ASTM E2403-23

Standard Test Method for Sulfated Ash of Organic Materials by Thermogravimetry

SIGNIFICANCE AND USE
5.1 The sulfated ash value indicates the level of known metal-containing additives or impurities in an organic material. When phosphorus is absent, barium, calcium, magnesium, sodium and potassium are converted to their sulfates. Tin and zinc are converted to their oxides.  
5.2 This test method may be used for research and development, specification acceptance, and quality assurance purposes.
SCOPE
1.1 This test method describes the determination of sulfated ash content (sometimes called residue-on-ignition) of organic materials by thermogravimetry. This test method converts common metals found in organic materials (such as sodium, potassium, lithium, calcium, magnesium, zinc, and tin) into their sulfate salts permitting estimation of their total content as sulfates or oxides. The range of this test method is from 0.1 % to 100 % metal content.  
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.  
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-Jul-2023
• ICS: 71.040.40 - Chemical analysis
• Technical Committee: E37 - Thermal Measurements
• Drafting Committee: E37.01 - Calorimetry and Mass Loss

Relations

• Refers: ASTM E473-23b - Standard Terminology Relating to Thermal Analysis and Rheology
• Effective Date: 01-Oct-2023
• Refers: ASTM E1142-23b - Standard Terminology Relating to Thermophysical Properties
• Effective Date: 01-Oct-2023
• Refers: ASTM E1131-20 - Standard Test Method for Compositional Analysis by Thermogravimetry
• Effective Date: 15-Mar-2020
• Refers: ASTM E2040-19 - Standard Test Method for Mass Scale Calibration of Thermogravimetric Analyzers
• Effective Date: 01-Dec-2019
• Refers: ASTM D3516-89(2019)e1 - Standard Test Methods for Ashing Cellulose
• Effective Date: 01-Dec-2019
• Refers: ASTM D914-12(2019) - Standard Test Methods for Ethylcellulose
• Effective Date: 01-Dec-2019
• Refers: ASTM E3142-18 - Standard Test Method for Thermal Lag of Thermal Analysis Apparatus
• Effective Date: 15-Jan-2018
• Refers: ASTM E1142-15 - Standard Terminology Relating to Thermophysical Properties
• Effective Date: 01-May-2015
• Refers: ASTM E1142-14b - Standard Terminology Relating to Thermophysical Properties
• Effective Date: 15-Aug-2014
• Refers: ASTM E473-14 - Standard Terminology Relating to Thermal Analysis and Rheology
• Effective Date: 15-Aug-2014
• Refers: ASTM E1142-14a - Standard Terminology Relating to Thermophysical Properties
• Effective Date: 01-Apr-2014
• Refers: ASTM E2040-08(2014) - Standard Test Method for Mass Scale Calibration of Thermogravimetric Analyzers
• Effective Date: 15-Mar-2014
• Refers: ASTM E1142-14 - Standard Terminology Relating to Thermophysical Properties
• Effective Date: 15-Feb-2014
• Refers: ASTM D874-13a - Standard Test Method for Sulfated Ash from Lubricating Oils and Additives
• Effective Date: 01-Sep-2013
• Refers: ASTM D874-13 - Standard Test Method for Sulfated Ash from Lubricating Oils and Additives
• Effective Date: 01-Aug-2013

Overview

ASTM E2403-23: Standard Test Method for Sulfated Ash of Organic Materials by Thermogravimetry establishes a reliable procedure to determine the sulfated ash content, also known as residue-on-ignition (ROI), in organic substances using thermogravimetric analysis (TGA). This standard quantifies metal-containing additives or impurities-such as sodium, potassium, lithium, calcium, magnesium, zinc, and tin-by converting them into their sulfate salts or oxides, allowing for estimation of their total content as sulfates or oxides. The method is suitable for samples with metal content from 0.1% to 100% and is widely used for research, quality assurance, and specification assessment.

Key Topics

• Sulfated Ash Determination: The residue left after incinerating a sample and treating it with sulfuric acid at high temperatures serves as an indicator of the inorganic content in organic materials.
• Thermogravimetric Analysis (TGA): An automated process monitors mass changes as a function of temperature, with strict control of heating rates and atmospheric conditions.
• Metal Conversion: In the absence of phosphorus, metals typically convert to sulfates (barium, calcium, magnesium, sodium, potassium) or oxides (zinc, tin) during analysis.
• Sample Requirements: Analysis is performed on small sample sizes (typically 30-40 mg), using platinum or other inert containers stable at up to 850°C.
• Calibration and Precision: The method requires careful calibration of TGA instrumentation to ensure high accuracy and repeatable results in industrial and laboratory environments.

Applications

ASTM E2403-23 is significant for industries and laboratories that must ascertain the inorganic content or metal additives in organic matrices. Common applications include:

• Quality Assurance of Organic Materials: The test method helps verify that raw materials and finished products meet metal impurity specifications in production environments.
• Research and Development: Provides data essential for material development, process optimization, and chemical formulation studies.
• Specification Compliance: Ensures manufacturer compliance with regulatory and client specifications in sectors such as polymers, lubricants, and specialty chemicals.
• Comparative Analysis: Supports benchmarking and testing for competitive products or alternative formulations.
• Regulatory Submissions: Used in preparing technical documentation for agencies requiring inorganic residue data.

Related Standards

To ensure robust and consistent results, ASTM E2403-23 references and is complemented by several related standards:

• ASTM D874 - Test Method for Sulfated Ash from Lubricating Oils and Additives
• ASTM D914 - Test Methods for Ethylcellulose
• ASTM D3516 - Test Methods for Ashing Cellulose
• ASTM E473 - Terminology Relating to Thermal Analysis and Rheology
• ASTM E1131 - Test Method for Compositional Analysis by Thermogravimetry
• ASTM E1142 - Terminology Relating to Thermophysical Properties
• ASTM E1582 - Test Method for Temperature Calibration of Thermogravimetric Analyzers
• ASTM E2040 - Test Method for Mass Scale Calibration of Thermogravimetric Analyzers
• ASTM E3142 - Test Method for Thermal Lag of Thermal Analysis Apparatus
• United States Pharmacopeia (USP) Section 281 - Procedures for Residue on Ignition

Practical Value

Using ASTM E2403-23 provides:

• Accurate quantification of metal impurities, crucial for product safety and performance.
• Standardized procedures for international consistency and reproducibility.
• Enhanced quality control by detecting potential contamination or deviations during production.
• Valuable data for research, supporting innovation and compliance across chemical, pharmaceutical, and polymer industries.

By implementing this method, organizations ensure precise sulfated ash determination, driving product quality and regulatory alignment.

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: E2403 − 23
Standard Test Method for
Sulfated Ash of Organic Materials by Thermogravimetry
This standard is issued under the fixed designation E2403; 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* E1142 Terminology Relating to Thermophysical Properties
E1582 Test Method for Temperature Calibration of Thermo-
1.1 This test method describes the determination of sulfated
gravimetric Analyzers
ash content (sometimes called residue-on-ignition) of organic
E2040 Test Method for Mass Scale Calibration of Thermo-
materials by thermogravimetry. This test method converts
gravimetric Analyzers
common metals found in organic materials (such as sodium,
E3142 Test Method for Thermal Lag of Thermal Analysis
potassium, lithium, calcium, magnesium, zinc, and tin) into
Apparatus
their sulfate salts permitting estimation of their total content as
sulfates or oxides. The range of this test method is from 0.1 % 2.2 Other Standards:
to 100 % metal content. The United States Pharmacopeia XXII and The National
Formulary XVII, United States Pharmacopeial
1.2 The values stated in SI units are to be regarded as
Convention, Rockville, MD, 1990, Section 281, p. 1527
standard. No other units of measurement are included in this
standard.
3. Terminology
1.3 This standard does not purport to address all of the
3.1 Definitions—Technical terms used in this standard are
safety concerns, if any, associated with its use. It is the
defined in Terminologies E473 and E1142.
responsibility of the user of this standard to establish appro-
3.1.1 residue-on-ignition, ROI, n—a commonly used alias
priate safety, health, and environmental practices and deter-
for sulfated ash.
mine the applicability of regulatory limitations prior to use.
1.4 This international standard was developed in accor- 3.1.2 sulfated ash, n—the residue remaining after a speci-
dance with internationally recognized principles on standard- men has been oxidized, and the residue subsequently treated
ization established in the Decision on Principles for the with sulfuric acid and heated to constant weight.
Development of International Standards, Guides and Recom-
3.1.3 volatiles, n—for the purpose of this test, those mate-
mendations issued by the World Trade Organization Technical
rials evolving as gas at temperatures below 160 °C in an air
Barriers to Trade (TBT) Committee.
atmosphere.
2. Referenced Documents
4. Summary of Test Method
2.1 ASTM Standards:
4.1 A test specimen is ignited and burned in an air atmo-
D874 Test Method for Sulfated Ash from Lubricating Oils
sphere at temperatures up to 600 °C until only ash remains.
and Additives
After cooling, the residue is treated with sulfuric acid and
D914 Test Methods for Ethylcellulose
heated to 800 °C to constant weight. The residue remaining is
D3516 Test Methods for Ashing Cellulose
identified as sulfated ash.
E473 Terminology Relating to Thermal Analysis and Rhe-
ology 4.2 This test method is similar to Test Method D874 for
lubricating oils and additives, Test Methods D914 for ethyl
E1131 Test Method for Compositional Analysis by Thermo-
gravimetry cellulose, Test Methods D3516 cellulose, and that of The
United States Pharmacopeia XXII and makes use of thermo-
gravimetric apparatus to perform the determination.
This test method is under the jurisdiction of ASTM Committee E37 on Thermal
Measurements and is the direct responsibility of Subcommittee E37.01 on Calo-
rimetry and Mass Loss.
5. Significance and Use
Current edition approved Aug. 1, 2023. Published August 2023. Originally
5.1 The sulfated ash value indicates the level of known
approved in 2004. Last previous edition approved in 2018 as E2403 – 06 (2018).
DOI: 10.1520/E2403-23.
metal-containing additives or impurities in an organic material.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
When phosphorus is absent, barium, calcium, magnesium,
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
sodium and potassium are converted to their sulfates. Tin and
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. zinc are converted to their oxides.
*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
E2403 − 23
5.2 This test method may be used for research and 10.2 Perform any cleaning and calibration procedures de-
development, specification acceptance, and quality assurance scribed by the manufacturer in the apparatus Operator’s
purposes. Manual.
6. Interferences
11. Calibration and Standardization
6.1 If phosphorus is present with metals, it partially or
11.1 Perform temperature calibration of the thermogravi-
wholly remains in the sulfated ash as metal phosphates.
metric analyzer according to Test Method E1582 using refer-
6.2 Sulfur and chlorides do not interfere.
ence materials suitable for the temperature range of this
method, namely 25 °C to 800 °C (see Appendix X1).
7. Apparatus
11.2 Perform mass calibration of the thermogravimetric
7.1 Thermogravimetric Analyzer (TGA)—The essential in-
analyzer according to Test Method E2040.
strumentation required to provide the minimum thermogravi-
metric analytical capability for this test method includes:
NOTE 1—Committee E37 recommends calibration, or calibration
7.1.1 A thermobalance composed of:
verification, of all signals at least annually.
7.1.1.1 A furnace to provide uniform controlled heating of a
specimen to a constant temperature of 850 °C and at a constant 12. Procedure
rate of 5 °C ⁄min to 60 °C ⁄min
12.1 Transfer 30 mg to 40 mg of the sample into a tared,
7.1.1.2 A temperature sensor to provide an indication of the
clean, and dry sample container. Assemble the thermogravi-
specimen or furnace temperature readable to 61 °C.
metric analyzer for operation. Record the initial weight of the
7.1.1.3 A continuously recording balance to measure the
test specimen as W to within 60.01 mg
o
specimen mass with a minimum capacity of 50 mg readable to
NOTE 2—The sample container may be preconditioned by heating in an
60.01 mg.
air atmosphere to 800 °C.
7.1.1.4 A means of maintaining the specimen or container
NOTE 3—Smaller quantities of test specimen will reduce the quantifi-
under atmospheric control of air at a purge flow rate of
cation capability of this method.
50 mL ⁄min to 100 mL/min 6 5 mL/min.
12.2 Heat the specimen from ambient to 600 °C at
7.1.2 A temperature controller capable of executing a spe-
10 °C ⁄min under an air purge gas with a flow rate of
cific temperature program by operating the furnace between
50 mL ⁄min to 100 mL ⁄min 6 5 mL/min and record the ther-
selected temperature limit at a rate of 5 °C ⁄min to 60 °C ⁄min
mal curve.
and to an isothermal temperature of up to 850 °C which is
maintained constant to 610 °C for a minimum of 70 min.
12.3 Cool the heated sample and thermogravimetric appa-
7.1.3 A data collection device, to provide a means of
ratus to 20 °C to 25 °C.
acquiring, storing, and displaying measured or calculated
12.4 If desired, record the weight at 150 °C (W ) as the mass
v
signals, or both. The minimum output signals required for TGA
after apparent loss of volatiles. Record the weight at 600 °C as
are mass, temperature, and time.
the mass of the residue (W ).
r
7.1.4 Containers (pans, crucibles, etc.) that are inert to the
specimen and to concentrated sulfuric acid and that will remain
NOTE 4—Mass loss due to apparent loss of volatiles at 150 °C and
gravimetrically stable up to 850 °C. Platinum is a common residue at 600 °C are not required for the sulfated ash determination but
may be recorded for additional sample characterization (see Test Method
material of construction for this purpose.
E113
...

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: E2403 − 06 (Reapproved 2018) E2403 − 23
Standard Test Method for
Sulfated Ash of Organic Materials by Thermogravimetry
This standard is issued under the fixed designation E2403; 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 Scope*
1.1 This test method describes the determination of sulfated ash content (sometimes called residue-on-ignition) of organic
materials by thermogravimetry. This test method converts common metals found in organic materials (such as sodium, potassium,
lithium, calcium, magnesium, zinc, and tin) into their sulfate salts permitting estimation of their total content as sulfates or oxides.
The range of this test method is from 0.10.1 % to 100 % metal content.
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.
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:
D874 Test Method for Sulfated Ash from Lubricating Oils and Additives
D914 Test Methods for Ethylcellulose
D3516 Test Methods for Ashing Cellulose
E473 Terminology Relating to Thermal Analysis and Rheology
E1131 Test Method for Compositional Analysis by Thermogravimetry
E1142 Terminology Relating to Thermophysical Properties
E1582 Test Method for Temperature Calibration of Thermogravimetric Analyzers
E2040 Test Method for Mass Scale Calibration of Thermogravimetric Analyzers
E3142 Test Method for Thermal Lag of Thermal Analysis Apparatus
2.2 Other Standards:
The United States Pharmacopeia XXII and The National Formulary XVII, United States Pharmacopeial Convention, Rockville,
MD, 1990, Section 281, p. 1527
3. Terminology
3.1 Definitions—Technical terms used in this standard are defined in Terminologies E473 and E1142.
This test method is under the jurisdiction of ASTM Committee E37 on Thermal Measurements and is the direct responsibility of Subcommittee E37.01 on Calorimetry
and Mass Loss.
Current edition approved April 1, 2018Aug. 1, 2023. Published May 2018August 2023. Originally approved in 2004. Last previous edition approved in 20122018 as
E2403 – 06 (2012).(2018). DOI: 10.1520/E2403-06R18.10.1520/E2403-23.
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.
*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
E2403 − 23
3.1.1 residue-on-ignition, ROI, n—a commonly used alias for sulfated ash.
3.1.2 sulfated ash, n—the residue remaining after a specimen has been oxidized, and the residue subsequently treated with sulfuric
acid and heated to constant weight.
3.1.2 residue-on-ignition, ROI, n—a commonly used alias for sulfated ash.
3.1.3 volatiles, n—for the purpose of this test, those materials evolving as gas at temperatures below 160°C160 °C in an air
atmosphere.
4. Summary of Test Method
4.1 A test specimen is ignited and burned in an air atmosphere at temperatures up to 600°C600 °C until only ash remains. After
cooling, the residue is treated with sulfuric acid and heated to 800°C800 °C to constant weight. The residue remaining is identified
as sulfated ash.
4.2 This test method is similar to Test Method D874 for lubricating oils and additives, Test Methods D914 for ethyl cellulose, Test
Methods D3516 cellulose, and that of The United States Pharmacopeia XXII and makes use of thermogravimetric apparatus to
perform the determination.
5. Significance and Use
5.1 The sulfated ash may be used to indicate value indicates the level of known metal-containing additives or impurities in an
organic material. When phosphorus is absent, barium, calcium, magnesium, sodium and potassium are converted to their sulfates.
Tin and zinc are converted to their oxides.
5.2 This test method may be used for research and development, specification acceptance, and quality assurance purposes.
6. Interferences
6.1 If phosphorus is present with metals, it partially or wholly remains in the sulfated ash as metal phosphates.
6.2 Sulfur and chlorides do not interfere.
7. Apparatus
7.1 Thermogravimetric Analyzer (TGA)—(TGA)—The essential instrumentation required to provide the minimum thermogravi-
metric analytical capability for this test method includes:
7.1.1 A thermobalance composed of:
7.1.1.1 A furnace to provide uniform controlled heating of a specimen to a constant temperature of 850°C850 °C and at a constant
rate of 55 °C ⁄min to 60°C/min60 °C ⁄min
7.1.1.2 A temperature sensor to provide an indication of the specimen or furnace temperature readable to 61°C.61 °C.
7.1.1.3 A continuously recording balance to measure the specimen mass with a minimum capacity of 50 mg and a sensitivity of
readable to 60.01 mg.
7.1.1.4 A means of maintaining the specimen or container under atmospheric control of air at a purge flow rate of 5050 mL ⁄min
to 100 mL/min 6 5 mL/min.
7.1.2 A temperature controller capable of executing a specific temperature program by operating the furnace between selected
temperature limit at a rate of 55 °C ⁄min to 60°C/min60 °C ⁄min and to an isothermal temperature of up to 850°C850 °C which is
maintained constant to 610°C610 °C for a minimum of 70 minutes.min.
E2403 − 23
7.1.3 A recording data collection device, capable of recording and displaying any fraction of the specimen mass signal (TGA
curve) including signal noise. to provide a means of acquiring, storing, and displaying measured or calculated signals, or both. The
minimum output signals required for TGA are mass, temperature, and time.
7.1.4 Containers (pans, crucibles, etc.) that are inert to the specimen and to concentrated sulfuric acid and that will remain
gravimetrically stable up to 850°C.850 °C. Platinum is a common material of construction for this purpose.
7.2 Graduated micropipette with capacity of 40–50 40 μL to 50 μL
8. Reagents and Materials
8.1 Sulfuric acid, concentrated (98 %), with a relative density of 1.84. (Warning—Poison. Corrosive. Strong Oxidizer.)
8.2 Air—Zero grade or better purity
9. Hazards
9.1 Sulfuric acid may be corrosive to some thermogravimetric apparatus. A regular visual inspection of the apparatus will
determine if any corrosion is taking place.
9.2 The exhausted purge gas from the apparatus will contain sulfuric acid fumes. This purge gas shall be treated by exhausting
to aan acid hood or by bubbling through a solution of sodium bicarbonate to absorb the acidic fumes.
10. Preparation of Apparatus
10.1 After turning the power on, allow the instrument to equilibrate for at least one hour prior to any measurements.
10.2 Perform any cleaning and calibration procedures described by the manufacturer in the apparatus Operator’s Manual.
11. Calibration and Standardization
11.1 Perform temperature calibration of the thermogravimetric analyzer according to Test Method E1582 using reference materials
suitable for the temperature range of this method, namely 25 to 800°C.25 °C to 800 °C (see Appendix X1).
11.2 Perform mass calibration of the thermogravimetric analyzer according to Test Method E2040.
NOTE 1—Committee E37 recommends calibration, or calibration verification, of all signals at least annually.
12. Procedure
12.1 Transfer 3030 mg to 40 mg of the sample into a tared, clean, and dry sample container. Asse
...