ISO/FDIS 21846

Vegetable fats and oils — Determination of composition of triacylglycerols and composition and content of diacylglycerols by capillary gas chromatography

This document specifies the determination of composition of triacylglycerols and the determination of the composition and content of diacylglycerols by capillary gas chromatography in vegetable oils with a lauric acid content below 1 %. Applying certain technological processing 1,2-diacylglycerols (1,2-DAGs) are transformed to the more stable isomeric 1,3-diacylglycerols (1,3-DAGs) due to acidic catalysed reaction. During storage, the speed and amount of this rearrangement depends on the acidity of the oil. The transformation normally reaches an equilibrium between the two isomeric forms. The relative amount of 1,2-DAGs is related to oil freshness or to a possible technological treatment. Therefore, it is possible to use the ratio of 1,2-DAGs to 1,3-DAGs as a quality criterion for vegetable fats and oils. The triacylglycerols profile is of potential interest for the fingerprint of each vegetable oil and may help the detection of certain types of adulteration, such as the addition of high oleic sunflower oil or palm olein in olive oil. NOTE This document is based on Reference [3].

Corps gras d'origine végétale — Détermination de la composition des triacylglycérols et de la teneur en diacylglycérols par chromatographie en phase gazeuse sur colonne capillaire, dans les huiles végétales

General Information

• Status: Not Published
• ICS: 67.200.10 - Animal and vegetable fats and oils
• Technical Committee: ISO/TC 34/SC 11 - Animal and vegetable fats and oils
• Drafting Committee: ISO/TC 34/SC 11 - Animal and vegetable fats and oils
• Current Stage: 5020 - FDIS ballot initiated: 2 months. Proof sent to secretariat
• Start Date: 07-Aug-2025
• Completion Date: 07-Aug-2025

Relations

• Revises: ISO 21846:2018 - Vegetable fats and oils — Determination of composition of triacylglycerols and composition and content of diacylglycerols by capillary gas chromatography
• Effective Date: 25-Jan-2025

Standards Content (Sample)

FINAL DRAFT
International
Standard
ISO/TC 34/SC 11
Vegetable fats and oils —
Secretariat: BSI
Determination of composition of
Voting begins on:
triacylglycerols and composition
and content of diacylglycerols by
Voting terminates on:
capillary gas chromatography
Corps gras d'origine végétale — Détermination de la composition
des triacylglycérols et de la teneur en diacylglycérols par
chromatographie en phase gazeuse sur colonne capillaire, dans
les huiles végétales
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 SUPPOR TING DOCUMENTATION.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO­
LOGICAL, COMMERCIAL AND USER PURPOSES, DRAFT
INTERNATIONAL STANDARDS MAY ON OCCASION HAVE
TO BE CONSIDERED IN THE LIGHT OF THEIR POTENTIAL
TO BECOME STAN DARDS TO WHICH REFERENCE MAY BE
MADE IN NATIONAL REGULATIONS.
Reference number
FINAL DRAFT
International
Standard
ISO/TC 34/SC 11
Vegetable fats and oils —
Secretariat: BSI
Determination of composition of
Voting begins on:
triacylglycerols and composition
and content of diacylglycerols by
Voting terminates on:
capillary gas chromatography
Corps gras d'origine végétale — Détermination de la composition
des triacylglycérols et de la teneur en diacylglycérols par
chromatographie en phase gazeuse sur colonne capillaire, dans
les huiles végétales
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 SUPPOR TING DOCUMENTATION.
© ISO 2025
IN ADDITION TO THEIR EVALUATION AS
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO­
LOGICAL, COMMERCIAL AND USER PURPOSES, DRAFT
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
INTERNATIONAL STANDARDS MAY ON OCCASION HAVE
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
TO BE CONSIDERED IN THE LIGHT OF THEIR POTENTIAL
or ISO’s member body in the country of the requester.
TO BECOME STAN DARDS TO WHICH REFERENCE MAY BE
MADE IN NATIONAL REGULATIONS.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland Reference number
ii
Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 1
5 Apparatus . 2
6 Reagents . 2
7 Procedure . 3
7.1 Gas chromatographic apparatus and capillary column condition .3
7.2 Choice of operating conditions .3
7.3 Performance of the analysis .3
7.4 Peak identification .3
7.5 Determination of percentage content of each triacylglycerol class .4
7.6 Determination of percentage content of each 1,2 diacylglycerol .4
7.7 Determination of weight percentage total content of diacylglycerols .4
8 Expression of results . 4
9 Precision of the method . 5
9.1 Repeatability, r.5
9.2 Reproducibility, R .5
10 Test report . 5
Annex A (informative) Examples of a typical chromatograms . 6
Annex B (informative) Results of an interlaboratory test .11
Bibliography .13

iii
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 34, Food products, Subcommittee SC 11, Animal
and vegetable fats and oils.
This second edition cancels and replaces the first edition (ISO 21846:2018), of which it constitutes a minor
revision.
The changes are as follows:
— entry errors have been corrected in Tables B.1, B.2, B.3, B.4 and B.5.
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
FINAL DRAFT International Standard ISO/FDIS 21846:2025(en)
Vegetable fats and oils — Determination of composition
of triacylglycerols and composition and content of
diacylglycerols by capillary gas chromatography
1 Scope
This document specifies the determination of composition of triacylglycerols and the determination of the
composition and content of diacylglycerols by capillary gas chromatography in vegetable oils with a lauric
acid content below 1 %.
Applying certain technological processing 1,2-diacylglycerols (1,2-DAGs) are transformed to the more stable
isomeric 1,3-diacylglycerols (1,3-DAGs) due to acidic catalysed reaction. During storage, the speed and
amount of this rearrangement depends on the acidity of the oil. The transformation normally reaches an
equilibrium between the two isomeric forms. The relative amount of 1,2-DAGs is related to oil freshness or
to a possible technological treatment. Therefore, it is possible to use the ratio of 1,2-DAGs to 1,3-DAGs as a
quality criterion for vegetable fats and oils.
The triacylglycerols profile is of potential interest for the fingerprint of each vegetable oil and may help the
detection of certain types of adulteration, such as the addition of high oleic sunflower oil or palm olein in
olive oil.
NOTE This document is based on Reference [3].
2 Normative references
There are no normative references in this document.
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
After the addition of an internal standard the oil sample is silylated, dissolved in a suitable reagent and
directly injected in the gas chromatographic apparatus. Triacyglycerols are separated into classes on the
basis of their carbon atom number, while diacylglycerols are separated in function of their carbon atom
number and structure, as 1,2 structures show a lower retention time than 1,3 ones.
Unsaturated diacylglycerol structures do not affect retention time. Therefore, saturated and unsaturated
diacylglycerols elute together, so 1,2 and 1,3-diacylglycerol structures are identified by their peak retention
time. The percentage content of 1,2 structure is determined through the ratio of 1,2-diacylglycerol areas to
the sum of areas of all the diacylglycerol peaks.
The diacylglycerol total content is calculated by means of an internal standard.

The percentage content for each triacylglycerol class is calculated after normalization to 100 % of all the
triacylglycerol peaks.
5 Apparatus
5.1 Analytical balance suitable to perform weighing to an accuracy of within +/−0,1 mg.
5.2 Gas chromatograph for use with a capillary column, equipped with a system for direct on-column for
cold injection or a programmed temperature vaporizer.
5.3 Thermostat-controlled oven with temperature programming.
5.4 Cold injector for on-column injection or programmed temperature vaporizer.
5.5 Flame-ionization detector and converter-amplifier.
5.6 Recorder-integrator for use with the converter-amplifier (5.5), with a rate of response below 1 s and
variable paper speed, or any suitable device for data capture and handling.
5.7 Capillary column, fused silica, 6 m to 8 m length, 0,25 mm to 0,32 mm internal diameter, internally
coated with SE 52, SE 54 liquid phase to a uniform thickness of 0,10 μm to 0,15 μm.
5.8 Microsyringe, 10 μl, with a hardened needle for on-column injector.
5.9 Microsyringe, 100 μl, with a hardened needle.
5.10 Usual laboratory glassware.
6 Reagents
WARNING — Attention is drawn to the regulations which specify the handling of hazardous
substances. Technical, organizational and personal safety measures shall be followed.
Unless otherwise stated analytically pure reagents shall be used.
6.1 Carrier gas: hydrogen or helium, pure, for gas chromatography.
6.2 Auxiliary gases:
— hydrogen, pure, for gas chromatography;
— air, pure, for gas chromatography.
6.3 Silylating reagent, mix equal volumes of
— pyridine, and
— bistrimethylsilylfluoroacetamide (BSTFA)-trimethylchlorosilane (TMCS), 99:1, volume fraction.
6.4 n-Heptane.
6.5 Reference
...

ISO/TC 34/SC 11
Date: 2025-07
ISO 21846:xxxx(E)
ISO TC 34/SC 11
Secretariat: BSI
Date:
Vegetable fats and oils — Determination of composition of
triacylglycerols and composition and content of diacylglycerols by
capillary gas chromatography
Corps gras d'origine végétale — Détermination de la composition des triacylglycérols et de la teneur en
diacylglycérols par chromatographie en phase gazeuse sur colonne capillaire, dans les huiles végétales
FDIS stage
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
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: + 41 22 749 01 11
E-mail: [e-mail]
Website: www.iso.org
Published in Switzerland
ii
Contents
Foreword . iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 1
5 Apparatus . 2
6 Reagents . 2
7 Procedure . 3
7.1 Gas chromatographic apparatus and capillary column condition . 3
7.2 Choice of operating conditions . 3
7.3 Performance of the analysis . 3
7.4 Peak identification . 3
7.5 Determination of percentage content of each triacylglycerol class . 4
7.6 Determination of percentage content of each 1,2 diacylglycerol . 4
7.7 Determination of weight percentage total content of diacylglycerols . 4
8 Expression of results . 4
9 Precision of the method . 5
9.1 Repeatability, r . 5
9.2 Reproducibility, R . 5
10 Test report . 5
Annex A (informative) Examples of a typical chromatograms . 6
Annex B (informative) Results of an interlaboratory test . 11
Bibliography . 14

iii
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 documentsdocument 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).
Attention is drawnISO draws attention to the possibility that some of the elementsimplementation of this
document may beinvolve the subjectuse 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. Details of any patent rights identified during the development of the
document will be in the Introduction and/or on the ISO list of patent declarations received (see ).
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 34, Food products, Subcommittee SC 11, Animal
and vegetable fats and oils.
This second edition is a minor revision, which corrects entry errors in Tables B.1, B.2, B.3, B.4 and B.5., and
cancels and replaces the first edition (ISO 21846:2018).), of which it constitutes a minor revision.
The changes are as follows:
— entry errors have been corrected in Tables B.1, B.2, B.3, B.4 and B.5.
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
Vegetable fats and oils — Determination of composition of
triacylglycerols and composition and content of diacylglycerols by
capillary gas chromatography
1 Scope
This document specifies the determination of composition of triacylglycerols and the determination of the
composition and content of diacylglycerols by capillary gas chromatography in vegetable oils with a lauric acid
content below 1 %.
Applying certain technological processing 1,2-diacylglycerols (1,2-DAGs) are transformed to the more stable
isomeric 1,3-diacylglycerols (1,3-DAGs) due to acidic catalysed reaction. During storage, the speed and
amount of this rearrangement depends on the acidity of the oil. The transformation normally reaches an
equilibrium between the two isomeric forms. The relative amount of 1,2-DAGs is related to oil freshness or to
a possible technological treatment. Therefore, it is possible to use the ratio of 1,2-DAGs to 1,3-DAGs as a quality
criterion for vegetable fats and oils.
The triacylglycerols profile is of potential interest for the fingerprint of each vegetable oil and may help the
detection of certain types of adulteration, such as the addition of high oleic sunflower oil or palm olein in olive
oil.
NOTE This document is based on Reference [3].
2 Normative references
There are no normative references in this document.
3 Terms and definitions
No terms and definitions are listed in this document.
ISO and IEC maintain terminologicalterminology 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
After the addition of an internal standard the oil sample is silylated, dissolved in a suitable reagent and directly
injected in the gas chromatographic apparatus. Triacyglycerols are separated into classes on the basis of their
carbon atom number, while diacylglycerols are separated in function of their carbon atom number and
structure, as 1,2 structures show a lower retention time than 1,3 ones.
Unsaturated diacylglycerol structures do not affect retention time. Therefore, saturated and unsaturated
diacylglycerols elute together, so 1,2 and 1,3-diacylglycerol structures are identified by their peak retention
time. The percentage content of 1,2 structure is determined through the ratio of 1,2-diacylglycerol areas to
the sum of areas of all the diacylglycerol peaks.
The diacylglycerol total content is calculated by means of an internal standard.
The percentage content for each triacylglycerol class is calculated after normalization to 100 % of all the
triacylglycerol peaks.
5 Apparatus
5.1 Analytical balance suitable to perform weighing to an accuracy of within +/−0,1 mg.
5.2 Gas chromatograph for use with a capillary column, equipped with a system for direct on-column for
cold injection or a programmed temperature vaporizer.
5.3 Thermostat-controlled oven with temperature programming.
5.4 Cold injector for on-column injection or programmed temperature vaporizer.
5.5 Flame-ionization detector and converter-amplifier.
5.6 Recorder-integrator for use with the converter-amplifier (5.5), with a rate of response below 1 s and
variable paper speed, or any suitable device for data capture and handling.
5.7 Capillary column, fused silica, 6 m to 8 m length, 0,25 mm to 0,32 mm internal diameter, internally
coated with SE 52, SE 54 liquid phase to a uniform thickness of 0,10 μm to 0,15 μm.
5.8 Microsyringe, 10 μl, with a hardened needle for on-column injector.
5.9 Microsyringe, 100 μl, with a hardened needle.
5.10 Usual laboratory glassware.
6 Reagents
WARNING — Attention is drawn to the regulations which specify the handling of hazardous substances.
Technical, organizational and personal safety measures shall be followed.
Unless otherwise stated analytically pure reagents shall be used.
6.1 Carrier gas: hydrogen or helium, pure, for gas chromatography.
6.2 Auxiliary gases:
— hydrogen, pure, for gas chromatography;
— air, pure, for gas chromatography.
6.3 Silylating reagent, mix equal volumes of
— pyridine, and
— bistrimethylsilylfluoroacetamide (BSTFA)-trimethylchlorosilane (TMCS), 99:1, volume fraction.
6.4 n-Heptane.
6.5 Reference samples: pure diacylglycerols and triacylglycerols and their mixtures, with known
composition.
6.6 Methyl tert-butyl ether.
6.7 Dinonadecanoin sample solution (internal standard), 0,1 % mass/ volume in methyl tert-butyl ether.
7 Procedure
7.1 Gas chromatographic apparatus and capillary column condition
Fit the column to the gas chromatograph (5.2), connecting the inlet port to the on-column system and the
outlet port to the detector. Check the gas chromatography apparatus (operation of gas loops, detector and
recorder efficiency, etc.).
Run a light flow of gas through the column, then switch on the gas chromatography apparatus. Gradually heat
until a temperature of 350 °C is reached after approximately 4 h.
Maintain this temperature for at least 2 h, then regulate the apparatus to the operating conditions (regulate
gas flow, light flame, connect to electronic recorder, regulate oven temperature for column, regulate detector,
etc.). Record the signal at a sensitivity at least twice as high as that required for the analysis. The base line
should be linear, with no peaks of any kind, and shall not have any drift.
Negative straight-line drift indicates that the column connections are not correct. Positive drift indicates that
the column has not been properly conditioned.
7.2 Choice of operating conditions
The operating conditions are generally as follows.
— The injector temperature shall be at least 10 °C below the vaporization temperature (99 °C) of the
employed solvent (n-Heptane).
— Detector temperature: 350 °C.
— Column temperature: 80 °C at first (1 min), ramp at 20 °C/min to 220 °C, ramp at 5 °C/min to 340 °C
(10 min).
— Carrier gas: hydrogen or helium at the optimal linear speed for the chosen gas.
— Amount of injected substance: 0,5 μl to 1 μl of solution prepared as in 7.3.
7.3 Performance of the analysis
Weigh (5.1) exactly 100 mg of oil in a glass bottom conical tube and add 1 ml of internal standard solution
(6.7). Shake the sample up to a complete solution, take up with a microsyringe (5.8) 20 μl to 30 μl of solution,
put it inside a new glass tube (with a stopper) and dry by nitrogen gentle stream. Add 200 μl of silylation
reagent. After 20 min dry by a soft nitrogen flow, add 2 ml of n-Heptane and shake. Inject (5.4) a volume from
0,5 μl to
...