Polarized light microscopy qualitative analysis: For each type of material identified by examination of sample at low magnifica o
tion. Mount spacially dispersed sample in 1.550 RI liquid. (If using dispersion staining, mount in 1.550 HD.) View at 100X with
both plane polarized light and crossed polars. More than one fiber type may be present.

Fibers

Fibers
absent

present

Examine two additional prepared slides at 100X

‘ +
-———————~ Fibers present Fibers absent
‘

Examination complete.

Fibers are isotropic (disappear at all Fibers are anisotropic {exhibit
Report no asbestos

angles of stage rotation with crossed extinction at 90° intervals of

polars) stage rotation.) present.
Possible fibers include:
Fiberglass: 1-20 um uniform diameter.
RI typically < 1.53
Mineral wool: 8-200 um diameter, 1. Determine extinction characteristics.
bulbous ends and shot. 2. Determine sign of elongation.
Ri typically > 1.53 |
v v
Positive Negative
t v
t Mount in 1.700 Ri liquid.
n= 1.550 All n's > 1.550 ———————* Mount in 1.680 RI liquid onernine oho logy for
eptermnine 7 ; crocidolite.
phology for chrysotile. n= 1,680 All n's < 1.680
If fibers are twisted and exhibit Determine n.
internal details, cellulose is indicated. Check morphology Mount in 1.605 RI liquid.

for “amosite”. Determine n.
Check morphology and
characteristics for anthophyllite-asbestos,
tremolite-actinolite-asbestos.

Figure 1-1. Flow chart for qualitative analysis of bulk samples by polarized light microscopy.


count, I?, of the reference
specimen following the
procedure in step 12. Determine
the normalized intensities by
dividing the peak intensities by

IP.

=18, and [Rg = By
?

1a=48 laa i

f

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 reduction
and sizing techniques should be
used for both standard and
sample materials.

2. Dry at 100°C for 2 hr; cool ina
desiccator.

3. Prepare two suspensions of each
standard in tsopropanol 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 approximately 200 mL
isopropanol to which a few drops
of surfactant have been added.

4. Ultrasonicate for 10 min ata
power density of approximately
0.1 W/mL, to disperse the
asbestos material.

5. Dilute to volume with
isopropanol.

6. Place 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 suspen-
sions. For each standard, mount a
silver membrane filter on the
filtration apparatus. Place a few
mL of isopropanol in the reservoir.
Vigorously hand shake the
asbestos suspension and immedi-
ately 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 of 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
outlined in Section 2.7.2.3, step
12, and the same conditions as
those used for the samples.

2. Determine the normalized
intensity for each peak
measured, I%1a, 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 filter from
the concentrations of the standard
suspensions and aliquot volumes.
Record the weight, w, of each
standard. Prepare a calibration curve
by regressing [Sa on w. Poor
reproducibility (+15 percent RSD) 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%q 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 back-
ground measurement. A large positive
intercept indicates an error in
determining the baseline or that an
impurity is included in the measured
peak,

Using the normalized intensity, lag,
for the attenuated silver peak of a
sample, and the corresponding
normalized intensity from the unattenu-
ated silver peak, i, of the sample
filter, calculate the transmittance, T,
for each sample as follows:7°7”

=e
Tig,
Determine the correction factor, f(T),

for each sample according to the
formula:

f(T) = Ln)
1-1
where
R= SIN Mag
sin 6.

Gag = angular position of the measured

silver peak (from Bragg’s Law), and.

6, = angular position of the diagnostic
asbestos peak.

10

Calculate the weight, Wa, in
micrograms, of the asbestos material
analyzed for in each sample, using the
appropriate calibration data and
absorption corrections:

Wa= le f(t)-b
m

Calculate the percent composition,
P,, of each asbestos mineral analyzed
for in the parent material, from the
total sample weight, Wr, on the filter:

p, = Wa (1--01U)

x 100
Wr
where
Pa = percent asbestos mineral in
parent material;
Wa = mass of asbestos mineral on
filter, in yg;
Wy; = total sample weight on filter, in
Hug;
L = percent weight loss of parent

material on ashing and/or acid
treatment (see Section 2.7.2.3).

2.10 References

1. H. P. Klug and L. E. Alexander, X-
ray Diffraction Procedures for
Polycrystalline and Amorphous
Materials, 2nd ed., New York:
John Wiley and Sons, 1979.

2. L.V. Azaroff and M. J. Buerger,
The Powder Method of X-ray
Crystallography, New York:
McGraw-Hill, 1958.

3. JCPDS-International Cemer for
Diffraction Data Powder
Diffraction File, on Powder
Diffraction Studies, 1601 Park
Lane, Swarthmore, PA.

4. W. J. Campbell, C. W. Huggins,
and A. G. Wylie, Chemical and
Physical Characterization of
Amosite, Chrysotile, Crocidolite,
and Nonfibrous Tremolite for
National Institute of .
Environmental Health Sciences
Oral Ingestion Studies, U.S.
Bureau of Mines Report of
Investigation RI8452, 1980.

5. B.A. Lange and J. C. Haariz,
Determination of microgram
quantities of asbestos by X-ray
diffraction: Chrysotile in thin dust
layers of matrix material, Ana/.
Chem., 61(4):520-525, 1979.

6. NIOSH Manual of Analytical
Methods, Volume 5, U.S. Dept.
HEW, August 1979, pp. 309-1 to
309-9.

7. H.W. Dunn and J. H. Stewart, Jr.,
Determination of chrysotile in
buiding materials by X-ray
Diffractometry, Anal. Chem., 54
(7), 1122-1125, 1982.


anthophyllite, crocidolite, and
tremolite. Calcium carbonate
(CaCOs) has a peak at 3.035 A that
overlaps major amphibole peaks at
approximately 3.1 A when present
in concentrations of >5 percent.
Removal of carbonates with a
dilute acid wash is possible;
however, if present, chrysotile may
be partially dissolved by this
treatment."

@ A major talc peak at 3.12 A inter-
feres with the primary tremolite
peak at this same position and with
secondary peaks of crocidolite
(3.10 A}, amosite (3.06 A), and
anthophyllite (3.05 A). In the
presence of talc, the major
diagnostic peak at approximately
8.3 A should be used for
quantitation of these asbestiform
minerals.

The problem of intraspecies and
matrix interferences is further
aggravated by the variability of the
silicate mineral powder diffraction
patterns themselves, 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
isomorphous substitution and degree
of crystallinity. This is especially true
for the amphiboles. These minerals
exhibit a wide variety of very similar
chemical compositions, with the result
being that their diffraction patterns are
characterized by having major (110)
reflections of the monoclinic
amphiboles and (210) reflections of the
orthorhombic anthophyllite separated
by less than 0.2 A.!?

2.3.2 Matrix Effects

\f a copper X-ray source is used, the
presence of iron at high
concentrations in a sample will result
in significant X-ray fluorescence,
leading to loss of peak intensity
with increased background intensity
and an overall decrease in sensitivity.
This situation may be corrected by
use of an X-ray source other than
copper; however, this is often accom-
panied both by loss of intensity and by
decreased resolution of closely spaced
reflections. Alternatively, use of a
diffracted beam monochromator will
reduce background fluorescent
radiation, enabling weaker diffraction
peaks to be detected.

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.°'*'* However,
unless absorption effects are known to
be the same for both samples and
standards, appropriate corrections
should be made by referencing
diagnostic peak areas to an internal
standard’® or filter substrate (Ag)
peak.°*

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
standard reference materials have
similar particle size distributions. The
optimum particle size (i.e., fiber length)
range for quantitative analysis of
asbestos by XRD has been reported to
be 1 to 10 pm.'® Comparability of
sample and standard reference material
particle size distributions should be
verified by optical microscopy (or
another suitable method) prior to analysis.

2.3.4 Preferred Orientation Effects
Preferred orientation of asbestiform
minerals during sample preparation
often poses a serious problem in
quantitative analysis by XRD. A
number of techniques have been
developed for reducing preferred
orientation effects in “thick layer”
samples.”®'® 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.'?,’* However, further
investigation into preferred 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; '®"7
however, these are not available in
large quantities for routine analysis.

In addition, the problem of ensuring
the comparability of standard
reference and sample materials,
particularly regarding crystallite size,
particle size distribution, and degree of
crystallinity, has yet to be adequately
addressed. For example, Langer et al."®
have observed that in insulating
matrices, chrysotile 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 sample will be under-
estimated by XRD analysis. To
minimize this problem, it is
recommended that standardized matrix
reduction 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 XRD analysis to be

performed.

@ Mortar and Pestle: Agate or
porcelain

@ Razor Blades

@ Sample Mil: SPEX, inc., freezer
mill or equivalent

@ Bulk Sample Holders

@ Silver Membrane Filters: 25-mm
diameter, 0.45-um pore size. Selas
Corp. of America, Flotronics Div.,
1957 Pioneer Road, Huntington
Valley, PA 19006

@ Microscope Slides

@ Vacuum Filtration Apparatus:

Gelman No. 1107 or equivalent,

and side-arm vacuum flask

Microbalance

Ultrasonic Bath or Probe: Model

W140, Ultrasonics, Inc., operated

at a power density of approximately

0.1 W/mL, or equivalent

Volumetric Flasks: 1-L volume

Assorted Pipet

Pipet Bulb

Nonserrated Forceps

Polyethylene Wash Bottle

Pyrex Beakers: 50-mL volume

Desiccator

Filter Storage Cassettes

Magnetic Stirring Plate and Bars

Porcelain Crucibles

Muffle Furnace or Low Temprature

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 Diffractometer 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 supply): Scintillation or
Proportional counter



2.1 Principle and Applicability

The principle of X-ray powder
diffraction (XRD) analysis is well
established." Any solid, crystalline
material will diffract an impingent
beam of parallel, monochromatic X-
rays whenever Bragg’s Law,

A=2dsin 6,

is satisfied for a particular set of
planes in the crystal lattice, where

A= the X-ray wavelength, A;

d= the interplanar spacings of the
set of reflecting lattice planes, A;
and

@= 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
crystalline 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 XRD
methods, samples are initially scanned
over limited diagnostic peak regions
for the serpentine (~7.4 A) and
amphibole (8.2-8.5 A) minerals (Table
2-2). Standard slow-scanning methods
for bulk sample analysis may be used
for materials shown by PLM to contain
significant amounts of asbestos (>5-
10 percent). Detection of minor or
trace amounts of asbestos may require
special sample preparation and step-
scanning analysis. All samples that
exhibit diffraction peaks in the
diagnostic regions for asbestiform
minerals are submitted to a full (5°-
60° 24 1° 26/min) qualitative XRD
scan, and their diffraction patterns are
compared with standard reference
powder diffraction patterns? to verify
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 matrix absorption
effects, and comparability of standard
reference and sample materials. The
most intense diffraction peak that has
been shown to be free from
interference by prior qualitative XRD
analysis is selected for quantitation of
each asbestiform mineral, A “thin-
layer” method of analysis** is
recommended in which, subsequent to
comminution of the bulk material to
~10 um 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.
Alternative “thick-layer” or bulk
methods,”* may be used for
semiquantitative 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
variable 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 indistinguish-
able by XRD techniques unless special
sample preparation techniques and
instrumentation are used,® the
presence of nonasbestiform
serpentines and amphiboles in a
sample will pose severe interference
problems in the identification and
quantitative analysis of their asbesti-
form analogs.

6

2. X-Ray Powder Diffraction

The use of XRD for identification and
quantitation of asbestiform minerals in
bulk 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 interfer-
ences may vary greatly (Table 2-3) and
present more serious problems in
identification and quantitation. '°
Potential interferences are
summarized in Table 2-4 and include
the following:
®@ Chlorite has major peaks at 7.19 A

and 3.58 A that interfere with 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.

@ Halloysite has a peak at 3.63 A that
interferes with the secondary (3.66
A) peak for chrysotile.

e Kaolinite has a major peak at 7.15
A that may interfere with the
primary peak of chrysotile at’ 7.36
A when present at concentrations
of >10 percent. However, the
secondary chrysotile peak at 3.66
A may be used for quantitation.

© Gypsum has a major peak at 7.5A
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 heating to
300°C to convert gypsum to plaster
of paris.

@ Cellulose has a broad peak that
partially overlaps the secondary
(3.66 A) chrysotile peak.®

@ Overlap of major diagnostic peaks
of the amphibole asbestos
minerals, amosite, anthophyllite,
crocidolite, and tremolite, at
approximately 8.3 A and 3.1A
causes mutual interference when
these minerals occur in the
presence of one another. In some
instances adequate resolution may
be attained by using step-scanning
methods and/or by decreasing the
collimator slit width at the X-ray
port.

@ Carbonates may also interfere with
quantitative analysis of the amphi-
bole asbestos minerals, amosite,


preparation may reduce preferred
orientation effects.)

3. Mount the sample on the diffrac-
tometer and scan over the
diagnostic peak regions for the
serpentine (~7.4 A) and amphibole
(8 2-8.5 A) minerals (see Table
2-2). The X-ray diffraction equip-
ment should be optimized for
intensity. A slow scanning speed
of 1° 28/min is recommended for
adequate resolution. Use of a
sample spinner is recommended

4. Submit all samples that exhibit
diffraction peaks in the diagnostic
regions for asbestiform minerals to
a full qualitative XRD scan (5°-60°
26; 1° 28/min) to verify initial peak
assignments and to identify
potential matrix interferences
when subsequent quantitative
analysis ts to be performed.

5. Compare the sample XRD pattern
with standard reference powder
diffraction patterns (i.e, JCPDS
powder diffraction data ° or those
of other well-characterized
reference materials). Principal
lattice spacings of asbestiform
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 XRD may fail to
detect small concentrations (<5
percent) of asbestos. The limits of
detection will, in general, be improved
if matrix absorption effects are mini-
mized, and if the sample particle size is
reduced to the optimal 1 to 10 um
range, provided that the crystal lattice
(s not degraded in the milling process.
Therefore, in those instances where
confirmation of the presence of an
asbestiform mineral at very low levels
is required, or where a negative result
from initial screening of the bulk
material by XRD (see Section
2.7.2.2.1) is in conflict with previous.
PLM results, it may be desirable to
prepare the sample as described for
quantitative analysis (see Section
2.7.2.3) and step-scan over
appropriate 26 ranges of selected
diagnostic peaks (Table 2-2). Accurate
transfer of the sample to the silver
membrane filter 1s not necessary
unless subsequent quantitative
analysis is to be performed.

2.7.2.3. Quantitative Analysis

The proposed method for quantita-
tion of asbestos in bulk samples is a
modification of the NIOSH-
recommended thin-layer method for
chrysotile in air ® A thick-layer or bulk

method involving pelletizing the
sample may be used for semiquantita-
tive analysis;”* 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
1s recommended:

1.

2

Mill and size all or a substantial
representative portion of the
sample as outlined in Section
2.72.1.1.

Dry at 100°C for 2 hr; cool ina
desiccator.

Weigh accurately to the nearest
0.01 mg.

Samples shown by PLM 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.

Quantitatively transfer an
accurately weighed amount (50-
100 mg) of the sample to a 1-L
volumetric flask with approxi-
mately 200 mL isopropanol to
which 3 to 4 drops of surfactant
have been added.

Ultrasonicate for 10 min at a
power density of approximately
0.1 W/mL, to disperse the
sample material.

Dilute to volume with
isopropanol.

Place flask on a magnetic stirring
plate. Stir.

Place a silver membrane filter on
the filtration apparatus, apply a
vacuum, and attach the
reservoir. Release the vacuum
and add several milliliters of
Jsopropanol to the reservoir.
Vigorously hand shake the
asbestos suspension and
immediately withdraw an aliquot
from the center of the
suspension so that total sample
weight, Wr, on the filter will be
approximately 1 mg. 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

9

10.

11.

12.

13.

clean pipet. Transfer the aliquot
to the reservoir. Filter rapidly
under vacuum. Do not wash the
reservoir walls. Leave the filter
apparatus under vacuum until
dry. Remove the reservoir,
release the vacuum, and remove
the filter with forceps (Note:
Water-soluble matrix interfer-
ences 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.)

Attach the filter to a flat holder
with a suitable adhesive and
place on the diffractometer. Use
of a sample spinner is
recommended.

For each asbestos mineral to be
quantitated, select a reflection (or
reflections) that has been shown
to be free from interferences by
prior PLM or qualitative XRO
analysis and that can be used
unambiguously as an index of
the amount of material present
in the sample (see Table 2-2).
Analyze the selected diagnostic
reflection(s) by step scanning in
increments of 0.02° 2 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-
scanning time. The net intensity,
|, is the difference between the
peak integrated count and the
total background count.
Determine the net count, lag, of
the filter 2.36 A silver peak
following the procedure in step
12. Remove the filter from the
holder, reverse it, and reattach it
to the holder. Determine the net
count for the unattenuated silver
peak, lg. Scan times may be /ess
for measurement of silver peaks
than for sample peaks; however,
they should be constant
throughout the analysis.
Normalize all raw, net intensities
{to correct for instrument instabil-
ities) by referencing them to an
external standard (e.g., the 3.34
A peak of an a-quartz reference
crystal). After each unknown ts
scanned, determine the net


a

EPA

United States
Environmental Protection
Agency

Environmental Monitoring Systems
Laboratory
Research Triangle Park NC 27711

Research and Development

EPA-600/M4-82-020 Dec. 1982

Test Method

Interim Method for the
Determination of Asbestos in
Bulk Insulation Samples*

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 of
suspect fibers is made by analysis of
subsamples with the polarized light
microscope.

The principles of optical mineralogy
are well established. "? A light
microscope equipped with two
polarizing filters is used to observe
specific optical characteristics of a
sample. The use of plane polarized-
fight 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 orthoscopic
illumination. Orientation of the two
filters such that their vibration planes
are perpendicular (crossed polars)
allows observation of the birefringence
and extinction characteristics 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 minerals in thin
sections of rock, Background
information on the use of point
counting’ and the interpretation of

point count data® is available.

An ‘method is carefully drafted from avail-
able source information. This method is still under
investigation and therefore is subject to revision.

This method is applicable to ail bulk
samples of friable insulation materials.
submitted for identification and
quantitation of asbestos components.

1.2 Range

The point counting method may be
used for analysis of samples
containing from O to 100 percent
asbestos. The upper detection limit is
100 percent. The lower detection limit
is less than 1 percent.

1.3 Interferences

Fibrous organic and inorganic
constituents of bulk samples may
interfere with the identification and
quantitation 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 may 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 report Bulk
Sample Analysis for Asbestos Content:
Evaluation of the Tentative Method.*

1.5 Apparatus

1.5.1 Sample Analysis
A tow-power binocular microscope,
preferably stereoscopic, is used to


Table 2-3.

Common constituents in insulation and

wall materials (from Ref. 10)

A. Insulation materials

8. Spray finishes or paints

Table 2-4, interferences in XRD analysis

of asbestiform minerals

Primary diagnostic
Asbestiform peaks (approxmate

mineral d-spacings in Aj Interference
Chrysotile Bassanite ; Serpentine
amosite” Carbonate verte) (calcite, Chrysotile 74 Nonasbestiform ser-
“Re . pentines (antigorite,
‘ock wool Tale hard:
* 5 izardite)
‘Slag wool Tremolite Chlorite
*Fiber glass Anthophyllite init
gi thophy Kaolinite
Gypsum (CaSO« - 2H20) Serpentine (including chrysotile) Gypsum
Vermiculite (micas) “amosite® *P
“Perlite Crocidotte 37 Nonasbestiterm serp-
Clays (kaalin) *Mineral wool entines, (antigorite,
“Wood pulp “Rock wool lizardite)
*Paper fibers (talc, clay, *Slag wool -
carbonate fillers) “Fiber glass eerie
Calcium silicates (synthetic) Clays (kaolin) Cellulose
Opaques (chromite, magnetite Micas ellulose
inclusions in serpentine) Chlorite Amphibole
Hematite (inclusions in Gypsum (CaSO«2H20) “Amosite” 3.1 Nonasbestiform amphi-
“amosite”) Quartz Anthophyllite boles (cummingtonite-
Magnesite *Organic binders and thickeners Crocidolite grunerite, anthophyllite,
*Diatomaceous earth Hydromagnesite Tremolite riebeckite, tremolite)
Wollastonite Mutual interferences
Opaques (chromite, magnetite Carbonates
inclusions in serpentine) Tale
Hematite (inclusions ia 83 Nonasbestitorm
‘amosite”) amphiboles (cumming-
i _ tonite, grunerite,
*Amorphous matertals--contribute anly to overall scattered ' radiation anthophyllite, reibeckite,
and increased background radiation. tremolite)
Mutual interferences
Postage and
United States Center for Environmental Research Fees Paid
Environmental Protection Information Environmenta!
Agency Cineinnats OH 45268, Protection
Agency
EPA 335, y
Official Business
Penalty for Private Use $300
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8. M. Taylor, Methods for the samples: Use of X-ray diffraction 19. A.M. Langer, M. S. Wolff, A. N.
quantitative determination of to supplement electron Rohl, and |. J. Selikoff, Variation
asbestos and quartz in bulk microscope analysis, In: Electron of properties of chrysotile
samples using X-ray diffraction, Microscopy and X-ray asbestos subjected to milling, J.
The Analyst, 103(1231):1009- Applications to Environmental Toxicol. and Environ. Health,
1020, 1978. and Occupation Health Analysis, 4:173-188, 1978.

9. L Birks, M. Fatemi, J. V. Gilfrich, P.A. Russell andA.£. Hutchings 20. A.M. Langer, A. D. Mackler, and
and E. T. Johnson, Quantitative (eds.), Ann Arbor: Ann Arbor F. D. Pooley, Electron
Analysis of Airborne Asbestos by Science Publications, 1977. microscopical investigation of
X-ray Diffraction, Naval Research 15. A.N. Rohl and A. M. Langer, asbestos fibers, Environ. Health
Laboratory Report 7879, Naval Identification and quantitation of Perspect., 9:63-80, 1974.
Research Laboratory, asbestos in talc, Environ. Health 21. E. Occella and G. Maddalon, X-
Washington, DC, 1975. Perspectives, 9:95-109, 1974. ray diffraction characteristics of

10. U.S. Environmental Protection 16. J.L. Graf, P. K. Ase, and R. G. some types of asbestos in
Agency, Asbestos-Containing Draftz, Preparation and relation to different techniques of
Materials in School Buildings: A Characterization of Analytical comminution, Med. Lavoro,
Guidance Document, Parts 1 and Reference Minerals, DHEW 54(10):628-636, 1963.

2, EPA/OTS No. CO00090, March (NIOSH) Publication No. 79-139, 22K. R. Spurny, W. Stéber, H.
1979. June 1979. Opiela, and G. Weiss, On the

11. J.B. Krause and W. H. Ashton, 17. J.C. Haartz, B. A. Lange, R. G. problem of milling and ultrasonic
Misidentification of asbestos in Draftz, and R. F. Scholl, Selection treatment of asbestos and glass
talc, pp. 339-353, In: and characterization of fibrous fibers in biological and analytical
Proceedings of Workshop on and nonfibrous amphiboles for applications, Am. Ind. Hyg.
Asbestos: Definitions and analytical methods development, Assoc. J., 41:198-203, 1980.
Measurement Methods (NBS pp. 295-312, tn: Proceedings of 23. L.G. Berry and B. Mason,
Special Publication 506), C. C. Workshop on Asbestos: Mineralogy, San Francisco: W. H.
Gravatt, P. D. LaFleur, and K. F. Definitions and Measurement Greeman & Co., 1959.

Heinrich (eds.), Washington, DC: Methods (NBS Special 24. J.P. Schelz, The detection of
National Measurement Publication 506), C. C. Gravatt, P. chrysotile asbestos at low levels
Laboratory, National Bureau of D. LaFleur, and K. F. Heinrich In talc by differential thermal
Standards, 1977 (issued 1978). (eds.), Washington, DC: National analysis, Thermochimica Acta,

12. H.D. Stanley, The detection and Measurement Laboratory, 8:197-204, 1974.
identification of asbestos and National Bureau of Standards, 25. Reference 1, pp. 372-374.
asbestiform minerals in talc, pp. 1977 (issued 1978). 26. J. Leroux, Staub-Reinhalt Luft,
325-337, In: Proceedings of 18. Personal communication, A. M. 29:26 (English), 1969.

Workshop on Asbestos: Langer, Environmental Sciences 27. J. A. Leroux, B. C. Davey, and A.
Definitions and Measurement Laboratory, Mount Sinai School Paillard, Am. ind. Hyg. Assoc. J.,
Methods (NBS Special of Medicine of the City University 34:409, 1973.

Publication 506), C. C. Gravatt, P. of New York, New York, NY.

D. LaFleur, and K. F. Heinrich

(eds.), Washington, DC: National

Measurement Laboratory,

National Bureau of Standards, Table 2-2. Principal lattice spacings of asbestiform minerals®*
1977 {issued 1978). JCPDS

13. A.L. Rickards, Estimation of Principal d-spacings (AJ Powder diffraction file
trace amounts of chrysotile Minerals and relative intensities number
asbestos by X-ray diffraction,

Anal. Chem., 44(11):1872-3, Chrysotile 737100 3.657 45750 21-543°
1972. 736100 36680 24565 25-645
14. fins Cook. P.L. Smith, and D. G. 710100 23380 36557 22-1162 (theoretical)
ilson, Amphibole fiber “Amosite” 8 33:00 30670 +=2 75670 17-745 (nonfibrous)
fora nationat and determination 8 22s00 30600 325% 27-1170 (UICC)
y Anthophyliite 3.08100 32460 8.265; 9-455
Table 2-1. The asbestos minerals and their 306109 833% 323s 16-401 (synthetic)
nonasbestiform analogs. Actinolite 272100 254100 340s 25-157
Asbestiform Nonasbestiform Crocidolite 8.35100 310s 272035 27-1415 (UICC)
Serpentine Tremolite 8 38100 3 1200 2 70500 13-497" isymhene
ee doar 706100 95 40 - synthetic,
Chrysotile Antigorite, lizardite 313100 27066 8444, 23-666 (synthetic
Amphibole mixture with richterite)

Anthophyllite asbestos — Anthophyllite "Thus information 1s intended as a guide, only Complete powder diffraction data,
Cummingtonite-grunerite | Cummingtonite- including mineral type and source, should be referred to, to ensure comparability

asbestos (“Amosite”) grunerite of sample and reference materials where possible Additional precisron XRD data
Crocidolite Riebeckite on amosite, crocidolite, tremolite, and chrysotile are available from the
Tremolite asbestos Tremolite wpe Bureau of Mines, Relerence &
Actinolite asbestos Actinolite orerence 3

“Fibrosity questionable
#¢U. S. GOVERNMENT PRINTING OFFICE: 1983/659 -095/0566


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

@ Data Output Accessories:

Strip Chart Recorder
Decade Scaler/Timer
Digital Printer

@ Sample Spinner (optional)

@ Instrument Calibration Reference
Specimen: a-quartz reference
crystal (Arkansas quartz standard,
#180-147-00, Philips Electronics
Instruments, Inc., 85 McKee Drive,
Mahwah, NJ 07430) or equivalent

2.6 Reagents

2.6.1 Standard Reference Materials

The reference materials listed below
are intended to serve as a guide. Every
attempt should be made to 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
Anthophyllite-Asbestos: UICC
Tremolite Asbestos: Wards Natural
Science Establishment, Rochester,
NY; Cyprus Research Standard,
Cyprus Research, 2435 Military
Ave., Los Angeles, CA 90064
{washed with dilute HCI to remove
small amount of calcite impurity);
Indian tremolite, Rajasthan State,
India.
e Actinolite Asbestos: (Source to

be determined).

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 Sampling

Samples for analysis of asbestos
content shall be collected as specified
in EPA Guidance Document #CO090,
Asbestos-Containing Materials in
School Buildings.’°

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.

@eoeoe

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 or 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 prepara-
tion 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
distribution, composition, and crystal-
linity, and to ensure sample representa-
tiveness and homogeneity for analysis.

2.7.2.1.1  Milling—Mechanical
milling of asbestos materials has been
shown to decrease fiber crystallinity,
with a resultant decrease in diffraction
intensity of the specimen; the degree
of lattice alteration is related to the
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 importance
and initial characterization of the
material with a minimum of matrix
reduction is often desirable to
document the composition of the
sample as received. Bulk samples of
very large particle size (>2-3 mm)
should be comminuted to ~100 um. A
mortar and pestle can sometimes be
used in size reduction of soft or loosely
bound materials though this may
cause matting of some samples. 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.

é

For accurate, reproducible quantita-
tive analysis, the‘particle size of both
sample and standard materials should
be reduced to ~10 ym (see Section
2.3.3). Dry ball milling at liquid
nitrogen temperatures (e.g., Spex
Freezer Mill, or equivalent) for a
maximum time of 10 min is
recommended to obtain satistactory
particle size distributions while
protecting the integrity of the crystal
lattice.® Bulk samples of very large
particle size may require grinding in
two stages for full matrix reduction to
<10 pm.2"6

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 shown by PLM to contain
large amounts of gypsum, cellulose, 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 temperatures between 550°C and
650°C, with subsequent
transformation to forsterite, 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

23,04

using the following procedure:
1.

Grind and mix the sample with a
mortar and pestle (or equivalent
method, see Section 2.7.2.1.1) toa
final particle size sufficiently small
(~100 um) to allow adequate
packing into the sample holder.

2. Pack sample into a standard bulk

sample holder. Care should be
taken to ensure that a representa-
tive portion of the milled sample is
selected for analysis. Particular
care should be taken to avoid
possible size segregation of the
sample. (Note: Use of a back-
packing method? for bulk sample


Table 1-1. Optical properties of asbestos fibers

Mineral Morphology, Refractive indices? Sign of

color’ a fringence Extinction elongation

Chrysotile Wavy fibers. Fiber bundles 1.493-1.560 1 517-1.5626 \ito fiber +
fasbestiform have splayed ends and “kinks”. {normally length (length slow)
serpentine) Aspect ratio typically >10.1 1.556)

Colorless}, nonpleochroic.

Amosite Straight, rigid fibers. 1.635-1.696 1.655-1.729° .020-.033 j\to fiber +
fasbestiform Aspect ratio typically >10 1 (normally fength (length slow)
grunerite} Colorless to brown, nonpleo- 1.696-1.710)

chroic or weakly so. Opaque
inclusions may be present.

Crocidolite Straight, rigid fibers. 1 654-1.701 1.668-1.7175 .014-.016 \\to fiber =
fasbestiform Thick fibers and bundles {normally length (length fast)
riebeckite) common, blue to purple-blue in close to 1.700)

color. Pleochroic. Birefringence
is generally masked by blue color.

Anthophyllite- Straight, single fibers, 1.596-1.652 1.615-1676° .019-.024 |\to fiber +
asbestos some larger composite length flengih slow)

fibers Anthrophyllite cleavage
fragments may be present with
aspect ratios < 10:1 4 Colorless
to light brown

Tremolite- Tremolite-asbestos may be 1,899-1.668 1.622-1.688° 023-.020 Oblique extinction, +
actinolite- present as single or composite 10-20° for {length slow)
asbestos fibers. Tremolite cleavage fragments.

fragments may be present as
single crystals with aspect ratios
<10:1.4 Colorless to pale green

Composite fibers
show \lextinction

\ From reference 5; colors cited are seen by observation 4 Fibers defined as having aspect ratio >3:1

with plane polarized light.
2 From references 5 and 8.
3 Fibers subjected to heating may be brownish.

Table 1-2. Central stop dispersron staining colors *

Mineral Riliqud we
Chrysoule 1.550"° Blue Blue-magenta
“Amosite” 1680 Blue-magenta Golden-yellow
to pale blue
1550"° Yellow to Yellow to white
white
Crocidolite’ 1700 Red magenta Blue-magenta
1.550"° Yellow to Yellow to white
white
Anthophyllite- 1.605"° Blue Gold to
asbestos gold-magenta
Tremolite- 1 605"°° Pale blue Yellow
asbestos
Actinolite- 1 605"° Gold-magenta Gold
asbestos to blue
1.630"°° Magenta Golden-yellow

54. to fiber length.
8 Ito fiber length.

"From reference 9, colors may vary slightly.
Blue absorption color.
“Oblique extinction view.


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 the pellet in 5 mL distilled
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 examine the residue.
Ashing should be performed in a low
temperature asher. Ashing may also
be performed in a muffle furnace at
temperatures of 500°C or lower.
Temperatures cf 550°C or higher will
cause dehydroxylation of the asbestos
minerals, resulting in changes 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 500°C

Ashing and acid treatment of
samples should not be used as
standard procedures. In order to
monitor possibse changes in fiber
characteristics, the material should be
viewed microscopically before and
after any sample preparation
procedure. Use of these procedures on
samples to be used for quantitation
requires a correction for percent
weight loss.
1.7.2.3 Fiber Identification

Positive identification of asbestos
requires the determination of the
following optical properties.
Morphology
Color and pleochroism
Refractive 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

ination procedure. Natural
variations in the conditions under
which deposits of asbestiform
minerals are formed will produce
exceptions to the published values and
differences from the UICC standards.
The sign of elongation is determined by
use of the compensator plate and
crossed polars. Refractive indices may
be determined by the Becke line test.
Alternatively, dispersion staining may
be used. Inexperienced operators may
find that the dispersion staining
technique ts more easily learned, and
should consult Reference 9 for
guidance. Central stop dispersion
staining colors are presented in Table

1-2. Available high-dispersion (HD)
liquids should be used.

1.7.2.4 Quantitation of Asbestos
Content

Asbestos quantitation is performed
by a point-counting procedure. An
ocular reticle (cross-hair or point array)
is used to visually superimpose a point
or points on the microscope field of
view. Record the number of points
positioned directly above each kind of
particle or fiber of interest. Score only
points directly over asbestos fibers or
nonasbestos matrix material. Do not
score empty points for the closest
particle. If an asbestos fiber and a
matrix particle overlap so that a point
is superimposed on therr visual
intersection, a point is scored for both
categories. Point counting provides a
determination of the area percent
asbestos. 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 this 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
nonasbestos matrix material must be
counted over at least eight different
preparations of representative
subsamples. Take eight forcep samples
and mount each separately 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. Count 50 nonempty points on
each preparation, using either
@ Across-hair reticle and mechanical

stage; or
e@ Areticle 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 the plane polarized
light path will allow simultaneous
discrimination of both particle types.
Quantitation should be performed at
100X or at the lowest magnification of
the polarized light microscope that can
effectively 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).

If a= 0, report “No asbestos
detected.” If O <a <3, report “<1%
asbestos.”

The value reported should be
rounded to the nearest percent.

1.8 References

4. 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, EPA-600/4-82-
021, U.S. Environmental
Protection Agency, in preparation.

5. U.S. Environmental Protection
Agency, Asbestos-Containing
Materials in School Buildings: A
Guidance Document, Parts 1 and
2, EPA/OTS No. CO0090, March
1979.

6. D. Lucas, T. Hartwell, and A. V.
Rao, Asbestos-Containing
Materials in School Buildings:
Guidance for Asbestos Analytical
Programs, EPA-560/13-80-017A,
U.S. Environmental Protection
Agency, December 1980.

7. D.H. Taylor and J. S. Bloom,
Hexametaphosphate pretreatment
of insulation samples for identifi-
cation of fibrous constituents,
Microscope, 28, 1980.

8. W. J. Campbell, R. L. Blake, L. L.
Brown, E. E. Cather, 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
1980.


examine the bulk insulation sample as

received.

@ Microscope: binocular, 10-45X
(approximate)

e@ Light Source: incandescent or
fluorescent

e@ 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

plate, 360° graduated rotating stage,

substage condenser, lamp, and amp

is.

@ 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 milli-
micron retardation

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 sample assessment.
®@ Ventilated Hood or negative
pressure glove box
Microscope Slides
Coverslips
Mortar and Pestle: agate or
porcelain (optional)
Wylie Mill (optional)
Beakers & assorted glassware
(optional)
Centrifuge (optional)
Filtration apparatus (optional)
Low temperature asher (optional)

.6 Reagents

6.1 Sample Preparation
Distilled Water (optional)
Dilute CHsCOOH: ACS reagent
grade (optional)

@ Dilute HCl: ACS reagent grade

(optional)
@ Sodium metaphosphate (NaPOs)s
(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

so

Pneumoconiosis 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 should
be 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 Gross Examination

Bulk samples of building materials
taken for the identification and
quantitation of asbestos are first
examined for homogeneity at low
magnification with the aid of a
stereomicroscope. The core sample
may be examined in its container or
carefully removed from the container
onto a glassine transfer paper or clean
glass plate. If possible, note is made of
the orientation of top and bottom
surfaces. When discrete strata are
identified, each is treated as a separate
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,

2

teased apart, covered with a cover
glass, and observed with the polarized
light microscope.

Alternatively, attempts may be made
to homogenize the sample or eliminate
interferences before further
characterization. The selection of
appropriate procedures 1s dependent
upon the samples encountered and
personal preference. The following are
presented as possible sample
preparation steps.

A mortar and pestle can scmetimes
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 ina
Wiley mill. Apparatus should be clean
and extreme care exercised to avoid
cross-contamination 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 vermiculite.
Grinding of amphiboles may result in
the separation of fiber bundles or the
production of cleavage fragments that
have aspect ratios greater than 3:1 and
will be classified as asbestos fibers.
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 micron 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
adhering to fiber surfaces may also be
removed by treatment with sodium
metaphosphate.” Add 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
tube. For approximately 15 seconds
each, stir the mixture on a vortex
mixer, place in an ultrasonic bat» and
then shake by hand. Repeat the series.