The purity of precious metals is the main factor for their monetary value. Therefore, it needs to be most accurately determined when trading gold or gold metal products. Whereby contents of up to 999 ‰ are determined with the Cupellation method (fire assay) (ISO 11426). For high-purity gold (>999‰) the determination of the precious metal content is done with a different method. Here the impurities are analyzed, and the purity of the precious metal is calculated by a subtraction of the sum of all impurities in the sample from 1000 ‰.
Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES) can be perfectly used for the elemental analysis of impurities in precious metals. Due to its multi-element capability — large linear dynamic range and high sensitivity — it is the recommended analytical procedure for the analysis of contamination traces in high-purity gold. The application is described in the ISO standard 15093 as well as in the ASTM method B562-95. This report describes the methodology for the ICP-OES analysis of trace elements in precious metals. It presents typical detection limits for selected elements (as well as studies on accuracy).