BS ISO 19746:2017,Determination of urea content in urea-based fertilizers by high performance liquid chromatography (HPLC).
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 modified ureas.
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 in hibitors)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 release N components.
ISO 19746:2017 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).
BS ISO 19746:2017 also applies to the determination of biuret content in urea containing fertilizer with the results published in the J. AOAC in 2014[5]. 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 Test Analyses[6].
4 Principles
The urea content in urea-based fertilizer is extracted by aqueous acetonitrile mobile phase and separated from other contents by High Performance liquid chromatography (HPLC) on an aminopropyl olumn. The urea peak is detected by a UV detector attached to the HPLC.
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