Gold by Aqua Regia

There are many different analytical methods available in the industry to develop geochemical targets. There are several digestion techniques that can be used depending on the end use of the data – from very weak extraction to complete dissolution. Aqua regia extractions are good for many elements including gold and base metals. ECBH experts are always available to assist you with selecting the gold (Au) analysis or assay technique that is fit for your purpose.

Aqua regia is a 3:1 mixture of hydrochloric acid and nitric acid. It is a strong oxidizing mixture that dissolves many base metal sulfide minerals as well as gold and platinum. However, it is a partial leach that leaves an undigested silicate and alumina residue as well as refractory minerals such as garnet and spinel. It is possible to vary the sample size from less than 1g up to 20 to 50g depending on the target elements and their expected concentration. Sub-ppb detection limits are possible and base metal detection limits of low ppb are common.

Aqua regia digestion can result in the partial loss of volatile arsenic and antimony. Insoluble barium and lead sulfates can precipitate when sulfide is oxidized to sulfate. This is common since aqua regia is a strong oxidizing agent.