ASTM E3296-22

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: E3296 − 22 An American National Standard
Standard Guide for
Using Pyrolysis Gas Chromatography and Pyrolysis Gas
Chromatography-Mass Spectrometry in Forensic Polymer
Examinations
This standard is issued under the fixed designation E3296; 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.
INTRODUCTION
The forensic analysis of polymers (for example, fibers, paints and coatings, tapes and adhesives)
using pyrolysis gas-chromatography (PGC) or pyrolysis gas-chromatography/mass spectrometry
(PGC/MS) is a destructive technique that provides detailed organic chemical information about such
samples. This information augments that obtained from other analytical techniques such as Fourier
transform infrared spectroscopy (FTIR), polarized light microscopy (PLM), scanning electron
microscopy-energy dispersive X-ray spectroscopy (SEM-EDS), and X-ray fluorescence spectroscopy
(XRF).
1. Scope Development of International Standards, Guides and Recom-
mendations issued by the World Trade Organization Technical
1.1 Thisguidecoversinformationandrecommendationsfor
Barriers to Trade (TBT) Committee.
the selection and application of various PGC and PGC/MS
procedures and methods in the forensic examination of poly-
2. Referenced Documents
meric materials (for example, fibers, paint, tape). PGC and
2.1 ASTM Standards:
PGC/MS methods are used for the identification and compari-
D16 TerminologyforPaint,RelatedCoatings,Materials,and
son of the organic components of these materials. Refer to
Applications
Practice D3452 for further information on the preparation of
D123 Terminology Relating to Textiles
the pyrolysis system for polymeric analyses.
D3452 Practice for Rubber—Identification by Pyrolysis-Gas
1.2 This guide is to be used in conjunction with a broader
Chromatography
analytical scheme such as Guides E1610 or E3260,orthe
E355 Practice for Gas ChromatographyTerms and Relation-
SWGMAT Forensic Fiber Examination Guidelines.
ships
1.3 This standard is intended for use by competent forensic
E1492 Practice for Receiving, Documenting, Storing, and
science practitioners with the requisite formal education,
Retrieving Evidence in a Forensic Science Laboratory
discipline-specific training (see Practices E2917, E3233,
E1610 Guide for Forensic Paint Analysis and Comparison
E3234), and demonstrated proficiency to perform forensic
E1732 Terminology Relating to Forensic Science
casework.
E2917 Practice for Forensic Science Practitioner Training,
Continuing Education, and Professional Development
1.4 The values stated in SI units are to be regarded as
Programs
standard. No other units of measurement are included in this
E3233 PracticeforForensicTapeAnalysisTrainingProgram
standard.
E3234 Practice for Forensic Paint Analysis Training Pro-
1.5 This international standard was developed in accor-
gram
dance with internationally recognized principles on standard-
E3260 Guide for Forensic Examination and Comparison of
ization established in the Decision on Principles for the
1 2
This guide is under the jurisdiction of ASTM Committee E30 on Forensic For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Sciences and is the direct responsibility of Subcommittee E30.01 on Criminalistics. contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Current edition approved Jan. 1, 2022. Published February 2022. DOI: 10.1520/ Standards volume information, refer to the standard’s Document Summary page on
E3296-22. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E3296 − 22
Pressure Sensitive Tapes 4.2 Pyrolysis breaks a large molecule into many smaller
2.2 Other Documents: molecules in a reproducible fashion through the breaking of
ISO/IEC 17025 General requirements for the competence of bonds by means of the application of thermal energy. Analyti-
testing and calibration laboratories cal pyrolysis is used to provide chemical information on
SWGMAT Forensic Fiber Examination Guidelines organic-containing solids that cannot be dissolved or otherwise
SWGMAT Trace Evidence Quality Assurance Guidelines introduced into a chromatographic system. It is also used to
SWGMAT Trace Evidence Recovery Guidelines analyze and compare solvents bound in a solid material (such
as tape adhesives) (10). When analyzed using a separation
3. Terminology
technique such as gas chromatography, the smaller molecules
3.1 Definitions—For definitions of terms used in this guide,
produced through the action of pyrolysis form a pattern of
see Terminologies D16, D123, and E1732, and Practice E355.
separated fragments. Mass and structural information indica-
tive of the original molecule are also available when a mass
3.2 Definitions of Terms Specific to This Standard:
spectral detector is used.
3.2.1 Curie point, n—the temperature at which a ferromag-
netic metal loses its ferromagnetic properties.
4.3 Although a destructive method, and therefore often
placed at the end of an analytical scheme, the pyrograms
3.2.2 exclusionary difference, n—a difference in a feature or
produced from different polymer compositions form character-
property between compared items that is substantial enough to
istic patterns that are useful for both identification of polymer
determine that they did not originate from the same source.
type and comparisons between samples (4, 6, 9-23). When
3.2.3 interface temperature, n—the temperature of the
usedforcomparisonpurposes,thegoalistodeterminewhether
heated zone between the pyrolysis unit and the GC.
any exclusionary differences exist between the samples.
3.2.4 pyrogram, n—a chromatogram obtained from the
pyrolysis products of a material.
5. Sample Handling
3.2.5 pyrolysis, n—the thermal fragmentation of a substance
5.1 General Considerations:
in an inert atmosphere.
5.1.1 Practice E1492 as well as the relevant portions of the
3.2.6 pyrolysis temperature, n—the temperature (set or
SWGMAT Trace Evidence Quality Assurance Guidelines and
ramped) at which the pyrolysis of the sample is performed.
Trace Evidence Recovery Guidelines are followed for the
general collection, handling, documentation, and tracking of
3.2.7 pyrolyzate, n—the product of the pyrolysis process.
specimens and samples.
3.2.8 traceable reference standard, n—a sample acquired or
5.1.2 Since PGC is a destructive technique, considerations
preparedwithdocumentedoriginthathasknownpropertiesfor
aremadepriortoanalysistoensurethattheentiresampleisnot
the purpose of calibrating equipment and/or for use as a
consumed.
control.
5.1.3 Prior to sampling, any foreign debris or contaminants
4. Significance and Use
that are visually observed by stereomicroscopy should be
scraped away or otherwise removed.
4.1 This guide provides guidance in the selection of appro-
5.1.4 Except where sample size or condition makes it
priatesamplepreparationmethodsandinstrumentalparameters
prohibitive, samples for PGC or PGCMS analysis are prepared
for the analysis, comparison, or identification of various
in a manner that permits resolution and analysis of individual
polymeric materials by PGC and PGC/MS.
layers. This allows the organic components from each layer to
4.1.1 PGC/MS can differentiate between classes of fibers
be effectively characterized and attributed to the appropriate
(for example, acrylic, polyester, nylon) and within classes of
layer. When samples are too small to isolate individual layers,
fibers (for example, acrylics) (1-3).
samples from multiple layers can be analyzed simultaneously.
4.1.2 Paint binders are differentiated based upon the variety
Samples for comparison are prepared under the same condi-
of monomers used in paint formulations which could be
tions and in the same manner whenever possible.
difficult to identify by other analytical techniques. In addition,
5.1.5 Sample size can vary in accordance with polymer
some additives can be detected or identified.
type, pyrolysis method, column type, chromatographic
4.1.3 Differentiation can be achieved by the separation and
conditions, and detection methods. As a general approach,
identification of organic components in the adhesive portion of
varying amounts of a known polymeric material can be
tapes (4, 5) and in the backings of electrical tapes (6).
analyzed to determine the minimum amount that provides
4.1.4 PGC/MS can provide additional discrimination for
sufficient signal to identify the characteristic components.
other types of polymers such as automotive lenses, automotive
Once optimal sample size is determined, samples of similar
body fillers, cosmetics, plastics, and rubbers (7-9).
size and shape should be used for analyzing replicates and for
comparison purposes. Instrument manufacturer recommenda-
Available from International Organization for Standardization (ISO), ISO
tions and published studies of like materials can be used for
Central Secretariat, Chemin de Blandonnet 8, CP 401, 1214 Vernier, Geneva,
Switzerland, https://www.iso.org.
guidance in determining approximate sample size.
Available from Scientific Working Group for Materials Analysis (SWGMAT),
5.1.6 Samples are positioned on or within appropriate
http://swgmat.org.
5 sample holders to maximize pyrolysis. More specific guidance
The boldface numbers in parentheses refer to a list of references at the end of
this standard. on sample holders is discussed in 6.7.1.
E3296 − 22
5.2 Fibers: 6.2.2.2 An electron ionization source is recommended in-
5.2.1 Pyrolysis should be conducted on individual fibers, steadofachemicalionizationsourceforapplicationsdiscussed
when possible. Optimal results are obtained from fiber lengths in this guide.
of 1–2 cm, although fibers as small as a few mm in length can 6.2.3 Reconstructed total ion chromatograms in PGC/MS
be analyzed. As little as 25–30 µg has been reported to be
look similar to PGC chromatograms and provide comparable
sufficient for some acrylic fibers (1). information to conventional PGC analysis.
5.3 Paint:
6.3 Pyrolysis Systems:
5.3.1 Suitable paint sample sizes for pyrolysis range from
6.3.1 Three different types of pyrolyzers are available: (1)
5–150 µg (21, 24). Generally, more sample should be used
resistively-heated, (2) Curie point/inductively-heated, and (3)
when the layer is heavily filled with inorganic material.
microfurnace.
6.3.2 Inresistively-heatedpyrolysis,thecoilheatsfirst,then
5.4 Tape:
transfers the heat through the sample holder (for example,
5.4.1 Suitable tape sample sizes for pyrolysis range from
quartztube)andheatsthesample (27).Temperaturerampingis
10–60 µg, depending on the type of tape as well as the
possible and the desired temperature can be selected by
chemical composition of the material (for example, amount of
controlling the current.The coil reaches its final temperature in
inorganic filler, type of elastomer). A 0.5 mm square of
1–2 seconds; however, it can take several seconds for the
electrical tape has been reported to correspond to approxi-
sample to pyrolyze for a total wait time close to 10 seconds.
mately 25 µg (21).
Some drawbacks are that coil probes can exhibit “cold spots”
5.4.2 Adhesive can be removed from tape for analysis using
and the coil is slow to heat the thermal mass of the quartz tube
several methods. When preparing the adhesive for analysis,
when compared with other pyrolysis systems.
care should be taken to make sure any reinforcement materials
6.3.3 With inductively-heated or Curie point pyrolysis, the
(that is, fibers) are not present in the sample.
5.4.3 The tape backing can be isolated for analysis by sample is either coated on or placed in a ferromagnetic wire,
ribbon, or boat. The type of wire, ribbon, or boat that is used
removing the adhesive using a metal probe, a scalpel, an
appropriate solvent, or a combination of these methods. determines the maximum temperature that can be reached.
Different alloy compositions are available for a wide range of
Alternately, a thin peel of the tape backing can be used. The
thinpeelshouldonlybeusedifthebackingisknowntoconsist temperatures. Temperature ramping is not an option with this
technique.
of a single layer polymer.
6.3.4 Microfurnace pyrolyzers use a quartz or metal cup to
5.5 Other Polymeric Materials:
introduce the sample into the heated analytical chamber
5.5.1 Suitable sample sizes for pyrolysis of other polymeric
(microfurnace). The microfurnace is typically held at a single
materials generally range from 10–100 µg (25), with automo-
temperature without the need for equilibration; this allows for
tive lens and rubber samples closer to 100 µg and cosmetic
greater reproducibility than observed with other pyrolysis
samples approximately 25–50 µg (7, 16, 26).
systems.Thethermalmassofthecupisnegligiblecomparedto
the microfurnace, so the cup and sample reach the set tempera-
6. Instrumentation and Operating Conditions
ture nearly instantaneously.
6.1 PGC instrumentation consists of two distinct compo-
6.4 Pyrolysis Temperature:
nents: (1) the pyrolysis unit, where sample fragmentation
6.4.1 The pyrolysis unit should use a temperature that
occurs, and (2) the gas chromatograph where separation and
results in complete pyrolysis without causing excessive bond
detectionofthepyrolyzatefragmentsoccur.Ininstanceswhere
breakage or fragmentation. Excessive fragmentation leads to a
amassspectrometeristhedetector,itisconsideredtobeathird
commonality of fragmentation data in the resulting pyrogram
distinct part of the instrument, as it aids in the identification of
and difficulties in classification, identification, or discrimina-
selected pyrolyzates. Some systems include an interface be-
tion.
tween the pyrolysis unit and the gas chromatograph.
6.4.2 The same analysis conditions (for example, set point,
6.2 The two most common detectors for use with PGC
heating rate, time) are used for samples being compared.
includetheflameionizationdetector(FID)andmassspectrom-
6.5 Instrument Operating Parameters:
eter (MS).
6.5.1 Operating conditions (for example, time, column
6.2.1 The FID is capable of detecting a broad range of
selection, temperature programming) are optimized for
combustible pyrolyzates. It is relatively inexpensive and has a
pyrolysis, chromatographic separation, and detection. As the
large linear dynamic range. Identifications and comparisons
analyst determines specific analytical needs, actual operating
with data from an FID are based on retention times of peaks
conditions can vary. Variation of the operating values is
and the appearance of overall pyrogram patterns.
permitted. The choice of conditions is based on the quality of
6.2.2 The MS provides information about the individual
pyrogramsproducedwithregardtopeakseparation,resolution,
fragments of the pyrolyzates, which enhances the ability to
and reproducibility.
chemically classify the different polymer components. By
6.5.2 Inlet Temperature—Typical inlet temperatures range
selecting ions of interest, classes of compounds are able to be
from 200–300 °C.
selectively viewed and searched for specific compounds.
6.2.2.1 Various types of mass spectrometers are available 6.5.3 Split Ratio—The sample introduced into the instru-
for use as GC detectors. ment is split so that neither the column nor detector are
E3296 − 22
saturated by the sample. Typical split ratios range from 20:1 to 6.7.2 Blanks:
100:1, depending on sample size.
6.7.2.1 Asystem blank is run using all aspects of the system
6.5.4 Oven parameters are critical for separation of pyro-
prior to every case sample to ensure that there is no contami-
lyzates. Oven temperature, ramp rates, co
...