Solid-phase extraction of silver in geological samples and its determination by FAAS

A macroporous and a nonionic resin, Amberlite XAD-16 as a solid sorbent and N,N-diethyl-N'-benzoylthiourea (DEBT) as a chelating agent have been used for the selective separation and preconcentration of silver. Sorption of silver was studied in three ways: sorption on DEBT impregnated Amberlite XAD-16 by batch and column processes and sorption of Ag-DEBT complex on Amberlite XAD-16 by column process. Factors affecting the sorption and desorption of silver ion were investigated. The stripping of silver was achieved by using either sodium thiourea or sodium thiosulfate solution. The silver ion capacity of impregnated resin was found to be 11.22mg Ag+/g resin and 870 mu g Ag+/g resin for batch and column processes, respectively. It was 370 mu g Ag+/g resin for Ag-DEBT complex. The interference effects of possible co-existing metal ions and some electrolytes were investigated. The applicability of the proposed method was shown by analyzing the geological copper ore samples.