ISO 19746:2017

Overview

ISO 19746:2017 specifies a standardized HPLC method for the determination of urea content in urea-based fertilizers. The scope covers pure urea, urea aldehydes (methylene urea, IBDU, CDU), urea triazone, UAN (urea ammonium nitrate), sulfur- and polymer-coated urea (SCU, PCU), and compound fertilizers containing urea. The method is based on High Performance Liquid Chromatography (HPLC) and is an extension of the AOAC Official Method 2003.14. Keywords: ISO 19746:2017, urea content, urea-based fertilizers, HPLC, urea determination.

Key topics and technical requirements

• Analytical principle: Extraction of urea with an aqueous acetonitrile mobile phase and separation on an aminopropyl HPLC column with UV detection.
• Mobile phase: Recommended composition is 850 ml acetonitrile + 150 ml water (LC grade acetonitrile); filter (0.22 μm) and degas before use.
• Standards and calibration: Urea standard solution (0.5 mg/ml) and a multi‑level working standard series to prepare a standard curve; at least two replicates per level.
• HPLC conditions: Typical settings include aminopropyl column, flow rate around 1.0 ml/min (other rates may be used), column temperature ~35 °C, injection volumes (e.g., 10 μl), and UV detection near 195–200 nm.
• Sample preparation: Grinding/sieving for solids (0.5 mm), ultrasonic dissolution, filtration (2.0 μm for sample particles; 0.22 μm for HPLC), and dilution to volumetric flasks per method.
• Calculations and reporting: Mass fraction of urea (%) calculated from the standard curve; report must include sample ID, method reference (ISO 19746), test results, sampling/analysis dates and repeatability assessment.
• Precision: Repeatability and reproducibility are addressed; users are directed to AOAC collaborative study data for statistical detail.

Applications and who uses it

• Quality control laboratories in fertilizer manufacturing to verify labeled urea content.
• Regulatory authorities verifying compliance with product specifications and nitrogen availability.
• Research and development teams characterizing modified and controlled‑release urea products (e.g., SCU, PCU, methylene ureas).
• Independent testing labs performing contract analyses for producers and distributors. Practical benefits include distinguishing free (readily available) urea from reacted/slow‑release urea forms and enabling consistent inter‑laboratory comparisons.

Related standards and references

• AOAC Official Method 2003.14 (basis for method development)
• ISO 3696 (water for analytical laboratory use)
• EN 15705 (related analyses for IBDU/CDU in fertilizers)
• ISO draft history: ISO/CD 18643 and ring test analyses are part of the method’s validation path.

ISO 19746:2017 provides a reproducible HPLC procedure for accurate urea quantification across diverse urea‑based fertilizer formulations, supporting product quality, regulatory compliance, and research.