ISO 11494:2019 Jewellery and precious metals – Determination of platinum in platinum alloys一ICP-OES method using an internal standard element

ISO 11494:2019 Jewellery and precious metals – Determination of platinum in platinum alloys一ICP-OES method using an internal standard element. This document describes an analytical procedure for the determination of platinum in platinum alloys with a nominal content tip to 990 O,/ (parts per thousand), including alloys according to Iso 9202. 2 Normative references There are no normative references in this document. 3 Terms and definitions No terms and definitions are listed in this document. ISO and IEC maintain terminological databases for use in standardization at the following addresses: — ISO Online browsing platform: available at https://www.isoorg/obp — IEC Electropedia: available at httpJ/www.electropedia.org/ 4 Principle At least two accurately weighed samples are dissolved in aqua regia and made up to an exactly weighed mass. These sample solutions are mixed with the internal standard and made up to the standard measuring volume. Using ICP-OES, the platinum content of the sample solution is measured by comparison of the ratio intensities of the spectral emission of platinum and appropriate internal standard (e.g. yttrium) line(s) with the ratios for solutions containing known masses of platinum and internal standard (e. g. yttrium) using the bracketing method. Minor modifications are required when the alloy contains ruthenium, rhodium, iridium, or tungsten. 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 (lid), approximately 30 % to 37 % IIC1 (mass fraction). 5.2 Nitric acid (HNO3), approximately 65 % to 70 % HNO3 (mass fraction). 5.3 Platinum (Pt) of 999,9 %o minimum purity; if a lower platinum content (e.g. 999,5 %o) is used, appropriate corrections shall be applied. 5.6 Orthophosphoric acid ([13P04), 85 % (mass fraction). 6 Equipment 6.1 Customary laboratory apparatus. 6.2 ICP-OES, capable of simultaneously measuring the platinum and the internal standard emission lines with a minimum optical resolution of 0,02 nm. 6.3 Analytical balance, with a reading accuracy of 0,01 mg. 7 Sampling The sampling procedure should be performed in accordance with Iso 11596. 8 Procedure WARNING — Suitable health and safety procedures should be followed. 8.1 Internal standard solution Dissolve approximately 20 rng YCl36H2O (5.4) in 200 ml water and make up to 1 000 ml with water. Alternatively, prepare a solution in order to obtain a concentration of approximately 6 mg/l of yttrium. Due to the sensitivity of the instrument, the concentration may be changed to achieve...