Overview
ISO 21826-1:2022 specifies a laboratory method for determining the total iron content in iron ores using an EDTA photometric titration after microwave digestion. The procedure applies to natural iron ores, iron ore concentrates and agglomerates (including sinter) with a total iron mass fraction from 37.00 % to 72.00 %. The standard covers sample digestion, reagent preparation, EDTA standardization, automatic photometric titration and calculation/reporting of results. Note: this method is not intended as a referee (official arbitration) method.
Keywords: ISO 21826-1:2022, iron ores, EDTA photometric titration, microwave digestion, total iron content, iron ore analysis
Key topics and technical requirements
- Scope and applicability: Valid for Fe mass fractions 37.00–72.00 % in ores, concentrates and agglomerates; excludes use as a referee method.
- Principle: Closed-vessel microwave digestion in a mixture of nitric acid, hydrochloric acid and hydrofluoric acid; dilution and pH adjustment to pH 1; sulphuric acid added to prevent titanium hydroxide precipitation; boric acid to mitigate fluoride interference; automatic photometric titration with disodium EDTA.
- Reagents and solutions: Analytical-grade acids (HCl, HNO3, HF), sulphuric and boric acid solutions, sodium hydroxide, iron standard solution and 0.10 mol·L−1 EDTA (with procedures for preparation and standardization).
- Apparatus and conditions: Closed microwave digestion vessels, photometric sensor and titration apparatus, pH electrode and controlled titration temperature (solution >50 °C at titration end); references to ISO glassware standards (ISO 385, 648, 1042).
- Quality control: Procedures for EDTA standardization and blank tests, multiple determinations, calculation of total iron content, repeatability, between-laboratory precision and trueness checks. Informative annexes provide flowsheets, typical titration curves and reference titration parameters.
- Safety: The document warns of hazardous materials (notably HF) and requires appropriate health and safety practices.
Applications and who uses it
- Mining and mineral processing laboratories for routine determination of total Fe in ores, concentrates and sinter products.
- Quality control and production monitoring in pelletizing/agglomeration plants to verify feed and product Fe content.
- Analytical chemists and metallurgists implementing validated EDTA titration workflows after microwave digestion.
- Contract testing laboratories and in-house QC labs that require a standardized photometric titration method for medium–high Fe concentrations (37–72 %).
Practical benefits include repeatable, automated endpoint detection and compatibility with closed-vessel microwave digestion for efficient sample decomposition.
Related standards
- ISO 3082 - Sampling and sample preparation procedures for iron ores
- ISO 7764 - Preparation of predried test samples for chemical analysis
- ISO glassware standards referenced: ISO 385, ISO 648, ISO 1042
Use ISO 21826-1:2022 when you need a standardized, validated EDTA photometric titration workflow for medium-to-high Fe iron ores and related materials, while observing all safety and laboratory quality-control requirements.
Open preview (PDF)Iron ores — Determination of total iron content using the EDTA photometric titration method — Part 1: Microwave digestion method
