Acid Digestion of Chromium Ores in Multiwave 7101, 7301, and 7501 for the Determination of the Metal Content with ICP Analysis

In the mining industry there is a large demand for fast routine analysis: In prospecting for new mining projects or in developing and maintaining existing mines, large numbers of mineral samples have to be analyzed quickly. These samples consist of ore and dead rock of varying ratio and are analyzed for geochemical lead elements to find or follow the geological formations that allow the most profitable mining operation.

For the challenging chromium ore analysis, classical methods involving fusion with inorganic salts are widely used as sample preparation for XRF, and classical photometric, gravimetric, and electrochemical methods.

Due to the stability of the generic chromite mineral, sample preparation – either fusion or acid digestion - is rather challenging. Weathering processes, which may be different for chromium ores from different origins, strongly influence the stability of the chromite.

Nowadays, ICP-OES and ICP-MS are more and more used, due to their higher potential for sample throughput. Acid digestion is very well suited as quick and reliable sample preparation for these techniques.

The method described in the following suits for the samples studied. However, depending on the source of the samples their composition may vary and require some modifications e.g. to the acid mixture. In any case, it may be used as a starting point.