FprEN 17403
(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
- Publication Date
- 03-Feb-2027
- Technical Committee
- CEN/TC 260 - Fertilizers and liming materials
- Drafting Committee
- CEN/TC 260/WG 7 - Chemical analysis
- Current Stage
- 5020 - Submission to Vote - Formal Approval
- Start Date
- 15-Oct-2026
- Due Date
- 09-Nov-2027
- Completion Date
- 15-Oct-2026
FprEN 17403 is a CEN standard for inorganic fertilizers. It specifies laboratory methods to determine cold water insoluble nitrogen and hot water insoluble nitrogen in solid urea formaldehyde (UF) and methylene urea (MU) slow-release fertilizers, and to determine the solubility of nutrient polymers in phosphate buffer solution at pH 7,5 and 100 °C. It is aimed at test laboratories, fertilizer producers, and quality teams that need comparable results for these materials.
What does FprEN 17403 specify?
FprEN 17403 covers one analytical method family for solid UF/MU fertilizers and one calculation for nutrient polymer solubility. The scope applies to the pure form of these materials in inorganic fertilizers and excludes liquid methylene urea.
The document is organized into clauses for scope, references, terms, sampling and sample preparation, the CWIN method, the HWIN method, the nutrient polymer solubility calculation, precision, and the test report.
| Annex | What it covers |
|---|---|
| Annex A | Informative results of the inter-laboratory study |
What are the key requirements of FprEN 17403?
Sampling and sample preparation
FprEN 17403 says sampling is outside the method and points users to EN 1482-1 as a recommended sampling method. It then requires sample preparation according to EN 1482-2. In practice, this means the laboratory must receive a representative sample and prepare it in a controlled way before measuring nitrogen fractions.
The sample is reduced to 100 g for the determinations, ground without warming, and the fraction used for analysis is selected by sieve steps. This matters because overheating or poor size control can change the nitrogen fractions being measured.
CWIN determination
Clause 5 determines cold water insoluble nitrogen (CWIN) by extracting the test portion at 25 °C in phosphate buffer solution, or distilled water, for 15 minutes, then filtering, washing and measuring nitrogen in the residue. Two analyses are run in parallel, and a blank test is made at the same time.
The method uses ISO 5315 for nitrogen measurement in the residue, although a combustion method is also allowed. In practice, the laboratory is comparing the nitrogen left in the insoluble residue with the blank-corrected result to calculate CWIN.
HWIN determination
Clause 6 determines hot water insoluble nitrogen (HWIN) by extracting the test portion in phosphate buffer solution at 100 °C for 30 minutes, then filtering, washing and measuring nitrogen in the residue. Two parallel analyses and a blank test are required here as well.
If filtration takes too long, the determination is discarded and repeated with celite as a filter aid. This makes the method more repeatable in routine work, because slow filtration can distort the result.
Nutrient polymer solubility
Clause 7 calculates hot water soluble nitrogen (HWSN) for nutrient polymers from the total nitrogen result and the HWIN result. The total nitrogen value is taken from EN 15478.
In practice, this clause turns two measured values into the soluble fraction used to describe nutrient polymer behavior at 100 °C in phosphate buffer solution.
Precision and reporting
Clause 8 gives repeatability and reproducibility based on an inter-laboratory study, with the limits listed in Table 1. The study data are in Annex A and were worked out using ISO 5725-2 and ISO 5725-3. Clause 9 then defines what the test report must record, including identification of the sample, the method used, the results, sampling details if known, the completion date, and any incidents or optional steps that could have affected the result.
What terms does FprEN 17403 define?
- UF - urea formaldehyde, a slow-release nitrogenous fertilizer made by reacting urea and formaldehyde.
- MU - methylene urea, a slow-release nitrogenous fertilizer made from urea and formaldehyde oligomers.
- CWIN - cold water insoluble nitrogen, the nitrogen fraction insoluble at 25 °C during a 15 minute period.
- HWIN - hot water insoluble nitrogen, the nitrogen fraction insoluble at 100 °C during a 30 minute period.
- HWSN - hot water soluble nitrogen, the nitrogen fraction soluble under the same 100 °C phosphate buffer conditions.
- HWSN only - the part of HWSN that is soluble at 100 °C but not soluble under the cold-water condition.
- nutrient polymers - polymer-based component materials in fertilizing products designed to control nutrient release.
Who uses FprEN 17403?
FprEN 17403 is used by laboratories, fertilizer manufacturers, and quality control teams working with UF and MU slow-release fertilizers. It also supports buyers and conformity assessment work where cold-water and hot-water insoluble nitrogen results need to be compared on a common basis.
What changed in FprEN 17403 from the previous edition?
FprEN 17403 supersedes CEN/TS 17403:2021. The stated changes are:
- the Technical Specification has been adopted as a European Standard
- Clause 2 and Clause 3 have been updated
- the quantitative filter paper is specified more clearly
- combustion is considered as a method for determining residue on the filter
- the total nitrogen method 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 FprEN 17403?
- EN 1482-2 - gives general sample preparation provisions used in Clause 4.
- EN 12944-1 and EN 12944-2 - supply the fertilizer vocabulary used for terms and definitions.
- EN 15478 - provides the total nitrogen method used in the nutrient polymer calculation.
- ISO 5315 - provides the titrimetric nitrogen method after distillation used for residue analysis.
- EN 1482-1 - is cited as a recommended sampling method in Clause 4.1.
- ISO 5725-2 and ISO 5725-3 - are used for repeatability and reproducibility in the precision study.
- ISO 19670:2017 - is a source for several nitrogen-fraction definitions used in Clause 3.
What does the FprEN 17403 document contain?
FprEN 17403 contains method principles, reagents, apparatus lists, procedures, calculation formulas, and reporting rules for CWIN, HWIN, and nutrient polymer solubility. It also includes a precision clause with repeatability and reproducibility data, plus an informative annex with inter-laboratory study results.
For practical use, the document tells the laboratory how to prepare the sample, extract the nitrogen fraction, filter and wash the residue, measure nitrogen, and calculate the final result. It is therefore suited to routine testing, product characterization, and technical comparison of slow-release fertilizer materials.
Relations
- Effective Date
- 18-Jan-2023
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Frequently Asked Questions
FprEN 17403 is a draft published by the European Committee for Standardization (CEN). 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.
FprEN 17403 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.
FprEN 17403 has the following relationships with other standards: It is inter standard links to CEN/TS 17403:2021. Understanding these relationships helps ensure you are using the most current and applicable version of the standard.
FprEN 17403 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.
FprEN 17403 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
...