ISO 17318:2015

Overview

ISO 17318:2015 - Fertilizers and soil conditioners - specifies laboratory methods for the determination of arsenic (As), cadmium (Cd), chromium (Cr), lead (Pb) and mercury (Hg) in fertilizers. The standard covers sample preparation, nitric‑acid microwave digestion, instrumental measurement by inductively coupled plasma - optical emission spectroscopy (ICP‑OES) and calculation, and sets expectations for method precision and reporting.

Key topics and technical requirements

• Scope: Analysis of metals soluble in nitric acid in fertilizers and soil conditioners; special attention for micro‑nutrient fertilizers.
• Sampling & sample prep:
  • Representative subsample (100 g) ground to pass a 0.50 mm sieve.
  • Test portion typically 1 g (adjusted for liming or organic matrices).
• Digestion:
  • Nitric acid predigestion followed by microwave digestion (example program: ramp to 160 °C and hold).
  • Use high‑purity reagents and ISO‑grade water (ISO 3696).
• Measurement:
  • ICP‑OES measurement of As, Cd, Cr, Pb, Hg; recommended element wavelengths are specified (e.g., As 189.042 nm, Cd 228.802 nm, Cr 283.563 nm, Pb 220.353 nm, Hg 184.950 nm).
  • Indium (5 mg/l) recommended as an internal standard for Cr and Pb to correct matrix effects; mixing device used for online addition.
• Quality & calculation:
  • Blended multi‑element calibration standards and blank determinations.
  • Result expression in mg/kg with formula and dilution corrections provided.
  • Precision evaluated through interlaboratory ring tests (precision assessed per ISO 5725‑2).
• Reporting:
  • Reports must include sample ID, method reference (ISO 17318), results, sampling and analysis dates and whether repeatability limits were met.

Practical applications and users

• Who uses it:
  • Fertilizer manufacturers and quality control labs verifying heavy‑metal content.
  • Agricultural testing labs, regulatory and certification bodies monitoring product safety and compliance.
  • Environmental and soil testing laboratories assessing potential contaminants from fertilizer use.
• Why it matters:
  • Ensures consistent, traceable measurement of toxic heavy metals in fertilizers to protect soil, crops and public health.
  • Supports regulatory compliance, product quality control, supplier audits and risk assessment.

Related standards

• ISO 3696 - Water for analytical laboratory use (referenced for reagent water quality).
• ISO 5725‑2 - Precision of measurement methods (used for ring test/statistics).

Keywords: ISO 17318:2015, fertilizer heavy metals, ICP‑OES, nitric acid digestion, microwave digestion, arsenic cadmium chromium lead mercury, laboratory testing, fertilizer quality control.