ASTM D3228-22

Standard Test Method for Total Nitrogen in Lubricating Oils and Fuel Oils by Modified Kjeldahl Method

SIGNIFICANCE AND USE
5.1 The concentration of nitrogen is a measure of the presence of nitrogen-containing additives. Knowledge of its concentration can be used to predict performance.
SCOPE
1.1 This test method covers the determination of nitrogen in lubricating oils when present in the concentration from 0.03 % to 0.10 % by mass, and for the determination of nitrogen in fuel oils when present in the concentration from 0.015 % to 2.0 % by mass. This test method is also applicable to the analysis of additive concentrates and additive packages.  
Note 1: This test method may not be applicable to certain materials containing N–O or N–N linkage. However, the samples used in the cooperative program to establish the precision of the test method were compounded with currently available ashless additives containing nitrogen. Complete recovery of the nitrogen present in these additives was obtained.  
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 7.6, 7.9, and 9.8.  
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-Sep-2022
• ICS: 75.100 - Lubricants, industrial oils and related products
• ICS: 75.160.20 - Liquid fuels
• Technical Committee: D02 - Petroleum Products, Liquid Fuels, and Lubricants
• Drafting Committee: D02.03 - Elemental Analysis

Relations

• Refers: ASTM D4175-23a - Standard Terminology Relating to Petroleum Products, Liquid Fuels, and Lubricants
• Effective Date: 15-Dec-2023
• Refers: ASTM D6299-23a - Standard Practice for Applying Statistical Quality Assurance and Control Charting Techniques to Evaluate Analytical Measurement System Performance
• Effective Date: 01-Dec-2023
• Refers: ASTM D4175-23e1 - Standard Terminology Relating to Petroleum Products, Liquid Fuels, and Lubricants
• Effective Date: 01-Jul-2023
• Refers: ASTM D6299-17b - Standard Practice for Applying Statistical Quality Assurance and Control Charting Techniques to Evaluate Analytical Measurement System Performance
• Effective Date: 15-Dec-2017
• Refers: ASTM D6299-17a - Standard Practice for Applying Statistical Quality Assurance and Control Charting Techniques to Evaluate Analytical Measurement System Performance
• Effective Date: 15-Nov-2017
• Refers: ASTM D6299-17 - Standard Practice for Applying Statistical Quality Assurance and Control Charting Techniques to Evaluate Analytical Measurement System Performance
• Effective Date: 01-Jan-2017
• Refers: ASTM D6299-13e1 - Standard Practice for Applying Statistical Quality Assurance and Control Charting Techniques to Evaluate Analytical Measurement System Performance
• Effective Date: 01-Oct-2013
• Refers: ASTM D4057-06(2011) - Standard Practice for Manual Sampling of Petroleum and Petroleum Products
• Effective Date: 01-Jun-2011
• Refers: ASTM D6299-10 - Standard Practice for Applying Statistical Quality Assurance and Control Charting Techniques to Evaluate Analytical Measurement System Performance
• Effective Date: 01-Mar-2010
• Refers: ASTM D6299-10e2 - Standard Practice for Applying Statistical Quality Assurance and Control Charting Techniques to Evaluate Analytical Measurement System Performance
• Effective Date: 01-Mar-2010
• Refers: ASTM D6299-09 - Standard Practice for Applying Statistical Quality Assurance and Control Charting Techniques to Evaluate Analytical Measurement System Performance
• Effective Date: 01-Nov-2009
• Refers: ASTM D6299-08 - Standard Practice for Applying Statistical Quality Assurance and Control Charting Techniques to Evaluate Analytical Measurement System Performance
• Effective Date: 15-Oct-2008
• Refers: ASTM D6299-07 - Standard Practice for Applying Statistical Quality Assurance and Control Charting Techniques to Evaluate Analytical Measurement System Performance
• Effective Date: 01-Nov-2007
• Refers: ASTM D6299-07e1 - Standard Practice for Applying Statistical Quality Assurance and Control Charting Techniques to Evaluate Analytical Measurement System Performance
• Effective Date: 01-Nov-2007
• Refers: ASTM D1193-06 - Standard Specification for Reagent Water
• Effective Date: 01-Mar-2006

Overview

ASTM D3228-22 is the Standard Test Method for Total Nitrogen in Lubricating Oils and Fuel Oils by the Modified Kjeldahl Method. Developed by ASTM International, this test method provides a reliable procedure for measuring the concentration of nitrogen in lubricating oils, fuel oils, additive concentrates, and additive packages. The method is significant because nitrogen often originates from specific additives which can impact the performance and compliance of oil products. Accurate determination of total nitrogen content helps quality control and regulatory compliance within the petroleum, lubricant, and fuel industries.

Key Topics

• Test Method Scope:

  • Applicable to lubricating oils with nitrogen concentrations from 0.03% to 0.10% by mass.
  • Applicable to fuel oils with nitrogen concentrations from 0.015% to 2.0% by mass.
  • Suitable for analyzing additive concentrates and additive packages.

• Modified Kjeldahl Method:

  • Involves sample digestion using concentrated sulfuric acid, potassium sulfate, and a suitable catalyst.
  • Followed by conversion of nitrogen compounds to ammonium sulfate, distillation as ammonia, and titration for quantification.
  • Uses only SI units for measurement as standard.

• Significance:

  • The determination of nitrogen in oils helps to measure the presence and amount of nitrogen-based additives.
  • Data from this method assist in predicting oil performance and ensuring product consistency.

• Safety and Compliance:

  • Users must implement appropriate safety, health, and environmental practices during testing.
  • The standard aligns with internationally recognized principles, supporting global compliance and harmonization.

Applications

ASTM D3228-22 is widely used in various practical scenarios, including:

• Quality Control in Manufacturing:

  • Ensures lubricating oils, fuel oils, and additives meet desired nitrogen content specifications.
  • Prevents excess or insufficient additive levels that could impact product effectiveness or stability.

• Product Development and Formulation:

  • Aids research and formulation teams in the development of oils with tailored performance characteristics.
  • Supports the validation of new additive chemistries and blending processes.

• Regulatory Compliance Testing:

  • Provides documented evidence of total nitrogen content for product certification and regulatory filings.
  • Used in conformity assessments during audits and inspections within the oil and fuel industries.

• Performance Prediction:

  • The knowledge of total nitrogen levels helps predict the behavior of oils under operational conditions, influencing maintenance schedules and lifecycle planning.

Related Standards

For effective implementation and better understanding, ASTM D3228-22 references or can be used alongside several related ASTM standards:

• ASTM D1193 - Specification for Reagent Water, crucial for sample preparation.
• ASTM D4057 - Practice for Manual Sampling of Petroleum and Petroleum Products, ensuring representative sample collection.
• ASTM D4175 - Terminology Relating to Petroleum Products, Liquid Fuels, and Lubricants.
• ASTM D6299 - Practice for Applying Statistical Quality Assurance and Control Charting Techniques.
• ASTM E200 - Practice for Preparation, Standardization, and Storage of Standard and Reagent Solutions for Chemical Analysis.

Practical Value

Adopting ASTM D3228-22:

• Enhances precision and repeatability in nitrogen determination for oils and additives.
• Supports international trade and regulatory acceptance through harmonization.
• Improves product consistency and consumer confidence by facilitating stringent quality control.

Keywords: ASTM D3228-22, Kjeldahl Method, total nitrogen, lubricating oils, fuel oils, additive concentrates, quality control, petroleum analysis, nitrogen content testing, oil additive measurement.

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: D3228 −22
Standard Test Method for
Total Nitrogen in Lubricating Oils and Fuel Oils by Modified
Kjeldahl Method
This standard is issued under the fixed designation D3228; 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* D4057 Practice for Manual Sampling of Petroleum and
Petroleum Products
1.1 This test method covers the determination of nitrogen in
D4175 Terminology Relating to Petroleum Products, Liquid
lubricating oils when present in the concentration from 0.03 %
Fuels, and Lubricants
to0.10 %bymass,andforthedeterminationofnitrogeninfuel
D6299 Practice for Applying Statistical Quality Assurance
oils when present in the concentration from 0.015 % to 2.0 %
and Control Charting Techniques to Evaluate Analytical
by mass. This test method is also applicable to the analysis of
Measurement System Performance
additive concentrates and additive packages.
E200 Practice for Preparation, Standardization, and Storage
NOTE 1—This test method may not be applicable to certain materials
of Standard and Reagent Solutions for ChemicalAnalysis
containing N–O or N–N linkage. However, the samples used in the
cooperative program to establish the precision of the test method were
3. Terminology
compounded with currently available ashless additives containing nitro-
3.1 Definitions:
gen. Complete recovery of the nitrogen present in these additives was
obtained. 3.1.1 For definitions of terms used in this test method, refer
to Terminology D4175.
1.2 The values stated in SI units are to be regarded as
3.2 Definitions of Terms Specific to This Standard:
standard. No other units of measurement are included in this
3.2.1 digestion, n—treating a sample with the use of heat or
standard.
elevated pressures, or both, usually in the presence of chemical
1.3 This standard does not purport to address all of the
additives, to bring analytes of interest into solution or to
safety concerns, if any, associated with its use. It is the
remove interfering matrix components, or both.
responsibility of the user of this standard to establish appro-
3.2.1.1 Discussion—In this test method acid, a catalyst and
priate safety, health, and environmental practices and deter-
heat are used to break the carbon nitrogen bonds to form
mine the applicability of regulatory limitations prior to use.
ammonium sulfate.
For specific warning statements, see 7.6, 7.9, and 9.8.
3.2.2 lubricating oil, n—a liquid lubricant, usually compris-
1.4 This international standard was developed in accor-
ing several ingredients, including a major portion of base oil
dance with internationally recognized principles on standard-
and minor portions of various additives.
ization established in the Decision on Principles for the
Development of International Standards, Guides and Recom- 3.2.3 titration, n—quantitative chemical analysis method
mendations issued by the World Trade Organization Technical
used to determine the unknown concentration of a specified
Barriers to Trade (TBT) Committee. element by reacting a solution prepared from the sample to be
analyzed with a known concentration and volume of specific
2. Referenced Documents
reagent.
2.1 ASTM Standards: 3.2.3.1 Discussion—Sensing electrodes or color indicators
D1193 Specification for Reagent Water
can be used to follow titrations if they respond to either the
species being determined or the titrant ion.
This test method is under the jurisdiction of ASTM Committee D02 on
3.2.4 Total Kjeldahl Nitrogen (TKN), n—the sum of the
Petroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility of
nitrogen contained in the free ammonia and other nitrogen
Subcommittee D02.03 on Elemental Analysis.
compounds which are converted to ammonium sulfate
Current edition approved Oct. 1, 2022. Published November 2022. Originally
approved in 1973. Last previous edition approved in 2020 as D3228 – 20. DOI: [(NH ) SO ] under the specified digestion conditions.
4 2 4
10.1520/D3228-22.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or 4. Summary of Test Method
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
4.1 The sample is digested in a mixture of concentrated
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. sulfuric acid, potassium sulfate, and a catalyst of mercuric
*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
D3228 − 22
oxide, titanium dioxide, or copper sulfate. After digestion, 7.6 Sodium Hydroxide Solution (1000 g⁄L)—Dissolve
sodium sulfide is added to precipitate the mercury if used as a 1000 g of sodium hydroxide (NaOH) in 1 L of water.
catalyst, and the mixture is made alkaline with caustic. (Warning—Causes burns. Poison.)
Nitrogen, now in the form of ammonia, is distilled into a boric
7.7 Sodium Sulfide Solution (40 g⁄L)—Dissolve 40 g of
acid solution. The ammonia is titrated with standard sulfuric
sodium sulfide (Na S) in warm water 194 °F (90 °C); cool and
acid using methyl purple as an indicator.
dilute to 1 L.
7.8 Sucrose—High purity reagent (for example, NIST SRM
5. Significance and Use
17f).
5.1 The concentration of nitrogen is a measure of the
7.9 Sulfuric Acid (rel dens 1.84)—Concentrated sulfuric
presence of nitrogen-containing additives. Knowledge of its
concentration can be used to predict performance. acid (H SO ). (Warning—Causes severe burns. Strong oxi-
2 4
dizer.)
6. Apparatus
7.10 SulfuricAcid, Standard(0.05 M)—Slowlyadd3 mLof
6.1 Buret, 50 mL, graduated in 0.1 mLsubdivisions, one for
concentrated sulfuric acid (H SO , rel dens 1.84) to 500 mLof
2 4
each titrant. Other size burettes may also be used.
water in a suitable size beaker. Mix the acid and water; allow
it to cool and transfer to a 1 L volumetric flask. Dilute to the
6.2 Flask, Erlenmeyer, 300 mL. Other sizes are also accept-
mark with water; mix well. Standardize sulfuric acid to the
able.
nearest 0.0005 mol⁄L against 0.1 mol⁄L NaOH solution using
6.3 Heater, electrical or gas.
phenolphthalein indicator. Standardize the NaOH solution
6.4 Kjeldahl Distillation Apparatus.
against primary standard grade potassium hydrogen phthalate
(HOOCC H COOK). Use the procedure outlined in Sections
6 4
NOTE2—CommerciallyavailablesemiautomaticKjeldahlapparatusare
14 to 19 of Practice E200.
acceptable. In such cases manufacturer prescribed sizes of burettes and
flasks may be used.
NOTE 3—Commercially available pre-standardized H SO and NaOH
2 4
6.5 Kjeldahl Flask, at least 500 mL volume.
solutions may be used.
6.6 Kjeldahl Digestion Apparatus. 7.11 Sulfuric Acid (0.005 M)—Prepare by tenfold dilution
of the standard 0.05 M sulfuric acid prepared and standardized
7. Reagents
in 7.10.
7.1 Purity of Reagents—Reagent grade chemicals shall be
7.12 Quality Control (QC) Sample, preferably are portions
used in all tests. Unless otherwise indicated, it is intended that
of one or more liquid petroleum materials that are stable and
all reagents shall conform to the specifications of the Commit-
representative of the samples of interest. These QC samples
tee onAnalytical Reagents of theAmerican Chemical Society,
can be used to check the validity of the testing process as
where such specifications are available. Other grades may be
described in Section 11.
used, provided it is first ascertained that the reagent is of
sufficiently high purity to permit its use without lessening the
8. Sampling
accuracy of the determination.
8.1 Take the sample in accordance with the instructions in
7.2 Purity of Water—Unless otherwise indicated, references
Practice D4057.
to water shall be understood to mean reagent water as defined
8.2 Ensure that the sample is thoroughly representative of
by Types I of Specification D1193.
the material to be tested and that the portion of the sample used
7.3 Boric Acid Solution (40 g⁄L)—Dissolve 40 g of boric
for test is thoroughly representative of the whole sample.
acid (H BO ) in 1 L of boiling water.
3 3
9. Procedure
7.4 Catalyst Reagent—For each test carefully weigh and
9.1 Transfer 1.0 g to 1.5 g of sample, weighed to the nearest
mix 9.9 g of potassium sulfate (K SO ), 0.41 g of mercuric
2 4
0.1 mg, into a Kjeldahl flask.Avoid contact of the sample with
oxide (HgO), and 0.08 g of copper sulfate (CuSO ). Other
the neck of the Kjeldahl flask.Add the catalyst reagent mixture
commercially prepared catalyst for Kjeldahl digestion tablets
to the Kjeldahl flask. Add two or three beads to prevent
or packets that use a catalyst other than mercury may be used.
bumping.
7.5 Methyl Purple Indicator Solution—Aqueous solution
containing approximately 0.1 % active constituent (not methyl NOTE 4—When using commercially prepared Kjeldahl tablets, it is
important to use 1 g of catalyst per 2 mL of sulfuric acid in the digestion.
violet). Other appropriate indicator solutions such as Sher
indicator or an indicator mixture of bromocresol green –
9.2 WashdowntheneckoftheKjeldahlflaskwith20 mLof
methyl red may also be used.
H SO (rel dens 1.84). Swirl the contents of the Kjeldahl flask
2 4
to facilitate the mixing of the sample, catalyst reagent, and
H SO .
3 2 4
ACS Reagent Chemicals, Specifications and Procedures for Reagents and
Standard-Grade Reference Materials, American Chemical Society, Washington,
9.3 Warm the contents of the Kjeldahl flask on the digestion
DC. For suggestions on the testing of reagents not listed by theAmerican Chemical
rack and repeat the swirling. Apply low heat until the frothing
Society, see Analar Standards for Laboratory Chemicals, BDH Ltd., Poole, Dorset,
has stopped. Samples that do not froth or char shall be
U.K., and the United States Pharmacopeia and National Formulary, U.S. Pharma-
copeial Convention, Inc. (USPC), Rockville, MD. subjected to a 20 min low-heating period. Careful periodic
D3228 − 22
swirlingofthesolutionintheKjeldahlflaskshallalsobemade. 9.9.2 Immediately connect the Kjeldahl flask to the distilla-
Gradually apply intermediate heat to raise the temperature of tion apparatus and mix the contents of the Kjeldahl flask
the solution to boiling. thoroughly by swirling. The digestion flask must be connected
to the distillation apparatus immediately after the alkali has
NOTE 5—When using commercial block digestors, swirling of the flask
beenaddedandlayered,butbeforeswirlingtomixtheacidand
is not necessary but use of intermediate heating may be necessary to
alkali. When any mixing is permitted to occur before the
mitigate sample foaming.
digestion flask is connected, the heat generated can be suffi-
9.4 Maintain a minimum volume of 15 mL of liquid in the
cient to release some of the ammonia which can be lost. This
Kjeldahl flask during the digestion period. Add volumes of
loss results in low recovery of ammonia, and thus low values
5mLto15mLofH SO (reldens1.84)whenthevolumedoes
2 4
for the nitrogen content of the sample.
notconformtothiscondition.UsetheH SO towashdownthe
2 4
neck of the Kjeldahl flask after the contents have been allowed 9.10 Promptly apply full heat to the digestion flask. Reduce
to cool sufficiently so that sulfur trioxide (SO ) fumes have
the heat just before the solution begins to boil and maintain at
subsided. The volume of H SO (rel dens 1.84) added will low boiling for 5 min. Heat must be applied promptly to
2 4
depend upon the carbonaceous material in the Kjeldahl flask.
prevent sucking of the H BO solution into the condenser as
3 3
After all of the carbonaceous material has been digested and the digestion solution cools. The initial distillation rate must
the solution has cleared, continue the digestion for two more
not be too rapid because most of the ammonia is distilled
hours at rapid rate of boiling. The total volume of liquid during the first few minutes, and if too large an amount is
remai
...

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: D3228 − 20 D3228 − 22
Standard Test Method for
Total Nitrogen in Lubricating Oils and Fuel Oils by Modified
Kjeldahl Method
This standard is issued under the fixed designation D3228; 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*
1.1 This test method covers the determination of nitrogen in lubricating oils when present in the concentration from 0.03 % to
0.10 % by mass, and for the determination of nitrogen in fuel oils when present in the concentration from 0.015 % to 2.0 % by
mass. This test method is also applicable to the analysis of additive concentrates and additive packages.
NOTE 1—This test method may not be applicable to certain materials containing N–O or N–N linkage. However, the samples used in the cooperative
program to establish the precision of the test method were compounded with currently available ashless additives containing nitrogen. Complete recovery
of the nitrogen present in these additives was obtained.
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 6.67.6, 6.97.9, and 8.89.8.
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
D4057 Practice for Manual Sampling of Petroleum and Petroleum Products
D4175 Terminology Relating to Petroleum Products, Liquid Fuels, and Lubricants
D6299 Practice for Applying Statistical Quality Assurance and Control Charting Techniques to Evaluate Analytical Measure-
ment System Performance
E200 Practice for Preparation, Standardization, and Storage of Standard and Reagent Solutions for Chemical Analysis
3. Terminology
3.1 Definitions:
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 July 1, 2020Oct. 1, 2022. Published July 2020November 2022. Originally approved in 1973. Last previous edition approved in 20192020 as
D3228 – 19.D3228 – 20. DOI: 10.1520/D3228-20.10.1520/D3228-22.
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
D3228 − 22
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:
3.2.1 digestion, n—treating a sample with the use of heat or elevated pressures, or both, usually in the presence of chemical
additives, to bring analytes of interest into solution or to remove interfering matrix components, or both.
3.2.1.1 Discussion—
In this test method acid, a catalyst and heat are used to break the carbon nitrogen bonds to form ammonium sulfate.
3.2.2 lubricating oil, n—a liquid lubricant, usually comprising several ingredients, including a major portion of base oil and minor
portions of various additives.
3.2.3 titration, n—quantitative chemical analysis method used to determine the unknown concentration of a specified element by
reacting a solution prepared from the sample to be analyzed with a known concentration and volume of specific reagent.
3.2.3.1 Discussion—
Sensing electrodes or color indicators can be used to follow titrations if they respond to either the species being determined or the
titrant ion.
3.2.4 Total Kjeldahl Nitrogen (TKN), n—the sum of the nitrogen contained in the free ammonia and other nitrogen compounds
which are converted to ammonium sulfate [(NH ) SO ] under the specified digestion conditions.
4 2 4
4. Summary of Test Method
4.1 The sample is digested in a mixture of concentrated sulfuric acid, potassium sulfate, and a catalyst of mercuric oxide, titanium
dioxide, or copper sulfate. After digestion, sodium sulfide is added to precipitate the mercury if used as a catalyst, and the mixture
is made alkaline with caustic. Nitrogen, now in the form of ammonia, is distilled into a boric acid solution. The ammonia is titrated
with standard sulfuric acid using methyl purple as an indicator.
5. Significance and Use
5.1 The concentration of nitrogen is a measure of the presence of nitrogen-containing additives. Knowledge of its concentration
can be used to predict performance.
6. Apparatus
6.1 Buret, 50 mL, graduated in 0.1 mL subdivisions, one for each titrant. Other size burettes may also be used.
6.2 Flask, Erlenmeyer, 300 mL. Other sizes are also acceptable.
6.3 Heater, electrical or gas.
6.4 Kjeldahl Distillation Apparatus.
NOTE 2—Commercially available semiautomatic Kjeldahl apparatus are acceptable. In such cases manufacturer prescribed sizes of burettes and flasks may
be used.
6.5 Kjeldahl Flask, at least 500 mL volume.
6.6 Kjeldahl Digestion Apparatus.
7. Reagents
7.1 Purity of Reagents—Reagent grade chemicals shall be used in all tests. Unless otherwise indicated, it is intended that all
reagents shall conform to the specifications of the Committee on Analytical Reagents of the American Chemical Society, where
D3228 − 22
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.
7.2 Purity of Water—Unless otherwise indicated, references to water shall be understood to mean reagent water as defined by
Types I of Specification D1193.
7.3 Boric Acid Solution (40 g ⁄L)—Dissolve 40 g of boric acid (H BO ) in 1 L of boiling water.
3 3
7.4 Catalyst Reagent—For each test carefully weigh and mix 9.9 g of potassium sulfate (K SO ), 0.41 g of mercuric oxide (HgO),
2 4
and 0.08 g of copper sulfate (CuSO ). Other commercially prepared catalyst for Kjeldahl digestion tablets or packets that use a
catalyst other than mercury may be used.
7.5 Methyl Purple Indicator Solution—Aqueous solution containing approximately 0.1 % active constituent (not methyl violet).
Other appropriate indicator solutions such as Sher indicator or an indicator mixture of bromocresol green – methyl red may also
be used.
7.6 Sodium Hydroxide Solution (1000 g ⁄L)—Dissolve 1000 g of sodium hydroxide (NaOH) in 1 L of water. (Warning—Causes
burns. Poison.)
7.7 Sodium Sulfide Solution (40 g ⁄L)—Dissolve 40 g of sodium sulfide (Na S) in warm water 194 °F (90 °C); cool and dilute to
1 L.
7.8 Sucrose—High purity reagent (for example, NIST SRM 17f).
7.9 Sulfuric Acid (rel dens 1.84)—Concentrated sulfuric acid (H SO ). (Warning—Causes severe burns. Strong oxidizer.)
2 4
7.10 Sulfuric Acid, Standard (0.05 M)—Slowly add 3 mL of concentrated sulfuric acid (H SO , rel dens 1.84) to 500 mL of water
2 4
in a suitable size beaker. Mix the acid and water; allow it to cool and transfer to a 1 L volumetric flask. Dilute to the mark with
water; mix well. Standardize sulfuric acid to the nearest 0.0005 mol ⁄L against 0.1 mol ⁄L NaOH solution using phenolphthalein
indicator. Standardize the NaOH solution against primary standard grade potassium hydrogen phthalate (HOOCC H COOK). Use
6 4
the procedure outlined in Sections 14 to 19 of Practice E200.
NOTE 3—Commercially available pre-standardized H SO and NaOH solutions may be used.
2 4
7.11 Sulfuric Acid (0.005 M)—Prepare by tenfold dilution of the standard 0.05 M sulfuric acid prepared and standardized in
6.107.10.
7.12 Quality Control (QC) Sample, preferably are portions of one or more liquid petroleum materials that are stable and
representative of the samples of interest. These QC samples can be used to check the validity of the testing process as described
in Section 1011.
8. Sampling
8.1 Take the sample in accordance with the instructions in Practice D4057.
8.2 Ensure that the sample is thoroughly representative of the material to be tested and that the portion of the sample used for test
is thoroughly representative of the whole sample.
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.
D3228 − 22
9. Procedure
9.1 Transfer 1.0 g to 1.5 g of sample, weighed to the nearest 0.1 mg, into a Kjeldahl flask. Avoid contact of the sample with the
neck of the Kjeldahl flask. Add the catalyst reagent mixture to the Kjeldahl flask. Add two or three beads to prevent bumping.
NOTE 4—When using commercially prepared Kjeldahl tablets, it is important to use 1 g of catalyst per 2 mL of sulfuric acid in the digestion.
9.2 Wash down the neck of the Kjeldahl flask with 20 mL of H SO (rel dens 1.84). Swirl the contents of the Kjeldahl flask to
2 4
facilitate the mixing of the sample, catalyst reagent, and H SO .
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9.3 Warm the contents of the Kjeldahl flask on the digestion rack and repeat the swirling. Apply low heat until the frothing has
stopped. Samples that do not froth or char shall be subjected to a 20 min low-heating period. Careful periodic swirling of the
solution in the Kjeldahl flask shall also be made. Gradually apply intermediate heat to raise the temperature of the solution to
boiling.
NOTE 5—When using commercial block digestors, swirling of the flask is not necessary but use of intermediate heating may be necessary to mitigate
sample foaming.
9.4 Maintain a minimum volume of 15 mL of liquid in the Kjeldahl flask during the digestion period. Add volumes of 5 mL to
15 mL of H SO (rel dens 1.84) when the volume does not conform to this condition. Use the H SO to wash down the neck of
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the Kjeldahl flask after the contents have been allowed to cool sufficiently so that sulfur trioxide (SO ) fumes have subsided. The
volume of H SO (rel dens 1.84) added will depend upon the carbonaceous material in the Kjeldahl flask. After all of the
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carbonaceous material has been digested and the solution has cleared, continue the digestion for two more hours at rapid rate of
boiling. The total volume of liquid remaining in the Kjeldahl flask after digestion approximates the volume in the Kjeldahl flask
for the blank.
NOTE 6—For some samples, a two hour digestion period may be unnecessary, if the solution has completely cleared.
9.5 Turn off the heat, but allow the Kjeldahl flask to remain in the fume duct or hood until the evolution of SO fumes has
subsided. Remove the Kjeldahl flask from the rack and cool to approximately room temperature.
9.6 Place a 300 mL receiving flask containing 25 mL of H BO solution and 5 drops of methyl purple indicator solution under the
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condenser with the delivery tube tip extending to the bottom of the receiving flask immersed in the boric acid to minimize any
loss of ammonia during the distillation.
9.7 Measure approximately 275 mL of water and add a portion of this water to the Kjeldahl flask and swirl the contents until the
salt cake has dissolved (Note 2). Add the remainder of the water and cool the contents of the Kjeldahl flask to room temperature.
Alternate volumes of water may be used when using a steam distillation apparatus with block digestion tubes.
NOTE 7—It can be necessary to warm the contents in the Kjeldahl flask to facili
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