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Fire assay is the industry standard method for gold, platinum and palladium exploration work, because it can accommodate a larger sample size than most geochemical analyses.

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SGS has many years of experience and expertise with fire assay and our results are trusted globally. Platinum and palladium can be determined by lead collection fire assay, but the full PGE six-element suite is best determined by nickel sulfide collection fire assay. Trust SGS experts for fire assay determinations with an unparalleled level of analytical expertise.

The nickel sulfide fusion is the industry standard method used to determine platinum group elements. It is slow, expensive and involves the use of highly toxic carbonyl nickel powder. Its advantage is that, when combined with ICP-MS detection, it gives reliable results for all of the PGE at low detection limits because these metals are quantitatively extracted into the nickel button.

The method involves mixing nickel powder, sulfur, sodium carbonate, borax and sample pulp together in a crucible and fusing it at over 1000°C for an hour. As the NiS matte button forms, it extracts the PGE from the sample. The button is then crushed and dissolved and the residue is filtered to remove extraneous material, leaving the precious metal residue on the filter. There are several options for determining their concentrations:

  • Powder the button and put it into a container for INAA finish.
  • Dissolve the powdered matte button in HCl, filter off the PGE-containing residue on a membrane, dissolve it in aqua regia and finish with ICP-OES or ICP-MS analysis.
  • Dissolve the powdered matte button, add tellurate and reduce this to elemental tellurium to concentrate the PGE. The PGE are analyzed using ICP-OES or ICP-MS after the digesting of the tellurium precipitate in aqua regia.

Partner with SGS today for unparalleled nickel sulfide fire assay results.