Overview
ISO 17322:2015 provides standardized analytical methods for Sulfur Coated Urea (SCU) - a slow‑release fertilizer made by coating urea granules with sulfur and a sealant. The standard defines test procedures to quantify key quality attributes of SCU, including total nitrogen, dissolution performance (1DDR and 7DDR), sulfur content, biuret, water (H2O) and particle size. SCU typically contains about 30–40% nitrogen and 10–30% sulfur, and ISO 17322 helps laboratories and manufacturers ensure product consistency and regulatory compliance.
Key topics and technical requirements
- Scope and applicability
- Analytical methods are specifically applicable to Sulfur Coated Urea (SCU).
- Sampling and sample preparation are carried out in accordance with ISO 17323.
- Total nitrogen
- Determination follows ISO 5315 (titrimetric method after distillation).
- One‑day and seven‑day dissolution rates (1DDR and 7DDR)
- Two validated approaches:
- Titrimetric method after distillation - sample incubation (e.g., 20 g in a nylon net, 200 ml water) at (38.0 ± 0.5) °C for 24 h and 7 d, filtration, then nitrogen analysis.
- Refractometer method - a faster alternative for dissolution rate measurement.
- Sulfur content
- Dedicated procedure to determine the mass fraction of sulfur (principle, reagents, apparatus and calculation are specified).
- Biuret and water content
- Methods for mass fraction of biuret are specified including calibration procedures.
- Water content determination references the Karl Fischer titration technique (ISO 760).
- Particle size
- Particle size testing and sieving reference test sieves (ISO 3310‑1).
- Quality assurance and precision
- Includes provisions on repeatability, reproducibility and interlaboratory (ring) tests and reporting requirements.
Practical applications and users
ISO 17322:2015 is intended for:
- Fertilizer manufacturers and QC labs that produce or test Sulfur Coated Urea (SCU).
- Third‑party testing laboratories and certification bodies performing conformity assessments.
- Regulatory agencies and procurement teams verifying product specifications for compliance and performance.
- Agronomists and R&D groups evaluating slow‑release fertilizer performance (dissolution rates, nutrient content).
Benefits:
- Ensures consistent, comparable analytical results for SCU across laboratories.
- Supports product labeling, quality control, and international trade.
Related standards
- ISO 5315 - Determination of total nitrogen (titrimetric after distillation)
- ISO 760 - Water determination - Karl Fischer method
- ISO 17323 - SCU - General requirements (sampling and sample prep)
- ISO 3310‑1 - Test sieves - technical requirements
Keywords: ISO 17322, Sulfur Coated Urea, SCU, analytical methods, one‑day dissolution rate, 1DDR, 7DDR, total nitrogen, sulfur content, biuret, Karl Fischer, particle size.