Overview
ISO/TR 18231:2016 - "Iron ores - Wavelength dispersive X‑ray fluorescence spectrometers - Determination of precision" provides a Technical Report of test methods to verify that wavelength dispersive X‑ray fluorescence (WD‑XRF) spectrometers deliver the precision required for iron‑ore chemical analysis. The document focuses on common sources of instrumental error and sets out procedures to measure and, where appropriate, help rectify those errors. It assumes instruments have already been optimized according to the manufacturer's instructions (two‑theta angle, pulse‑height window, detector gas environment and power supply).
Key topics and technical requirements
- Scope and assumptions: Tests target parts of WD‑XRF spectrometers likely to introduce error rather than every component; applicable to both sequential and simultaneous spectrometers unless stated otherwise.
- Frequency of testing: Suggested schedules include monthly, half‑yearly, and yearly checks depending on the test and instrument changes (see examples below).
- Counter tests:
- Counter resolution (gas‑flow proportional, scintillation, sealed gas counters), including theoretical and practical resolution calculations and acceptable performance guidance (e.g., theoretical Cu Kα resolution examples provided).
- Conductivity of gas‑flow proportional counter window and pulse‑height shift corrector operation.
- Spectrometer tests:
- Precision assessment and counting‑statistical error calculations.
- Test specimen selection and instrument operating conditions for sequential vs simultaneous spectrometers.
- Operational tests such as stability, specimen rotation, carousel reproducibility, mounting/loading reproducibility, sample holder and carousel position comparisons, angular reproducibility, collimator/detector/crystal changing reproducibility.
- Dead time and maximum usable count rate: Methods to determine detector dead time and recommend procedures for evaluating maximum count rates.
- Supporting material: Annexes include calculation methods such as coefficient of variation for duplicates.
Practical applications and users
- Laboratories performing chemical analysis of iron ores that rely on WD‑XRF for routine quality control and product specification.
- QC managers, laboratory technicians, calibration engineers, and instrument service teams who need documented test procedures for instrument validation and troubleshooting.
- Instrument manufacturers and third‑party service providers that develop maintenance, validation, and acceptance testing protocols.
- Use cases include verifying instrument readiness after maintenance, establishing routine quality assurance schedules, and confirming that measured precision meets internal or contractual limits.
Related standards and guidance
- ISO/TR 18231:2016 complements other ISO documents on chemical analysis and iron ores produced under ISO/TC 102 (Iron ore and direct reduced iron). Consult manufacturer manuals and ISO/TC 102 publications for harmonized test programs and conformity assessment guidance.
Keywords: ISO/TR 18231:2016, WD‑XRF, wavelength dispersive X‑ray fluorescence, iron ores, spectrometer precision, counter resolution, dead time, spectrometer testing, QC.