Sodium peroxide fusion for reliable determination of gold in ores and metallurgical samples

Abstract

A protocol based on peroxide fusion has been developed for the determination of Au in metallurgical samples and ores covering a wide range of concentrations and diverse mineralogies. The quantity of Na₂O₂ required was minimised, while maintaining lixiviant efficacy, by the use of mixed NaOH + Na₂O₂ fluxes. The method was shown to be particularly applicable to the determination of coarsely-particulate gold. Fusion cakes were dissolved in hydrochloric acid and then extracted using methylisobutylketone to provide concentrations appropriate for quantification by graphite furnace atomic absorption spectroscopy and to minimise interferences from dissolved salts. The protocol was tested on a variety of certified reference materials and produced results in excellent agreement (at Au concentrations ranging from 0.05 to 47 μg g^− 1) with the traditional lead fire assay method, while avoiding the health and safety issues associated with that technique.