The determination of gold in geochemical samples by non-dispersive atomic fluorescence spectrometry

Abstract

Non-dispersive flame atomic fluorescence spectrometry is a very sensitive method for the determination of gold, with a limit of detection in aqueous solution of about 0.5 ng ml −1. However, the application of the technique to aqua regia digests of geochemical samples is limited by large scatter signals which are due mainly to aluminium. The use of an auxiliary lamp to provide correction for scatter is suitable for samples containing low concentrations of elements which form refractory compounds in the flame or for samples where the full sensitivity of the fluorescence technique is not required. To obtain both high accuracy and sensitivity, gold must be separated from the scattering matrix and this can be achieved by a simple extraction with a 0.1% (w/v) solution of a trioctylmethyl-ammonium salt (Aliquat-336) in di-isobutyl ketone. The use of fluorescence avoids the need for a large extraction ratio and a subsequent washing step to remove iron, as is normally required for atomic absorption measurements.