ISO 15093:2020 pdf download – Jewellery and precious metals – Determination of high purity gold, platinum and palladium – Difference method using ICP-OES
1 Scope
This document specifies the analytical procedure for the determination of gold, platinum and palladium with a nominal content of and above 999 ‰ (parts per thousand). This document specifies a method intended to be used as the recommended method for the determination of gold, platinum and palladium of fineness of and above 999 ‰. For the determination of fineness of and above 999,9 ‰, modifications described in Annex B apply.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes requirements of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 11596, Jewellery — Sampling of precious metal alloys for and in jewellery and associated products
3 Terms and definitions
No terms and definitions are listed in this document.
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4 Principle
The sample is weighed and dissolved in aqua regia to prepare a 10 g/l solution (higher concentration is used for fineness of and above 999,9 ‰). The impurities are determined by ICP-OES (see Table A.1 for wavelengths), and the precious metal content is obtained by subtraction of the total content of impurities in the sample from 1 000 ‰. For the determination of fineness of and above 999,9 ‰, modifications described in Annex B shall be applied.
5 Reagents
During the analysis, unless otherwise stated, use only reagents of recognized analytical grade and only distilled water or water of equivalent purity.
5.1 Hydrochloric acid (HCl), 30 % to 37 % HCl (mass fraction).
5.2 Nitric acid (HNO 3 ), 65 % to 70 % HNO 3 (mass fraction).
5.3 Aqua regia (should be prepared just before use). Mix three volumes of hydrochloric acid (5.1) and one volume of nitric acid (5.2).
5.4 Stock solution A (shall not contain any chloride), Ag, Al, Cd, Cr, Cu, Fe, Mg, Mn (100 mg/l each) in 3 % to 7 % HNO 3 (5.2) (mass fraction). NOTE The stock solution “A” is typically prepared by mixing 10 % (of the total volume) of each 1 000 mg/l monoelemental solution with 5 % of nitric acid (5.2) (volume fraction) and making up with water. It can be kept for up to 12 months under proper storage conditions.
5.5 Stock solution B (may contain both chlorides and nitrates), Bi, Co, Ga, In, Se, Sn, Te, Ti, Zn (100 mg/l each) in 3 % to 7 % aqua regia (5.3) (volume fraction).
5.6 Stock solution C (may contain both chlorides and nitrates), As, Ni, Pb, Sb, Si, Tl, W, Zr (100 mg/l each) in 3 % to 7 % aqua regia (5.3) (volume fraction).
5.7 Stock solution D (may contain both chlorides and nitrates), Au, Ir, Pd, Pt, Rh, Ru (100 mg/l each) in 3 % to 7 % aqua regia (5.3) (volume fraction). NOTE 1 Elements which do not need to be analysed can be omitted. Other elements can be added, provided they are stable and do not generate significant interferences. NOTE 2 The stock solutions “B” to “D” are typically prepared by mixing 10 % (of the total volume) of each 1 000 mg/l monoelemental solution with 5 % of aqua regia (5.3) (volume fraction) and making up with water. They can be kept for up to 12 months under proper storage conditions.
5.8 Reference materials: gold, platinum or palladium, of 999,9 ‰ minimum purity. The content of each impurity shall be specified and taken into account in the calibration.