EN 15721:2026

Ethanol as a blending component for petrol - Determination of higher alcohols, methanol and other impurities - Gas chromatographic method

This document specifies a gas chromatographic method for ethanol, in which higher alcohols (propan-1-ol, butan-1-ol, butan-2-ol, 2-methylpropan-1-ol (iso-butanol), 2-methylbutan-1-ol, and 3-methylbutan-1-ol) from (0,1 up to 2,5) mass percentage, methanol from (0,1 up to 3) mass percentage and other impurities, in the range from (0,1 up to 2) mass percentage are determined.
NOTE 1   The European ethanol blending component specification [1] sets a limit for the combined result of ethanol + higher alcohols, not the ethanol content itself.
The method is developed for non-denatured ethanol samples. With sufficient attention to correct separation of the higher alcohols and other components, determination of hydrocarbons in ethanol that contains denaturants as per EN 15376 [1] is possible.
NOTE 2   For the purposes of this document, the term “% (m/m)” is used to represent the mass percentage or mass fraction (ω).

Ethanol zur Verwendung als Blendkomponente in Ottokraftstoff - Bestimmung von höheren Alkoholen, Methanol und andere Verunreinigungen - Gaschromatographisches Verfahren

Dieses Dokument legt ein gaschromatographisches Verfahren für Ethanol fest, mit dem höhere Alkohole [Propan-1-ol, Butan-1-ol, Butan-2-ol, 2-Methylpropan-1-ol (Isobutanol), 2-Methylbutan-1-ol und 3-Methylbutan-1-o] von (0,1 bis 2,5) % Massenanteil, Methanol von (0,1 bis 3) % Massenanteil und andere Verunreinigungen im Konzentrationsbereich von (0,1 bis 2) % Massenanteil bestimmt werden.
ANMERKUNG 1   In der Europäischen Spezifikation [1] für Ethanol zur Verwendung als Blendkomponente ist ein Grenzwert für das kombinierte Ergebnis von Ethanol + höheren Alkoholen festgelegt, nicht für den Ethanolgehalt selbst.
Das Verfahren wurde für Proben von unvergälltem Ethanol entwickelt. Unter ausreichender Beachtung der korrekten Trennung der höheren Alkohole und anderer Bestandteile ist die Bestimmung von Kohlenwasserstoffen in Ethanol, das Vergällungsmittel nach EN 15376 [1] enthält, möglich.
ANMERKUNG 2   Für die Zwecke dieses Dokuments wird zur Angabe des Massenanteils in Prozent oder des Massenanteils (ω) einer Substanz der Ausdruck „% (m/m)“ verwendet.

Éthanol comme base de mélange à l'essence - Détermination de la teneur en alcools supérieurs, méthanol et autres impuretés - Méthode par chromatographie en phase gazeuse

Le présent document spécifie une méthode de chromatographie en phase gazeuse applicable à l'éthanol, pour la détermination de la teneur en alcools supérieurs (propan-1-ol, butan-1-ol, butan-2-ol, 2-méthyl propan-1-ol (isobutanol), 2-méthyl butan-1-ol, et 3-méthyl butan-1-ol) de 0,1 à 2,5 % en pourcentage massique, de la teneur en méthanol de 0,1 % à 3 % en pourcentage massique et de la teneur en autres impuretés de 0,1 % à 2 % en pourcentage massique.
NOTE 1   La norme de spécification européenne de l’éthanol comme base de mélange [1] fixe une exigence sur la teneur combinée éthanol + alcools supérieurs et non sur la teneur en éthanol uniquement.
La méthode a été développée pour les échantillons d'éthanol non-dénaturé. En accordant une attention suffisante à la séparation correcte des alcools supérieurs et des autres composants, il est possible de déterminer les hydrocarbures dans l'éthanol contenant des dénaturants selon l'EN 15376 [1].
NOTE 2   Pour les besoins du présent document, l’expression « % (m/m) » est utilisée pour désigner le pourcentage massique ou la fraction massique (ω).

Etanol kot komponenta za dodajanje motornemu bencinu - Določanje višjih alkoholov, metanola ter drugih nečistoč - Metoda plinske kromatografije

General Information

• Status: Not Published
• Publication Date: 30-Jun-2026
• ICS: 71.080.60 - Alcohols. Ethers
• ICS: 75.160.20 - Liquid fuels
• Technical Committee: CEN/TC 19 - Petroleum products, lubricants and related products
• Drafting Committee: CEN/TC 19/WG 9 - Chromatographic test methods
• Current Stage: 6055 - CEN Ratification completed (DOR) - Publishing
• Start Date: 17-May-2026
• Due Date: 21-Apr-2027
• Completion Date: 17-May-2026
• Ref Project: kSIST FprEN 15721:2026 - Ethanol as a blending component for petrol — Determination of higher alcohols, methanol and other impurities — Gas chromatographic method

Relations

• Revises: EN 15721:2013 - Ethanol as a blending component for petrol - Determination of higher alcohols, methanol and other impurities - Gas chromatographic method
• Effective Date: 19-Mar-2025

Overview

EN 15721:2026 is a European standard developed by CEN that specifies a gas chromatographic method for the determination of higher alcohols, methanol, and other impurities in ethanol intended as a blending component for petrol. This standard is designed to support compliance with European ethanol blending component specifications, particularly EN 15376, by providing procedures to accurately quantify impurities present in ethanol samples. The methodology outlined applies to mass percentages relevant for fuel quality control, ensuring ethanol used in petrol blends meets stringent requirements for purity and performance.

Key Topics

• Scope of Assessment: The standard outlines procedures for quantifying:
  • Higher alcohols (propan-1-ol, butan-1-ol, butan-2-ol, 2-methylpropan-1-ol (iso-butanol), 2-methylbutan-1-ol, 3-methylbutan-1-ol) in the range of 0.1 to 2.5% (m/m)
  • Methanol in the range of 0.1 to 3% (m/m)
  • Impurities (other volatile compounds) in the range of 0.1 to 2% (m/m)
• Sample Applicability: The method is developed for non-denatured ethanol; with suitable separation, it can also be applied to denatured ethanol as per EN 15376.
• Analysis Principle: Utilizes direct injection (Procedure A) or water dilution (Procedure B) of the ethanol sample into a gas chromatograph with a flame ionization detector (FID) to identify and quantify target compounds.
• Precision and Reliability: Validated through multilaboratory studies, both method variants offer reproducible and repeatable results aligned with industry expectations for fuel analysis.

Applications

• Fuel Quality Control: Enables fuel producers, refiners, and analytical laboratories to ensure that ethanol blended into petrol is compliant with European requirements for composition and quality-critical for engine performance, emissions, and regulatory adherence.
• Laboratory Analysis: Provides detailed protocols for sample preparation, calibration, chromatographic separation, and calculation of results to yield accurate quantification of higher alcohols, methanol, and other impurities.
• Support for Regulatory Compliance: The data derived using this method support declarations of ethanol content, higher alcohols, and impurity levels required by EN 15376 and related automotive fuel standards.
• Adaptability: Suitable for continuous quality assurance and research applications in ethanol production and distribution chains, including monitoring during production, storage, blending, and transportation.
• Flexibility in Method Variant Use: Laboratories can select direct injection or dilution based on sample characteristics, potential contamination, or specific analytical needs.

Related Standards

• EN 15376: Automotive fuels - Ethanol as a blending component for petrol - Requirements and test methods. Specifies the quality, specification limits, and test methods for ethanol used in fuel blending.
• EN ISO 3170: Petroleum liquids - Manual sampling. Provides sampling procedures for reliable laboratory analysis.
• EN ISO 3696: Water for analytical laboratory use. Ensures reagent water quality used in preparation and analysis.
• EN ISO 4259: Petroleum products - Determination and application of precision data in relation to methods of test. Supports determination of repeatability and reproducibility for analytical methods.

Practical Value

• Ensures Consistent Fuel Quality: By applying EN 15721:2026, stakeholders in the fuel supply chain can maintain consistent ethanol quality, leading to improved engine compatibility and reduced risk of operational issues.
• Mitigates Impurity Risks: Accurate analysis of higher alcohols and methanol prevents excess impurity levels, which can impact fuel quality and vehicle emissions.
• Contributes to Harmonization: Facilitates uniform testing practices across the European fuel industry, supporting market fairness and legal enforcement of fuel quality standards.
• Supports Industry and Regulatory Needs: Ideal for use within fuel manufacturing, governmental inspection laboratories, and any context where ethanol-based fuel blends are managed or regulated.

For further guidance and technical details, refer to EN 15376 and the accompanying chromatographic methods specified in related international standards. By implementing EN 15721:2026, organizations ensure robust, precise, and trusted assessments of ethanol purity for petrol blending.

Standards Content (Sample)

SLOVENSKI STANDARD
oSIST prEN 15721:2025
01-junij-2025
Etanol kot komponenta za dodajanje motornemu bencinu - Določanje višjih
alkoholov, metanola ter drugih nečistoč - Metoda plinske kromatografije
Ethanol as a blending component for petrol — Determination of higher alcohols,
methanol and other impurities — Gas chromatographic method
Ethanol zur Verwendung als Blendkomponente in Ottokraftstoff - Bestimmung von
höheren Alkoholen, Methanol und andere Verunreinigungen - Gaschromatographisches
Verfahren
Ethanol comme base de mélange à l'essence — Détermination de la teneur des alcools
supérieurs, méthanol et autres impuretés — Méthode par chromatographie en phase
gazeuse
Ta slovenski standard je istoveten z: prEN 15721
ICS:
71.080.60 Alkoholi. Etri Alcohols. Ethers
75.160.20 Tekoča goriva Liquid fuels
oSIST prEN 15721:2025 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

oSIST prEN 15721:2025
oSIST prEN 15721:2025
DRAFT
EUROPEAN STANDARD
prEN 15721
NORME EUROPÉENNE
EUROPÄISCHE NORM
June 2025
ICS 75.160.20; 71.080.60 Will supersede EN 15721:2013
English Version
Ethanol as a blending component for petrol -
Determination of higher alcohols, methanol and other
impurities - Gas chromatographic method
Ethanol comme base de mélange à l'essence - Ethanol zur Verwendung als Blendkomponente in
Détermination de la teneur des alcools supérieurs, Ottokraftstoff - Bestimmung von höheren Alkoholen,
méthanol et autres impuretés - Méthode par Methanol und andere Verunreinigungen -
chromatographie en phase gazeuse Gaschromatographisches Verfahren
This draft European Standard is submitted to CEN members for enquiry. It has been drawn up by the Technical Committee
CEN/TC 19.
If this draft becomes a European Standard, 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.

This draft European Standard was established by CEN 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.
Recipients of this draft are invited to submit, with their comments, notification of any relevant patent rights of which they are
aware and to provide supporting documentation.

Warning : This document is not a European Standard. It is distributed for review and comments. It is subject to change without
notice and shall not be referred to as a European Standard.

EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2025 CEN All rights of exploitation in any form and by any means reserved Ref. No. prEN 15721:2025 E
worldwide for CEN national Members.

oSIST prEN 15721:2025
prEN 15721:2025 (E)
Contents Page
European Foreword . 3
Introduction . 4
1 Scope . 5
2 Normative references . 5
3 Terms and definitions . 5
4 Principle . 5
5 Reagents and materials . 6
6 Apparatus . 6
7 Sampling . 8
8 Procedure. 8
8.1 General . 8
8.2 General considerations for preparation and handling of solutions . 8
8.3 Preparation of solutions for Procedure A . 8
8.3.1 Calibration stock solution (E) for Procedure A . 8
8.3.2 Internal standard stock solution (ES) for Procedure A . 9
8.3.3 Calibration solution (FS1) for Procedure A . 9
8.3.4 Preparation of sample (S) for Procedure A . 9
8.4 Preparation of solutions for Procedure B . 9
8.4.1 Calibration stock solution (E) for Procedure B . 9
8.4.2 Internal standard stock solution (ES) for Procedure B . 10
8.4.3 Calibration solution (FS1) for Procedure B . 10
8.4.4 Preparation of sample (S) for Procedure B . 10
8.5 Determination . 10
8.5.1 Gas chromatograph analysis conditions . 10
8.5.2 Determination of response factors . 11
8.5.3 Recording the chromatogram . 12
8.5.4 Performance checks . 12
9 Calculation . 12
9.1 Content of individual compounds . 12
9.2 Calculation of group contents . 13
9.3 Expression of results . 13
10 Precision . 14
10.1 General . 14
10.2 Repeatability . 14
10.3 Reproducibility . 14
11 Test report . 15
Annex A (informative) Examples of chromatograms . 16
Bibliography . 22
oSIST prEN 15721:2025
prEN 15721:2025 (E)
European Foreword
This document (prEN 15721:2025) has been prepared by 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 document is currently submitted to the CEN Enquiry.
This document will supersede EN 15721:2013.
prEN 15721:2025 included the following significant technical changes with respect to EN 15721:2013.
— the requirement to use self-determined response factors in the calculation (9.1) for all components,
whereas recommendations are given for the commonly used denaturants.
— the need for a good separation, to prevent peak overlap between ethanol and petrol components, is
underlined (8.5.3).
oSIST prEN 15721:2025
prEN 15721:2025 (E)
Introduction
This document specifies a gas chromatographic (GC) test method for the determination of a number of
compounds present in ethanol for use as a blending component in petrol according to the CEN ethanol
blending component specification EN 15376 [1]. The test method comprises of GC identification and
analysis of a number of molecules, which are then attributed to several classes (“impurities”, “methanol”,
“higher alcohols”), which are needed for calculation of the specified values as required in EN 15376.
The method described in this document was prepared by CEN/TC 19’s Working Group 9 and is based on
two methods ([2] and [3]) published from a European Regulation on wine and on other internationally
published analytical methods on spirits [4]. The method is modified for determinations in ethanol for
automotive applications.
oSIST prEN 15721:2025
prEN 15721:2025 (E)
1 Scope
This document specifies a gas chromatographic method for ethanol, in which higher alcohols (propan-1-
ol, butan-1-ol, butan-2-ol, 2-methylpropan-1-ol (iso-butanol), 2-methylbutan-1-ol, and 3-methylbutan-1-
ol) from (0,1 up to 2,5) mass percentage, methanol from (0,1 up to 3) mass percentage and other
impurities, in the range from (0,1 up to 2) mass percentage are determined.
Impurities are all the compounds not attributed to the groups of higher alcohols or methanol.
[1]
NOTE 1 The European ethanol blending component specification sets a limit for the combined result of ethanol
+ higher alcohols, not the ethanol content itself.
The method is developed for non-denatured ethanol samples. With sufficient attention to correct
separation of the higher alcohols and other components, determination of hydrocarbons in ethanol that
contains denaturants as per EN 15376[1] is possible. Water, if present in the sample, is not included in
this analysis, because a signal for water is not visible in the chromatogram. Therefore, if “alcohol content”
is called up in a specification, water needs to be considered separately in the calculations.
NOTE 2 For the purposes of this document, the term “% (m/m)” is used to represent the mass percentage or
mass fraction (ω).
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and are
indispensable for its application. For dated references, only the edition cited applies. For undated
references, the latest edition of the referenced document (including any amendments) applies.
EN ISO 3170, Petroleum liquids — Manual sampling (ISO 3170)
EN ISO 3696, Water for analytical laboratory use — Specification and test methods (ISO 3696)
3 Terms and definitions
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/
No terms and definitions are listed in this document.
4 Principle
The compounds specified in the scope are determined by direct injection of a test portion into a gas
chromatograph (GC) system. An internal standard is added to the sample prior to the injection. The
compounds are separated with suitable GC equipment using temperature programming with the option
to also use flow programming on a suitable column. They are detected using a flame ionization detector
(FID). The concentration of each compound is determined from response factors with respect to the
internal standard.
The response factors are obtained during calibration using the same chromatographic conditions as those
for the analysis of the ethanol samples.
oSIST prEN 15721:2025
prEN 15721:2025 (E)
Two procedures (“Procedure A” and “Procedure B”) are specified which differ mainly in the optional use
of a water dilution step prior to the analysis. Both variants have been validated to produce identical
results and precision in extensive Round Robin tests.
5 Reagents and materials
All reagents shall be of recognized analytical grade (minimum 99 %) or of higher purity, if commercially
available. They shall be stored in closed dark glass bottles and can be used for some long time. Other
internal standards may also be used when there is sufficient proof that their GC signal does not interfere
with the other signals in the chromatogram.
5.1 Water which, for analytical laboratory use, shall conform to grade 2 of EN ISO 3696.
5.2 Compounds
The compounds used for calibration and peak identification are listed in Table 1.
Table 1 — Compounds for calibration, used as solvents and other related information
Compound Attributed to group
Calibration compounds
Methanol Methanol
Propan-1-ol Higher Alcohols
Butan-1-ol Higher Alcohols
Butan-2-ol Higher Alcohols
2-Methylpropan-1-ol Higher Alcohols
2-Methylbutan-1-ol Higher Alcohols
3-Methylbutan-1-ol Higher Alcohols
Internal standards
Pentan-3-ol Internal standard for Procedure A
4-Methylpentan-2-ol Internal standard for Procedure B
Solvent
a
Solvent
Ethanol
a
Ethanol is needed in Procedure “A” and “B” as a solvent for the calibration
solutions. The purity of the ethanol should be considered when preparing the
mixtures. It should not contain any impurities that may interfere with the
analysis and the results shall be corrected for the purity of the ethanol
6 Apparatus
6.1 Gas chromatograph, equipped with a Flame Ionization Detector (FID), a split injector and
connected to a PC or other system permitting the recording of chromatograms and execution of
quantitative calculations.
oSIST prEN 15721:2025
prEN 15721:2025 (E)
6.2 Gas chromatographic column
6.2.1 General
Bonded capillary column with a suited phase, permitting the complete separation of all requested
compounds for the analysis, except for 2-methylbutan-1-ol and 3-methylbutan-1-ol, for which a
minimum peak resolution of 1,0 (see 6.2.2) is required. The internal standard shall be perfectly separated
from all other compounds. Additional detail, including sample chromatograms, is given in Annex A.
6.2.2 Chromatographic resolution
The column resolution (as measured for 2-methylbutan-1-ol and 3-methylbutan-1-ol) shall be at least
1,0. Determine the column resolution, CR, with the calibration solutions (8.3) or (8.4) for the 2-
methylbutan-1-ol and 3-methylbutan-1-ol peaks using the following Formula (1):
2 tt−
( )
2 1
CR= (1)
1,699 W + W
( )
1 2
where
t is the retention time, in seconds, for the 2-methylbutan-1-ol peak;
t is the retention time, in seconds, for the 3-methylbutan-1-ol peak;
W is the width, in seconds, at half-height of 2-methylbutan-1-ol peak;
W is the width, in seconds, at half-height of 3-methylbutan-1-ol peak.
Figure 1 presents further clarification on the calculation of column resolution, CR, of 2-methylbutan-1-ol
and 3-methylbutan-1-ol according to procedure “B” (example: CR = 1,30).

Key
1 Pentan-3-ol (retention time 12,292 min) X retention time (min)
2 2-methylbutan-1-ol (retention time 13,741 min) Y FID signal
3 3-methylbutan-1-ol (retention time 13,820 min)
Figure 1 — Typical chromatogram for calculation of column resolution
oSIST prEN 15721:2025
prEN 15721:2025 (E)
6.3 Analytical balance, capable of weighing to the nearest 0,1 mg.
6.4 Vials, having seals and used for test portions and calibration solutions.
7 Sampling
Unless otherwise specified, laboratory samples shall be obtained by the procedures specified in
EN ISO 3170.
Glass bottles shall be used for taking samples. The glass bottles shall be meticulously cleaned and rinsed
at least twice with the product to be sampled. Special care shall be taken during all further manipulations
with the samples to avoid any risk of further contamination, e.g. with water.
8 Procedure
8.1 General
Two method variants are defined in this document:
a) “Procedure A”, using direct injection of a test portion;
b) “Procedure B”, using injection after one additional preparation step, i.e. dilution of the sample with
water.
Which of the two method variants is used is subject to decision in the laboratory. It may also depend on
a particular request for solution to a specific problem. See the examples of chromatograms in Annex A for
additional detail.
NOTE To prevent the separation of eventually present ethyl acetate due to formation of 1,1-ethoxethane,
Procedure B is preferred.
8.2 General considerations for preparation and handling of solutions
Several precautions shall be observed in the preparation and handling of stock solutions and calibration
solutions to avoid loss of material due to the
...