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