Alternatives to the Fire Assay Procedure for the Preparation of Automobile Catalyst Samples Prior to Analysis

摘要

To ensure reliable results for precious metal (PM) determinations, where the metals are unevenly distributed through the matrix, adaptations of the fireassay procedure are normally used for sample preparation. Fire assay for precious metals usually refers to a process in which the assay portion of a sample (usually from 10-30 g) is heated with a flux containing either litharge or nickel sulphide. The complete process is complex, very time-consuming and labour intensive, and so alternative methods of sample preparation have been sought for many years (1). An open-beaker digestion method (I), a microwaveassisted pressure digestion method (II) and a sodium peroxide fusion method (III) are described for the dissolution of automobile exhaust catalyst samples prior to their analyses for platinum, palladium and rhodium by ICP-MS. Sample sizes varied between 0.1 and 0.25g. Analyses were performed on a Perkin Elmer-Elan 6000 ICP-MS with indium and iridium as internal standards. With Methods I and II, good recoveries (-100pecent) were achieved for platinum and palladium, but the rhodium recoveries (-90pecent) were unsatisfactory. However, with Method III, excellent recoveries (-100pecent) were found for all three elements and its introduction led to a reduction in cost (labour and materials) from