ASTM E2224-02

Standard Guide for Forensic Analysis of Fibers by Infrared Spectroscopy

SIGNIFICANCE AND USE
Fiber samples may be prepared and mounted for microscopical infrared analysis by a variety of techniques. Infrared spectra of fibers are obtained using an IR spectrophotometer coupled with an IR microscope. Fiber polymer identification is made by comparison of the fiber spectrum with reference spectra.
Consideration should be given to the potential for additional compositional information that may be obtained by IR spectroscopy over polarized light microscopy alone (see Microscopy Guidelines). The extent to which IR spectral comparison is indicated will vary with specific sample and case evaluations.
The recommended point for IR analysis in a forensic fiber examination is following visible and UV comparison microscopy (fluoresence microscopy), polarized light microscopy, and UV/visible spectroscopy, but before dye extraction for thin-layer chromatography. This list of analytical techniques is not meant to be totally inclusive or exclusive.
The following generic types of fiber are occasionally encountered in routine forensic examinations: Anidex, Fluorocarbon, Lastrile, Novoloid, Nytril, Polycarbonate, PBI, Sulfar, Vinal, and Vinyon.
Exemplar data, reference standards, and/or examiner experience may be inadequate for characterization of these fibers by optical microscopical and microchemical techniques. For these fiber types, IR spectroscopic confirmation of polymer type is advisable.
Because of the large number of subgeneric classes, forensic examination of acrylic fibers is likely to benefit significantly from IR spectral analysis (11).
Colorless manufactured fibers are lacking in the characteristics for color comparison available in dyed or pigmented fibers. The forensic examination of these fibers may, therefore, benefit from the additional comparative aspect of IR spectral analysis.
If polymer identification is not readily apparent from optical data alone, an additional method of analysis should be used such as microchemical tests, melting point, p...
SCOPE
1.1 Infrared (IR) spectrophotometery is a valuable method of fiber polymer identification and comparison in forensic examinations. The use of IR microscopes coupled with Fourier transform infrared (FT-IR) spectrometers has greatly simplified the IR analysis of single fibers, thus making the technique feasible for routine use in the forensic laboratory.
1.2 This guideline is intended to assist individuals and laboratories that conduct forensic fiber examinations and comparisons in the effective application of infrared spectroscopy to the analysis of fiber evidence. Although this guide is intended to be applied to the analysis of single fibers, many of its suggestions are applicable to the infrared analysis of small particles in general.

General Information

• Status: Historical
• Publication Date: 09-Jul-2002
• ICS: 07.140 - Forensic science
• ICS: 71.040.50 - Physicochemical methods of analysis
• Technical Committee: E30 - Forensic Sciences
• Drafting Committee: E30.01 - Criminalistics

Relations

• Replaced By: ASTM E2224-10 - Standard Guide for Forensic Analysis of Fibers by Infrared Spectroscopy
• Effective Date: 15-Sep-2010
• Referred By: ASTM E2225-23 - Standard Guide for Forensic Examination of Fabrics and Cordage
• Effective Date: 10-Jul-2002
• Referred By: ASTM E1732-22 - Standard Terminology Relating to Forensic Science
• Effective Date: 10-Jul-2002
• Referred By: ASTM E3260-21 - Standard Guide for Forensic Examination and Comparison of Pressure Sensitive Tapes
• Effective Date: 10-Jul-2002
• Referred By: ASTM E3233-20 - Standard Practice for Forensic Tape Analysis Training Program
• Effective Date: 10-Jul-2002
• Referred By: ASTM E2227-23e1 - Standard Guide for Forensic Examination of Dyes in Textile Fibers by Thin-Layer Chromatography
• Effective Date: 10-Jul-2002
• Referred By: ASTM F3416-21 - Standard Guide for Using Fourier Transform Infrared Spectrometry to Evaluate Synthetic Equine Surface Components
• Effective Date: 10-Jul-2002
• Referred By: ASTM E3085-17 - Standard Guide for Fourier Transform Infrared Spectroscopy in Forensic Tape Examinations
• Effective Date: 10-Jul-2002

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation:E2224–02
Standard Guide for
1
Forensic Analysis of Fibers by Infrared Spectroscopy
This standard is issued under the fixed designation E2224; 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 (´) indicates an editorial change since the last revision or reapproval.
1. Scope 3.5 attenuated total reflection (ATR)—reflection that occurs
when an absorbing coupling mechanism acts in the process of
1.1 Infrared (IR) spectrophotometery is a valuable method
total internal reflection to make the reflectance less than unity.
of fiber polymer identification and comparison in forensic
3.6 background—apparent absorption caused by anything
examinations.The use of IR microscopes coupled with Fourier
other than the substance for which the analysis is being made.
transforminfrared(FT-IR)spectrometershasgreatlysimplified
3.7 cellulosic fiber—fiber composed of polymers formed
the IR analysis of single fibers, thus making the technique
from glucose subunits.
feasible for routine use in the forensic laboratory.
3.8 far-infrared—pertaining to the infrared region of the
1.2 This guideline is intended to assist individuals and
electromagnetic spectrum with wavelength range from ap-
laboratories that conduct forensic fiber examinations and
-1
proximately25to300µm(wavenumberrange400to30cm ).
comparisons in the effective application of infrared spectros-
3.9 Fourier transform—a mathematical operation that con-
copy to the analysis of fiber evidence. Although this guide is
verts a function of one independent variable to one of a
intended to be applied to the analysis of single fibers, many of
different independent variable. In FT-IR spectroscopy, the
its suggestions are applicable to the infrared analysis of small
Fourier transform converts a time function (the interferogram)
particles in general.
to a frequency function (the infrared absorption spectrum).
2. Referenced Documents Spectraldataarecollectedthroughtheuseofaninterferometer,
2
which replaces the monochrometer found in the dispersive
2.1 ASTM Standards:
infrared spectrometer.
E1421 Practice for Describing and Measuring Performance
3.10 Fourier transform infrared (FT-IR) spectrometry—a
of Fourier Transform Mid-Infrared (FT-MIR) Spectrom-
form of infrared spectrometry in which an interferogram is
eters: Level Zero and Level One Tests
obtained; this interferogram is then subjected to a Fourier
E1459 Guide for Physical Evidence Labeling and Related
transformation to obtain an amplitude-wavenumber (or wave-
Documentation
length) spectrum.
E1492 Practice for Receiving, Documenting, Storing, and
3.11 generic class—agroupoffibershavingsimilar(butnot
Retrieving Evidence in a Forensic Science Laboratory
necessarily identical) chemical composition. A generic name
3. Terminology
applies to all members of a group and is not protected by
trademark registration. Generic names for manufactured fibers
3.1 absorbance (A)—the logarithm to the base 10 of the
include, for example, rayon, nylon, and polyester. (Generic
reciprocal of the transmittance, (T); A = log (1/T) = -log T.
10 10
names to be used in the United States for manufactured fibers
3.2 absorption band—a region of the absorption spectrum
were established as part of the Textile Fiber Products Identifi-
in which the absorbance passes through a maximum.
3
cation Act enacted by Congress in 1954 (1).
3.3 absorption spectrum—a plot, or other representation, of
3.12 infrared—pertaining to the region of the electromag-
absorbance,oranyfunctionofabsorbance,againstwavelength,
netic spectrum with wavelength range from approximately
or any function of wavelength.
-1
0.78 to 1000 µm (wavenumber range 12 800 to 10 cm ).
3.4 absorptivity (a)—absorbance divided by the product of
3.13 infrared spectroscopy—to spectroscopy in the infrared
the sample pathlength (b) and the concentration of the absorb-
region of the electromagnetic spectrum.
ing substance (c); a = A/bc
3.14 internal reflection spectroscopy (IRS)—the technique
of recording optical spectra by placing a sample material in
1
This guide is under the jurisdiction of ASTM Committee E30 on Forensic
contact with a transparent medium of greater refractive index
Sciences and is the direct responsibility of Subcommittee E30.01 on Criminalistics.
Current edition approved July 10, 2002. Published September 2002. DOI:
10.1520/E2224-02.
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
3
Standards volume information, refer to the standard’s Document Summary page on The boldface numbers in parentheses refer to the list of references at the end of
the ASTM website. this standar
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