ASTM E2864-18(2022)

Standard Test Method for Measurement of Airborne Metal Oxide Nanoparticle Surface Area Concentration in Inhalation Exposure Chambers using Krypton Gas Adsorption

SIGNIFICANCE AND USE
5.1 A tiered strategy for characterization of nanoparticle properties is necessary to draw meaningful conclusions concerning dose-response relationships observed during inhalation toxicology experiments. This tiered strategy includes characterization of nanoparticles as produced (that is, measured as the bulk material sold by the supplier) and as administered (that is, measured at the point of delivery to a test subject) (Oberdorster et al. (6)).  
5.2 Test Methods B922 and C1274 and ISO 9277 and ISO 18757 exist for determination of the as produced surface area of bulk metal and metal oxide powders. During the delivery of nanoparticles in inhalation exposure chambers, the material properties may undergo change and therefore have properties that differ from the material as produced. This test method describes the determination of the as administered surface area of airborne metal oxide nanoparticles in inhalation exposure chambers for inhalation toxicology studies.
SCOPE
1.1 This test method covers determination of surface area of airborne metal oxide nanoparticles in inhalation exposure chambers for inhalation toxicology studies. Surface area may be measured by gas adsorption methods using adsorbates such as nitrogen, krypton, and argon (Brunauer et al. (1),2 Anderson (2), Gregg and Sing (3)) or by ion attachment and mobility-based methods (Ku and Maynard (4)). This test method is specific to the measurement of surface area by gas adsorption by krypton gas adsorption. The test method permits the use of any modern commercial krypton adsorption instruments but strictly defines the sample collection, outgassing, and analysis procedures for metal and metal oxide nanoparticles. Use of krypton is required due to the low overall surface area of particle-laden samples and the need to accurately measure the background surface area of the filter used for sample collection. Instrument-reported values of surface area based on the multipoint Brunauer, Emmett and Teller (BET) equation (Brunauer et al. (1), Anderson (2), Gregg and Sing (3)) are used to calculate surface area of airborne nanoparticles collected on a filter.  
1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard. State all numerical values in terms of SI units unless specific instrumentation software reports surface area using alternate units.  
1.3 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.4 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

General Information

• Status: Published
• Publication Date: 14-Nov-2022
• ICS: 07.120 - Nanotechnologies
• ICS: 49.025.05 - Ferrous alloys in general
• Technical Committee: E56 - Nanotechnology
• Drafting Committee: E56.02 - Physical and Chemical Characterization

Relations

• Refers: ASTM C1274-12(2020) - Standard Test Method for Advanced Ceramic Specific Surface Area by Physical Adsorption
• Effective Date: 01-Apr-2020
• Refers: ASTM B922-17 - Standard Test Method for Metal Powder Specific Surface Area by Physical Adsorption
• Effective Date: 01-Jan-2017
• Refers: ASTM E691-13 - Standard Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
• Effective Date: 01-May-2013
• Refers: ASTM C1274-12 - Standard Test Method for Advanced Ceramic Specific Surface Area by Physical Adsorption
• Effective Date: 01-Aug-2012
• Refers: ASTM E691-11 - Standard Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
• Effective Date: 01-Nov-2011
• Refers: ASTM C1274-10 - Standard Test Method for Advanced Ceramic Specific Surface Area by Physical Adsorption
• Effective Date: 01-Dec-2010
• Refers: ASTM B922-10 - Standard Test Method for Metal Powder Specific Surface Area by Physical Adsorption
• Effective Date: 01-May-2010
• Refers: ASTM E691-08 - Standard Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
• Effective Date: 01-Oct-2008
• Refers: ASTM B922-02(2008) - Standard Test Method for Metal Powder Specific Surface Area by Physical Adsorption
• Effective Date: 01-Apr-2008
• Refers: ASTM E2456-06 - Standard Terminology Relating to Nanotechnology
• Effective Date: 01-Oct-2006
• Refers: ASTM C1274-00(2006) - Standard Test Method for Advanced Ceramic Specific Surface Area by Physical Adsorption
• Effective Date: 01-Jan-2006
• Refers: ASTM E691-05 - Standard Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
• Effective Date: 01-Nov-2005
• Refers: ASTM B922-02 - Standard Test Method for Metal Powder Specific Surface Area by Physical Adsorption
• Effective Date: 10-Oct-2002
• Refers: ASTM C1274-00 - Standard Test Method for Advanced Ceramic Specific Surface Area by Physical Adsorption
• Effective Date: 10-Dec-2000
• Refers: ASTM E691-99 - Standard Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
• Effective Date: 10-May-1999

Overview

ASTM E2864-18(2022) is an international standard test method developed by ASTM for the measurement of airborne metal oxide nanoparticle surface area concentration in inhalation exposure chambers using krypton gas adsorption. This standard method is crucial for inhalation exposure studies, particularly those related to toxicology, where understanding the properties of nanoparticles as delivered is essential for accurate dose-response assessments. The procedure precisely defines collection, outgassing, and analysis techniques, addressing the unique challenges associated with measuring the surface area of nanoparticles in the air using krypton gas due to their typically low total surface area.

Key Topics

• Characterization of Nanoparticles: The standard supports a tiered approach, requiring characterization of nanoparticles in both bulk (as produced) and airborne (as administered) forms to ensure accurate health and toxicology evaluations.
• Krypton Gas Adsorption: The method focuses on using krypton for surface area measurements due to its sensitivity in detecting low levels of particulate matter collected on filters.
• Filter Handling and Analysis: Strict procedures are outlined for sample collection, filter preparation, outgassing, and final surface area measurement to ensure precise and repeatable results.
• BET Methodology: Surface area calculations are based on the multipoint Brunauer, Emmett and Teller (BET) equation, widely accepted in gas adsorption analysis.
• Sample and Instrumentation Requirements: The test utilizes modern, commercial krypton adsorption instruments, analytical balances with high sensitivity, and specific filters, ensuring reliability and reproducibility.

Applications

ASTM E2864-18(2022) has a range of practical applications, especially in fields where airborne nanoparticle analysis is required:

• Inhalation Toxicology Studies: The method is directly applicable to laboratories conducting inhalation experiments to determine accurate nanoparticle dose-response relationships, supporting occupational health and environmental safety research.
• Nanomaterial Risk Assessment: Enables researchers and manufacturers to assess the as-administered properties of nanoparticles, which may differ from their form as produced, aiding in regulatory compliance and product safety evaluations.
• Quality Assurance and Research: Laboratories can use this standard for interlaboratory comparisons, calibration, and ensuring the consistency and accuracy of surface area measurements of airborne metal oxide nanoparticles.
• Exposure Chamber Monitoring: Provides a reliable technique for monitoring and quantifying nanoparticle concentrations during exposure studies, supporting risk assessment in workplace and environmental applications.

Related Standards

For comprehensive characterization and measurement of nanoparticle surface area and properties, ASTM E2864-18(2022) should be considered alongside these related international and ASTM standards:

• ASTM B922: Test Method for Metal Powder Specific Surface Area by Physical Adsorption
• ASTM C1274: Test Method for Advanced Ceramic Specific Surface Area by Physical Adsorption
• ASTM E691: Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
• ASTM E2456: Terminology Relating to Nanotechnology
• ISO 9277: Determination of the Specific Surface Area of Solids by Gas Adsorption using the BET Method
• ISO 18757: Fine Ceramics – Determination of Specific Surface Area of Ceramic Powders by Gas Adsorption

Summary

ASTM E2864-18(2022) provides a standardized, reliable method for accurately measuring the surface area concentration of airborne metal oxide nanoparticles in inhalation exposure chambers using krypton gas adsorption. This facilitates meaningful toxicological studies, regulatory compliance, and risk assessment in occupational and environmental settings. Leveraging krypton gas adsorption and robust handling protocols, the standard ensures the integrity and accuracy of nanoparticle surface area measurements, which are essential for supporting health and safety in nanotechnology applications.

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: E2864 − 18 (Reapproved 2022)
Standard Test Method for
Measurement of Airborne Metal Oxide Nanoparticle Surface
Area Concentration in Inhalation Exposure Chambers using
Krypton Gas Adsorption
This standard is issued under the fixed designation E2864; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope ization established in the Decision on Principles for the
Development of International Standards, Guides and Recom-
1.1 Thistestmethodcoversdeterminationofsurfaceareaof
mendations issued by the World Trade Organization Technical
airborne metal oxide nanoparticles in inhalation exposure
Barriers to Trade (TBT) Committee.
chambers for inhalation toxicology studies. Surface area may
be measured by gas adsorption methods using adsorbates such
2. Referenced Documents
as nitrogen, krypton, and argon (Brunauer et al. (1), Anderson
(2), Gregg and Sing (3)) or by ion attachment and mobility- 2.1 ASTM Standards:
based methods (Ku and Maynard (4)). This test method is B922Test Method for Metal Powder Specific Surface Area
specific to the measurement of surface area by gas adsorption by Physical Adsorption
by krypton gas adsorption. The test method permits the use of C1274Test Method forAdvanced Ceramic Specific Surface
any modern commercial krypton adsorption instruments but Area by Physical Adsorption
strictly defines the sample collection, outgassing, and analysis E691Practice for Conducting an Interlaboratory Study to
procedures for metal and metal oxide nanoparticles. Use of Determine the Precision of a Test Method
krypton is required due to the low overall surface area of E2456Terminology Relating to Nanotechnology
particle-laden samples and the need to accurately measure the
2.2 ISO Standards:
background surface area of the filter used for sample collec-
ISO 9277Determination of the Specific Surface Area of
tion. Instrument-reported values of surface area based on the
Solids by Gas Adsorption using the BET Method
multipoint Brunauer, Emmett and Teller (BET) equation
ISO 18757Fine Ceramics (Advanced Ceramics, Advanced
(Brunaueretal. (1),Anderson (2),GreggandSing (3))areused
Technical Ceramics)—Determination of Specific surface
to calculate surface area of airborne nanoparticles collected on
Area of Ceramic Powders by Gas Adsorption using the
a filter.
BET Method
1.2 The values stated in SI units are to be regarded as
standard. No other units of measurement are included in this 3. Terminology
standard. State all numerical values in terms of SI units unless
3.1 Definitions—For additional definitions related to
specific instrumentation software reports surface area using
nanotechnology, see Terminology E2456.
alternate units.
3.1.1 nanoparticles, n—in nanotechnology, a sub-
1.3 This standard does not purport to address all of the
classification of ultrafine particle with lengths in two or three
safety concerns, if any, associated with its use. It is the
dimensions greater than 0.001 micrometre (1 nanometre) and
responsibility of the user of this standard to establish appro-
smallerthanabout0.1micrometre(100nanometres)andwhich
priate safety, health, and environmental practices and deter-
may or may not exhibit a size-related intensive property.
mine the applicability of regulatory limitations prior to use.
E2456
1.4 This international standard was developed in accor-
3.1.2 adsorbate, n—material that has been retained by the
dance with internationally recognized principles on standard-
process of adsorption. B922
This test method is under the jurisdiction of ASTM Committee E56 on
Nanotechnology and is the direct responsibility of Subcommittee E56.02 on
Physical and Chemical Characterization. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved Nov. 15, 2022. Published November 2022. Originally contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
approved in 2013. Last previous edition approved in 2018 as E2864 – 18. DOI: Standards volume information, refer to the standard’s Document Summary page on
10.1520/E2864-18R22. the ASTM website.
Theboldfacenumbersinparenthesesrefertothelistofreferencesattheendof Available fromAmerican National Standards Institute (ANSI), 25 W. 43rd St.,
this standard. 4th Floor, New York, NY 10036, http://www.ansi.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E2864 − 18 (2022)
3.1.3 adsorbent, n—any solid having the ability to concen- the total amount of gas adsorbed onto the sample under
trate or collect significant quantities of other substances on its analysis. The sample mass is then used to normalize the
surface. B922 measuredadsorptionresults.Anyerrorinthesamplemasswill
affect the final BET surface area.
3.1.4 adsorption, n—a process in which fluid molecules are
concentrated or collected on a surface by chemical or physical
4.4 CalculationsarebasedontheBETequation,asrequired
forces, or both. B922
by the instrument being used for the determination. The
instrument pressure tolerance (pressure range that must be
3.1.5 BET-constant, n—an indication of the magnitude of
maintained within a sample cell to accept a valid data point) is
the adsorbent/adsorbate interactions in the first adsorbed layer.
6.6Pa.Inthisstandard,thecross-sectionalareaforthekrypton
3.1.6 outgassing, n—the evolution of gas from a material in
-19 2
adsorbate is taken to be 2.02 × 10 m (ISO 9277); however,
a vacuum or inert gas flow, at or above ambient temperature.
someinstrumentsoftwaremayuseadifferentdefaultvalue.As
B922
such, the cross-sectional area of the krypton adsorbate used in
3.1.7 physical adsorption (van der Waals adsorption),
calculations should be reported with the BET surface area
n—the binding of an adsorbate to the surface of a solid by
results.
forceswhoseenergylevelsapproximatethoseofcondensation.
B922 5. Significance and Use
3.1.8 surface area, n—the total area of the surface of a
5.1 A tiered strategy for characterization of nanoparticle
powder or solid including both external and accessible internal
properties is necessary to draw meaningful conclusions con-
surfaces (from voids, cracks, open porosity, and fissures); the
cerningdose-responserelationshipsobservedduringinhalation
area may be calculated by the BET equation from gas adsorp-
toxicology experiments. This tiered strategy includes charac-
tion data obtained under specific conditions; it is useful to
terizationofnanoparticlesasproduced(thatis,measuredasthe
express this value as the specific surface area, for example,
bulkmaterialsoldbythesupplier)and as administered(thatis,
surface area per unit mass of sample (m /kg). B922
measuredatthepointofdeliverytoatestsubject)(Oberdorster
et al. (6)).
3.1.9 surface area (BET), n—thetotalsurfaceareaofasolid
calculated by the BET equation, from gas adsorption data
5.2 Test Methods B922 and C1274 and ISO 9277 and ISO
obtained under specific conditions.
18757 exist for determination of the as produced surface area
of bulk metal and metal oxide powders. During the delivery of
3.1.10 surface area, specific, n—the area, per unit mass of a
nanoparticles in inhalation exposure chambers, the material
granular or powdered or formed porous solid, of all external
properties may undergo change and therefore have properties
plusinternalsurfacesthatareaccessibletoapenetratinggasor
that differ from the material as produced. This test method
liquid. B922
describesthedeterminationofthe as administeredsurfacearea
4. Summary of Test Method of airborne metal oxide nanoparticles in inhalation exposure
chambers for inhalation toxicology studies.
4.1 An appropriate filter is pre-weighed to the nearest 1 ×
-8
10 kg (0.01 mg), outgassed, and the background surface area
6. Interferences
measured prior to nanoparticle collection in an inhalation
6.1 This test method can be used to determine the internal
exposure chamber. A sufficient amount of nanoparticles (to
and external surface of nanoparticles only after the surfaces
provide at least the minimum surface area required for reliable
have been cleaned of any physically adsorbed molecules (for
results for the instrument used) are collected on the filter, the
example, water or volatile organic compounds) which prevent
filter with particles is post-weighed, outgassed, and total
physicaladsorptionofthegasprobemoleculesusedtomeasure
surface area measured. The surface area concentration of the
surface area. Therefore, it is necessary to remove these
airbornenanoparticlesintheexposurechamberisestimatedby
adsorbedcontaminantspriortosurfaceareaanalysis(Anderson
subtracting the background filter surface area from the total
(2), Gregg and Sing (3)). Outgassing is performed by evacu-
surface area of the filter with nanoparticles and normalized by
-1
ating the sample (typically at 10 Pa) and can be accelerated
the volume of air sampled, with the final result expressed as
2 3 by using elevated temperatures, provided no irreversible
m /m (LeBouf et al. (5)).
sample changes occur. Outgassing is complete when duplicate
4.2 Multipoint BET Analyses—Volume of gas adsorbed at
surface area analyses produce results within expected instru-
-6 3
77 K (liquid nitrogen temperature) is determined as 10 m
ment repeatability limits.
(cm ) corrected to standard temperature and pressure for a
minimum of five relative pressures within the linear BET 7. Apparatus
transformation range of the physical adsorption isotherm
7.1 Commercial instruments employing low temperature
characteristic of the filter or nanoparticle, or both. The linear
(77 K) krypton adsorption are available from several manufac-
range is that which results in a least squares correlation
turers for the measurement of specific surface area by physical
coefficientof0.999orgreaterfortherelationshipbetweenBET
adsorption. Use of krypton is required due to the low overall
transformationandrelativepressure.Typically,thelinearrange
surface area of particle-laden samples and the need to accu-
includes relative pressures between 0.05 and 0.30.
rately measure the background surface area of the filter used
4.3 It is important to use an analytical balance to determine for sample collection. Some instruments are automated ver-
thesamplemass.Thephysicaladsorptioninstrumentmeasures sions of the classical vacuum apparatus. Others make use of
E2864 − 18 (2022)
TABLE 1 Available Powder Reference Materials
balanced adsorption technology. Additionally, commercial in-
struments are available which measure physical adsorption BET Specific
Reference
Powder Adsorbate Surface Area
A
based on the dynamic flow method.
Material
(m /g)
-8
7.2 Analytical Balance, having a sensitivity of1×10 kg.
BAM-PM-101 Silicon dioxide Krypton 0.177
BAM-PM-102 α-Alumina Nitrogen 5.41
7.3 Degassing Equipment, capable of maintaining a sample
BAM-PM-104 α-Alumina Nitrogen 79.8
degas temperature of 120 6 10°C. BAM-P105 Nanoporous glass Nitrogen 198.5
NIST 1898 Titanium dioxide Nitrogen 55.55
7.4 Sampling pump, calibrated and capable of maintaining
NIST 1900 Silicon nitride Nitrogen 2.79
NIST 2206 Nanoporous glass Nitrogen 10.99
constant flow.
NIST 2207 Nanoporous glass Nitrogen 177.8
7.5 Pellet style glass sample cell, minimum internal diam-
A
BAM = Bundesanstalt für Materialforschung und prüfung; NIST = National
eter 9 mm.
Institute of Standards and Technology
7.6 Static charge neutralizer, properly operating.
NOTE 1—Use caution with static charge neutralizers as static discharge
could be an ignition source for certain types of filters that contain
deviation) in that same laboratory.
flammable constituents (for example, nitroscellulose).
10.2.1 Theusermustverifythebackgroundsurfaceareafor
the particular type and lot of filter used.
8. Reagents and Materials
10.2.2 Handle a filter on the edges only using metal
8.1 Liquid Nitrogen.
tweezers, pass through a static charge neutralizer, and record
8.2 Krypton, 99.999 mole percent, with the sum of N,O ,
the mass reading on a calibrated analytical balance capable of
2 2
-8
Ar,CO ,hydrocarbons(asCH ),andH Ototalinglessthan10
reading to1×10 kg.
2 4 2
ppm, dry and oil-free, cylinder, or other source of purified
NOTE 5—If desired, a control filter can be weighed and handled in
krypton.
exactly the same manner as the experimental filter to verify that the filter
handling steps do not result in gravimetric errors.
8.3 Helium,99.99molepercent,withthesumofN,O ,Ar,
2 2
CO , hydrocarbons (as CH ), and H O totaling less than 10
10.2.3 Equilibrate the filter in the same temperature- and
2 4 2
ppm, dry and oil-free, cylinder, or other source of purified
humidity-controlledenvironmentasthebalancepriortoweigh-
helium, if needed for determination of void space above
ing.
sample.
10.2.4 Wearing clean nitrile gloves roll the filter into a
cylinder having a diameter narrow enough to insert it into the
8.4 Track-etched polycarbonate (TEPC) filters, 0.037-m
-7
glass sample cell.
(37-mm) diameter,4×10 -m (0.4-µm) pore size.
NOTE2—Otherfiltertypesandsizesoffiltersmaybeusedprovidedthat
NOTE 6—The filter can be wrapped around a clean glass rod to obtain
theirbackgroundweight,surfacearea,pressuredrop,collectionefficiency,
cylindrical shape. If helpful, pass the filter through a static charge
and physical integrity have been characterized (LeBouf et al. (5)).
neutralizer before inserting it into the glass
...