A PROCEDURAL MODIFICATION FOR ENHANCED RECOVERY OF PRECIOUS METALS (AU, PGE) FOLLOWING NICKEL SULFIDE FIRE ASSAY AND TELLURIUM COPRECIPITATION - APPLICATIONS FOR ANALYSIS OF GEOLOGICAL SAMPLES BY INDUCTIVELY-COUPLED PLASMA-MASS SPECTROMETRY

Recovery of precious metals has been improved to approximately 100% (except for Au approximately 90% and Os approximately 65%) employing screw-capped Teflon(R) bombs (Savillex(R)) for dissolution of nickel sulphide fire assay beads, and for dissolution of the tellurium precipitate. Relative standard deviations for Ru, Rh, Pd, Ir, and Au are less-than-or-equal-to 5%, for Pt 9%, and for Re and Os less-than-or-equal-to 30%. The procedural modification avoids NiS button crushing, and open beaker evaporation, and reduces reagent volumes by 6 times for dissolution of NiS button and by 2.5 times for the tellurium precipitate, thereby minimizing contamination during preconcentration. The technique also ensures full retrieval of tellurium precipitate by replacing filter system with centrifuge tubes. This study indicates that loss of precious metals in NiS fusion process is not significant. The enhanced recovery permits analysis of geological materials for low level PGE and gold.