1、Designation: E2864 13E2864 18Standard Test Method forMeasurement of Airborne Metal and Metal OxideNanoparticle Surface Area Concentration in InhalationExposure Chambers using Krypton Gas Adsorption1This standard is issued under the fixed designation E2864; the number immediately following the design
2、ation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers determin
3、ation of surface area of airborne metal and metal oxide nanoparticles in inhalation exposurechambers for inhalation toxicology studies. Surface area may be measured by gas adsorption methods using adsorbates such asnitrogen, krypton, and argon (Brunauer et al., 1938; Anderson, 1975; Gregg and Sing,
4、1982) al. (1, ),2, 3)2 Anderson (2), Greggand Sing (3) or by ion attachment and mobility-based methods (Ku and Maynard, 2005) Maynard (4).). This test method isspecific to the measurement of surface area by gas adsorption by krypton gas adsorption. The test method permits the use of anymodern commer
5、cial krypton adsorption instruments but strictly defines the sample collection, outgassing, and analysis proceduresfor metal and metal oxide nanoparticles. Use of krypton is required due to the low overall surface area of particle-laden samplesand the need to accurately measure the background surfac
6、e area of the filter used for sample collection. Instrument-reported valuesof surface area based on the multipoint Brunauer, Emmett andTeller (BET) equation (Brunauer et al., 1938;Anderson, 1975; Greggand Sing, 1982) al. (1,), Anderson (2,), Gregg and Sing (3) are used to calculate surface area of a
7、irborne nanoparticles collectedon 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
8、.1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety safety, health, and healthenvironmental practices and determine theapplicability of regulatory limitations
9、prior to use.1.4 This international standard was developed in accordance with internationally recognized principles on standardizationestablished in the Decision on Principles for the Development of International Standards, Guides and Recommendations issuedby the World Trade Organization Technical B
10、arriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:3B922 Test Method for Metal Powder Specific Surface Area by Physical AdsorptionC1274 Test Method for Advanced Ceramic Specific Surface Area by Physical AdsorptionE691 Practice for Conducting an Interlaboratory Study to Determ
11、ine the Precision of a Test MethodE2456 Terminology Relating to Nanotechnology2.2 ISO Standards:4ISO 9277 Determination of the Specific Surface Area of Solids by Gas Adsorption using the BET MethodISO 18757 Fine Ceramics (Advanced Ceramics, Advanced Technical Ceramics)Determination of Specific surfa
12、ce Area ofCeramic Powders by Gas Adsorption using the BET Method3. Terminology3.1 DefinitionsFor additional definitions related to nanotechnology, see Terminology E2456.1 This test method is under the jurisdiction ofASTM Committee E56 on Nanotechnology and is the direct responsibility of Subcommitte
13、e E56.02 on Physical and ChemicalCharacterization.Current edition approved Sept. 1, 2013Oct. 1, 2018. Published October 2013October 2018. Originally approved in 2013. Last previous edition approved in 2013 as E2864 13. DOI: 10.1520/E2864-13.10.1520/E2864-18.2 The boldface numbers in parentheses refe
14、r to the list of references at the end of this standard.3 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.4 Ava
15、ilable from American National Standards Institute (ANSI), 25 W. 43rd St., 4th Floor, New York, NY 10036, http:/www.ansi.org.This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
16、it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the official document.Copyright ASTM International, 100 Barr
17、 Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States13.1.1 nanoparticles, nin nanotechnology, a sub-classification of ultrafine particle with lengths in two or three dimensionsgreater than 0.001 micrometre (1 nanometre) and smaller than about 0.1 micrometre (100 nanometres) an
18、d which may or may notexhibit a size-related intensive property. E24563.1.2 adsorbate, nmaterial that has been retained by the process of adsorption. B9223.1.3 adsorbent, nany solid having the ability to concentrate or collect significant quantities of other substances on its surface.B9223.1.4 adsor
19、ption, na process in which fluid molecules are concentrated or collected on a surface by chemical or physicalforces, or both. B9223.1.5 BET-constant, nan indication of the magnitude of the adsorbent/adsorbate interactions in the first adsorbed layer.3.1.6 outgassing, nthe evolution of gas from a mat
20、erial in a vacuum or inert gas flow, at or above ambient temperature. B9223.1.7 physical adsorption (van der Waals adsorption), nthe binding of an adsorbate to the surface of a solid by forces whoseenergy levels approximate those of condensation. B9223.1.8 surface area, nthe total area of the surfac
21、e of a powder or solid including both external and accessible internal surfaces(from voids, cracks, open porosity, and fissures); the area may be calculated by the BETequation from gas adsorption data obtainedunder specific conditions; it is useful to express this value as the specific surface area,
22、 for example, surface area per unit mass ofsample (m2/kg). B9223.1.9 surface area (BET), nthe total surface area of a solid calculated by the BET equation, from gas adsorption data obtainedunder specific conditions.3.1.10 surface area, specific, nthe area, per unit mass of a granular or powdered or
23、formed porous solid, of all external plusinternal surfaces that are accessible to a penetrating gas or liquid. B9224. Summary of Test Method4.1 An appropriate filter is pre-weighed to the nearest 1 10-8 kg (0.01 mg), outgassed, and the background surface areameasured prior to nanoparticle collection
24、 in an inhalation exposure chamber. A sufficient amount of nanoparticles (to provide atleast the minimum surface area required for reliable results for the instrument used) are collected on the filter, the filter withparticles is post-weighed, outgassed, and total surface area measured. The surface
25、area concentration of the airborne nanoparticlesin the exposure chamber is estimated by subtracting the background filter surface area from the total surface area of the filter withnanoparticles and normalized by the volume of air sampled, with the final result expressed as m2/m3 (LeBouf et al., 201
26、1) al. (5).).4.2 Multipoint BET AnalysesVolume of gas adsorbed at 77 K (liquid nitrogen temperature) is determined as 10-6 m3 (cm3)corrected to standard temperature and pressure for a minimum of five relative pressures within the linear BET transformation rangeof the physical adsorption isotherm cha
27、racteristic of the filter and/or nanoparticle. or nanoparticle, or both. The linear range is thatwhich results in a least squares correlation coefficient of 0.999 or greater for the relationship between BET transformation andrelative pressure. Typically, the linear range includes relative pressures
28、between 0.05 and 0.30.4.3 It is important to use an analytical balance to determine the sample mass. The physical adsorption instrument measures thetotal amount of gas adsorbed onto the sample under analysis. The sample mass is then used to normalize the measured adsorptionresults. Any error in the
29、sample mass will affect the final BET surface area.4.4 Calculations are based on the BET equation, as required by the instrument being used for the determination. The instrumentpressure tolerance (pressure range that must be maintained within a sample cell to accept a valid data point) is 6.6 Pa. In
30、 thisstandard, the cross-sectional area for the krypton adsorbate is taken to be 2.02 10-19 m2 (ISO 9277); however, some instrumentsoftware may use a different default value. As such, the cross-sectional area of the krypton adsorbate used in calculations shouldbe reported with the BET surface area r
31、esults.5. Significance and Use5.1 A tiered strategy for characterization of nanoparticle properties is necessary to draw meaningful conclusions concerningdose-response relationships observed during inhalation toxicology experiments. This tiered strategy includes characterization ofnanoparticles as p
32、roduced (that is, measured as the bulk material sold by the supplier) and as administered (that is, measured atthe point of delivery to a test subject) (Oberdorster et al., 2005) al. (6).).5.2 Test Methods B922 and C1274 and ISO Standards 9277 and ISO 18757 exist for determination of the as produced
33、 surfacearea of bulk metal and metal oxide powders. During the delivery of metal and metal oxide nanoparticles in inhalation exposurechambers, the material properties may undergo change and therefore have properties that differ from the material as produced. Thistest method describes the determinati
34、on of the as administered surface area of airborne metal and metal oxide nanoparticles ininhalation exposure chambers for inhalation toxicology studies.6. Interferences6.1 This test method can be used to determine the internal and external surface of nanoparticles only after the surfaces have beencl
35、eaned of any physically adsorbed molecules (for example, water or volatile organic compounds) which prevent physicalE2864 182adsorption of the gas probe molecules used to measure surface area. Therefore, it is necessary to remove these adsorbedcontaminants prior to surface area analysis (Anderson, 1
36、975; Gregg and Sing, 1982) (Anderson (2,), Gregg and Sing (3).).Outgassing is performed by evacuating the sample (typically at 10-1 Pa) and can be accelerated by using elevated temperatures,provided no irreversible sample changes occur. Outgassing is complete when duplicate surface area analyses pro
37、duce results withinexpected instrument repeatability limits.7. Apparatus7.1 Commercial instruments employing low temperature (77 K) krypton adsorption are available from several manufacturersfor the measurement of specific surface area by physical adsorption. Use of krypton is required due to the lo
38、w overall surface areaof particle-laden samples and the need to accurately measure the background surface area of the filter used for sample collection.Some instruments are automated versions of the classical vacuum apparatus. Others make use of balanced adsorption technology.Additionally, commercia
39、l instruments are available which measure physical adsorption based on the dynamic flow method.7.2 Analytical Balance, having a sensitivity of 1 10-8 kg.7.3 Degassing Equipment, capable of maintaining a sample degas temperature of 120 6 10C.7.4 Sampling pump, calibrated and capable of maintaining co
40、nstant flow.7.5 Pellet style glass sample cell, minimum internal diameter 9 mm.7.6 Static charge neutralizer, properly operating.NOTE 1Use caution with static charge neutralizers as static discharge could be an ignition source for certain types of filters that contain flammableconstituents (for exam
41、ple, nitroscellulose).8. Reagents and Materials8.1 Liquid Nitrogen.8.2 Krypton, 99.999 mole percent, with the sum of N2, O2,Ar, CO2, hydrocarbons (as CH4), and H2O totaling less than 10 ppm,dry and oil-free, cylinder, or other source of purified krypton.8.3 Helium, 99.99 mole percent, with the sum o
42、f N2, O2, Ar, CO2, hydrocarbons (as CH4), and H2O totaling less than 10 ppm,dry and oil-free, cylinder, or other source of purified helium, if needed for determination of void space above sample.8.4 Track-etched polycarbonate (TEPC) filters, 0.037 m (37 mm) 0.037-m (37-mm) diameter, 4 10-7 m (0.4 m)
43、 -m (0.4-m)pore size.NOTE 2Other filter types and sizes of filters may be used provided that their background weight, surface area, pressure drop, collection efficiency,and physical integrity have been characterized (LeBouf et al., 2011) al. (5).).NOTE 3The 0.037 m 0.037-m diameter, 4 10-7 m pore si
44、ze TEPC filter will collect 20 nm to 100 nm 20-nm to 100-nm particles with 97 %efficiency at a flow rate of 0.002 m3/min (LeBouf et al., 2011; Liu et al., 1983) al. (5,), Liu et al. (7).).8.5 Plastic filter cassette sampler, 0.037 m 0.037-m diameter.9. Hazards9.1 Precautions applying to the use of l
45、iquid nitrogen and compressed gases and handling of powdered nanomaterials shouldbe observed.10. Procedure10.1 Calibration and Standardization:10.1.1 Follow manufacturers instructions for instrument calibration. Verify proper operational performance of the instrumentusing an acceptable reference mat
46、erial. Examples of available reference materials are provided in Table 1. Instrumentmanufacturers may also produce reference materials.TABLE 1 Available Powder Reference MaterialsReferenceMaterialA Powder AdsorbateBET SpecificSurface Area(m2/g)BAM-PM-101 Silicon dioxide Krypton 0.177BAM-PM-102 -Alum
47、ina Nitrogen 5.41BAM-PM-104 -Alumina Nitrogen 79.8BAM-P105 Nanoporous glass Nitrogen 198.5NIST 1898 Titanium dioxide Nitrogen 55.55NIST 1900 Silicon nitride Nitrogen 2.79NIST 2206 Nanoporous glass Nitrogen 10.99NIST 2207 Nanoporous glass Nitrogen 177.8A BAM = Bundesanstalt fr Materialforschung und p
48、rfung;prfung; NIST =National Institute of Standards and TechnologyE2864 18310.2 Background Filter Surface Area:NOTE 4As an alternative to determining the background surface area for each TEPC filter sample, an average background surface area can bedetermined from a representative sample of filters f
49、rom each lot. The between-lot filter surface area variability for TEPC filters (0.037 m (0.037-mdiameter, 4 10-7 m -m pore size) accounted for 65 % of the total variability whereas the within lot-filter variability accounted for 35 % of the totalvariability in one laboratory. The within lot filter repeatability standard deviation has been determined to be 0.03 (pooled relative standard deviation) inthat same laboratory.10.2.1 The user must verify the background surface area for the particular type and lot of filter used.10.2.2 Han
