FprEN 17403

• Abstract:

  This document specifies a method for the determination of the cold and hot water insoluble nitrogen content in solid urea formaldehyde and methylene urea slow-release fertilizers and for the determination of the solubility of nutrient polymers in a phosphate buffer solution with a pH of 7,5 at 100 °C, in their pure form in inorganic fertilizers.; This document is not applicable to the following nutrient polymers: liquid methylene urea.

• Status: Not Published
• Publication Date: 03-Feb-2027
• ICS: 65.080 - Fertilizers
• Technical Committee: CEN/TC 260 - Fertilizers and liming materials
• Drafting Committee: CEN/TC 260/WG 7 - Chemical analysis
• Current Stage: 4599 - Dispatch of FV draft to CMC - Finalization for Vote
• Start Date: 12-Aug-2026
• Due Date: 31-Aug-2027
• Completion Date: 12-Aug-2026
• Directive: Harmonized Standard2019/1009 - Regulation (EU) 2019/1009 of the European Parliament and of the Council of 5 June 2019 laying down rules on the making available on the market of EU fertilising products and amending Regulations (EC) No 1069/2009 and (EC) No 1107/2009 and repealing Regulation (EC) No 2003/2003 (Text with EEA relevance)
• Mandate: M/564 - Fertilising products in support of Regulation (EU) 2019/1009
• Mandate: M/564 Amd 1 - amending Implementing Decision C(2020) 612 as regards certain harmonised standards and standardisation deliverables, deadlines for their adoption and the duration of the validity of the standardisation request
• Mandate: M/564 Amd 2 - Commission Implementing decision amending Implementing Decision C(2020)612 as regards harmonised standards, the deadlines for the adoption of those standards and the duration of the validity of the standardisation request to the European Committee for Standardisation as regards the EU fertilising products in support of Regulation (EU) 2019/1009 of the European Parliament and of the Council
• Ref Project: oSIST prEN 17403:2026 - Inorganic fertilizers - Determination of cold water insoluble nitrogen and hot water insoluble nitrogen in solid urea formaldehyde and methylene urea slow-release fertilizers and determination of the solubility of nutrient polymers in phosphate buffer solution with a pH of 7,5 at 100 °C

• Revises: CEN/TS 17403:2021 - Fertilizers - Determination of cold water insoluble nitrogen and hot water insoluble nitrogen in solid urea formaldehyde and methylene urea slow-release fertilizers and determination of the solubility of nutrient polymers in phosphate buffer solution with a pH of 7,5 at 100 °C
• Effective Date: 18-Jan-2023

Overview

FprEN 17403 is a CEN standard that establishes standardized methods for the determination of cold water insoluble nitrogen (CWIN), hot water insoluble nitrogen (HWIN), and the solubility of nutrient polymers in solid urea formaldehyde and methylene urea slow-release inorganic fertilizers. It also specifies the determination of nutrient polymer solubility in a phosphate buffer solution with pH 7.5 at 100 °C. By providing clear procedures for these analyses, this standard supports quality control and regulatory compliance for fertilizer manufacturers, laboratories, and agronomy professionals throughout Europe.

Key Topics

• Cold Water Insoluble Nitrogen (CWIN)
  Refers to nitrogen fractions in solid urea formaldehyde and methylene urea fertilizers that remain insoluble in cold phosphate buffer (or distilled water) at 25 °C. This parameter is a key indicator of the slow-release properties of these fertilizers.

• Hot Water Insoluble Nitrogen (HWIN)
  Indicates the content of nitrogen remaining insoluble after extraction in a phosphate buffer at 100 °C. HWIN is critical for evaluating the length and efficiency of nutrient release.

• Determination Procedures

  • Sample preparation follows EN 1482-2 guidelines.
  • Extraction in phosphate buffer at specified temperature and time.
  • Filtration and measurement of nitrogen in the residue, using titrimetric or combustion-based methods.

• Nutrient Polymer Solubility
  The standard outlines the method for assessing the solubility of nutrient polymers in a phosphate buffer solution at 100 °C, which is essential for evaluating the controlled nutrient release characteristics of such products.

• Precision and Repeatability
  Annex A details results from inter-laboratory studies, ensuring that the methods are repeatable and reproducible across different laboratories.

Applications

• Fertilizer Quality Control
  Ensuring fertilizers meet specified release profiles for effective and environmentally responsible nutrient management.

• Compliance and Certification
  Facilitating compliance with European regulations for fertilizer products, including Regulation (EU) 2019/1009.

• Research and Product Development
  Supporting research laboratories and manufacturers in developing new slow-release fertilizer formulations with validated nutrient release characteristics.

• Regulatory Testing
  Enabling governmental and third-party laboratories to verify fertilizer claims, leading to improved marketplace transparency.

• Environmental Management
  Promoting sustainable agriculture by supporting the use of slow-release fertilizers, which minimize nutrient losses and reduce environmental impact.

Related Standards

• EN 1482-2: Fertilizers, liming materials, and inhibitors – Sampling and sample preparation
• EN 15478: Inorganic fertilizers – Determination of total nitrogen in urea, methylene-urea and urea formaldehyde
• EN 12944-1/2: Fertilizers, liming materials, and inhibitors – Vocabulary
• ISO 5315: Fertilizers – Determination of total nitrogen content – Titrimetric method after distillation
• ISO 5725-2/3: Measurement methods – Repeatability and Reproducibility
• ISO 19670: Solid urea aldehyde slow release fertilizer – General requirements
• Regulation (EU) 2019/1009: Market rules for EU fertilizing products

Practical Value

Adopting FprEN 17403 delivers measurable benefits:

• Ensures consistency in slow-release fertilizer testing.
• Supports traceability and regulatory acceptance of test results.
• Enhances product stewardship by promoting science-based claims for nutrient efficiency.
• Provides harmonized methods that support international trade and product innovation in the fertilizer sector.

This standard is essential for anyone involved in inorganic slow-release fertilizer production, analysis, or regulatory oversight, ensuring reliable, transparent, and reproducible measurement of key nitrogen parameters and nutrient polymer solubility.

SLOVENSKI STANDARD
01-april-2026
Anorganska gnojila - Določanje v hladni in vroči vodi netopnega dušika,
dobljenega s počasnim sproščanjem iz trdnih gnojil in metilenuree, ter določanje
topnosti polimernih hranil v raztopini fosfatnega pufra s pH 7,5 pri 100 °C
Inorganic fertilizers - Determination of cold water insoluble nitrogen and hot water
insoluble nitrogen in solid urea formaldehyde and methylene urea slow-release fertilizers
and determination of the solubility of nutrient polymers in phosphate buffer solution with
a pH of 7,5 at 100 °C
Düngemittel - Bestimmung von kalt- und heißwasserunlöslichem Stickstoff in festen
langsam freisetzenden Harnstoff-Formaldehyd- und Methylenharnstoff-Düngemitteln
sowie Bestimmung der Löslichkeit von Nährstoffpolymeren in Phosphatpufferlösung mit
einem pH-Wert von 7,5 bei 100 °C
Engrais inorganiques - Dosage de l’azote insoluble dans l’eau froide et de l’azote
insoluble dans l’eau chaude dans les engrais à libération lente urée-formaldéhyde et
méthylène-urée solides, et détermination de la solubilité des polymères nutritifs dans une
solution tampon phosphate avec un pH de 7,5 à 100 °C
Ta slovenski standard je istoveten z: prEN 17403
ICS:
65.080 Gnojila Fertilizers
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

DRAFT
EUROPEAN STANDARD
prEN 17403
NORME EUROPÉENNE
EUROPÄISCHE NORM
February 2026
ICS 65.080 Will supersede CEN/TS 17403:2021
English Version
Inorganic fertilizers - Determination of cold water
insoluble nitrogen and hot water insoluble nitrogen in
solid urea formaldehyde and methylene urea slow-release
fertilizers and determination of the solubility of nutrient
polymers in phosphate buffer solution with a pH of 7,5 at
100 °C
Engrais inorganiques - Dosage de l'azote insoluble dans Düngemittel - Bestimmung von kalt- und
l'eau froide et de l'azote insoluble dans l'eau chaude heißwasserunlöslichem Stickstoff in festen langsam
dans les engrais à libération lente urée-formaldéhyde freisetzenden Harnstoff-Formaldehyd- und
et méthylène-urée solides, et détermination de la Methylenharnstoff-Düngemitteln sowie Bestimmung
solubilité des polymères nutritifs dans une solution der Löslichkeit von Nährstoffpolymeren in
tampon phosphate avec un pH de 7,5 à 100 °C Phosphatpufferlösung mit einem pH-Wert von 7,5 bei
100 °C
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 17403:2026 E
worldwide for CEN national Members.

prEN 17403:2026 (E)
Contents Page
European foreword . 3
Introduction . 4
1 Scope . 5
2 Normative references . 5
3 Terms and definitions . 5
4 Sampling and sample preparation . 7
4.1 Sampling . 7
4.2 Sample preparation . 7
5 Determination of the mass fraction of CWIN in solid UF/MU . 7
5.1 Principle . 7
5.2 Reagents . 7
5.3 Apparatus . 7
5.4 Procedure . 8
5.5 Calculation and expression of results . 8
6 Determination of the mass fraction of HWIN in solid UF/MU . 8
6.1 Principle . 8
6.2 Reagents . 8
6.3 Apparatus . 9
6.4 Procedure . 9
6.5 Calculation and expression of results . 9
7 Determination of the solubility of nutrient polymers in phosphate buffer solution
with a pH of 7,5 at 100 °C . 10
8 Precision . 10
8.1 Inter-laboratory study . 10
8.2 Repeatability . 10
8.3 Reproducibility . 10
9 Test report . 10
Annex A (informative) Results of the inter-laboratory study . 12
Bibliography . 15

prEN 17403:2026 (E)
European foreword
This document (prEN 17403:2026) has been prepared by Technical Committee CEN/TC 260 “Fertilizers
and liming materials”, the secretariat of which is held by DIN.
This is currently submitted to CEN Enquiry.
This document will supersede CEN/TS 17403:2021.
prEN 17403:2026 includes the following significant technical changes with respect to
CEN/TS 17403:2021:
a) The CEN Technical Specification has been adopted as a European Standard.
b) Normative references (Clause 2) and Terms and definitions (Clause 3) have been updated.
c) The type of quantitative filter paper has been better specified.
d) The use of the combustion method to determine the residue on the filter has been contemplated.
e) The method for determining total nitrogen has been specified.
f) Clause 8 on precision has been added.
g) Annex A with the results of the inter-laboratory study has been added.
h) The Bibliography has been updated.
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.
prEN 17403:2026 (E)
Introduction
Solid urea formaldehyde and methylene urea slow-release fertilizers are non-coated and chemically
synthesized nitrogen fertilizers with slow-release effect. In 1924, the first slow-release fertilizer patent
in the world was issued to urea formaldehyde (UF) and in 1955, UF was put into commercial production
as the oldest slow-release fertilizer.
WARNING — Users of this document should be familiar with normal laboratory practice. This
document does not purport to address all of the safety issues, if any, associated with its use. It is the
responsibility of the user to establish appropriate health and safety practices and to ensure compliance
with any national regulatory conditions.
IMPORTANT — It is absolutely essential that tests conducted according to this document are carried
out by suitably trained staff.
prEN 17403:2026 (E)
1 Scope
This document specifies a method for the determination of the cold and hot water insoluble nitrogen
content in solid urea formaldehyde and methylene urea slow-release fertilizers and for the
determination of the solubility of nutrient polymers in a phosphate buffer solution with a pH of 7,5 at
100 °C, in their pure form in inorganic fertilizers.
This document is not applicable to the following nutrient polymers: liquid methylene urea.
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 1482-2, Fertilizers, liming materials and inhibitors — Sampling and sample preparation — Part 2:
General sample preparation provisions
EN 12944-1, Fertilizers, liming materials and inhibitors — Vocabulary — Part 1: General terms
EN 12944-2, Fertilizers, liming materials and inhibitors — Vocabulary — Part 2: Terms relating to
fertilizers
EN 15478, Inorganic fertilizers — Determination of total nitrogen in urea, methylene-urea and urea
formaldehyde
ISO 5315, Fertilizers — Determination of total nitrogen content — Titrimetric method after distillation
3 Terms and definitions
For the purposes of this document, the terms and definitions given in EN 12944-1 and EN 12944-2 and
the following 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/
3.1
urea formaldehyde
UF
slow-release nitrogenous fertilizer obtained by the reaction between urea and formaldehyde to produce
molecular chains of general formula NH -CO-NH(CH NHCONH) H
2 2 n
3.2
methylene urea
MU
slow-release nitrogenous fertilizer obtained by the reaction between urea and formaldehyde to produce
oligomers such as MDU (methylendiurea), DMTU (dimethylentriurea), TMTU (trimethylentetraurea),
TMPU (tetramethylenpentaurea) and higher counterparts

A revision is under preparation. Stage at the time of preparation: prEN 12944-1:2026
A revision is under preparation. Stage at the time of preparation: prEN 12944-2:2026
prEN 17403:2026 (E)
3.3
nutrient polymers
component material of fertilizing products consisting of polymers exclusively made up of virgin
material substances and mixtures, where the purpose of the polymerisation is to control the release of
nutrients from one or more of the monomer substances
3.4
virgin material substances and mixtures
component material of fertilizing products consisting of virgin material substances and mixtures
Note 1 to entry: Excluded are the following products: waste and by-products according to [4], materials formerly
having constituted in waste or by-products, animal by-products or derived products and polymers.
3.5
cold water insoluble nitrogen
CWIN
insoluble nitrogen fractions in urea formaldehyde or methylene urea products that are insoluble in
phosphate buffer solution (pH 7,5) or distilled water at 25 °C during a 15 min period
[SOURCE: ISO 19670:2017, 3.2]
3.6
cold water soluble nitrogen
CWSN
...