The natural occurrence of platinum group metals, ruthenium, rhodium, and palladium as well as osmium, iridium and platinum, is very rare; making them extremely valuable.
Even a tiny difference in the already very-low platinum metal concentrations in a raw material can determine whether or not extraction is worthwhile. This is true for all forms of production, be it mining for metal ores, as a byproduct during nickel refining, recycling of electronic scrap or material recovery in spoil piles leftover from earlier platinum ore mining.
The SPECTRO MS inductively coupled plasma mass spectrometer (ICP-MS) can establish the contents of platinum metals with a high precision and sensitivity. Even determination in the range of a few micrograms per kilogram is possible.
The high sensitivity and precision have been made possible by internal standardization of the instrument. With the conventional method for the solid material analysis of platinum metals, the sample is first mixed with nickel sulfate. The mixture is then processed to form a fused bead, whereby the platinum metals accumulate in the nickel sulfate, and the rest of the sample can be removed as slag. In the next step, the bead is subjected to a laser impulse. Using this laser ablation, a portion of the material at the sample surface is transformed into a plasma that can be evaluated with an analytical instrument.
“The problem is that the amount of sample that passes into the plasma is strongly dependent on the sample matrix,” explains Willi Barger, specialist for ICP mass spectrometry at SPECTRO. “If a large portion of the sample substance passes into the plasma, then the instrument measures high concentrations. But if only a small amount is removed, then the contents are low. To minimize the resulting fuzziness, the SPECTRO MS uses nickel, the main component in the bead, as an internal calibration standard.”