Preconcentration and determination of trace elements with 2,6-diacetylpyridine functionalized Amberlite XAD-4 by flow injection and atomic spectroscopy

Abstract

An on-line flow injection method for the direct determination of trace elements in environmental samples is described. A mini-column packed with 2,6-diacetylpyridine functionalized Amberlite XAD-4 was used to preconcentrate and separate 8 trace metals (Cd, Co, Cu, Mn, Ni, Pb, U and Zn) from water and extracts from solid samples. The metals were eluted with 0.1 M HNO₃ directly to the detection system (either inductively coupled plasma-mass spectrometry (ICP-MS) or flame atomic absorption spectrometry (FAAS)). As well as demonstrating that the resin could be used to preconcentrate ultra-trace analytes from natural waters, it was also shown to work well at a pH of 5.5. Therefore, after treatment of sample digests with sodium fluoride, samples that contain extremely large concentrations of iron may be analysed for trace analytes without the excess iron overloading the capacity of the resin. To this end, the analytes Cd, Co, Cu and Ni were preconcentrated from acid extracts of certified soil/sediment samples and then eluted with nitric acid to be determined on-line. Limits of detection (3σ) of Cd = 0.33 µg l⁻¹, Co = 0.094 µg l⁻¹, Cu = 0.34 µg l⁻¹, Mn = 0.32 µg l⁻¹, Ni = 0.30 µg l⁻¹, Pb = 0.43 µg l⁻¹, U = 0.067 µg l⁻¹ and Zn = 0.20 µg l⁻¹ for the FI-ICP-MS system and Cd = 22 µg l⁻¹, Co = 60 µg l⁻¹, Cu = 10 µg l⁻¹ and Ni = 4.8 µg l⁻¹ for the FI-FAAS system were obtained. Analysis of certified reference materials showed good agreement with the certified values using the two methods.