Analysis Methods and Instruments:
In our laboratory routine analysis is accomplished by using standard wet chemical analysis such as gravimetry, volumetry and electrogravimetry.
Extraction of the Precious Metals:
For the analysis of precious metals like gold (Au), silver (Ag), platinum (Pt) and palladium (Pd), we run with the well-established fire assay (Docimacy) method. This method includes the melting and extraction processes. Samples containing precious metals are mixed with flux and suitable collecting material like lead (Pb) in earthen crucibles. The crucibles are put in melting furnace and heated at 1000 -1100°C for certain period of time. Melting process takes place and the precious metals are extracted in the lead as a bead.
The resulting bead is analyzed by titration or by ICP-OES for (Ag) or a gravimetric determination for Au (rolling the collected gold metal into strips). Other collectors such as copper (Cu) or nickel sulfide (NiS) are often used for rhodium (Rh), iridium (Ir) and ruthenium (Ru). Further enrichment processes are also used upon the customer’s request and feasibility.
Analysis by Inductively Coupled Plasma – Optical Emission Spectrometry (ICP-OES):
We use inductively coupled plasma atomic emission such as Optical Emission Spectrometry (OES) with spark excitation (spark) and plasma excitation (ICP-OES). We are using three different types of ICP-OES instruments namely axial view plasma with CCD detector (Iris Advantage, Thermo), radial view plasma with CCD detector (Arcos, SPECTRO) and Photomultiplier tubes (Modula, SPECTRO). Depending on the sample material, elements of interest and their concentration, we select the appropriate method. The concentration of precious metals less than 1 ppm (µg/g) can be analyzed.
Analysis by X-Ray Fluorescence Spectrometry (XRF):
By means of a wavelength dispersive x-ray fluorescence spectrometer (Panalytical) we analyse all the precious metals collected in Cu (as copper beads), after recasting in copper, by using special calibrated methods. To verify the accurate results, natural and synthetic reference materials are used. Depending on the size of the sample, pre-treatment and elements to be analyzed, the concentration ranges from ca. 1-2 ppm up to 100% can be analyzed.
Analysis by Inductively coupled Mass Spectrometer (ICP-MS): :
A wide range of different matrices sample can be analysed by ICP-MS.
Myint Myint Sein, Wolfgang van Leeuwen and Peter Glörfeld (2017) Combination of Fire Assay and Modern Instrumental Techniques for Precious Metals Analysis, In: Production and Recycling of Non-Ferrous Metals: Saving Resources for a Sustainable Future, European Metallurgical Conference EMC 2017, Vol. 4, 1785 – 1796.