ASTM D3120-08(2019)
(Test Method)Standard Test Method for Trace Quantities of Sulfur in Light Liquid Petroleum Hydrocarbons by Oxidative Microcoulometry
Standard Test Method for Trace Quantities of Sulfur in Light Liquid Petroleum Hydrocarbons by Oxidative Microcoulometry
SIGNIFICANCE AND USE
4.1 This test method is used to determine the concentration of sulfur in light liquid hydrocarbons, gasoline, and diesels and their additives, where such concentrations of sulfur can be detrimental to their production, performance, and use. The measurement of sulfur in the production and final product of gasoline and diesel is required for both regulatory purposes and to ensure maximum life expectancy of catalytic converters used in the automotive industry.
SCOPE
1.1 This test method covers the determination of sulfur concentration in the range from 3.0 mg/kg to 1000 mg/kg in light liquid hydrocarbons and fuels with oxygenates boiling in the range from 26 °C to 274 °C (80 °F to 525 °F).
Note 1: Preliminary data has shown that this test method is also applicable to the determination of sulfur in denatured fuel ethanol (Specification D4806), automotive spark ignition engine fuel (Specification D4814), Ed75–Ed85 (Specification D5798) or gasoline-oxygenate fuel blends with greater than 10 % ethanol. However, the precision for these materials has not been determined. Subcommittee D02.03 is undertaking activities to obtain precision statements for these materials.
1.2 Other materials falling within the distillation range specified in 1.1, but having sulfur concentrations above 1000 mg/kg, may be tested using appropriate dilutions to bring them within the specified limit. In addition, sample types that may be outside the specified distillation range, such as diesels and biodiesels, may be analyzed by this test method.
1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard. The preferred units are milligrams per kilogram (mg/kg).
1.4 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.For specific hazard statements, see Sections 7 – 9.
1.5 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
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: D3120 − 08 (Reapproved 2019)
Standard Test Method for
Trace Quantities of Sulfur in Light Liquid Petroleum
Hydrocarbons by Oxidative Microcoulometry
This standard is issued under the fixed designation D3120; 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.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1. Scope 2. Referenced Documents
1.1 This test method covers the determination of sulfur 2.1 ASTM Standards:
concentration in the range from 3.0mg⁄kg to 1000mg⁄kg in D1193Specification for Reagent Water
light liquid hydrocarbons and fuels with oxygenates boiling in D1298Test Method for Density, Relative Density, or API
the range from 26°C to 274°C (80°F to 525°F). Gravity of Crude Petroleum and Liquid Petroleum Prod-
ucts by Hydrometer Method
NOTE 1—Preliminary data has shown that this test method is also
D4052Test Method for Density, Relative Density, and API
applicable to the determination of sulfur in denatured fuel ethanol
Gravity of Liquids by Digital Density Meter
(Specification D4806), automotive spark ignition engine fuel (Specifica-
tion D4814), Ed75–Ed85 (Specification D5798) or gasoline-oxygenate
D4057Practice for Manual Sampling of Petroleum and
fuel blends with greater than 10% ethanol. However, the precision for
Petroleum Products
these materials has not been determined. Subcommittee D02.03 is
D4177Practice for Automatic Sampling of Petroleum and
undertaking activities to obtain precision statements for these materials.
Petroleum Products
1.2 Other materials falling within the distillation range
D4806Specification for Denatured Fuel Ethanol for Blend-
specified in 1.1, but having sulfur concentrations above
ing with Gasolines for Use asAutomotive Spark-Ignition
1000mg⁄kg,maybetestedusingappropriatedilutionstobring
Engine Fuel
them within the specified limit. In addition, sample types that
D4814Specification for Automotive Spark-Ignition Engine
may be outside the specified distillation range, such as diesels
Fuel
and biodiesels, may be analyzed by this test method.
D5798Specification for Ethanol Fuel Blends for Flexible-
1.3 The values stated in SI units are to be regarded as Fuel Automotive Spark-Ignition Engines
standard. No other units of measurement are included in this D6299Practice for Applying Statistical Quality Assurance
standard. The preferred units are milligrams per kilogram and Control Charting Techniques to Evaluate Analytical
(mg/kg). Measurement System Performance
1.4 This standard does not purport to address all of the 2.2 OSHA Regulations:
OSHA Regulations 29 CFR, paragraphs 1910.1000 and
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro- 1910.1200
priate safety, health, and environmental practices and deter-
3. Summary of Test Method
mine the applicability of regulatory limitations prior to use.For
specific hazard statements, see Sections7–9.
3.1 A liquid sample is introduced into a pyrolysis tube
1.5 This international standard was developed in accor-
maintained at a temperature between 900°C to 1200°C,
dance with internationally recognized principles on standard-
having a flowing stream of gas containing 50% to 80%
ization established in the Decision on Principles for the
oxygen and 20% to 50% inert gas (for example, argon,
Development of International Standards, Guides and Recom-
helium,andsoforth).Oxidativepyrolysisconvertsthesulfurto
mendations issued by the World Trade Organization Technical
sulfur dioxide, which then flows into a titration cell where it
Barriers to Trade (TBT) Committee.
reactswithtriiodideionpresentintheelectrolyte.Thetriiodide
1 2
This test method is under the jurisdiction of ASTM Committee D02 on For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Petroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility of contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Subcommittee D02.03 on Elemental Analysis. Standards volume information, refer to the standard’s Document Summary page on
Current edition approved May 1, 2019. Published June 2019. Originally the ASTM website.
approved in 1972. Last previous edition approved in 2014 as D3120–08(2014). Available from U.S. Government Printing Office, Superintendent of
DOI: 10.1520/D3120-08R19. Documents, 732 N. Capitol St., NW, Mail Stop: SDE, Washington, DC 20401.
*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
D3120 − 08 (2019)
ion consumed is coulometrically replaced and the total current 6.4 Pyrolysis Tube—Fabricatedfromquartzandconstructed
(I × t) required to replace it is a measure of the sulfur present so the sample is vaporized in a heated zone before the furnace
in the sample. andsweptintotheoxidationzonebyaninertcarriergas,where
thevaporizedsamplemixeswithoxygenandispyrolyzed.The
3.2 The reaction occurring in the titration cell as sulfur
inlet shall be constructed large enough to accommodate a
dioxide enters is:
sampleboatcompletelyintotheoxidationzoneofthepyrolysis
2 2 1
I 1SO 1H O→SO 13I 12H (1)
3 2 2 3
tube or allow the direct injection of the sample into the heated
zone before the furnace. The pyrolysis tube shall have side
The triiodide ion consumed in the above reaction is gener-
arms for the introduction of oxygen and inert carrier gas.
ated coulometrically thus:
2 2 2
6.5 Titration Cell—Consisting of a sensor/reference pair of
3I →I 12e (2)
electrodes to detect changes in triiodide ion concentration, a
3.3 These microequivalents of triiodide ion (iodine) are
generator anode-cathode pair of electrodes to maintain a
equal to the number of microequivalents of titratable SO ion
constant triiodide ion concentration, an inlet for gaseous
entering the titration cell.
sample from the pyrolysis tube, and an outlet to vent the exit
gases from the titration cell. The reference electrode can be
4. Significance and Use
either an Ag/AgCl double junction reference electrode or a
4.1 This test method is used to determine the concentration
platinum wire in a saturated triiodide half-cell. The sensor
ofsulfurinlightliquidhydrocarbons,gasoline,anddieselsand
electrode and both the anode and cathode electrodes of the
their additives, where such concentrations of sulfur can be
generator are made of platinum. The titration cell shall require
detrimental to their production, performance, and use. The
mixing, which can be accomplished with a magnetic stir bar,
measurement of sulfur in the production and final product of
stream of gas, or other suitable means. Other sensor and
gasolineanddieselisrequiredforbothregulatorypurposesand
reference electrodes may be used if they meet the performance
to ensure maximum life expectancy of catalytic converters
criteria of this test method.
used in the automotive industry.
NOTE 2—Take care not to use excessive stirring and possibly damage
5. Interferences
theelectrodeswiththestirbar.Thecreationofaslightvortexisadequate.
5.1 This test method is applicable in the presence of total
6.6 Microcoulometer—The apparatus’ microcoulometer,
halideconcentrationsofupto10timesthesulfurlevelandtotal
with variable attenuation and gain control, shall be capable of
nitrogen concentrations of up to 1000 times the sulfur level.
measuring the potential of the sensing-reference electrode pair
5.1.1 Stringent techniques shall be employed and all pos-
and compare this potential to a bias potential. By amplifying
sible sources of sulfur contamination eliminated to attain the
this potential difference and applying the difference to a
quantitative detectability capable with this test method. working-auxiliary pair of electrodes (the generator), a titrant is
generated. The microcoulometer integrates the amount of
5.2 This test method is not applicable in the presence of
current used, calculates the equivalent mass of sulfur titrated
total heavy metal concentrations (for example, Ni, V, Pb, and
and calculates the concentration of sulfur in the sample.
so forth) in excess of 500mg⁄kg (ppm).
6.7 Strip Chart Recorder (Optional)—To monitor and plot
6. Apparatus
the mV potential of the titration cell during the analysis.
6.1 Theconfigurationofthepyrolysistubeandfurnacemay
6.8 Flow Control—The apparatus shall be equipped with
be constructed as is desirable as long as the operating param-
flow controllers capable of maintaining a constant supply of
eters are met. Fig. 1 is typical of apparatus currently in use.
oxygen and inert carrier gas.
6.2 A typical assembly and oxidative gas flow through a
6.9 Dryer Tube—The oxidation of samples produces water
coulometric apparatus for the determination of trace sulfur is
vapor which, if allowed to condense between the exit of the
shown in Fig. 2.
pyrolysistubeandthetitrationcell,willabsorbtheSO formed
6.3 Furnace—Maintained at a temperature sufficient to
andresultinlowrecovery.Stepsshallbetakentopreventsuch
completely pyrolyze the organic matrix, 900°C to 1200°C,
an occurrence. This is easily accomplished by placing a
and completely oxidize the organically bound sulfur to SO .
phosphoricaciddehydrationtubebetweenthetitrationcelland
Independentlycontrolledinletandoutlettemperaturezonesare
exit of the pyrolysis tube. Other approaches, such as heating
optional.An electrical furnace has been found suitable to use.
tapeorpermeationtubes,canbeusedifprecisionandaccuracy
are not degraded.
6.10 Sampling Syringes—Microlitre syringes able to accu-
rately deliver 5mL to 80mL of sample are required. The
volume injected should not exceed 80% of a syringe’s
capacity.
6.11 Sample Inlet System—Either type of sample inlet
system described can be used.
6.11.1 Boat Inlet System—The inlet of the pyrolysis tube is
FIG. 1 Typical Pyrolysis Tube sealed to the boat inlet system. The system provides a cooled
D3120 − 08 (2019)
FIG. 2 Flow Diagram for Typical Coulometric Apparatus for Trace Sulfur Determination
areabeforethefurnaceforthesampleboatpriortoquantitative where such specifications are available. Other grades may be
introductionofsampleintotheboatandispurgedwiththeinert used, provided it is first ascertained that the reagent is of
carrier gas. The boat driving mechanism then fully inserts the sufficiently high purity to permit its use without lessening the
boat into the oxidation zone of the furnace. The drive mecha- accuracy of the determination.
nism shall advance and retract the sample boat into and out of
7.2 Purity of Water—Unless otherwise indicated, references
theoxidationzoneofthefurnaceatacontrolledandrepeatable
towatershallbeunderstoodtomeanreagentwaterconforming
rate (see Note 3).
to Specification D1193, Type II and III.
6.11.1.1 Boat Inlet Cooler (Optional)—Sample volatility
7.3 Quartz Wool—Grade fine.
and injection volume may require an apparatus capable of
cooling the sample boat prior to sample introduction. Thermo- 7.4 Acetic Acid (CH COOH)—Glacial acetic acid with spe-
electric coolers (peltier) or recirculating refrigerated liquid
cific gravity = 1.05. (Warning—Poison. Corrosive. Combus-
devices are strongly recommended. Switching sample boats tible.Maybefatalifswallowed.Causessevereburns.Harmful
between each analysis may prove effective, provided sample
if inhaled.)
size is not too large.
7.5 Phosphoric Acid (85 % w/w)—Orthophosphoric acid
6.11.1.2 Sample Boats—Quartz or other suitable material
(H PO ). (Warning—Poison. Corrosive. May be fatal if swal-
3 4
which will not react with the sample or sulfur compounds
lowed. Causes severe burns.)
being analyzed and able to withstand the temperatures ex-
7.6 Inert Gas—Argon or helium, high purity grade (HP),
tremes of the test method.
used as carrier gas. (Warning—Compressed gas under high
6.11.2 Syringe Inlet System—The system shall deliver a
pressure. Gas reduces oxygen available for breathing.)
quantitative amount of sample from a microlitre syringe into a
heated area before the oxidation zone of the pyrolysis tube at
7.7 Oxygen—High purity grade (HP), used as the reactant
acontrolledandrepeatablerate.Therethesampleisvolatilized
gas. (Warning—Oxygen vigorously accelerates combustion.)
and the inert carrier gas stream purging the heated area
7.8 Gas Regulators—Two-stagegasregulatorsshallbeused
transports the volatilized sample into the oxidation zone of the
for the oxygen and inert carrier gas.
pyrolysis furnace. An adjustable drive mechanism capable of
7.9 Cell Electrolyte Solution—Dissolve 0.5g of potassium
injectingthesamplefromamicrolitresyringeataconstantrate
iodide(KI)and0.6gofsodiumazide(NaN )inapproximately
between 0.5mL⁄s to 1.0mL⁄s is required (see Note 3).
500mL of high-purity water, add 6mL of glacial acetic acid
NOTE 3—Take care not to introduce the sample too fast into the
(CH COOH), and dilute to 1000mL or follow the manufac-
oxidationzoneofthefurnaceandoverloadthecombustioncapacityofthe
turer’s specifications.
pyrolysis tube. Program the sample inlet system to deliver the sample at
a sufficiently controlled and repeatable rate to prevent any incomplete
NOTE 4—Take care to store bulk quantities of the electrolyte in a dark
combustion by-products (coke or soot) from forming at the exit of the
place. It is recommended to prepare fresh electrolyte at least every three
pyrolysis tube.
months.
6.12 Balance—With a weighing precision of 60.01mg.
Reagent Chemicals, American Chemical Society Specifications, American
7. Reagents and Materials
Chemical Society, Washington, DC. For Suggestions on the testing of reagents not
listed by the American Chemical Society, see Annual Standards for Laboratory
7.1 Purity of Reagents—Reagent grade chemicals shall be
Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia
used in all tests. Unless otherwise indicated, it is intended that
and National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,
all reagents shall conform to the specifications of the Commit-
MD.
tee onAnalytical Reagents of theAmerican Chemical Society, High-purity grade gas has a minimum purity of 99.995%.
D3120 − 08 (2019)
typically have a useful life of about 3 months.
7.10 Sodium Azide (NaN ), fine granular. (Warning—
NOTE 8
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