ISO 24181-1:2024

Overview

ISO 24181-1:2024 specifies a harmonized analytical method for the determination of non-rare earth impurities (Al, Ca, Mg, Fe, Si) in individual rare earth metals and their oxides using inductively coupled plasma atomic emission spectroscopy (ICP‑AES). It defines applicable and verified measurement ranges, sample preparation by acid digestion, calibration with matrix matching, and calculation/precision reporting to ensure reproducible quantification across testing laboratories.

Key topics and requirements

• Analytes covered: Magnesium (Mg), Aluminum (Al), Silicon (Si), Calcium (Ca), Iron (Fe).
• Applicable measurement ranges (mass fraction %):
  • Mg, Al, Si, Ca: 0.001 to 0.2
  • Fe: 0.001 to 0.5
• Verified interlaboratory ranges: Mg 0.002–0.06; Al 0.003–0.03; Si 0.002–0.03; Ca 0.004–0.08; Fe 0.003–0.03.
• Analytical technique: ICP‑AES (also called ICP‑OES) with selected emission lines and instrument settings suitable for these ranges.
• Sample preparation: Acid digestion (complete matrix dissolution). If insoluble residue remains, results are to be reported as imprecise.
• Calibration: Calibration‑curve method with matrix matching using matrix solution and stock solutions; blank/matrix used to determine LOQ.
• LOQ definition: Ten times the standard deviation of blank measurements. LOQ must be below the lower limit of the measurement range.
• Quality/precision: Includes interlaboratory test results, regression formulae for precision, and required reporting elements.
• Safety note: Method involves hazardous chemicals and procedures; users must follow relevant health and safety standards.

Practical applications and users

• Producers of rare‑earth metals and oxides: quality control, acceptance testing, process monitoring.
• Analytical laboratories: routine impurity assays using ICP‑AES and validated sample prep.
• Buyers, traders, and specifiers: contract testing and verification of material purity for commercial transactions.
• R&D and materials scientists: impurity profiling to correlate properties with trace contaminants.
• Regulatory bodies and conformity assessment: consistent method for comparative data and dispute resolution.

Benefits: improves comparability of impurity data, reduces analytical discrepancies, and supports material specification and supply‑chain transparency for rare‑earth products.

Related standards

• ISO 11885 - ICP‑OES determination of selected elements (general guidance)
• ISO 22444‑1 / ISO 22444‑2 - Rare earth vocabulary (minerals, oxides, metals)
• ISO 648, ISO 1042, ISO 3696 - Laboratory glassware and water for analytical use
• ISO 15202 series - Safety and handling of rare-earth materials

Keywords: ISO 24181-1:2024, rare earth impurities, ICP‑AES, aluminum, calcium, magnesium, iron, silicon, acid digestion, calibration curve, matrix matching, LOQ, measurement ranges.