oSIST prEN 17765:2026

SLOVENSKI STANDARD
01-marec-2026
Organska in organsko-mineralna gnojila - Določanje biureta s tekočinsko
kromatografijo visoke ločljivosti (HPLC)
Organic and organo-mineral fertilizers - Determination of biuret content by high-
performance liquid chromatography (HPLC)
Organische und organisch-mineralische Düngemittel - Bestimmung des Biuretgehalts
mittels Hochleistungs-Flüssigkeitschromatographie (HPLC)
Engrais organiques et organo-minéraux - Détermination de la teneur en biuret par
chromatographie liquide à haute performance (HPLC)
Ta slovenski standard je istoveten z: prEN 17765
ICS:
65.080 Gnojila Fertilizers
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

DRAFT
EUROPEAN STANDARD
NORME EUROPÉENNE
EUROPÄISCHE NORM
January 2026
ICS 65.080 Will supersede CEN/TS 17765:2022
English Version
Organic and organo-mineral fertilizers - Determination of
biuret content by high-performance liquid
chromatography (HPLC)
Engrais organiques et organo-minéraux - Organische und organisch-mineralische Düngemittel -
Détermination de la teneur en biuret par Bestimmung des Biuretgehalts mittels Hochleistungs-
chromatographie liquide à haute performance (HPLC) Flüssigkeitschromatographie (HPLC)
This draft European Standard is submitted to CEN members for enquiry. It has been drawn up by the Technical Committee
CEN/TC 260.
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
© 2026 CEN All rights of exploitation in any form and by any means reserved Ref. No. prEN 17765:2026 E
worldwide for CEN national Members.

Contents Page
European foreword . 3
Introduction . 4
1 Scope . 5
2 Normative references . 5
3 Terms and definitions . 5
4 Principle . 6
5 Reagents . 6
6 Apparatus . 6
7 Procedure . 7
7.1 Sampling . 7
7.2 Calibration solutions . 7
7.3 Preparation of the sample . 8
7.4 Extraction of the sample and preparation of the test solution. 8
7.5 HPLC conditions . 8
7.6 Preparation of the standard curve . 9
7.7 Determination of biuret in the test solutions . 9
8 Calculations . 9
9 Precision . 10
9.1 Inter-laboratory study . 10
9.2 Repeatability . 10
9.3 Reproducibility . 10
10 Test report . 11
Annex A (informative) Results of the interlaboratory study . 12
A.1 Interlaboratory tests . 12
A.2 Statistical results for the determination of biuret . 13
Annex ZA (informative) Relationship between this European Standard and the essential
requirements of Regulation (EU) 2019/1009 making available on the market of EU
fertilising products aimed to be covered . 14
Bibliography . 15

European foreword
This document (prEN 17765:2026) has been prepared by Technical Committee CEN/TC 260 “Fertilizers
and liming materials”, the secretariat of which is held by DIN.
This document is currently submitted to the CEN Enquiry.
This document will supersede CEN/TS 17765:2022.
Compared to the previous edition, prEN 17765:2026 includes the following significant technical changes:
— the CEN Technical Specification has been adopted as a European Standard including the addition of
Annex ZA;
— the Scope (Clause 1) has been updated including a clarification on fertilizing product blends;
— Clause 9 (Precision) and Annex A (Results of the interlaboratory study) have been added.
This document has been prepared under a Standardization Request addressed to CEN by the European
Commission. The Standing Committee of the EFTA States subsequently approves these requests for its
Member States.
For the relationship with EU Legislation, see informative Annex ZA, which is an integral part of this
document.
Introduction
This document defines a test method for the determination of the biuret content to be used for organic
and organo-mineral fertilizers.
When heating urea near or above its melting point (132 °C) during the manufacturing of urea, ammonia
slowly evolves and several different substances, including biuret, are formed. Excessively high
concentrations of biuret can have detrimental effects on plants growth.

1 Scope
This document specifies a method for the determination of the biuret content by high-performance liquid
chromatography (HPLC) with ultraviolet (UV) detector.
This document is applicable to organic and organo-mineral fertilizers containing urea.
This document is applicable to fertilizing products blends where a blend is a mix of at least two of the
following products: fertilizers, liming materials, soil improvers, growing media, inhibitors, plant
biostimulants and where organic matter is present in at least one of the products in the blend. In case a
fertilizing product blend is composed only of inorganic products, the European Standard for inorganic
fertilizers applies. Variations in analytical methods for fertilizing product blends can lead to differing
results as some components or matrix interactions can affect the outcome. Validation procedures have
shown that developed standard methods are robust and reliable across diverse product compositions,
but possible interferences and unexpected results when analysing fertilizing product blends are possible.
NOTE 1 This method was tested only for one fertilizing product blend during the inter-laboratory study. The
product tested was a liquid organo-mineral mixture of a liquid organic fertilizer, a growing medium and a non-
microbial plant biostimulant.
NOTE 2 Nowadays, there is a method standardized as EN 15479 that allows the determination of biuret in urea
by spectrophotometric detection. Organic and organo-mineral fertilizers contain organic matter and other
compounds apart from urea that would interfere in a spectrophotometric method. HPLC allows an accurate
determination of biuret by separating it from possible interfering compounds [2] [5].
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.
EN 12944-1:1999, Fertilizers and liming materials — Vocabulary — Part 1: General terms
EN 12944-2:1999, Fertilizers and liming materials — Vocabulary — Part 2: Terms relating to fertilizers
EN 1482-2:2024, Fertilizers, liming materials and inhibitors — Sampling and sample preparation — Part
2: General sample preparation provisions
prEN 17773:2026, Organic and organo-mineral fertilizers — Determination of the dry matter content
3 Terms and definitions
For the purposes of this document, the terms and definitions given in EN 12944-1:1999 and
EN 12944-2:1999 and the following apply.
ISO and IEC maintain terminological 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/

As impacted by EN 12944-1:1999/AC:2000.
As impacted by EN 12944-2:1999/AC:2000.
Under preparation.
3.1
biuret
imidodicarbonic diamide
member of the class of condensed ureas, formed by the condensation of two molecules of urea
Note 1 to entry: Condensed ureas are the compounds formed by the condensation of two or more molecules of
urea.
4 Principle
The biuret content of the fertilizer sample is extracted with an aqueous acetonitrile solution and
separated by reversed-phase liquid chromatography. Detection of peaks is performed using an UV
detector. Quantification is performed with calibration curve using external standards.
5 Reagents
All reagents shall be of recognized analytical grade.
5.1 Water.
All water shall have a specific conductivity of not more than 0,2 ms/m at 25 °C and shall be free of the
compounds to be detected.
5.2 Acetonitrile, HPLC grade, ≥ 99,9 %.
5.3 Biuret.
The purity of these reagents shall be ≥ 97 %, and the calculation of biuret content within fertilizer should
be based on the purity claimed on the label.
5.4 Eluent, used for HPLC (mobile phase), acetonitrile: water 85 : 15 (volume fraction).
For the preparation of the eluent, the following tasks shall be performed:
a) mix 150 ml water (5.1) with 850 ml acetonitrile (5.2);
b) filter the solution by 0,22 µm membrane filter (6.5) as pretreatment;
c) ultrasonic degas (6.4) for 10 min before used, alternatively an in-line degasser can be used.
5.5 Biuret standard solution (0,5 mg/ml).
For the preparation of the biuret standard solution (0,5 mg/ml), the following tasks shall be performed:
a) weigh approximately 0,50 g to the nearest 0,1 mg of biuret (5.3) and dissolve it by mobile phase (5.4);
b) transfer it into a 1 l volumetric flask;
c) bring to volume with mobile phase (5.4) and mix it thoroughly.
6 Apparatus
6.1 High performance liquid chromatograph, with UV detector.
6.2 Chromatographic column, amino column or amino-propyl column.
6.3 Injection loop.
6.4 Ultrasonic bath.
6.5 Membrane filter, for organic solvents, pore size of 0,22 µm.
6.6 Micro-syringe, with a volume between 5 µl and 50 µl.
The micro-syringe is only necessary in case of using manual injection.
6.7 Syringe-driven filter, syringe with membrane filter for organic solvents (for example
Polytetrafluoroethylene, PTFE), pore size of 0,22 µm.
6.8 Centrifuge.
6.9 Sieve, aperture size of
...