EN 15688:2008

Fertilizers - Determination of urease inhibitor N-(n-butyl)thiophosphoric triamide (NBPT) using high-performance liquid chromatography (HPLC)

This document specifies a method for the quantitative determination of the urease inhibitor N-(n-butyl)thiophosphoric triamide (NBPT) content in water-soluble matrices, i.e. urea based fertilizers using high performance liquid chromatography (HPLC).
NOTE   Pure NBPT reference material is required as a standard for the quantitative calibration.

Düngemittel - Bestimmung von Urease-Hemmstoff N-(n-Butyl)-thiophosphortriamid (NBPT) mit Hochleistungs-Flüssigchromatographie (HPLC)

Dieses Dokument legt ein Verfahren zur quantitativen Bestimmung des Urease-Hemmstoffs N-(n-Butyl)-
thiophosphortriamid (NBPT)-Gehalts in wasserlöslichen Matrices, d. h. in harnstoffhaltigen Düngemitteln, mit
Hochleistungs-Flüssigchromatographie (HPLC) fest.
ANMERKUNG Reines NBPT-Referenzmaterial ist als Standard für die quantitative Kalibrierung erforderlich.

Engrais - Détermination de l'inhibiteur d'uréase N-(n-butyl) triamine thiophosphorique (NBPT) par chromatographie liquide haute performance (HPLC)

Le présent document spécifie une méthode pour la détermination quantitative de la teneur en inhibiteur d’uréase N-(n-butyl) triamine thiophosphorique (NBPT) dans des matrices solubles dans l’eau, c’est-à-dire des engrais à base d’urée, par chromatographie liquide haute performance (HPLC).
NOTE   Un matériau de référence NBPT pur est requis en tant qu’étalon pour l’étalonnage quantitatif.

Gnojila - Določevanje inhibitorja ureaze N-(n-butil)tiofosfortriamida (NBPT) s tekočinsko kromatografijo visoke ločljivosti (HPLC)

General Information

• Status: Published
• Publication Date: 05-Aug-2008
• ICS: 65.080 - Fertilizers
• Technical Committee: CEN/TC 260 - Fertilizers and liming materials
• Drafting Committee: CEN/TC 260/WG 7 - Chemical analysis
• Current Stage: 9093 - Decision to confirm - Review Enquiry
• Start Date: 05-Feb-2025
• Completion Date: 11-Feb-2026
• Mandate: M/335 - Standardization Mandate assigned to the CEN concerning the modernisation of the methods of anylysis of Fertilizers
• Ref Project: SIST EN 15688:2008 - Fertilizers - Determination of urease inhibitor N-(n-butyl)thiophosphoric triamide (NBPT) using high-performance liquid chromatography (HPLC)

Relations

• Refers: EN 12944-2:1999 - Fertilizers and liming materials and soil improvers - Vocabulary - Part 2: Terms relating to fertilizers
• Effective Date: 28-Jan-2026
• Refers: EN ISO 3696:1995 - Water for analytical laboratory use - Specification and test methods (ISO 3696:1987)
• Effective Date: 28-Jan-2026
• Refers: EN 12944-1:1999 - Fertilizers and liming materials and soil improvers - Vocabulary - Part 1: General terms
• Effective Date: 28-Jan-2026
• Refers: EN 1482-2:2024 - Fertilizers, liming materials and inhibitors - Sampling and sample preparation - Part 2: General sample preparation provisions
• Effective Date: 28-Jan-2026
• Referred By: CEN/TS 17752:2022 - Inorganic fertilizers - Determination of specific inhibitors
• Effective Date: 28-Jan-2026

Overview

EN 15688:2008 is a European standard developed by CEN that specifies a method for the quantitative determination of the urease inhibitor N-(n-butyl)thiophosphoric triamide (NBPT) in urea-based fertilizers. The method utilizes high-performance liquid chromatography (HPLC) to accurately measure NBPT content in water-soluble fertilizer matrices. NBPT is commonly added to fertilizers to improve nitrogen efficiency by reducing urease activity, which in turn minimizes ammonia volatilization losses in agricultural applications.

This standard ensures a consistent, reliable analytical approach across laboratories and industry, supporting compliance, quality control, and regulatory requirements for fertilizers containing NBPT.

Key Topics

• Urease Inhibitor Analysis
  EN 15688:2008 focuses on quantitative analysis of NBPT, a vital additive in agrochemicals for controlling nitrogen release.

• High-Performance Liquid Chromatography (HPLC)
  The procedure is built around HPLC technology, allowing precise separation and detection of NBPT in fertilizer samples.

• Sample Preparation and Calibration
  Accurate preparation of fertilizer samples and calibration with pure NBPT reference materials are central to achieving valid results.

• Precision and Reliability
  The standard details assessment of method repeatability and reproducibility, supported by inter-laboratory testing, to ensure consistent performance.

• Test Reporting
  A systematic outline for documenting results is provided, ensuring traceability and clarity in compliance reports.

Applications

• Fertilizer Quality Control
  Manufacturers and laboratories use EN 15688:2008 to verify NBPT content in urea-based fertilizers, ensuring that products meet specified formulation standards.

• Regulatory Compliance
  The method supports compliance with EU fertilizer regulations where accurate quantification of NBPT is required for product registration and market release.

• Research and Development
  Agricultural researchers and product developers apply this standardized HPLC method to assess the performance of novel formulations or to study the stability of NBPT in various fertilizer blends.

• Accredited Laboratory Testing
  Accredited testing services rely on this standard to provide certified analysis of fertilizers for NBPT content, supporting the fertilizer industry and agricultural sector.

Related Standards

EN 15688:2008 is part of a broader framework of standards addressing the testing and quality assurance of fertilizers:

• EN 1482-1 – Fertilizers and liming materials – Sampling and sample preparation – Part 1: Sampling
  Describes recommended procedures for collecting representative fertilizer samples.

• EN 1482-2 – Fertilizers and liming materials – Sampling and sample preparation – Part 2: Sample preparation
  Details preparation steps crucial for achieving accurate HPLC analysis.

• EN 12944-1 & EN 12944-2 – Vocabulary for fertilizers and liming materials
  Defines general and fertilizer-specific terminology for clarity and consistency.

• EN ISO 3696 – Water for analytical laboratory use – Specification and test methods
  Specifies water purity requirements vital for chemical analysis.

• ISO 5725-1 – Accuracy of measurement methods and results – General principles and definitions
  Used for calculating repeatability and reproducibility within this and similar analytical standards.

• Regulation (EC) No 2003/2003 – Relating to fertilizers
  Sets regulatory context referenced by this standard for fertilizer products marketed in the European Union.

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Organizations and laboratories adhering to EN 15688:2008 guarantee precise, consistent measurement of NBPT in fertilizers, enhancing product performance, compliance, and environmental stewardship through standardized HPLC analysis.

Standards Content (Sample)

SLOVENSKI STANDARD
01-oktober-2008
*QRMLOD'RORþHYDQMHLQKLELWRUMDXUHD]H1QEXWLOWLRIRVIRUWULDPLGD1%37V
WHNRþLQVNRNURPDWRJUDILMRYLVRNHORþOMLYRVWL+3/&
Fertilizers - Determination of urease inhibitor N-(n-butyl)thiophosphoric triamide (NBPT)
using high-performance liquid chromatography (HPLC)
Düngemittel - Bestimmung von Urease-Hemmstoff N-(n-Butyl)-thiophosphortriamid
(NBPT) mit Hochleistungs-Flüssigchromatographie (HPLC)
Engrais - Détermination de l'inhibiteur d'uréase N-(n-butyl) thiophosphorique triamide
(NBPT) par chromatographie liquide haute performance (CLHP)
Ta slovenski standard je istoveten z: EN 15688:2008
ICS:
65.080 Gnojila Fertilizers
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD
EN 15688
NORME EUROPÉENNE
EUROPÄISCHE NORM
August 2008
ICS 65.080
English Version
Fertilizers - Determination of urease inhibitor N-(n-
butyl)thiophosphoric triamide (NBPT) using high-performance
liquid chromatography (HPLC)
Engrais - Détermination de l'inhibiteur d'uréase N-(n-butyl) Düngemittel - Bestimmung von Urease-Hemmstoff N-(n-
triamine thiophosphorique (NBPT) par chromatographie Butyl)-thiophosphortriamid (NBPT) mit Hochleistungs-
liquide haute performance (HPLC) Flüssigchromatographie (HPLC)
This European Standard was approved by CEN on 4 July 2008.
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 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 Management Centre has the same status as the
official versions.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland,
France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal,
Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre: rue de Stassart, 36  B-1050 Brussels
© 2008 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN 15688:2008: E
worldwide for CEN national Members.

Contents Page
Foreword.3
1 Scope .4
2 Normative references .4
3 Terms and definitions .4
4 Principle.4
5 Reagents.4
6 Apparatus .5
7 Sampling and sample preparation.6
8 Procedure .6
9 Calculation and expression of the result .7
10 Precision.7
11 Test report .8
Annex A (informative) Results of the inter-laboratory test .9
Bibliography .10

Foreword
This document (EN 15688:2008) 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 February 2009, and conflicting national standards shall be withdrawn
at the latest by February 2009.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent rights.
This document has been prepared under a mandate given to CEN by the European Commission and the
European Free Trade Association.
According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following
countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Cyprus, Czech
Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia,
Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain,
Sweden, Switzerland and the United Kingdom.
1 Scope
This document specifies a method for the quantitative determination of the urease inhibitor N-(n-
butyl)thiophosphoric triamide (NBPT) content in water-soluble matrices, i.e. urea based fertilizers using high
performance liquid chromatography (HPLC).
NOTE Pure NBPT reference material is required as a standard for the quantitative calibration.
2 Normative references
The following referenced documents are indispensable for the application 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 12944-1:1999, Fertilizers and liming materials and soil improvers — Vocabulary — Part 1: General terms
EN 12944-2:1999, Fertilizers and liming materials and soil improvers — Vocabulary — Part 2: Terms relating
to fertilizers
EN ISO 3696, Water for analytical laboratory use — Specification and test methods (ISO 3696:1987)
3 Terms and definitions
For the purposes of this document, the terms and definitions given in EN 12944-1:1999 and EN 12944-2:1999
apply.
4 Principle
This analytical method is based on the principles of liquid chromatography, with absorption in the ultraviolet
region for detection of the separated compounds.
5 Reagents
5.1 General
Use only reagents of recognized analytical grade and distilled or demineralized water (grade 3 according to
EN ISO 3696).
5.2 Reagents for liquid chromatography
5.2.1 Acetonitrile, HPLC-grade or spectroscopic grade.
5.2.2 Water, Milli-Q purified or equiva
...