ASTM D6953-18

Standard Test Method for Determination of Antioxidants and Erucamide Slip Additives in Polyethylene Using Liquid Chromatography (LC)

SIGNIFICANCE AND USE
5.1 Separation and identification of stabilizers used in the manufacture of polyethylene resins are necessary in order to correlate performance properties with polymer composition. This test method provides a means to determine the polymer additives listed in Table 1 in polyethylene samples. This test method is capable of the determination of other antioxidants, but the stability of these during extraction has not been investigated.  
5.2 The additive extraction procedure is made effective by the relatively low solubility of the polymer sample in solvents generally used for liquid chromatographic analysis. In this method, isopropanol and cyclohexane were chosen because of their excellent extraction efficiencies as well as for safety reasons. Other solvents including ethylacetate, isobutanol, chloroform and methylene chloride can also be used.  
5.3 Methods other than refluxing that have been used to remove additives from the polymer matrix including pressurized liquid, microwave, ultrasonic, and supercritical fluid extractions. For the separation of the extracted additives, SFC and GC have been used successfully for several of the additives.  
5.4 Under optimum conditions, the lowest level of detection for an antioxidant is approximately 2 ppm.
SCOPE
1.1 This test method covers a liquid-chromatographic procedure for the separation of primary and secondary antioxidant and slip additives currently used in polyethylene plastics. These additives are extracted with either isopropanol (resin densities 3) or cyclohexane (resin densities > 0.94 g/cm3) prior to liquid-chromatographic separation. The ultraviolet absorbance of the eluting compound(s) is measured and quantitation is performed using external calibration.  
1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
1.3 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. Specific precautionary statements are given in Section 9.
Note 1: There is no known ISO equivalent to this standard.  
1.4 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: 31-Oct-2018
• ICS: 83.040.20 - Rubber compounding ingredients
• Technical Committee: D20 - Plastics
• Drafting Committee: D20.70 - Analytical Methods

Relations

• Replaces: ASTM D6953-11 - Standard Test Method for Determination of Antioxidants and Erucamide Slip Additives in Polyethylene Using Liquid Chromatography (LC)
• Effective Date: 01-Nov-2018
• Refers: ASTM D883-24 - Standard Terminology Relating to Plastics
• Effective Date: 01-Feb-2024
• Refers: ASTM D883-23 - Standard Terminology Relating to Plastics
• Effective Date: 01-Nov-2023
• Refers: ASTM D883-20 - Standard Terminology Relating to Plastics
• Effective Date: 01-Jan-2020
• Refers: ASTM E1657-98(2019) - Standard Practice for Testing Variable-Wavelength Photometric Detectors Used in Liquid Chromatography
• Effective Date: 01-Dec-2019
• Refers: ASTM D883-19c - Standard Terminology Relating to Plastics
• Effective Date: 01-Aug-2019
• Refers: ASTM D883-19a - Standard Terminology Relating to Plastics
• Effective Date: 15-Apr-2019
• Refers: ASTM D883-19 - Standard Terminology Relating to Plastics
• Effective Date: 01-Feb-2019
• Refers: ASTM D883-18a - Standard Terminology Relating to Plastics
• Effective Date: 01-Dec-2018
• Refers: ASTM D883-18 - Standard Terminology Relating to Plastics
• Effective Date: 01-Nov-2018
• Refers: ASTM D1600-18 - Standard Terminology for Abbreviated Terms Relating to Plastics (Withdrawn 2024)
• Effective Date: 01-Jan-2018
• Refers: ASTM D883-17 - Standard Terminology Relating to Plastics
• Effective Date: 15-Aug-2017
• Refers: ASTM E169-04(2014) - Standard Practices for General Techniques of Ultraviolet-Visible Quantitative Analysis
• Effective Date: 01-Aug-2014
• Refers: ASTM D1600-14 - Standard Terminology for Abbreviated Terms Relating to Plastics
• Effective Date: 01-Feb-2014
• Refers: ASTM E691-13 - Standard Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
• Effective Date: 01-May-2013

Overview

ASTM D6953-18 sets the standard test method for the determination of antioxidants and erucamide slip additives in polyethylene using liquid chromatography (LC). This internationally recognized ASTM standard covers the extraction, separation, and quantitation of primary and secondary antioxidants, as well as slip agents such as erucamide, used in the manufacture of polyethylene plastics. By providing a reliable analytical method, ASTM D6953-18 enables manufacturers, laboratories, and quality assurance professionals to monitor additive content and ensure polymer performance matches application requirements.

Key Topics

• Additive Identification: The method enables the separation and identification of stabilizers, particularly antioxidants and slip additives, commonly formulated in polyethylene resins.
• Liquid Chromatography (LC) Procedure: Polyethylene samples are extracted using isopropanol (for densities < 0.94 g/cm³) or cyclohexane (for densities > 0.94 g/cm³), followed by reverse-phase liquid chromatographic separation and ultraviolet (UV) absorbance detection.
• Detection Sensitivity: Under optimized conditions, antioxidant levels as low as 2 ppm can be detected, offering high sensitivity for trace-level analysis.
• Flexibility in Extraction: While reflux with isopropanol or cyclohexane is standard, alternative extraction processes such as pressurized liquid extraction, microwave, ultrasonic, and supercritical fluid extraction may also be used.
• Calibration and Quantification: Quantitative analysis is carried out using external calibration with UV-Vis detection at specific wavelengths, ensuring accuracy across different laboratories.
• Precision and Repeatability: The method includes robust guidelines for calibration, quality assurance, and round-robin validation, supporting reproducible results.

Applications

ASTM D6953-18 is widely applied across the plastics and polymer industry for:

• Quality Control and Assurance: Monitoring additive levels ensures the correct performance of polyethylene films, containers, and components, preventing premature degradation or failures.
• Research and Development: Supporting the development of new polyethylene grades by correlating additive composition with desired mechanical, optical, and barrier properties.
• Regulatory Compliance: Supporting documentation and specification for material safety, environmental compliance, and meeting customer or regulatory requirements for food contact or medical applications.
• Failure Analysis: Identifying additive-related defects or inconsistencies in finished products.

Typical additives determined using this method include:

• Primary antioxidants (e.g., butylated hydroxy toluene, butylated hydroxy ethyl benzene)
• Secondary antioxidants (e.g., tris(nonylphenyl)phosphite)
• Erucamide (slip agent)
• Degradation products of antioxidants

Related Standards

A number of related ASTM and referenced standards provide supporting terminology, analytical procedures, and performance testing for plastics and spectroscopy, such as:

• ASTM D883: Terminology Relating to Plastics
• ASTM D1600: Terminology for Abbreviated Terms Relating to Plastics
• ASTM E169: Practices for General Techniques of Ultraviolet-Visible Quantitative Analysis
• ASTM E691: Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
• ASTM E131: Terminology Relating to Molecular Spectroscopy
• IEEE/ASTM SI 10: Standard for Use of the International System of Units (SI)

Note: There is currently no ISO equivalent to ASTM D6953-18.

Practical Value

Implementing ASTM D6953-18 enables stakeholders in the polyethylene supply chain to:

• Ensure the correct dosing and distribution of antioxidants and slip agents for product consistency and longevity
• Reduce product failures related to oxidative degradation or processability
• Support traceability and technical documentation in global markets
• Meet the stringent requirements of end-use sectors such as packaging, automotive, medical, and consumer goods

By adhering to this ASTM standard, organizations can ensure high-quality, reliable, and compliant polyethylene products, maintaining their reputation in competitive markets.

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:D6953 −18
Standard Test Method for
Determination of Antioxidants and Erucamide Slip Additives
in Polyethylene Using Liquid Chromatography (LC)
This standard is issued under the fixed designation D6953; 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* Laboratory (Withdrawn 2009)
E131 Terminology Relating to Molecular Spectroscopy
1.1 This test method covers a liquid-chromatographic pro-
E169 PracticesforGeneralTechniquesofUltraviolet-Visible
cedure for the separation of primary and secondary antioxidant
Quantitative Analysis
and slip additives currently used in polyethylene plastics.
E275 Practice for Describing and Measuring Performance of
These additives are extracted with either isopropanol (resin
3 Ultraviolet and Visible Spectrophotometers
densities < 0.94 g/cm ) or cyclohexane (resin densities > 0.94
3 E691 Practice for Conducting an Interlaboratory Study to
g/cm ) prior to liquid-chromatographic separation. The ultra-
Determine the Precision of a Test Method
violet absorbance of the eluting compound(s) is measured and
E1657 Practice for Testing Variable-Wavelength Photomet-
quantitation is performed using external calibration.
ric Detectors Used in Liquid Chromatography
1.2 The values stated in SI units are to be regarded as
IEEE/ASTM SI 10 Standard for Use of the International
standard. No other units of measurement are included in this
System of Units (SI): The Modern Metric System
standard.
3. Terminology
1.3 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
3.1 Definitions:
responsibility of the user of this standard to establish appro-
3.1.1 For definitions of plastic terms and detector terminol-
priate safety, health, and environmental practices and deter-
ogy used in this test method, see Terminologies D883, D1600,
mine the applicability of regulatory limitations prior to use.
and E1657.
Specific precautionary statements are given in Section 9.
3.1.2 Forunitsandsymbolsusedinthistestmethod,referto
Terminology E131 or IEEE/ASTM SI 10.
NOTE 1—There is no known ISO equivalent to this standard.
1.4 This international standard was developed in accor-
4. Summary of Test Method
dance with internationally recognized principles on standard-
4.1 The polyethylene sample is ground to a 1-mm (~20
ization established in the Decision on Principles for the
mesh) or 0.5-mm (~40 mesh) particle size and extracted by
Development of International Standards, Guides and Recom-
refluxing with either isopropanol or cyclohexane.
mendations issued by the World Trade Organization Technical
Barriers to Trade (TBT) Committee.
4.2 The solvent extract is analyzed by liquid chromatogra-
phy.
2. Referenced Documents
4.3 Additive concentrations are determined from external
2.1 ASTM Standards:
calibration curves using reverse phase chromatography (C-8 or
D883 Terminology Relating to Plastics
C-18 column) with ultraviolet (UV) detection at wavelengths
D1600 Terminology forAbbreviatedTerms Relating to Plas-
corresponding to the wavelengths of an absorption apex of
tics
each additive (except erucamide which does not have an
D4697 Guide for Maintaining Test Methods in the User’s
absorption maximum in the accessible UV region).
5. Significance and Use
This test method is under the jurisdiction ofASTM Committee D20 on Plastics
5.1 Separation and identification of stabilizers used in the
and is the direct responsibility of Subcommittee D20.70 on Analytical Methods.
Current edition approved Nov. 1, 2018. Published November 2018. Originally
manufacture of polyethylene resins are necessary in order to
approved in 2003. Last previous edition approved in 2011 as D6953 - 11.
correlate performance properties with polymer composition.
DOI:10.1520/D6953-18.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on The last approved version of this historical standard is referenced on
the ASTM website. www.astm.org.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D6953−18
TABLE 1 Common Polyolefin Additives
Chemical Name Chemical Classification CAS Number
Formula
BHEB, 2,6-di-t-butyl-4-ethylphenol or butylated hydroxyethyl C H O 1º Antioxidant 4130-42-1
16 26
benzene
BHT, 2,6-di-t-butylcresol or butylated hydroxy toluene C H O 1º Antioxidant 128-37-0
15 24
Tris (2,4-di-t-butylphenyl)-phosphite C H O P 2º Antioxidant 31570-04-4
42 63 3
Tris(2,4-di-t-butylphenyl)-phosphate C H O P Degradation product 78-33-1
30 39 4
Tetrakis[methylene(3,5-di-t-butyl-4- hydroxyhydrocinnamate)] C H O 1º Antioxidant 6683-19-8
73 108 12
methane
Octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)- propionate C H O 1º Antioxidant 2082-79-3
35 62 3
2,2’-ethylidene bis(4,6-di-t-butylphenol) C H O 1º Antioxidant 35958-30-6
30 46 2
Erucamide—Cis-13-docosenamide C H NO Fatty acid amide, slip agent 112-84-5
28 43
TNPP,Tris(nonylphenyl)phosphite C H O P 2º Antioxidant 26523-78-4
45 69 3
Nonylphenol C H O 2º Antioxidant 104-40-5
15 24
Tris(nonylphenyl)phosphate C H O P Degradation product 26569-53-9
45 69 4
This test method provides a means to determine the polymer 7.2 Chromatographic Column, C-8 or C-18 reverse phase,
additives listed in Table 1 in polyethylene samples. This test 5-µm particle size, 15 cm by 4.6 mm or equivalent, capable of
method is capable of the determination of other antioxidants, separating the additives and their degradation products.
but the stability of these during extraction has not been
7.3 DataAcquisition/Handling System, providing the means
investigated.
for determining chromatographic peak areas and for handling
5.2 The additive extraction procedure is made effective by
and reporting data.This is best accomplished using a computer
the relatively low solubility of the polymer sample in solvents
with appropriate software.
generally used for liquid chromatographic analysis. In this
7.4 Mill—Cutting Mill or Centrifugal Grinding Mill,
method, isopropanol and cyclohexane were chosen because of
equipped with 1-mm (~20 mesh) and 0.5-mm (~40 mesh)
their excellent extraction efficiencies as well as for safety
screens.
reasons. Other solvents including ethylacetate, isobutanol,
chloroform and methylene chloride can also be used. 7.5 Reflux Extraction Apparatus, consisting of a condenser,
(24/40 ground-glass joint), a round-bottom 125-mL flask
5.3 Methods other than refluxing that have been used to
having a 24/40 ground-glass joint, and a heating mantle.
remove additives from the polymer matrix including pressur-
ized liquid, microwave, ultrasonic, and supercritical fluid
7.6 Boiling Chips.
extractions. For the separation of the extracted additives, SFC
7.7 Filter System, (PTFE ), for non-aqueous solutions (pore
and GC have been used successfully for several of the
size of 0.22 µm).
additives.
7.8 Analytical Balance, capable of weighing to 60.0001 g.
5.4 Under optimum conditions, the lowest level of detection
for an antioxidant is approximately 2 ppm.
7.9 Top Loading Balance, capable of weighing to 60.01 g.
6. Interferences
8. Reagents and Materials
6.1 Any material eluting at or near the same retention time
8.1 Solvents:
as the additive can cause erroneous results. This includes
8.1.1 Isopropanol—HPLC grade, spectro-quality or chro-
degradation products of the additives.
matography quality reagent.
6.2 A major source of interferences can be from solvent
8.1.2 Cyclohexane—HPLC grade, spectro-quality or chro-
impurities. For this reason, the solvents shall be examined by
matography quality reagent.
HPLC using the same analysis conditions as for the samples
8.1.3 Water—HPLC, or UV quality reagent, degassed by
(see Section 12).
sparging with high-purity helium or by filtration under
6.3 The grinding process may cause a low bias. For
vacuum.
example, some erucamide slip is known to be lost to the
8.1.4 Acetonitrile—HPLC, spectro-quality or chromatogra-
grinder surface and excessive grinding may cause degradation
phy quality reagent (a reagent whose UV cutoff is about 190
of the antioxidants.
nm).
8.2 Additives:
7. Apparatus
8.2.1 High purity additives and degradation products (see
7.1 Liquid Chromatograph, equipped with a multiple wave-
Table 1).
length (see Practices E169 and E275) or photodiode array
ultraviolet detector, heated column compartment, and gradient
9. Precautions
elution capabilities. The liquid chromatograph shall be
equipped with a means for a 10-µL injection such as a sample 9.1 Isopropanol and cyclohexane are flammable. This ex-
loop. traction procedure should be carried out in a fume hood.
D6953−18
10. Preparation of Solutions 10.3.1 Prepare four dilute standards of each concentrated
standard by weighing 30-mL septum bottles, including septum
10.1 Polymer Samples:
and cap, to the nearest 0.1 mg.
10.1.1 Grind the sample to a particle size of 1 mm, that is,
3 10.3.2 Add with a 5-mL syringe, 0.5 mL, 1.0 mL, 2.0 mL,
~20 mesh (density < 0.94 g/cm ) or 0.5 mm, that is, ~40 mesh
3 and 5.0 mL of a concentrated solution to each of four of the
(density > 0.94 g/cm ).
30-mL bottles and weigh to the nearest 0.1 mg.
NOTE 2—Unless sample amount is limited, grind a minimum of 10 g.
10.3.3 Fill the bottles with isopropanol or cyclohexane, cap,
It is important to minimize the time of grinding to prevent any thermal
mix and weigh to the nearest 1 mg.
degradation of the additives in the polymer. Some erucamide is known to
be lost during grinding.
10.3.4 Calculate the concentration, [Additive] , of each
dil
NOTE 3—Acutting-type mill is needed for film samples. Because of its
additive in the dilute standards in mg/kg (that is, ppm) as
higher efficiency, a centrifugal-type mill is recommended for pellet
follows:
samples.
W @Additive#
conc conc
10.1.2 Weigh,tothenearest0.01g,approximately5gofthe Additive 5 (3)
@ #
dil
W 1W
~ !
conc sol
sample, that is, W , into a pre-weighed (to the nearest 0.01
sample
where:
g) 125-mL flat-bottom flask containing boiling chips, that is,
W . Add approximately 50.0 mL of isopropanol or cyclo-
W = weight (g) of concentrated standard
flask
conc
hexane and boil for a minimum of 2 h.
solution,
[Additive] = concentration (mg/kg) of additive in con-
conc
NOTE 4—Isopropanol is used as the extraction solvent for densities of
centrated standard (see 10.2.5), and
3 3
lessthan0.94g/cm andcyclohexanefordensitieshigherthan0.94g/cm .
W = weight (g) of solvent used for dilution.
sol
10.1.3 Cool the solution to room temperature by raising the
flask from the heating mantle while still attached to the
11. Performance Requirements
condenser.
11.1 Resolution—The resolution (R) provides an indication
10.1.4 Weigh the cooled flask to the nearest 0.01 g, that is,
of the component separation and band broadening of a column.
W .
(flask + sol)
For Gaussian-shaped peaks, the resolution is defined as:
10.1.5 Attach a filter disk assembly to a 5-mL Luer-Lok tip
2 t 2 t
hypodermic syringe. ~ !
R,2 R,1
R 5 (4)
W 1W
~ !
10.1.6 Decant approximately 4 mL of the solvent extract 1 2
into the above syringe.
where:
10.1.7 Insert the plunger and carefully apply pressure to
t ,t = peak elution time in minutes of Additives 1 and
R,1 R,2
force the solvent extract through the filter into a sample vial.
2, and
10.1.8 Calculate the amount (mg) of sample per kg of
W,W = peak width in minutes of Additives 1 and 2
1 2
solution, [Sample] :
sol determined by measuring the distance between
the baseline intercepts of lines drawn tangent to
10 W
sample
@Sample# 5 (1)
sol
the peak inflection points.
W 2 W
~ !
~flask1sol! flask
11.1.1 For an extracted additives mixtures containing any
10.2 Concentrated Additive Standards:
combination (including degradation products) of those listed in
10.2.1 Prepare two to three mixtures in 125-mL sept
...

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. Because
it 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 version
of the standard as published by ASTM is to be considered the official document.
Designation: D6953 − 11 D6953 − 18
Standard Test Method for
Determination of Antioxidants and Erucamide Slip Additives
in Polyethylene Using Liquid Chromatography (LC)
This standard is issued under the fixed designation D6953; 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*
1.1 This test method covers a liquid-chromatographic procedure for the separation of primary and secondary antioxidant and
slip additives currently used in polyethylene plastics. These additives are extracted with either isopropanol (resin densities < 0.94
3 3
g/cm ) or cyclohexane (resin densities > 0.94 g/cm ) prior to liquid-chromatographic separation. The ultraviolet absorbance of the
eluting compound(s) is measured and quantitation is performed using external calibration.
1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.3 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 safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use. Specific precautionary statements are given in Section 9.
NOTE 1—There is no known ISO equivalent to this standard.
1.4 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.
2. Referenced Documents
2.1 ASTM Standards:
D883 Terminology Relating to Plastics
D1600 Terminology for Abbreviated Terms Relating to Plastics
D4697 Guide for Maintaining Test Methods in the User’s Laboratory (Withdrawn 2009)
E131 Terminology Relating to Molecular Spectroscopy
E169 Practices for General Techniques of Ultraviolet-Visible Quantitative Analysis
E275 Practice for Describing and Measuring Performance of Ultraviolet and Visible Spectrophotometers
E691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
E1657 Practice for Testing Variable-Wavelength Photometric Detectors Used in Liquid Chromatography
IEEE/ASTM SI 10 Standard for Use of the International System of Units (SI): The Modern Metric System
3. Terminology
3.1 Definitions:
3.1.1 For definitions of plastic terms and detector terminology used in this test method, see Terminologies D883, D1600, and
E1657.
3.1.2 For units and symbols used in this test method, refer to Terminology E131 or IEEE/ASTM SI 10.
4. Summary of Test Method
4.1 The polyethylene sample is ground to a 1-mm (~20 mesh) or 0.5-mm (~40 mesh) particle size and extracted by refluxing
with either isopropanol or cyclohexane.
This test method is under the jurisdiction of ASTM Committee D20 on Plastics and is the direct responsibility of Subcommittee D20.70 on Analytical Methods.
Current edition approved Sept. 1, 2011Nov. 1, 2018. Published September 2011November 2018. Originally approved in 2003. Last previous edition approved in 20032011
as D6953 - 03.D6953 - 11. DOI:10.1520/D6953-11.DOI:10.1520/D6953-18.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
The last approved version of this historical standard is referenced on www.astm.org.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D6953 − 18
TABLE 1 Common Polyolefin Additives
Chemical Name Chemical Classification CAS Number
Formula
BHEB, 2,6-di-t-butyl-4-ethylphenol or butylated hydroxyethyl C H O 1º Antioxidant 4130-42-1
16 26
benzene
BHT, 2,6-di-t-butylcresol or butylated hydroxy toluene C H O 1º Antioxidant 128-37-0
15 24
Tris (2,4-di-t-butylphenyl)-phosphite C H O P 2º Antioxidant 31570-04-4
42 63 3
Tris(2,4-di-t-butylphenyl)-phosphate C H O P Degradation product 78-33-1
30 39 4
Tetrakis[methylene(3,5-di-t-butyl-4- hydroxyhydrocinnamate)] C H O 1º Antioxidant 6683-19-8
73 108 12
methane
Octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)- propionate C H O 1º Antioxidant 2082-79-3
35 62 3
2,2’-ethylidene bis(4,6-di-t-butylphenol) C H O 1º Antioxidant 35958-30-6
30 46 2
Erucamide—Cis-13-docosenamide C H NO Fatty acid amide, slip agent 112-84-5
28 43
TNPP,Tris(nonylphenyl)phosphite C H O P 2º Antioxidant 26523-78-4
45 69 3
Nonylphenol C H O 2º Antioxidant 104-40-5
15 24
Tris(nonylphenyl)phosphate C H O P Degradation product 26569-53-9
45 69 4
4.2 The solvent extract is analyzed by liquid chromatography.
4.3 Additive concentrations are determined from external calibration curves using reverse phase chromatography (C-8 or C-18
column) with ultraviolet (UV) detection at wavelengths corresponding to the wavelengths of an absorption apex of each additive
(except erucamide which does not have an absorption maximum in the accessible UV region).
5. Significance and Use
5.1 Separation and identification of stabilizers used in the manufacture of polyethylene resins are necessary in order to correlate
performance properties with polymer composition. This test method provides a means to determine the polymer additives listed
in Table 1 in polyethylene samples. This test method is capable of the determination of other antioxidants, but the stability of these
during extraction has not been investigated.
5.2 The additive extraction procedure is made effective by the relatively low solubility of the polymer sample in solvents
generally used for liquid chromatographic analysis. In this method, isopropanol and cyclohexane were chosen because of their
excellent extraction efficiencies as well as for safety reasons. Other solvents including ethylacetate, isobutanol, chloroform and
methylene chloride can also be used.
5.3 Methods other than refluxing that have been used to remove additives from the polymer matrix including pressurized liquid,
microwave, ultrasonic, and supercritical fluid extractions. For the separation of the extracted additives, SFC and GC have been
used successfully for several of the additives.
5.4 Under optimum conditions, the lowest level of detection for an antioxidant is approximately 2 ppm.
6. Interferences
6.1 Any material eluting at or near the same retention time as the additive can cause erroneous results. This includes degradation
products of the additives.
6.2 A major source of interferences can be from solvent impurities. For this reason, the solvents shall be examined by HPLC
using the same analysis conditions as for the samples (see Section 12).
6.3 The grinding process may cause a low bias. For example, some erucamide slip is known to be lost to the grinder surface
and excessive grinding may cause degradation of the antioxidants.
7. Apparatus
7.1 Liquid Chromatograph, equipped with a multiple wavelength (see Practices E169 and E275) or photodiode array ultraviolet
detector, heated column compartment, and gradient elution capabilities. The liquid chromatograph shall be equipped with a means
for a 10-μL injection such as a sample loop.
7.2 Chromatographic Column, C-8 or C-18 reverse phase, 5-μm particle size, 15 cm by 4.6 mm or equivalent, capable of
separating the additives and their degradation products.
7.3 Data Acquisition/Handling System, providing the means for determining chromatographic peak areas and for handling and
reporting data. This is best accomplished using a computer with appropriate software.
7.4 Mill—Cutting Mill (Wiley) or Centrifugal Grinding Mill (Brinkmann), Mill, equipped with 1-mm (~20 mesh) and 0.5-mm
(~40 mesh) screens.
7.5 Reflux Extraction Apparatus, consisting of a condenser, (24/40 ground-glass joint), a round-bottom 125-mL flask having a
24/40 ground-glass joint, and a heating mantle.
7.6 Boiling Chips.
D6953 − 18
7.7 Filter System, (PTFE ), for non-aqueous solutions (pore size of 0.22 μm).
7.8 Analytical Balance, capable of weighing to 60.0001 g.
7.9 Top Loading Balance, capable of weighing to 60.01 g.
8. Reagents and Materials
8.1 Solvents:
8.1.1 Isopropanol—HPLC grade, spectro-quality or chromatography quality reagent.
8.1.2 Cyclohexane—HPLC grade, spectro-quality or chromatography quality reagent.
8.1.3 Water—HPLC, or UV quality reagent, degassed by sparging with high-purity helium or by filtration under vacuum.
8.1.4 Acetonitrile—HPLC, spectro-quality or chromatography quality reagent (a reagent whose UV cutoff is about 190 nm).
8.2 Additives:
8.2.1 High purity additives and degradation products (see Table 1).
9. Precautions
9.1 Isopropanol and cyclohexane are flammable. This extraction procedure should be carried out in a fume hood.
10. Preparation of Solutions
10.1 Polymer Samples:
10.1.1 Grind the sample to a particle size of 1 mm, that is, ~20 mesh (density < 0.94 g/cm ) or 0.5 mm, that is, ~40 mesh
(density > 0.94 g/cm ).
NOTE 2—Unless sample amount is limited, grind a minimum of 10 g. It is important to minimize the time of grinding to prevent any thermal
degradation of the additives in the polymer. Some erucamide is known to be lost during grinding.
NOTE 3—A cutting-type mill is needed for film samples. Because of its higher efficiency, a centrifugal-type mill is recommended for pellet samples.
10.1.2 Weigh, to the nearest 0.01 g, approximately 5 g of the sample, that is, W , into a pre-weighed (to the nearest 0.01
sample
g) 125-mL flat-bottom flask containing boiling chips, that is, W . Add approximately 50.0 mL of isopropanol or cyclohexane
flask
and boil for a minimum of 2 h.
3 3
NOTE 4—Isopropanol is used as the extraction solvent for densities of less than 0.94 g/cm and cyclohexane for densities higher than 0.94 g/cm .
10.1.3 Cool the solution to room temperature by raising the flask from the heating mantle while still attached to the condenser.
10.1.4 Weigh the cooled flask to the nearest 0.01 g, that is, W .
(flask + sol)
10.1.5 Attach a filter disk assembly to a 5-mL Luer-Lok tip hypodermic syringe.
10.1.6 Decant approximately 4 mL of the solvent extract into the above syringe.
10.1.7 Insert the plunger and carefully apply pressure to force the solvent extract through the filter into a sample vial.
10.1.8 Calculate the amount (mg) of sample per kg of solution, [Sample] :
sol
10 W
sample
Sample 5 (1)
@ #
sol
W 2 W
~ !
flask1sol flask
~ !
10.2 Concentrated Additive Standards:
10.2.1 Prepare two to three mixtures in 125-mL septum bottles by weighing the bottles, including septum and cap, to the nearest
0.1 mg.
10.2.2 Weigh into a bottle, to the nearest 0.1 mg, approximately 0.2 g of each additive.
10.2.3 Fill the bottle with either isopropanol or cyclohexane, cap and weigh the bottle on a top loading balance to the nearest
10 mg.
10.2.4 Agitate the bottle to speed up dissolution.
10.2.5 Calculate the concentration, [Additive] , of each additive in the concentrated standard in mg/kg (that is, ppm) as
conc
follows:
10 W
add
@Additive# 5 (2)
conc
~W 1W !
Tadd sol
where:
W = weight (g) of individual additive,
add
W = total weight (g) of all additives, and
Tadd
W = weight (g) of solvent.
sol
10.3 Dilute Additive Standards:
10.3.1 Prepare four dilute standards of each concentrated standard by weighing 30-mL septum bottles, including septum and
cap, to the nearest 0.1 mg.
10.3.2 Add with a 5-mL syringe, 0.5 mL, 1.0 mL, 2.0 mL, and 5.0 mL of a concentrated solution to each of four of the 30-mL
bottles and weigh to the nearest 0.1 mg.
D6953 − 18
10.3.3 Fill the bottles with isopropanol or cyclohexane, cap, mix and weigh to the nearest 1 mg.
10.3.4 Calculate the concentration, [Additive] , of each additive in the dilute standards in mg/kg (that is, ppm) as follows:
dil
W Additive
@ #
conc
conc
@Additive# 5 (3)
dil
~W 1W !
conc sol
where:
W = weight (g) of concentrated standard solution,
conc
[Additive] = concentration (mg/kg) of additive in concentrated standard (see 10.2.5), and
conc
W = weight (g) of solvent used for dilution.
sol
11. Performance Requirements
11.1 Resolution—The resolution (R) provides an indication of the component separation and band broadening of a column. For
Gaussian-shaped peaks, the resolution is define
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