Overview
ISO/TR 4688-1:2017 - "Iron ores - Determination of aluminium - Part 1: Flame atomic absorption spectrometric method" specifies a laboratory procedure for determining the mass fraction of aluminium in iron ores, concentrates and agglomerates (including sinter). The method uses flame atomic absorption spectrometry (AAS) after chemical decomposition and is applicable to aluminium contents from 0.1 % to 5.0 % (mass fraction). This document is published as a Technical Report and replaces the earlier ISO 4688-1:2006 edition.
Key Topics and Requirements
- Analytical principle: Sample decomposition with hydrochloric and a small amount of nitric acid; silica dehydration by evaporation; residue ignition and removal of silica with hydrofluoric and sulfuric acids; fusion with sodium carbonate; dissolution and aspiration into a dinitrogen oxide/acetylene flame AAS. Results are obtained by comparison with calibration solutions.
- Scope and range: Valid for natural iron ores, concentrates and agglomerates with Al between 0.1 % and 5.0 %.
- Sampling & sample prep:
- Use a laboratory sample ground to minus 100 µm (minus 160 µm for ores with significant combined water or oxidizable compounds).
- Predry test samples at 105 °C ± 2 °C (see ISO 7764 for guidance).
- Typical test portion ~1 g, weighed to 0.0002 g.
- Reagents & calibration: Analytical-grade reagents only (HCl, HNO3, HF, H2SO4, Na2CO3). Includes preparation of a 500 µg Al/ml standard, background solution and a series of calibration solutions.
- Instrumentation & performance criteria:
- AAS equipped with a dinitrogen oxide/acetylene burner.
- Instrument sensitivity: absorbance of highest calibration solution ≥ 0.30.
- Linearity: slope in top 20 % of range ≥ 0.7 × slope in bottom 20 %.
- Stability: standard deviation limits for repeat measurements (specified in the report).
- Example instrument settings provided (Al lamp 25 mA, wavelength 396.2 nm, N2O 13.8 l/min, C2H2 6.6 l/min).
- Quality control: Parallel blank and certified reference material (CRM) analysis required; at least duplicate independent determinations.
- Safety: Method involves hazardous reagents (HF, strong acids) and flammable gases - follow manufacturer and laboratory safety procedures (wear appropriate eye protection, follow flame ignition instructions).
Applications and Users
This standard is intended for:
- Analytical and metallurgical laboratories performing aluminium content analysis in iron ore for quality control and process monitoring.
- Mining companies, ore concentrators and agglomeration/sinter plants requiring reliable AAS-based aluminium assays.
- Laboratories preparing calibration, QA/QC documentation and regulatory or commercial reporting for iron ore chemistry.
Related Standards
Keywords: ISO/TR 4688-1:2017, aluminium determination, iron ores, flame atomic absorption spectrometry, AAS, sample preparation, calibration, quality control.