particle or fiber of interest. Score
only points directly over asbestos fibers or nonasbestos matrix material. Do
17
-------
TABLE 1-1. OPTICAL PROPERTIES OF ASBESTOS FIBERS
00
Mineral
Chrysolde
(asbestlfora
serpentine)

Aaostte
(asbeslifor*
grunerlte)

doc! do lite
(as best (fora
rleteckite)

Anthopi.yUile-
asbosto*

Iremvllte-
actinglite-
asbestos

Morphology,
color
Wavy fibers. Fiber bundles
have splayed ends and "kinks".
Aspect ratio typically >10:1.
Colorless , nonpleocltrolc.
Straight, rigid fibers.
Aspect ratio typically >10:1.
Colorless to brown, nonpleo-
chrolc or weakly so. Opaque
inclusions may be present.
Straight, rigid fibers.
Thick fibers and bundles coa-
mon, blue to purple-blue in
color. Pleochroic. Bire-
fringence is generally Masked
by blue color.
Straight fibers and.acicular
cleavage fragments. Some
composite fibers. Aspect
ratio <10:1. Colorless to
light brown.
Normally present as acicu'ar
or prismatic cleavage frag-
ments . Single crystals pre-
dominate, aspect ratio <10:1.
Colorless to pale green.

Refractive indices
« »
1.493-1.560 1 517-1
(normal ly

1.635-1.696 1.655-1
birefringence
.562* .008
1.556)

.729f .020-. 033
(normally
1.696-1

1.654-1.701 1.668-1
(norma
close to

1.596-1.652 1.615-1

1.599-1.668 1.622-1

.710)

.71?" .014-. 016
My
1.700)

.676f .019-. 024

.68af .023-. 020

Extinction
|tG fiber
length

Ito fiber
length

|to fiber
length

Ito fiber
length

Oblique
extinction,
10-20° for
frayoents.
Composite
fibers ihow 1
exl'nction.
Sign of
elongation
«
( length slow)

4
(length slow)

-
(Icngtl. fast)

+
(length slow)

«
(length slow)

*Fro» reference 5; colors cited are seen by observation with
plane polarited light.
Froa references 5 and 8.
""Fibers subjected to heating may be brownish.
Fibers defined as having aspect ratio >3:1.
' HP fiber length.

'I to fiber length.
-------
Poleriied light microscopy analysis: For each type of material identified by examination of sample at low magnification.
Mount specially dispersed sample in 1.550 Rl liquid. (If using dispersion staining, mount in 1.550 HO.) View at 100X
with both plane polarized light and crossed pdars. More than one fiber type may be present.
Fihm
•I

•dditiamJ prepttttf iMti it IOOX and 450X

Fifcifj pnMm fa,,,, rt,.,.!
I
» » E«>.nin «< *• tttn in iwjuro^c (inkikh Report no abmtoi
Mftri il (tiff ntitio* wttk traoW litiutiM .-.' *0* uttrvdi if prtunt
»«Un) ittei riUtiM j
1
1 -II um Mihra «bMtir.
Rl tytiu*v < I M
iMd: I7M urn Htmitu, 1. DtttrmiM ixtiKtJM ckMKtwirtkt.
k«lk*4a Mdt M< AM. I. OitirniM (%u •( tfeiititkii.
I
^ ^ k!i«iM in 1.709 Rl liUM 1
0«lsf«to»« 1
Ck«k •.rpfcoliw Mo.m hi I.MS Rl H,.d.
DitmabM «.
Cluck m»ifk»t»f^ vtt
ckjractiriAki tat MlkipkytlrH,
tranoNti-ieti^olin.
Figure 1-1. Flow chart for analysis of bulk samples by polarized light microscopy.
-------
TABLE 1-2. CENTRAL STOP DISPERSION STAINING COLORS*
Mineral
Chrysotile
Amosite
Crocidolite
Anthophyllite
Tremolite
Actinolite
RI Liquid
1. 550HO
1.680
1. 550HD
1.700
1. 550HO
1.605HD
1.605H°C
1.605HO
1. 630HO
n i
Blue
Blue-magenta to
pale blue
Yel low to white
Red n.agenta
Ycl low to white
Blue
Pale blue
Gold-magenta
to blue
Magenta
n ii
Blue-magenta
Golden-yel low
Yellow to white
Blue-magenta
Yellow to white
Gold to
gold-magenta
Yellow
Gold
Golden-yel low
From reference 9.
Blue absorption color.
Oblique extinction view.
20
-------
not score empty points for the cli '.-t particle. If an asbestos fiber and a
matrix pa:'ticle overlap so that a foint is superimposed on their visual inter-
section, a point is scored for both categories. Point counting provides a
determination of the area percent asbestoo. Reliable conversion of area
percent to percent of dry weight is not currently feasible unless the specific
gravities and relative volumes of the materials are known.
For the purpose of tr.is method, "asbestos fibers" are defined as having
an aspect ratio greater than 3:1 and being positively identified as one of the
minerals in Table 1-1.
A total of 400 points superimposed on either asbestos fibers or nonasbes-
tos matrix material must be counted over at least eight different preparations
of representative subsamples. Take eight forcep samples and mount each separ-
ately with the appropriate refractive index liquid. The preparation should
not be heavily loaded. The sample should be uniformly dispersed to avoid
overlapping particles and allow 25-50 percent empty area within the fields of
view. Court 50 nonempty points on each preparation, using either
A cross-hair reticle and mechanical stage; or
A reticle with 25 points (Chalkley Point Array) and counting at
least 2 randomly selected fields.
For samples with mixtures of isotropic and anisotropic materials present,
viewing the sample with slightly uncrossed polars or the addition of the
compensator plate to ths polarized light path will allow simultaneous discrim-
ination of both particle types. Quantisation should be performed at 100X or
at the lowest magnification of the polarized light microscope that can effec-
tively distinguish the sample components. Confirmation of the quantitation
result by a second analyst on some percentage of analyzed samples should be
used as standard quality control procedure.
The percent asbestos is calculated as follows:
% asbestos = (a/n) 100%

where
a = number of asbestos counts,
n = number of nonempty points counted (400).
21
-------
If a = 0, report "No asbestos detected." If 0 < a < 3, report "

asbestos".

The value reported should be rounded to the nearest percent.

1.8 REFERENCES

1. Paul F. Kerr, Optical Mineralogy. 4th ed., New York, McGraw-Hill, 1977.

2. E. M. Chamot and C. W. Mason, Handbook of Chemical Microscopy, Volume One,
3rd ed., New York: John Wiley & Sons, 1958.

3. F. Chayes, Petrographic Modal Analysis: An Elementary Statistical
Appraisal, New York:John Wiley & Sons, 1956.

4. E. P. Brantly, Jr., K. W. Gold, L. E. Myers, and D. E. Lentzen, Bulk
Sample Analysis for Asbestos Content: Evaluation of the Tentative Method,
U.S. Environmental Protection Agency, October 1981.
U.S. Environmental Protection Agency, Asbestos-Containing Materials in
School Buildings: A Guidance Document, Parts 1 and 2, fcPA/UIS No. CUU090,
5.

March 1979.
6. D. Lucas, T. Hartwell, and A. V. Rao, Asbestos-Containing Materials in
School Buildings: Guidance for Asbestos Analytical Programs, EPA SBW13-
80-017A, U.S. Environmental Protection Agency, December 1980, 96 pp.

7. D. H. Taylor and J. S. Bloom, Hexametaphosphate pretreatment of insula-
tion samples for identification of fibrous constituents, Microscope, 28,
1980. ~

8. W. J. Campbell, R. L Blake, L. L. Brown, E. E. Gather, and J. J. Sjoberg.
Selected Silicate Minerals and Their Asbestiform Varieties: Mineralogical
Definitions and Identification-Characterization, U.S. Bureau of Mines
Information Circular 8751, 1977.

9. Walter C. McCrone, Asbestos Particle Atlas. Ann Arbor: Ann Arbor Science
Publishers, June 198TT
22
-------
SECTION 2
X-RAY POWDER DIFFRACTION

2.1 PRINCIPLE AND APPLICABILITY
The principle of X-ray powder diffraction (XRD) analysis is well estab-
lished.1 2 Any solid, crystalline material will diffract an impingent beam of
parallel, monochromatic X-rays whenever Bragg1s Law,
X = 2d sin 6,
is satisfied for a particular set of planes in the crystal lattice,
where
o
\ = the X-ray wavelength, A;
d = the interplanar spacings of the set of reflecting lattice planes,
O
A; and
9 = the angle of incidence between the X-ray beam and the reflecting
lattice planes.
By appropriate orientation of a sample relative to the incident X-ray beam, a
diffraction pattern can be generated that, in most cases, will be uniquely
characteristic of both the chemical composition and structure of the crystal-
line phases present.
Unlike optical methods of analysis, however, XRD cannot determine crystal
morphology. Therefore, in asbestos analysis, XRD does not distinguish between
fibrous and nonfibrous forms of the serpentine and amphibole minerals (Table 2-1).
However, when used in conjunction with optical methods such as polarized light
microscopy (PLM), XRD techniques can provide a reliable analytical method for
the identification and characterization of asbestiform minerals in bulk materials.
For qualitative analysis by XR'J methods, sajsples are initially scanned
O
over limited diagnostic peak regions for the serpentine (-7.4 A) and amphibole
O
(8.2-8.5 A) minerals (Table 2-2). Standard slow-scanning methods for bulk
sample analysis may be used for materials shovn oy PLM to contain significant
amounts of asbestos (>5-10 percent). Detection of minor or trace amounts of
23
-------
TABLE 2-1. THE ASBESTOS MINERALS AND THEIR
NONASBESTIFORM ANALOGS
Asbestiform Nonasbestifonn '

SERPENTINE

Chrysotile Antigorite, lizardite

AHPHI80LE

AnthophylHte asbestos Antfiophyl lite
Cujnn)ingtonite-gn;nerite asbestos CuDmingtom'te-grunen'te
("Amosite")
Crocidolite Riebeckite
Tremolite asbestos Treraolite
Actinolite asbestos Actinolite
24
-------
TABLE 2-2. PRINCIPAL LATTICE SPACINGS OF AS8ESTIFORM MINERALS4
Minerals
Principal d-ipacings (A)
and relative intensities
JCPDS
Powder diffraction file3
number
Chrysotile
"Amosite"
Anthophyl 1 ite
Actinolite
Croc idol ite
Tremolite
7.37100
7. 36100
7.10100
£•. 33100
8.2210o
3.05100
3.06100
2.72100
8.35l0o
2.706100
3.5570
3. OOgo
2.3380
3.0670
3.0608S
3.2460
8. 3370
2.54100
3.1055
3.12100
3.1495
2. 70660
4.57SO
2.456S
3.5570
2.75670
3.2570
8.2655
3.2350
3.4080
2.72035
2. 70590
8.4340
8.4440
21-543b
25-645
22-1162 (theoretical)
17-745 (nonfibrous)
27-1170 (UICC)
9-455
16-401 (synthetic)
25-157
27-1415 (UICC)
13-437b.
20-1310° (synthetic)
23-666 (synthetic
mixture with
richterite)
This information is intended as a guide, only. Complete powder diffraction
data, including mineral type and source, should be referred to, to ensure
comparability of sample and reference materials where possible. Additional
precision XRD data on amosite, crocidolite, tremolite, and chrysotile are
available from the U.S. Sureau of Mines.4

Fibrosity questionable.
25
-------
asbestos may require special sample preparation and step-scanning analysis.
All samples that exhibit diffraction peaks in the diagnostic regions for
aobestiform minerals are submitted to a full (5°-60° 26; 1° 28/min) qualita-
tive XRD scan, and their diffraction patterns are compared with standard refer-
ence powder diffraction patterns3 to vcvify initial peak assignments and to
identify possible matrix interferences when subsequent quantitative analysis
will be performed.
Accurate quantitative analysis of asbestos in bulk samples by XRD is
critically dependent on particle size distribution, crystallite size, preferred
orientation and ip^trix absorption effects, and comparability of standard
reference an«^ sample materials. The most intense diffraction peak that has
been shown to be free from interference by prior qualitative XRD analysis is
selected for quantisation cf each asoestiform mineral. A "thin-layer" method
of analysis* 6 is recommended in which, subsequent to comminuticp of the bulk
material to ~1C urn by suitable cryogenic milling techniques, an accurately
known amount of the sample is deposited on a silver membrane filter. The mass
of asbestiform material is determined by measuring the integrated area of the
selected diffraction peak using a step-scanning mode, correcting for matrix
absorption effects, and comparing with suitable calibration standards. Alter-
native "thick-layer" or bulk methods,7 8 may be used for semi quantitative
analysis.
This XRD method is applicable as a confirmatory method for identification
and quantitation of asbestos in bulk material samples that have undergone prior
analysis by PLM or other optical methods.
2.2 RANGE AND SENSITIVITY
The range of the method has not been determined.
The sensitivity of the method has not been determined. It will be vari-
able and dependent upon many factors, including matrix effects (absorption and
interferences), diagnostic reflections selected, and their relative intensities.
2.3 LIMITATIONS
2.3.1 Interferences
Since the fibrous and nonfibrous forms of the serpentine and amphibole
minerals (Table 2-1) are indistinguishable by XRD techniques unless special
26
-------
sample preparation techniques and instrumentation are used,9 the presence of
nonasbestiform serpentines and amphiboles in a sample will pose severe inter-
f«rence problems in the identification and quantitative analysis of their
asbestiform analogs.
The use of XRD for ia«ntification and quantisation of asbestiform minerals
in tulk samples may also be limited by the presence of other interfering
materials in the sample. For naturally occurring materials the commonly
associated asbestos-related mineral interferences can usually be anticipated.
However, for fabricated materials the nature of the interferences may vary
greatly (Table 2-3) and present more serious problems in identification and
quantitation.10 Potential interferences are summarized in Table 2-4 and
include the following:
o o
Chlorite has major peaks at 7.19 A and 3.58 A that interfere with
o o
both the primary (7.36 A) and secondary (3.66 A) peaks for chrysotile.
Resolution of the primary peak to give good quantitative results may
be possible when a step-scanning mode of operation is employed.
o
HalToysite has a peak at 3.63 A that interferes with the secondary
'J
(3.66 A) peak for chrysotile.
O
Kaolim'te has a major peak at 7.15 A that may intfirfere with the
~~—~"~~~~ o
primary peak of chrysotile at 7.36 A when present at concentrations
of >10 percent. However, the secondary chrysoti"ie peak at 3.66 A
may be used for quantitation.
o o
Gypsum has a major peak at 7.5 A that overlaps the 7.36 A peak of
chrysotile when present as a major sample constituent. This may be
removed by careful washing with distilled water, or by heatir.g to
300° C to convert gypsum to plaster of paris.
Cellulose has a broad peak that partially overlaps the secondary
(3.65 A) chrysotile peak.8
Overlap of major diagnostic peaks of the amphibole asbestos minerals,
amosite, anthophyllite, crocidolite, and tremolite, at approximately
o o
8.3 A and 3.1 A causes mutual interference when these minerals occur
in the presence of one another. In some instances, adequate resolu-
tion may be attained by using step-scanning methods and/cr by decreas-
ing the collimator slit width at the X-ray port.
27
-------
TABLE 2-3. COMMON CONSTITUENTS IN INSULATION AND
WALL MATERIALS10
A. Insulation materials

Chrysotile
"Amosite"
Crocidolite
*Rcc:k wool
*Slag wool
*Fiber glass
Gypsum (CaS04 • 2H20)
Vertniculite (micas)
*Perlite
Clays (kaolin)
*Vood pulp
*Paper fibers (talc, clay, carbonate fillers)
Calcium silicates (synthetic)
Opaques (chromite, magnetite inclusions in serpentine)
Hematite (inclusions in "amosite")
Magnesite
*0iatomaceous earth

B. Spray finishes or paints

Bassanite
Carbonate minerals (calci'te, dolomite, vaterite)
Talc
Tremolite
Anthophyllite
Serpentine (including chrysotile)
Amosite
Crocidolite
*Mineral wool
*Rock wool
*Slag wool
*Fiber glass
Clays (kaolin)
Micas
Chlorite
Gypsurs (CaS04 • 2H20)
Quartz
"Organic binders and thickener*?
Hydromagnesite
Wollastonite
Opaques (chromite, magnetite inclusions in serpentine)
Hematite (inclusions in "amosite")

^Amorphous materials—contribute only to overall scattered radiation and
increased background radiation.
28
-------
TABLE 2-4. INTERFERENCES IN XRO ANALYSIS
OF ASBESTIFORM MINERALS
Asoestiform
mineral
Pr-imary diagnostic
peaks (approximate
o
d-spacings, in A)
Interferer.ee
serpentine
Chrysotile
7.4
Amphibole
"Amosite"
Anthop/iyllite
C roc iV.o lite
Tremoh'ts
3.7
3.1
8.3
Nonasbestiform serpen-
tines (antigorite,
lizardite)
Chlorite
Kaolinite *
Gypsum

Chlorite
Halloysite
Cellulose
Nonasbestiform amphiboles
(cummingtonite-grunerite,
anthophyllite, riebeckite,
tremolite)
Mutual interferences
Carbonates
Talc

Mutual interferences
29
-------
Carbonates may alsa interfere with quantitative analysis of the amphi-
bole asbestos minerals, amosite, anthophy?lite, crocidolite, and tremo-
o
lite. Calcium carbonate (CaC03) has a peak at 3.035 A that overlaps
o
major amphibole peaks at approximately 3.1 A when present in concen-
trations of >5 percent. Removal of carbonates with a dilute acid
wash is possible; however, if present, cnrysotile may be partially
dissolved by this treatment.11
o
A major talc peak at 3.12 A interferes with the primary tremolite peak
o
at this same position and with secondary peaks of crocidolite (3.10 A),
o o
amosite (3.06 A), and anthopnyllite (3.05 A). In the presence of talc,
o
the major diagnostic peak at approximately 8.3 A should be used for
quantisation of these asbestiform minerals.
The problem of intraspecies and matrix interferences is further aggravated
by the variability of the silicate mineral powder diffraction patterns them-
selves, which often makes definitive identification of the asbestos minerals
by comparison with standard reference diffraction patterns difficult. This
variability results from alterations in the crystal lattice associated with
differences in isomcruhous substitution and degree of crystal! *'nity. This is
especially true for t.(e amphiboles. These minerals exhibit a wide variety of
very similar chemical compositions, with the result being that their diffrac-
tion patterns are characterized by having major (110) reflections of the mono-
clinic amphiboles and (210) reflections of the orthorhombic anthophyllite
o
separated by less than 0.2 A.12
2.3.2 Matrix Effects
If a copper X-ray source is used, the presence of iron at high concentra-
tions in a sample will result in significant X-ray fluorescence, leading to*
loss of peak intensity along with increased background intensity and an overall
decrease in sensitivity. This situation may be corrected by choosing an X-ray
source other than copper; however, this is often accompanied both by loss of
•intensity and by decreased resolution of closely spaced reflections. Alterna-
tively, use of a diffracted beam monochromator will reduce background fluorescent
radiation, enabling weaker diffraction peaks to be detected.
30
-------
X-ray absorption by the sample matrix will result in overall attenuation
of the diffracted beam and may seriously interfere with quantitative analysis.
Absorption effects may be minimized by using sufficiently "thin" samples for
analysis.5 13 14 However, unless absorption effects are knosn to be the same
for both samples and standards, appropriate corrections should be made by
referencing diagnostic peak areas to an internal standard7 8 or filter sub-
strate (Ag) peak.5 6
2.3.3 Particle Size Dependence
Because the intensity of diffracted X-radiation is particle-size dependent,
it is essential for accurate quantitative analysis that both sample and stand-
ard reference materials have similar particle size distributions. The optimum
particle size range for quantitative analysis of asbestos by XRD has bean re-
ported to be 1 to 10 urn.15 Comparability of sample and standard reference
material particle size distributions should be verified by optical microscopy
(or another suitable met.nod) prior to analysis.
2.3.4 Preferred Orientation Effects
Preferred orientation of asbestiform uiinerals during sample preparation
often poses a serious problem in quantitative analysis by XRD. A nurrber of
techniques have heen developed for reducing preferred orientation effects in
"thick layer" san.ples.7 8 1S However, for "thin" samples on membrane filters,
the preferred orientation effects seem to be both reproducible and favorable
to enhancement of the principal diagnostic reflections of asbestos minerals,
actually increasing the overall sensitivity of the method.12 l* (Further
investigation into preforred orientation effects in both thin layer and bulk
samples is required.)
2.3.5 Lack of Suitably Characterized Standard Materials
The problem of obtaining and characterizing suitable reference materials
for asbestos analysis is clearly recognized. NIOSH has recently directed a
major research effort toward the preparation and characterization of analytical
reference materials, including asbestos standards;16 17 however, these are not
available in large quantities for routine analysis.
31
-------
In addition, the problem of ensuring the comparability of st-iidara reference
and sample materials, particularly regarding crystallite size, oarticle size
distribution, and degree of crystal 1inity, has yet to b« aoequr-tely addressed.
For example, Langer et al.16 have observed that in insulating .'natr:ces, chryso-
tile tends to break open into bundles more frequently than amphiboles. This
results in a line-broadening effect with a resultant decrease in sensitivity.
Unless this effect is the same for both standard and sample materials, the
amount of chrysotile in the sampls will be" underestimated by XfiD analysis. To
minimize this problem, it is recommended that standardized matrix red-jctior,
procedures be used for both sample and standard materials.
2.4 PRECISION AND ACCURACY
Precision of the method has not been determined.
Accuracy of the method has not been determined.
2.5 APPARATUS
2.5.1 Sample Preparation
Sample preparation apparatus requirements will depend upon the sample
type under consideration and the kind of XRO analysis to be performed.
Mortar and Pestle: Agate or porcelain.
Razor Blades
Sample Mill: SPEX, Inc., freezer mill or equivalent.
Bulk Sample Holders
Silver Membrane Filters: 25-mm diameter, 0.45-pm pore size. Sulas
Corp. of America, Flotronics Div., 1957 Piercer Road, Huntir.yton
Valley, PA 19006.
Microscope Slides

'/acujm Filtration^Apparatus: 'Gelman No. 1107 or equivalent, and
side-arm vacuum fiask.
Hicrobalance
Ultrasonic Bath or Probe: Model W140, Ultrasonics, Inc., operated
at a power density of approximately 0.1 W/mt., or equivalent.
32
-------
Volumetric Masks: 1-L volume.

Assorted Pipettes

Pipette Bulb

Nonserrated Forceps

Polyethylene Wash Bottle

Pyrex Beakers: 50-mL volume.

Desiccator

Filter Storage Cassettes

Magnetic Stirring Plate and 3ars

Porcelain CruciL^e?

Muffle Furnace or Low Temperature Asher

2.5.2 Sample Analysis

Sample analysis requirements include an X-ray diffraction unit, equipped
with:

Constant Potential Generator; Voltage and mA Stabilizers

Automated Diffractorceter with Step-Scanning Mode

Copper Target X-Ray Tube: High intensity, fine focus, preferably.

X-Ray Pulse Height Selector

X-Ray Detector (with high voltage power supo'y): Scintillation or
proportional counter.

Focusing Graphite Crystal Monochromator; or Nickel Filter (if copper
source is used, and iryn fluorescence is not a serious problem).

Data Output Accessories:

Strip Chart Recorder

Decade Sealer/Timer

Digital Printer
33
-------
Sample Spinner (optional).
Instrument Calibration Reference Specimen: crquartz reference
crystal (Arkansas quartz standard, #180-147-00, Philips Elsctronics
Instruments, Inc., 85 McKee Drive, Mahwar, NJ 07430) or equivalent.
2.6 RFAGENTS
2.6.1 Standard Reference Materials
The reference materials listed below are intended to serve as a guida.
Every attempt should be made tc acquire pure reference materials that are
comparable to sample materials being analyzed.
Chrysotile: UICC Canadian, or NIEHS Plastibest. (UICC reference
materials available from: UICC, MRC Pneumoconiosis Unit, Llandough
Hospital, Penarth, Glamorgan, CF61XW, UK).
Crocidolite: UICC
Amosite: UICC
Anthopnyllite: UICC
Tremclite Asbestos: Wards Natural Science Establishment, Rochester,
N.Y.; Cyprus Research Standard, Cyprus Research, 2435 Military Ave.,
Los Angel?s, CA 90064 (washed with dilute HC1 to remove small
amount of calcite impurity); India tremolite, Rajasthan State,
India.
Actinolite Asbestos
2.6.2 Adhesive
Tape, petroleum jelly, etc. (for attaching silver membrane filters to
sample holders).
2.6.3 Surfactant
1 percent aerosol OT aqueous solution or equivalent.
2.6.4 Isopropanol
ACS Reagent Grade.
2.7 PROCEDURE
2.7.1 Samp]fng
Sampios for analysis of asbestos content shall be collected as specified
34
-------
in EPA Guidance Document #C0090, Asbestos-Containing Materials in School Build-
ings.1"
2.7.2 Analysis
All samples must be analyzed initially for asbestos content by PLM. XRD
should be used as an auxiliary method when a second, independent analysis is
requested.
NOTE: ASBESTOS IS A TOXIC SUBSTANCE. ALL HANDLING OF DRY MATERIALS
SHOULD BE PERFORMED IN AN OPERATING FUME HOOD.
2.7.2.1 Sample Preparation—
The method of sample preparation required for XRD analysis will depend
on: (1) the condition of the sample received (sample size, homogeneity,
particle size distribution, and overall composition as determined by PLM); and
(2) the type of XRD analysis to be performed (qualitative, quantitative, thin
layer or bulk).
Bulk materials are usually received as inhomogeneous mixtures of complex
composition with very wide particle size distributions. Preparation of a
homogeneous, representative sample from asbestos-containing materials is
particularly difficult because the fibrous nature of the asbestos minerals
inhibits mechanical mixing and stirring, and because milling procedures may
cause adverse lattice alterations.
A discussion of specific matrix reduction procedures is given below.
Complete methods of sample preparation are detailed in Sections 2.7.2.2 and
2.7.2.3. Note: All samples should be examined microscopically before and
after each matrix reduction step to monitor changes in sample particle size,
composition, and crystal!inity, and to ensure sample representativeness and
homogeneity for analysis.
2.7.2.1.1 Mi 11ing—Mechanical Milling of asbestos materials has been
shown to decrease fiber crystal 1inity, with a resultant decrease in diffraction
intensity of the specimen; the degree of lattice alteration is related to the
19-22
duration and type of milling process. Therefore, all milling times should
be kept to a minimum.
For qualitative analysis, particle size is not usually of critical impor-
tance and initial characterization of the material with a minimum of matrix
reduction is often desirable to document the composition of the sample as

35
-------
received. Bulk samples of very large particle size (>2-3 mm) should be com-
minuted to ~100 urn. A mortar and pestle can sometimes be used in size reduc-
tion of soft or loosely bound materials though this may cause matting of some
sa/nples. Such samples may be reduced by cutting with a razor blade in a mortar,
or by grinding in a suitable mill (e.g., a microhammer mill or equivalent).
When using a mortar for grinding or cutting, the sample should be moistened
with ethanol, or some other suitable wetting agent, to minimize exposures.
For accurate, reproducible quantitative analysis, the particle size of
both sample and standard materials should be reduced to ~10 urn (see Sec-
tion 2.3.3). Dry ball millir.^ at liquid nitrogen temperatures (e.g., Spex
Freezer Mill, or equivalent) for a maximum time of 10 min is recommended to
obtain satisfactory particle size distributions while protecting the integrity
of the crystal lattice.5 Bulk samples of very large particle size nay require
grinding in two stages for full matrix reduction to <10 urn.8 IS
Final particle size distributions should always be verified by optical
microscopy or another suitable method.
2.7.2.1.2 Low temperature ashing—For materials shewn by PLM to contain
large amounts of gypsum, cellulosic, or other organic materials, it may be
desirable to ash the samples prior to analysis to reduce background radiation
or matrix interference. Since chrysotile undergoes dehydroxylation at tempera-
tures between 550° C and 650° C, with subsequent transformation to forsterite,23 24
ashing temperatures should be kept below 500° C. Use of a low temperature asher
is recommended. In all cases, calibration of the oven is essential to ensure
that a maximum ashing temperature of 500° C is not exceeded.
2.7.2.1.3 Acid leaching—Because of the interference caused by gypsum
and some carbonates in the detection of asbestiform minerals by XRD (see
Section 2.3.1), it may be necessary to remove these interferents by a simple
acid leaching procedure prior to analysis (see Section 1.7.2.2).
2.7.2.2 Qualitative Analysis—
2.7.2.2.1 Initial screening of bulk material—Qualitative analysis
should be performed on a representative, homogeneous portion of the sample
with a minimum of sample treatment.
36
-------
1. Grind and mix the sample with a mortar and pestle (or equivalent
method, see Section 2.7.2.1.1.) to a final particle size suf-
ficiently small (-100 urn) to allow adequate packing into the
sample holder.
2. Pack the sample into a standard bulk sample holder. Care
should be taken to ensure that a representative portion of the
milled sample is selected for analysis. Particular care should
be taken to avoid possible size segregation of tna sample.
(Note: Use of a back-packing method25 of bulk sample prepara-
tion may reduce preferred orientation effects.)
3. Mount the sample on tiie Hiffractometer and scan over the diag-
o
nostic peak regions for the serpentine (~7.4 A) and amphibole
o
(8.2-8.5 A) minerals (see Table 2-2). The X-r-y diffraction
equipment should be optimized for intensity. A slow scanning
speed of 1° 26/min is recoiiunended for adequate resolution. Use
of a sample spinner is recommended.
4. Submit all samples that exhibit diffraction peaks in the diag-
nostic regions for asbestiform minerals to a full qualitative
XRD scan (5°-60° 28; 1° 29/min) to verify initial peak assign-
ments and to identify potentia! matrix interferences when
subsequent quantitative analysis is to be performed.
5. Compare the sample XRD pattern with standard reference powder
diffraction patterns (i.e., JCPOS powder diffraction data3 or
those of other well-character!zed reference materials).
Principal lattice spacings of asbestifom minerals are given in
Table 2-2; common constituents of bulk insulation and wall
materials are listed in Table 2-3.
2.7.2.2.2 Detection of minor or trace constituents—Routine screening of
bulk materials by XRO may fail to detect small concentrations (<5 percent) of
asbestos. The limits of detection will, in general, be improved if matrix
absorption effects are minimized, and if the sample particle size is reduced
to the optimal 1 to 10 urn range, provided that the crystal lattice is not
degraded in the milling process. Therefore, in those instances where confirma-
tion of the presence of an asbestiform mineral at very low levels is required,
37
-------
or where a negative result from initial screening of th3 bulk material by XRD
(sea Section 2.7.2.2.1) is in conflict with previous PLM results, it may be
desirable to prepare the sanple as described for quantitative analysis (see
Section 2.7.2.3) and step-scan over appropriate 29 ranges of selected diagnos-
tic peaks (Table 2-2). Accurate transfer of the sample to the silver membrane
filter is not necessary unless subsequent quantitative analysis is to be
performed.
2.7.2.3 Quantitative Analysis--
The proposed method for quantitation of asbestos in bulk samples is a
modification of the NIOSH-recommended thin-layer method for chrysotile in
air.5 A thick-layer o?* bulk method involving pelletizing the sample may be used
for semi quantitative analysis;7 8 however, this method requires the addition of
an internal standard, use of a specially fabricated sample press, and relatively
large amounts of standard reference materials. Additional research is required
to evaluate the comparability of thin- and thick-layer methods for quantitative
asbestos analysis.
For quantitative analysis by thin-layer methods, the following procedure
is recommended:
1. Mill and size al! or a substantial representative portion of the
sample as outlined in Section 2.7.2.1.1.
2. Dry at 100° C for 2 hr; cool in a desiccator.
3. Weigh accurately to the nearest 0.01 mg.
4. Samples shown by FLM to contain large amounts of cellulosic or other
organic materials, gypsum, or carbonates, should be submitted to
appropriate matrix reduction procedures described in Sections 2.7.2.1.2
and 2.7.2.1.3. After ashing and/or acid treatment, repeat the
drying and weighing procedures described above, and determine the
percent weight loss, L.
5. Quantitatively transfer an accurately weighed amount (50-100 mg) of
the sample to a 1-L volumetric flask with approximately 200 mL
isopropanol to which 3 to 4 drops of surfactant have been added.
6. illtrasonicate fr/r 10 min at a power density of approximately 0.1 W/mL,
to disperse thf sample material.
7. Dilute to voli-me with isoprcpanol.
38
-------
8. Place flask on a magnetic stirring plate. Stir.
9. Place a silver membrane filter or, the filtration apparatus, apply a
vacuum, and attach the reservoir. Re.ease the vacuum and add several
mil 1iliters of isopropanol to the reservoir. Vigorously hand shake
the asbestos suspension and immediately withdraw an aliquot from the
center of the suspension so that tota'i sample weight, W,, on the
filter will be approximately 1 ;ng. Do not adjust the volume in the
pipet. by expelling part of the suspension; if more than the desired
aliquot is withdrawn, discard the aliquot and resume the procedure
with a clean pipet. Transfer the aliquot to the reservoir. Filter
rapidly under vacuum. Do not wash the reservoir wells. Leave the
filter apparatus under vacuum until dry. Remove the reservoir, re-
lease the vacuum, and remove the filter with forceps. (Note: Water-
soluble matrix interferences such as gypsum may be removed at this
time by careful washing of the filtrate with distilled water. Extreme
care should be taken not to disturb the sample.)
10. Attach the filter to a flat holder with a suitable adhesive and place
on the d'ffractometer. I'se of a sample spinner is recommended.
11. For each asbestos mineral to be quantitated select a reflection (or
reflections) that has been shown to be . ,'ee from interferences by
prior PLM or qualitative XRO analysis and that can be used unambi-
guously as an index of the amount of material present in the sample
(see Table 2-2).
12. Analyze the selected diagnostic reflection(s) by step scanning in
increments of 0.02° 29 for an appropriate fixed time and integrating
the counts. (A fixed count scan may be used alternatively; however,
the method chosen should be used consistently for all samples and
standards.) An appropriate scanning interval should be selected for
each peak, and background corrections made. For a fixed time scan,
measure the background on each side of the peak for one-half the
peak-seaming time. The net intensity, I , is the difference between
Q
the peak integrated count and the total background count.
o
13. Determine the net count, I. , of the filter 2.36 A silver peak
following the procedure in step 12. Remove the filter from the
39
-------
holder, reverse it, and reattach it to the holder. Determine the
net count for the unattenuated silver peak, I? . Scan times may be
"9
less for measurement of silver peaks than for sample peaks; however,
they should be constant throughout the analysis..
14. Normalize all raw, net intensities (to correct for instrument insta-
bilities) by referencing them to an external standard (e.g., the
o
3.34 A peak of an or-quartz reference crystal). After each unknown
is scanned, determine the net count, 1° of the reference specimen
following the procedure in step 12. Determine the normalized inten-
sities oy dividing the peak intensities by I*:

;a - ~ • 'AC, = ^ ' and O, = ^
3 TO "R TO «g TO
r r r
2.8 CALIBRATION
2.8.1 Preparation of Calibration Standards
1. Mill and size standard asbestos materials according to the procedure
outlined in Section 2.7.2.1.1. Equivalent, standardized matrix reduc-
tion and sizing techniques should be used for both standard and sample
materials.
2. Dry at 100° C for 2 hr; cool in a desiccator.
3. Prepare two suspensions of each standard in isopropanol by weighing
approximately 10 and 50 mg of the dry material to the nearest 0.01 mg.
Quantitatively transfer each to a 1-L volumetric flask with approxi-
mately 200 mL isopropanol to which a few drops of surfactant have
been added.
4. Ultrasonicate for 10 nrin at a power density of approximately 0.1 W/mL,
to disperse the asbestos material.
5. t'ilute to volume with isopropanol.
6. (Mace the flask on a magnetic stirring plate. Stir.
7. Prepare, in triplicate, a series of at least five standard filters
to cover the desired analytical range, using appropriate aliquots of
the 10 and 50 mg/L suspensions and the following procedure.
Mount a silver membrane filter on the filtration apparatus.
40
-------
Place a few milliliters of isopropanol in the reservoir. Vigorously
hand shake the asbestos suspension and immediately withdraw an
aliquot from the center of the suspension. Do not adjust the volume
in the pipet by expelling part of the suspension; if more than the
desired aliquot is withdrawn, discard the aliquot and resume the
procedure with a clean pipet. Transfer the aliquot to the reservoir.
Keep the tip of the pipet near the surface cf the isopropanol.
Filter rapidly under vacuum. Do not wash the sides of the reservoir.
Leave the vacuum on for a time sufficient to dry the filter. Release
the vacuum and remove the filter with forceps.
2.8.2 Analysis of Calibration Standards
1. Mount each filter on a flat holder. Perform step scans on selected
diagnostic reflections of the standards and reference specimen using
the procedure outMned in Section 2.7.2.3, step 12, and the same
conditions as those used for the samples.
2. Determine the normalized intens-'ty for each peak measured, I°*d, as
outlined in Section 2.7.2.3, step 14.
2.9 CALCULATIONS
For each asbestos reference material, calculate the exact weight deposited
on each standard filler from the concentrations of the standard suspensions
and aliquot volumes. Record the weight, w, of each standard. Prepare a
calibration curve by regressing 1° on w. Pyor reproducibility (±15 percent
R50) at any given level indicates problems in the sample preparation technique,
and a need for new standards. The data should fit a straight line equation.
Determine the slope, m, of the calibration curve in counts/microgram.
The intercept, b, of the line with the I°t. axis should be approximately zero.
A large negative intercept indicates an error in determining the background.
This may arise from incorrectly measuring the baseline or from interference by
another phase at the angle of background measurement. A large positive inter-
cept indicates an error in determining the baseline or that an impurity is
included in the measured peak.
f*
Using the normalized intensity, I., for the attenuated silver peak of a
sample, and the corresponding normalized intensity from the unattenuated
41
-------
silver peak, I? , of the sample filter, calculate the transmittance, T, for

each sample as follows:26 2?
Determine the correction factor, f(T), for each sample according to the

formula:
f(T) =
i-r

where

sin 9Ao
R = - =3-
sin 9
Q

Sin = angular position of the measured silver peak (from Bragg1s Law), and
«g

8 = angular position of the diagnostic asbestos peak.
cl

Calculate the weight, W , in micrograms, of the asbestos material analyzed
a

for in iach sample, using the appropriate calibration data and absorption

corrections:

If(t) - b
Calculate the percent composition, P , of each asbestos uineral analyzed
3

for in the parent material, from the total sample weight, W,, on the filxar:

Wa (1-.01L)

Pa = -i-^. x 100

where

P = percent asbestos mineral in parent material;
a

W = mass of asbestos mineral on filter, in ug;

W, = total sample weight on filter, in ug;

L = percent weight loss of parent material on ashing

and/or acid treatment (see Section 2.7.2.3).
42
-------
2.iO REFERENCES

1. H. P. Klug and L. E. Alexander, X-ray Diffraction Procedures for Poly-
crystalline and Amorphous Materials, 2nd ad. . New fork:John Wiley and
Sons, 1979.

2. L. V. Azaroff and M. J. Buerger, The Powder Method of X-ray Crystal log-
rap hyt New York: McGraw-Hill, IS5S.

3. JCPOS-International Canter for Diffraction Data Powder Diffraction File,
U.S. Department of Commerce, National Bureau of Standards, a;id Joint Com-
mittee on Powder Diffraction Studies, Swarthmore, PA.

4. W. J. Campbell, C. W. Muggins, and A. G. Wylfe, Chemical and Physical
Characterization of Amositej ChrysotiTe; CrocidoTTte, and Nonfi'brous~
TremoTice for National Institute of Environmental Health Sciences Oral
Ingestion Studies, U.S. Bureau of Mines Report of Investigation RI8452,
1980.

5. 8. A. Lange and j. C. Haartz, Determination of microgram quantities of
asbestos by X-ray diffraction: Chrysotile in thin dust layers of matrix
material, Anal. Chorn.. £1(4): 520-525, 1979.

6. NIOSH Manual of Analytical Methods. Volume 5, U.S. Oept. HEW, August 1379,
pp. 309-1 to 309-9.

7. H. Dunn and J. H. Stewart, Jr., Quantitative determination of Chrysotile
in building materials, The Microscope, 29(1), 1981.

8. M. Taylor, Methods for the quantitative determination of asbestos and
quartz In bulk samples using X-ray diffraction, The Analyst, 103(1231):
1009-1020, 1978.

9. L. Birks, M. Faterai, J. V. Gilfrich, and E. T. Johnson, Quantitative
Analysis of Airborne Asbestos by X-ray Diffraction, Naval Research Labora-
tory Report 7879, Naval Research Laboratory, Washington, D.C., 1975.

10. U.S. Environmental Protection Agency, Asbestos-Containing Materials in
School Buildings: A Guidance Document, Parts 1 and 2. EPA/OTS No. C00090,
March 1979.

11. J. 8. Krause and W. H. Ashton, Misidentification of asbestos in talc,
pp. 339-353, in: Proceedings of Workshop on Asbestos: Definitions and
Measurement Methods (N8S Special Publication 505), C. C. Gravatt,
P. D. LaFlejr, and X. F. Heinrich (eds.), Washington, D.C.: National
Measurement Laboratory, National Bureau of Standards, 1977 (issued 1978).

12. H. D. Stanley, The detection and identification or" asbestos and asbesti-
fonn minerals in talc, pp. 325-337, in Proceedings of Workshop on Asbestos:
Definitions and Measurement Methods ^NBS Special Publication 506),
C. C. Gravatt, P. D. LaFleur, and K. F. Heinrich (ec's.), Washington, D.C.
43
-------
National Measurement Laboratory, National Bureau of Standards, 1977 (issued
1978).

13. A. L. Rickards, Estimation of trace amounts of chrysotile asbestos by X-ray
diffraction, Anal. Chem.. 44(11):1872-3, 1972.

14. P. M. Cook, P. L. Smith, and D. G. Wilson, Amphibole fiber concentration
and determination for a series of community air samples: use of X-ray
diffraction to supplement electron microscope analysis, in: Electron Micros-
copy and X-Ray Applications to Environmental and Occupation Health Analysis,
P. A. Russell and A. E. Hutchings (eds.), Ann Arbor: Ann Arbor Science
Publications, 1977.

15. A. N. Rohl and A. M. Langer, Identification and quantitation of asbestos
in talc, Environ. Health Perspectives. 9:95-109, 1974.

16. J. L. Graf, P. K. Ase, and R. G. Oraftz, Preparation and Characterization
of Analytical Reference Minerals. DHEW (NIOSH) Publication No. 79-139,
June 1979.

17. J. C. rlaartz, B. A. Lange, K. G. Oraftz, and R. F. Scholl, Selection and
characterization of fibrous and nonfibrous amphiholes for analytical
methods development, pp. 295-312, in: Proceedings of Workshop on Asbestos:
Definitions and Measurement Methods (NBS Special Publication 506),
C. C. Gravatt, P. 0. LaFleur, and K. F. Heinrich (eds.), Washington, D.C.:
National Measurement Laboratory, National Bureau of Standards, 1977 (issued
1978).

18. Personal communication, A. M. Langer, Environmental Sciences Laboratory,
Mount Sinai School of Medicine of the City University of New York, New
York, New York.

19. A. M. Langer, M. S. Wolff. A. N. Rohl, and I. J. Selikoff, Variation of
properties of chrysotile asbestos subjected to milling, J. Toxicol. and
Environ. Health. 4:173-188, 1978.

20. A. M. Langer, A. 0. Mackler, and F. D. Pooley, Electron microscopical
investigation of asbestos fibers, Environ. Health Perspect., 9:63-80,
1974.

21. E. Cecelia and G. Maddalon, X-ray diffraction characteristics of some
types of asbestos in relation to different techniques of comminution,
Med. Lavoro. 54(10):628-636, 1963.

22. K. R. Spurny, W. Stb'ber, H. Opiela, and G. Weiss, On the problem of milling
and ultrasonic treatment of asbestos and glass fibers in biological and
analytical applications, Am. Ind. Hyg. Assoc. J., 41:198-203, 1980.

23. L. G. Berry and 8. Mason, Mineralogy. San Francisco: W. H. Greeman & Co.,
1959.
44
-------
24. J. P. Schelz, The detection of chrysotile asbestos at low levels in talc
by differential thermal analysis, Thermochimien Acta, 8:197-204, 1974.

25. Reference 1, pp. 372-374.

26. J. Leroux, Staub-Reinhalt Luft. 29:26 (English), 1969.

27. J. A. Larcux, B. C. Davey, and A. Paillard, Am. Ind. Hyq. Assoc. J., 34:409,
1973.
45
-------
-------