Preconcentration of Ag and Pd ions using graphite oxide and 2,6-diaminopyridyne from water, anode slime and catalytic converter samples

Abstract

In this work, graphite oxide was used for the first time as an effective adsorbent for the separation/preconcentration of Ag and Pd ions in various samples prior to flame atomic absorption detection. 2,6-diaminopyridyne was used as a chelating reagent. Analytical parameters affecting the solid phase extraction of Ag and Pd such as pH, adsorption and elution contact time, centrifugation time, reagent amount, eluent concentration and volume, sample volume and matrix ions were investigated. The recovery values for Ag and Pd were found to be ≥ 95%. The adsorption and elution contact times were 60 s. The preconcentration factor of the method was 120 for a 600 mL sample using 100 mg of the graphite oxide. The elution was easily performed using 5 mL of 2.0 mol L⁻¹ HCl. The graphite oxide was reusable for 150 cycles. The detection limits of Ag and Pd were 0.39 μg L⁻¹ and 0.94 μg L⁻¹, respectively. The relative standard deviations (RSD, %) were ≤2.5%. The proposed method was validated by analysing the certified reference materials SRM 2556 (used auto catalyst pellets) and TMDA-70 lake water, and spiked real samples. The optimized method was applied for the preconcentration of Ag and Pd ions in various water (tap water, mineral water and wastewater), anode slime and catalytic converter samples.