An Improved Method for Determination of Trace Silver in Geochemical Exploration Samples by Graphite Furnace Atomic Absorption Spectrometry

The chemical procedure of the HCl-HNO₃-HF-HClO₄ acids system on the electric heating plate is usually used to determine trace Ag in geochemical exploration samples using the Graphite Furnace Atomic Absorption Spectrometry (GFASS) method. Ir and Pt are usually used as the matrix modifiers. However, the thiourea serving as the medium probably leads to a large amount of precipitation with Cu, which interferes with the measurement results. Also, this dissolution method is time consuming during the analysis process and costly. In this paper it is reported that sample in water bath is dissolved by 50% aqua regia. The 50 g/L thiourea matrix modifier was added as the solution, avoiding the precipitation with Cu. The detection limit was 0.01 μg/g with good accuracy and precision. The qualified rates of internal and external examination were in agreement with the standard values. This new method simplifies the processing steps, saving time and cost, and is suitable for batch samples analyses. Furthermore, the dissolved solution of the samples was applied to determine As, Hg, Bi, Sb and other elements by the hydride generation method.