Single-Walled Carbon Nanotubes as Solid-Phase Extraction Adsorbent for the Preconcentration and Determination of Precious Metals by ICP-MS

In this paper, the potential of single-walled carbon nanotubes (SWNTs) as a solid-phase extraction adsorbent for the separation and preconcentration of trace precious metals (Au and Pd) was investigated by inductively coupled plasma mass spectrometry (ICP-MS). Experiments were performed to optimize conditions such as pH, sample flow rate, sample volume, concentration of eluent and interference of coexisting ions. Gold and palladium were quantitatively adsorbed on SWNTs in the pH range of 2.0-5.0. The retained analytes were completely eluted with 2.0 mL of 3.0% thiourea in 0.5 mol L-1 HCl solution. Under the selected conditions, the detection limits (3 sigma) of this method were 0.23 ng mL(-1) of Au and 0.06 ng mL(-1) of Pd, and the relative standard deviations (RSDs) were 5.4% and 3.7%, respectively (n=11, c=1.0 ng mL(-1)). This method was applied for the determination of trace Au and Pd in geological and water samples with recoveries of 93.6-103%.