SIST EN 15959:2024

Inorganic fertilizers - Determination of extracted phosphorus P2O5

This document specifies a method for the determination of phosphorus in fertilizer extracts.
The method is applicable to all extracts of fertilizers for the determination of the different forms of phosphorus as phosphorus soluble in mineral acids, water-soluble phosphorus, phosphorus soluble in solutions of neutral ammonium citrate, phosphorus soluble in 2 % citric acid and phosphorus soluble in a mass fraction of 2 % formic acid.
The method has only been validated on inorganic fertilizers but can be applicable to all extracted phosphorous if proper extraction methods are used.

Anorganische Düngemittel - Bestimmung des Gehalts an extrahiertem Phosphor P2O5

Dieses Dokument legt ein Verfahren zur Bestimmung von Phosphor in Düngemittelextrakten fest.
Das Verfahren ist für alle Düngemittelextrakte zur Bestimmung verschiedener Formen von Phosphor anwendbar, wie Phosphor, der in Mineralsäuren löslich ist, wasserlöslicher Phosphor, Phosphor, der in neutralen Ammoniumcitrat-Lösungen löslich ist, Phosphor, der in 2%iger Citronensäure löslich ist, und Phosphor, der in Ameisensäure mit einem Massenanteil von 2 % löslich ist.
Das Verfahren wurde nur für anorganische Düngemittel validiert, kann aber bei Verwendung geeigneter Extraktionsverfahren auf jeden Phosphor in den Extrakten angewendet werden.

Engrais inorganiques - Dosage du phosphore extrait P2O5

Le présent document spécifie une méthode de dosage du phosphore dans des extraits d’engrais.
La méthode est applicable à tous les extraits d’engrais pour le dosage des différentes formes de phosphore telles que le phosphore soluble dans les acides minéraux, dans l’eau, dans des solutions de citrate d’ammonium neutre, dans l’acide citrique à 2 % et dans l’acide formique ayant une fraction massique de 2 %.
La méthode a uniquement été validée pour les engrais inorganiques, mais elle peut être applicable à tout phosphore extrait si des méthodes d’extraction correctes sont utilisées.

Anorganska gnojila - Določanje ekstrahiranega fosforja P2O5

Ta dokument določa metodo za določanje fosforja v izvlečkih gnojil.
Metoda se uporablja za vse izvlečke gnojil za določevanje različnih oblik fosforja, topnega v mineralnih kislinah, vodi, raztopinah amonijevega citrata, 2-odstotni citronski kislini in 2-odstotni mravljični kislini.

General Information

• Status: Published
• Public Enquiry End Date: 14-Nov-2023
• Publication Date: 12-May-2024
• ICS: 65.080 - Fertilizers
• Technical Committee: KAT - Soil quality
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 12-Mar-2024
• Due Date: 17-May-2024
• Completion Date: 13-May-2024
• Directive: 2019/1009 - 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
• 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
• Ref Project: EN 15959:2023 - Inorganic fertilizers - Determination of extracted phosphorus P2O5

Relations

• Replaces: SIST EN 15959:2012 - Fertilizers - Determination of extracted phosphorus
• Effective Date: 01-Jun-2024

Overview

EN 15959:2023 - published by CEN - specifies a laboratory method for the determination of extracted phosphorus expressed as P2O5 in fertilizer extracts. The procedure is aimed primarily at inorganic fertilizers (validated on inorganic matrices) but can be applied to other extracted phosphorus fractions when appropriate extraction methods are used. The standard replaces EN 15959:2011 and was approved in December 2023.

Key topics and technical requirements

• Scope of extracts: phosphorus soluble in mineral acids, water-soluble phosphorus, phosphorus soluble in neutral ammonium citrate, 2 % citric acid and 2 % formic acid extracts.
• Analytical principle: precipitation of phosphorus as quinoline phosphomolybdate using molybdate-based reagents (sodium or ammonium molybdate), followed by drying at 250 °C and gravimetric weighing of the precipitate.
• Reagents and apparatus: distilled water, concentrated nitric acid, citric acid, quinoline, molybdate reagent solutions; standard laboratory equipment including sintered glass funnels, filter crucibles (5–20 µm), steam bath, oven at 250 ± 10 °C and a balance capable of 0.0001 g.
• Procedure highlights:
  • Aliquot treatment and acidification (e.g., ~15 ml HNO3 for typical aliquots).
  • Optional hydrolysis step (reflux/boil) to convert metaphosphates, pyrophosphates or polyphosphates to orthophosphate.
  • Dropwise addition of molybdate reagent, aging on a steam bath, vacuum filtration, thorough washing, drying and weighing.
  • Blank tests and verification using potassium dihydrogen phosphate (KH2PO4) are required.
• Calculation & expression: mass fraction calculations reference conversion factors and dilution/test portion parameters; formulas provided for P and P2O5 reporting.
• Precision: inter‑laboratory tests (multiple extraction methods), with repeatability and reproducibility statistics calculated per ISO 5725‑2. Additional precision data for formic-acid-soluble P2O5 were added in this edition.

Applications and who uses it

• Fertilizer testing laboratories for routine quality control and batch release.
• Manufacturers of inorganic fertilizers to quantify available phosphorus (P2O5) for product specification and labeling.
• Regulatory and certification bodies ensuring compliance with fertilizer standards and trade requirements.
• Research and agronomy labs assessing phosphorus fractions in fertilizer research, formulation and efficacy studies.
• Use cases include product specification, verification of declared nutrient content, R&D comparisons of extraction methods, and enforcement testing.

Related standards

• EN 1482-2 - Sampling and sample preparation (recommended sample prep)
• EN 12944-1 / EN 12944-2 - Vocabulary for fertilizers and liming materials
• Extraction method references: EN 15956, EN 15957, EN 15958, EN 15919 (used in inter‑laboratory validation)

Keywords: EN 15959:2023, inorganic fertilizers, phosphorus determination, P2O5, fertilizer extracts, quinoline phosphomolybdate, molybdate reagent, hydrolysis, precision, CEN.

Standards Content (Sample)

SLOVENSKI STANDARD
01-junij-2024
Nadomešča:
SIST EN 15959:2012
Anorganska gnojila - Določanje ekstrahiranega fosforja P2O5
Inorganic fertilizers - Determination of extracted phosphorus P2O5
Anorganische Düngemittel - Bestimmung des Gehalts an extrahiertem Phosphor P2O5
Engrais inorganiques - Dosage du phosphore extrait P2O5
Ta slovenski standard je istoveten z: EN 15959:2023
ICS:
65.080 Gnojila Fertilizers
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN 15959
EUROPEAN STANDARD
NORME EUROPÉENNE
December 2023
EUROPÄISCHE NORM
ICS 65.080 Supersedes EN 15959:2011
English Version
Inorganic fertilizers - Determination of extracted
phosphorus P O
2 5
Engrais inorganiques - Dosage du phosphore extrait Anorganische Düngemittel - Bestimmung des Gehalts
P O an extrahiertem Phosphor P O
2 5 2 5
This European Standard was approved by CEN on 27 November 2023.

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. Up-to-date lists and bibliographical references
concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN
member.
This European Standard exists 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.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATIO N

EUROPÄISCHES KOMITEE FÜR NORMUN G

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2023 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN 15959:2023 E
worldwide for CEN national Members.

Contents Page
European foreword . 3
1 Scope . 4
2 Normative references . 4
3 Terms and definitions . 4
4 Principle . 4
5 Reagents . 4
6 Apparatus and equipment . 5
7 Sampling and sample preparation . 6
8 Procedure . 6
8.1 Treatment of the solution . 6
8.2 Hydrolysis . 6
8.3 Weighing the crucible . 6
8.4 Precipitation . 7
8.5 Filtering and washing . 7
8.6 Drying and weighing . 7
8.7 Blank test . 7
8.8 Verification . 7
9 Calculation and expression of the result . 7
10 Precision . 8
10.1 Inter-laboratory tests . 8
10.2 Repeatability . 8
10.3 Reproducibility . 8
11 Test report . 9
Annex A (informative) Statistical results of the inter-laboratory tests . 10
Bibliography. 13

European foreword
This document (EN 15959:2023) has been prepared by Technical Committee CEN/TC 260 “Fertilizers
and liming materials”, the secretariat of which is held by DIN.
This European Standard shall be given the status of a national standard, either by publication of an
identical text or by endorsement, at the latest by June 2024, and conflicting national standards shall be
withdrawn at the latest by June 2024.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
This document supersedes EN 15959:2011.
In comparison with the previous edition EN 15959:2011, the following technical modifications have been
made:
— precision data for the determination of the formic acid soluble P O content have been added to
2 5
Table 2 and Annex A.
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.
Any feedback and questions on this document should be directed to the users’ national standards body.
A complete listing of these bodies can be found on the CEN website.
According to the CEN-CENELEC Internal Regulations, the national standards organisations of the
following countries are bound to implement this European Standard: 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 the United
Kingdom.
1 Scope
This document specifies a method for the determination of phosphorus in fertilizer extracts.
The method is applicable to all extracts of fertilizers for the determination of the different forms of
phosphorus as phosphorus soluble in mineral acids, water-soluble phosphorus, phosphorus soluble in
solutions of neutral ammonium citrate, phosphorus soluble in 2 % citric acid and phosphorus soluble in
a mass fraction of 2 % formic acid.
The method has only been validated on inorganic fertilizers but can be applicable to all extracted
phosphorous if proper extraction methods are used.
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 and liming materials — Sampling and sample preparation — Part 2: Sample
preparation
EN 12944-1, Fertilizers and liming materials — Vocabulary — Part 1: General terms
EN 12944-2, Fertilizers and liming materials — Vocabulary — Part 2: Terms relating to fertilizers
3 Terms and definitions
For the purposes of this document, the terms and definitions given in EN 12944-1 and EN 12944-2 apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— IEC Electropedia: available at https://www.electropedia.org/
— ISO Online browsing platform: available at https://www.iso.org/obp
4 Principle
After possible hydrolysis, phosphorus is precipitated in an acid media in the form of quinoline
phosphomolybdate.
After filtering and washing, the precipitate is dried at 250 °C and weighed.
In the above-mentioned conditions no interfering action is exerted by the compounds likely to be found
in the solution (mineral and organic acids, ammonium ions, soluble silicates, etc.) if a reagent based on
sodium molybdate or ammonium molybdate is used in the precipitation.
5 Reagents
Use only reagents of recognized analytical grade.
5.1 Water, distilled or demineralized.
5.2 Concentrated nitric acid, mass concentration ρ = 1,40 g/ml.
5.3 Reagent solutions.
5.3.1 Reagent solutions based on sodium molybdate.
Solution A: Dissolve 70 g of sodium molybdate dihydrate in 100 ml of distilled water.
Solution B: Dissolve 60 g of citric acid monohydrate in 100 ml of distilled water and add 85 ml
concentrated nitric acid (5.2).
Solution C: Stir solution A into solution B to obtain solution C.
Solution D: To 50 ml of distilled water (5.1), add 35 ml of concentrated nitric acid (5.2), then 5 ml of
freshly distilled quinoline. Add this solution to solution C, mix thoroughly and leave standing overnight
in the dark. After this, make up to 500 ml with distilled water (5.1), mix again, and filter through a sintered
glass funnel (6.6).
5.3.2 Reagent solutions based on ammonium molybdate.
Solution A: In 300 ml of distilled water (5.1), dissolve 100 g of ammonium molybdate while heating gently
and stirring from time to time.
Solution B: Dissolve 120 g of citric acid monohydrate in 200 ml of distilled water (5.1), add 170 ml of
concentrated nitric acid (5.2).
Solution C: Add 10 ml of freshly distilled quinoline to 70 ml of concentrated nitric acid (5.2).
Solution D: Slowly pour, stirring well, solution A into solution B. After thoroughly mixing add solution C
to this mixture and make up to 1 l. Leave standing for two days in a dark place and filter through a sintered
glass funnel (6.6).
The reagent solutions 5.3.1 and 5.3.2 may be used in the same way; both shall be kept in the dark in
stoppered polyethylene bottles.
6 Apparatus and equipment
Usual laboratory glassware and equipment and, in particular, the following.
6.1 500 ml Erlenmeyer flask, with a wide neck.
6.2
...