ASTM D7039-04
(Test Method)Standard Test Method for Sulfur in Gasoline and Diesel Fuel by Monochromatic Wavelength Dispersive X-ray Fluorescence Spectrometry
Standard Test Method for Sulfur in Gasoline and Diesel Fuel by Monochromatic Wavelength Dispersive X-ray Fluorescence Spectrometry
SCOPE
1.1 This test method covers the determination of total sulfur by monochromatic, wavelength-dispersive X-ray fluorescence (MWDXRF) spectrometry in single-phase gasolines, diesel fuels, and refinery process streams used to blend gasoline and diesel, at concentrations from 2 mg/kg to 500 mg/kg. The precision of this test method was determined by an interlaboratory study using representative samples of the liquids described in 1.1 and 1.2. The pooled limit of quantitation (PLOQ) was estimated to be 4 mg/kg.
Note 1—Volatile samples such as high-vapor-pressure gasolines or light hydrocarbons might not meet the stated precision because of the evaporation of light components during the analysis.
1.2 Gasoline samples containing oxygenates may be analyzed with this test method provided the matrix of the calibration standards is either matched to the sample matrices or the matrix correction described in Annex A1 is applied to the results. The conditions for matrix matching and matrix correction are provided in the Interferences section (Section 5).
1.3 Gasolines and diesels with sulfur contents above 500 mg/kg can be analyzed after dilution with appropriate solvent (see 5.2). The precision and bias of sulfur determinations on diluted samples has not been determined and may not be the same as shown for neat samples (Section 15).
1.4 When the elemental composition of the samples differ significantly from the calibration standards used to prepare the calibration curve, the cautions and recommendation in Section 5 should be carefully observed.
1.5 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.
1.6 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 health practices and determine the applicability of regulatory limitations prior to use. For specific hazard information, see 3.1.
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An American National Standard
Designation:D7039–04
Standard Test Method for
Sulfur in Gasoline and Diesel Fuel by Monochromatic
Wavelength Dispersive X-ray Fluorescence Spectrometry
This standard is issued under the fixed designation D 7039; 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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope 2. Referenced Documents
2.1 ASTM Standards:
1.1 This test method covers the determination of total sulfur
by monochromatic, wavelength-dispersive X-ray fluorescence D 4057 Practice for Manual Sampling of Petroleum and
(MWDXRF) spectrometry in single-phase gasolines, diesel Petroleum Products
fuels, and refinery process streams used to blend gasoline and D 4177 Practice for Automatic Sampling of Petroleum and
diesel, at concentrations from 2 mg/kg to 500 mg/kg. The Petroleum Products
precision of this test method was determined by an interlabo- D 6299 Practice for Applying Statistical Quality Assurance
ratory study using representative samples of the liquids de- Techniques to Evaluate Analytical Measurement System
scribedin1.1and1.2.Thepooledlimitofquantitation(PLOQ) Performance
was estimated to be 4 mg/kg. D 6300 Practice for Determination of Precision and Bias
Data for Use in Test Methods for Petroleum Products and
NOTE 1—Volatile samples such as high-vapor-pressure gasolines or
Lubricants
light hydrocarbons might not meet the stated precision because of the
evaporation of light components during the analysis.
3. Summary of Test Method
1.2 Gasoline samples containing oxygenates may be ana-
3.1 A monochromatic X-ray beam with a wavelength suit-
lyzed with this test method provided the matrix of the
able to excite the K-shell electrons of sulfur is focused onto a
calibration standards is either matched to the sample matrices
test specimen contained in a sample cell (see Fig. 1). The
orthematrixcorrectiondescribedinAnnexA1isappliedtothe
fluorescent Ka radiation at 0.5373 nm (5.373 Å) emitted by
results. The conditions for matrix matching and matrix correc-
sulfur is collected by a fixed monochromator (analyzer). The
tion are provided in the Interferences section (Section 5).
intensity (counts per second) of the sulfur X rays is measured
1.3 Gasolines and diesels with sulfur contents above 500
using a suitable detector and converted to the concentration of
mg/kg can be analyzed after dilution with appropriate solvent
sulfur (mg/kg) in a test specimen using a calibration equation.
(see 5.2). The precision and bias of sulfur determinations on
Excitation by monochromatic X rays reduces background,
diluted samples has not been determined and may not be the
simplifies matrix correction, and increases the signal/
same as shown for neat samples (Section 15).
backgroundratiocomparedtopolychromaticexcitationusedin
1.4 When the elemental composition of the samples differ
conventional WDXRF techniques. (Warning—Exposure to
significantly from the calibration standards used to prepare the
excessive quantities of X-ray radiation is injurious to health.
calibration curve, the cautions and recommendation in Section
The operator needs to take appropriate actions to avoid
5 should be carefully observed.
exposing any part of his/her body, not only to primary X rays,
1.5 The values stated in SI units are to be regarded as the
but also to secondary or scattered radiation that might be
standard. The values given in parentheses are for information
present. The X-ray spectrometer should be operated in accor-
only.
dance with the regulations governing the use of ionizing
1.6 This standard does not purport to address all of the
radiation.)
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro-
4. Significance and Use
priate safety and health practices and determine the applica-
4.1 This test method provides for the precise measurement
bility of regulatory limitations prior to use. For specific hazard
ofthetotalsulfurcontentofgasolinesanddieselswithminimal
information, see 3.1.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
This test method is under the jurisdiction of ASTM Committee D02 on Standards volume information, refer to the standard’s Document Summary page on
Petroleum Products and Lubricants and is the direct responsibility of Subcommittee the ASTM website.
D02.03 on Elemental Analysis. Bertin, E. P., Principles and Practices of X-ray Spectrometric Analysis, Plenum
Current edition approved May 1, 2004. Published June 2004. Press, New York, 1975, pp. 115-118.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D7039–04
FIG. 1 Schematic of the MWDXRF Analyzer
sample preparation and analyst involvement. The typical time diluting samples, use a diluent with an elemental composition
for each analysis is two to three minutes. the same or similar to the base material used for preparing the
4.2 Knowledge of the sulfur content of diesel fuels, gaso- calibration standards.
lines, and refinery process streams used to blend gasolines is 5.2.1 A base material for gasoline can be approximately
important for process control as well as the prediction and simulated by mixing 2,2,4-trimethylpentane (isooctane) and
control of operational problems such as unit corrosion and toluene in a ratio that approximates the expected aromatic
catalyst poisoning, and in the blending of products to com- content of the samples to be analyzed.
modity specifications. 5.2.2 Fuels containing oxygenates may be analyzed using
4.3 Various federal, state, and local agencies regulate the calibration standards containing the same amount of the same
sulfur content of some petroleum products, including gasoline oxygenate in the test fuel.
anddieselfuel.Unbiasedandprecisedeterminationofsulfurin
6. Apparatus
these products is critical to compliance with regulatory stan-
dards. 6.1 Monochromatic Wavelength Dispersive X-ray Fluores-
cence (MWDXRF) Spectrometer , equipped for X-ray detec-
5. Interferences
tion at 0.5373 nm (5.373Å).Any spectrometer of this type can
be used if it includes the following features, and the precision
5.1 Differences between the elemental composition of test
and bias of test results are in accordance with the values
samplesandthecalibrationstandardscanresultinbiasedsulfur
described in Section 15.
determinations. For diesels and gasolines within the scope of
6.1.1 X-ray Source, capable of producing X rays to excite
this test method, the only important elements contributing to
sulfur. X-ray tubes with a power >25W capable of producing
bias resulting from differences in the matrices of calibrants and
Rh La,PdLa,AgLa,TiKa,ScKa, and Cr Ka radiation are
test samples are hydrogen, carbon, and oxygen. A matrix-
recommended for this purpose.
correction factor (C) can be used to correct this bias; the
calculation is described in Annex A1. For general analytical 6.1.2 Incident-beam Monochromator, capable of focusing
and selecting a single wavelength of characteristic X rays from
purposes, the matrices of test samples and the calibrants are
consideredtobematchedwhenthecalculatedcorrectionfactor the source onto the specimen.
6.1.3 Optical Path, designed to minimize the absorption
C is within 0.98 to 1.04. No matrix correction is required
within this range. Samples used in the 2002 interlaboratory along the path of the excitation and fluorescent beams using a
vacuum or a helium atmosphere. A vacuum of < 2.7 kPa (<20
study fall within this category. A matrix correction is required
when the value of C is outside the range of 0.98 to 1.04. For Torr) is recommended. The calibration and test measurements
must be done with identical optical paths, including vacuum or
most testing, matrix correction can be avoided with a proper
helium pressure.
choice of calibrants. For example, based on the example graph
6.1.4 Fixed-channel Monochromator, suitable for dispers-
in Annex A1 (Fig. 2), a calibrant with 86 mass % carbon and
ing sulfur Ka X rays.
14mass%hydrogencancovernon-oxygencontainingsamples
with C/H ratios from 5.4 to 8.5. For gasolines with oxygenates,
up to 2.3 mass % oxygen (12 mass % MTBE) can be tolerated
The sole source of this apparatus known to the committee at this time is X-ray
for test samples with the same C/H ratio as the calibrants.
Optical Systems, Inc., 15 Tech Valley Drive, East Greenbush, NY12061. If you are
5.2 To minimize any bias in the results, use calibration
aware of alternative suppliers, please provide this information to ASTM Interna-
standards prepared from sulfur-free base materials of the same
tional Headquarters.Your comments will receive careful consideration at a meeting
or similar elemental composition as the test samples. When of the responsible technical committee, which you may attend.
D7039–04
FIG. 2 Matrix Correction for a Test Sample vs. C/H and Total Oxygen Content Using Chromium Ka for the Excitation Beam
6.1.5 Detector, designed for efficient detection of sulfur Ka such specifications are available. Other grades may be used,
X rays. provided it is first ascertained that the reagent is of sufficiently
6.1.6 Single-Channel Analyzer, an energy discriminator to high purity to permit its use without lessening the accuracy of
monitor only sulfur radiation. the determination.
6.1.7 Removable Sample Cell, an open-ended specimen 7.2 Calibration-Check Samples, for verifying the accuracy
holder compatible with the geometry of the MWDXRF spec- of a calibration. The check samples shall have known sulfur
trometeranddesignedtousereplaceableX-raytransparentfilm content and not be used in determining the calibration curve.A
(see 6.1.8) to hold a liquid specimen with a minimum depth of standard from the same reliable and consistent source of
5mm. The sample cell must not leak when fitted with X-ray calibration standards used to determine the calibration curve is
transparent film. A disposable cell is recommended. convenient to check the calibration.
6.1.8 X-Ray Transparent Film, for containing and support- 7.3 Di-n-butyl Sulfide, a high-purity liquid with a certified
ing the test specimen in the sample cell (see 6.1.7) while sulfur concentration. Use the certified sulfur concentration
providing a low-absorption window for X rays to pass to and when calculating the exact concentrations of sulfur in calibra-
from the sample. Any film resistant to chemical attack by the tion standards.
sample, free of sulfur, and X-ray transparent can be used, for 7.4 Drift-Monitor Sample (Optional), to determine and
example, polyester, polypropylene, polycarbonate, and poly- correct instrument drift over time (see 10.4, 11.1, and 12.1).
imide.However,samplesofhigharomaticcontentcandissolve Various forms of stable sulfur-containing materials are suitable
polyester and polycarbonate films. drift-correction samples, for example, liquid petroleum, solid,
pressed powder, metal alloy, and fused glass. The count rate
7. Reagents and Materials
displayed by the monitor sample, in combination with a
convenient count time (T), shall be sufficient to give a relative
7.1 Purity of Reagents—Reagent grade chemicals shall be
standard deviation (RSD) of<1% (see Appendix X1).
used in all tests. Unless otherwise indicated, it is intended that
all reagents conform to the specifications of the Committee on
NOTE 2—Calibration standards may be used as drift-monitor samples.
Analytical Reagents of the American Chemical Society where
Because it is desirable to discard test specimens after each determination,
Reagent Chemicals, American Chemical Society Specifications, American
Chemical Society, Washington, D.C. 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. Pharmaceutical Convention, Inc. (USPC), Rockville,
MD.
D7039–04
alowercostmaterialissuggestedfordailyuse.Anystablematerialcanbe
manufacturer’s instructions. Allow sufficient time for instru-
used for daily monitoring of drift.
ment electronics to stabilize. Perform any instrument checkout
NOTE 3—The effect of drift correction on the precision and bias of this
procedures required. When possible, the instrument should be
test method has not been studied.
run continuously to maintain optimum stability.
7.4.1 Drift correction can be done automatically if the
9.1.1 Use the count time (T) recommended by the instru-
instrument embodies this option, although the calculation can
ment manufacturer for the lowest sulfur concentration ex-
be readily done by conventional methods of data reduction and
pected. The typical time for each measurement is two to three
processing.
minutes.
7.5 Quality-Control (QC) Samples , for use in establishing
9.1.2 Alternatively, determine T expected for a desired
and monitoring the stability and precision of an analytical
count precision by following the procedure in Appendix X1.
measurement system (see Section 14). Use homogeneous
9.2 Specimen Preparation—Prepare a specimen of a test
materials, similar to samples of interest and available in
sample or a calibration standard as follows:
sufficient quantity to be analyzed regularly for a long period of
9.2.1 Carefully transfer a sufficient portion of the liquid to
time
fill an open-ended sample cell above a minimum depth of 5
mm, beyond which additional liquid does not affect the count
NOTE 4—Verification of system control through the use of QC samples
rate. Filling the sample cell to three-fourths of the cell’s depth
and control charting is highly recommended.
NOTE 5—SuitableQCsamplescanbepreparedbycombiningretainsof
is generally adequate.
typical samples.
9.2.2 Fit an unused piece of X-ray-transparent film over the
sample-cell opening and attach securely. Use the same batch of
7.6 White Oil, use a high purity mineral oil and account for
film for the analysis of test samples and the calibration
its sulfur content when calculating the sulfur concentrations of
standards used for constructing the calibration curve. Avoid
the calibration standards.
touching the inside of the sample cell, any portion of the film
7.7 Helium, minimum purity 99.9 %, for use as an optical
exposed to the liquid or the X-ray beam, and also avoid
path.
touching the instrument window. (It is highly recommended
8. Sampli
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