Investigation of adverse effect of coexisting aminopolycarboxylates on the determination of rare earth elements by ICP-MS after solid phase extraction using an iminodiacetate-based chelating-resin
2019
When iminodiacetic acid chelating-resin solid phase extraction (SPE) was used for the preconcentration of rare earth elements (REEs) in river water samples around sewage treatment plant (STP), low recovery values for heavy REEs were observed. In order to find out the reason for the low recovery, in the present paper, organic ligands in the STP effluent, which may compete with iminodiacetic acids, were analyzed by GC-NPD. It was found that EDTA was contained in the STP effluent at several-100 nM level and interfered with the adsorption of REEs, especially heavy REEs (present at pM level) on the chelating-resin due to the formation of stable complexes. Therefore, acid treatment was applied to decompose EDTA molecules. As a result of acid treatment with HNO₃ and H₂O₂ at 170 °C for 4 h, all REEs were almost quantitatively recovered from the STP effluent with chelating-resin SPE with good reproducibility. After the acid treatment and subsequent 40-times preconcentration with SPE, all REEs in river water samples were precisely determined by ICP-MS at several-10 to sub pg mL⁻¹ levels.
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