ASTM E2224-2018 Standard Guide for Forensic Analysis of Fibers by Infrared Spectroscopy.pdf

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1、Designation: E2224 10E2224 18Standard Guide forForensic Analysis of Fibers by Infrared Spectroscopy1This standard is issued under the fixed designation E2224; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revisio

2、n. 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 Infrared (IR) spectrophotometeryspectroscopy is a valuable method of fiber polymer identification and comparison inforensic examin

3、ations. The use of IR microscopes, coupled with Fourier transform infrared (FT-IR) spectrometers(FTIR)spectrometers, has greatly simplified the IR analysis of single fibers, thus making the technique feasible for routine use in theforensic laboratory. This guide provides basic recommendations and in

4、formation about IR spectrometers and accessories, with anemphasis on sampling techniques specific to fiber examinations. The particular method(s) employed by each examiner orlaboratory will depend upon available equipment, examiner training, sample suitability, and sample size.1.2 This guideline is

5、intended to assist individuals and laboratories that conduct forensic fiber examinations and comparisonsin the effective application of infrared spectroscopy to the analysis of fiber evidence.Although this guide is intended to be appliedto the analysis of single fibers, many of its suggestions are a

6、pplicable to the infrared analysis of small particles in general.forexaminers with a basic knowledge of the theory and practice of IR spectroscopy, as well as experience in the handling and forensicexamination of fibers. In addition, this guide is to be used in conjunction with a broader analytical

7、scheme.1.3 If polymer identification is not readily apparent from optical data alone, an additional method of analysis, such asmicrochemical tests, melting point, IR spectroscopy, Raman spectroscopy, or pyrolysis gas chromatography, should be used. Anadvantage of IR spectroscopy is that the instrume

8、ntation is readily available in most forensic laboratories and the technique isminimally destructive.1.4 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.1.5 This standard cannot replace knowledge, skills, or abilities acquired

9、 through education, training, and experience and is tobe used in conjunction with professional judgment by individuals with such discipline-specific knowledge, skills, and abilities.1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the r

10、esponsibilityof the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability ofregulatory limitations prior to use.1.7 This international standard was developed in accordance with internationally recognized principles on standardizati

11、onestablished in the Decision on Principles for the Development of International Standards, Guides and Recommendations issuedby the World Trade Organization Technical Barriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2D123 Terminology Relating to TextilesE131 Terminology Re

12、lating to Molecular SpectroscopyE1421 Practice for Describing and Measuring Performance of Fourier Transform Mid-Infrared (FT-MIR) Spectrometers: LevelZero and Level One TestsE1459 Guide for Physical Evidence Labeling and Related DocumentationE1492 Practice for Receiving, Documenting, Storing, and R

13、etrieving Evidence in a Forensic Science LaboratoryE2228 Guide for Microscopical Examination of Textile Fibers1 This guide is under the jurisdiction of ASTM Committee E30 on Forensic Sciences and is the direct responsibility of Subcommittee E30.01 on Criminalistics.Current edition approved Sept. 15,

14、 2010Sept. 1, 2018. Published October 2010September 2018. Originally approved in 2002. Last previous edition approved in 20022010as E2224 02.E2224 10. DOI: 10.1520/E2224-10.10.1520/E2224-18.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at servic

15、eastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.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. Be

16、causeit 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

17、 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States13. Terminology3.1 DefinitionsFor definitions of terms used in this guide, refer to TerminologyTerminologies D123 and E131.3.2 Definitions of Terms Specific to This Standard:3.2.1 absorbance (A)the logarithm to the base

18、10 of the reciprocal of the transmittance, (T):A 5log101/T! 52log10T3.2.1 absorptionaperture, bandna region of the absorption spectrum in which the absorbance passes through a maximum.anopening in an optical system that controls the amount of light passing through a system.3.2.3 absorption spectruma

19、 plot, or other representation, of absorbance, or any function of absorbance, against wavelength,or any function of wavelength.3.2.4 absorptivity (a)absorbance divided by the product of the sample pathlength (b) and the concentration of the absorbingsubstance (c):a 5A/bc3.2.2 attenuated total reflec

20、tion (ATR)(ATR), nreflection that occurs when an absorbing coupling mechanism acts in theprocess of total internal reflection to make the reflectance less than unity.a method of spectrophotometric analysis based on thereflection of energy at the interface of two media which have different refractive

21、 indices and are in intimate contact with each other.3.2.3 backgroundbackground, napparent absorption caused by anything other than the substance for which the analysis isbeing made. E1313.2.4 cellulosic fiberfiber, nfiber composed of polymers formed from glucose subunits.3.2.5 far-infrareddelustran

22、t, npertaining to the infrared region of the electromagnetic spectrum with wavelength range fromapproximately 25 to 300 m (wavenumber range 400 to 30 cma pigment, usually titanium dioxide, used to dull the luster of amanufactured fiber.-1). E22283.2.6 Fourierdiffraction, transformna mathematical ope

23、ration that converts a function of one independent variable to oneof a different independent variable. phenomenon that arises as a result of passing radiation through the “lens” of themicrospectrometer and past the edges of objects such as apertures and the specimen. It causes radiation to deviate f

24、rom its usuallystraight line causing blurring of what should be sharp images (1).33.2.9.1 DiscussionIn FT-IR spectroscopy, the Fourier transform converts a time function (the interferogram) to a frequency function (the infraredabsorption spectrum). Spectral data are collected through the use of an i

25、nterferometer, which replaces the monochrometer foundin the dispersive infrared spectrometer.3.2.10 Fourier transform infrared (FT-IR) spectrometrya form of infrared spectrometry in which an interferogram is obtained;this interferogram is then subjected to a Fourier transformation to obtain an ampli

26、tude-wavenumber (or wavelength) spectrum.3.2.7 generic classclass, na group of fibers having similar (but not necessarily identical) chemical composition; a genericname applies to all members of a group and is not protected by trademark registration. as used with textile fibers, a grouping havingsim

27、ilar chemical compositions or specific chemical characteristics. D1233.2.7.1 DiscussionAgeneric name applies to all members of a group and is not protected by trademark registration. Generic names for manufacturedfibers include, for example, rayon, nylon, and polyester. Generic names to be used in t

28、he United States for manufactured fibers wereestablished as part of the Textile Fiber Products Identification Act enacted by Congress in 1954 (12).3.2.8 infraredinterference fringes, npertaining to the region of the electromagnetic spectrum with wavelength range fromapproximately 0.78 to 1000 m (wav

29、enumber range 12 800 to 10 cmthe pattern that results from constructive and destructiveinterference of light waves.-1).3.2.13 infrared spectroscopypertaining to spectroscopy in the infrared region of the electromagnetic spectrum.3.2.9 internal reflectionman-made fiber, spectroscopy n(IRS)the techniq

30、ue of recording optical spectra by placing a samplematerial in contact with a transparent medium of greater refractive index and measuring the reflectance (single or multiple) fromthe interface, generally at angles of incidence greater than the critical angle.a class name for various genera of filam

31、ent, tow, orstaple produced from fiber-forming substances which are chemically synthesized or modified.3 The boldface numbers in parentheses refer to thea list of references at the end of this standard.E2224 1823.2.10 manufactured (man-made)fiber, fiberna class name for various genera of filament, t

32、ow, or staple produced from fiberforming substance which mayfiber-forming substances which can be (1) polymers synthesized from chemical compound,compounds, (2) modified or transformed natural polymers, or (3) glass.3.2.11 meaningful difference(s), na feature or property of a sample that does not fa

33、ll within the variation exhibited by thecomparison sample, considering the limitations of the sample or technique, and therefore indicates the two samples do not sharea common origin. The use of this term does not imply the formal application of statistical tests.3.2.11.1 DiscussionThe evaluation of

34、 variation is typically based on the visual comparison of spectral data.3.2.12 mid-infraredmid-infrared, npertaining to the infraredIR region of the electromagnetic spectrum with wavelengthrange from approximately 2.5 to 25 m (wavenumber range approximately 4000 to 400 cm-1).3.2.17 near-infraredpert

35、aining to the infrared region of the electromagnetic spectrum with wavelength range fromapproximately 0.78 to 2.5 m (wavenumber range 12 820 to 4000 cm-1).3.2.18 spectrometerphotometric device for the measurement of spectral transmittance, spectral reflectance, or relative spectralemittance.3.2.13 s

36、ubgeneric classsub-generic class, na group of fibers within a generic class that share the same polymerbase-polymer composition; subgenericsub-generic names include, for example, nylon 6, nylon 6,6, and poly(ethylene terephthalate).6and nylon 6,6.3.2.20 transmittance (T)the ratio of radiant power tr

37、ansmitted by the sample, I, to the radiant power incident on the sample,Io:T 5I/Io3.2.21 wavelengththe distance, measured along the line of propagation, between two points that are in phase on adjacentwaves.3.2.22 wavenumberthe number of waves per unit length, in a vacuum, usually given in reciproca

38、l centimeters, cm-1.4. Summary of Guide4.1 This guideline covers identification of fiber polymer composition by interpretation of guide covers the collection andcomparison of IR absorption spectra obtained by infrared microspectroscopy. It is intended to be applicablefrom fibers and can beapplied to

39、 a wide range of infrared spectrophotometeryIR spectrometers and microscope configurations.Additional information oninfrared and microscopical analyses can be found in the sources listed in the Bibliography at the end of this guide.accessoryconfigurations. This guide is not meant to be the first ste

40、p in the process of a fiber examination (3).4.2 Spectra may also be obtained by a variety of alternative IR techniques. Other techniques (not covered in the scope of thisguideline) include: micro internal reflection spectroscopy (MIR), which differs from attenuated total reflectance (ATR) in that th

41、einfrared radiation is dependent upon the amount of sample in contact with the surface of the prism (2):4.2.1 Diamond cell (medium or high pressure) used with a beam condenser (3-5) (This combination is frequently used with aspectrophotometer configured for mid- and far-IR).4.2.2 Thin films: solvent

42、 (6, 7), melt (4), or mechanically prepared (8).4.2.3 Lead foil technique (6).4.2.4 Micro potassium bromide (micro-KBr) (or other appropriate salt) pellets (9, 10). This list is not meant to be totallyinclusive or exclusive.4.2 This analytical method covers manufactured textile fibers (with the exce

43、ption of inorganic fibers), including, but not limitedto:Acetate Modacrylic Polyester Vinal (5)Acrylic Novoloid (5) Rayon VinyonAnidel Nylon SaranAramid Nytril SpandexAzlon (5) Olefin SulfarFluorocarbon Polybenzimidazole(PBI)TriacetateLastrile Polycarbonate RubberThis analytical guide focuses on the

44、 identification of manufactured textile fibers (with the exception of inorganic fibers).Although natural fibers may also be analyzed by IR spectroscopy, they are excluded from this guideline because no additionaldiscriminating compositional information of the fiber is provided over that yielded by l

45、ight microscopy. However, infraredspectrophotometery may provide significantly useful information if there are dyes present in the natural fiber and can serve todistinguish among similarly colored fibers.light microscopy is the primary method for the identification of natural fibers.E2224 1835. Sign

46、ificance and Use5.1 Fiber samples may be prepared and mounted for microscopical infrared analysis by a variety of techniques. Infrared spectraof fibers are obtained using an IR spectrophotometer coupled with an IR microscope. Fiber polymer identification is made bycomparison of the fiber spectrum wi

47、th reference spectra.5.1 Consideration should be given to the potential for This guide is designed to assist an examiner in the selection of appropriatesample preparation methods for the analysis, comparison, and identification of fibers using IR spectroscopy. IR spectroscopy mayprovide additional c

48、ompositional information that may be obtained by IR spectroscopy over than is obtained using polarized lightmicroscopy alone (see Microscopy Guidelines). alone. The extent to which IR spectral comparison is indicatedconducted will varywith specific sample and case evaluations.5.2 The recommended poi

49、nt for IR analysis in a forensic fiber examination is following visible and ultraviolet (UV) comparisonmicroscopy (fluoresence microscopy), IR analysis should follow visible and fluorescence comparison microscopy, polarized lightmicroscopy, and UV/visible spectroscopy, but before dye extraction for thin-layer chromatography. This list of analyticaltechniques is not meant to be totally inclusive or exclusive.ultraviolet (UV)/visible spectroscopy. If no meaningful differences arenoted between the known and unknown samples in optical pr