ISO 13825

FINAL DRAFT
International
Standard
ISO/FDIS 13825
ISO/TC 28
Petroleum and related products —
Secretariat: NEN
Determination of arsenic in
Voting begins on:
crude petroleum using atomic
2025-07-01
fluorescence spectrometry
Voting terminates on:
2025-08-26
Pétrole et produits connexes — Détermination de l'arsenic dans
le pétrole brut par spectrométrie de fluorescence atomique
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MADE IN NATIONAL REGULATIONS.
Reference number
ISO/FDIS 13825:2025(en) © ISO 2025

FINAL DRAFT
ISO/FDIS 13825:2025(en)
International
Standard
ISO/FDIS 13825
ISO/TC 28
Petroleum and related products —
Secretariat: NEN
Determination of arsenic in
Voting begins on:
crude petroleum using atomic
fluorescence spectrometry
Voting terminates on:
Pétrole et produits connexes — Détermination de l'arsenic dans
le pétrole brut par spectrométrie de fluorescence atomique
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
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TO BE CONSIDERED IN THE LIGHT OF THEIR POTENTIAL
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TO BECOME STAN DARDS TO WHICH REFERENCE MAY BE
MADE IN NATIONAL REGULATIONS.
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Published in Switzerland Reference number
ISO/FDIS 13825:2025(en) © ISO 2025

ii
ISO/FDIS 13825:2025(en)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 1
5 Reagents . 1
6 Apparatus . 3
7 Sampling and sample preparation . 4
7.1 Sampling .4
7.2 Mixing samples .4
7.3 Preparation of test solution .4
8 Instrumental set-up . 5
9 Procedure . 5
10 Calculation using the calibration curve . 6
11 Expression of results . 6
12 Precision . 6
12.1 Repeatability, r.6
12.2 Reproducibility, R .6
13 Test report . 6
Annex A (normative) Homogenization of samples . 8
Bibliography . 9

iii
ISO/FDIS 13825:2025(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.
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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.
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
ISO/FDIS 13825:2025(en)
Introduction
Arsenic compounds have a wide range of contents in crude oil. During the refining process, it is easy for the
arsenic compounds to be adsorbed by the catalyst, leading to catalyst poisoning. It has been confirmed that
−9
arsenic compounds of the order of 10 can cause permanent poisoning and deactivation of platinum-based
catalysts for reforming. The presence of arsenic compounds can directly lead to contamination of straight
run fractions of oil products such as naphtha or heavy fraction oil.
The determination of arsenic content plays an important role in guiding the removal of arsenic, determining
the arsenic tolerance of catalysts, and extending the service life of catalysts.
This document provides a method to determine the arsenic content in crude oil. Since arsenic occurs
naturally in organic and inorganic compounds, a closed state is maintained during the digestion process in
order to fully decompose all arsenic containing compounds and avoid losses.

v
FINAL DRAFT International Standard ISO/FDIS 13825:2025(en)
Petroleum and related products — Determination of arsenic
in crude petroleum using atomic fluorescence spectrometry
WARNING — It is absolutely essential that tests conducted according to this document be carried out
by suitably trained staff. This document does not purport to address all of the safety problems, if any,
associated with its use. It is the responsibility of the user to establish appropriate safety and health
practices and to ensure compliance with any national regulatory conditions.
1 Scope
This document specifies a method for the determination of arsenic content in crude oil pretreated by a
closed microwave digestion method by atomic fluorescence spectrometry.
The precision statement of this test method was determined in an interlaboratory study and is valid for
samples with an arsenic content between 0,35 mg/kg and 3,57 mg/kg. The test method can also be applied
to samples with either a higher or lower arsenic content, however, no precision data has been determined at
levels outside of this range.
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 3696, Water for analytical laboratory use — Specification and test methods
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
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 adding acid to the sample and pre-treating it by a closed microwave digestion method, adding
thiourea-ascorbic acid mixed solution to reduce the arsenic (V) to arsenic (III) in the solution, add sodium
tetrahydroborate solution under acidic conditions to convert the arsenic into gaseous arsenic hydrogen. At
the same time, when the hydrogen generated by the reaction of sodium borohydride and acid is brought into
the atomizer by argon, the hydrogen is ignited and forms an argon hydrogen flame, and arsine leads into
the atomizer by means of argon gas flow. The arsenic content in the sample is quantitatively measured by
atomic fluorescence spectrometry.
5 Reagents
It is important to use high purity reagents in all cases. Use only reagents of recognized analytical grade,
unless otherwise specified.
ISO/FDIS 13825:2025(en)
5.1 Water, complying with grade 1 as defined in ISO 3696, for all sample preparation and dilutions.
5.2 Nitric acid,ρ(HNO ) = 1,4 g/ml.
NOTE Nitric acid is available both as ρ(HNO ) = 1,40 g/ml, approximately mass fraction of 65 % and
ρ(HNO ) = 1,42 g/ml, approximately mass fraction of 69 %. Both are suitable.
5.3 Hydrogen peroxide, H O , approximately mass fraction of 30 %.
2 2
5.4 Hydrochloric acid,ρ(HCl) = 1,16 g/ml, approximately mass fraction of 36 %.
5.5 Hydrochloric acid solution (1 + 1), obtained by mixing one volume of hydrochloric acid (5.4) with
one volume of water (5.1).
5.6 Hydrochloric acid solution,ρ(HCl) = 50 ml/l. This solution is obtained by adding 50 ml of hydrochloric
acid (5.4) to 250 ml of water (5.1) and making up a final
...