Determination of Trace Silver in Polymetallic Ore Samples by Flame Atomic Absorption Spectrometry after Solid-Phase Extraction Using a Microcolumn Comprising Eggshell Membrane

A rapid and inexpensive method was developed for the determination of trace silver in polymetallic ore samples by use of eggshell membrane (ESM), a natural biomaterial, as the solid-phase extraction (SPE) adsorbent coupled with flame atomic absorption spectrometry (FAAS). The ESM was used for the separation/pre-concentration of silver, and the parameters affecting sensitivity, such as pH, sample flow rate, eluent volume and eluent flow rate, were carefully investigated. ESM was found to be an effective solid phase extractant for the adsorption of trace silver over a wide range of acidity from 0.02 to 0.50 mol l-1 HNO3. The sample solution in 0.4 mol l-1 HNO3 was pumped through an ESM microcolumn at the rate of 1.0 ml min-1. Silver was absorbed, and then eluted with a solution of 1.0% m/v thiourea0.5% v/v HCl. Under these optimal conditions, ESM exhibited a good enrichment efficiency for silver with a dynamic adsorption capacity of 1.7 mg g-1. The proposed method was applied to the FAAS determination of trace silver in polymetallic ores and geological reference materials, GSO-2, 3 and 5, and GSD-11, GSD-12, and the determined values were in good agreement with certified values.