Overview
EN ISO 11494:2019 - "Jewellery and precious metals - Determination of platinum in platinum alloys - ICP‑OES method using an internal standard element" - specifies an analytical ICP‑OES procedure for measuring platinum content in platinum alloys with nominal platinum content up to 990 ‰ (parts per thousand). The method uses an internal standard (typically yttrium) and a bracketing calibration approach. It applies to jewellery and precious‑metal alloys, including those referenced in ISO 9202.
Key topics and technical requirements
- Principle: Dissolve accurately weighed samples in aqua regia, add an internal standard, and measure the ratio of platinum emission intensity to internal standard emission by ICP‑OES using bracketing calibration.
- Scope: Platinum alloys up to 990 ‰; minor method modifications described for alloys containing Ru, Rh, Ir or W.
- Reagents: Analytical grade HCl (30–37 %), HNO3 (65–70 %), high‑purity Pt (≥999.9 ‰), yttrium compound for internal standard, high‑purity copper (Pt‑free) and orthophosphoric acid for tungsten cases.
- Equipment: ICP‑OES capable of simultaneous measurement of Pt and the internal standard with minimum optical resolution 0.02 nm; analytical balance with 0.01 mg readability.
- Calibration & standards:
- Bracketing uses two standards nearest expected sample concentration; recommended to prepare at least three for linearity checks.
- Example standard masses listed (approx. 45–100 mg Pt) for preparing calibration solutions.
- Internal standard solution: ~6 mg/L yttrium (typical preparation given).
- Sample preparation:
- Typical sample mass: ~100 mg dissolved in aqua regia and adjusted to precise mass/volume.
- Matrix matching and consistent acid concentration between calibration solutions and sample solutions are required.
- Alloys with >5 % Ru/Ir/W may require pressure dissolution or preliminary alloying with Pt‑free copper; add orthophosphoric acid when tungsten is present.
- Measurement: Simultaneous measurement of Pt and internal standard emission lines, appropriate background correction, clean sample introduction system and stabilized plasma.
- Quality: Calculation method, repeatability, and test report content specified.
Applications and who uses this standard
- Quality control and assay testing in jewellery manufacturers, assay offices, precious‑metal refineries and laboratories.
- Compliance testing for hallmarking and certification of platinum jewellery and components.
- Analytical laboratories performing elemental analysis of platinum alloys for trade, customs, and materials verification.
Related standards
- ISO 9202 - reference for platinum alloy compositions.
- ISO 11596 - sampling of precious metal items (sampling procedure referenced).
- EN ISO 11494:2019 supersedes EN ISO 11494:2016.
Keywords: EN ISO 11494:2019, platinum determination, ICP‑OES, internal standard, yttrium, platinum alloys, jewellery testing, aqua regia dissolution, bracketing calibration.
