ASTM D8401-24

Standard Test Method for Identification of Polymer Type and Quantity of Microplastic Particles and Fibers in Waters with High to Low Suspended Solids Using Pyrolysis-Gas Chromatography/Mass Spectrometry

SIGNIFICANCE AND USE
5.1 Preliminary studies have identified polymeric organic compounds as contaminants in treated drinking water, wastewater, surface water, ground water, and marine waters. These polymers may be harmful to the environment and adversely affect human health, and in these circumstances, mass estimation is commonly required. A universal, analytical method will help to normalize data from around the world and better understand which polymers are most frequently found in various climatic and geological locations (5-7). Pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) has many advantages in that both polymer identification and mass quantification can be easily accomplished by chromatographic separation in combination with mass spectral analysis.
SCOPE
1.1 In this pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) test method, an analytical protocol validated specifically for the analysis of water with high to low suspended solids is described. This test method will standardize the identification and simultaneous quantitation of organic polymer particles and fibers in water. It has been designed for and applies to all microplastic particles and fibers, and is intended for use with treated drinking water, surface waters, wastewater influent and effluent (secondary and tertiary), and marine waters. This test method is not limited to these particular water matrices; however, the applicability of this test method to other aqueous matrices shall be demonstrated.  
1.2 Microgram quantities of a sample containing microplastics are pyrolyzed (Py) at 600 °C. The pyrolyzates are separated on an analytical column (GC) and detected using a 70-eV electron impact mass spectrometer (MS). Polymers often have similar pyrograms, making it difficult to differentiate the pyrolyzates for a given polymer from those of the composite sample. In this test method, ion ratios at predetermined retention times to facilitate the identification of each polymer present in a sample containing microplastics are compared.  
1.3 This test method is to be used in conjunction with Practices D8332, D8333, and D8402. These ASTM International standards enable the collection and preparation of water samples with high, medium, or low suspended solids for the identification and quantification of microplastic particles and fibers without compromising the integrity of the microplastics. This test method is applicable to microplastic fibers and particles, including sizes defined as a nanoparticle; this is a natural extension of this test method because Py-GC/MS technology responds to the total mass of the sample independent of individual particle sizes. The uniformity of particle size influences the reproducibility of the pyrogram and samples with microplastics should be reduced to a fine powder with the final particle size diameter on the order of less than 0.2 mm.  
1.4 It is the responsibility of the user to ensure the validity of this test method for untested matrices.  
1.5 Units—The values stated in SI units are to be regarded as the standard. No other units of measurement are included in this standard.  
1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.7 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.

General Information

• Status: Published
• Publication Date: 29-Feb-2024
• Technical Committee: D19 - Water
• Drafting Committee: D19.06 - Methods for Analysis for Organic Substances in Water

Overview

ASTM D8401-24: Standard Test Method for Identification of Polymer Type and Quantity of Microplastic Particles and Fibers in Waters with High to Low Suspended Solids Using Pyrolysis-Gas Chromatography/Mass Spectrometry (Py-GC/MS) provides a globally harmonized analytical protocol for the identification and quantification of microplastic contaminants in a wide variety of water matrices. Developed by ASTM International, this method addresses the critical need for reliable microplastics analysis in water by leveraging the advanced capabilities of pyrolysis-gas chromatography/mass spectrometry, allowing both polymer identification and mass estimation in environmental and drinking water samples.

This standard supports laboratories, environmental monitoring agencies, and water utilities in generating reproducible, comparable datasets for microplastic pollution, thus facilitating regulatory compliance, risk assessment, and public health protection.

Key Topics

• Microplastic Analysis in Diverse Waters:
  Applies to treated drinking water, surface water, wastewater influent and effluent (secondary and tertiary), and marine waters with a range of suspended solids.

• Polymer Identification and Quantification:
  Employs Py-GC/MS to thermally degrade microplastics, separate their pyrolyzates, and identify polymers based on characteristic mass spectra and retention times.

• Standardization of Sample Preparation:
  Recommends pre-treatment steps such as size reduction to <0.2 mm, drying, and homogenization to ensure reproducibility.

• Calibration and Quality Control:
  Utilizes internal and external calibration standards and emphasizes ongoing instrument performance verification.

• Comprehensive Coverage:
  Validated for major polymers found as microplastics, with flexibility for laboratories to extend validation to additional polymers or matrices if needed.

Applications

ASTM D8401-24 is valuable for organizations involved in:

• Environmental Monitoring:
  Enables detection and mass quantification of microplastic contamination in rivers, lakes, groundwater, and marine ecosystems, supporting pollution studies and ecological risk assessments.

• Drinking Water Safety:
  Assures water utilities and regulatory bodies of compliance with guidelines by facilitating the identification and measurement of microplastic particles in treated water.

• Wastewater Treatment Assessment:
  Assists facilities in quantifying microplastic removal efficiencies by comparing influent and effluent concentrations.

• Research and Public Health:
  Provides researchers with a robust method to analyze the occurrence, distribution, and potential health impacts of microplastics in various water environments.

• Global Data Harmonization:
  Standardized methodology allows for inter-laboratory and international comparison of microplastic data, supporting global efforts to address plastic pollution.

Related Standards

The effectiveness and reliability of ASTM D8401-24 are strengthened by its integration with several related ASTM standards, including:

• ASTM D8332: Practice for Collection of Water Samples with High, Medium, or Low Suspended Solids for Identification and Quantification of Microplastic Particles and Fibers
• ASTM D8333: Practice for Preparation of Water Samples with High, Medium, or Low Suspended Solids for Identification and Quantification of Microplastic Particles and Fibers
• ASTM D8402: Practice for Development of Microplastic Reference Samples for Calibration and Proficiency Evaluation
• ASTM E355: Practice for Gas Chromatography Terms and Relationships
• ASTM D1193: Specification for Reagent Water
• EPA SW-846: Hazardous Waste Test Methods
• TNI GUID-3-110-Rev0: TNI Guidance on Instrument Calibration

Practical Value

ASTM D8401-24 offers laboratories and stakeholders a validated, universal test method tailored for real-world water samples with a wide range of suspended solids. Its adoption enables:

• Greater consistency and reliability in microplastic quantification
• Facilitation of regulatory compliance and environmental stewardship
• Enhanced understanding of microplastic contamination across different water systems

By applying standardized Py-GC/MS analysis, the method sets a benchmark for accurate, reproducible microplastic polymer identification and supports data-driven environmental and public health decision making.

Standards Content (Sample)

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: D8401 − 24
Standard Test Method for
Identification of Polymer Type and Quantity of Microplastic
Particles and Fibers in Waters with High to Low Suspended
Solids Using Pyrolysis-Gas Chromatography/Mass
Spectrometry
This standard is issued under the fixed designation D8401; 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 influences the reproducibility of the pyrogram and samples
with microplastics should be reduced to a fine powder with the
1.1 In this pyrolysis-gas chromatography/mass spectrom-
final particle size diameter on the order of less than 0.2 mm.
etry (Py-GC/MS) test method, an analytical protocol validated
specifically for the analysis of water with high to low sus- 1.4 It is the responsibility of the user to ensure the validity
pended solids is described. This test method will standardize of this test method for untested matrices.
the identification and simultaneous quantitation of organic
1.5 Units—The values stated in SI units are to be regarded
polymer particles and fibers in water. It has been designed for
as the standard. No other units of measurement are included in
and applies to all microplastic particles and fibers, and is
this standard.
intended for use with treated drinking water, surface waters,
1.6 This standard does not purport to address all of the
wastewater influent and effluent (secondary and tertiary), and
safety concerns, if any, associated with its use. It is the
marine waters. This test method is not limited to these
responsibility of the user of this standard to establish appro-
particular water matrices; however, the applicability of this test
priate safety, health, and environmental practices and deter-
method to other aqueous matrices shall be demonstrated.
mine the applicability of regulatory limitations prior to use.
1.2 Microgram quantities of a sample containing microplas-
1.7 This international standard was developed in accor-
tics are pyrolyzed (Py) at 600 °C. The pyrolyzates are sepa-
dance with internationally recognized principles on standard-
rated on an analytical column (GC) and detected using a 70-eV
ization established in the Decision on Principles for the
electron impact mass spectrometer (MS). Polymers often have
Development of International Standards, Guides and Recom-
similar pyrograms, making it difficult to differentiate the
mendations issued by the World Trade Organization Technical
pyrolyzates for a given polymer from those of the composite
Barriers to Trade (TBT) Committee.
sample. In this test method, ion ratios at predetermined
retention times to facilitate the identification of each polymer
2. Referenced Documents
present in a sample containing microplastics are compared.
2.1 ASTM Standards:
1.3 This test method is to be used in conjunction with
D883 Terminology Relating to Plastics
Practices D8332, D8333, and D8402. These ASTM Interna-
D1129 Terminology Relating to Water
tional standards enable the collection and preparation of water
D1193 Specification for Reagent Water
samples with high, medium, or low suspended solids for the
D2777 Practice for Determination of Precision and Bias of
identification and quantification of microplastic particles and
Applicable Test Methods of Committee D19 on Water
fibers without compromising the integrity of the microplastics.
D8332 Practice for Collection of Water Samples with High,
This test method is applicable to microplastic fibers and
Medium, or Low Suspended Solids for Identification and
particles, including sizes defined as a nanoparticle; this is a
Quantification of Microplastic Particles and Fibers
natural extension of this test method because Py-GC/MS
D8333 Practice for Preparation of Water Samples with High,
technology responds to the total mass of the sample indepen-
Medium, or Low Suspended Solids for Identification and
dent of individual particle sizes. The uniformity of particle size
Quantification of Microplastic Particles and Fibers Using
This test method is under the jurisdiction of ASTM Committee D19 on Water
and is the direct responsibility of Subcommittee D19.06 on Methods for Analysis for For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Organic Substances in Water. contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
Current edition approved March 1, 2024. Published April 2024. DOI: 10.1520/ Standards volume information, refer to the standard’s Document Summary page on
D8401-24. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D8401 − 24
Raman Spectroscopy, IR Spectroscopy, or Pyrolysis- spectrometry (Py-GC/MS) unit located at the column inlet and
GC/MS uses temperature to narrow the initial bandwidths of the sample
D8402 Practice for Development of Microplastic Reference vapors.
Samples for Calibration and Proficiency Evaluation in All
3.2.5.1 Discussion—While cryo-trapping is commonly used
Types of Water Matrices with High to Low Levels of
with sample introduction devices such as thermal desorption
Suspended Solids
units that slowly introduce volatile compounds to a GC or
E177 Practice for Use of the Terms Precision and Bias in
GC/MS, it is not needed or recommended for this test method
ASTM Test Methods
because of the high speed in which the polymer sample is
E355 Practice for Gas Chromatography Terms and Relation-
introduced into the column.
ships
3.2.6 effluent, n—any stage of treated wastewater.
E691 Practice for Conducting an Interlaboratory Study to
3.2.7 extracted ion chromatogram, EIC, n—plot of detector
Determine the Precision of a Test Method
response for a specified ion versus elution time.
E2456 Terminology Relating to Nanotechnology
3.2.7.1 Discussion—The EIC is a graph of signal intensity
2.2 EPA Standard:
versus time for a single mass to charge (m/z) or a range of
SW-846 Hazardous Waste Test Methods
masses. In typical use, this is a subset of the total ion
2.3 TNI Standard:
chromatogram (TIC) in which all the mass ions detected are
GUID-3-110-Rev0 TNI Guidance on Instrument Calibra-
plotted together in a single two-dimensional (2D) graph of
tion
signal versus time. Further detail on this definition can be
found in Refs 2 and 3. The most general term for this EIC type
3. Terminology
of plot was “mass chromatogram” as defined by Ron Hites in
3.1 Definitions—For definitions of terms used in this test
1970 (4). Later, it was recognized that the mass chromatogram
method, refer to Terminologies D883 and D1129 and Practice
may include other ions (for example, multiple charged ions)
E355.
that contribute toward the actual ion current detected by the
MS. The term “extracted ion current” chromatogram or EIC
3.2 Definitions of Terms Specific to This Standard:
has been in common use for many decades. Sometimes, EIC is
3.2.1 backflush, n—practice of reversing the flow through
also defined as “extracted ion chromatogram.” Although other
(1) the analytical column at the column connection or (2) a
acronyms will be found in the literature such as XIC, in this
pre-column located between the injection port and the column.
test method, the more common acronym EIC is used for this
3.2.1.1 Discussion—This practice prevents high boiling
2D plot.
sample constituents from entering and perhaps contaminating
the column, which significantly reduces sample analysis cycle
3.2.8 field replicates, n—two or more separate samples
time. (1)
collected according to the collection protocol for that sample
collection, placed under identical circumstances and treated
3.2.2 calibration factor, CF, n—area/concentration of the
exactly the same throughout field and laboratory procedures.
polymer-specific ion in the pyrogram versus the amount of the
standard, evaluated from a plot. 3.2.8.1 Discussion—The analysis of field replicates dupli-
3.2.2.1 Discussion—CF is often referred to as response cates provides an indication of the precision associated with
factor (RF) when there is an internal standard calibration. sample collection, preservation, and storage, as well as labo-
ratory procedures.
3.2.3 calibration reference standard, CRS, n—mixture or
solution prepared from the primary polymer standards.
3.2.9 influent, n—raw sewage entering a wastewater treat-
3.2.3.1 Discussion—Calibration reference standards are
ment facility.
used to calibrate the instrument response with respect to
3.2.10 laboratory replicates, n—two or more sample ali-
analyte amount.
quots taken from the same homogenous sample in the analyti-
3.2.4 continuing calibration check (CCC) sample, n—25 μg
cal laboratory and analyzed separately using identical proce-
of polystyrene (PS) is commonly used as the representative
dures.
polymer to monitor system performance.
3.2.10.1 Discussion—Analysis of laboratory replicates
3.2.4.1 Discussion—A CCC shall be run and analyzed after
gives an indication of the precision associated with laboratory
the analysis of every 20 field samples. This sample is often
procedures but not with sample collection as described in
referred to as a CCC.
Practice D8332, post-collection preparation as described in
3.2.5 cryo-trap, n—device also known as a “cold-trap” Practice D8333, preservation, or storage procedures.
frequently attached to a pyrolysis-gas chromatography/mass
3.2.11 linear dynamic range, n—concentration range over
which an ion signal is linear with analyte concentration.
3 3.2.12 microplastic, n—any solid, synthetic, organic, poly-
Available from United States Environmental Protection Agency (EPA), William
meric material to which chemical additives or other substances
Jefferson Clinton Bldg., 1200 Pennsylvania Ave., NW, Washington, DC 20460,
http://www.epa.gov.
may have been added, which are particles <5 mm in their
Available from The Nelac Institute, PO Box 2439, Weatherford, TX 76086,
largest dimension and fibers no longer than 15 mm in length
https://nelac-institute.org/docs/guidance/21666708.pdf.
with an aspect ratio of at least 30:1 and <500 μm in its smallest
The boldface numbers in parentheses refer to a list of references at the end of
this standard. dimension. D8332, D8333
D8401 − 24
3.2.13 MQ water, n—water that has been purified using peaks by combining retention indices and spectral library
resin filters and deionized to a high degree by a water search results is common in many laboratories.
purification system and typically characterized as a
3.2.22 retention time, RT, n—measure of the time required
18.0 Mohm.cm at 25 °C water (Specification D1193, Type 1
for a solute to pass through a chromatographic column and
laboratory water).
defined as the time from injection to the apex of the chromato-
graphic “peak.”
3.2.14 nanoparticle, n—in nanotechnology, a subclassifica-
tion of ultrafine particle with lengths in two or three dimen-
3.2.23 sample cup, n—vessel made from deactivated stain-
sions greater than 0.001 μm (1 nm) and smaller than about
less steel, quartz, or quartz-coated glass in which the sample is
0.1 μm (100 nm), and that may or may not exhibit a size-
placed before pyrolysis.
related intensive property.
3.2.24 surface waters, n—water body with its surface in
3.2.14.1 Discussion—This term is a subject of controversy
contact with the ambient atmosphere and examples include
regarding the size range and presence of a size-related prop-
lakes, rivers, and streams.
erty. Current usage emphasizes size and not properties in the
3.2.25 suspended solids, n—all matter that remain in sus-
definition. The length scale may be a hydrodynamic diameter
pension in water media and are removed by a 0.45 μm filter.
or a geometric length appropriate to the intended use of the
nanoparticle. E2456
4. Summary of Test Method
3.2.15 pyrogram, n—plot of detector (MS) response signal
4.1 This analytical test method has been developed specifi-
to elution time, often referred to as a TIC.
cally for water samples with high to very low suspended solids.
It has been designed for and applies to all microplastic particles
3.2.16 pyrolyzer, n—device that heats a sample for the
and fibers regardless of polymer type and has been validated
purpose of performing pyrolysis.
for use with treated drinking water, surface waters, wastewater
3.2.16.1 Discussion—The term pyrolyzer can be used syn-
influent and effluent (secondary and tertiary), and marine
onymously with furnace or another heater type to describe this
waters for those polymer types identified in Table 1.
device; this includes filament-based, curie point-based, and
furnace-based pyrolyzer technologies.
4.2 This test method is used in conjunction with the collec-
tion and preparation practices of Practices D8332, D8333, and
3.2.17 pyrolysis, Py, n—sudden thermal degradation of or-
D8402.
ganic compounds.
4.3 Microgram quantities of a sample containing microplas-
3.2.17.1 Discussion—The sample shall be “heated” (to a
tics are pyrolyzed (Py) at 600 °C. The pyrolyzates are sepa-
temperature high enough to break covalent bonds) instanta-
rated on an analytical column (GC) and detected using a 70 eV
neously in an inert atmosphere. The sample path shall be inert
electron impact MS (SW-846) (5-8). Polymers often have
and at a uniform elevated temperature. The sample shall be at
similar pyrograms making it difficult to differentiate the pyro-
ambient temperature in an inert atmosphere before pyrolysis.
lyzates for a given polymer from those of the composite
3.2.18 reactive pyrolysis, RxPy—thermal hydrolysis fol-
sample; comparing ion ratios at predetermined retention times
lowed by methylation of acidic functionality on reactive
will often facilitate the identification of each polymer present
molecules.
in the sample containing microplastics. Various software algo-
3.2.18.1 Discussion—Reactive pyrolysis is the breakdown
rithms are used to simplify the complex chromatogram com-
of a sample under thermolysis in the presence of a chemical
monly associated with a multi-polymer pyrogram.
reactant added to that sample. This can be, but is not limited to,
4.4 Methyl Eicosanoate (Me-Eic) is added to all samples as
methanolysis by for example, tetramethylammonium hydrox-
an analytical check standard. Me-Eic is used not as a surrogate
ide (TMAH). The compound, CaCO , is a solid, and when
nor an internal standard (ISTD) but as an indicator of the
present in the sample cup, reactive pyrolysis can be induced in
analytical quality of each injection. It monitors the quality of
specific pyrolzates.
the analysis of the GC/MS instrument because the Me-Eic
3.2.19 relative standard deviation, RSD, n—is expressed in
molecule is a thermally and chemically stable compound. It is
percent and is obtained by multiplying the standard deviation
not degraded at typical pyrolysis temperatures, and it does not
by 100 and dividing this product by the average.
react with pyrolyzates from polymers.
3.2.19.1 Discussion—RSD compares the standard deviation
4.5 In Table 1, the polymers and reference ions used to
with the mean of the given data set and tells you whether the
validate this test method are listed. This test method is not
“regular” standard deviation is small or large when compared
limited to the polymers listed in the table; however, the
to the mean of the given data set.
applicability of this test method to polymers not listed shall be
3.2.20 response factor, RF, n—the area/weight of the
demonstrated (see 4.9 – 4.11 and Section 6). If desired, particle
polymer-specific ion in the pyrogram versus the amount of
size, shape, or surface features, or combinations thereof, may
standard analyzed, evaluated with a plot.
be noted before analysis using appropriate instrumentation,
such as scanning electron microscopy or infrared (IR) and
3.2.21 retention indices, RI, n—relative retention times
Raman spectroscopy.
normalized to closely eluting n-alkanes.
3.2.21.1 Discussion—Retention indices are system- 4.6 For the proper pyrolysis of a sample and to enable an
independent and exhibit long-term reproducibility. Identifying accurate determination of the mass of microplastics in the
D8401 − 24
TABLE 1 Polymers Validated for This Test Method
Compound Primary Quantitation Ion Polymer Identification (Ion) Representatives
(Abbr.) (Name, Abbr.)
Polyethylene (PE) 82 (1,20-Heneicosadiene, C21”) C10’, C14’, C21”
Polypropylene (PP) 126 (2,4-Diemthyl-1-heptene, C9’) C9’, C12’, C15’
Polyvinylchloride (PVC) 128 (Naphthalene, Naph) Naphthalene, Indene, 3-methyl Indene
A
4-tert-Butylphenol, Bisphenol A
Polycarbonate (PC) 134 (4-Isopropenylphenol, IPP)
4-Isopropenylphenol
Polyethylene terephthalate (PET) 182 (Benzophenone, BP) Benzophenone
Poly (methyl methacrylate) (PMMA) 100 (Methyl methacrylate, MMA) Methyl methacrylate
ε-Caprolactam,
Nylon-6 (N-6) 113 (ε-Caprolactam, Capro)
N-(5-cyanopentyl)hex-5-anamide
Polystyrene (PS) 91 (Styrene trimer, SSS) Styrene monomer, Styrene dimer, Styrene trimer
Styrene monomer,
Acrylonitrile-butadiene-styrene copolymer (ABS) 170 (2-Phenethyl-4-phenylpent-4-enenitrile, SAS)
2-Phenethyl-4-phenylpent-4-enenitrile
4-Vinylcyclohexene, SB (C12H14, hybrid dimer), SBB
Styrene-butadiene rubber (SBR) 54 (4-Vinylcyclohexene, VCH)
B
(C16H12 hybrid trimer)
C
Nylon-6,6 (N-66) 84 (Cyclopentanone, CP) Cyclopentanone, hexane-1,6-diamine
MDI-Polyurethane (PU) 198 (4,4’-Methylenedianiline, MDA) 4,4-Methylenedianiline
Reference (Ref) 326 (Methyl Eicosanoate, Me-Eic) Methyl Eicosanoate
A
BPA (bisphenol A) is a polar compound and it would be more susceptible to analytical deviations due to a less-than-optimally-performing system, from gradual column
degradation or possible system contamination. IPP (4-Isopropenylphenol) is a less polar compound and more robust in this analytical method.
B
Terminology for SB (C12H14) and SBB (C16H12) includes “S” for styrene and “B” for butadiene for this hybrid dimer and trimer.
C
DA (hexane-1,6-diamine) could be used for identification. However, DA is a very polar compound and susceptible to analytical deviations due to a less-than-optimally
performing system from gradual column degradation or possible system contamination.
sample cup, some samples may require additional pretreatment 4.9 The concentration of each identified polymer is deter-
beyond that described in Practice D8333 and Section 11. mined using either internal or external standard calibration
Samples may include large pieces that need to be reduced in
procedures (1). Data presented in support of this test method
size or may be excessively wet and need to be dried. In these (Fig. 1) was determined using external standard calibration
instances, the additional pretreatment might be as simple as
procedures (15.1) and collected using a 13 min backflush of the
crushing, filtration, drying, or solvation of the sample. Prepared pre-column (1). Back-flushing of the pre-column is strongly
sample homogeneity is essential.
recommended because it is an integral function of the separa-
tion process that reduces contamination of the analytical
4.7 A known amount of prepared sample is placed in a clean
column, which reduces sample-to-sample cycle time.
pyrolysis vessel such as a deactivated cup or quartz capillary
tube and automatically purged with helium to remove oxygen
4.10 Each polymer is identified based on the presence of a
before pyrolysis. Any pyrolysis GC/MS system combination
preselected pyrolyzate (that is, target compound) at a known
may be used that meets the performance specifications and
retention time in the sample pyrogram and confirmation of the
system settings in this test method. The vessel (sample cup) is
specific reference compounds. In Table 2, the target com-
inserted into the 600 °C environment of the pyrolyzer so that
pounds and other ions used to identify each of the twelve target
the polymers are instantaneously thermally degraded (“pyro-
polymers are identified. For example, in the case of Nylon-6
lyzed”). In practice, the larger the surface area to mass ratio the
(N-6), it is identified and quantified based on the presence or
more instantaneous the degradation and the more reproducible
absence of ε-Caprolactam, m/z = 113 amu, at a retention time
the pyrogram. The smaller the diameter of microplastic par-
of 10.76 min. If N-6 is not present in the polymeric sample,
ticles and fibers, the higher the surface-area/mass ratios; thus,
ε-Caprolactam will not be present in the sample pyrogram.
analytical precision is high. Note that the uniformity of particle
4.11 The choice of target compound for each polymer is
diameter influences the reproducibility of the pyrogram; the
based upon its uniqueness in the pool of pyrolyzates created by
sample should be reduced to a fine powder using a cryogenic
all polymers (and non-polymeric contaminants) in the sample,
mill with the final particle diameter on the order of less than
and discretion is necessary in its selection. For example,
0.2 mm.
benzene is present in the pyrogram of the twelve polymer
4.8 The pyrolyzates are flushed from the pyrolysis tube into
mixture in Fig. 1, but it is not used as a target compound.
a GC column via a deactivated needle fixed in a split injection
Benzene is a pyrolyzate found in the pyrograms of many types
port. The column is interfaced to a MS. The pyrolysis and
of polymers, and because the benzene peak in the pyrogram is
sample introduction process is fast and there is no need to
the sum of all the benzene formed when the twelve polymer
cryo-trap at the head of the column (see Appendix X7). The
mixture is pyrolyzed, it cannot be definitively assigned as a
GC column is temperature-programmed to separate the ana-
target compound to a specific polymer.
lytes (that is, pyrolyzates) formed by the thermal degradation
of the polymer and detected by the MS. A plot of signal versus 4.12 This is a test method for identifying and quantifying
retention time is called a pyrogram, and a plot of the total MS polymers on the list of twelve with the provision for qualifying
signal versus time is often referred to as a TIC. A plot of the additional polymers specific to one’s interest (Section 6). The
detector response from a single ion (m/z) versus time is process of polymer identification begins with confirmation of
generated, and this plot is referred to as an EIC. the target compound followed by confirmation of the specific
D8401 − 24
FIG. 1 Typical Pyrogram (TIC) of the Twelve Target Polymers
TABLE 2 Polymers and Their Associated Target Ion Information (9)
Polymers Target Compound m/z R.T.
Name Abbr. Name Abbr. Measure Other Ions M.W. (min.)
1,20-
Polyethylene PE C21” 82 41, 55, 97 208 14.67
Heneicosadiene
2,4-Dimethyl-1-
Polypropylene PP C9’ 126 43, 55, 70 126 6.62
heptene
Polyvinylchloride PVC Naphthalene Naph 128 102 128 10.17
4-Isopropenyl-
Polycarbonate PC IPP 134 91, 119 134 10.83
phenol
Polyethylene
PET Benzophenone BP 182 51, 77, 105 182 13.26
terephthalate
Polymethyl Methyl
PMMA MMA 100 69, 41, 99 100 5.17
methacrylate methacrylate
Nylon-6 N-6 ε-Caprolactam Capro 113 30, 55, 85 113 10.76
Polystyrene PS Styrene trimer SSS 91 117, 207, 312 312 17.63
Acrylonitrile 2-Phenethyl-4-
butadiene styrene ABS phenylpent-4- SAS 170 91, 115, 118 261 15.68
copolymer enenitrile
Styrene-butadiene
SBR 4-Vinylcyclohexene VCH 54 79, 66, 108 108 6.68
rubber
Nylon-6,6 N-66 Cyclopentanone CP 84 39, 55, 56 84 6.38
4-4’-
Polyurethane PU MDA 198 106, 182, 197 198 15.58
Methylenedianiline
Methyl
Reference Ref Me-Eic 326 74, 143 326 16.01
Eicosanoate
reference compounds. In this second step, the reference com- lish the pyrolyzate ratios using the calibration standards for the
pounds shall be present in the correct ratios of peak intensities instrumentation in their laboratory.
to each other and the target compound. These ratios are
5. Significance and Use
established through the analysis of a known calibration stan-
dard for each of the polymers on the list of twelve. See Ref 5 5.1 Preliminary studies have identified polymeric organic
for many pyrogram examples and the pyrolyzate ratios for a compounds as contaminants in treated drinking water,
specific set of experimental conditions. Be advised that the wastewater, surface water, ground water, and marine waters.
pyrolyzate ratios depend on the specific conditions and the type These polymers may be harmful to the environment and
of pyrolyzer. Each individual laboratory shall separately estab- adversely affect human health, and in these circumstances,
D8401 − 24
mass estimation is commonly required. A universal, analytical 6.6 If a unique target compound cannot be identified, it may
method will help to normalize data from around the world and be necessary to alter the original blend (leaving out the
better understand which polymers are most frequently found in polymer that is the source of the interference), or it may be
various climatic and geological locations (5-7). Pyrolysis-gas easier to analyze the “additional” polymer separately or with a
chromatography/mass spectrometry (Py-GC/MS) has many different group of polymers.
advantages in that both polymer identification and mass
6.7 The analyst needs to be aware that the new polymer
quantification can be easily accomplished by chromatographic
cannot be added to the twelve polymer database used to
separation in combination with mass spectral analysis.
identify and quantitate the twelve compounds specified in
6. Adding and Validating Non-Target Polymers Table 1. Each laboratory shall evaluate their need to automate
the entire process. The laboratory may deem it essential (that
6.1 In this test method, the procedures and analytical
is, higher numbers of samples, request for fast turnaround time,
conditions used to determine accurately and precisely twelve
and so forth) to develop in-house software compatible with
specific polymers is described, and the target compound list
their existing protocols or purchase software compatible with
can be any combination of these twelve polymers as listed in
in-house protocols. On the other hand, small projects can often
Table 1. The procedures can be easily modified if a subset of
be effectively processed using existing in-house software or
the twelve validated polymers is of interest (“polymers of
third-party software.
interest”), which will then simplify the preparation of the
calibration samples, the analytical samples, and the processing
7. Interferences
of the MS data. Additional polymers can be added to this
analytical protocol only after it is confirmed that the “addi-
7.1 This test method uses external standard calibration to
tional polymer” is (1) completely soluble in the solvent(s)
quantitate each polymer to accommodate a broad range of
being used, (2) that the resulting solution is stable (in its lowest
target compound concentrations. However, if the concentration
energy state), and (3) there is no interference from either the
range is such that all target compounds fall within a range
analytical system or catalyzed interactions involving the py-
consistent with the linear dynamic range of the analytical
rolysis products from other components in the analytical
system, internal standards are recommended. Care should be
sample. A completely insoluble polymer can also be added by
taken when preparing, using, and storing the calibration
following the method technique as described for PE and
standards: in preparing the solutions, avoid plastic containers
polypropylene (PP) polymers.
and tools throughout the process. Artifacts introduced when
using the standards may degrade data quality. The frequent
6.2 The spectra of each peak in the pyrogram of the
analysis of the continuing calibration check sample (CCC) and
unknown polymer is compared to the spectra of the corre-
the commitment to maintaining a current quality control (QC)
sponding peak in the library database. Ideally, all peaks in the
chart will enable the changes in the standards or the analytical
pyrogram of the unknown polymer are identified. The library
system to be noted in a timely manner.
database is available in Ref 5.
6.3 In instances in which the pyrograms of both the un-
7.2 Contamination of the system will be apparent by moni-
known polymer and the library have similar peak profiles at the
toring the baseline and peak symmetry during the routine
same retention times, a “tentative identification” is made and
analysis of the CCC. While extended periods of heat may
the next step in the process (6.4) is taken.
temporarily “clean” the system, it may be necessary to clean
(or replace) the pyrolysis tube, the needle interface, and the
6.4 The last step is to analyze the “polymers of interest”
injection port liner to rid the system of contamination.
with and without the “tentatively identified” polymer. Examine
the pyrograms (TIC) and plot the intensity of the potential
7.3 Leaks in the system are detected by monitoring the area
target ion versus retention time. The original mixture without
of Me-Eic.
the “tentatively identified” polymer should not have a response
7.4 In a typical GC chromatogram with a non-MS detector,
at the expected retention time of the compound being consid-
column resolution may be critical to resolve two closely eluting
ered as a new target compound; the pyrogram of the mixture
compounds. EICs assist in peak separation.
spiked with the “tentatively identified” polymer will have a
signal for the ion being considered as a target compound for the
7.5 Column resolution is a measurement to quantify column
new polymer of interest.
performance in this regard; however, with GC/MS, EICs are
6.5 When adding non-validated polymers to the protocol, it
used and the method does not include critical peak pairs that
is essential to select target compounds that do not interfere with shall be carefully resolved under optimum conditions.
the pyrolyzates created from the pyrolysis of other components
7.6 If the laboratory is using the recommended column, then
in the analytical sample. See 4.5 – 4.7. For example, in Table
this test method does not need nor require a specific determi-
2, naphthalene as the target compound for polyvinyl chloride
nation of column resolution. If the column is not performing
(PVC) identification and quantitation is listed even though
and providing the expected separation, then installation of a
benzene has a higher response than naphthalene (2:1 at
new column is advised.
600 °C). Although the naphthalene response compared to the
benzene response is lower, the naphthalene response is unique 7.7 Sample cups should not be reused because pyrolysis of
and only PVC on the list of twelve target polymers forms samples containing polymers will often leave an inorganic
naphthalene when pyrolyzed at 600 °C. residue or char on the sample cup surface, which degrades
D8401 − 24
surface inertness. This residue is very difficult to remove the column flow rate will remain constant as the column
without damaging the inertness of the surface. temperature increases.
8.2.2 Capillary GC Columns—Any GC separation and pre-
8. Apparatus
column combination that meets the performance specifications
8.1 Pyrolysis System—Conceptually, pyrolysis is a simple
of this test method may be used. Separations of the calibration
process. Apply sufficient heat to a complex chemical species
mixture shall be equivalent to, or better than, those described in
until organic bonds begin to break, forming smaller, stable
this test method. The prescribed method is based on the column
molecules commonly referred to as pyrolyzates. The GC
and conditions described in Fig. 2. This enables the analyst to
separation of the pyrolyzates is called a pyrogram. The
compare the chromatogram of the “standard” obtained at the
pyrolyzates formed and their relative intensities provide insight
beginning of an analytical sequence easily with that existing
into the nature of the original material. While data quality is a
during the course of multiple “real-world” analyses. Differ-
function of the entire GC system, the design of the pyrolyzer
ences can be notated and their effect on analytical data can
has the greatest impact on data quality. Three factors are of
often be reconciled. The pre-column prevents or, at a
paramount importance:
minimum, reduces the accumulation of chemical residue in the
8.1.1 The sample shall be “heated” instantaneously to mini-
separation column. For best system performance, the pre-
mize secondary reactions that will adversely affect reproduc-
column should be evaluated or replaced when needed if
ibility. Pyrolyzer temperature stability is directly related to
experiencing peak shape distortion for many polar compounds
pyrolysis data quality. The pyrolyzer temperature shall be
or degradation in peak area reproducibility, or both, compared
constant within 60.1 °C. Thermal instability has an adverse
to the previous MP calibration standard analysis. A common
effect on data quality.
GC column stationary phase for polymer analysis is 5 %
8.1.2 The sample path shall be inert and at a uniform
phenyl 95 % methylpolysiloxane (PMPS-5); however, cyclo-
temperature. Ideally, there is no transfer line, that is, the
pentanone (N6,6) can overlap with other matrix peaks from
pyrolyzates flow directly from the furnace to the GC column,
other polymers. The 50 % phenyl 50 % methylpolysiloxane
thus eliminating the contamination and thermal gradients
(PMPS-50) GC column has a semi-polar phase that helps in the
associated with conventional transfer lines.
separation of several peak combinations in close elution time
8.1.3 The sample shall be in an inert atmosphere and shall
zones when using a short length of PMPS-50 as a pre-column.
be kept at ambient temperature to prevent unexpected
This improves the robustness of this test method.
reactions, to ensure that all peaks and peak ratios form properly
8.2.3 The MS shall be capable of electron ionization at a
during pyrolysis. This maintains sample integrity and contrib-
nominal electron energy of 70 eV. The MS shall be capable of
utes to the accuracy, precision, and reproducibility of the
scanning from a minimum of 20 amu to 700 amu with a
dataset.
complete scan cycle time (including scan overhead) of 0.2 s to
8.2 GC/MS/DS: 0.5 s (scan cycle time = total MS data acquisition time in
8.2.1 The GC shall be capable of temperature programming seconds divided by number of scans in the chromatogram) and
and should be based on the use of pressure regulation so that consistent with the manufacturer’s suggested or recommended
FIG. 2 Specific Set Points for the Analytical Method
D8401 − 24
scan cycle time, which is a function of the machine’s settings, 9.2 Purity of Water—Unless otherwise indicated, references
not its tuning. The spectrometer shall produce mass spectra that to water shall be understood to mean reagent water as defined
meet all the performance criteria published in the manufactur- by Type 1 of Specification D1193.
ers’ product support documents. 9.2.1 References to water shall be understood to mean MQ
8.2.4 An interfaced data system is required to ensure that the water.
MS meets expected performance criteria and to acquire, store,
9.3 Laboratory Reagent Blank—Fill a 10 mL volumetric
reduce, and output mass spectral data. The computer software
flask with an organic solvent and adjust to the mark with no air
should have the capability to process stored GC/MS data by
bubbles. Inject 10 μL of the reagent blank into a sample cup
recognizing a GC peak within any given retention time/
and let it evaporate at room temperature until there is a light
retention index (RI) window comparing the mass spectra from
coating on the inside of the cup. A clean quartz fiber filter disc
the GC peak with spectral data in a user-created or commercial
or a small amount of organic-free quartz wool can be placed in
database or library and generating a list of tentatively identified
the top of the sample cup if there is reason to suspect
compounds within their retention times/RI and scan numbers.
tumultuous air flow around the cup. Analyze using the condi-
The software shall allow integration of the ion abundance of
tions listed in Fig. 2.
any specific ion between specified time or scan number limits.
The software should also allow calculation of the final polymer
10. Hazards
concentrations based on the results of an external standard
10.1 The toxicity or carcinogenicity of chemicals used in
calculation.
this test method have not been precisely defined; each chemical
8.2.5 Analytical Balance Capable of Weighing to
should be treated as a potential health hazard, and exposure to
60.00001 g (0.01 mg)—Standard preparation of micro-
these chemicals should be minimized. Each laboratory is
polymers shall be scaled accordingly to ensure that the data are
responsible for maintaining awareness of Occupational Safety
accurate to three significant figures. The analysis of submicron
and Health Administration (OSHA) regulations regarding safe
and nano-sized particles may require the use of a more
handling of chemicals used in this test method.
sensitive balance (0.0001 mg) to ensure that the data are
accurate to three significant figures. Sample preparation often
11. Sample Collection and Storage
uses various optical techniques to identify particles of interest.
11.1 See Practice D8332.
Special tools are available that facilitate the selection of a
11.1.1 Sample contents should be stored at 4 °C 6 2 °C for
specific particle(s).
the sample preparation phase.
8.2.6 Cryo-Mill—Cryo-milling or cryo-crushing is the pro-
cess of cooling or chilling a material and then reducing it into
12. Calibration Reference Standard: Pyrolysis-Specific
a smaller particle size. Polymers such as polyethylene (LDPE,
Preparation
HDPE) and PP with a glass transition temperature (Tg) below
12.1 The calibration reference standard is a multi-
room temperature may require liquid nitrogen to embrittle
component standard that includes all twelve of the target
them for milling into a smaller particle size. For field samples,
polymers and a calibration standard (Appendix X2). Some of
in particular, in the absence of knowing which polymers are in
the polymers are soluble, a few are not. Some polymers include
the sample, embrittlement with liquid nitrogen followed by
a variety of chemical functionalities. No single solvent has
milling/crushing is the recommended default preparation for
been identified that will dissolve all twelve target polymers;
analysis in the pyrolysis sample cup.
consequently, polymers are grouped according to their solubil-
8.2.7 Pyrolysis Sample Cup—The pyrolysis sample cup
ity. Aliquots of the dissolved polymers are combined, in a
should be clean and free of organic material. Sample cups can
predetermined order, in one sample cup that becomes the
be used in which the surface is deactivated stainless steel,
“calibration” sample of record. The procedure is illustrated in
quartz, or quartz-coated glass.
Fig. 3.
9. Reagents
12.2 Care shall be taken to ensure the purity of each
9.1 Purity of Reagents—Reagent-grade chemicals shall be polymer standard and the purity of the solvents used. The
individual polymers are stable and can used for up to six
used in all tests. Unless otherwise indicated, it is intended that
all reagents conform to the specifications of the Committee on months if properly sealed and stored at room temperature. It is
recommended that polymer/solvent solutions can be retained
Analytical Reagents of the American Chemical Society where
such specifications are available. Other grades may be used, for the course of an analysis not to exceed two weeks when
stored tightly-capped in a refrigerator at 4 °C to 6 °C.
provided it is first ascertained that the reagent is of sufficiently
high purity to permit its use without lessening the accuracy of
12.3 The polymers of interest are listed in Table 1. The
the determination.
present protocol is not limited to the twelve polymers listed in
Table 1, but its applicability to other polymers shall be
demonstrated using tests similar to those discussed in this test
ACS Reagent Chemicals, Specifications and Procedures for Reagents and
method.
Standard-Grade Reference Materials, American Chemical Society, Washington,
DC. For suggestions on the testing of reagents not listed by the American Chemical
12.4 The composition of each solution is described in Fig. 3.
Society, see Analar Standards for Laboratory Chemicals, BDH Ltd., Poole, Dorset,
The amount of each polymer reflects the variability in the MS
U.K., and the United States Pharmacopeia and National Formulary, U.S. Pharma-
copeial Convention, Inc. (USPC), Rockville, MD. response for the various pyrolyzates, which typically reflects
D8401 − 24
FIG. 3 Preparation of the Polymer Calibration Sample
the diversity of functional groups in the various polymers. For evaporate before analysis. Samples used in support of this test
example, polystyrene degrades into three pyrolyzates and the method are prepared in the order of solutions first then solids
S/N of the base peak is large. Polyethylene, on the other hand, (CaCO ). The order in which the various fractions are com-
degrades into many pyrolyzates, each with low S/N. It is bined shall be consistent throughout the analytical sequence.
necessary to have more polyethylene than polystyrene when The addition of a few non-target polymers to the sample matrix
preparing the standard. The intent is to normalize the response
may have an effect on the precision and accuracy of the
for all polymers. Liquids (solutions) are easy to prepare and
determination; thus, it is prudent to prepare samples using
homogeneity is not an issue. Care shall be taken to ensure that
different sequences during the validation phase to determine if
the polymer(s) of interest is (are) soluble in the solvent.
it has any impact on the data (see Appendix X6).
Anhydrous and high-purity (≥99 %) solvents should be pur-
12.7 Solids Are Also Easily Prepared—The calibration ref-
chased from providers.
erence standard is prepared from the solid polymers using a
12.5 Preparation of the Calibration Standard—The proce-
planetary/rotatory/vibratory ball-mill that should be able to
dure for adding known amounts of each polymer (solids and
operate with liquid-nitrogen-cooled samples. The solid poly-
liquids) to the sample cup is detailed in Fig. 3. Each solution
mers should be purchased as high-purity materials from
addresses a subset of the twelve polymers. Laboratory studies
specialized providers. When applicable, samples in powder
were performed to ensure that each polymer was soluble in a
form, particle size of less than 0.03 mm, are preferred over
given solvent.
pellets or other shapes. The reference standard should include
12.6 When the calibration reference standard has both liquid all polymers of interest. The amount of each polymer added to
the mixture should be adjusted so that the response of the
and solid elements, the solutions are added to the sample cup
first and the solid (CaCO ) added last. The solvent needs to pyrolyzate ions used for the identification and quantitation of
D8401 − 24
the individual polymers is above their limits of quantitation and those listed in Fig. 2. The ion used for identification and
within the linear dynamic ranges of the various components of quantitation for each polymer is noted in Table 1 and Fig. 5
the analytical system (see 1.2 – 1.5). (12).
12.8 In-house specific mixtures of solid samples (for
13. Creation of Calibration Levels and Quantitation of
example, PE, PP) can be prepared using CaCO as a diluent.
Calibration Reference Standards
The additional weight of the CaCO may eliminate the need for
an ultra-micro balance. Because milligrams (for example,
13.1 The method requires generation of a calibration curve
4 mg) of the diluent are added, a standard five-place (0.01 mg)
based on three or more concentration levels in which each is
balance can be used.
analyzed in triplicate. A minimum of nine sample cups are
required to generate a complete calibration curve [3 levels × 3
12.9 CaCO is known to have catalytic activity (TNI
analysis/
...