Simultaneous measurement of fifteen rare earth elements using diffusive gradients in thin films

A new method for simultaneous measurement of fifteen rare earth elements (REEs) [La (Ⅲ), Ce (Ⅲ), Pr (Ⅲ), Nd (Ⅲ), Sm (Ⅲ), Eu (Ⅲ), Gd (Ⅲ), Tb (Ⅲ), Dy (Ⅲ), Ho (Ⅲ), Er (Ⅲ), Tm (Ⅲ), Yb (Ⅲ), Lu (Ⅲ), and Y (Ⅲ)] was established in this study using the diffusive gradients in thin films (DGT) technique with Chelex^®100 binding gel. Five different types of ion exchange resins (Chelex^®100, D418, D001-cc, 001 × 7, and HSTY^®-SS) were selected for the initial investigation of their adsorption performance for REEs. The Chelex^®100 binding gel had the greatest uptake efficiencies of >95% for the fifteen REE ions, which was used for all subsequent experiments. The binding gel exhibited rapid binding dynamics to REEs in mixed solution of the fifteen REE ions. Elution efficiencies ranging from 86.5% to 93.8% for these REEs were obtained based on extraction using 2.0 M HCl. The Chelex^®100 DGT uptake of the fifteen REE ions increased linearly with the deployment time and found to be independent of pH (3–9) and ionic strength (3 mM–100 mM). The capacities of Chelex^®100 DGT for measurement of the mixed elements were determined at a range of 5.39–6.75 μg cm⁻². Application of the DGT for soil analysis showed that Chelex^®100 DGT was a useful tool in simultaneous measurement of the fifteen REE ions, even in a soil with high concentrations of REEs. This study demonstrated the advantage of Chelex^®100 DGT in simultaneous measurement of the fifteen REE ions due to high uptake efficiencies and a wide tolerance to environmental interference.