MODIFIED DECOMPOSITION PROCEDURE FOR THE DETERMINATION OF GOLD IN GEOLOGICAL SAMPLES BY ATOMIC-ABSORPTION SPECTROMETRY

A method is described for the atomic absorption spectrometric determination of gold in geological samples, involving a modified digestion procedure with sequential use of HBr-Br2 and aqua regia [HCl-HNO3 (3 + 1)]. The roasted sample (approximately 700-degrees-C) was first treated with an HBr-Br2 mixture. Gold was extracted from the aqueous layer into isobutyl methyl ketone and the organic solvent containing gold was mixed with the original residue. The dried residue was again attacked with aqua regia. Gold was coprecipitated with potassium tellurite using tin(II) chloride solution. The precipitate was extracted into toluene and gold was stripped back into aqua regia solution for final nebulization into an air-acetylene flame. The method was applied to various reference materials with diverse matrices.