ISO 11494:2019

Overview

ISO 11494:2019 specifies an analytical procedure for the determination of platinum in platinum alloys (nominal content up to 990 ‰) using ICP‑OES (inductively coupled plasma optical emission spectrometry) with an internal standard element. Designed for jewellery and precious‑metals testing, the standard covers sample dissolution, preparation of calibration and sample solutions, measurement by ICP‑OES using an internal standard (e.g., yttrium), and calculation/reporting of results. The method is particularly applicable to alloys conforming to ISO 9202.

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Key Topics and Requirements

• Scope: determination of Pt in platinum alloys up to 990 ‰ (parts per thousand).
• Analytical technique: ICP‑OES with an internal standard (commonly yttrium).
• Sample preparation:
  • Dissolution in aqua regia (HCl and HNO3), with guidance on acid volumes and heating to remove nitrogen oxides.
  • Special handling for alloys containing >5 % Ru, Ir or W (pressure digestion or pre‑alloying with platinum‑free copper); add H3PO4 in presence of tungsten.
• Reagents and materials:
  • High‑purity reagents (HCl ~30–37 %, HNO3 ~65–70 %, H3PO4 85 %).
  • Platinum standard (min. 999.9 ‰) and analytical grade yttrium compound for internal standard.
  • Analytical balance (precision 0.01 mg) and ICP‑OES with optical resolution ≤ 0.02 nm.
• Calibration and measurement:
  • Bracketing (encadrement) calibration uses two standards nearest the expected Pt level; recommend preparing multiple standards and verifying linearity.
  • Maintain equivalent acid matrix in standards and samples; add a fixed mass of internal standard to all solutions.
  • Measurement sequence and stabilization times: instrument stabilization and timed integrations; target relative standard deviation (RSD) ≤ 0.3 % for averaged intensity ratios.
• Recommended emission lines (examples):
  • Platinum: 265.945 nm, 214.424 nm, 299.796 nm, 306.471 nm (select lines free of interferences).
  • Yttrium (internal standard): 371.029 nm, 377.433 nm, 321.669 nm.
• Reporting: follow the calculation approach described in ISO 11494:2019 (intensity ratios corrected for internal standard mass), and include details required in the test report.

Applications and Users

• Accredited jewellery and precious‑metal assay laboratories performing quality control and purity certification.
• Manufacturer QC of platinum jewellery, coins and platinum‑based components.
• Reference and materials testing laboratories needing traceable Pt quantification.
• Research groups working on platinum alloy characterization or metallurgical studies.

Related Standards

• ISO 9202 - Platinum and platinum alloys (reference to alloy definitions).
• ISO 11596 - Sampling procedures for precious‑metal articles (sampling guidance referenced by ISO 11494).

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