Proficiency testing on the analytical control of precious metal production

Our experience of executing proficiency testing programs on the analysis of precious metals and precious metal bearing materials is summarized. Six proficiency testing programs of the ”distributed sample testing” type were carried out using samples essentially distinct from each other: (I) certified samples of fine gold and fine silver, and (II) recoverable raw (scrap and catalyst waste) containing precious metals of unknown contents. The test results were assessed using the London Bullion Market Association (LBMA) rules and by Z-criteria using the ISO/IEC Guide 43 scale. Satisfactory results were presented by all participants for the analysis of certified samples of fine gold and fine silver. The results of catalyst waste analysis agreed rather well, whereas the scrap analysis revealed an essential discrepancy in the data for some samples. The reasons for such discrepancies are discussed.