Overview
ISO 12926:2012 specifies a wavelength-dispersive X‑ray fluorescence (WDXRF) spectrometric method for the determination of aluminium fluoride (AlF3) from fluorine content and for the measurement of trace elements in industrial-grade aluminium fluoride. The method uses pressed powder tablets prepared from milled samples and does not determine oxygen. Calibration reference materials are not specified in the standard - users must obtain suitable calibration materials.
Key topics and technical requirements
- Analytes and concentration ranges: Applicable to industrial AlF3 where concentrations fall within the ranges listed in the standard (examples include AlF3 86.5–95.75 mass %, Na 0.05–0.25 %, Si 0.001–0.14 %, P 0.001–0.02 %, S 0.01–0.6 %, Ca 0.001–0.10 %, Fe 0.005–0.05 %).
- Sample preparation:
- Two accepted approaches: addition of binder and backing method. Either may be used but preparation must match calibration material handling.
- Typical test portion: 10.0 g (users should maintain same test mass as calibration standards).
- Mill to particle size below 63 µm (typical milling times 1–4 min; shorter times increase variability).
- Use of binders (examples listed) to reduce segregation and aid tablet removal.
- Tablet formation:
- Press powdered sample into tablets using a tablet press (example pressures 20–40 ton, typical 25 ton for 20 s with 40 mm diameter).
- Use Mylar film to protect surfaces; inspect tablets for cracks and surface quality.
- Instrumental measurement:
- Use a wavelength-dispersive XRF spectrometer with vacuum path; Kα lines are preferred.
- Correct for spectral overlaps, background and instrumental drift (monitor samples recommended).
- Suggested measurement lines and settings are provided; users must follow instrument manufacturer guidance.
- Quality considerations:
- Calibration reference materials are user‑supplied; accuracy depends on matched calibration and sample mineralogy.
- Note: fluorine determination can be affected by mineralogical variation - unusual samples should be verified by an absolute method.
- Precision, reporting format and calculation procedures are included in the standard.
Practical applications and users
ISO 12926:2012 is intended for:
- Quality control and incoming inspection of industrial aluminium fluoride (AlF3) used in aluminium smelting and cast‑house processes (electrolyte acidity control, TAC).
- Metallurgical and chemical laboratories performing AlF3 trace element analysis using WDXRF.
- Producers and suppliers of AlF3 requiring routine compositional testing and batch verification.
Benefits include reproducible sample prep procedures (pressed powder tablets), guidance on WDXRF measurement, and structured reporting for regulatory and process control needs.
Related standards
- ISO 1619 - Cryolite, natural and artificial - Preparation and storage of test samples (referenced for sample handling).
- Users should consult instrument manufacturer documentation and available certified reference materials for calibration.