FprEN 18251

SLOVENSKI STANDARD
01-december-2025
Izboljševalci tal in rastni substrati - Določanje fosfonatov
Soil improvers and growing media - Determination of phosphonate content
Bodenverbesserungsmittel und Kultursubstrate - Bestimmung des Phosphonatgehalts
Amendements du sol et supports de culture - Détermination de la teneur en
phosphonates
Ta slovenski standard je istoveten z: prEN 18251
ICS:
65.080 Gnojila Fertilizers
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

DRAFT
EUROPEAN STANDARD
prEN 18251
NORME EUROPÉENNE
EUROPÄISCHE NORM
October 2025
ICS 65.080
English Version
Soil improvers and growing media - Determination of
phosphonate content
Amendements du sol et supports de culture - Bodenverbesserungsmittel und Kultursubstrate -
Détermination de la teneur en phosphonates Bestimmung des Phosphonatgehalts
This draft European Standard is submitted to CEN members for enquiry. It has been drawn up by the Technical Committee
CEN/TC 223.
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
© 2025 CEN All rights of exploitation in any form and by any means reserved Ref. No. prEN 18251:2025 E
worldwide for CEN national Members.

prEN18251:2025 (E)
Contents Page
European foreword . 3
Introduction . 4
1 Scope . 5
2 Normative references . 5
3 Terms and definitions . 5
4 Principle . 5
5 Reagents . 5
6 Apparatus . 6
7 Sampling . 7
8 Procedure . 7
8.1 Safety . 7
8.2 Sample preparation . 7
8.3 Water extraction . 7
8.4 Preparation of the calibration solutions . 7
8.5 Measurement . 8
8.5.1 Instrument conditions . 8
8.5.2 IC-CD measurement . 9
9 Calculation and expression of the results . 9
9.1 Integration of peaks . 9
9.2 Concentration of phosphonates in test solutions . 9
10 Test report . 10
11 Validation of the method . 11
11.1 Validation in accordance with ISO 5725-2. 11
11.2 Performance characteristics. 11
Annex A (informative) Performance characteristics of the method . 12
Bibliography . 14

prEN18251:2025 (E)
European foreword
This document (prEN 18251:2025) has been prepared by Technical Committee CEN/TC 223 “Soil
improvers and growing media”, the secretariat of which is held by NEN, in collaboration with CEN/TC 260
“Fertilizers and liming materials” and CEN/TC 455 “Plant Biostimulants”.
This document is currently submitted to the CEN Enquiry.
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.
prEN18251:2025 (E)
Introduction
This document was prepared by the experts of CEN/TC 223 “Soil improvers and growing media”. The
European Committee for Standardization (CEN) was requested by the European Commission (EC) to
draft European standards or European standardization deliverables to support the implementation of
Regulation (EU) 2019/1009 of 5 June 2019 laying down rules on the making available on the market of
EU fertilizing products (“FPR” or “Fertilising Products Regulation”) [1].
This standardization request, presented as M/564, also contributes to the Communication on “Innovating
for Sustainable Growth: A Bio economy for Europe”. CEN/TC 223 “Soil improvers and growing media”
was established to carry out the work programme that will prepare a series of standards. WG 4 of
CEN/TC 223 “Analytical methods”, was requested to develop a work programme as part of this request.
The interest in soil improvers and growing media have increased significantly in Europe as a valuable
tool to use in agriculture.
This document describes an extraction and measurement for the determination of phosphonate
(phosphite) in growing media and soil improvers. The standard is based on a water extraction of the
phosphonate (phosphite) followed by ion chromatography with conductivity detection (IC-CD) [2], [3],
[4], [5], [6].
The ion chromatography with a conductivity detector (IC-CD) method can be used in well-equipped
analytical laboratories for the determination of different ions. In the field of fertilizing products, the
method is used and standardized for the determination of perchlorates in mineral fertilizers. The IC-CD
method can determine more ions simultaneously.
The legislative limit for phosphonate content is 0,5 % (mass fraction) and the method described in this
document was adapted to achieve this requirement and simultaneously to reduce interferences from
other co-extracted anions as much as possible.
The definition of phosphonates is not clearly stated in the Regulation (EU) 2019/1009 [1] and to avoid
any misunderstanding the results are expressed as a content of phosphorus (P) bound in the form of free
water-soluble phosphonates (P-PO ).
prEN18251:2025 (E)
1 Scope
This document specifies a method for the extraction and determination of phosphonates (P-PO ) in
growing media and soil improvers using ion chromatography and conductivity detection (IC-CD).
This document is applicable to the fertilizing product blends where a blend is a mix of two or more
fertilising products belonging to the categories of fertilizers, liming material, soil improvers, growing
media, inhibitors and plant biostimulants, and where soil improvers and/or growing media are the
components with the highest percentage in the blend by mass or volume, or in the case of products in
liquid form by dry mass. If the soil improvers and/or growing media are not the components with the
highest percentage in the blend, the document relevant to the component with the highest percentage in
the blend applies. In case a blend is composed of fertilising products mixed in equal quantities, the user
of the document decides which standard to apply.
NOTE A soil improver consists of a single bulky (volume-building) component or a mix of bulky (volume-
building) components (for example peat, wood fibres, coconut coir, compost, expanded perlite).
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.
CEN/TS 17732:2022, Soil improvers and growing media - Terminology
EN 12579:2024, Soil improvers and growing media - Sampling
prEN 13040-1:2025, Soil improvers and growing media — Sample preparation — Part 1: Sample
preparation for chemical and physical tests, determination of dry matter content, moisture content and
laboratory bulk density
3 Terms and definitions
For the purposes of this document, the following terms and definitions and the terms and definitions
given in CEN/TS 17732:2022 apply.
3.1
phosphonates
salts derived from phosphonic acid (H PO )
3 3
4 Principle
A representative test portion of the sample is extracted with water. Phosphonate in the extract is
selectively separated from other compounds using ion chromatography (IC) and determined by a
conductivity detector (CD). External calibration is used for quantification of the amount of the
phosphonate.
5 Reagents
5.1 General
All reagents shall be of recognized analytical grade. The concentration of phosphonate in the reagents
and deionized water used shall be low enough not to affect the results of the determination.
5.2 Water, with a specific conductivity not higher than 0,2 mS/m at 25 °C.
prEN18251:2025 (E)
5.3 Phosphonate standard stock solution, r(P-PO ) = 1 000 mg/l is prepared by dissolving
commercially available sodium phosphite dibasic pentahydrate salt (Mw = 216,04 mol/l, purity ≥ 98 %).
For preparation the phosphonate standard stock solution 0,697 ± 0,001 g is weighed, transferred to
100 ml volumetric flask, fill with deionized water (5.2) to final volume and mix thoroughly.
5.4 Phosphonate standard solution, r(P-PO ) = 100 mg/l is prepared from a standard stock solution
(5.3) by appropriate dilution with deionized water (5.2). Pipette 10 ml of stock solution (5.3) to a 100 ml
volumetric flask, fill with deionized water to final volume and mix thoroughly.
5.5 Mobile phase, KOH cartridge for ion chromatography (commercially supplied). Concentration of
the KOH mobile phase is electrolytically generated in externally supplied deionized water (5.2).
NOTE Different mobile phase can be used according to the instructions of the manufacturer of the column but
it is necessary to verify optimal separation conditions. For example, Metrosep A Supp5 (250 mm/4 mm) and a
recommended mobile phase for this column – 3,2 mM Na2CO3 + 1 mM NaHCO3 was successfully used for the
analysis.
−
5.6 Chloride standard, r(Cl ) = 1000 mg/l – commercially available.
5.7 Nitrate standard, r(NO -) = 1000 mg/l – commercially available.
−
5.8 Solution for checking chromatographic separation, r(P-PO ) = 10 mg/l, r(Cl and NO -
3 3
) = 50 mg/l is prepared by pipetting 1 ml of phosphonate standard stock solution (5.3), 5 ml of chloride
standard (5.6), 5 ml of nitrate standard (5.7) to 100 ml volumetric flask and fill to final volume with
deionized water (5.2).
6 Apparatus
6.1 Common laboratory glassware and plastic.
6.2 Laboratory grinder, capable of grinding to a particle size less than 0,5 mm.
6.3 Analytical balance, accuracy ≤ 1 mg.
6.4 Shaker, rotary or horizontal shaker. Shaking shall prevent any settling of the sample during
extraction.
6.5 Extraction vessels, capacity 200 ml to 500 ml.
−1
6.6 Centrifuge (optional), for minimum 4 000 min (approx. 2 000 g).
6.7 Single use syringe filters (0,22 µm) or vials with filters, for filtering of test solutions prior to
analysis.
6.8 Ion chromatograph, with conductivity detector (IC-CD).
For lower signal noise a supressed conductivity detector is preferred.
6.9 Chromatographic column for anion exchange, suitable for the selective se
...