ASTM D4294-21

Standard Test Method for Sulfur in Petroleum and Petroleum Products by Energy Dispersive X-ray Fluorescence Spectrometry

SIGNIFICANCE AND USE
5.1 This test method provides rapid and precise measurement of total sulfur in petroleum and petroleum products with a minimum of sample preparation. A typical analysis time is 1 min to 5 min per sample.  
5.2 The quality of many petroleum products is related to the amount of sulfur present. Knowledge of sulfur concentration is necessary for processing purposes. There are also regulations promulgated in federal, state, and local agencies that restrict the amount of sulfur present in some fuels.  
5.3 This test method provides a means of determining whether the sulfur content of petroleum or a petroleum product meets specification or regulatory limits.  
5.4 When this test method is applied to petroleum materials with matrices significantly different from the calibration materials specified in 10.1, the cautions and recommendations in Section 6 should be observed when interpreting results.
SCOPE
1.1 This test method covers the determination of total sulfur in petroleum and petroleum products that are single-phase and either liquid at ambient conditions, liquefiable with moderate heat, or soluble in hydrocarbon solvents. These materials can include diesel fuel, jet fuel, kerosine, other distillate oil, naphtha, residual oil, lubricating base oil, hydraulic oil, crude oil, unleaded gasoline, gasoline-ethanol blends, biodiesel (see Note 2), and similar petroleum products.
Note 1: Oxygenated fuels with ethanol or methanol contents exceeding the limits given in Table 1 can be dealt with using this test method, but the precision and bias statements do not apply (see Appendix X3).
Note 2: For samples with high oxygen contents (>3 % by weight) sample dilution as described in 1.3 or matrix matching must be performed to assure accurate results.  
1.2 Interlaboratory studies on precision revealed the scope to be 17 mg/kg to 4.6 % by mass. An estimate of this test method’s pooled limit of quantitation (PLOQ) is 16.0 mg/kg as calculated by the procedures in Practice D6259. However, because instrumentation covered by this test method can vary in sensitivity, the applicability of the test method at sulfur concentrations below approximately 20 mg/kg must be determined on an individual basis. An estimate of the limit of detection is three times the reproducibility standard deviation, and an estimate of the limit of quantitation2 is ten times the reproducibility standard deviation.  
1.3 Samples containing more than 4.6 % by mass sulfur can be diluted to bring the sulfur concentration of the diluted material within the scope of this test method. Samples that are diluted can have higher errors than indicated in Section 17 than non-diluted samples.  
1.4 Volatile samples (such as high vapor pressure gasolines or light hydrocarbons) may not meet the stated precision because of selective loss of light materials during the analysis.  
1.5 A fundamental assumption in this test method is that the standard and sample matrices are well matched, or that the matrix differences are accounted for (see 6.2). Matrix mismatch can be caused by C/H ratio differences between samples and standards (see Section 6) or by the presence of other heteroatoms.  
1.6 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
1.7 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.  
1.8 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-Nov-2021
• ICS: 75.080 - Petroleum products in general
• 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 D7343-12(2017) - Standard Practice for Optimization, Sample Handling, Calibration, and Validation of X-ray Fluorescence Spectrometry Methods for Elemental Analysis of Petroleum Products and Lubricants
• Effective Date: 01-Jun-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 D6259-98(2010) - Standard Practice for Determination of a Pooled Limit of Quantitation
• Effective Date: 01-Jul-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 D6299-10 - Standard Practice for Applying Statistical Quality Assurance and Control Charting Techniques to Evaluate Analytical Measurement System Performance
• Effective Date: 01-Mar-2010
• Refers: ASTM D6299-09 - 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 E29-08 - Standard Practice for Using Significant Digits in Test Data to Determine Conformance with Specifications
• Effective Date: 01-Oct-2008

Overview

ASTM D4294-21, titled Standard Test Method for Sulfur in Petroleum and Petroleum Products by Energy Dispersive X-ray Fluorescence Spectrometry, is a standard developed by ASTM International. This method specifies procedures for determining total sulfur content in petroleum and petroleum products using energy dispersive X-ray fluorescence (EDXRF) spectrometry. The standard encompasses a wide array of liquid petroleum products, including diesel fuel, gasoline, jet fuel, kerosine, crude oil, lubricating oils, and biodiesel blends.

This technique is widely adopted due to its rapid analysis time-typically 1 to 5 minutes per sample-and minimal sample preparation. The EDXRF method enables reliable measurement of sulfur concentrations, catering to industrial needs and ensuring compliance with regulatory and specification limits.

Key Topics

• Scope of Application

  • Suitable for single-phase petroleum and petroleum products that are liquid at ambient conditions, can be liquefied by moderate heat, or are soluble in hydrocarbon solvents.
  • Applicable matrices include distillate oils, naphtha, residual oils, unleaded gasoline, gasoline-ethanol blends, and hydraulic oils, among others.
  • For fuels with significant oxygen content (>3% by weight), sample dilution or matrix matching is required for accurate sulfur determination.

• Analytical Range and Limitations

  • The method’s typical measurement range is from 17 mg/kg to 4.6% by mass of sulfur.
  • Pooled limit of quantitation (PLOQ) is approximately 16 mg/kg.
  • For sulfur levels above 4.6% by mass, samples can be diluted to fall within the test method's scope.
  • Measurement precision may be reduced for volatile samples, such as light hydrocarbons, due to possible material loss during testing.

• Sample and Calibration Considerations

  • Matrix matching is vital; calibration standards should closely resemble the sample matrix to avoid measurement bias.
  • Interferences from elements like phosphorus, zinc, barium, calcium, chlorine, ethanol, methanol, and others must be considered and compensated for during analysis.
  • Regular use of quality control samples and drift correction standards is recommended for maintaining analytical performance.

• Reporting and Quality Control

  • Results are reported in mg/kg or mass percent, following the requirements for significant figures.
  • Laboratories are encouraged to use statistical quality assurance practices and regular calibration checks to ensure reliability.

Applications

• Regulatory Compliance: The quality and environmental acceptability of fuels are often judged by sulfur content. This test method supports compliance with federal, state, and local sulfur regulations for fuels and petroleum products.
• Quality Control in Refining and Blending: Refineries and fuel distributors utilize ASTM D4294-21 to monitor and adjust sulfur concentrations in fuels, maintaining consistent product quality.
• Routine Analysis: The minimal sample preparation and rapid analysis make EDXRF ideal for routine laboratory and process control environments.
• Product Specification Verification: ASTM D4294-21 provides a practical tool for determining if petroleum products meet internal specifications or customer requirements for sulfur content.

Related Standards

• ASTM D4057 - Practice for Manual Sampling of Petroleum and Petroleum Products
• ASTM D4177 - Practice for Automatic Sampling of Petroleum and Petroleum Products
• ASTM D6259 - Pooled Limit of Quantitation for a Test Method
• ASTM D6299 - Statistical Quality Assurance and Control Charting
• ASTM D7343 - Optimization and Validation of X-ray Fluorescence Methods for Petroleum Products
• ASTM E29 - Use of Significant Digits in Test Data

These related standards enhance guidance on sampling, calibration, data analysis, and statistical quality assurance, ensuring best practices when applying ASTM D4294-21 for sulfur analysis.

---

Keywords: ASTM D4294-21, sulfur determination, petroleum products, energy dispersive X-ray fluorescence, EDXRF, sulfur content, fuel analysis, regulatory compliance, sulfur in fuels, petroleum testing standard

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: D4294 − 21
Standard Test Method for
Sulfur in Petroleum and Petroleum Products by Energy
Dispersive X-ray Fluorescence Spectrometry
This standard is issued under the fixed designation D4294; 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* 1.5 Afundamental assumption in this test method is that the
standard and sample matrices are well matched, or that the
1.1 This test method covers the determination of total sulfur
matrix differences are accounted for (see 6.2). Matrix mis-
in petroleum and petroleum products that are single-phase and
match can be caused by C/H ratio differences between samples
either liquid at ambient conditions, liquefiable with moderate
and standards (see Section 6) or by the presence of other
heat, or soluble in hydrocarbon solvents. These materials can
heteroatoms.
include diesel fuel, jet fuel, kerosine, other distillate oil,
naphtha, residual oil, lubricating base oil, hydraulic oil, crude 1.6 The values stated in SI units are to be regarded as
oil, unleaded gasoline, gasoline-ethanol blends, biodiesel (see standard. No other units of measurement are included in this
Note 2), and similar petroleum products. standard.
1.7 This standard does not purport to address all of the
NOTE 1—Oxygenated fuels with ethanol or methanol contents exceed-
ingthelimitsgiveninTable1canbedealtwithusingthistestmethod,but safety concerns, if any, associated with its use. It is the
the precision and bias statements do not apply (see Appendix X3).
responsibility of the user of this standard to establish appro-
NOTE 2—For samples with high oxygen contents (>3 % by weight)
priate safety, health, and environmental practices and deter-
sample dilution as described in 1.3 or matrix matching must be performed
mine the applicability of regulatory limitations prior to use.
to assure accurate results.
1.8 This international standard was developed in accor-
1.2 Interlaboratory studies on precision revealed the scope
dance with internationally recognized principles on standard-
to be 17 mg⁄kg to 4.6 % by mass. An estimate of this test
ization established in the Decision on Principles for the
method’spooledlimitofquantitation(PLOQ)is16.0 mg⁄kgas
Development of International Standards, Guides and Recom-
calculated by the procedures in Practice D6259. However,
mendations issued by the World Trade Organization Technical
because instrumentation covered by this test method can vary
Barriers to Trade (TBT) Committee.
in sensitivity, the applicability of the test method at sulfur
concentrations below approximately 20 mg/kg must be deter-
2. Referenced Documents
mined on an individual basis. An estimate of the limit of
2.1 ASTM Standards:
detection is three times the reproducibility standard deviation,
D4057 Practice for Manual Sampling of Petroleum and
and an estimate of the limit of quantitation is ten times the
Petroleum Products
reproducibility standard deviation.
D4175 Terminology Relating to Petroleum Products, Liquid
1.3 Samples containing more than 4.6 % by mass sulfur can
Fuels, and Lubricants
be diluted to bring the sulfur concentration of the diluted
D4177 Practice for Automatic Sampling of Petroleum and
material within the scope of this test method. Samples that are
Petroleum Products
dilutedcanhavehighererrorsthanindicatedinSection17than
D6259 Practice for Determination of a Pooled Limit of
non-diluted samples.
Quantitation for a Test Method
1.4 Volatile samples (such as high vapor pressure gasolines
D6299 Practice for Applying Statistical Quality Assurance
or light hydrocarbons) may not meet the stated precision
and Control Charting Techniques to Evaluate Analytical
because of selective loss of light materials during the analysis.
Measurement System Performance
D7343 Practice for Optimization, Sample Handling,
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 Dec. 1, 2021. Published December 2021. Originally For referenced ASTM standards, visit the ASTM website, www.astm.org, or
ɛ1
approved in 1983. Last previous edition approved in 2016 as D4294 – 16 . DOI: contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
10.1520/D4294-21. Standards volume information, refer to the standard’s Document Summary page on
Analytical Chemistry, Vol 55, 1983, pp. 2210-2218. 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
D4294 − 21
A
TABLE 1 Concentrations of Interfering Species TABLE 2 Matrix Diluents
Element Mass % Tolerated
Matrix Matrix Diluent Alternate Diluent
Phosphorus 0.3
#2 Diesel #2 Diesel Kerosine
Zinc 0.6
Naphtha Kerosine —
Barium 0.8
Kerosine Kerosine #2 Diesel
A
Lead 0.9
Residuals Lube Oil MOWH
B
Calcium 1
Lubricating Base Oils Lube Oil MOWL
B
Chlorine 3
Hydraulic Oils Lube Oil MOWL
A
Ethanol (Note 11) 8.6
Crude Oil Lube Oil MOWH
Methanol (Note 11) 6
Jet Fuels Kerosine —
Fatty Acid Methyl Ester (FAME) 5
Gasoline Gasoline —
A
A
The concentrations of substances in this table were determined by the calcula-
MOWH = mineral oil white heavy
B
tion of the sum of the mass absorption coefficients times mass fraction of each
MOWL = mineral oil white light
element present. This calculation was made for dilutions of representative samples
containing approximately 3 % of interfering substances and 0.5 % sulfur.
a result, the lines produce spectral peaks that overlap with each
other. Spectral interferences may arise from samples contain-
ing lead alkyls, silicon, phosphorus, calcium, potassium,
Calibration, and Validation of X-ray Fluorescence Spec-
halides, and catalyst particles if present at concentrations
trometry Methods for Elemental Analysis of Petroleum
greater than one tenth of the measured concentration of sulfur,
Products and Lubricants
or more than a few hundred milligrams/kilogram (parts per
E29 Practice for Using Significant Digits in Test Data to
million—mass ppm). Follow the manufacturer’s operating-
Determine Conformance with Specifications
guide to compensate for the interferences.
3. Terminology
6.2 Matrix effects are caused by concentration variations of
3.1 For definitions of terms used in this test method, refer to
the elements in a sample. These variations directly influence
Terminology D4175.
X-ray absorption and change the measured intensity of each
element. For example, performance enhancing additives, such
4. Summary of Test Method
as oxygenates in gasoline, may affect the apparent sulfur
4.1 The sample is placed in the beam emitted from an X-ray
reading. Other matrix related interferences may arise from
tube. The resultant excited characteristic X radiation is heavy metal additives, lead alkyls, and elements such as
measured, and the accumulated count is compared with counts
silicon, phosphorus, calcium, potassium, and the halides,
from previously prepared calibration samples to obtain the especially if present at concentrations greater than one tenth of
sulfur concentration in mass percent or mg/kg, or both. A
the measured concentration of sulfur, or more than a few
minimumofthreegroupsofcalibrationsamplesarerequiredto hundred milligrams/kilogram (parts per million—ppm). These
span the concentration range: 0.0 % to 0.1 % by mass, 0.1 % to
types of interferences are always present in X-ray fluorescence
1.0 % by mass, and 1.0 % to 5.0 % by mass sulfur. (See
analysis and are completely unrelated to spectral interferences.
Practice D7343.)
6.3 The interferences mentioned in 6.1 and 6.2 may be
compensated for in contemporary instruments with the use of
5. Significance and Use
built-in software for spectra deconvolution or overlap correc-
5.1 This test method provides rapid and precise measure-
tion and inter-element correction by multiple regression or by
ment of total sulfur in petroleum and petroleum products with
other mathematical methods.
a minimum of sample preparation. A typical analysis time is
6.4 In general, petroleum materials with compositions that
1 min to 5 min per sample.
vary from oils as specified in 10.1 may be analyzed with
5.2 The quality of many petroleum products is related to the
standards made from base materials that are of the same, or
amount of sulfur present. Knowledge of sulfur concentration is
similar, composition. Thus, a gasoline may be simulated by
necessary for processing purposes. There are also regulations
mixing isooctane and toluene in a ratio that approximates the
promulgated in federal, state, and local agencies that restrict
true aromatic content of the samples to be analyzed. Standards
the amount of sulfur present in some fuels.
made from this simulated gasoline will produce results that are
more accurate than results obtained using white oils. Sugges-
5.3 This test method provides a means of determining
whether the sulfur content of petroleum or a petroleum product tions are given in Table 2.
NOTE 3—In the case of petroleum materials that contain suspended
meets specification or regulatory limits.
water, it is recommended that the water be removed before testing or that
5.4 When this test method is applied to petroleum materials
the sample be thoroughly homogenized and immediately tested. The
with matrices significantly different from the calibration mate- interferenceisgreatestifthewatercreatesalayeroverthetransparentfilm
as it will attenuate the X-ray intensity for sulfur. One such method to
rials specified in 10.1, the cautions and recommendations in
accomplish the removal of water is to centrifuge the sample first under
Section 6 should be observed when interpreting results.
ambient sealed conditions, taking care that the sample integrity is not
compromised.
6. Interferences
7. Apparatus
6.1 Spectral interferences are caused by the closeness of the
X-ray characteristic lines of the elements present in a sample 7.1 Energy-dispersive X-ray Fluorescence Analyzer—
and the limited detector ability to completely resolve them.As Energy dispersive X-ray fluorescence analyzer may be used if
D4294 − 21
its design incorporates, as a minimum, the following features correction monitors. Appropriate drift monitor samples should
and if test results from it are shown to be equivalent on the be permanent materials that are stable with respect to repeated
samples of interest. Required design features include:
exposure to X-rays. Stable liquids like polysulfide oils, glass,
7.1.1 Source of X-ray Excitation, X-ray tube with excitation
or metallic specimens are recommended. Liquids, pressed
energy above 2.5 keV.
powders, and solid materials that degrade with repeated expo-
7.1.2 Removable Sample Cup, equipped with replaceable
sure to X-rays should not be used. Examples of sulfur
X-ray transparent plastic film windows and providing a sample
containing materials that have been found to be suitable
depth of at least 4 mm and a diameter of at least 10 mm.
includearenewableliquidpetroleummaterial,ametalalloy,or
7.1.3 X-ray Detector, with high sensitivity and a resolution
a fused glass disk.The monitor’s counting rate, in combination
value (Full Width at Half Maximum, FWHM) not to exceed
with count time, shall be sufficient to give a relative counting
800 eV at 2.3 keV.
erroroflessthan1 %.Thecountingrateforthemonitorsample
7.1.4 Filters or other means of discriminating between
is determined during calibration (see 10.2.1) and again at the
sulfur Kα radiation and other X-rays of higher energy.
time of analysis (see 13.2). These counting rates are used to
7.1.5 Signal conditioning and data handling electronics that
calculate a drift correction factor (see 16.6).
include the functions of X-ray intensity counting, a minimum
8.3.1 Drift correction is usually implemented automatically
of two energy regions, spectral overlap corrections, and con-
in software, although the calculation can readily be done
version of sulfur X-ray intensity into mass percent sulfur
manually. For X-ray instruments that are highly stable, the
concentration.
magnitude of the drift correction factor may not differ signifi-
7.1.6 The analyzer shall have the sensitivity under opti-
mizedmeasurementconditionstomeasuretheconcentrationof cantly from unity.
sulfur at the 0.05 % level with a demonstrated error due to
8.4 Polysulfide Oil, generally nonyl polysulfides containing
counting statistics with one standard deviation not greater than
a known percentage of sulfur diluted in a hydrocarbon matrix.
0.5 % relative at the 500 mg⁄kg level. This requirement
(Warning—May cause allergic skin reactions. Warning—
pertains to sample measurements of less than 1000 mg/kg.
Solutionspreparedinavolatileorun-stabilizedmatrixmaynot
7.1.7 Display or Printer that reads out in mass percent
be stable several months after preparation.)
sulfur or mg/kg sulfur, or both.
NOTE 6—Polysulfide oils are high molecular weight oils that contain
7.2 Analytical Balance, with an accuracy and resolution of
high concentrations of sulfur, as high as 50 % by weight. They exhibit
0.1 mg and capable of weighing up to 100 g.
excellent physical properties such as low viscosity, low volatility, and
NOTE 4—Operation of analyzers using X-ray tube sources is to be
durableshelflifewhilebeingcompletelymiscibleinwhiteoil.Polysulfide
conducted in accordance with the manufacturer’s safety instructions.
oils are readily available commercially. The sulfur content of the polysul-
fide oil concentrate is determined via mass dilution in sulfur-free white oil
8. Reagents
followed by a direct comparison analysis against NIST reference materi-
als.
8.1 Purity of Reagents—Reagent grade chemicals shall be
used in all tests. Unless otherwise indicated, it is intended that
8.5 Mineral Oil, White (MOW), ACS Reagent Grade con-
all reagents conform to the specifications of the Committee on
taining less than 2 mg/kg sulfur or other suitable base material
Analytical Reagents of theAmerican Chemical Society (ACS)
containing less than 2 mg/kg sulfur. When low level
where such specifications are available. Other grades may be
(<200 mg⁄kg) measurements are anticipated, then the sulfur
used, provided it is first ascertained that the reagent is of
content, if any, of the base material needs to be included in the
sufficiently high purity to permit its use without lessening the
calculation of calibration standard concentration (see 10.1).
accuracy of the determination.
When the sulfur content of the solvent or reagent is not
8.2 Di-n-Butyl Sulfide (DBS), a high-purity standard with a
certified, verify the absence of sulfur. Use the purest available
certified analysis for sulfur content. Use the certified sulfur
grades for chemicals to be used for preparing calibration
content and the material purity when calculating the exact
standards.
concentrations of the calibration standards (see 10.1).
8.6 X-ray Transparent Film—Any film that resists attack by
(Warning—Di-n-butyl sulfide is flammable and toxic.
the sample, is free of sulfur, and is sufficiently X-ray transpar-
Warning—Solutions prepared in a volatile or un-stabilized
ent can be used. Film types can include polyester,
matrix may not be stable several months after preparation.)
NOTE 5—It is essential to know the concentration of sulfur in the
polypropylene, polycarbonate, and polyimide. However,
di-n-butyl sulfide, not only the purity, since impurities may also be sulfur
samples of high aromatic content can dissolve polypropylene,
containing compounds.
polycarbonate, and polyester films.
8.3 Drift Correction Monitor(s) (Optional)—Several differ-
8.7 Helium Purge Gas (optional), Follow manufacturer’s
ent materials have been found to be suitable for use as drift
recommendationsforcorrespondingspecificationswhenuseof
helium purge gas is required.
ACS Reagent Chemicals, Specifications and Procedures for Reagents and
Standard-Grade Reference Materials, American Chemical Society, Washington, 8.8 Counting Gas, for instruments equipped with flow
DC. For suggestions on the testing of reagents not listed by theAmerican Chemical
proportional counters.The purity of the counting gas should be
Society, see Analar Standards for Laboratory Chemicals, BDH Ltd., Poole, Dorset,
in agreement with the specification provided by the instrument
U.K., and the United States Pharmacopeia and National Formulary, U.S. Pharma-
copeial Convention, Inc. (USPC), Rockville, MD. manufacturer.
D4294 − 21
TABLE 3 Composition of Primary Standards
8.9 Sample Cells, compatible with the sample and the
geometry requirements of the spectrometer. Disposable cells Sulfur Content, Mass of Matrix Mass of
mass % Diluent, g Di-n-Butyl Sulfide, g
are preferred over reusable ones for ultra low (<50 mg/kg)
5 48.6 14.4
sulfur levels.
0.1 43.6 0.2
8.10 Calibration Check Samples, portions of one or more
liquid petroleum or product standards of known or certified
sulfur content (including polysulfide oils, di-n-butyl sulfide,
ranges of interest. Take into account any sulfur in the base
thiophenes, etc.) and not used in the generation of the calibra-
materialwhencalculatingtheconcentrationofstandardsbelow
tion curve. The check samples shall be used to determine the
0.02 % by mass (200 mg/kg), as shown in Eq 1. Weigh the
precision and accuracy of the initial calibration (see Section
DBSandmatrixdiluenttotherecommendedmassascloselyas
10).
possible. It is important that the exact mass is known and thus
the exact concentration of the prepared standards can be
8.11 Quality Control (QC) Samples, stable petroleum or
calculated and entered into the instrument for calibration
product samples or solids representative of the samples of
purposes. The concentration of sulfur can be calculated using
interest that are run on a regular basis to verify that the system
the following equation:
is in statistical control (see Section 16).
NOTE 7—Verification of system control through the use of QC samples
S 5 DBS 3 S 1 MOW 3 S / DBS1MOW (1)
@~ ! ~ !# ~ !
DBS MOW
and control charting is highly recommended. It is recognized that QC
procedures are the province of the individual laboratory. where:
NOTE 8—Suitable QC samples can often be prepared by combining
S = mass % sulfur of the prepared standards,
retains of typical samples if they are stable. For monitors, solid materials
DBS = actual mass of DBS, g,
are recommended. QC samples must be stable over long periods.
S = the mass % sulfur in DBS, typically 21.91 %,
DBS
MOW = actual mass of white oil, g, and
9. Sample Cell Preparation
S = mass % sulfur in the white oil.
MOW
9.1 If you employ reusable cups, clean and dry cells before
For any generic source of sulfur use the following equation:
use. Disposable sample cups are not to be reused. Window
S 5 @~M 3 S !1~M 3 S !#/~M 1M ! (2)
materialusuallyis<10µmpolyesterorpolycarbonatefilm(see
SC SC D D SC D
8.6). Polycarbonate is preferred due to its high transmissivity
where:
of sulfur X-rays. Renewal of the window of the sample cup is
S = mass % of sulfur in standard,
essential for the measurement of each sample. Avoid touching
M = mass of sulfur compound, g,
SC
the inside of the sample cup or portion of the window film in
S = mass % of sulfur in sulfur compound,
SC
the cup or in the instrument window that is exposed to X-rays.
M = mass of diluent, g, and
D
Oil from fingerprints can affect the reading when analyzing for
S = mass % of sulfur in diluent.
D
low levels of sulfur.Wrinkles in the film will affect the number
10.1.1 Calibration standards can also be prepared by careful
of sulfur X-rays transmitted. Therefore, the importance of the
mixing of certified reference materials (CRM) of the same
film’s smoothness and cleanliness cannot be over stressed to
matrix, so long as the sulfur values of the resulting blends and
ensure reliable results. The analyzer will need recalibration if
their uncertainties are characterized by the certifying body.
the type or thickness of the window film is changed.
10.1.2 Alternatively, standards may be prepared by mass
9.2 Impurities which may affect the measurement of low
serial dilution of polysulfide oils (Note 6) with sulfur-free
levels of sulfur have been found in polyester films and may
white oil. A freshly prepared calibration curve should be
vary from lot to lot. Therefore, if using a polyester film, the
verified using CRMs traceable to a national measurement
calibration should be checked after starting each new roll.
institution that has demonstrated proficiency for measuring
sulfur in the matrix of interest.
9.3 Samples of high aromatic content may dissolve
polyester, polypropylene, and polycarbonate films. In these
NOTE 9—Commercially available standards may be used provided their
cases, other materials besides these films may be used for
sulfur concentrations are accurately known and they approximate the
X-ray windows, provided that they do not contain any elemen-
nominal concentrations listed in Table 3.
tal impurities. An optional window material is 6 µm thick
10.1.3 Accurately weigh the appropriate quantity of matrix
polyimide foil. While polyimide foil absorbs sulfur X-rays
diluent, shown in Table 3, into a suitable, narrow-necked
more than other films, it may be a preferred window material
container and then accurately weigh in the appropriate quantity
asitismuchmoreresistanttochemicalattackbyaromaticsand
of completely pure di-n-butyl sulfide. Mix thoroughly (a
exhibits higher mechanical strength.
polytetrafluoroethylene (PTFE)-coated magnetic stirrer is ad-
visable) at
...

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.
´1
Designation: D4294 − 16 D4294 − 21
Standard Test Method for
Sulfur in Petroleum and Petroleum Products by Energy
Dispersive X-ray Fluorescence Spectrometry
This standard is issued under the fixed designation D4294; 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.
ε NOTE—The overall layout of the Appendix sections was editorially corrected in February 2016.
1. Scope*
1.1 This test method covers the determination of total sulfur in petroleum and petroleum products that are single-phase and either
liquid at ambient conditions, liquefiable with moderate heat, or soluble in hydrocarbon solvents. These materials can include diesel
fuel, jet fuel, kerosine, other distillate oil, naphtha, residual oil, lubricating base oil, hydraulic oil, crude oil, unleaded gasoline,
gasoline-ethanol blends, biodiesel (see Note 2), and similar petroleum products.
NOTE 1—Oxygenated fuels with ethanol or methanol contents exceeding the limits given in Table 1 can be dealt with using this test method, but the
precision and bias statements do not apply (see Appendix X3).
NOTE 2—For samples with high oxygen contents (>3 weight %)(>3 % by weight) sample dilution as described in 1.3 or matrix matching must be
performed to assure accurate results.
1.2 Interlaboratory studies on precision revealed the scope to be 17 mg ⁄kg to 4.6 mass %. 4.6 % by mass. An estimate of this test
method’s pooled limit of quantitation (PLOQ) is 16.0 mg ⁄kg as calculated by the procedures in Practice D6259. However, because
instrumentation covered by this test method can vary in sensitivity, the applicability of the test method at sulfur concentrations
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 Jan. 1, 2016Dec. 1, 2021. Published February 2016December 2021. Originally approved in 1983. Last previous edition approved in 20102016
ɛ1
as D4294 – 10.D4294 – 16 . DOI: 10.1520/D4294-16E01.10.1520/D4294-21.
A
TABLE 1 Concentrations of Interfering Species
Element Mass % Tolerated
Phosphorus 0.3
Zinc 0.6
Barium 0.8
Lead 0.9
Calcium 1
Chlorine 3
Ethanol (Note 11) 8.6
Methanol (Note 11) 6
Fatty Acid Methyl Ester (FAME) 5
A
The concentrations of substances in this table were determined by the calcula-
tion of the sum of the mass absorption coefficients times mass fraction of each
element present. This calculation was made for dilutions of representative samples
containing approximately 3 % of interfering substances and 0.5 % sulfur.
*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
D4294 − 21
below approximately 20 mg/kg must be determined on an individual basis. An estimate of the limit of detection is three times the
reproducibility standard deviation, and an estimate of the limit of quantitation is ten times the reproducibility standard deviation.
1.3 Samples containing more than 4.6 mass % 4.6 % by mass sulfur can be diluted to bring the sulfur concentration of the diluted
material within the scope of this test method. Samples that are diluted can have higher errors than indicated in Section 1617 than
non-diluted samples.
1.4 Volatile samples (such as high vapor pressure gasolines or light hydrocarbons) may not meet the stated precision because of
selective loss of light materials during the analysis.
1.5 A fundamental assumption in this test method is that the standard and sample matrices are well matched, or that the matrix
differences are accounted for (see 5.26.2). Matrix mismatch can be caused by C/H ratio differences between samples and standards
(see Section 56) or by the presence of other heteroatoms.
1.6 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.7 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.
1.8 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:
D4057 Practice for Manual Sampling of Petroleum and Petroleum Products
D4175 Terminology Relating to Petroleum Products, Liquid Fuels, and Lubricants
D4177 Practice for Automatic Sampling of Petroleum and Petroleum Products
D6259 Practice for Determination of a Pooled Limit of Quantitation for a Test Method
D6299 Practice for Applying Statistical Quality Assurance and Control Charting Techniques to Evaluate Analytical Measure-
ment System Performance
D7343 Practice for Optimization, Sample Handling, Calibration, and Validation of X-ray Fluorescence Spectrometry Methods
for Elemental Analysis of Petroleum Products and Lubricants
E29 Practice for Using Significant Digits in Test Data to Determine Conformance with Specifications
3. Terminology
3.1 For definitions of terms used in this test method, refer to Terminology D4175.
4. Summary of Test Method
4.1 The sample is placed in the beam emitted from an X-ray tube. The resultant excited characteristic X radiation is measured,
and the accumulated count is compared with counts from previously prepared calibration samples to obtain the sulfur concentration
in mass percent or mg/kg, or both. A minimum of three groups of calibration samples are required to span the concentration range:
0.0 mass % to 0.1 mass %, 0.1 mass % to 1.0 mass %, and 1.0 mass % to 5.0 mass % 0.0 % to 0.1 % by mass, 0.1 % to 1.0 % by
mass, and 1.0 % to 5.0 % by mass sulfur. (See Practice D7343.)
5. Significance and Use
5.1 This test method provides rapid and precise measurement of total sulfur in petroleum and petroleum products with a minimum
of sample preparation. A typical analysis time is 1 min to 5 min per sample.
Analytical Chemistry, Vol 55, 1983, pp. 2210-2218.
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.
D4294 − 21
TABLE 2 Matrix Diluents
Matrix Matrix Diluent Alternate Diluent
#2 Diesel #2 Diesel Kerosine
Naphtha Kerosine —
Kerosine Kerosine #2 Diesel
A
Residuals Lube Oil MOWH
B
Lubricating Base Oils Lube Oil MOWL
B
Hydraulic Oils Lube Oil MOWL
A
Crude Oil Lube Oil MOWH
Jet Fuels Kerosine —
Gasoline Gasoline —
A
MOWH = mineral oil white heavy
B
MOWL = mineral oil white light
5.2 The quality of many petroleum products is related to the amount of sulfur present. Knowledge of sulfur concentration is
necessary for processing purposes. There are also regulations promulgated in federal, state, and local agencies that restrict the
amount of sulfur present in some fuels.
5.3 This test method provides a means of determining whether the sulfur content of petroleum or a petroleum product meets
specification or regulatory limits.
5.4 When this test method is applied to petroleum materials with matrices significantly different from the calibration materials
specified in 9.110.1, the cautions and recommendations in Section 56 should be observed when interpreting results.
6. Interferences
6.1 Spectral interferences are caused by the closeness of the X-ray characteristic lines of the elements present in a sample and the
limited detector ability to completely resolve them. As a result, the lines produce spectral peaks that overlap with each other.
Spectral interferences may arise from samples containing lead alkyls, silicon, phosphorus, calcium, potassium, halides, and catalyst
particles if present at concentrations greater than one tenth of the measured concentration of sulfur, or more than a few hundred
milligrams/kilogram (parts per million—mass ppm). Follow the manufacturer’s operating-guide to compensate for the
interferences.
6.2 Matrix effects are caused by concentration variations of the elements in a sample. These variations directly influence X-ray
absorption and change the measured intensity of each element. For example, performance enhancing additives, such as oxygenates
in gasoline, may affect the apparent sulfur reading. Other matrix related interferences may arise from heavy metal additives, lead
alkyls, and elements such as silicon, phosphorus, calcium, potassium, and the halides, especially if present at concentrations greater
than one tenth of the measured concentration of sulfur, or more than a few hundred milligrams/kilogram (parts per million—ppm).
These types of interferences are always present in X-ray fluorescence analysis and are completely unrelated to spectral
interferences.
6.3 The interferences mentioned in 5.16.1 and 5.26.2 may be compensated for in contemporary instruments with the use of built-in
software for spectra deconvolution or overlap correction and inter-element correction by multiple regression or by other
mathematical methods.
6.4 In general, petroleum materials with compositions that vary from oils as specified in 9.110.1 may be analyzed with standards
made from base materials that are of the same, or similar, composition. Thus, a gasoline may be simulated by mixing isooctane
and toluene in a ratio that approximates the true aromatic content of the samples to be analyzed. Standards made from this
simulated gasoline will produce results that are more accurate than results obtained using white oils. Suggestions are given in Table
2.
NOTE 3—In the case of petroleum materials that contain suspended water, it is recommended that the water be removed before testing or that the sample
be thoroughly homogenized and immediately tested. The interference is greatest if the water creates a layer over the transparent film as it will attenuate
the X-ray intensity for sulfur. One such method to accomplish the removal of water is to centrifuge the sample first under ambient sealed conditions, taking
care that the sample integrity is not compromised.
D4294 − 21
7. Apparatus
7.1 Energy-dispersive X-ray Fluorescence Analyzer—Energy dispersive X-ray fluorescence analyzer may be used if its design
incorporates, as a minimum, the following features and if test results from it are shown to be equivalent on the samples of interest.
Required design features include:
7.1.1 Source of X-ray Excitation , Excitation, X-ray tube with excitation energy above 2.5 keV.
7.1.2 Removable Sample Cup, equipped with replaceable X-ray transparent plastic film windows and providing a sample depth
of at least 4 mm and a diameter of at least 10 mm.
7.1.3 X-ray Detector, with high sensitivity and a resolution value (Full Width at Half Maximum, FWHM) not to exceed 800 eV
at 2.3 keV.
7.1.4 Filters or other means of discriminating between sulfur Kα radiation and other X-rays of higher energy.
7.1.5 Signal conditioning and data handling electronics that include the functions of X-ray intensity counting, a minimum of two
energy regions, spectral overlap corrections, and conversion of sulfur X-ray intensity into mass percent sulfur concentration.
7.1.6 The analyzer shall have the sensitivity under optimized measurement conditions to measure the concentration of sulfur at
the 0.05 % level with a demonstrated error due to counting statistics with one standard deviation not greater than 0.5 % relative
at the 500 mg ⁄kg level. This requirement pertains to sample measurements of less than 1000 mg/kg.
7.1.7 Display or Printer that reads out in mass percent sulfur or mg/kg sulfur, or both.
7.2 Analytical Balance, with an accuracy and resolution of 0.1 mg and capable of weighing up to 100 g.
NOTE 4—Operation of analyzers using X-ray tube sources is to be conducted in accordance with the manufacturer’s safety instructions.
8. Reagents
8.1 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 (ACS) 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.
8.2 Di-n-Butyl Sulfide (DBS), a high-purity standard with a certified analysis for sulfur content. Use the certified sulfur content
and the material purity when calculating the exact concentrations of the calibration standards (see 9.110.1). (Warning—Di-n-butyl
sulfide is flammable and toxic. Warning—Solutions prepared in a volatile or un-stabilized matrix may not be stable several months
after preparationDi-.)n-butyl sulfide is flammable and toxic.)
NOTE 5—It is essential to know the concentration of sulfur in the di-n-butyl sulfide, not only the purity, since impurities may also be sulfur containing
compounds.
8.3 Drift Correction Monitor(s) (Optional)—Several different materials have been found to be suitable for use as drift correction
monitors. Appropriate drift monitor samples should be permanent materials that are stable with respect to repeated exposure to
X-rays. Stable liquids like polysulfide oils, glass, or metallic specimens are recommended. Liquids, pressed powders, and solid
materials that degrade with repeated exposure to X-rays should not be used. Examples of sulfur containing materials that have been
found to be suitable include a renewable liquid petroleum material, a metal alloy, or a fused glass disk. The monitor’s counting
rate, in combination with count time, shall be sufficient to give a relative counting error of less than 1 %. The counting rate for
the monitor sample is determined during calibration (see 9.2.110.2.1) and again at the time of analysis (see 12.213.2). These
counting rates are used to calculate a drift correction factor (see 15.616.6).
Reagent Chemicals, American Chemical Society SpecificationsACS 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.
D4294 − 21
8.3.1 Drift correction is usually implemented automatically in software, although the calculation can readily be done manually.
For X-ray instruments that are highly stable, the magnitude of the drift correction factor may not differ significantly from unity.
8.4 Polysulfide Oil, generally nonyl polysulfides containing a known percentage of sulfur diluted in a hydrocarbon matrix.
(Warning—May cause allergic skin reactions. Warning—Solutions prepared in a volatile or un-stabilized matrix may not be
stable several months after preparation.May cause allergic skin reactions.))
NOTE 6—Polysulfide oils are high molecular weight oils that contain high concentrations of sulfur, as high as 50 weight %.50 % by weight. They exhibit
excellent physical properties such as low viscosity, low volatility, and durable shelf life while being completely miscible in white oil. Polysulfide oils are
readily available commercially. The sulfur content of the polysulfide oil concentrate is determined via mass dilution in sulfur-free white oil followed by
a direct comparison analysis against NIST reference materials.
8.5 Mineral Oil, White (MOW), ACS Reagent Grade containing less than 2 mg/kg sulfur or other suitable base material containing
less than 2 mg/kg sulfur. When low level (<200(<200 mg mg/kg) ⁄kg) measurements are anticipated, then the sulfur content, if any,
of the base material needs to be included in the calculation of calibration standard concentration (see 9.110.1). When the sulfur
content of the solvent or reagent is not certified, verify the absence of sulfur. Use the purest available grades for chemicals to be
used for preparing calibration standards.
8.6 X-ray Transparent Film—Any film that resists attack by the sample, is free of sulfur, and is sufficiently X-ray transparent can
be used. Film types can include polyester, polypropylene, polycarbonate, and polyimide. However, samples of high aromatic
content can dissolve polypropylene, polycarbonate, and polyester films.
8.7 Helium Purge Gas (optional) , (optional), Follow manufacturer’s recommendations for corresponding specifications when use
of helium purge gas is required.
8.8 Counting Gas, for instruments equipped with flow proportional counters. The purity of the counting gas should be in
agreement with the specification provided by the instrument manufacturer.
8.9 Sample Cells, compatible with the sample and the geometry requirements of the spectrometer. Disposable cells are preferred
over reusable ones for ultra low (<50 mg/kg) sulfur levels.
8.10 Calibration Check Samples, portions of one or more liquid petroleum or product standards of known or certified sulfur
content (including polysulfide oils, di-n-butyl sulfide, thiophenes, etc.) and not used in the generation of the calibration curve. The
check samples shall be used to determine the precision and accuracy of the initial calibration (see Section 910).
8.11 Quality Control (QC) Samples, stable petroleum or product samples or solids representative of the samples of interest that
are run on a regular basis to verify that the system is in statistical control (see Section 1516).
NOTE 7—Verification of system control through the use of QC samples and control charting is highly recommended. It is recognized that QC procedures
are the province of the individual laboratory.
NOTE 8—Suitable QC samples can often be prepared by combining retains of typical samples if they are stable. For monitors, solid materials are
recommended. QC samples must be stable over long periods.
9. Sample Cell Preparation
9.1 If you employ reusable cups, clean and dry cells before use. Disposable sample cups are not to be reused. Window material
usually is <10 μm polyester or polycarbonate film (see 7.68.6). Polycarbonate is preferred due to its high transmissivity of sulfur
X-rays. Renewal of the window of the sample cup is essential for the measurement of each sample. Avoid touching the inside of
the sample cup or portion of the window film in the cup or in the instrument window that is exposed to X-rays. Oil from fingerprints
can affect the reading when analyzing for low levels of sulfur. Wrinkles in the film will affect the number of sulfur X-rays
transmitted. Therefore, the importance of the film’s smoothness and cleanliness cannot be over stressed to ensure reliable results.
The analyzer will need recalibration if the type or thickness of the window film is changed.
9.2 Impurities which may affect the measurement of low levels of sulfur have been found in polyester films and may vary from
lot to lot. Therefore, if using a polyester film, the calibration should be checked after starting each new roll.
D4294 − 21
TABLE 3 Composition of Primary Standards
Sulfur Content, Mass of Matrix Mass of
mass % Diluent, g Di-n-Butyl Sulfide, g
5 48.6 14.4
0.1 43.6 0.2
9.3 Samples of high aromatic content may dissolve polyester, polypropylene, and polycarbonate films. In these cases, other
materials besides these films may be used for X-ray windows, provided that they do not contain any elemental impurities. An
optional window material is 6 μm thick polyimide foil. While polyimide foil absorbs sulfur X-rays more than other films, it may
be a preferred window material as it is much more resistant to chemical attack by aromatics and exhibits higher mechanical
strength.
10. Calibration
10.1 Prepare Calibration Standards by careful mass dilution of the certified di-n-butyl sulfide with a sulfur-free white oil or other
suitable base material (see 7.58.5). The concentrations of the unknown samples must lie within the calibration range that is used.
Approximate recommended nominal sulfur concentration standards are listed in Table 3 for the sulfur concentration ranges of
interest. Take into account any sulfur in the base material when calculating the concentration of standards below 0.02 mass %
0.02 % by mass (200 mg/kg), as shown in Eq 1. Weigh the DBS and matrix diluent to the recommended mass as closely as possible.
It is important that the exact mass is known and thus the exact concentration of the prepared standards can be calculated and
entered into the instrument for calibration purposes. The concentration of sulfur can be calculated using the following equation:
S 5 DBS 3S 1 MOW 3S / DBS1MOW (1)
@~ ! ~ !# ~ !
DBS MOW
where:
S = mass % sulfur of the prepared standards,
DBS = actual mass of DBS, g,
S = the mass % sulfur in DBS, typically 21.91 %,
DBS
MOW = actual mass of white oil, g, and
S = mass % sulfur in the white oil.
MOW
For any generic source of sulfur use the following equation:
S 5 M 3S 1 M 3S / M 1M (2)
@~ ! ~ !# ~ !
SC SC D D SC D
where:
S = mass % of sulfur in standard,
M = mass of sulfur compound, g,
SC
S = mass % of sulfur in sulfur compound,
SC
M = mass of diluent, g, and
D
S = mass % of sulfur in diluent.
D
10.1.1 Calibration standards can also be prepared by careful mixing of certified reference materials (CRM) of the same matrix,
so long as the sulfur values of the resulting blends and their uncertainties are characterized by the certifying body.
10.1.2 Alternatively, standards may be prepared by mass serial dilution of polysulfide oils (Note 56) with sulfur-free white oil. A
freshly prepared polysulfide oil calibration curve should be verified using CRMs traceable to NIST, or other national metrology
institutea national measurement institution that has demonstrated proficiency for measuring sulfur in the matrix of interest. Once
a polysulfide oil calibration curve is established, the calibration standards are stored at room temperature, out of direct sunlight,
and in amber glass bottles. Polysulfide oil standards can be prepared over a wide concentration range from low mg/kg to high
mass % levels of sulfur. They are easily prepared in quantity and make excellent quality control standards. Shaking polysulfide oil
standards before fresh aliquots are taken is recommended to ensure the standard is uniformly blended. The high molecular weight
of these sulfur compounds results in a very low vapor pressure that inh
...