Determination Of Rare Earth Elements Research Articles

A Feasibility Study of Rare-Earth Element Vapor Generation by Nebulized Film Dielectric Barrier Discharge and Its Application in Environmental Sample Determination.

The feasibility of 16 types of rare-earth elements (REEs) containing Sc, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu vapor, generated simultaneously, was demonstrated by nebulized film dielectric barrier discharge (NFDBD) in this work. Note that this is the first report on the simultaneous vapor generation of 16 types of REEs, which previously was difficult to realize. Combining it with inductively coupled plasma-mass spectroscopy (ICP-MS) as the sampling technique, a 4-fold to 10-fold improvement in the detection limits (LODs) of the REEs was observed, compared with the conventional solution nebulization, and no obvious interferences from other metal ions and the mutual interferences between REEs at the mg L-1 level were found. Compared with ultrasonic nebulization, microconcentric (MCN) and membrane-desolvation (Aridus) and electrothermal vaporization (ETV) for REEs sampling, this NFDBD sampling technique operates not only with low cost and low power, but also without any requirement of extra reagents and easy coupling with flow injection for volume limited samples. Under optimized conditions, the relative standard deviation (RSD) of 16 types of REEs determined at 5 μg L-1 was between 0.2% and 1.9%, and the LODs of REEs were between 0.002 ng L-1 and 0.422 ng L-1, depending on the element. This technique provides an alternative green and highly efficient vapor generation approach for the determination of REEs in environmental samples, especially in natural water.

Determination of rare earth elements by inductively coupled plasma-mass spectrometry after dispersive solid phase extraction with novel oxidized graphene oxide and optimization with response surface methodology and central composite design

A novel oxidized graphene oxide (OGO) material was prepared and employed for the dispersive solid phase extraction (d-SPE) of rare earth elements (REEs) in drinking water and nuts followed by inductively coupled plasma mass spectrometry (ICP-MS) determination. The novel material was characterized by Brunauer–Emmett–Teller (BET) surface area analysis, X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Fourier transform-Infrared spectroscopy (FT-IR). Response Surface Methodology (RSM) with a Central Composite Design (CCD) and Derringer's type Desirability Function were employed for the optimization of factors that could possibly influence the extraction recovery. Response surfaces charts illustrated the effects of the examined parameters and their interactions. Under the optimum conditions, the detection limits ranged between 0.03 and 1.08 ng L−1 and the limits of quantification range between 0.09 and 3.26 ng L−1. The relative standard deviations for intra-day repeatability (concentration = 50 ng g−1, n = =5) and the inter-day repeatability (concentration = 50 ng g−1, n = =5 × 3) were 4.2–6.2% and 6.2–7.6%, respectively. The sample preparation procedure with the oxidized graphene oxide nanoparticles was simple and fast while it provided good enrichment factors and extraction recoveries. The method was successfully applied for the determination of trace REEs in almonds, peanuts and walnuts as well as tap and mineral water.

Determination of rare earth elements in seawater samples by inductively coupled plasma tandem quadrupole mass spectrometry after coprecipitation with magnesium hydroxide

Coprecipitation with magnesium hydroxide was investigated as a pretreatment method for the determination of rare earth elements (REEs) in seawater samples, both for separation of the salt contents and for the enrichment of REEs. The precipitate of magnesium hydroxide was collected on a syringe filter and then subjected to the on-line measurement of REEs by an inductively coupled plasma tandem quadrupole mass spectrometer (ICP-MS/MS). Coprecipitation resulted in a separating rate of over 99% for salt contents, while the on-line measurement of REEs in the magnesium hydroxide provided an enhancement factor of 130-fold for the transient peak height of signal intensities. Mass-shift mode was applied to the measurement of REEs by ICP-MS/MS, where each isotope of the REEs was permitted to pass the first QMS and to react with oxygen gas in the reaction cell so as to form a monoxide ion, which was permitted to pass the second QMS and then measured by the detector. Mass-shift to monoxide ion effectively removed the spectral interferences in the measurement of REEs and permitted the correct determination of REEs in seawater samples. Detection limits were calculated based on the results of 10-set of the replicated blank test, which were low enough for the determination of REEs in natural seawater samples. The effectiveness of the present method was confirmed by the analysis of three certified reference materials of seawater, i.e. CASS-4, CASS-5, and NASS-6.

On the modeling of heavy metals and rare earth elements adsorption on colloidal carbon-based nanoparticles

Acid-base and metal ions adsorptive properties of colloidal carbon-based nanostructured materials, bearing a variable number of oxygen-containing functional groups at the surface, were investigated and modeled. Hydrophilic carbonaceous nanoparticles (HNPs) with uniform dimensions and a good grade of dispersion in water, were obtained through the oxidation of a carbon black with nitric acid, at a temperature of 100 °C, for different reaction times (2–24 h). The acid-base properties of the functional groups were evaluated in water suspension by potentiometry and infrared spectroscopy. By means of X-ray fluorescence, infrared spectroscopy and differential pulse voltammetry the interaction properties of HNPs with Cd2+, Zn2+, Pb2+ and selected Ln3+ ions have also been investigated. The experimental data, collected in the 2.0–7.0 pH range, suggest that the adsorption of metal ions on HNPs is controlled by chemical adsorption involving the strong complexation of metal ions with the carboxylic groups on the surface of HNPs. Particularly, the high complexation of Ln3+ ions opens the exploitation of HNPs in solid phase extraction for preconcentration, separation and determination of rare earth elements and actinides.

Calibration strategies for the direct determination of rare earth elements in hard disk magnets using laser-induced breakdown spectroscopy

This study is dedicated to the direct determination of base (B and Fe) and some rare earth elements (REE; Dy, Gd, Nd, Pr, Sm and Tb) in hard disk magnets. Five calibration strategies were tested and compared. Two of them are related to multivariate calibration: multiple linear regression (MLR) and partial least squares (PLS). Both presented adequate trueness values within a range of 80–120% for almost all analytes. The only exception was Tb, which was probably due to matrix effects. The use of MLR and PLS permits the testing of calibration models in the presence of interference, but matrix effects are not corrected. Because of this, three other univariate calibration methods were also tested and compared: multi-energy calibration (MEC), one-point gravimetric standard addition (OP GSA) and two-point calibration transfer (TP CT). These three calibration approaches permit matrix effects corrections, but an appropriate selection of the blank and standard is mandatory. The standard error obtained ranged from 0.01 to 6% using these univariate calibration methods.

Potentiometric Sensors and Multisensor Systems for the Determination of Lanthanides

Problems of the development of potentiometric sensors and multisensor systems for the determination of rare-earth elements in aqueous solutions are considered. The efficiency of the approach to the fabrication of sensors based on the application of substances and regularities used in solvent extraction is shown. Possibilities of multisensor systems for the selective determination of individual lanthanides in complex mixtures are demonstrated.

Biogeochemical Cycle of Lanthanides in a Light Rare Earth Element-Enriched Geological Area (Quebec, Canada)

This work investigated a rare earth element (REE) natural biogeochemical cycle in an area with a light rare earth element (LREE)-rich ferrocarbonatite intrusion. An REE determination in this geological environment allowed us to trace REE natural transfers in order to better manage future REE mining exploitations. Our findings suggest that although REE concentrations in abiotic compartments (soil and freshwater systems) and biotic samples (terrestrial and aquatic plants) were low, the LREE fractionation observed in the parent material was maintained along compartments. Additionally, Nd anomalies observed in the sediment pore water suggest a potential different biogeochemical cycle of this element in aquatic systems. According to the potential bioaccumulation of REEs in the organisms of two studied plants belonging to terrestrial and aquatic compartments, Equisetum arvense L. and Typha latifolia L. (respectively), we observed that REEs were not accumulated and that they showed limited REE transfer inside plants, but with an increased uptake of Eu relative to the other REEs. Our results indicated a low mobility and transfer of REEs from REE-rich bedrocks in a natural area toward terrestrial and freshwater systems, but also pointed to a dilution of the REE content in the different compartments, maintaining the LREE fractionation. Our findings provide new knowledge about the REE biochemical cycle in a natural area (from rocks to plants) and represent a starting point for an environmentally friendly exploitation of future REE mining areas.

Happy Jack Uraninite: A New Reference Material for High Spatial Resolution Analysis of U‐Rich Matrices

There is currently a lack of well‐characterised matrix‐matched reference materials (RMs) for forensic analysis of U‐rich materials at high spatial resolution. This study reports a detailed characterisation of uraninite (nominally UO2+x) from the Happy Jack Mine (UT, USA). The Happy Jack uraninite can be used as a RM for the determination of rare earth element (REE) mass fractions in nuclear materials, which provide critical information for source attribution purposes. This investigation includes powder X‐ray diffraction (pXRD) data, as well as major, minor and trace element abundances determined using a variety of micro‐analytical techniques. The chemical signature of the uraninite was investigated at the macro (cm)‐scale with micro‐X‐ray fluorescence (µXRF) mapping and at high spatial resolution (tens of micrometre scale) using electron probe microanalysis (EPMA) and laser ablation‐inductively coupled plasma‐mass spectrometry (LA‐ICP‐MS) analyses. Based on EPMA results, the uraninite is characterised by homogeneous UO2 and CaO contents of 91.57 ± 1.49% m/m (2s uncertainty) and 2.70 ± 0.38% m/m (2s), respectively. Therefore, CaO abundances were used as the internal standard when conducting LA‐ICP‐MS analyses. Overall, the major element and REE compositions are homogeneous at both the centimetre and micrometre scales, allowing this material to be used as a RM for high spatial resolution analysis of U‐rich samples.

Comparison of different spectral resolution ICP-OES spectrometers for the determination of rare earth elements

This study investigates possible mutual spectral interferences of REEs for three commercially available spectrometers with different spectral resolutions. Comprehensive spectral interference data were obtained by using model solutions of REEs and spectral interference profiles of the most frequently used analytical lines are presented. The interference factors were calculated for line overlap correction and to confirm the effectiveness of the corrections, and model samples containing mixtures of rare earth elements were analyzed. This approach was useful only for spectrometers with low spectral resolution where the spectral interferences were found to be significant. As was expected, considerably better results were obtained by spectrometers with a high spectral resolution, as such corrections were unnecessary. The certified reference material REE-1 (the Strange Lake mine, Quebec, Canada) was used as a real sample representing REE-containing ore. Our results for both types of spectrometer confirm the assumption that high-spectral-resolution spectrometers provide better and more reliable results than low-spectral-resolution spectrometers with corrective factors. Nevertheless, the use of correction factors for the studied analytical lines does lead to improved results in many cases.

Determination of rare earth elements in environmental samples with high concentrations of barium by quadrupole inductively coupled plasma mass spectrometry

This paper proposes a new method of sample preparation for the determination of rare earth elements (REE) by quadrupole inductively coupled plasma mass spectrometry (Q-ICP-MS) in challenging environmental samples with high Ba concentrations. The method consists in adding 10% (v/v) sulfuric acid to the wet sample digest, obtained after acid decomposition in an open system, in order to precipitate and separate BaSO4. The removal of BaO interference in Eu isotopes was efficient for Ba concentrations in solution higher than 0.1 mg L−1. The methodology was applied to asphalt pavement and the crushed stone used to produce it. Accuracy was assessed using two certified materials, NIST 688 Standard Reference Material of basalt rock and Geological Survey G2 granite, resulting in acceptable recoveries. Additionally, all samples were decomposed by fusion, and the concentrations of major elements and Eu were determined by inductively coupled plasma optical emission spectrometry (ICP OES). Eu results were in agreement with the proposed methodology, and limits of detection for REE varied from 0.003 mg L−1 (Lu) to 0.010 mg L−1 (Gd). The NASC normalized profiles of REE in the crushed stone showed a positive Eu anomaly, that was not observed in the asphalt sample. As well, the latter was enriched in heavy REE (Tb-Lu), suggesting a loss of carbonatite minerals, consequently to the weathering of the pavement.

Study on the determination of rare earth elements in coal ash by ICP-MS

In this paper, an analytical method for the determination of rare earth elements in coal ash by mixed acid decomposition-inductively coupled plasma mass spectrometry was established. Using this method, the content of 15 rare earth elements in coal ash can be detected accurately, with the detection limit being 0.007–0.033 μg·g−1, and the precision (RSD, n = 6) less than 5.0%. This method was used to test the coal ash of different commercial coals. The results show that the light rare earth elements in coal ash account for 75.66%–82.61% of the total rare earth elements, among which, the total amount of rare earth elements in Yitai coal after being ashed is significantly lower than that of other coals.

Feathers of Humboldt penguin are suitable bioindicators of Rare Earth Elements

Rare earth elements (REEs), also called lanthanides, are emerging contaminants worldwide, due to their unique physical and chemical characteristics that make them essential in a variety of industrial applications. However, there is still a gap in the knowledge of occurrence and accumulation of REEs in biota, and no investigations have yet been performed in penguin feathers, which have already been widely utilized as a non-invasive tool for the biomonitoring of trace elements.The concentrations of 16 REEs were investigated in a colony of Humboldt penguins (Spheniscus humboldti) housed at the Acquario di Cattolica (Italy). Multielement determination of REEs was performed by an Inductively Coupled Plasma-Mass Spectrometer after a microwave digestion of feathers. As this colony lives indoors in a controlled environment, it was the ideal choice for studying lanthanide occurrence in penguin feathers. Since there is a strict link between metal levels in feathers and the diet of penguins, their food (capelin) was also tested for REEs.Chondrite normalized values revealed the same pattern for REEs in feathers and fish, but REE concentrations were an order of magnitude higher in penguin feathers, demonstrating the suitability of this tissue as a bioindicator of REEs.

Comparison of methods for the geochemical determination of rare earth elements: Rock Canyon Creek REE–F–Ba deposit case study, SE British Columbia, Canada

Using the Rock Canyon Creek carbonate-hosted rare earth element (REE)–F–Ba deposit as an example, we demonstrate the need for verifying inherited geochemical data prior to reinterpretation. Inherited La, Ce, Nd and Sm data obtained by pressed pellet X-ray fluorescence (XRF), and La and Y data obtained by aqua regia digestion inductively coupled plasma atomic emission spectroscopy (ICP-AES) for more than 300 drill-core samples were analysed in 2009 and were subsequently compared to sample subsets re-analysed using lithium metaborate-tetraborate (LMB) fusion ICP mass spectroscopy (ICP-MS), Na 2 O 2 fusion ICP-MS, and LMB fusion-XRF. We determine that LMB ICP-MS and Na 2 O 2 ICP-MS accurately determined REE concentrations in control reference materials (CRM) SY-2 and SY-4, and provided precision of about 10%. Fusion-XRF was precise for La, Ce and Nd at concentrations greater than ten times the lower detection limit; however, accuracy of this method was not established because REE concentrations in SY-4 were below the lower detection limit. Analysis of the sample subset revealed substantial discrepancies for Ce concentrations determined by pressed pellet XRF in comparison to those determined by other methods due to Ba spectral interference. Samarium, present in lower concentrations than other REE that were determined, was consistently underestimated by XRF methods relative to ICP-MS methods. This may be the result of Sm concentrations approaching the lower detection limits of XRF methods, elemental interference or inadequate background corrections. Aqua regia dissolution results, reporting only for La and Y, are underestimated relative to the other methods. We highlight the importance of selecting the most appropriate analytical method and reference materials for determining the REE content of mineralized rock which may be several orders of magnitude higher than that of typical host rock.

Determination of Rare Earth Elements in Natural Water Samples by Rapid Sequential High-Resolution Continuum Source Flame Atomic Absorption Spectrometry (HR CS FAAS) and inductively Coupled Plasma-Mass Spectrometry (ICP-MS)

A method was developed to sequentially assay ten rare earth elements by high-resolution continuum source flame atomic absorption spectrometry. The rare earth elements Nd, Sm, Eu, Tb, Ho, Er, Tm, Yb, Y, and Sc were assayed in environmental water samples which were also analyzed by a reference inductively coupled plasma-mass spectrometry protocol. The samples did not require pretreatment or preconcentration. Interferences for the method were evaluated. Experimental parameters, including the flame composition, burner height, ionization buffers and number of pixels, were optimized. The volume necessary to run measurements in triplicate was only 15 mL per sample. The accuracy, precision and linear range were evaluated. The limits of detection ranged from 0.003 to 0.473 µg mL−1 for the most sensitive (Yb) to the least sensitive (Tb) element.

Evaluating Laser-Induced Breakdown Spectroscopy Sensor Technology for Rapid Source Characterization of Rare Earth Elements

A prototype laser-induced breakdown spectroscopy (LIBS) sensor is tested for the determination of rare earth elements (Eu and Yb) in liquid and solid samples. The sensor head, built using a monolithic passively Q-switched (PQSW) Nd:YAG laser, produced a 1064 nm laser beam with ns pulses and an energy of 4.2 mJ. The measurements show good calibration linearity for both Eu and Yb with R2 values above 0.99 for all analyzed spectral lines in liquid and solid samples. Limits of detection (LODs) obtained were as low as 1 ppm, which are comparable to or better than those reported previously by using table top actively Q-switched systems. This study aims to develop a high sensitivity, field deployable sensor for characterizing existing and new sources of rare earth elements.

Magnetic ZnFe2O4 nanotubes for dispersive micro solid-phase extraction of trace rare earth elements prior to their determination by ICP-MS.

Magnetic ZnFe2O4 nanotubes (ZFONTs) with numerous pores on their walls were synthesized and characterized. They are shown to be a viable sorbent for dispersive micro-solid phase extraction of the trivalent ions of rare earth elements (REEs), specifically of lanthanum, praseodymium, europium, gadolinium, holmium and ytterbium. The specific surface area of ZFONTs is large (57m2⋅g-1) and much bigger than that of ZnFeO4 nanoparticles (16m2⋅g-1). It is shown that REEs are quantitatively retained on ZFONTs in the pH range of 7.0-9.0. The separation of the sorbent from the aqueous phase was achieved by an external magnetic field. Following elution with 0.5mol⋅L-1 HNO3, REEs were quantified by inductively coupled plasma mass spectrometry. The main parameters influencing preconcentration and determination of the REEs were studied. Under optimum conditions, detection limits for REEs range from 0.01(Ho) to 0.75(La) pg⋅mL-1. Relative standard deviations are less than 6.5% (for n = 9; at 1.0ng⋅mL-1). The method was applied to the determination of trace REEs in spiked biological and environmental samples and gave satisfactory results. Graphical abstract Schematic presentation of a new adsorbent for dispersive micro-solid phase extraction (DMSPE) combined with ICP-MS. Magnetic ZnFe2O4 nanotubes with many pores on their walls were used for preconcentration and determination of rare earth elements (REEs) in environmental and biological samples.

Determination of trace rare earth elements in fruits by microwave digestion coupled with inductively coupled plasma optical emission spectrometry

In this work, a novel method was developed for the determination of trace rare earth elements (REEs) in fruit samples by microwave digestion coupled with inductively coupled plasma optical emission spectrometry (ICP-OES) after preconcentration with N, N, N′, N′-tetraoctyl diglycolamide (TODGA). The parameters affecting the extraction and back-extraction behaviors of the target analytes in liquid-liquid extraction (LLE) were studied systematically. Under the optimum conditions, the limits of detection (3σ, n = 7) for the target REEs of interest were in the range of 0.0548 (Tb)–0.541 (La) μg L−1, and the tolerable concentration ratios were reaches 4 orders of magnitude for the common interfering ions. The relative standard deviations (c = 100 μg L−1, n = 7) were from 0.6% (Sm) to 3.3% (La) with the wide linear range spanned three orders of magnitude (R2 > 0.999). The recoveries for the spiked fruit samples were ranged from 92.1% to 104%. The proposed method has the advantages of simple operation, good anti-interference ability, simultaneous determine 16 REEs, which has been successfully applied for analysis of REEs in the 10 locally collected fruit samples, thereby exhibits application potential for the analysis of trace REEs in biological samples with complex matrix.

A two-jet arc plasma: matrix effects and ways to their suppression

A two-jet plasma is used for direct atomic emission analysis of powdered samples. It is characterized by relatively weak matrix effects, which allows using unified calibration samples on the basis of graphite powder for analysis of the samples with inorganic, organic, and organomineral matrix. In the present paper the effects limiting the usage of the unified approach due to different thermal stability and evaporation efficiency of the samples are discussed. The understated concentrations of a set of elements (Al, Ba, Ca, La, Mg, Mn, Sr, Ti, and Y) were obtained in analysis of certified reference materials of geological samples. It was shown that determination of rare earth elements should be carried out in the region behind the jet confluence providing their complete evaporation. For other elements, registration of the spectra in this region improves the results to some extent but they do not achieve the certified values. To speed up evaporation of these elements, the experimental conditions were chosen for plasma chemical reactions which provide conversion of the matrix elements into more volatile compounds. Addition of ammonium hydrofluoride to powdered sample considerably increased the line intensities of Al and Ca strongly associated with the silicon matrix. Incomplete evaporation was observed in analysis of biological samples with particle size more than 100 μm. A decrease in consumption of carrier argon is quite enough for effective decomposition of the organic matrix in plasma; the value of gas consumption depends on thermal stability and particle size of the sample. Preliminary sample carbonization is another way to improve evaporation of biological samples.

Comment on: Mass Fractions of Forty‐Six Major and Trace Elements, Including Rare Earth Elements, in Sediment and Soil Reference Materials Used in Environmental Studies. Fiket et al. (2017), Geostandards and Geoanalytical Research, 41, 123–135

This paper is intended to be a constructive discussion of Fiket et al. (2017, Geostandards and Geoanalytical Research, 41, 123–135), who dealt with the determination of major, trace and rare earth elements in several sediment and soil certified reference materials. In the present author's view, the paper by Fiket et al. (2017) suffers from a lack of reference to several publications in which somewhat similar results had already been reported. The present contribution therefore provides a comparison of previously published results with those of Fiket et al. for the CRMs soil NCS DC 77302 (GBW 07410), stream sediment NCS DC 73309 (GBW 07311), marine sediments MESS‐3 and NCS DC 75301 (GBW 07314) and estuarine sediment IAEA‐405. It is argued that this fuller consideration (a) allows critical evaluation of the quality of the results presented by Fiket et al. and (b) highlights the advantages of their work. Finally, attention is drawn to the (possible or real) problems that can arise during simultaneous determination of multiple trace elements.

Dissolution techniques for determination of rare earth elements in phosphate products: Acid digestion or alkaline fusion?

Several studies have been carried out to compare and/or improve instrumental analytical techniques capable of quantifying trace elements, rare earths included. Sample dissolution is a key step in this process and the choice of the most appropriate technique depends on many factors, e.g., digestion power, laboratory workability, available instrumentation, and timing. Alkaline fusion and acid digestion are often the preferred techniques for decomposition of geological samples due to their precision and accuracy. The aim of this study was to evaluate dissolution techniques for determination of REE in phosphate products by ICP-MS. For this, twenty samples of phosphate products were selected from the fertilizer quality control program of the Brazilian Ministry of Agriculture, Livestock, and Food Supply. Samples of these products were digested by either microwave digestion or alkaline fusion. Both methods yielded accurate results, with alkaline fusion being slightly more efficient than microwave digestion in the extraction of light REE. However, this difference between methods was not observed for heavy REE and it did not affect the REE signatures. The information provided in this paper can assist in the choice of dissolution techniques for REE quantification, especially in phosphate fertilizers. In addition, the equations provided in this paper may also be used to interconvert the results from both methods.