Overview
ISO 13548:2025 specifies a laboratory procedure for the determination of fluorine (F) in copper and zinc sulfide concentrates using sodium hydroxide (NaOH) fusion followed by detection with a fluoride ion selective electrode (FISE). The method leaches fluoride ions from the NaOH fusion, masks potential interfering ions via a complexing agent and pH control, and quantifies fluoride by electrode measurement calibrated against sodium fluoride standards. The standard includes guidance on sampling, reagents, apparatus, calibration, precision and reporting. A trueness assessment is provided in Annex C.
Key technical topics and requirements
- Scope and applicability
- Applicable to fluorine mass fractions in:
- Copper concentrates: 0.008 % to 0.3 %
- Zinc concentrates: 0.005 % to 0.1 %
- Aluminium content up to 4.5 % has no effect; higher Al may affect results.
- Analytical principle
- Decompose test portion by NaOH fusion, leach fluoride, mask interferences, measure with FISE.
- Reagents and standards
- Use analytical-grade reagents and ISO 3696 grade 2 water.
- Calibrate with sodium fluoride (NaF) working standards (1 000 mg/L, 100 mg/L, 10 mg/L).
- Apparatus essentials
- Fluorine-free glassware/equipment, combined or single fluoride ion selective electrode and reference electrode, nickel/zirconium crucibles, platinum dish, balances, pH meter, muffle furnace, magnetic stirrer.
- Procedure highlights
- Duplicate determinations; prepare laboratory and test samples per ISO 12743 and ISO 9599 where applicable.
- Prepare leach solutions, condition and stabilize the electrode, control temperature and pH, plot calibration graph and calculate fluorine mass fraction.
- Quality and reporting
- Includes procedures for blanks, calibration, precision expression, interlaboratory precision and trueness checks (Annex C).
- Safety warning regarding hazardous materials and safe laboratory practice.
Practical applications and users
- Who uses ISO 13548:2025:
- Analytical chemists in mining, metallurgical laboratories and concentrate quality control.
- QA/QC managers monitoring fluorine content for smelting process control, product specification compliance, and environmental reporting.
- Laboratories performing routine and forensic analysis of copper and zinc concentrates.
- Practical benefits:
- Reproducible, standardized method for regulatory compliance and process optimisation.
- Clear guidance on interference control (notably aluminium) and calibration for reliable results.
Related standards
- ISO 3696 - Water for analytical laboratory use
- ISO 9599 - Determination of hygroscopic moisture content of the analysis sample
- ISO 12743 - Sampling procedures for determination of metal and moisture content
Keywords: ISO 13548:2025, fluorine determination, fluoride ion selective electrode, sodium hydroxide fusion, copper concentrates, zinc concentrates, FISE, analytical method, NaF standards, aluminium interference.