EN ISO 20846:2026
(Main)Petroleum and related products - Determination of sulfur content of automotive fuels - Ultraviolet fluorescence method (ISO 20846:2026)
- Abstract
This document specifies an ultraviolet (UV) fluorescence test method for the determination of the sulfur content of the following products:
having sulfur contents in the range 3 mg/kg to 500 mg/kg:
motor gasolines containing up to a mass fraction of 3,7 % (3,7 % (m/m)) of oxygen [including those blended with a volume fraction of ethanol up to about 10 % (10 % (V/V))];
diesel fuels, including those containing up to a volume fraction of about 50 % of fatty acid methyl ester (FAME);
having sulfur contents in the range of 3 mg/kg to 45 mg/kg:
synthetic fuels, such as hydrotreated vegetable oil (HVO) and gas to liquid (GTL);
having sulfur contents in the range of 3 mg/kg to 30 mg/kg:
neat FAME (B100) and diesel fuels containing volume fraction of more than 50 % of FAME.
Other products (for example process feeds and effluents) can be analysed and other sulfur contents can be determined according to this test method, however, no precision data for products other than automotive fuels and for results outside the specified range have been established for this document. Halogens interfere with this detection technique at concentrations above approximately 3 500 mg/kg.
- Status
- Published
- Publication Date
- 28-Jul-2026
- Technical Committee
- CEN/TC 19 - Petroleum products, lubricants and related products
- Drafting Committee
- CEN/TC 19/WG 27 - Elemental analysis of petroleum and related products
- Current Stage
- 6060 - Definitive text made available (DAV) - Publishing
- Start Date
- 29-Jul-2026
- Completion Date
- 29-Jul-2026
EN ISO 20846:2026 is a CEN European Standard that adopts ISO 20846:2026 without modification. It specifies an ultraviolet (UV) fluorescence test method for determining sulfur content in automotive fuels and related fuels. In practice, it is used for laboratory measurement of sulfur in fuel samples, with results reported in mg/kg.
What does EN ISO 20846:2026 specify?
EN ISO 20846:2026 specifies a UV fluorescence method for sulfur determination in several fuel types and defines the sample ranges for which precision data are established. It also sets out the document structure: scope, normative references, principle, reagents and materials, apparatus, sampling and sample handling, apparatus preparation, calibration and verification, procedure, calculation, expression of results, precision, and test report.
| Product covered by EN ISO 20846:2026 | Sulfur range stated in the document |
|---|---|
| Motor gasolines containing up to 3.7 % (m/m) oxygen, including blends with about 10 % (V/V) ethanol | 3 mg/kg to 500 mg/kg |
| Diesel fuels, including those containing about 50 % (V/V) FAME | 3 mg/kg to 500 mg/kg |
| Synthetic fuels such as HVO and GTL | 3 mg/kg to 45 mg/kg |
| Neat FAME (B100) and diesel fuels containing more than 50 % FAME | 3 mg/kg to 30 mg/kg |
The document also notes that other products, such as process feeds and effluents, can be analysed by the method, but precision data are only established for automotive fuels and for results within the stated ranges. Halogens interfere with the technique above about 3 500 mg/kg.
What are the key requirements of EN ISO 20846:2026?
EN ISO 20846:2026 requires a controlled combustion-and-detection setup, careful calibration, and repeated measurements. The practical goal is to make sure the sulfur signal comes from the sample, not from contamination, poor calibration, or unstable instrument conditions.
Sample preparation and measurement conditions
Clause 4 states that the sample is either injected directly or introduced by a sample boat into a hot combustion tube, where sulfur is converted to sulfur dioxide and then measured by UV fluorescence. The furnace temperature must be high enough to pyrolyze the sample and oxidize all sulfur, typically in the 1 000 °C to 1 100 °C range depending on the furnace design.
Clause 7 and Clause 10 make sample handling part of the method. Samples should be taken by manual sampling or automatic pipeline sampling, kept cool where practical, mixed before testing if they have stood, and their density determined by ISO 3675 or ISO 12185 when needed for calculation. This matters because evaporation, contamination, or density errors can affect the final sulfur result.
Reagents, materials, and apparatus
Clause 5 requires high-purity inert gas and oxygen, suitable solvents such as toluene or isooctane, sulfur compounds for stock solutions, quality control samples, and quartz wool. Clause 6 lists the essential apparatus: furnace, quartz combustion tube, flow controllers, vapour drier, UV fluorescence detector, microlitre syringe, sample inlet system, balance, and Class A volumetric flasks.
These requirements matter because the method depends on clean combustion and stable detector response. Clause 6 also warns that UV exposure is hazardous and recommends checking for nitrogen interference when relevant.
Calibration and verification
Clause 9 gives two calibration approaches. Multi-point calibration is recommended, with at least four standards and a linear calibration curve whose correlation coefficient is at least 0.995. The document gives suggested calibration ranges in Table 1 and states that the expected sulfur level of the sample should sit near the middle of the curve.
Single-point calibration is allowed, but Clause 9 warns that it can create errors when the product is not well known. Clause 9.3 requires verification with a quality control sample at the start of a series and at least every 20 analyses during a long series. In practice, this is the check that tells the laboratory whether the calibration is still valid before it relies on a batch of results.
Calculation and result validation
Clause 10 calls for three determinations of the sample, and Clause 11 says the reported sulfur content is the average of those three results. When the sulfur level is low compared with the calibration range, the intercept must be checked: if the absolute intercept is more than 10 % of the slope, the curve must be rebuilt closer to the sample level.
Clause 11 also requires dilution correction when the sample has been diluted, and Clause 12 sets the reporting resolution. Results above 60 mg/kg are reported to the nearest 1 mg/kg, and results below 60 mg/kg to the nearest 0.1 mg/kg. That distinction matters because low-level sulfur work needs finer reporting than high-level fuel checks.
Precision and what it means for routine use
Clause 13 gives repeatability and reproducibility statements for gasoline and diesel ranges, plus precision estimates in Table 4. The precision basis includes studies for paraffinic diesel fuels and for FAME from different origins, which supports use of the same precision statements up to 30 mg/kg for FAME. For a laboratory, these values are the reference for judging whether two results are close enough to be considered consistent.
What terms does EN ISO 20846:2026 define?
EN ISO 20846:2026 uses a number of technical abbreviations and fuel names that readers need to recognize quickly.
- UV - ultraviolet, the radiation used to excite sulfur dioxide in the detector stage.
- FAME - fatty acid methyl ester, used in biodiesel and in blends with diesel fuel.
- B100 - neat FAME, meaning 100 % FAME.
- HVO - hydrotreated vegetable oil, a synthetic fuel named in the scope.
- GTL - gas to liquid, another synthetic fuel named in the scope.
- DBT - dibenzothiophene, one of the sulfur compounds used to prepare stock solution.
- DBS - dibutyl sulfide, one of the sulfur compounds used for calibration materials.
- DBDS - dibutyl disulfide, another sulfur compound used for stock solution preparation.
- TNA - thionaphthene (benzothiophene), a sulfur compound used in calibration work.
Who uses EN ISO 20846:2026?
EN ISO 20846:2026 is used by laboratories and quality-control teams that measure sulfur in motor gasolines, diesel fuels, synthetic fuels, and FAME-containing fuels. It supports the full workflow from sampling and sample handling through calibration, verification, calculation, and reporting.
It is particularly relevant where fuel sulfur must be checked as part of product release, incoming inspection, or routine monitoring. It also helps analysts working on low-level sulfur measurements because the document sets out how to avoid carry-over, how to verify calibration, and when to recheck instrument cleanliness.
What changed in EN ISO 20846:2026 from the previous edition?
EN ISO 20846:2026 supersedes EN ISO 20846:2019 and is technically revised. The changes stated in the document are:
- the scope has been extended to include higher blends of biodiesel (FAME) from 50 % up to neat FAME (B100);
- additional instructions have been added for the validity of multi-point calibration.
Which standards are used with EN ISO 20846:2026?
EN ISO 20846:2026 cites several standards that support sampling, preparation, density measurement, precision work, and reference materials.
- ISO 1042 - defines Class A one-mark volumetric flasks used to prepare stock solutions and calibration standards.
- ISO 3170 - gives manual sampling procedures for hydrocarbon liquids.
- ISO 3171 - gives automatic pipeline sampling procedures for petroleum liquids.
- ISO 3675 - provides the hydrometer method for density determination.
- ISO 12185 - provides laboratory density-meter measurement with an oscillating U-tube sensor.
- ISO 91 - supports temperature correction of density when the injection temperature differs from the density determination temperature.
- ISO 17034 - is used as the competence reference for certified reference materials.
- ISO 4259:2006, ISO 4259-1:2017, ISO 4259-1:2017/Amd 1:2019, and ISO 4259-1:2017/Amd 2:2020 - are cited for precision data and statistical treatment of sulfur test results.
What does the EN ISO 20846:2026 document contain?
EN ISO 20846:2026 contains a detailed test method, not just a result limit. Clause 5 gives reagent preparation and stock-solution preparation, including examples of sulfur compounds and calibration materials. Clause 6 includes the apparatus synopsis and the key instrument parts needed for combustion and UV fluorescence detection.
Clause 9 gives the calibration routines, including multi-point and single-point approaches, blank handling, and verification with quality control samples. Clauses 10 and 11 give the operating procedure and the calculation steps, including dilution correction and validation of the calibration intercept. Clause 13 presents repeatability, reproducibility, and worked precision estimates in tables, while Clause 14 lists the items that must appear in the test report.
Relations
- Effective Date
- 26-Jul-2023
- Effective Date
- 02-Sep-2026
- Effective Date
- 02-Sep-2026
- Effective Date
- 02-Sep-2026
- Effective Date
- 02-Sep-2026
- Effective Date
- 02-Sep-2026
- Effective Date
- 05-Aug-2026
- Effective Date
- 05-Aug-2026
- Effective Date
- 05-Aug-2026
- Referred By
EN 16900:2017 - Fast pyrolysis bio-oils for industrial boilers - Requirements and test methods - Effective Date
- 05-Aug-2026
- Consolidated By
ISO 20846:2026 - Petroleum and related products — Determination of sulfur content of automotive fuels — Ultraviolet fluorescence method - Effective Date
- 12-Feb-2026
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Frequently Asked Questions
EN ISO 20846:2026 is a standard published by the European Committee for Standardization (CEN). Its full title is "Petroleum and related products - Determination of sulfur content of automotive fuels - Ultraviolet fluorescence method (ISO 20846:2026)". This standard covers: This document specifies an ultraviolet (UV) fluorescence test method for the determination of the sulfur content of the following products: having sulfur contents in the range 3 mg/kg to 500 mg/kg: motor gasolines containing up to a mass fraction of 3,7 % (3,7 % (m/m)) of oxygen [including those blended with a volume fraction of ethanol up to about 10 % (10 % (V/V))]; diesel fuels, including those containing up to a volume fraction of about 50 % of fatty acid methyl ester (FAME); having sulfur contents in the range of 3 mg/kg to 45 mg/kg: synthetic fuels, such as hydrotreated vegetable oil (HVO) and gas to liquid (GTL); having sulfur contents in the range of 3 mg/kg to 30 mg/kg: neat FAME (B100) and diesel fuels containing volume fraction of more than 50 % of FAME. Other products (for example process feeds and effluents) can be analysed and other sulfur contents can be determined according to this test method, however, no precision data for products other than automotive fuels and for results outside the specified range have been established for this document. Halogens interfere with this detection technique at concentrations above approximately 3 500 mg/kg.
This document specifies an ultraviolet (UV) fluorescence test method for the determination of the sulfur content of the following products: having sulfur contents in the range 3 mg/kg to 500 mg/kg: motor gasolines containing up to a mass fraction of 3,7 % (3,7 % (m/m)) of oxygen [including those blended with a volume fraction of ethanol up to about 10 % (10 % (V/V))]; diesel fuels, including those containing up to a volume fraction of about 50 % of fatty acid methyl ester (FAME); having sulfur contents in the range of 3 mg/kg to 45 mg/kg: synthetic fuels, such as hydrotreated vegetable oil (HVO) and gas to liquid (GTL); having sulfur contents in the range of 3 mg/kg to 30 mg/kg: neat FAME (B100) and diesel fuels containing volume fraction of more than 50 % of FAME. Other products (for example process feeds and effluents) can be analysed and other sulfur contents can be determined according to this test method, however, no precision data for products other than automotive fuels and for results outside the specified range have been established for this document. Halogens interfere with this detection technique at concentrations above approximately 3 500 mg/kg.
EN ISO 20846:2026 is classified under the following ICS (International Classification for Standards) categories: 75.160.20 - Liquid fuels; 75.160.30 - Gaseous fuels. The ICS classification helps identify the subject area and facilitates finding related standards.
EN ISO 20846:2026 has the following relationships with other standards: It is inter standard links to EN ISO 20846:2019, ISO 3675:1998, ISO 1042:1998, ISO 3170:2025, ISO 12185:2024, ISO 3171:1988, CEN/TR 17103:2017, CEN/TS 15940:2012, CEN/TS 18227:2025, EN 16900:2017, ISO 20846:2026. Understanding these relationships helps ensure you are using the most current and applicable version of the standard.
EN ISO 20846:2026 is available in PDF format for immediate download after purchase. The document can be added to your cart and obtained through the secure checkout process. Digital delivery ensures instant access to the complete standard document.
Standards Content (Sample)
SLOVENSKI STANDARD
01-september-2026
Nadomešča:
SIST EN ISO 20846:2019
Naftni in sorodni proizvodi - Določanje žvepla v gorivih za motorna vozila -
Ultravijolična fluorescenčna metoda (ISO 20846:2026)
Petroleum and related products - Determination of sulfur content of automotive fuels -
Ultraviolet fluorescence method (ISO 20846:2026)
Mineralölerzeugnisse - Bestimmung des Schwefelgehaltes von Kraftstoffen -
Ultraviolettfluoreszenz-Verfahren (ISO 20846:2026)
Produits pétroliers et connexes - Détermination de la teneur en soufre des carburants
pour automobiles - Méthode par fluorescence ultraviolette (ISO 20846:2026)
Ta slovenski standard je istoveten z: EN ISO 20846:2026
ICS:
75.160.20 Tekoča goriva Liquid fuels
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
EN ISO 20846
EUROPEAN STANDARD
NORME EUROPÉENNE
July 2026
EUROPÄISCHE NORM
ICS 75.160.20; 75.160.30 Supersedes EN ISO 20846:2019
English Version
Petroleum and related products - Determination of sulfur
content of automotive fuels - Ultraviolet fluorescence
method (ISO 20846:2026)
Produits pétroliers et connexes - Détermination de la Mineralölerzeugnisse - Bestimmung des
teneur en soufre des carburants pour automobiles - Schwefelgehaltes von Kraftstoffen -
Méthode par fluorescence ultraviolette (ISO Ultraviolettfluoreszenz-Verfahren (ISO 20846:2026)
20846:2026)
This European Standard was approved by CEN on 1 July 2026.
CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this
European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references
concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN
member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by
translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management
Centre has the same status as the official versions.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and
United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2026 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 20846:2026 E
worldwide for CEN national Members.
Contents Page
European foreword . 3
European foreword
This document (EN ISO 20846:2026) has been prepared by Technical Committee ISO/TC 28 "Petroleum
and related products, fuels and lubricants from natural or synthetic sources" in collaboration with
Technical Committee CEN/TC 19 “Gaseous and liquid fuels, lubricants and related products of
petroleum, synthetic and biological origin” the secretariat of which is held by NEN.
This European Standard shall be given the status of a national standard, either by publication of an
identical text or by endorsement, at the latest by January 2027, and conflicting national standards shall
be withdrawn at the latest by January 2027.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
This document supersedes EN ISO 20846:2019.
Any feedback and questions on this document should be directed to the users’ national standards
body/national committee. A complete listing of these bodies can be found on the CEN website.
According to the CEN-CENELEC Internal Regulations, the national standards organizations of the
following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria,
Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland,
Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of
North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and the
United Kingdom.
Endorsement notice
The text of ISO 20846:2026 has been approved by CEN as EN ISO 20846:2026 without any modification.
International
Standard
ISO 20846
Fourth edition
Petroleum and related products —
2026-07
Determination of sulfur content
of automotive fuels — Ultraviolet
fluorescence method
Produits pétroliers et connexes — Détermination de la teneur
en soufre des carburants pour automobiles — Méthode par
fluorescence ultraviolette
Reference number
ISO 20846:2026(en) © ISO 2026
ISO 20846:2026(en)
© ISO 2026
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
or ISO’s member body in the country of the requester.
ISO copyright office
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CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii
ISO 20846:2026(en)
Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 2
4 Principle . 2
5 Reagents and materials . 2
5.1 Inert gas .2
5.2 Oxygen .2
5.3 Solvent .2
5.4 Sulfur compounds .2
5.5 Sulfur stock solution . .3
5.6 Calibration standards .3
5.7 Quality control samples .3
5.8 Quartz wool .4
6 Apparatus . 4
7 Sampling and sample handling . 5
8 Apparatus preparation . 5
9 Apparatus calibration and verification . 6
9.1 Multi-point calibration .6
9.2 Single point calibration .8
9.3 Verification . .8
10 Procedure . 9
11 Calculation . 9
11.1 Using multi-point calibration.9
11.2 Using one-point calibration .10
11.3 Calculation .10
12 Expression of results .11
13 Precision .11
13.1 General .11
13.2 Repeatability, r.11
13.3 Reproducibility, R .11
13.4 Precision estimates . 12
14 Test report .12
Bibliography .13
iii
ISO 20846:2026(en)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out through
ISO technical committees. Each member body interested in a subject for which a technical committee
has been established has the right to be represented on that committee. International organizations,
governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely
with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types
of ISO document should be noted. This document was drafted in accordance with the editorial rules of the
ISO/IEC Directives, Part 2 (see www.iso.org/directives).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions
related to conformity assessment, as well as information about ISO's adherence to the World Trade
Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 28, Petroleum and related products, fuels and
lubricants from natural or synthetic sources, in collaboration with the European Committee for Standardization
(CEN) Technical Committee CEN/TC 19, Gaseous and liquid fuels, lubricants and related products of petroleum,
synthetic and biological origin, in accordance with the Agreement on technical cooperation between ISO and
CEN (Vienna Agreement).
This fourth edition cancels and replaces the third edition (ISO 20846:2019), which has been technically
revised.
The main changes are as follows:
— the extension of the application scope to include higher blends of biodiesel (FAME) from 50 % up to neat
FAME (B100);
— further instructions regarding the (validity of the) multi-point calibration have been implemented.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.
iv
International Standard ISO 20846:2026(en)
Petroleum and related products — Determination of sulfur
content of automotive fuels — Ultraviolet fluorescence
method
WARNING — The use of this document can involve hazardous materials, operations and equipment.
This document does not purport to address all of the safety problems associated with its use. It is
the responsibility of users of this document to take appropriate measures to ensure the safety and
health of personnel prior to application of the document and fulfil other applicable requirements for
this purpose.
1 Scope
This document specifies an ultraviolet (UV) fluorescence test method for the determination of the sulfur
content of the following products:
— having sulfur contents in the range 3 mg/kg to 500 mg/kg:
— motor gasolines containing up to a mass fraction of 3,7 % (3,7 % (m/m)) of oxygen [including those
blended with a volume fraction of ethanol up to about 10 % (10 % (V/V))];
— diesel fuels, including those containing up to a volume fraction of about 50 % of fatty acid methyl
ester (FAME);
— having sulfur contents in the range of 3 mg/kg to 45 mg/kg:
— synthetic fuels, such as hydrotreated vegetable oil (HVO) and gas to liquid (GTL);
— having sulfur contents in the range of 3 mg/kg to 30 mg/kg:
— neat FAME (B100) and diesel fuels containing volume fraction of more than 50 % of FAME.
Other products (for example process feeds and effluents) can be analysed and other sulfur contents can be
determined according to this test method, however, no precision data for products other than automotive
fuels and for results outside the specified range have been established for this document. Halogens interfere
with this detection technique at concentrations above approximately 3 500 mg/kg.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes
requirements of this document. For dated references, only the edition cited applies. For undated references,
the latest edition of the referenced document (including any amendments) applies.
ISO 1042, Laboratory glassware — One-mark volumetric flasks
ISO 3170, Hydrocarbon Liquids — Manual sampling
ISO 3171, Petroleum liquids — Automatic pipeline sampling
ISO 3675, Crude petroleum and liquid petroleum products — Laboratory determination of density — Hydrometer
method
ISO 12185, Crude petroleum, petroleum products and related products — Determination of density —
Laboratory density meter with an oscillating U-tube sensor
ISO 20846:2026(en)
3 Terms and definitions
No terms and definitions are listed in this document.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
4 Principle
A hydrocarbon sample is either directly injected or placed in a sample boat. Then, it enters a high temperature
combustion tube (1 000 °C to 1 100 °C), where the sulfur is oxidized to sulfur dioxide (SO ) in an oxygen-rich
atmosphere. Water produced during the sample combustion is removed and the sample combustion gases
are exposed to UV light. The SO absorbs the energy from the UV light and is converted to excited sulfur
dioxide (SO *). The fluorescence emitted from the excited SO * as it returns to a stable state SO is detected
2 2 2
by a photomultiplier tube and the resulting signal is a measure of the sulfur contained in the sample.
5 Reagents and materials
5.1 Inert gas
Use argon or helium, high purity grade with a minimum purity of 99,998 % by volume.
5.2 Oxygen
Use high purity grade with a minimum purity of 99,75 % by volume.
WARNING — Oxygen vigorously accelerates combustion.
5.3 Solvent
Use either that specified in a) or b), or a solvent similar to that occurring in the sample under analysis.
Correction for sulfur contribution from solvents used in standard preparation and sample dilution is
required. Alternatively, a solvent with non-detectable sulfur contamination relative to the unknown sample
can be used, making the blank correction unnecessary.
NOTE Non-detectable is in general considered to be below 0,5 mg/kg for regular samples, though solvents
with < 0,05 mg/kg of sulfur are readily available.
a) Toluene, reagent grade.
b) Isooctane, reagent grade.
WARNING — Flammable solvents.
5.4 Sulfur compounds
Compounds with a minimum purity of 99 % by mass shall be used. Examples are given in a) to d). Where the
purity of these compounds is less than 99 % by mass, the concentrations and nature of all impurities shall be
established.
NOTE 1 A correction for chemical impurity can be applied when the sulfur content is known with accuracy.
[3]
NOTE 2 Certified reference materials (CRM) produced in accordance with ISO 17034 are suitable alternatives to
the compounds listed in a) to d).
ISO 20846:2026(en)
a) Dibenzothiophene (DBT), of molar mass 184,26 g/mol, with a nominal sulfur content of 17,399 % mass
fraction.
b) Dibutyl sulfide (DBS), of molar mass 146,29 g/mol, with a nominal sulfur content of 21,915 % mass
fraction.
c) Dibutyl disulfide (DBDS), of molar mass 178,36 g/mol, with a nominal sulfur content of 35,950 % mass
fraction.
d) Thionaphthene (benzothiophene) (TNA), of molar mass 134,20 g/mol, with a nominal sulfur content of
23,890 % mass fraction.
5.5 Sulfur stock solution
Prepare a stock solution of approximately 1 000 mg/l sulfur content by accurately weighing the appropriate
quantity of sulfur compound (5.4) in a volumetric flask (6.9). Ensure complete dissolution with solvent (5.3).
Calculate the exact sulfur concentration of the stock solution to the nearest 1 mg/l. This stock solution is
used for the preparation of calibration standards. As an alternative procedure, a sulfur stock solution of
approximately 1 000 mg/kg can be prepared by accurately weighing the appropriate quantity of sulfur
compound (5.4) in a volumetric flask (6.9) and reweighing the volumetric flask once it has been filled to the
mark with the solvent (5.3). Take precautions to ensure that evaporation of either the solvent or the sulfur
compounds, or both, are not causing weighing errors.
The appropriate mass of sulfur compound described in 5.4 a) to d) that shall be added to the 100 ml flask is:
— 0,574 8 g (DBT),
— 0,456 3 g (DBS),
— 0,278 1 g (DBDS),
— 0,418 6 g (TNA).
NOTE The shelf life of the stock solution is approximately three months when stored at low temperature, typically
in a refrigerator.
5.6 Calibration standards
Prepare the calibration standards by dilution of the stock solution (5.5) with the selected solvent (5.3).
Calculate the exact sulfur content of each calibration standard.
Calibration standards with a known
...