ASTM F1877-98
(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 are 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.
General Information
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Standards Content (Sample)
NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
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Designation: F 1877 – 98
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.
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 (SEMs)
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 These methods are appropriate for particles produced by
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
Measurement in Batch Samples for Filter Evaluation Using
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 690 Particle Size Distribution of Alumina or Quartz by
sterilization of retrieved particles are not the subject of this
Electric Sensing Technique
practice.
F 732 Practice for Reciprocating Pin-on-Flat Evaluation of
1.5 A classification scheme for description of particle mor-
Friction and Wear Properties of Polymeric Materials for
phology are included in Appendix X3.
Use in Total Joint Prostheses
1.6 As a precautionary measure, removed debris from
F 1714 Guide for Gravimetric Wear Assessment of Pros-
implant tissues should be sterilized or minimally disinfected by
thetic Hip Designs in Simulator Devices
an appropriate means that does not adversely affect the
F 1715 Guide for Gravimetric Wear Assessment of Pros-
particulate material. This standard does not purport to address
thetic Knee Designs in Simulator Devices
all of the safety concerns, if any, associated with its use. It is
the responsibility of the user of this standard to establish
3. Terminology
appropriate safety and health practices and determine the
3.1 Definitions of Terms Specific to This Standard:
applicability of regulatory limitations prior to use.
3.1.1 agglomerate, n—a mass formed by the cementation of
2. Referenced Documents individual particles, probably by chemical forces.
3.1.2 aggregate, n—a mass formed of mixtures of particu-
2.1 ASTM Standards:
late and agglomerate particles having a binding force interme-
E 11 Specification for Wire-Cloth Sieves for Testing Pur-
2 diate between agglomerates and flocculates. Formation of
poses
aggregates can occur after sampling if the samples are improp-
E 20 Practice for Particle Size Analysis of Particulate Sub-
erly kept or treated.
stances in the Range of 0.2 to 75 μm by Optical Micros-
3.1.3 aspect ratio (AR), n—a ratio of the major to the minor
copy
diameter of a particle, which can be used when the major axis
E 161 Specification for Precision Electroformed Sieves
does not cross a particle outline (see 11.3.3).
(Square Opening Series)
3.1.4 elongation (E), n—ratio of the particle length to the
average particle width (see 11.3.4).
3.1.5 equivalent circle diameter (ECD), n—a measure of the
This practice is under the jurisdiction of ASTM Committee F04 on Medical and
size of a particle (see 11.3.2 and Appendix X1).
Surgical Materials and Devices and is the direct responsibility of Subcommittee
3.1.6 Feret diameter, n—the mean value of the distance
F04.16 on Biocompatibility.
Current edition approved April 10, 1998. Published March 1999.
Annual Book of ASTM Standards, Vol 14.02.
3 4
Discontinued 1994—Vol 14.02. Annual Book of ASTM Standards, Vol 13.01.
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NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
F 1877
between pairs of parallel tangents to a projected outline of a conditions, such as the magnitude and rate of load application,
particle. device configuration, and test environment. Comparison of the
3.1.7 flocculate, n—a group of two or more attached par- morphology and size of particles produced in vitro with those
ticles held together by physical forces, such as surface tension, produced in vivo will provide valuable information regarding
adsorption, or similar forces. the degree to which the method simulates the in vivo condition
3.1.8 form factor (FF), n—a dimensionless number relating being modeled.
area and perimeter of a particle, as directed in 11.3.6.
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
contain a mixture of materials. Care should be taken to separate
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
generated in vitro, or obtained from commercial sources, are a low acceleration voltage (1-2 kV) machine with a high
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
aggregation. A two level analysis is provided. For routine 7.1.2 Elemental analysis may be accomplished with an
analysis, the particles are characterized by the terms of energy dispersive spectrometer (EDS) for energy dispersive
morphology and by size using Feret diameters. For more X-ray analysis (EDXA).
detailed studies, several methods are described that may be
7.2 Optical Microscope—An optical microscope operating
utilized for numerically characterizing their dimensions, size
in the transmission mode may be utilized. Dark field illumina-
distribution, and number.
tion may enhance visualization of some particles. Polarized
light will facilitate identification of semicrystalline polymeric
5. Significance and Use
materials.
5.1 The biological response to materials in the form of small
7.3 Automatic Particle Counters (see Practice F 660):
particles, as from wear debris, often is different significantly
7.3.1 Image Analyzer—This instrument counts particles by
from that to the same materials as larger implant components.
size as those particles lie on a microscope slide.
The size and shape (morphology) of the particles may have a
7.3.2 Optical Counter—This instrument measures the area
major effect on the biological response; therefore, this practice
of a shadow cast by a particle as it passes a window. From this
provides a standardized nomenclature for describing particles.
area the instrument reports the diameter of a circle of equal
Such a unified nomenclature will be of value in interpretation
area (see Practice F 661).
of biological tests of responses to particles, in that it will
7.3.3 Electrical Resistance Counter—This instrument mea-
facilitate separation of biological responses associated with
sures the volume of an individual particle. From that volume
shape from those associated with the chemical composition of
the instrument reports the diameter of a sphere of equal volume
debris.
(see Method F 662).
5.2 The quantity, size, and morphology of particles released
as wear debris from implants in vivo may produce an adverse
8. Reagents
biological response which will affect the long term survival of
8.1 Particle-Free (0.2 μm Filtered) Deionized Water, for
the device. Characterization of such debris will provide valu-
nonpolymeric particles.
able information regarding the effectiveness of device designs
8.2 Particle-Free (0.2 μm Filtered) Methanol or Ethanol,
or methods of processing components and the mechanisms of
for polymeric or mixed debris.
wear.
5.3 The morphology of particles produced in laboratory 8.3 Ultra-Cleaning Reagent, for apparatus or labware clean-
tests of wear and abrasion often is affected by the test ing.
NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
F 1877
9. Specimen Preparation 11.3.3.1 The AR is the ratio of the major diameter (d )to
max
the minor diameter (d ). The major diameter is the longest
9.1 Specimens from explanted tissues from animal or clini- min
straight line that can be drawn between any two points on the
cal studies may need to be harvested and digested using
outline. The minor diameter is the longest line perpendicular to
methods, such as those described in Practice F 561.
the major diameter:
9.2 Particles from in vitro cell culture tests also may need to
be digested and harvested. AR 5 d /d (2)
max min
9.3 Particles from wear tests should be centrifuged at atleast
11.3.4 The elongation (E), is similar to the AR except it is
400 g for 10 min, and resuspended in water or methanol.
more suited for the measurement of much longer particles,
Resuspended particles may be filtered in accordance with
especially fibrilar particles, where the major axis line does not
Practice F 561 prior to examination by SEM.
stay within the particle boundaries. Refer to particle types A
and C in Appendix X1.
10. Particle Imaging by Light or Scanning Electron
11.3.4.1 The E is the ratio of the length (FL) to the breadth
Microscopy
(FW):
10.1 Images may either be captured electronically or pho-
E 5 FL/FW (3)
tographically for subsequent analysis.
10.2 For the characterization and measurements to be accu- 11.3.5 The roundness (R) is a measure of how closely a
particle resembles a circle. The R varies from zero to one in
rate, it is essential that the particles be imaged at the largest
magnification as possible. The magnifications in Table 1 are magnitude with a perfect circle having a value of one.
recommended. 2
R 5 ~4A!/~p d ! (4)
max
10.3 For particle size distribution measurements, divide
each of the size ranges specified in Table 1, into 10 bins. where:
A = area, and
11. Particle Characterization
d = the maximum diameter.
max
11.1 Particle Shape (Morphology)—Refer to the photo- 11.3.6 The form factor (FF) is similar to R but is based on
graphs and classify the morphology of the particles using the
the perimeter (p) of the particle outline rather than the major
nomenclature in Appendix X2. diameter. The FF is more sensitive to the variations in
11.2 Routine Particle Size Determination Using Feret Di- roughness of the particle outline.
ameters:
FF 5 4pA/p (5)
11.2.1 The use of multiple Feret diameters especially is
useful for spherical and rectangular particles.
where:
11.2.2 Determine the particle size and aspect ratio as the
p = perimeter of the particle outline.
mean of two Feret diameters. 11.4 Other Particles Size Determination Methods:
11.2.3 Calculate the particle size distribution based on the
11.4.1 Particles larger than 20 μm may be determined by
volume of solution used and the size of the filters. sieves described in Specifications E 11 and E 161.
11.3 Detailed Particle Shape Analysis for Irregular Shaped
11.4.2 Particles in liquid suspension may be sized as di-
Particles: rected in Practice F 661 or Method F 662.
11.3.1 Five particle dimensional measurements are provided
using examples shown in Appendix X1. One is a measure of 12. Elemental Analysis
particle size while the other four are shape descriptors.
12.1 SEM-EDS analysis should be conducted at a magnifi-
11.3.2 The Equivalent Circle Diameter (ECD) as a Measure
cation suggested in 10.2.
of Particle Size:
12.2 Elemental analysis should be conducted for at least 10
11.3.2.1 The ECD is defined as the diameter of a circle with
s for each particle. Since detailed compositional analysis is of
an area equivalent to the area (A) of the particle and has the
questionable meaning for micron and submicron sized par-
units of length:
ticles, it is recommended that composition be determined based
on identification of key elemental peaks for the major elements
ECD5~4*A/p! (1)
likely to be present in the sample.
11.3.3 The Aspect Ratio (AR) is a Common Measure of
Shape:
13. Report
13.1 Report the following information:
13.1.1 The source of the particles and materials and meth-
The examples provided were analyzed with the NIH Image Program by Landry
and Agarwal. A set of macros is available from t
...
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