DETERMINATION OF PLATINUM, PALLADIUM, IRIDIUM AND GOLD IN SELECTED GEOLOGICAL REFERENCE MATERIALS BY RADIOCHEMICAL NEUTRON-ACTIVATION ANALYSIS - COMPARISON OF PROCEDURES BASED ON AQUA REGIA LEACHING AND SODIUMPEROXIDE SINTERING

A rapid and sensitive neutron activation method for the determination of platinum, palladium, iridium and gold in rocks is described. The pr ocedure consists of thermal neutron irradiation of about 250 mg of sam ple, followed by chemical treatment of the rock, precipitation of gold and the platinum group elements with tellurium and high-resolution ga mma-ray spectrometry with a hyper-pure Ge detector, Two different meth ods were used for the chemical treatment of the rock: aqua regia leach ing and sintering with sodium peroxide. The procedures were evaluated by analysis of the certified reference material SARM-7 and the referen ce material CHR-Pt+, Sintering with sodium peroxide and precipitation with tellurium were more appropriate for the determination of Pd, Pt a nd Ir, giving results in good agreement (within +/-10%) with literatur e values, For gold, aqua regia leaching gave more accurate results (re lative errors from 0 to 6%). The detection limits for the analytical c onditions employed were 0.1 mu g kg(-1) Au, 10 mu g kg(-1) Pd, 20 mu g kg(-1) Pt and 0.2 mu g kg(-1) Ir, The procedure employing fusion with sodium peroxide was applied to the analysis of the reference material CHR-Bkg and the concentrations of Au, Pt, Pd and Ir obtained are pres ented.