Abstract
The determination of trace rare-earth elements (REEs) can be used for the assessment of environmental pollution, and is of great significance to the study of toxicity and toxicology in animals and plants. N, N, N′, N′-tetraoctyl diglycolamide (TODGA) is an environmental friendly extractant that is highly selective to REEs. In this study, an analytical method was developed for the simultaneous determination of 16 trace REEs in simulated water samples by inductively coupled plasma optical emission spectroscopy (ICP-OES). With this method, TODGA was used as the extractant to perform the liquid-liquid extraction (LLE) sample pretreatment procedure. All 16 REEs were extracted from a 3 M nitric acid medium into an organic phase by a 0.025 M TODGA petroleum ether solution. A 0.03 M ethylenediaminetetraacetic acid disodium salt (EDTA) solution was used for back-extraction to strip the REEs from the organic phase into the aqueous phase. The aqueous phase was concentrated using a vacuum rotary evaporator and the concentration of the 16 REEs was detected by ICP-OES. Under the optimum experimental conditions, the limits of detection (3σ, n = 7) for the REEs ranged from 0.0405 ng mL-1 (Nd) to 0.5038 ng mL-1 (Ho). The relative standard deviations (c = 100 ng mL-1, n = 7) were from 0.5% (Eu) to 4.0% (Tm) with a linear range of 4–1000 ng mL-1 (R2 > 0.999). The recoveries of 16 REEs ranged from 95% to 106%. The LLE-ICP-OES method established in this study has the advantages of simple operation, low detection limits, fast analysis speed and the ability to simultaneously determine 16 REEs, thereby acting as a viable alternative for the simultaneous detection of trace amounts of REEs in water samples.
Highlights
Rare-earth elements (REEs), according to the International Union of Pure and Applied Chemistry, are defined as including the lanthanides with atomic numbers ranging from 57 (La) to 71 (Lu), and two additional elements, Sc (21) and Y (39) [1]
The results showed that the limits of quantification (LOQs) of the method ranged from 6.3 ng mL−1 (La) to 15 ng mL−1 (Ce), with the recoveries for the spiked samples ranging from 93 to 105%
Compared with the obtained results by the method based on inductively coupled plasma mass spectrometry (ICP-MS) determinations, satisfactory results were obtained, indicating that this new method could be an alternative for the simultaneous determination of REEs
Summary
Rare-earth elements (REEs), according to the International Union of Pure and Applied Chemistry, are defined as including the lanthanides with atomic numbers ranging from 57 (La) to 71 (Lu), and two additional elements, Sc (21) and Y (39) [1]. Different methods of separation and preconcentration prior to determination by the apparatus have been reported, including ion-exchange resins [28], solid phase extraction [16,18,20,21,22,29] and cloud point extraction [24,30] These techniques still present some limitations and inconveniences for the analysis, as they are time consuming and tedious. This method has the advantages of rapidity, simplicity and sensitivity Based on this idea, we synthesized a new type of highly efficient and environmentally friendly extractant, TODGA [31], and established a liquid-liquid extraction method that can preconcentrate 16 REEs from high-content matrix elements effectively and determine them by ICP-OES simultaneously. Compared with the obtained results by the method based on ICP-MS determinations, satisfactory results were obtained, indicating that this new method could be an alternative for the simultaneous determination of REEs
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