ASTM D4952-23

Standard Test Method for Qualitative Analysis for Active Sulfur Species in Fuels and Solvents (Doctor Test)

SIGNIFICANCE AND USE
5.1 Sulfur present as mercaptans or as hydrogen sulfide in distillate fuels and solvents can attack many metallic and non-metallic materials in fuel and other distribution systems. A negative result in the doctor test ensures that the concentration of these compounds is insufficient to cause such problems in normal use.
SCOPE
1.1 This test method covers and is intended primarily for the detection of mercaptans in motor fuel, kerosine, and similar petroleum products. This method may also provide information on hydrogen sulfide and elemental sulfur that may be present in these sample types.  
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.  For specific warning statements, see 7.3.  
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: 30-Jun-2023
• ICS: 75.080 - Petroleum products in general
• ICS: 75.160.20 - Liquid fuels
• Technical Committee: D02 - Petroleum Products, Liquid Fuels, and Lubricants
• Drafting Committee: D02.03 - Elemental Analysis

Relations

• Refers: ASTM D3227-24 - Standard Test Method for (Thiol Mercaptan) Sulfur in Gasoline, Kerosine, Aviation Turbine, and Distillate Fuels (Potentiometric Method)
• Effective Date: 01-Mar-2024
• Refers: ASTM D4175-23a - Standard Terminology Relating to Petroleum Products, Liquid Fuels, and Lubricants
• Effective Date: 15-Dec-2023
• Refers: ASTM D4175-23e1 - Standard Terminology Relating to Petroleum Products, Liquid Fuels, and Lubricants
• Effective Date: 01-Jul-2023
• Refers: ASTM D3227-13 - Standard Test Method for (Thiol Mercaptan) Sulfur in Gasoline, Kerosine, Aviation Turbine, and Distillate Fuels (Potentiometric Method)
• Effective Date: 15-Jun-2013
• Refers: ASTM D1193-06 - Standard Specification for Reagent Water
• Effective Date: 01-Mar-2006
• Refers: ASTM D3227-04a(2010) - Standard Test Method for (Thiol Mercaptan) Sulfur in Gasoline, Kerosine, Aviation Turbine, and Distillate Fuels (Potentiometric Method)
• Effective Date: 01-Nov-2004
• Refers: ASTM D3227-04a - Standard Test Method for (Thiol Mercaptan) Sulfur in Gasoline, Kerosine, Aviation Turbine, and Distillate Fuels (Potentiometric Method)
• Effective Date: 01-Nov-2004
• Refers: ASTM D3227-04 - Standard Test Method for (Thiol Mercaptan) Sulfur in Gasoline, Kerosine, Aviation Turbine, and Distillate Fuels (Potentiometric Method)
• Effective Date: 01-May-2004
• Refers: ASTM D3227-02a - Standard Test Method for (Thiol Mercaptan) Sulfur in Gasoline, Kerosine, Aviation Turbine, and Distillate Fuels (Potentiometric Method)
• Effective Date: 10-Nov-2002
• Refers: ASTM D3227-00 - Standard Test Method for (Thiol Mercaptan) Sulfur in Gasoline, Kerosine, Aviation Turbine, and Distillate Fuels (Potentiometric Method)
• Effective Date: 10-Apr-2002
• Refers: ASTM D3227-02 - Standard Test Method for (Thiol Mercaptan) Sulfur in Gasoline, Kerosine, Aviation Turbine, and Distillate Fuels (Potentiometric Method)
• Effective Date: 10-Apr-2002
• Refers: ASTM D1193-99 - Standard Specification for Reagent Water
• Effective Date: 10-Feb-1999
• Refers: ASTM D1193-99e1 - Standard Specification for Reagent Water
• Effective Date: 10-Feb-1999

Overview

ASTM D4952-23: Standard Test Method for Qualitative Analysis for Active Sulfur Species in Fuels and Solvents (Doctor Test) provides a qualitative procedure for detecting mercaptans, hydrogen sulfide, and elemental sulfur in motor fuel, kerosine, and similar petroleum products. The Doctor Test is widely used in the petroleum industry to identify active sulfur species that can compromise distribution systems, fuel performance, and equipment durability. A negative result assures users that sulfur compounds are present at concentrations unlikely to cause operational problems or material degradation.

Key Topics

• Detection Focus: Primarily identifies the presence of mercaptans, but also provides information on hydrogen sulfide and elemental sulfur content in fuels and solvents.
• Test Procedure: The sample is mixed with sodium plumbite solution and powdered sulfur. Discoloration indicates the presence of active sulfur species.
• Interpretation:
  • A positive result (discoloration or masking of sulfur layer color) means the sample is "sour" and contains undesirable sulfur compounds.
  • A negative result (bright yellow or only slightly discolored sulfur layer) categorizes the sample as "sweet", suitable for use.
• Sample Handling: Proper collection and prompt testing are vital. Samples should be shielded from UV light to prevent peroxide formation, which can interfere with test accuracy.
• Interferences: The presence of peroxides can result in false positives. There are prescribed checks for peroxide interference, and affected samples must be retested.
• Safety Considerations: The test uses hazardous chemicals (such as sodium plumbite, which contains lead), emphasizing strict safety, health, and environmental precautions.

Applications

This test method is critical across several sectors:

• Petroleum Refining and Distribution: Ensures that fuels meet quality standards for sulfur content before distribution, reducing risks to storage and pipeline infrastructure.
• Fuel Quality Control: Used by laboratories and fuel suppliers to quickly classify fuels as "sour" or "sweet", impacting blending decisions and downstream usage.
• Material Protection: Limiting active sulfur species protects both metallic and non-metallic materials against corrosive attack, prolonging equipment life.
• Regulatory Compliance: Supports compliance with fuel and environmental regulations regarding sulfur content in fuels and solvents.
• Solvent and Additive Manufacturing: Verifies the suitability of solvents and additives used in industrial and chemical processes.

Related Standards

ASTM D4952-23 references several related documents and methods for comprehensive fuel analysis:

• ASTM D1193 - Specification for Reagent Water
  Defines water quality requirements for laboratory testing.
• ASTM D3227 - Test Method for (Thiol Mercaptan) Sulfur in Gasoline, Kerosine, Aviation Turbine, and Distillate Fuels (Potentiometric Method)
  Offers quantitative analysis for mercaptans, complementing the qualitative Doctor Test.
• ASTM D4175 - Terminology Relating to Petroleum Products, Liquid Fuels, and Lubricants
  Standardized terms for consistent communication in fuel analysis.
• Energy Institute IP 30 - Detection of Mercaptans, Hydrogen Sulfide, Elemental Sulfur, and Peroxides (Doctor Test Method)
  An international equivalent for broader applicability beyond ASTM standards.

Summary

The ASTM D4952-23 (Doctor Test) is an essential qualitative analytical method for detecting problematic sulfur species in fuels and solvents. Its implementation helps maintain product integrity, protect system components, and ensure compliance with industry regulations. Accurate sulfur detection with the Doctor Test promotes safe, reliable, and efficient fuel handling across the oil, gas, and chemical sectors.

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: D4952 − 23
Standard Test Method for
Qualitative Analysis for Active Sulfur Species in Fuels and
Solvents (Doctor Test)
This standard is issued under the fixed designation D4952; 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.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1. Scope* 2.2 Energy Institute Standards:
IP 30 Detection of Mercaptans, Hydrogen Sulfide, Elemental
1.1 This test method covers and is intended primarily for the
Sulfur, and Peroxides – Doctor Test Method
detection of mercaptans in motor fuel, kerosine, and similar
petroleum products. This method may also provide information
3. Terminology
on hydrogen sulfide and elemental sulfur that may be present in
3.1 Definitions:
these sample types.
3.1.1 For definitions of terms used in this test method, refer
1.2 The values stated in SI units are to be regarded as
to Terminology D4175.
standard. No other units of measurement are included in this
3.2 Definitions of Terms Specific to This Standard:
standard.
3.2.1 flowers of sulfur, n—a purified form of sulfur that is
1.3 This standard does not purport to address all of the
prepared by sublimation, as opposed to precipitation.
safety concerns, if any, associated with its use. It is the
3.2.2 sour, adj—describing material having a detectable
responsibility of the user of this standard to establish appro-
quantity of hydrogen sulfide or mercaptan.
priate safety, health, and environmental practices and deter-
3.2.3 sweet, adj—describing material having a nondetect-
mine the applicability of regulatory limitations prior to use.
able quantity of hydrogen sulfide or mercaptan.
For specific warning statements, see 7.3.
1.4 This international standard was developed in accor- 3.3 Acronyms:
3.3.1 UV, adj—ultraviolet, the spectrum of electromagnetic
dance with internationally recognized principles on standard-
ization established in the Decision on Principles for the radiation commonly defined as having a wavelength between
100 and 400 nanometers.
Development of International Standards, Guides and Recom-
mendations issued by the World Trade Organization Technical
3.3.1.1 Discussion—In the context of this test method, the
Barriers to Trade (TBT) Committee.
term of UV is expanded to include wavelengths up to 550 nm
for the reason discussed in 8.1.
2. Referenced Documents
4. Summary of Test Method
2.1 ASTM Standards:
D1193 Specification for Reagent Water
4.1 The sample is shaken with sodium plumbite solution, a
D3227 Test Method for (Thiol Mercaptan) Sulfur in
small quantity of powdered sulfur added, and the mixture
Gasoline, Kerosine, Aviation Turbine, and Distillate Fuels
shaken again. The presence of mercaptans or hydrogen sulfide
(Potentiometric Method)
or both is indicated by discoloration of the sulfur floating at the
D4175 Terminology Relating to Petroleum Products, Liquid
oil-water interface or by discoloration of either of the phases.
Fuels, and Lubricants
5. Significance and Use
5.1 Sulfur present as mercaptans or as hydrogen sulfide in
This test method is under the jurisdiction of ASTM Committee D02 on distillate fuels and solvents can attack many metallic and
Petroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility of
non-metallic materials in fuel and other distribution systems. A
Subcommittee D02.03 on Elemental Analysis.
negative result in the doctor test ensures that the concentration
Current edition approved July 1, 2023. Published July 2023. Originally approved
of these compounds is insufficient to cause such problems in
in 1989. Last previous edition approved in 2017 as D4952 – 12 (2017). DOI:
10.1520/D4952-23.
normal use.
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 Available from Energy Institute, 61 New Cavendish St., London, WIG 7AR,
the ASTM website. U.K., http://www.energyinst.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
D4952 − 23
NOTE 1—Alternative volumes of the solution may be prepared or
6. Interferences
purchased, provided the final solution concentration is equivalent.
6.1 This test cannot be used if there are more than trace
7.4 Sulfur—Pure, sublimed, stored in a closed container.
amounts of peroxides in the test sample. Peroxides can give a
false positive results where mercaptans are at low level or not 7.5 Potassium Iodide, approximately 100 g ⁄L Solution—
even present. Dissolve approximately 1 g of potassium iodide in approxi-
mately 10 mL of water. Prepare fresh for each test.
6.2 To check if peroxides are present in sufficient concen-
tration to invalidate the test, shake 10 mL 6 0.5 mL of a fresh 7.6 Acetic Acid, approximately 100 g ⁄L Solution—Add ap-
portion of the sample with approximately 2 mL of the potas- proximately 10 mL of glacial acetic acid to approximately
sium iodide solution, add two drops of the acetic acid solution, 100 mL water.
and two drops of the starch solution. If the aqueous layer turns
7.7 Starch Indicator, approximately 5 g ⁄L Indicator
a blue color, this confirms the presence of peroxides in
Solution—Prepare fresh each time of testing.
sufficient quantity to invalidate the test, and the test on this
sample should be discontinued. Proceed in accordance with
8. Sampling and Handling of Test Samples
6.4.
8.1 Improper choice of clear glass sample bottles followed
6.3 Alternatively, one may choose to perform a preliminary
by exposure to sunlight or fluorescent lighting emitting UV
Doctor Test. If a brown precipitate slowly forms, peroxide is
wavelengths shorter than 550 nm in the laboratory can generate
probably present. Proceed in accordance with 6.2 to confirm
peroxides in cracked gasolines as well as finished batches of
presence of peroxides at sufficient quantity to invalidate the
gasolines. Peroxides are generated in proportion to the head-
test.
space air volume and time of exposure. It has been reported
that peroxides can interfere with the Doctor Test—see 6.1.
6.4 If interference from peroxides is confirmed, proceed to
re-sample and retest. Ensure that sampling and handling 8.2 It is preferable to collect the field samples using dark
procedures for the new sample prevent UV light exposures as
brown/amber bottles or metal cans, or if using clear glass
prescribed in 8.1. None of the normal refinery units or blending bottles to wrap them in foil or place in a light-tight box to
processes producing spark ignition motor fuels are known to
prevent UV light exposure.
create peroxides under normal operating conditions.
8.3 The samples should be tested without delay upon receipt
in the laboratory before further chemical interactions take
7. Reagents and Materials
place.
7.1 Purity of Reagents—Reagent grade chemicals shall be
used in all tests. Unless otherwise indicated, it is intended that
9. Procedure
all reagents conform
...

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: D4952 − 12 (Reapproved 2017) D4952 − 23
Standard Test Method for
Qualitative Analysis for Active Sulfur Species in Fuels and
Solvents (Doctor Test)
This standard is issued under the fixed designation D4952; 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.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1. Scope Scope*
1.1 This test method covers and is intended primarily for the detection of mercaptans in motor fuel, kerosine, and similar
petroleum products. This method may also provide information on hydrogen sulfide and elemental sulfur that may be present in
these sample types.
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 and healthsafety, health, and environmental practices and determine
the applicability of regulatory limitations prior to use. For specific warning statements, see 7.3.
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:
D1193 Specification for Reagent Water
D3227 Test Method for (Thiol Mercaptan) Sulfur in Gasoline, Kerosine, Aviation Turbine, and Distillate Fuels (Potentiometric
Method)
D4175 Terminology Relating to Petroleum Products, Liquid Fuels, and Lubricants
2.2 Energy Institute Standards:
IP 30 Detection of Mercaptans, Hydrogen Sulfide, Elemental Sulfur, and Peroxides – Doctor Test Method
3. Terminology
3.1 Definitions:
3.1.1 For definitions of terms used in this test method, refer to Terminology D4175.
3.2 Definitions of Terms Specific to This Standard:
This test method is under the jurisdiction of ASTM Committee D02 on Petroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility of Subcommittee
D02.03 on Elemental Analysis.
Current edition approved May 1, 2017July 1, 2023. Published June 2017July 2023. Originally approved in 1989. Last previous edition approved in 20122017 as
D4952 – 12.D4952 – 12 (2017). DOI: 10.1520/D4952-12R17.10.1520/D4952-23.
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.
Available from Energy Institute, 61 New Cavendish St., London, WIG 7AR, U.K., http://www.energyinst.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
D4952 − 23
3.2.1 flowers of sulfur, n—a purified form of sulfur that is prepared by sublimation, as opposed to precipitation.
3.2.2 sour, adj—describing material having a detectable quantity of hydrogen sulfide or mercaptan.
3.2.3 sweet, adj—describing material having a nondetectable quantity of hydrogen sulfide or mercaptan.
3.3 Acronyms:
3.3.1 UV, adj—ultraviolet, the spectrum of electromagnetic radiation commonly defined as having a wavelength between 100 and
400 nanometers.
3.3.1.1 Discussion—
In the context of this test method, the term of UV is expanded to include wavelengths up to 550 nm for the reason discussed in
8.1.
4. Summary of Test Method
4.1 The sample is shaken with sodium plumbite solution, a small quantity of powdered sulfur added, and the mixture shaken again.
The presence of mercaptans or hydrogen sulfide or both is indicated by discoloration of the sulfur floating at the oil-water interface
or by discoloration of either of the phases.
5. Significance and Use
5.1 Sulfur present as mercaptans or as hydrogen sulfide in distillate fuels and solvents can attack many metallic and non-metallic
materials in fuel and other distribution systems. A negative result in the doctor test ensures that the concentration of these
compounds is insufficient to cause such problems in normal use.
6. Interferences
6.1 This test cannot be used if there are more than trace amounts of peroxides in the test sample. Peroxides can give a false positive
results where mercaptans are at low level or not even present.
6.2 To check if peroxides are present in sufficient concentration to invalidate the test, shake 10 mL 6 0.5 mL of a fresh portion
of the sample with approximately 2 mL of the potassium iodide solution, add two drops of the acetic acid solution, and two drops
of the starch solution. If the aqueous layer turns a blue color, this confirms the presence of peroxides in sufficient quantity to
invalidate the test, and the test on this sample should be discontinued. Proceed in accordance with 5.46.4.
6.3 Alternatively, one may choose to perform a preliminary Doctor Test. If a brown precipitate slowly forms, peroxide is probably
present. Proceed in accordance with 5.26.2 to confirm presence of peroxides at sufficient quantity to invalidate the test.
6.4 If interference from peroxides is confirmed, proceed to re-sample and retest. Ensure that sampling and handling procedures
for the new sample prevent UV light exposures as prescribed in 7.18.1. None of the normal refinery units or blending processes
producing spark ignition motor fuels are known to create peroxides under normal operating conditions.
7. Reagents and Materials
7.1 Purity of Reagents—Reagent grade chemicals shall be used in all tests. Unless otherwise indicated, it is intended that all
reagents conform to the specifications of the Committee on Analytical Reagents of the American Chemical Society where such
specifications are available. Other grades may be used, provided it is first ascertained that the reagent is of sufficiently high purity
to permit its use without lessening the accuracy of the determination.
Brooks, B. T., “Sodium Plumbite or Doctor Test of Gasolines,” Industrial and Engineering Chemistry, Vol 16, No. 6, June 1924, p. 588.
Reagent Chemicals, American Chemical Society Specifications, ACS Reagent Chemicals, Specifications and Procedures for Reagents and Standard-Grade Reference
Materials, American Chemical Society, Washington, DC. For suggestions on the testing of reagents not listed by the American Chemical Society, see Analar Standards for
Laboratory Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia and National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC),
Rockville, MD.
D4952 − 23
7.2 Purity of Water—Unless otherwise indicated, references to water shall be understood to mean reagent water as defined by
Types II or III of Specification D1193.
7.3 Doctor (Sodium Plumbite) Solution—(Warning—Poisonous and suspect carcinogen.) Dissolve approximately 125 g of
sodium hydroxide (NaOH) in 1 L of reagent water. Add 60 g of lead monoxide (PbO) and shake vigorously for 15 min,
...