kSIST FprEN 17403:2026
(Main)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
- 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
- Public Enquiry End Date
- 01-May-2026
- Technical Committee
- KAT - Soil quality
- Current Stage
- 5020 - Formal vote (FV) (Adopted Project)
- Start Date
- 03-Nov-2026
- Due Date
- 22-Dec-2026
kSIST FprEN 17403:2026 is a European standard published through SIST and prepared by CEN/TC 260 for inorganic fertilizers. It specifies how to measure cold water insoluble nitrogen (CWIN) and hot water insoluble nitrogen (HWIN) in solid urea formaldehyde (UF) and methylene urea (MU) slow-release fertilizers, and how to determine the solubility of nutrient polymers in phosphate buffer solution at pH 7,5 and 100 °C. Laboratories use it to report these nitrogen fractions consistently in fertilizer control and product verification.
What does kSIST FprEN 17403:2026 specify?
kSIST FprEN 17403:2026 covers a laboratory method for solid UF/MU fertilizers and for nutrient polymers in inorganic fertilizers in their pure form. It is not applicable to liquid methylene urea.
The document is organized into nine clauses and one informative annex.
| Annex | What it covers |
|---|---|
| Annex A | Results of the inter-laboratory study used for precision data |
Clause 4 covers sampling and sample preparation, Clauses 5 and 6 cover the two nitrogen determinations, Clause 7 covers the solubility calculation for nutrient polymers, Clause 8 covers precision, and Clause 9 covers the test report.
What are the key requirements of kSIST FprEN 17403:2026?
kSIST FprEN 17403:2026 gives a step-by-step analytical method that starts with representative sample preparation, then separates the insoluble nitrogen fractions by extraction, filtration and nitrogen determination in the residue. For a buyer, manufacturer or laboratory, the practical point is that the reported CWIN, HWIN and HWSN values come from a defined extraction time, temperature and calculation route.
Sample preparation
Clause 4 says sampling is outside the method, but the laboratory should receive a representative sample that has not been damaged or changed in transport or storage. Sample preparation follows EN 1482-2, and the laboratory sample is reduced to 100 g, ground, and sieved so that only the fraction retained on the 0,212 mm sieve is used.
This matters because particle size affects extraction and filtration. A poorly prepared sample can shift the measured nitrogen fractions.
CWIN in solid UF/MU
Clause 5 determines CWIN by extracting the test portion at 25 °C for 15 min in phosphate buffer solution at pH 7,5 or in distilled water, then filtering, washing and determining nitrogen in the insoluble residue. Two parallel analyses are required, and a blank test is run at the same time.
The residue nitrogen is determined according to ISO 5315, or by a combustion method. The result is calculated as a mass fraction in percent, and the final determination result is the arithmetic average of the duplicate results.
HWIN in solid UF/MU
Clause 6 determines HWIN by extracting the test portion in phosphate buffer solution at pH 7,5 and 100 °C for 30 min, then filtering, washing and determining nitrogen in the residue. Two parallel analyses are again required, and a blank test is run in parallel.
If filtration takes more than 4 min, the determination is discarded and repeated with Celite as filter-aid. This is a practical control on filtration speed, so the method stays within the intended operating conditions.
Solubility, precision and reporting
Clause 7 calculates HWSN from the HWIN result and the total nitrogen content determined according to EN 15478. In practice, this links the insoluble fraction to the total nitrogen figure already measured by a separate recognized method.
Clause 8 summarizes precision and gives repeatability and reproducibility limits in Table 1 for solid methylene urea and solid urea formaldehyde. Clause 9 requires the test report to identify the sample, state the method used with its year, give the results, note sampling details if known, record when analysis finished, state whether the repeatability limit was met, and list any optional steps or incidents that could have affected the result.
What terms does kSIST FprEN 17403:2026 define?
- UF - urea formaldehyde, a slow-release nitrogenous fertilizer formed by reaction between urea and formaldehyde.
- MU - methylene urea, a slow-release nitrogenous fertilizer containing oligomers such as MDU, DMTU, TMTU and TMPU.
- nutrient polymers - polymer-based component materials used to control nutrient release from one or more monomers.
- virgin material substances and mixtures - component materials made from virgin substances and mixtures, excluding the listed waste-related and animal-derived materials.
- CWIN - the nitrogen fraction insoluble in phosphate buffer solution at pH 7,5 or distilled water at 25 °C during 15 min.
- HWIN - the nitrogen fraction insoluble in phosphate buffer solution at pH 7,5 at 100 °C during 30 min.
- HWSN only - the fraction soluble at 100 °C but not soluble at 25 °C, derived from the HWSN and CWSN relationship.
Who uses kSIST FprEN 17403:2026?
Fertilizer laboratories use this standard to prepare samples, run the extraction steps and calculate reported nitrogen fractions. Manufacturers of solid UF and MU slow-release fertilizers use it for product control and specification checks. Quality managers and buyers use it when comparing products, checking claims about cold and hot water insoluble nitrogen, or reviewing test reports for conformity work.
What changed in kSIST FprEN 17403:2026 from the previous edition?
kSIST FprEN 17403:2026 supersedes CEN/TS 17403:2021. The foreword states these main changes:
- the CEN Technical Specification has been adopted as a European Standard
- Clause 2 normative references and Clause 3 terms and definitions have been updated
- the type of quantitative filter paper is better specified
- use of a combustion method for determining residue nitrogen is considered
- the method for determining total nitrogen is specified
- Clause 8 on precision has been added
- Annex A with inter-laboratory study results has been added
- the bibliography has been updated
Which standards are used with kSIST FprEN 17403:2026?
- EN 1482-1 - recommended sampling method mentioned in Clause 4.
- EN 1482-2 - sample preparation provisions used in Clause 4.
- EN 12944-1 and EN 12944-2 - general fertilizer vocabulary and terms used in Clause 3.
- EN 15478 - total nitrogen determination used for the HWSN calculation in Clause 7.
- ISO 5315 - nitrogen determination in the residue used in Clauses 5 and 6.
- ISO 5725-2 and ISO 5725-3 - repeatability and reproducibility calculations used for the precision study in Clause 8.
- ISO 19670 - source for several definitions used in Clause 3.
What does the kSIST FprEN 17403:2026 document contain?
kSIST FprEN 17403:2026 contains the principle, reagents, apparatus, procedure and calculation for the CWIN and HWIN determinations. It also gives the calculation for nutrient polymer solubility, precision data, and the reporting requirements for laboratory results.
Table 1 gives repeatability and reproducibility limits for the two fertilizer types covered by the precision study. Annex A presents the inter-laboratory study statistics, including the number of laboratories, analytical values, outliers and precision indicators used to support Clause 8.
Relations
- Effective Date
- 01-Dec-2026
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Frequently Asked Questions
kSIST FprEN 17403:2026 is a draft published by the Slovenian Institute for Standardization (SIST). Its full title is "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". This standard covers: 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.
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.
kSIST FprEN 17403:2026 is classified under the following ICS (International Classification for Standards) categories: 65.080 - Fertilizers. The ICS classification helps identify the subject area and facilitates finding related standards.
kSIST FprEN 17403:2026 has the following relationships with other standards: It is inter standard links to SIST-TS CEN/TS 17403:2021. Understanding these relationships helps ensure you are using the most current and applicable version of the standard.
kSIST FprEN 17403:2026 is associated with the following European legislation: EU Directives/Regulations: 2019/1009; Standardization Mandates: M/564, M/564 AMD 1, M/564 AMD 2. When a standard is cited in the Official Journal of the European Union, products manufactured in conformity with it benefit from a presumption of conformity with the essential requirements of the corresponding EU directive or regulation.
kSIST FprEN 17403:2026 is available in PDF format for immediate download after purchase. The document can be added to your cart and obtained through the secure checkout process. Digital delivery ensures instant access to the complete standard document.
Standards Content (Sample)
SLOVENSKI STANDARD
oSIST prEN 17403:2026
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
oSIST prEN 17403:2026 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
oSIST prEN 17403:2026
oSIST prEN 17403:2026
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.
oSIST prEN 17403:2026
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
oSIST prEN 17403:2026
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.
oSIST prEN 17403:2026
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.
oSIST prEN 17403:2026
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
oSIST prEN 17403:2026
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
...