ISO 19746:2017

INTERNATIONAL ISO
STANDARD 19746
First edition
2017-02
Determination of urea content in urea-
based fertilizers by high performance
liquid chromatography (HPLC)
Détermination de la teneur en urée dans les engrais à base d’urée par
chromatographie liquide à haute performance (CLHP)
Reference number
©
ISO 2017
© ISO 2017, Published in Switzerland
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ii © ISO 2017 – All rights reserved

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principles . 1
5 Reagents . 1
6 Apparatus . 2
7 Procedures . 2
7.1 Preparation of test sample . 2
7.2 Preparation of the test solution . 2
7.3 Preparation of urea working standard solution . 3
7.4 HPLC conditions . 3
7.5 Preparation of standard curve . 3
7.6 Determination of the urea content in the test solution . . 4
7.7 Calculation and expression of results. 4
7.8 Precision . 4
7.8.1 Repeatability, r . 4
7.8.2 Reproducibility, R . 4
7.9 Test report . 4
Annex A (informative) Examples of the retention times of triuret, biuret, urea and some
other ureaforms . 5
Bibliography . 8
Foreword
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This document was prepared by Technical Committee ISO/TC 134, Fertilizers and soil conditioners.
iv © ISO 2017 – All rights reserved

Introduction
Urea is the most widely used source of nitrogen fertilizers worldwide and is used in a variety of
forms such as pure urea, in combination with other nutrients, in complex fertilizers, and as reacted or
[2]
modified ureas .
[3]
Due to the rapid hydrolysis of urea in the environment, especially when applied at the soil surface ,
efforts have been made to modify urea to slow down this loss process. Slow release nitrogen fertilizers
such as methylene urea compounds, controlled release N fertilizers such as sulfur-coated urea (SCU)
or polymer-coated urea (PCU), and stabilized N fertilizers containing additives (urease inhibitors and
nitrification inhibitors) are examples of products aimed at containing the rapid hydrolyses of urea in
the soil.
Accurate determination of urea in urea-based fertilizers is desirable for regulatory and product
quality purposes. This is especially true for those fertilizers in which the urea content is physically or
chemically modified. Most of these modified fertilizers contain some amounts of free and unreacted
urea which is readily available N and therefore could not be accounted as part of the slow or controlled
[5]
release N component .
INTERNATIONAL STANDARD ISO 19746:2017(E)
Determination of urea content in urea-based fertilizers by
high performance liquid chromatography (HPLC)
1 Scope
This document specifies the test procedure for determining the urea content in urea-based fertilizers,
including urea, urea aldehydes [methylene urea fertilizers, isobutylene diurea (IBDU), crotonylidene
diurea (CDU)], urea triazone fertilizers, urea ammonium nitrate (UAN), sulfur- and polymer-coated
urea (SCU and PCU), as well as compound fertilizers containing urea. The method is based on High
Performance Liquid Chromatography (HPLC).
The proposed method is an extension of the AOAC Official Method 2003.14 which was collaboratively
studied for the “Determination of Urea in Water-Soluble Urea-Formaldehyde Fertilizer Products and in
[4]
Aqueous Urea Solutions” in 2003. The method was published in the Journal of AOAC in 2004 and was
granted the First Action in 2003 and the Final Action in 2008.
This method also applies to the determination of biuret content in urea containing fertilizer with the
[5]
results published in the J. AOAC in 2014 . This method was adopted by the International Organization
for Standardization (ISO) as a Committee Draft (ISO/CD 18643) in 2014, and after review and the Ring
[6]
Test Analyses .
NOTE This HPLC method can also be utilized to analyse Crotonylidene diurea (CDU) and Isobutylidene
[1]
diurea (IBDU) contents within those above-mentioned fertilizers, in addition to EN 15705 .
2 Normative references
The fo
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