ASTM D7212-13(2018)

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: D7212 − 13 (Reapproved 2018)
Standard Test Method for
Low Sulfur in Automotive Fuels by Energy-Dispersive X-ray
Fluorescence Spectrometry Using a Low-Background
Proportional Counter
This standard is issued under the fixed designation D7212; 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.
1. Scope D6299 Practice for Applying Statistical Quality Assurance
and Control Charting Techniques to Evaluate Analytical
1.1 This test method specifies an energy-dispersive X-ray
Measurement System Performance
fluorescence (EDXRF) method for the determination of the
D6300 Practice for Determination of Precision and Bias
total sulfur content of automotive fuels with a concentration
Data for Use in Test Methods for Petroleum Products and
range from 7 mg/kg to 50 mg/kg.
Lubricants
1.1.1 The pooled limit of quantitation of this test method as
D6792 Practice for Quality Management Systems in Petro-
obtained by statistical analysis of interlaboratory test results is
leum Products, Liquid Fuels, and Lubricants Testing
7 mg⁄kg sulfur.
Laboratories
1.2 The values stated in SI units are to be regarded as the
D7343 Practice for Optimization, Sample Handling,
standard. The preferred concentration units are mg/kg sulfur.
Calibration, and Validation of X-ray Fluorescence Spec-
1.3 This standard does not purport to address all of the
trometry Methods for Elemental Analysis of Petroleum
safety concerns, if any, associated with its use. It is the
Products and Lubricants
responsibility of the user of this standard to establish appro-
E29 Practice for Using Significant Digits in Test Data to
priate safety, health, and environmental practices and deter-
Determine Conformance with Specifications
mine the applicability of regulatory limitations prior to use.
1.4 This international standard was developed in accor-
3. Terminology
dance with internationally recognized principles on standard-
3.1 Definitions of Terms Specific to This Standard:
ization established in the Decision on Principles for the
3.1.1 low background proportional counter, n—an X-ray
Development of International Standards, Guides and Recom-
proportional counter that can suppress the noise generated
mendations issued by the World Trade Organization Technical
when incident X rays are absorbed near the wall with resulting
Barriers to Trade (TBT) Committee.
incomplete charge collection.
2. Referenced Documents 3.1.1.1 Discussion—An electrode shield close to the wall
detects incomplete charge collection and associated electronic
2.1 ASTM Standards:
detection circuitry rejects those events. In comparison to
D4045 Test Method for Sulfur in Petroleum Products by
conventional proportional counters, this gives lower spectral
Hydrogenolysis and Rateometric Colorimetry
background and a lower limit of detection.
D4057 Practice for Manual Sampling of Petroleum and
Petroleum Products
4. Summary of Test Method
D4177 Practice for Automatic Sampling of Petroleum and
Petroleum Products
4.1 The sample is placed in the beam emitted from an X-ray
source with titanium target and primary filtration so that
excitation is by essentially monochromatic radiation of
This test method is under the jurisdiction of ASTM Committee D02 on
4.51 keV and virtually no background at 2.3 keV. A low
Petroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility of
background proportional counter measures the intensity of the
Subcommittee D02.03 on Elemental Analysis.
fluorescent sulfur K series intensity and argon K series inten-
Current edition approved July 1, 2018. Published August 2018. Originally
sity (from residual air) and the accumulated counts are com-
approved in 2006. Last previous edition approved in 2013 as D7212 – 13. DOI:
10.1520/D7212-13R18.
pared with counts from previously prepared calibration stan-
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
dards to obtain the sulfur concentration in mg/kg. If chlorine is
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
expected to be present in some samples then other regions of
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. the spectrum must be measured to provide compensation for
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D7212 − 13 (2018)
spectral overlap. One group of calibration standards is required 7.1.2 Low Background Proportional Counter (see 3.1.1),
to span the concentration range from 0 mg⁄kg to 150 mg⁄kg with sensitivity at 2.3 keV.
sulfur. 7.1.3 Multi-channel Analyzer, with a channel width of 10eV
NOTE 1—Operation of analyzers using X-ray tubes is to be conducted
or less, covering the energy range from 0 keV to 10 keV.
in accordance with the manufacturer’s safety instructions and federal,
7.1.4 Signal Conditioning and Data Handling Electronics,
state, and local regulations governing the use of ionizing radiation.
that include the functions of X-ray intensity counting, a
4.2 Practice D7343 should be consulted regarding standard
minimum of four energy regions (to correct for background X
operating protocols in XRF analysis.
rays and spectral overlap), spectral overlap corrections, and
conversions of sulfur X-ray intensity into sulfur concentration.
5. Significance and Use
7.1.5 Display or Printer, that reads out in mg/kg sulfur.
7.1.6 Removable Sample Cell, providing a sample depth of
5.1 This test method determines total sulfur in automotive
at least 4 mm and equipped with a replaceable X-ray transpar-
fuels with a typical analysis time around 10 min per sample.
ent plastic film window.
5.2 The quality of automotive fuel is related to the amount
7.1.7 Helium Purged Optical Path, to maximize sensitivity
of sulfur present. Knowledge of sulfur level is necessary for
and minimize spectral overlap from argon in air. The helium
processing purposes.
shall be at least 99.9 % purity.
5.3 Sulfur level in automotive fuels affects performance
8. Reagents and Materials
characteristicsandairquality.Federal,state,andlocalagencies
regulate the level of sulfur in fuel delivered at the pump.
8.1 Purity of Reagents—Reagent grade chemicals shall be
used in all tests. Unless otherwise indicated, it is intended that
5.4 This test method can be referenced in specification
all reagents conform to the specifications of the Committee on
documents to determine if the material meets the desired sulfur
Analytical Reagents of the American Chemical Society where
content.
such specifications are available. Other grades may be used,
5.5 If this test method is applied to petroleum matrices with
provided it is first ascertained that the reagent is of sufficiently
significantly different composition to those used in the inter-
high purity to permit its use without lessening the accuracy of
laboratory precision study, then the caution and recommenda-
the determination.
tions in Section 6 should be observed when interpreting the
8.2 Di-n Butyl Sulfide (DBS), a high purity standard with
results.
certified analysis for sulfur content. Use the certified sulfur
content when calculating the exact concentrations of the
6. Interferences
calibration standards. (Warning—Di-n-butyl sulfide is flam-
6.1 Spectral interferences result when some sample compo-
mable and toxic).
nent element or elements emit X rays that the detector cannot
8.3 MineralOil,White(MOW),withsulfurcontentlessthan
resolvefromsulfurX-rayemission.Overlappingpeaklinesare
0.2 mg⁄kgascertifiedbyasuitableanalyticalmethod,likeTest
theresultofthis.Thisoverlappingeffectmaybebyleadalkyls,
Method D4045.
silicon, phosphorus, calcium, potassium, and halides if their
aggregate concentration is more than 10 mg⁄kg. The most 8.4 X-ray Transparent Film, any film that resists attack by
likely interference is chlorine that has been found in biodiesel the sample, is free of sulfur and other interfering elements (see
derived from recycled waste vegetable oil. 6.1), and is sufficiently X-ray transparent may be used.
6.2 The presence of oxygenates or water may alter the
NOTE 2—Polycarbonate with thickness of 5 or 6 µm most closely
matches these requirements and eight of nine participants in the interlabo-
sensitivity for sulfur.
ratorystudy usedoneofthesefilms,whiletheotherlaboratoryused3 µm
6.3 Follow the manufacturer’s operating guide to compen-
polyester.
sate for the interferences.
8.4.1 Samples of high aromatic content may dissolve poly-
carbonate film and polypropylene has a tendency to absorb
7. Apparatus
some hydrocarbons and may stretch during a long measure-
7.1 Energy-dispersive X-ray Fluorescence Analyzer—Any ment time.
energy dispersive X-ray fluorescence analyzer may be used if
its design incorporates, as a minimum the following features:
The low background proportional counter is covered by a pending patent.
7.1.1 SourceofX-rayExcitation,X-raysourcewithtitanium
Interested parties are invited to submit information regarding the identification of an
target and primary filtration so that excitation is by essentially
alternative(s) to this patent-pending item toASTM International Headquarters.Your
monochromatic radiation of 4.51 keV.
comments will receive careful consideration at a meeting of the responsible
technical committee, which you may attend.
Reagent Chemicals, American Chemical Society Specifications, American
Chemical Society, Washington DC. For suggestions on testing of reagents not listed
The sole source of supply of the apparatus known to the committee at this time by the American Chemical Society, see Annual Standards for Laboratory , BDH
is the Twin-X ULS from Oxford Instruments Analytical, Halifax Road, High Ltd., Poole Dorset, U.K., and the United States Pharmacopeia and National
Wycombe, Bucks, HP12 3SE, England. If you are aware of alternative suppliers, Formulary, U.S Pharmacopeial Convention, Inc. (USPC), Rockville, MD.
please provide this information to ASTM International Headquarters. Your com- Supporting data have been filed at ASTM International Headquarters and may
ments will receive careful consideration at a meeting of the responsible technical beobtainedbyrequestingResearchReportRR:D02-1587.ContactASTMCustomer
committee, which you may attend. Service at service@astm.org.
D7212 − 13 (2018)
NOTE3—Onelaboratoryhasshownthatpolycarbonateresistsamixture
10. Preparation of Apparatus
of 25 % by mass isooctane and 75 % by mass toluene for 80 min.
10.1 Set up the apparatus in accordance with the manufac-
8.4.2 In these cases high purity polyester is acceptable, but
turer’s instructions. Whenever possible, the instrument should
overall, polycarbonate offers the best combination of spectral
remain energized to maintain optimum stability.
purityandresistancetostretching.Othermaterialsmaybeused
10.2 When changing the helium gas cylinder or after a
for X-ray windows, provided that they do not contain any
system has been idle for a day or more ensure that the helium
elemental impurities and match the listed films for X-ray
pipes are purged of air by performing a dummy measurement.
transmission.
11. Calibration and Standardization
8.5 Sample Cells, resistant to sample attack and meet the
geometry requirements of spectrometer.
11.1 Preparation of Calibration Standards:
11.1.1 Preparation of Stock Calibration Standard—
8.6 Calibration Check Samples, portions of one or more
Accurately weigh the nominal quantity of white mineral oil to
automotivefuelstandardsofknownsulfurcontentandnotused
the nearest 0.1 mg, as shown in Table 1, into a suitable
in the generation of the calibration line. The check samples
narrow-necked container, then accurately weigh in the nominal
shallbeusedtodeterminetheaccuracyoftheinitialcalibration
quantity of di-n-butyl sulfide. Mix thoroughly (a PTFE-coated
(see 11.3).
magnetic stirrer is advisable) at room temperature. Calculate
8.7 Quality Control (QC) Samples, preferably portions of the concentration of sulfur in the stock standard to 1 mg⁄kg
using the following equation:
one or more automotive fuel materials that are stable and
representative of the samples of interest.
S 5 @DBS 3S /~DBS1MO!# 310000 (1)
Stock DBS
where:
9. Sampling
S = mg/kg of sulfur in the stock standard,
Stock
9.1 A sample shall be taken in accordance with the instruc-
DBS = actual mass of DBS, g,
tions in Practice D4057 or D4177, where appropriate. Do not
S = the mass % of sulfur in DBS, typically 21.91 %, and
DBS
shake samples, thus avoiding entrained air. Analyze samples
MO = actual mass of white mineral oil, g.
immediately after pouring into a sample cell and allowing the
11.1.2 Preparation of Calibration Standards—Accurately
escape of the air bubbles caused by mixing.
weigh the nominal quantity of white mineral oil to the nearest
9.2 For the measurement of low sulfur contents disposable 0.1 mg, as shown in Table 2, into a suitable narrow-necked
container, then accurately weigh in the nominal quantity of
cells are recommended. Preparation of sample cells must be
done with care and by following any advice from the supplier. stock standard. Mix thoroughly (a PTFE-coated magnetic
stirrer is advisable) at room temperature. Calculate the concen-
Afreshly prepared sample cell including film is required prior
to analyzing the samples. Avoid touching the inside of the tration of sulfur in the each standard to 0.1 mg⁄kg using the
following equation:
sample cell or portion of the window film in the cell or in the
instrument window that is exposed to X rays. Oil from
S 5 STK 3S / STK1MO (2)
~ !
Std Stock
fingerprints affects the reading when analyzing for low level of
where:
sulfur. Ensure that the film is not scratched, especially by the
S = mg/kg of sulfur in the calibration standard, and
tear-off bar as it is withdrawn from the container. Wrinkles in
Std
STK = actual mass of stock standard, g.
the film will affect the intensity of sulfur X rays transmitted.
Therefore, it is essential that the film be taut and clean to
11.2 Storage of Standards and Calibration Check
ensure reliable results. Film may become electrostatically
Samples—Store all standards and check samples in glass
charged during handling so it is important that the cell window
bottles in a cool, dark place until required. The glass bottles
doesnotattractanydust,fiber,andhair.Theanalyzerwillneed
shall be eit
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