Analysis of Precious metals and their alloys by nondestructive methods:
X-Ray analysis (XRF-analysis) –qualitative and quantitative analysis of alloys.
On the basis of X-ray analysis is
an excitation and relaxation process within the atomic electron shell. In atomic physics, fluorescence is generally defined as a two-stage process in which an atom passes into excited status by an external energy transfer and then passes back into the initial state on emission of a X-ray photon with characteristic energy level for each element. The emitted radiation of the sample hits the detector and then goes to the analyzer. Analyzer examines and processes the signal, as the results of this is the sample qualitative and quantitative content.
X-ray analysis permits to analyze samples with small area and to get results in a few minutes.
Analyses of Precious metals and their alloys by destructive methods:
The silver alloys analysis is held by EVS-EN ISO 11427:2016 “Determination of silver in silver jewellery alloys – Volumetric (potentiometric) method using potassium bromide”.
The method’s principle: The sample is dissolved in the acid. The silver content of the resulting solution is determined by titration with standard potassium bromide solution, using a potentiometric indication of the equivalence point.
The gold alloy analysis is held by EVS-EN ISO 11426:2021 „Determination of gold in gold jewellery alloys – Cupellation method (fire assay)”
The method’s principle:
The gold alloy are inquarted with silver, compounded with lead and cupelled in a cupellation furnace until a precious metal button obtained. After flattening and rolling, the silver is extracted in acid and the gold weighed.
The platinum alloy analysis is held by EVS-EN ISO 11210:2016 „Determination of platinum in platinum jewellery alloys – Gravimetric method after precipitation of diammonium hexachloroplatinate“.
The palladium alloy analysis is held by EVS-EN ISO 11490:2016 „Determination of palladium in palladium jewellery alloys- Gravimetric determination with dimethylglyoxime“.
The method’s principle:
The sample is dissolved in aqua regia. Palladium is precipitated with dimethylglyoxime. The palladium dymethylglyoxime compound is converted to metallic palladium by ignition and then is weighted.
Nickel is the most frequent cause of contact allergy in Europe. According to current legislation a precious metal article shall not be offered for sale or transferred for charge if it is coated with nickel. The presence of nickel coat is determined by XRF-analysis.
Nickel is used in various alloys as a component (white gold alloys, newsilver, etc.).
Nickel containing alloys may cause allergy, if alloy releases nickel at a rate greater than – 0,5 µg/ cm2 /week.
The Nickel release qualitative analysis is held by CR 12471.
The Nickel release quantitative analysis is held by EN 1811
The following elements: Rh, Ir, Co, Cu, Fe, Mn, Ni, Zn, Al, Sb, Sn, Bi, Pb, Cd, Re, W, Mo, Ta are determinated by Atomic-absorption spectrometry method (AAS-analysis).
The high quality chemicals and distilled water with the high degree of purity are in use for analysis.
For samples weighting there are in use analytical balances with measurement accuracy ± 0,01 mg or microanalytical balances with measurement accuracy ± 0,001 mg.
The results of analyses with the indication of used method and method’s accuracy are registrated in the Report of Analyses.