ASTM D6445-99(2004)e1
(Test Method)Standard Test Method for Sulfur in Gasoline by Energy-Dispersive X-ray Fluorescence Spectrometry (Withdrawn 2009)
Standard Test Method for Sulfur in Gasoline by Energy-Dispersive X-ray Fluorescence Spectrometry (Withdrawn 2009)
SIGNIFICANCE AND USE
This test method provides a means of quantifying sulfur content in gasoline. It can be referenced in specification documents as a means to determine if the material meets the desired sulfur content. It is a rapid and precise measurement of total sulfur in petroleum products with a minimum of sample preparation.
The quality of gasoline 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 gasoline as it affects performance characteristics and potential corrosion problems and emission levels. During combustion, the sulfur content in fuel affects SOx emissions, which degrade air quality. Certain jurisdictions may restrict the amount of sulfur in gasoline to prevent or limit pollution to the environment.
SCOPE
1.1 This test method covers the measurement of sulfur in nonleaded gasoline and gasoline-oxygenate blends. The applicable concentration range is 48 to 1000 mg/kg sulfur.
1.2 The values stated in SI units are to be regarded as the standard. The preferred concentration units are mg/kg sulfur.
1.3 This standard may involve hazardous materials, operations, and equipment. 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 precautionary statements, see Sections 5 and 7.
WITHDRAWN RATIONALE
This test method covers the measurement of sulfur in nonleaded gasoline and gasoline-oxygenate blends. The applicable concentration range is 48 to 1000 mg/kg sulfur.
Formerly under the jurisdiction of Committee D02 on Petroleum Products and Lubricants, this test method was withdrawn without replacement in October 2009, because Test Method D4294 has a better precision using the same technology.
General Information
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Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
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Designation: D6445 – 99 (Reapproved 2004)
Standard Test Method for
Sulfur in Gasoline by Energy-Dispersive X-ray Fluorescence
Spectrometry
This standard is issued under the fixed designation D6445; 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.
´ NOTE—Warning notes were editorially moved into the standard text in July 2004.
1. Scope sulfur concentration in mg/kg. One group of calibration stan-
dards is required to span the concentration 5 to 1000 mg/kg
1.1 This test method covers the measurement of sulfur in
sulfur.
nonleaded gasoline and gasoline-oxygenate blends. The appli-
cable concentration range is 48 to 1000 mg/kg sulfur.
4. Significance and Use
1.2 The values stated in SI units are to be regarded as the
4.1 This test method provides a means of quantifying sulfur
standard. The preferred concentration units are mg/kg sulfur.
content in gasoline. It can be referenced in specification
1.3 This standard may involve hazardous materials, opera-
documents as a means to determine if the material meets the
tions, and equipment. This standard does not purport to
desired sulfur content. It is a rapid and precise measurement of
address all of the safety concerns, if any, associated with its
total sulfur in petroleum products with a minimum of sample
use. It is the responsibility of the user of this standard to
preparation.
establish appropriate safety and health practices and deter-
4.2 The quality of gasoline is related to the amount of sulfur
mine the applicability of regulatory limitations prior to use.
present. Knowledge of sulfur concentration is necessary for
For specific warning statements, see Sections 5 and 7.
processing purposes.There are also regulations promulgated in
2. Referenced Documents federal, state, and local agencies that restrict the amount of
sulfur present in gasoline as it affects performance character-
2.1 ASTM Standards:
istics and potential corrosion problems and emission levels.
D3120 Test Method for Trace Quantities of Sulfur in Light
During combustion, the sulfur content in fuel affects SO
x
Liquid Petroleum Hydrocarbons by Oxidative Microcou-
emissions, which degrade air quality. Certain jurisdictions may
lometry
restrict the amount of sulfur in gasoline to prevent or limit
D4057 Practice for Manual Sampling of Petroleum and
pollution to the environment.
Petroleum Products
D4177 Practice for Automatic Sampling of Petroleum and
5. Apparatus
Petroleum Products
5.1 Energy-dispersive X-ray Fluorescence Analyzer—The
3. Summary of Test Method analyzer needs to have sufficient sensitivity to measure the
concentration of sulfur at 500 mg/kg with a one standard
3.1 The sample is placed in the beam emitted from an X-ray
deviation value due to counting statistics no greater than 10
source. The resultant excited characteristic X radiation is
mg/kg under optimized conditions. Any energy dispersive
measured, and the accumulated count is compared with counts
X-ray fluorescence analyzer may be used if its design incor-
from previously prepared calibration standards to obtain the
porates, as a minimum, the following features:
5.1.1 Source of X-ray Excitation—X-ray tube with energy
This test method is under the jurisdiction of ASTM Committee D02 on
above 2.5 keV.
Petroleum Products and Lubricants and is the direct responsibility of Subcommittee
D02.03 on Elemental Analysis.
NOTE 1—Operation of analyzers using X-ray tubes is to be conducted
CurrenteditionapprovedMay1,2004.PublishedJuly2004.Originallyapproved
in accordance with the manufacturer’s safety instructions and federal state
in 1999. Last previous edition approved in 1999 as D6445–99. DOI: 10.1520/
and local regulations.
D6445-99R04E01.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or 5.1.2 Sample Cell, providing a sample depth of at least 4
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
mm and equipped with replaceable X-ray transparent film
Standards volume information, refer to the standard’s Document Summary page on
window.
the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
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D6445 – 99 (2004)
5.1.3 X-ray Detector, with a resolution value not to exceed certified sulfur content when calculating the exact concentra-
800 eV at 2.3 keV. A gas filled proportional counter has been tions of the calibration standards (see 10.1).
found suitable to use.
7.3 Thiophene, sulfur content 37.72 mass %, 99 % purity.
5.1.4 Filters, or other means of discriminating between
7.4 2-Methylthiophene, 32.00 % sulfur, 98 % purity.
sulfur K radiation and other X rays.
a
NOTE 2—Purity on the label for di-n-butyl sulfide, thiophene, and
5.1.5 Signal conditioning and data handling electronics that
2-methylthiophene is only a nominal value. It is essential to know the
include the functions of X-ray intensity counting, spectral
concentration of sulfur in the sulfur standard, not the purity, since
overlap corrections, and conversion of sulfur X-ray intensity
impurities may also be sulfur containing compounds.
into mg/kg sulfur concentration. It is also imperative that the
7.5 Isooctane (2,2,4–trimethylpentane), with a certified
instrument has the capability to monitor counts for at least one
analysis for sulfur content or checked by Test Method D3120
energy region distinct from the sulfur region to allow compen-
or equivalent test method as containing less than 3 mg/kg
sation for variations in spectral background (that is, calculation
sulfur.
of net intensities).
7.6 Toluene, with a certified analysis for sulfur content or
5.1.6 Display or Printer, that reads or prints out in mg/kg or
checked by Test Method D3120 or equivalent test method as
mass percent sulfur.
containing less than 3 mg/kg sulfur.
7.7 X-ray Transparent Film—Any film that resists attack by
6. Matrix Effects
the sample, is free of sulfur, and is sufficiently X-ray transpar-
6.1 Matrix effects refer to changes in measured intensity of
ent may be used. Films found to be suitable are polyester,
sulfur caused by concentration variations of the elements in a
polypropylene, polycarbonate, and polyimide films. Typical
sample. These variations directly influence X-ray absorption
film thicknesses range from 1.5 to 8 µm. Film thickness will
and change the measured intensity of each element. For
affect the transmission of X rays and the films resistance to
example,performanceenhancingadditives,suchasoxygenates
chemical attack.
in gasoline, can affect the apparent sulfur reading. These types
7.7.1 Samples of high aromatic content may dissolve poly-
of interferences are always present in X-ray fluorescence
ester and polycarbonate films. In these cases, other materials
analysis and are completely unrelated to spectral interferences.
besides these films may be used for X-ray windows, provided
6.2 Many modern instruments have the capability to correct
that they do not contain any elemental impurities.An optional
for matrix effects by ratioing measured sulfur intensities to that
window material is polyimide film. While polyimide film
of X-ray radiation scattered from the sample (for example,
absorbs sulfur X rays more than other films, it may be a
scattered X-ray tube lines).This can be an effective method for
preferred window material as it is much more resistant to
compensating for matrix differences between samples and
chemical attack by aromatics and exhibits higher mechanical
standards, although it can result in some degradation of the
strength.
measurement precision. It is the user’s responsibility, however,
7.8 Sample Cells, resistant to sample attack and meeting
to ensure that the matrix corrections applied are accurate. It is
geometry requirements of spectrometer. Disposable cells are
recommended that these are checked by analyzing standard
preferred.
reference materials and that the software corrections offered by
the manufacturer not be accepted at face value. In addition,
8. Sampling and Specimen Preparation
corrections should be verified for new formulations.
8.1 Take samples in accordance with the instructions in
7. Reagents and Materials
Practice D4057 or D4177 where appropriate. Thoroughly mix
7.1 Purity of Reagents—Reagent grade chemicals shall be
and analyze samples immediately after pouring into a sample
used in all tests. Unless otherwise indicated, it is intended that
cell. Inspect the sample for any air bubbles or sediment.Allow
all reagents conform to the specifications of the Committee on
air bubbles to escape or resample if necessary.
Analytical Reagents of the American Chemical Society where
3 NOTE 3—The measured sulfur concentration may vary with the time
such specifications are available. Other grades may be used,
that the sample/standard contacts the film covering the sample cell. By
provided it is first ascertained that the reagent is of sufficiently
consistently minimizing the length of time the film comes into contact
high purity to permit its use without lessening the accuracy of
with the sample or standards, possible variations can be reduced.
the determination. The concentration should be known to at
8.2 Ifusingreusablesamplecells,cleananddrycellsbefore
least three significant figures or nearest 1 mg/kg, whichever is
use. Do not reuse disposable sample cells. Replacement of the
higher.
X-ray film of a reused sample cell is essential for the
7.2 Di-n-Butyl Sulfide (DBS),(Warning—Di-n-butyl sul-
measurement of each sample.Avoid touching the inside of the
fide is flammable and toxic.)Ahigh purity standard, minimum
sample cell or portion of the window film in the cell or in the
96 %purity,withacertifiedanalysisforsulfurcontent.Usethe
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 intensity of
Reagent Chemicals, American Chemical Society Specifications, American
Chemical Society, Washington, DC. For Suggestions on the testing of reagents not
sulfur X rays transmitted.Therefore, it is essential that the film
listed by the American Chemical Society, see Annual Standards for Laboratory
be taut and clean to ensure reliable results. The analyzer will
Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia
need recalibration if the type or thickness of the window
and National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,
MD. material is changed.
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D6445 – 99 (2004)
TABLE 2 Composition of Primary Standards When Using
8.3 Impurities or thickness variations, which may affect the
Thiophene/2-Methylthiophene Blend (TM)
measurement of low levels of sulfur, have been found in
Sulfur Mass of Diluent Mass of TM
window materials films and may vary from lot to lot. There-
(mg/kg) (g) (g)
fore, check the calibration after starting each new package of
100 540 0.15
film.
2000 200.8 1.15
9. Preparation of Apparatus
9.1 Set up the apparatus in accordance with the manufac-
prepared standards to the nearest 1 mg/kg. Calculate the
turer’s instructions. Whenever possible the instrument should
concentration of sulfur in the primary standard using the
remain energized to maintain optimum stability.
following equations. Use Eq 1 if using di-n-butyl sulfide and
10. Calibration and Standardization Eq 2 if using the thiophene/2-methylthiophene blend as a
source of sulfur:
10.1 Preparation of Calibration Standards:
10.1.1 Prepare diluent by blending 20 % toluene and 80 % 10,000~DBS3 S 1 Diluent 3 S !
DBS DILUENT
S 5 (1)
isooctane by volume. DBS 1 Diluent
10.1.2 Use either di-n-butyl sulfide or a blend of thiophene/
2-methylthiophene as a source of sulfur in the primary stan-
10,000~TM 3 S 1 Diluent 3 S !
TM DILUENT
S 5 (2)
dards. If using di-n-butyl sulfide as the source of sulfur, TM 1 Diluent
proceed to 10.1.3.
where:
10.1.2.1 To prepare the thiophene/2-methylthiophene (TM)
S = mg/kg sulfur of the primary standards,
blend, mix 9.90 g thiophene with 9.55 g 2-methylthiophene.
DBS = if using the di-n-butyl sulfide, this is the actual
Weighthematerialsintoataredvolumetricflaskandrecordthe
mass in grams of di-n-butyl sulfide used,
mass to four significant digits. Calculate the exact sulfur
TM = ifusingthethiophene/2-methylthiopheneblend,
content of the stock sulfur solution to the nearest mg/kg. Mix
this is the actual mass of the sulfur blend in
thoroughly (a polytetrafluoroethylene (PTFE)-coated magnetic
grams,
stirrer is suitable) at room temperature.
S = if using di-n-butyl sulfide, this is the mass %
DBS
10.1.3 Make primary standards independently at 100 and
sulfur of the di-n-butyl sulfide, typically
2000 mg/kg sulfur and not by serial dilutions from a single
21.91 %. For example, 21.91 % would be ex-
concentrate. Refer to 10.1.3.1 if using di-n-butyl sulfide and
pressed as 21.91 in the formula (see Note 2),
10.1.3.2ifusingthethiophene/2-methylthiopheneblendforthe
S = ifusingthethiophene/2-methylthiopheneblend,
TM
source of sulfur.
this is the mass % sulfur in the this blend,
10.1.3.1 Weigh the diluent and the di-n-butyl sulfide (DBS)
typically 34.9 mass %. For example, 34.9 %
into a tared volumetric flask, using the indicated mass in Table
would be expressed as 34.9 in the formula (see
1 (but record the mass to four significant digits). Mix thor-
Note 2),
oughly (a PTFE-coated magnetic stirrer is suitable) at room
Diluent = actual mass of isooctane/toluene diluent (g),
temperature.
and
10.1.3.2 Weigh the diluent and the thiophene/2-
S = mass % sulfur in the isooctane/toluene blend.
Diluent
methylthiophene (TM) blend into a tared volumetric flask
For example, 0.0001 % would be expressed as
usingtheindicatedmassinTable2(butrecordthemasstofour
0.0001 in the formula.
significant digits). Mix thoroughly (a PTFE-coated magnetic
10.1.4 Prepare calibration standards with the nominal con-
stirrer is advisable) at room temperature.
centration ranges identified in Table 3 for the two ranges by
10.1.3.3 If the isooctane/toluene diluent being used for the
preparation of standards contains sulfur, incorporate this value
into the calculated sulfur content of the prepared standards
TABLE 3 Calibration Standards
(consultyoursupplierforacertifiedsulfurconcentrationortest
Standard Nominal Mass of Primary Mass of Diluent
the isooctane/toluene using Test Method D3120 or any other
Number Concentration Standard (g)
(mg/kg) (g)
equivalent low level sulfur analyzing method).
10.1.3.4 It is important that the actual mass is known and
Use 100 mg/kg primary standard for Stan
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