Separation and determination of gold from iron rich matrices by an off/on-line preconcentration system coupled to ICP-AES

Abstract

A preconcentration/separation method has been developed for the off/on-line determination by ICP-AES of gold in complex matrices, containing iron and manganese which cause severe spectral interferences on the two most sensitive Au-lines. The available automated preconcentration apparatus was modified using as absorbent the highly selective, for precious metals, chelating anion exchanger SRAFION NMRR. From the elution of this resin with 5% thiourea a nearly quantitative recovery of gold and its separation from iron, existing in percent range in the matrix, and from manganese was obtained. The validity of the developed method was tested by the determination of gold in standard reference materials from BCR, such as sewage sludge of domestic and mainly industrial origin and in a calcareous loam soil. The preconcentration procedure was synchronized with the ICP operating parameters in order to get an optimised on-line coupling of these two systems. The described process has been successfully applied to the determination of low gold contents in dissolved iron rich sediments using for the gold prospection.