ISO 15237:2025

Overview

ISO 15237:2025 - Coal - Determination of total mercury specifies a reference laboratory method for measuring the total mercury mass fraction in coal. The third edition updates procedures for sample handling, introduces a direct combustion option, modifies formulae and reporting requirements, and remains the benchmark for validating faster instrumental methods. The standard emphasizes quantitative recovery of mercury - a volatile element - by strict procedural control.

Key Topics

• Scope and principle
  • Defines a procedure to determine total mercury in coal using oxygen bomb combustion with absorption of combustion products in water, followed by cold-vapour atomic absorption spectroscopy (CV-AAS).
  • Allows alternative reductants (stannous chloride, LiBH4, NaBH4) or direct combustion analysis if equivalence to the reference method is demonstrated.
• Reagents and materials
  • Specifies reagent grades and preparations: mercury stock and working standards, 10% nitric acid, potassium permanganate stabilizer, hydroxylammonium chloride, and stannous chloride reducing solution.
• Apparatus and cleanliness
  • Requires an oxygen combustion bomb constructed from mercury-free materials, silica crucible, precision balance, and an atomic absorption spectrometer with a flameless cold-vapour system.
  • Includes checks for bomb contamination and instructions for cleaning and blank determination.
• Sample preparation and procedure
  • Sample prep per ISO 13909‑4 / ISO 18283, moisture equilibration, and ~1 g test portions (or smaller if bomb design dictates).
  • Combustion steps: water in bomb, oxygen charge, firing, controlled venting, and quantitative recovery of washings into acidified volumetric flasks.
• Calibration and analysis
  • Matrix-matched calibration standards (e.g., 3, 5, 10 µg/L) stabilized with permanganate; measurement by CV‑AAS and reporting of results on specified bases.
• Quality and precision
  • Includes blank procedures, repeatability/reproducibility requirements, and test report content.

Applications

• Environmental monitoring of mercury content in coal feedstocks.
• Fuel quality control for power plants and utilities concerned with mercury emissions.
• Regulatory compliance testing where accurate total mercury mass fraction is required.
• Reference method for validating faster or automated mercury analyzers (e.g., direct combustion instruments).

Who uses this standard

• Analytical and environmental laboratories performing coal analysis.
• Coal producers and quality assurance teams.
• Power generation and combustion facilities monitoring fuel contaminants.
• Regulatory bodies and test method developers validating alternative mercury measurement methods.

Related Standards

• ISO 1928 (gross calorific value)
• ISO 3696 (laboratory water)
• ISO 13909-4 / ISO 18283 (sampling/preparation)
• ISO 5068-2 / ISO 11722 (moisture determination)
• ASTM 6722 (direct combustion total mercury in coal)

Keywords: ISO 15237:2025, total mercury, coal, mercury determination, oxygen bomb combustion, cold‑vapour AAS, direct combustion, mercury mass fraction.