ASTM D6334-12(2017)
(Test Method)Standard Test Method for Sulfur in Gasoline by Wavelength Dispersive X-Ray Fluorescence
Standard Test Method for Sulfur in Gasoline by Wavelength Dispersive X-Ray Fluorescence
SIGNIFICANCE AND USE
4.1 Knowledge of the presence of sulfur in petroleum products, especially fuels, helps predict performance characteristics, potential corrosion problems, and vehicle emission levels. In addition, some regulatory agencies mandate reduced levels of sulfur in reformulated type gasolines.
SCOPE
1.1 This test method covers the quantitative determination of total sulfur in gasoline and gasoline-oxygenate blends. The Pooled Limit of Quantitation (PLOQ) was determined to be 15 mg/kg. Therefore, the practical range for this test method is from 15 mg/kg to 940 mg/kg.
Note 1: This concentration range is based on that used in the interlaboratory round robin, which shows that the range of sulfur in the round robin samples was from 1.5 mg/kg to 940 mg/kg; however, below 15 mg/kg, the reproducibility approaches 100 % of the concentration.
1.2 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 limitation prior to use.
1.3 The values stated in SI units are to be regarded as the standard. The preferred units are mg/kg sulfur.
1.4 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
General Information
Relations
Buy Standard
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NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.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
Designation: D6334 − 12 (Reapproved 2017)
Standard Test Method for
Sulfur in Gasoline by Wavelength Dispersive X-Ray
Fluorescence
This standard is issued under the fixed designation D6334; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope D4057Practice for Manual Sampling of Petroleum and
Petroleum Products
1.1 This test method covers the quantitative determination
D4177Practice for Automatic Sampling of Petroleum and
of total sulfur in gasoline and gasoline-oxygenate blends. The
Petroleum Products
Pooled Limit of Quantitation (PLOQ) was determined to be
D4294Test Method for Sulfur in Petroleum and Petroleum
15mg⁄kg.Therefore,thepracticalrangeforthistestmethodis
Products by Energy Dispersive X-ray Fluorescence Spec-
from 15mg⁄kg to 940mg⁄kg.
trometry
NOTE 1—This concentration range is based on that used in the
D5453Test Method for Determination of Total Sulfur in
interlaboratory round robin, which shows that the range of sulfur in the
Light Hydrocarbons, Spark Ignition Engine Fuel, Diesel
round robin samples was from 1.5mg⁄kg to 940mg⁄kg; however, below
Engine Fuel, and Engine Oil by Ultraviolet Fluorescence
15mg⁄kg, the reproducibility approaches 100% of the concentration.
D5842Practice for Sampling and Handling of Fuels for
1.2 This standard does not purport to address all of the
Volatility Measurement
safety concerns, if any, associated with its use. It is the
D5854Practice for Mixing and Handling of Liquid Samples
responsibility of the user of this standard to establish appro-
of Petroleum and Petroleum Products
priate safety and health practices and determine the applica-
D6299Practice for Applying Statistical Quality Assurance
bility of regulatory limitation prior to use.
and Control Charting Techniques to Evaluate Analytical
1.3 The values stated in SI units are to be regarded as the
Measurement System Performance
standard. The preferred units are mg/kg sulfur.
D6792Practice for Quality Management Systems in Petro-
1.4 This international standard was developed in accor-
leum Products, Liquid Fuels, and Lubricants Testing
dance with internationally recognized principles on standard-
Laboratories
ization established in the Decision on Principles for the
Development of International Standards, Guides and Recom- 3. Summary of Test Method
mendations issued by the World Trade Organization Technical
3.1 The sample is placed in the X-ray beam, and the
Barriers to Trade (TBT) Committee.
intensity of the sulfur Kα line at 5.373Å is measured. The
intensity of a corrected background, measured at a recom-
2. Referenced Documents
mended wavelength of 5.190Å, or if a rhodium tube is used,
2.1 ASTM Standards: 5.437Å, is subtracted from this intensity. The resultant net
D2622Test Method for Sulfur in Petroleum Products by
counting rate is then compared to a previously prepared
Wavelength Dispersive X-ray Fluorescence Spectrometry calibration curve or equation to obtain the concentration of
D3210Test Method for Comparing Colors of Films from sulfur in mg/kg. (Warning—Exposure to excessive quantities
Water-Emulsion Floor Polishes of X radiation is injurious to health.Therefore, it is imperative
D4045Test Method for Sulfur in Petroleum Products by that the operator avoid exposing any part of his or her person,
Hydrogenolysis and Rateometric Colorimetry
not only to primary X-rays, but also to secondary or scattered
radiationthatmightbepresent.TheX-rayspectrometershould
be operated in accordance with the regulations of recommen-
This test method is under the jurisdiction of ASTM Committee D02 on
dations governing the use of ionizing radiation.)
Petroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility of
Subcommittee D02.03 on Elemental Analysis.
4. Significance and Use
CurrenteditionapprovedMay1,2017.PublishedJuly2017.Originallyapproved
4.1 Knowledge of the presence of sulfur in petroleum
in 1962. Last previous edition approved in 2012 as D6334–12. DOI: 10.1520/
D6334-12R17.
products, especially fuels, helps predict performance
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
characteristics,potentialcorrosionproblems,andvehicleemis-
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
sion levels. In addition, some regulatory agencies mandate
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. reduced levels of sulfur in reformulated type gasolines.
Copyright ©ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA19428-2959. United States
D6334 − 12 (2017)
5. Interferences 7.7 Calibration Check Standards, one or more liquid petro-
leum or product standards of known sulfur content (which do
5.1 Fuels with compositions that vary from those specified
not represent one of the samples prepared in Section 9) are
in 9.1 may be analyzed with standards made from base
used to verify the accuracy of the calibration curve.
materials that are of similar composition to minimize matrix
effects. 7.8 Quality Control (QC) Sample, one or more stable liquid
5.1.1 Fuels containing oxygenates may be analyzed using petroleumorproductsamples,whichareusedtoverifythatthe
standardspreparedwithsimilaramountsofthesameoxygenate measurementsystemisincontrol.PreferablytheQCsample(s)
added to the standard dilution matrix. However, round robin should be representative of the samples typically analyzed. In
studiesdonebytheWesternStatesPetroleumAssociationhave cases where volatility of the QC sample(s) may affect the
shown no significant bias in determining sulfur in gasolines sample integrity, precautions need to be taken to minimize or
with and without oxygenates at regulatory levels (0 to 2.7 eliminate sample losses prior to analysis to ensure that a stable
weight percent oxygen). and representative sample can be taken and analyzed over the
5.1.2 Methanol fuels (M85 and M100) exhibit interferences period of intended use. It is permissible to use calibration
at this level of detection (<100mg⁄kg). They can be analyzed standards for this purpose. Since standard samples are dis-
using a calibration curve produced by diluting the standards in carded after each determination, it is recommended that a
a similar matrix of M85 or M100 or by Test Method D2622. lower cost material be used for daily calibration checks.
6. Apparatus 8. Sampling and Specimen Preparation
6.1 Wavelength Dispersive X-Ray Fluorescence Spectrom- 8.1 Samples shall be taken in accordance with the instruc-
eter (WDXRF), equipped for soft ray detection in the 5.37Å tions in Practice D4057, D4177, D5842,or D5854, where
range. For optimum sensitivity to sulfur, equip the instrument appropriate.
with the following:
8.2 Clean and dry reusable cells before use. Disposable
6.1.1 Optical Path, of helium.
sample cups are not to be reused. Window material usually is
6.1.2 Pulse-Height Analyzer, or other means of energy
8 µm polyester, 8µm polycarbonate, or 6µm polypropylene
discrimination.
film. Renewal of the window of the sample cup is essential for
6.1.3 Detector, designed for the detection of long wave-
the measurement of each sample.Avoid touching the inside of
length X-rays.
the sample cup, the portion of the window film in the cup, or
6.1.4 Analyzing Crystal,suitableforthedispersionofsulfur
the instrument window that is exposed to X-rays. Oil from
Kα X-rays within the angular range of the spectrometer
fingerprints can affect the reading when analyzing for low
employed. Pentaerythritol and germanium are the most
levels of sulfur. Wrinkles in the film will affect the number of
popular,althoughmaterials,suchasEDDT,ADP,graphite,and
sulfur X-rays transmitted. Therefore, the importance of the
quartz, may be used.
film’s tautness and cleanliness cannot be over stressed. Reca-
6.1.5 X-Ray Tube, capable of exciting sulfur K radiation.
α
librate the analyzer when you change the type or thickness of
Tubes with anodes of rhodium, chromium, and scandium are
the window film.
most popular, although other anodes may be suitable.
8.3 Polyester films often contain impurities that may affect
the measurement of lowlevels of sulfur and may vary fromlot
7. Reagents
tolot.Therefore,ifusingapolyesterfilm,checkthecalibration
7.1 Di-n-Butyl Sulfide (MW – 146.30), a high-purity grade
with the start of each new roll.
standard with a certified sulfur analysis.
8.4 X-ray films may vary in thickness from batch to batch.
7.2 Thiophene MW– 84.14), a high-purity (98+ %) grade
Check the calibration when starting a new roll of any film.
standard with a certified sulfur analysis.
8.5 Samples of high aromatic count may dissolve polyester
7.3 2-Methylthiophene MW– 98.17), a high purity (98+ %)
andpolycarbonatefilms.Inthesecases,othermaterialsbesides
grade standard with a standard sulfur analysis.
thesefilmsmaybeusedforX-raywindows,providedthatthey
7.4 2,2,4-Trimethylpentane, (isooctane), reagent grade, do not contain any elemental impurities that can adversely
affect the results obtained by this test method.
MW-114.23.
7.5 Methylbenzene, (Toluene), reagent grade, MW-92.14.
9. Calibration
7.6 Drift Correction Monitor(s), (Optional), several differ-
9.1 Prepare calibration standards by the careful preparation
ent materials have been found to be suitable for use as drift
by mass of a 50:50 mixture (based on sulfur content) of the
correction monitors. Examples of sulfur containing materials
certified thiophene and 2-methylthiophene or n-butyl sulfide
that meet these requirements are renewable liquid petroleum
with 20% to 80% mixture of toluene–isooctane or other
materials,semipermanentsolids,pressedpowderpellets,metal
suitablebasematerial(see5.1).Exactstandardsofthenominal
alloys, or fused glass disks. Bracket the calibration range with
sulfur concentrations listed in Table 1 are recommended.
concentrations of monitor samples. The counting rate for each
monitor is determined during calibration (see 9.7) and again at 9.2 Preparation of Stock Standard: Weigh approximately
thetimeofanalysis(see10.1).Thesecountingratesareusedto 0.657g of thiophene and 0.767g of 2-methylthiophene and
calculate a drift correction factor (see 11.1). record the masses to the nearest 0.1mg, or weigh 2.286 of
D6334 − 12 (2017)
TABLE 1 Nominal Sulfur Standards
9.6.1 Using the software and algorithms supplied by the
Range 1 Range 2 instrument manufacturer.
Sulfur Concentration, Sulfur Concentration,
9.6.2 Fitting the data to an equation of the type:
mg/kg mg/kg
0 100
S 5 aR1b (3)
5 250
10 500
where:
50 1000
S = sulfur concentration, mg/kg,
100 —
R = net intensity for the sulfur radiation,
a = slope of the calibration curve, and
b = intercept of the calibration curve.
9.6.3 Plot corrected net intensity in counts per second (cps)
n-butyl sulfide to the nearest 0.1 mg. Add the standard
versus sulfur concentration. Plot data in two ranges listed in
materials to a tared 100mL volumetric flask. Add mixed
Table 1.
solvent of 20% toluene and 80% isooctane (by volume) or
9.7 Duringcollectionofcalibrationdata,measuretheinten-
other base material (see 5.1) to a net mass of 50.000g +
sity of the drift monitor standards. Use the intensities from
0.010g. This stock standard contains approximately 10mg⁄g
these standards to correct for day to day instrument sensitivity.
sulfur. Correct the concentration by multiplying the measured
This value corresponds to A in Eq 5, Section 11. Many
masses by the sulfur equivalency in each of the standards, that
instrumentmanufacturershavebuiltdriftcorrectionprocedures
is thiophene grams × 0.3803 × purity plus 2-methylthiophene
into their software.
grams × 0.3260 × purity (or n-butyl sulfide grams × 0.2191 ×
9.8 At the completion of the calibration, measure one or
purity) = weight of sulfur in the standard solution. Divide this
more independent calibration check standards to verify the
number by the total mass of the standards and base material
accuracyofthecalibrationcurve.Thesestandards(see7.7)are
added to them, multiply by 1000 mg/g and the result is the
independent of the calibration set. The measured value shall
actual sulfur concentration in mg/g. This calculation is as
agree with the standard value within 62% relative or 2ppm,
follows:
whichever is greater.
T 30.3803 3P1M 30.3260 3P
S, mg/g 51000 3 (1)
F NOTE 3—NIST traceable gasoline standards are available at the
1mg⁄kg, 10mg⁄kg, 40mg⁄kg, and 300mg⁄kg levels. Other concentra-
DB 30.2187 3P
tions may be prepared by dilution of these standards with a solvent of
S, mg/g 51000 3 (2)
F
similar matrix to the standards previously prepared.
NOTE4—NISThassuggesteda“designer”methodforthepreparation
where:
ofNISTtraceablefossilfuelstandardswithconcentrationsintermediateto
S = final sulfur concentration, SRM values for sulfur. Laboratories can mix and prepare standards for
distillate fuels oils, residual fuel oil in almost any desired concentrations
T = mass of thiophene added,
with uncertainties that are calculable and traceable to NIST-certified
M = mass of 2-methylthiophene added,
values. This method enables the SRM user to create a customized series
DB = mass of di- n-butyl sulfide added,
of calibration and quality control test samples.
P = purity of the standard material, and
NOTE 5—A DVD available from NIST includes the above cited paper
F = final mass of mixture.
plus subsequent papers dealing with this subject as well as programmable
spreadsheet to calculate blend concentrations and uncertainties. Some of
9.3 Preparation of Diluted Standard: Dilute 25.0mL of
the subsequent papers discuss the actual procedure to use when mixing
stock standard to 250mLusing the base material. This gives a
rather than the proof of concept given in the first paper.
standard of approximately 1000mg⁄kg. Divide the standard
10. Procedure
concentration calculated in 9.2 by 10 to determine the actual
concentration.
10.1 Measure the intensity of the drift correction monitor(s)
used in 9.7. The value determined corresponds to B in Eq 5,
9.4 Serial Dilutions: Prepare serial dilutions of the diluted
Section 11. This measurement may not be required on high
standard by diluting the following volumes to 100mL using
stability instrumentation. Determine the value of F'in Eq 6,
the base material:
Section 11 at regular intervals by measuring the peak and
0.5 mL = 5 mg/kg
1.0 mL = 10 mg/kg background count rates on the solvent blank. This measure-
5.0 mL = 50 mg/kg
ment may not be needed on some instruments.
10.0 mL = 100 mg/kg
25.0 mL = 250 mg/kg
10.2 Place the sample in an approp
...
This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: D6334 − 12 D6334 − 12 (Reapproved 2017)
Standard Test Method for
Sulfur in Gasoline by Wavelength Dispersive X-Ray
Fluorescence
This standard is issued under the fixed designation D6334; 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*Scope
1.1 This test method covers the quantitative determination of total sulfur in gasoline and gasoline-oxygenate blends. The Pooled
Limit of Quantitation (PLOQ) was determined to be 1515 mg mg/kg. ⁄kg. Therefore, the practical range for this test method is from
1515 mg ⁄kg to 940 940 mg mg/kg.⁄kg.
NOTE 1—This concentration range is based on that used in the interlaboratory round robin, which shows that the range of sulfur in the round robin
samples was from 1.51.5 mg ⁄kg to 940940 mg mg/kg; ⁄kg; however, below 1515 mg mg/kg, ⁄kg, the reproducibility approaches 100 % of the
concentration.
1.2 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
limitation prior to use.
1.3 The values stated in SI units are to be regarded as the standard. The preferred units are mg/kg sulfur.
1.4 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
D2622 Test Method for Sulfur in Petroleum Products by Wavelength Dispersive X-ray Fluorescence Spectrometry
D3210 Test Method for Comparing Colors of Films from Water-Emulsion Floor Polishes
D4045 Test Method for Sulfur in Petroleum Products by Hydrogenolysis and Rateometric Colorimetry
D4057 Practice for Manual Sampling of Petroleum and Petroleum Products
D4177 Practice for Automatic Sampling of Petroleum and Petroleum Products
D4294 Test Method for Sulfur in Petroleum and Petroleum Products by Energy Dispersive X-ray Fluorescence Spectrometry
D5453 Test Method for Determination of Total Sulfur in Light Hydrocarbons, Spark Ignition Engine Fuel, Diesel Engine Fuel,
and Engine Oil by Ultraviolet Fluorescence
D5842 Practice for Sampling and Handling of Fuels for Volatility Measurement
D5854 Practice for Mixing and Handling of Liquid Samples of Petroleum and Petroleum Products
D6299 Practice for Applying Statistical Quality Assurance and Control Charting Techniques to Evaluate Analytical Measure-
ment System Performance
D6792 Practice for Quality Management Systems in Petroleum Products, Liquid Fuels, and Lubricants Testing Laboratories
3. Summary of Test Method
3.1 The sample is placed in the X-ray beam, and the intensity of the sulfur Kα line at 5.373 Å 5.373 Å is measured. The intensity
of a corrected background, measured at a recommended wavelength of 5.190 Å, 5.190 Å, or if a rhodium tube is used, 5.437 Å,
5.437 Å, is subtracted from this intensity. The resultant net counting rate is then compared to a previously prepared calibration
curve or equation to obtain the concentration of sulfur in mg/kg. (Warning—Exposure to excessive quantities of X radiation is
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, 2012May 1, 2017. Published December 2012July 2017. Originally approved in 1962. Last previous edition approved in 20072012 as
D6334D6334 – 12.–07. DOI: 10.1520/D6334-12.10.1520/D6334-12R17.
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 Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D6334 − 12 (2017)
injurious to health. Therefore, it is imperative that the operator avoid exposing any part of his or her person, not only to primary
X-rays, but also to secondary or scattered radiation that might be present. The X-ray spectrometer should be operated in accordance
with the regulations of recommendations governing the use of ionizing radiation.)
4. Significance and Use
4.1 Knowledge of the presence of sulfur in petroleum products, especially fuels, helps predict performance characteristics,
potential corrosion problems, and vehicle emission levels. In addition, some regulatory agencies mandate reduced levels of sulfur
in reformulated type gasolines.
5. Interferences
5.1 Fuels with compositions that vary from those specified in 9.1 may be analyzed with standards made from base materials
that are of similar composition to minimize matrix effects.
D6334 − 12 (2017)
5.1.1 Fuels containing oxygenates may be analyzed using standards prepared with similar amounts of the same oxygenate added
to the standard dilution matrix. However, round robin studies done by the Western States Petroleum Association have shown no
significant bias in determining sulfur in gasolines with and without oxygenates at regulatory levels (0 to 2.7 weight percent
oxygen).
5.1.2 Methanol fuels (M85 and M100) exhibit interferences at this level of detection (<100(<100 mg mg/kg). ⁄kg). They can
be analyzed using a calibration curve produced by diluting the standards in a similar matrix of M85 or M100 or by Test Method
D2622.
6. Apparatus
6.1 Wavelength Dispersive X-Ray Fluorescence Spectrometer (WDXRF), equipped for soft ray detection in the 5.37 Å 5.37 Å
range. For optimum sensitivity to sulfur, equip the instrument with the following:
6.1.1 Optical Path, of helium.
6.1.2 Pulse-Height Analyzer, or other means of energy discrimination.
6.1.3 Detector, designed for the detection of long wavelength X-rays.
6.1.4 Analyzing Crystal, suitable for the dispersion of sulfur Kα X-rays within the angular range of the spectrometer employed.
Pentaerythritol and germanium are the most popular, although materials, such as EDDT, ADP, graphite, and quartz, may be used.
6.1.5 X-Ray Tube, capable of exciting sulfur K radiation. Tubes with anodes of rhodium, chromium, and scandium are most
α
popular, although other anodes may be suitable.
7. Reagents
7.1 Di-n-Butyl Sulfide (MW – 146.30),a high-purity grade standard with a certified sulfur analysis.
7.2 Thiophene MW– 84.14),a high-purity (98+ %) grade standard with a certified sulfur analysis.
7.3 2-Methylthiophene MW – 98.17),a high purity (98+ %) grade standard with a standard sulfur analysis.
7.4 2,2,4-Trimethylpentane, (isooctane), reagent grade, MW-114.23.
7.5 Methylbenzene, (Toluene), reagent grade, MW-92.14.
7.6 Drift Correction Monitor(s), (Optional), several different materials have been found to be suitable for use as drift correction
monitors. Examples of sulfur containing materials that meet these requirements are renewable liquid petroleum materials,
semipermanent solids, pressed powder pellets, metal alloys, or fused glass disks. Bracket the calibration range with concentrations
of monitor samples. The counting rate for each monitor is determined during calibration (see 9.7) and again at the time of analysis
(see 10.1). These counting rates are used to calculate a drift correction factor (see 11.1).
7.7 Calibration Check Standards, one or more liquid petroleum or product standards of known sulfur content (which do not
represent one of the samples prepared in Section 9) are used to verify the accuracy of the calibration curve.
7.8 Quality Control (QC) Sample, one or more stable liquid petroleum or product samples, which are used to verify that the
measurement system is in control. Preferably the QC sample(s) should be representative of the samples typically analyzed. In cases
where volatility of the QC sample(s) may affect the sample integrity, precautions need to be taken to minimize or eliminate sample
losses prior to analysis to ensure that a stable and representative sample can be taken and analyzed over the period of intended use.
It is permissible to use calibration standards for this purpose. Since standard samples are discarded after each determination, it is
recommended that a lower cost material be used for daily calibration checks.
8. Sampling and Specimen Preparation
8.1 Samples shall be taken in accordance with the instructions in Practice D4057, D4177, D5842, or D5854, where appropriate.
8.2 Clean and dry reusable cells before use. Disposable sample cups are not to be reused. Window material usually is 8 μm
polyester, 8 μm 8 μm polycarbonate, or 6 μm 6 μm polypropylene film. Renewal of the window of the sample cup is essential for
the measurement of each sample. Avoid touching the inside of the sample cup, the portion of the window film in the cup, or 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 tautness and
cleanliness cannot be over stressed. Recalibrate the analyzer when you change the type or thickness of the window film.
8.3 Polyester films often contain impurities that may affect the measurement of low levels of sulfur and may vary from lot to
lot. Therefore, if using a polyester film, check the calibration with the start of each new roll.
8.4 X-ray films may vary in thickness from batch to batch. Check the calibration when starting a new roll of any film.
8.5 Samples of high aromatic count may dissolve polyester 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 that can adversely affect the
results obtained by this test method.
D6334 − 12 (2017)
9. Calibration
9.1 Prepare calibration standards by the careful preparation by mass of a 50:50 mixture (based on sulfur content) of the certified
thiophene and 2-methylthiophene or n-butyl sulfide with 2020 % to 80 % mixture of toluene–isooctane or other suitable base
material (see 5.1). Exact standards of the nominal sulfur concentrations listed in Table 1 are recommended.
9.2 Preparation of Stock Standard: Weigh approximately 0.657 g 0.657 g of thiophene and 0.767 g 0.767 g of
2-methylthiophene and record the masses to the nearest 0.1 mg, 0.1 mg, or weigh 2.286 of n-butyl sulfide to the nearest 0.1 mg.
Add the standard materials to a tared 100 mL 100 mL volumetric flask. Add mixed solvent of 20 % toluene and 80 % isooctane
(by volume) or other base material (see 5.1) to a net mass of 50.00050.000 g + 0.010 g. 0.010 g. This stock standard contains
approximately 1010 mg mg/g ⁄g sulfur. Correct the concentration by multiplying the measured masses by the sulfur equivalency
in each of the standards, that is thiophene grams × 0.3803 × purity plus 2-methylthiophene grams × 0.3260 × purity (or n-butyl
sulfide grams × 0.2191 × purity) = weight of sulfur in the standard solution. Divide this number by the total mass of the standards
and base material added to them, multiply by 1000 mg/g and the result is the actual sulfur concentration in mg/g. This calculation
is as follows:
T 30.3803 3P1M 30.3260 3P
S, mg/g5 1000 3 (1)
F
DB 30.2187 3P
S, mg/g5 1000 3 (2)
F
where:
where:
S = final sulfur concentration,
T = mass of thiophene added,
M = mass of 2-methylthiophene added,
DB = mass of di- n-butyl sulfide added,
P = purity of the standard material, and
F = final mass of mixture.
9.3 Preparation of Diluted Standard: Dilute 25.0 mL 25.0 mL of stock standard to 250 mL 250 mL using the base material. This
gives a standard of approximately 10001000 mg mg/kg. ⁄kg. Divide the standard concentration calculated in 9.29.2 by 10 to
determine the actual concentration.
9.4 Serial Dilutions: Prepare serial dilutions of the diluted standard by diluting the following volumes to 100 mL 100 mL using
the base material:
0.5 mL = 5 mg/kg
1.0 mL = 10 mg/kg
5.0 mL = 50 mg/kg
10.0 mL = 100 mg/kg
25.0 mL = 250 mg/kg
50.0 mL = 500 mg/kg
Diluted Standard = 1000 mg/kg
NOTE 2—Prepare calibrations up to 10001000 mg mg/kg ⁄kg sulfur, and dilute samples with higher concentrations of sulfur to within this concentration
range.
9.5 Establish calibration curve data by carefully measuring the net intensity of the emitted sulfur radiation from each of the
standards by the procedure described in Sections 10 and 11.
9.6 Construct a calibration model by:
9.6.1 Using the software and algorithms supplied by the instrument manufacturer.
9.6.2 Fitting the data to an equation of the type:
S 5 aR1b (3)
TABLE 1 Nominal Sulfur Standards
Range 1 Range 2
Sulfur Concentration, Sulfur Concentration,
mg/kg mg/kg
0 100
5 250
10 500
50 1000
100 —
D6334 − 12 (2017)
where:
S = sulfur concentration, mg/kg,
R = net intensity for the sulfur radiation,
a = slope of the calibration curve, and
b = intercept of the calibration curve.
9.6.3 Plot corrected net intensity in counts per second (cps) versus sulfur concentration. Plot data in two ranges listed in Table
1.
9.7 During collection of calibration data, measure the intensity of the drift monitor standards. Use the intensities from these
standards to correct for day to day instrument sensitivity. This value corresponds to A in Eq 5, Section 11. Many instrument
manufacturers have built drift correction procedures into their software.
9.8 At the completion of the calibration, measure one or more independent calibration check standards to verify the accuracy
of the calibration curve. These standards (see 7.7) are independent of the calibration set. The measured value shall agree with the
standard value within 62 % relative or 2 ppm, 2 ppm, whichever is greater.
NOTE 3—NIST traceable gasoline standards are available at the 1,1 mg 10,⁄kg, 10 mg 40,⁄kg, 40 mg ⁄kg, and 30030
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.