SOXHLET EXTRACTION AND ACID DIGESTION METHODS FOR SILVER DETERMINATION IN SOILS BY FLAME AND ELECTROTHERMAL ATOMIC-ABSORPTION SPECTROMETRY

This paper describes the development of a soxhlet extraction method fo r the extraction of silver as silver iodide from soil, and its subsequ ent determination by atomic absorption spectrometry. Silver iodide is extracted as a double salt with potassium iodide in acetone and, after condensation, silver is measured in the extract by flame atomic absor ption spectrometry. The efficiency of this extraction was compared to a wet digestion method. Concentrated nitric acid was used for soil dig estion and silver was determined in the acid digests by electrothermal atomic absorption spectrometry. In a series of soil samples, silver r ecovery varied between 90-110%. The detection limits were mass-depende nt and, at the experimental conditions described in this work, these w ere found to be 2 mu g/kg in extracted and 3 mu g/kg in acid digested soil samples.