ASTM E3085-17

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: E3085 − 17 An American National Standard
Standard Guide for
Fourier Transform Infrared Spectroscopy in Forensic Tape
Examinations
This standard is issued under the fixed designation E3085; 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 E573 Practices for Internal Reflection Spectroscopy
E1421 Practice for Describing and Measuring Performance
1.1 Infrared spectroscopy (IR) is a valuable method for the
of Fourier Transform Mid-Infrared (FT-MIR) Spectrom-
identification and comparison of pressure sensitive tapes (1-
2 eters: Level Zero and Level One Tests
20). This guide provides basic recommendations and infor-
E1492 Practice for Receiving, Documenting, Storing, and
mation about infrared spectrometers and accessories, with an
Retrieving Evidence in a Forensic Science Laboratory
emphasis on sampling techniques specific to pressure sensitive
E2224 Guide for Forensic Analysis of Fibers by Infrared
tape examinations.The particular method(s) employed by each
Spectroscopy
examiner or laboratory will depend upon available equipment,
examiner training, sample suitability, and sample size.
3. Terminology
1.2 This guide is intended for examiners with a basic
3.1 Definitions—For terms relevant to molecular
knowledge of the theory and proficiency in the use of infrared
spectroscopy, refer to Terminology E131.
spectroscopyaswellasexperienceinthehandlingandforensic
3.1.1 background, n—the signal produced by the entire
examinationofpressuresensitivetapes.Further,thisguideisto
analytical system apart from the material of interest.
be used in conjunction with a broader analytical scheme
(21-23).
3.1.2 elastomer, n—the polymeric backbone of a pressure
sensitive adhesive imparting elastic properties, for example,
1.3 Disclaimer: This guide offers a set of instructions for
rubber.
performing one or more specific operations. This standard
cannotreplaceknowledge,skill,ortheabilityacquiredthrough
3.1.3 fiber reinforcement, n—the fabric portion of some
appropriate education, training, and experience and should be
pressure sensitive adhesive tapes; also referred to as scrim.
used in conjunction with sound professional judgment.
3.1.4 filler/extender, n—an inorganic material that is added
1.4 The values stated in SI units are to be regarded as
to a tape to modify a physical property or reduce cost.
standard. No other units of measurement are included in this
3.1.5 low e-glass, n—adichroicmirrorthatiscoatedwithan
standard.
IR reflective surface.
1.5 This standard does not purport to address all of the
3.1.5.1 Discussion—Such glass is suitable for use as a
safety concerns, if any, associated with its use. It is the
sample support when performing IR reflection techniques.
responsibility of the user of this standard to establish appro-
3.1.6 meaningful difference, n—a feature or property of a
priate safety and health practices and determine the applica-
sample that does not fall within the variation exhibited by the
bility of regulatory limitations prior to use.
comparison sample, considering the limitations of the sample
or technique, and therefore indicates the two samples do not
2. Referenced Documents
share a common origin.
2.1 ASTM Standards:
3.1.6.1 Discussion—The use of this term does not imply the
E131 Terminology Relating to Molecular Spectroscopy
formal application of statistics.
3.1.7 pressure-sensitive adhesive, n—a viscoelastic material
This guide is under the jurisdiction of ASTM Committee E30 on Forensic
which, in solvent-free form, remains tacky and will adhere
Sciences and is the direct responsibility of Subcommittee E30.01 on Criminalistics.
Current edition approved March 1, 2017. Published March 2017. DOI: 10.1520/
instantaneously to most solid surfaces with the application of
E3085-17.
very slight pressure.
The boldface numbers in parentheses refer to a list of references at the end of
this standard.
3.1.8 pressure-sensitive adhesive (PSA) tape, n—a combi-
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
nation of a pressure sensitive adhesive with a continuous
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
flexiblebacking(forexample,cloth,paper,metal,orplastic)or
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. with a backing and release liner.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E3085 − 17
3.1.8.1 Discussion—Use of the word “tape” in this guide is dependent on factors such as sample size and condition and
refers to PSA tapes and their components. is evaluated on a case-by-case basis.
3.1.9 release coat, n—an inert material with a low surface 6.4 If necessary, the tape backing can be cleaned with an
energy, applied to a backing film on the side opposite the
appropriate solvent (for example, methanol or hexane).
adhesive, that provides ease of unwind and prevents delami- Alternatively,residuecanberemovedbygentlescrapingofthe
nation or tearing.
surface. An adhesive sample can be obtained by exposing and
sampling the underlying portion.
3.1.10 tackifier, n—solid resins added to the adhesive base
polymer to impart the necessary tack and adhesion.
6.5 The infrared analysis of tapes can be carried out using
either transmission or reflection techniques. These measure-
4. Summary of Guide
ments can be taken with a variety of equipment configurations
and accessories, the most common being the use ofAttenuated
4.1 This guideline covers the analysis of tape backings and
Total Reflection (ATR) or an infrared microscope. However,
adhesives by infrared spectroscopy. It can be applied to a wide
the use of an ATR requires a larger sample size.
range of infrared spectrometers and accessory configurations.
6.6 Attenuated Total Reflection (ATR), also known as In-
4.2 Fortheinfraredanalysisofthefiberreinforcement,refer
ternal Reflection Spectroscopy (IRS), is described in Practices
to Guide E2224.
E573. For forensic tape analysis, it offers a rapid approach to
sampling a tape backing and the adhesive as virtually no
5. Significance and Use
sample preparation is necessary. Single or multiple reflection
5.1 This guide is designed to assist an examiner in the
elements may be used depending on the amount of area
selection of appropriate sample preparation methods for the
available for sampling. When only a small area is available, a
analysis, comparison, and identification of pressure sensitive
single reflection element is desirable to avoid contamination.
adhesive (PSA) tapes. If no meaningful differences are noted
6.7 Transmission microspectroscopy is possible by sam-
between the known and unknown samples regarding physical
pling a small portion of the tape component (backing, or
appearance or measurements, then IR spectroscopy should be
adhesive) and analyzing it as a thin film.
the next step in the analytical scheme.
6.8 A diamond anvil cell may be used in the bench with a
5.2 Infrared spectroscopy can provide molecular informa-
beam condenser or placed under the microscope accessory to
tion regarding major organic and inorganic components. For
analyze both the backing and the adhesive portions of tape.
various reasons, components in lesser amounts are typically
6.9 Tackifiers or plasticizers can be extracted from the
more difficult to identify unequivocally. Reasons for this
adhesive or backing using a mild solvent such as hexane or
include interference of the absorption bands of the major
acetone (20), for subsequent analysis as a thin film using
components with the less intense bands of minor components
transmission mode.
and sensitivity issues whereby the minor components are
present at concentrations below the detection limits of the
6.10 Samples being compared shall be prepared and ana-
instrument.
lyzed in the same manner.
5.3 Infrared spectroscopy can be used to obtain spectra for
7. Analysis
elucidation of the chemical composition of a tape and for
7.1 A standard mid-IR range Fourier transform infrared
comparison of two or more tape samples. When used for
(FTIR) spectrometer is acceptable to conduct the necessary
spectralcomparisons,theobjectiveistodeterminewhetherany
-1
analyses. Detector cutoff no higher than 750 cm is recom-
meaningful differences exist between the samples.
mended. A mid-infrared FTIR spectrometer with an extended
-1
range down to 200 cm is advantageous for the classification
6. Sample Handling
and comparison of inorganic fillers and pigments.
6.1 The general collection, handling, and tracking of
7.2 Instrument Parameters:
samples shall meet or exceed the requirements of Practice
7.2.1 Performance and Verification—It is essential that
E1492.
instrument performance and verification be evaluated routinely
6.2 The work area and tools used for the preparation of
(for example, monthly or before use if used less frequently).
samples shall be free of any materials that could transfer to the
7.2.2 The preferred performance evaluation method is in
sample.
accordance with Practice E1421. In brief, this includes evalu-
6.3 When analyzing difficult samples (for example, adhe- ation of the system throughput, single-beam spectrum, 100%T
sive residue, dirty samples, limited sample size, or inhomoge- line, and polystyrene reference spectrum.
neous samples), care shall be taken in sampling each available 7.2.3 Sample and background scans shall be run under the
tape layer (that is, film backing, adhesive, fiber reinforcement same instrument conditions (for example, aperture size).
if present) as well as in selection of appropriate analytical 7.2.4 Typically, 16 to 256 scans are collected at a resolution
-1
conditions. An attempt shall be made to remove extraneous of4cm or less.
material from the specimen before analysis. In order to ensure 7.2.5 When comparing spectra, the data shall be displayed
reproducibility and evaluate intra-sample variations, repeat in the same units (for example, Absorbance units, %
analysis of samples is recommended. The number of replicates Transmission, % Reflectance).
E3085 − 17
7.3 Main Bench – Transmission: has been compressed. This leaves the thin compressed film
adhering to one of the diamond faces.
7.3.1 Transmission methods generally require more exten-
sive sample preparation. The sample shall be thin enough not
7.7 Microscope Accessory – Reflection:
to over-absorb. For transmission data viewed in %
7.7.1 If samples are analyzed directly on an infrared light
transmittance, spectral peaks optimally should not fall below
reflectingsurface(forexample,lowe-glassorgoldmirror),the
10 % T. For spectra displayed in absorbance, the maximum
reflection mode can be used to produce spectra mimicking
absorbance optimally should be 1.0 or less. This typically
double-pass transmission spectra. The technique is sometimes
requires a sample thickness of approximately 5–10 µm.
referred to as “transflection” or “reflection/absorption.”
7.3.2 Sample preparation techniques that may be employed
Samples need to be approximately half the thickness of an
for transmission analysis in the main bench include backing or
optimum transmission sample.
adhesive pressed in a diamond cell, a thin backing sample
7.7.2 The FTIR microscope can also be used in the specular
stretched over an aperture, or adhesive deposited onto an alkali
reflection mode; however, it is not useful for tape unless the
halide pellet (for example, KBr, NaCl, AgCl).
surface of the sample is highly reflective.
7.8 Microscope Accessory – ATR:
7.4 Main Bench – ATR:
7.8.1 ATRobjectivesareavailableforinfraredmicroscopes.
7.4.1 ATR methods lend themselves to conducting the
Applying consistent pressure to each sample can mitigate
examination of the tape intact. Since ATR is a surface tech-
spectral variations. Intra-sample variations can result from
nique it is necessary to remove any extraneous material from
sample heterogeneity; therefore, multiple samplings shall be
the area to be examined.
conducted as feasible.
7.4.2 ATR is also useful in the analysis of duct tape
backings for layer structure evaluation as a complementary
8. Classificat
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