Preconcentration of trace gold and silver on titanium dioxide nanotubes and their determination by inductively coupled plasma mass spectrometry

Based on titanium dioxide nanotubes (TDNTs) as a solid phase extraction adsorbent, a microcolumn preconcentration method coupled with inductively coupled plasma mass spectrometry was developed for the determination of trace gold and silver in environmental and biological samples. The effect of various experimental parameters such as pH, sample flow rate and volume, elution solution and interfering ions on the retention of the analytes was investigated systematically. The experimental results showed that the analytes were retained on TDNTs in the pH range of 3.0–5.0 and desorbed quantitatively with 2.0 mL of 1.0 mol L−1 HNO3 solution containing 1.5% thiourea. An enrichment factor of 100 was achieved. Under the optimum conditions, the detection limits (3σ) of this method were 0.0013 ng mL−1 and 0.018 ng mL−1 for Au and Ag, and the relative standard deviations were 2.7% and 4.1% for Au and Ag (n = 9, c = 0.5 ng mL−1), respectively. This method was applied to the determination of trace Au and Ag in a natural water sample and a certified reference material of human hair (GBW 07601) with satisfactory results.