1、Designation: E2834 12 (Reapproved 2018)Standard Guide forMeasurement of Particle Size Distribution of Nanomaterialsin Suspension by Nanoparticle Tracking Analysis (NTA)1This standard is issued under the fixed designation E2834; the number immediately following the designation indicates the year ofor
2、iginal 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 guide deals with the measurement of particle sizedistrib
3、ution of suspended particles, from 10 nm to the onset ofsedimentation, sample dependent, using the nanoparticle track-ing analysis (NTA) technique. It does not provide a completemeasurement methodology for any specific nanomaterial, butprovides a general overview and guide as to the methodologythat
4、should be followed for good practice, along with potentialpitfalls.1.2 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.3 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It
5、is theresponsibility of the user of this standard to establish appro-priate safety, health, and environmental practices and deter-mine the applicability of regulatory limitations prior to use.1.4 This international standard was developed in accor-dance with internationally recognized principles on s
6、tandard-ization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2C322 Practice for Sampling Ceramic Whitewa
7、re ClaysE456 Terminology Relating to Quality and StatisticsE1617 Practice for Reporting Particle Size CharacterizationDataE2490 Guide for Measurement of Particle Size Distributionof Nanomaterials in Suspension by Photon CorrelationSpectroscopy (PCS)2.2 ISO Standards:3ISO 13320 Particle Size Analysis
8、Laser Diffraction Meth-odsISO 13321 Particle Size AnalysisPhoton CorrelationSpectroscopyISO 14488 Particulate MaterialsSampling And SampleSplitting for the Determination of Particulate PropertiesISO 22412 Particle Size AnalysisDynamic Light Scatter-ing (DLS)3. Terminology3.1 Definitions:3.1.1 diffus
9、ion coeffcient, na measure to characterize therate a particular molecule or particle moves in a particularmedium when driven by random thermal agitation (Brownianmotion).3.1.1.1 DiscussionAfter measurement, the value is to beinputted into the Stokes-Einstein equation (Eq 1, see7.2.1.2(3). Diffusion
10、coefficient units in nanoparticle trackinganalysis (NTA) measurements are typically cm2/s, rather thanthe correct SI units of m2/s.3.1.2 repeatability, nin NTA and other particle sizingtechniques, this usually refers to a measure of the precision ofrepeated consecutive measurements on the same group
11、 ofparticles under identical conditions and is normally expressedas a relative standard deviation (RSD) or coefficient of varia-tion (CV).3.1.2.1 DiscussionThe repeatability value reflects the sta-bility (instrumental, but mainly the sample) of the system overtime. Changes in the sample could includ
12、e dispersion, aggre-gation and settling.3.1.3 reproducibility, nin NTA and particle sizing thisusually refers to a measure of the deviation of the resultsobtained from the first aliquot to that obtained for the secondand further aliquots of the same bulk sample (and therefore issubject to the homoge
13、neity or heterogeneity of the starting1This guide is under the jurisdiction of ASTM Committee E56 on Nanotech-nology and is the direct responsibility of Subcommittee E56.02 on Physical andChemical Characterization.Current edition approved Jan. 1, 2018. Published January 2018. Originallyapproved in 2
14、012. Last previous edition approved in 2012 as E2834 12. DOI:10.1520/E2834-12R18.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page
15、 onthe ASTM website.3Available from American National Standards Institute (ANSI), 25 W. 43rd St.,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 StatesThis international standard was develope
16、d in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.1material and the sampl
17、ing method employed). Normally ex-pressed as a relative standard deviation (RSD) or coefficient ofvariation (CV).3.1.3.1 DiscussionIn a heterogenous and polydisperse (forexample, slurry) system, it is often the largest error whenrepeated samples are taken. Other definitions of reproducibilityalso ad
18、dress the variability among single test results gatheredfrom different laboratories when inter-laboratory testing isundertaken, or operator-to-operator, instrument-to-instrument,location-to-location, or even day-to-day. It is to be noted thatthe same group of particles can never be measured in such
19、asystem of tests and therefore reproducibility values maytypically be considerably in excess of repeatability values.3.1.4 robustness, na measure of the change of the requiredparameter with deliberate and systematic variations in any orall of the key parameters that influence it.3.1.4.1 DiscussionFo
20、r example, dispersion energy input(that is, ultrasound power and duration) almost certainly willaffect the reported results. Variation in pH is likely to affect thedegree of agglomeration and so forth. A useful discussion ofrobustness experiment considerations is found in the ICHValidation of Analyt
21、ical Procedures Q2(R1) Guideline (1).43.1.5 rotational diffusion, na process by which the equi-librium statistical distribution of the overall orientation ofmolecules or particles is maintained or restored.3.1.6 translational diffusion, na process by which theequilibrium statistical distribution of
22、molecules or particles inspace is maintained or restored.3.1.7 visualization, nas it relates to the NTA technique,the particles themselves are not imaged, being below thediffraction limit. Each particle acts as a point scatterer, meaningthat the imaging system only sees the scattered light from thep
23、article. This allows the position of each particle to beidentified and followed with respect to time. See 7.2.3.1.7.1 DiscussionThe intensity and shape of the scatteredlight pattern for each particle may vary, and some additionalinformation may be obtained from these differences, at leastqualitative
24、ly, but is outside the scope of this guide.3.1.8 percentile, na statistical measure of the distributionof sizes. The size below which a certain percent of thedistribution falls. For example, the 10th percentile is the sizebelow which 10 percent of the particles may be found.Expressed in ISO form as
25、x10,x50,x90, and also commonlyexpressed as D10, D50, D90. The 50th percentile is themedian.3.1.9 coeffcient of variation, nin statistics, a normalizedmeasure of dispersion of a distribution. Defined as the standarddeviation divided by the mean value. (Note: CV = SD/Mean)3.1.10 relative standard devi
26、ation, nin statistics, the ab-solute value of the coefficient of variation, expressed as apercentage. (Note: RSD = 100SD/Mean)NOTE 1Other common statistical measures are defined in Terminol-ogy E456.3.2 Acronyms:3.2.1 CVcoefficient of variation3.2.2 CCDcharge-coupled device3.2.3 CMOScomplementary me
27、taloxidesemiconductor3.2.4 DLSdynamic light scattering3.2.5 EMCCDelectron-multiplying charge-coupled de-vice3.2.6 NTAnanoparticle tracking analysis3.2.7 PCSphoton correlation spectroscopy3.2.8 RSDrelative standard deviation4. Summary of Guide4.1 Nanoparticle tracking analysis (NTA) is a method forth
28、e direct and real-time visualization and analysis of nanopar-ticles in liquids. Particles in suspension are illuminated with afocused laser beam. Light scattered from each particle isvisible through magnifying optics fitted to a digital camerasuch as a CCD. The software analyzes the video stream fro
29、mthe camera, identifying and tracking the motion of each particlewith time. Because each particle in the field of view is beingsimultaneously but separately tracked and analyzed, the par-ticle size distribution profile obtained by NTA is a directnumber-based distribution.4.2 The laser beam is focuse
30、d such that only particles in thefocal plane of the magnifying optics are illuminated. Particlesout of the focal plane are not illuminated and at the size rangeunder discussion are not visible to the camera. This yields ahigh signal to noise image, allowing particles as small as 10 nmto be visualize
31、d, depending on sample material. While outsidethe scope of this document, the technique is generally able tomeasure particles as large as approximately 1 m.4.3 The average distance each particle moves in the image isautomatically calculated by the software. From this value, theparticle diffusion coe
32、fficient can be obtained and through theuse of the Stokes-Einstein equation, particle size can bedetermined.4.4 This guide discusses the scientific basis for thetechnique, size limits, concentration ranges, sampling andsample preparation considerations, condition and analysisselection, data interpre
33、tation and comparison to other comple-mentary techniques.5. Significance and Use5.1 NTA is one of the very few techniques that are able todeal with the measurement of particle size distribution in thenano-size region. This guide describes the NTA technique fordirect visualization and measurement of
34、Brownian motion,generally applicable in the particle size range from severalnanometers until the onset of sedimentation in the sample. TheNTAtechnique is usually applied to dilute suspensions of solidmaterial in a liquid carrier. It is a first principles method (thatis, calibration in the standard u
35、nderstanding of this word, is notinvolved). The measurement is hydrodynamically based andtherefore provides size information in the suspending medium(typically water). Thus the hydrodynamic diameter will almostcertainly differ from size diameters determined by other4The boldface numbers in parenthes
36、es refer to the list of references at the end ofthis standard.E2834 12 (2018)2techniques and users of the NTAtechnique need to be aware ofthe distinction of the various descriptors of particle diameterbefore making comparisons between techniques (see 8.7).Notwithstanding the preceding sentence, the
37、technique isroutinely applied in industry and academia as both a researchand development tool and as a QC method for the character-ization of submicron systems.6. Reagents6.1 In general, no reagents specific to the technique arenecessary. However, dispersing and stabilizing agents often arerequired
38、for a specific test sample in order to preserve colloidalstability during the measurement. A suitable diluent is used toachieve a particle concentration appropriate for the measure-ment. The apparent hydrodynamic size or diffusion coefficientmay undergo change on dilution, as the ionic environment,w
39、ithin which the particles are dispersed, changes in nature orconcentration. This is particularly noticeable when diluting amonodisperse latex. A latex that is measured as 60 nm in 1 10-3M NaCl can have a hydrodynamic diameter of over 70 nmin110-6M NaCl (close to deionized water).6.2 In order to mini
40、mize any changes in the system ondilution, it is common to use the “mother liquor”. This is theliquid in which the particles exist in stable form and is usuallyobtained by centrifuging of the suspension or making up thesame ionic composition of the dispersant liquid if knowledgeof these components i
41、s available. Many biological materialsare measured in a buffer (often phosphate buffered saline),which confers the correct (range of) conditions of pH and ionicstrength to assure stability of the system. Instability (usuallythrough inadequate zeta potentialsee (2) can promote ag-glomeration leading
42、to settling or sedimentation in a solid-liquid system or creaming in a liquid-liquid system (emulsion).Such fundamental changes interfere with the stability of thesuspension and need to be minimized as they affect the quality(accuracy and repeatability) of the reported measurements.These should be i
43、nvestigated in a robustness experiment.7. Procedure7.1 Verification:7.1.1 The instrument to be used in the measurement shouldbe verified for correct performance, within pre-defined qualitycontrol limits, by following protocols issued by the instrumentmanufacturer. These confirmation tests normally i
44、nvolve theuse of one or more NIST-traceable spherical particle sizestandards. In the sub-micron (10 %), care must be exercised to ensure that theappropriate methods and conditions are selected to ensurereliable results. Analysis time, image capture settings, andsample concentration are variables tha
45、t need to be considered.8.8 Conversion of the Concentration Distribution to OtherParticle Size Distributions:8.8.1 With any technique, the most reliable results are thosereported in that techniques natural format. Conversion to otherdistribution bases may be mathematically valid, but the as-sumption
46、s in obtaining this derived information need to becarefully understood and the implications of reporting thisinformation also carefully evaluated. Small changes in col-lected data can give rise to enormous changes in derived resultand as such treat any derived result with caution and skepti-cism. To
47、 convert from concentration to volume distributionwould involve the manipulation of perfect noise-free experi-mental data. The wider the initial distribution the more seriousare the potential errors in the conversion.8.8.2 Notwithstanding the above caveats and cautions, con-version to a volume-weigh
48、ted distribution can often provide anindication of the relative importance (prominence) of two ormore reported peaks. A common situation is to see an appar-ently dominant small-size peak virtually disappearing and alow-intensity larger-sized peak becoming the primary modeafter conversion to volume w
49、eighting.9. Report9.1 See Practice E1617.9.2 As a minimum the following need reporting in additionto graphical and tabular information:9.2.1 The instrument type and manufacturer and serialnumber. Version of software employed.9.2.2 Date and results of the last verification. Details of thetraceability of the standards employed.9.2.3 Date of measurement together with analysts nameand affiliation.9.2.4 Details of the sample including chemical composition.Shape information if obtained by electron microscopy oratomic force microscopy is
