ASTM F1877-98(2003)e1
(Practice)Standard Practice for Characterization of Particles
Standard Practice for Characterization of Particles
SCOPE
1.1 This practice outlines a series of procedures for characterization of the morphology, number, size, and size distribution of particles. The methods utilized include sieves, optical, SEM, and electrooptical.
1.2 These methods are appropriate for particles produced by a number of different methods. These include wear test machines, total joint simulation systems, abrasion testing, methods for producing particulates, such as shatter boxes or pulverizors, commercially available particles, and particles harvested from tissues in animal or clinical studies.
1.3 The debris may include metallic, polymeric, ceramic, or any combination of these.
1.4 The digestion procedures to be used and issues of sterilization of retrieved particles are not the subject of this practice.
1.5 A classification scheme for description of particle morphology is included in Appendix X3.
1.6 As a precautionary measure, removed debris from implant tissues should be sterilized or minimally disinfected by an appropriate means that does not adversely affect the particulate material. This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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Designation: F 1877 – 98 (Reapproved 2003)
Standard Practice for
Characterization of Particles
This standard is issued under the fixed designation F 1877; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
e NOTE—Editorial changes were made throughout in April 2003.
1. Scope E 1617 Practice for Reporting Particle Size Characteriza-
tion Data
1.1 This practice outlines a series of procedures for charac-
E 766 Practice for Calibrating the Magnification of Scan-
terization of the morphology, number, size, and size distribu-
ning Electron Microscopes
tion of particles. The methods utilized include sieves, optical,
F 561 Practice for Retrieval and Analysis of Implanted
SEM, and electrooptical.
Medical Devices, and Associated Tissues
1.2 Thesemethodsareappropriateforparticlesproducedby
F 660 Practice for Comparing Particle Size in the Use of
a number of different methods. These include wear test
Alternative Types of Particle Counters
machines, total joint simulation systems, abrasion testing,
F 661 Practice for Particle Count and Size Distribution
methods for producing particulates, such as shatter boxes or
MeasurementinBatchSamplesforFilterEvaluationUsing
pulverizors, commercially available particles, and particles
an Optical Particle Counter
harvested from tissues in animal or clinical studies.
F 662 Method for Particle Count and Size Distribution in
1.3 The debris may include metallic, polymeric, ceramic, or
Batch Samples for Filter Evaluation Using an Electrical
any combination of these.
Resistance Particle Counter
1.4 The digestion procedures to be used and issues of
F 732 Test Method forWearTesting of Polymeric Materials
sterilization of retrieved particles are not the subject of this
for Use in Total Joint Prostheses
practice.
F 1714 Guide for Gravimetric Wear Assessment of Pros-
1.5 A classification scheme for description of particle mor-
thetic Hip Designs in Simulator Devices
phology is included in Appendix X3.
F 1715 Guide for Wear Assessment of Prosthetic Knee
1.6 As a precautionary measure, removed debris from
Designs in Simulator Devices
implanttissuesshouldbesterilizedorminimallydisinfectedby
an appropriate means that does not adversely affect the
3. Terminology
particulate material. This standard does not purport to address
3.1 Definitions of Terms Specific to This Standard:
all of the safety concerns, if any, associated with its use. It is
3.1.1 agglomerate, n—amassformedbythecementationof
the responsibility of the user of this standard to establish
individual particles, probably by chemical forces.
appropriate safety and health practices and determine the
3.1.2 aggregate, n—a mass formed of mixtures of particu-
applicability of regulatory limitations prior to use.
late and agglomerate particles having a binding force interme-
2. Referenced Documents diate between agglomerates and flocculates. Formation of
aggregates can occur after sampling if the samples are improp-
2.1 ASTM Standards:
erly kept or treated.
C 678 Test Methods for Particle Size Distribution of Alu-
3.1.3 aspect ratio (AR), n—a ratio of the major to the minor
mina or Quartz by Electric Sensing Technique
diameter of a particle, which can be used when the major axis
E 11 Specification for Wire Cloth and Sieves for Testing
does not cross a particle outline (see 11.3.3).
Purposes
3.1.4 elongation (E), n—ratio of the particle length to the
E 161 Specification for Precision Electroformed Sieves
average particle width (see 11.3.4).
3.1.5 equivalentcirclediameter(ECD),n—ameasureofthe
size of a particle (see 11.3.2 and Appendix X1).
ThispracticeisunderthejurisdictionofASTMCommitteeF04onMedicaland
Surgical Materials and Devices and is the direct responsibility of Subcommittee
F04.16 on Biocompatibility Test Methods.
Current edition approved Apr. 10, 2003. Published May 2003. Originally Annual Book of ASTM Standards, Vol 03.01.
approved in 1998. Last previous edition approved in 1998 as F 1877 – 98. Annual Book of ASTM Standards, Vol 13.01.
2 6
Discontinued; See 1995 Annual Book of ASTM Standards, Vol 15.02. Annual Book of ASTM Standards, Vol 11.01.
3 7
Annual Book of ASTM Standards, Vol 14.02. Discontinued; See 2001 Annual Book of ASTM Standards, Vol 14.04.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
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F 1877 – 98 (2003)
3.1.6 Feret diameter, n—the mean value of the distance 5.3 The morphology of particles produced in laboratory
between pairs of parallel tangents to a projected outline of a tests of wear and abrasion often is affected by the test
particle. conditions, such as the magnitude and rate of load application,
3.1.7 flocculate, n—a group of two or more attached par- device configuration, and test environment. Comparison of the
ticles held together by physical forces, such as surface tension, morphology and size of particles produced in vitro with those
adsorption, or similar forces. produced in vivo will provide valuable information regarding
the degree to which the method simulates the in vivo condition
3.1.8 form factor (FF), n—a dimensionless number relating
area and perimeter of a particle, as determined in 11.3.6. being modeled.
3.1.9 irregular, adj—a particle that cannot be described as
6. Interferences
round or spherical. A set of standard nomenclature and refer-
6.1 Particles may form aggregates or agglomerates during
ence figures are given in Appendix X2.
preparation and storage. These would result in an increase in
3.1.10 particle, n—the smallest discrete unit detectable as
measured particle size and decrease in particle number. It is
determined in test methods.
essential that care be taken to resuspend particles prior to
3.1.11 particle breadth, n—distance between touch points
analysis and to note any effects of the dispersant used.
of the shortest Feret pair, orthogonal to length.
6.2 Debris from wear tests or harvested from tissues may
3.1.12 particle length, n—distance between touch points of
containamixtureofmaterials.Careshouldbetakentoseparate
maximum Feret pair.This value will be greater than or equal to
the particles and methods utilized to determine the chemical
the maximum Feret diameter.
composition of the particles.
3.1.13 rectangular, adj—a particle that approximates a
6.3 Many automated particle counters operate on the as-
square or rectangle in shape.
sumption that the particles are spherical. These methods may
3.1.14 roundness (R), n—a measure of how closely an
not be appropriate for nonspherical debris.Additional methods
object represents a circle as determined in 11.3.5.
should be used to verify size using methods that take aspect
3.1.15 spherical, adj—a particle with a generally spherical
ratio into consideration, for example, SEM image analysis.
shape that appears round in a photograph.
7. Apparatus
4. Summary of Practice
7.1 Scanning Electron Microscope (SEM):
4.1 Particles produced by implant wear in vivo in animal or
7.1.1 Standard SEM equipment can be utilized for many
clinical studies are harvested from tissues after digestion
studies. In special instances, such as with polymeric particles,
utilizing methods, such as those in Practice F 561. Particles
a low acceleration voltage (1-2 kV) machine with a high
generated in vitro, or obtained from commercial sources, are
brightness electron source, such as a field emission tip, may be
used as received, or after digestion, if they were generated in
utilized.
protein solutions, and further separation if there are signs of
7.1.2 Elemental analysis may be accomplished with an
aggregation. A two level analysis is provided. For routine
energy dispersive spectrometer (EDS) for energy dispersive
analysis, the particles are characterized by the terms of
X-ray analysis (EDXA).
morphology and by size using Feret diameters. For more
7.2 Optical Microscope—An optical microscope operating
detailed studies, several methods are described that may be
in the transmission mode may be utilized. Dark field illumina-
utilized for numerically characterizing their dimensions, size
tion may enhance visualization of some particles. Polarized
distribution, and number.
light will facilitate identification of semicrystalline polymeric
materials.
5. Significance and Use
7.3 Automatic Particle Counters (see Practice F 660):
5.1 Thebiologicalresponsetomaterialsintheformofsmall
7.3.1 Image Analyzer—This instrument counts particles by
particles, as from wear debris, often is significantly different
size as those particles lie on a microscope slide.
from that to the same materials as larger implant components.
7.3.2 Optical Counter—This instrument measures the area
The size and shape (morphology) of the particles may have a
of a shadow cast by a particle as it passes a window. From this
major effect on the biological response; therefore, this practice
area the instrument reports the diameter of a circle of equal
provides a standardized nomenclature for describing particles.
area (see Practice F 661).
Such a unified nomenclature will be of value in interpretation
7.3.3 Electrical Resistance Counter—This instrument mea-
of biological tests of responses to particles, in that it will
sures the volume of an individual particle. From that volume
facilitate separation of biological responses associated with
theinstrumentreportsthediameterofasphereofequalvolume
shape from those associated with the chemical composition of
(see Method F 662).
debris.
8. Reagents
5.2 The quantity, size, and morphology of particles released
as wear debris from implants in vivo may produce an adverse 8.1 Particle-Free (0.2 µm Filtered) Deionized Water, for
biological response which will affect the long term survival of nonpolymeric particles.
the device. Characterization of such debris will provide valu- 8.2 Particle-Free (0.2 µm Filtered) Methanol or Ethanol,
able information regarding the effectiveness of device designs for polymeric or mixed debris.
or methods of processing components and the mechanisms of 8.3 Ultra-Cleaning Reagent,forapparatusorlabwareclean-
wear. ing.
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F 1877 – 98 (2003)
TABLE 1 Recommended Magnifications for Particle Imaging
11.3.3 The Aspect Ratio (AR) is a Common Measure of
Magnification Particle Size Range (µm) Shape:
10000 0.1 to 1.0 11.3.3.1 The AR is the ratio of the major diameter (d )to
max
1000 1 to 10
the minor diameter (d ). The major diameter is the longest
min
100 10 to 100
straight line that can be drawn between any two points on the
outline.The minor diameter is the longest line perpendicular to
the major diameter:
9. Specimen Preparation
AR 5 d /d (2)
max min
9.1 Specimens from explanted tissues from animal or clini-
11.3.4 The elongation (E), is similar to the AR except it is
cal studies may need to be harvested and digested using
more suited for the measurement of much longer particles,
methods, such as those described in Practice F 561.
especially fibrilar particles, where the major axis line does not
9.2 Particles from in vitro cell culture tests also may need to
stay within the particle boundaries. Refer to particle types A
be digested and harvested.
and C in Appendix X1.
9.3 Centrifugation of particles from wear may be consid-
11.3.4.1 The E is the ratio of the length (FL) to the breadth
ered, if necessary, at 400 g for 10 min, and resuspended in
(FW):
water or methanol. Resuspended particles may be filtered in
E 5 FL/FW (3)
accordance with Practice F 561 prior to examination by SEM.
11.3.5 The roundness (R) is a measure of how closely a
10. Particle Imaging by Light or Scanning Electron
particle resembles a circle. The R varies from zero to one in
Microscopy
magnitude with a perfect circle having a value of one.
10.1 Images may either be captured electronically or pho- 2
R 5 ~4A!/~p d ! (4)
max
tographically for subsequent analysis.
10.2 For the characterization and measurements to be accu- where:
A = area, and
rate, it is essential that the particles be imaged at the largest
d = the maximum diameter.
magnification as possible. The magnifications in Table 1 are max
recommended. 11.3.6 The form factor (FF) is similar to R but is based on
10.3 For particle size distribution measurements, divide the perimeter (p) of the particle outline rather than the major
each of the size ranges specified in Table 1, into 10 bins. diameter. The FF is more sensitive to the variations in
roughness of the particle outline.
11. Particle Characterization
FF 5 4pA/p (5)
11.1 Particle Shape (Morphology)—Refer to the photo-
where:
graphs and classify the morphology of the particles using the
p = perimeter of the particle outline.
nomenclature in Appendix X2.
11.2 Routine Particle Size Determination Using Feret Di- 11.4 Other Particles Size Determination Methods:
ameters:
11.4.1 Particles larger than 20 µm may be determined by
11.2.1 The use of multiple Feret diameters especially is
sieves described in Specifications E 11 and E 161.
useful for spherical and rectangular particles.
11.4.2 Particles in liquid suspension may be sized as di-
11.2.2 Determine the particle size and aspect ratio as the
rected in Practice F 661 or Method F 662.
mean of two Feret diameters.
11.2.3 Calculate the particle size distribution based on the
12. Elemental Analysis
volume of solution used and the size of the filters.
12.1 SEM-EDS analysis should be conducted at a magnifi-
11.3 Detailed Particle Shape Analysis for Irregular Shaped
cation suggested in 10.2.
Particles:
12.2 Elemental analysis should be conducted for at least 10
11.3.1 Fiveparticledimensionalmeasurementsareprovided
s for each particle. Since detailed compositional analysis is of
using examples shown in Appendix X1. One is a measure of
questionable meaning for micron and submicron sized par-
particle size while the other four are shape descriptors.
ticles,itisrecommendedthatcompositionbedeterminedbased
11.3.2 The Equivalent Circle Diameter (ECD) as a Measure
on identification of key elemental peaks for the major elements
of Particle Size:
likely to be present in the sample.
11.3.2.1 The ECD is defined as the diameter of a circle with
an area equivalent to the area (A) of the particle and has the
13. Report
units of length:
13.1 Report the following information:
ECD5~4*A/p!2 (1)
13.1.1 The source of the particles and materials and meth-
ods for generation.
13.1.2 Methods utilized to digest and separate the particles.
The examples provided were analyzed with the NIH Image Program by Landry
13.1.3 Morphological description of the particles.
a
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