A sensitive method for the determination of gold and palladium based on dispersive liquid–liquid microextraction combined with flame atomic absorption spectrometric determination using N-(6-morpholin-4-ylpyridin-3-yl)-N′-phenylthiourea

Abstract

A new method for the determination of gold and palladium was developed by dispersive liquid–liquid microextraction separation–preconcentration and flame atomic absorption spectrometry detection. In the proposed approach, N-(6-morpholin-4-ylpyridin-3-yl)-N′-phenylthiourea (MPPT) was synthesized as a complexing agent. The complexation ability of the MPPT was explored by examining the effect of a series of heavy metal ions, including Mn²⁺, Pd²⁺, Ni²⁺, Cd²⁺, Co²⁺, Cu²⁺, Au³⁺, Pb²⁺, Zn²⁺ and Fe³⁺, using the DLLME procedure. The MPPT exhibited pronounced selectivity toward Pd²⁺ and Au³⁺ ions at different pH levels. Factors influencing the extraction efficiency and complex formation were examined, i.e. the pH of the sample solution, the concentration of the chelating agent, the extraction and dispersive solvent type and volume, the sample volume, and foreign ions, etc. Optimal conditions for quantitative recoveries were pH 5.5 for gold and pH 1.5 for palladium, 125 μL of % 0.4 MPPT, 1200 μL of methanol and 125 μL of carbon tetrachloride. The presented method showed a good linearity within a range of 30–230 and 25–200 μg L⁻¹ with the detection limits of 1.75 and 1.65 μg L⁻¹ for Au and Pd, respectively. The relative standard deviation (RSD) was below 2.8% at 50 μg L⁻¹ for both ions (n = 10). The developed method was simple, fast, cost efficient, and sensitive for the extraction and preconcentration of gold and palladium in samples of liquids (sea, stream water) and solids (stream sediment, ores, and electronic waste).