Measurement Of Rare Earth Elements Research Articles

Accurate Measurement of Rare Earth Elements by ICP‐MS after Ion‐Exchange Separation: Application to Ultra‐Depleted Samples

This study reports precise and accurate data for rare earth elements (REE) measured on eight geological reference materials, five enriched in REE (BE‐N, BHVO‐2, BR, BR‐24 and RGM‐1) and three very depleted in REE (BIR‐1, UB‐N and DTS‐2). Data were acquired by quadrupole ICP‐MS after isolation of the REE using an ion‐exchange chromatography procedure. All the measured REE abundances were similar within ≈ 5% (10% for the most REE‐depleted sample DTS‐2) to the high‐quality measurements previously published in the literature. We also show that by using an internal Tm spike, the reproducibility of the data was improved to ∼ 1%. Applying this technique to the analysis of ultra‐depleted rock samples (sub ng g−1), we show that significant improvements were obtained relative to the routine trace element measurement method. The chondrite‐normalised patterns were smooth instead of displaying irregularities. Although the classical method gives excellent results on REE‐rich samples, we believe that our technique improves the precision and accuracy of measurements for highly REE‐depleted rocks.

Determination of REEs in natural water by ICP-MS with the aid of an automatic column changing system

An automatic column changing system was developed for preconcentration and measurement of rare earth elements (REEs) in natural water samples, where syringe driven chelating columns (SDCCs) were applied to the hybrid (off-line operation and on-line operation) solid phase extraction of REEs. The sample loading was carried out off-line prior to the measurement. After that, the SDCCs were set into the column holder of the automatic column changing system and REEs were on-line eluted and measured by an inductively coupled plasma mass spectrometer (ICP-MS). The present automatic column changing system permitted continuously automatic measurement of 30 samples, while 3 min was enough for measuring one sample. The reproducibilities of REEs' signals obtained with two kinds of SDCCs showed that both of them are fit for the hybrid solid phase extraction method for preconcentration of REEs. The analytical detection limits (ADL) of REEs were in the range from 0.013 pg mL−1 for Tm to 0.15 pg mL−1 for Ce when 10 mL of water sample was loaded to each SDCC. The usefulness of the present method was confirmed by analysing NMIJ CRM 7201-a. After that, REEs in Lake Baikal water samples from depth of 50, 100, 150, 200, 250 m were determined. The results showed that dissolved REEs in the sample of 50 m depth were significantly lower than other samples, while the total REEs in the sample of each depth were close to one another. The distribution of REEs in Lake Baikal water samples was also discussed using shale normalized REEs distribution pattern.

Quantifying trace element disequilibria in mantle xenoliths and abyssal peridotites

We apply a tool based on element distribution between orthopyroxene and clinopyroxene for quantifying rare earth element (REE) disequilibria in ultramafic rocks in the subsolidus state. We present case studies of the REE contents of mineral cores in mantle xenoliths and abyssal peridotites using in situ analytical tools. Even when only mineral cores are measured (to avoid enriched rims), equilibrium is not always achieved on the mineral scale. Mineral cores in mantle xenoliths are closer to equilibrium than those in abyssal peridotites even though mantle xenoliths are known to be light REE-contaminated from the host lava. In the case of the abyssal peridotites, 13 out of 14 are out of equilibrium with the least metasomatized most in disequilibrium and the most metasomatized closest to equilibrium. We discuss hypotheses for these observations, but regardless of what caused the disequilibria, this tool allows one to “see through” the effects of secondary processes, such as infiltration by fluid inclusions via cracks and diffusive exchange between minerals and melts/fluids along grain boundaries. The ease of making in situ REE measurements makes this tool formidable in identifying different generations of clinopyroxenes in ultramafic lithologies. Such data will complement the interpretation of isotopic and petrographic studies of continental and oceanic lithospheric mantle.

Importance of measurement of rare-earth elements from the Soil Information and Monitoring System: A normalization method for detection of chromium contamination in soils

Importance of measurement of rare-earth elements from the Soil Information and Monitoring System: A normalization method for detection of chromium contamination in soils

Uptake and fractionation of rare earth elements on hydrothermal plume particles at 9°45′N, East Pacific Rise

Particulate samples (>0.45 μm) from a neutrally buoyant hydrothermal plume at 9°45′N on the northern East Pacific Rise were collected using large volume in situ filtration and analyzed for Fe, Al, Mn, Ni, and fourteen rare earth elements (REE). The Sm/Fe ratio (a proxy for overall REE/Fe) and Nd/Er (light/heavy REE fractionation) increased moderately with decreasing particulate Fe. Chemically, the sense of these relationships matched that documented previously in the TAG plume on the Mid-Atlantic Ridge (German et al., 1990), although particulate Fe was about 10 fold lower at 9°45′N. Spatial trends relative to the vent source, however, were opposite of expectation because slow Fe(II) oxidation and Fe(III) colloid aggregation over this interval led to increased particulate Fe (10–26 nM) with distance from source (Field and Sherrell, submitted). After subtraction of non-plume background particle composition, plume particles at 9°45′N and TAG had indistinguishable ranges of light REE-enriched fractionation relative to ambient seawater and had very similar Sm/Fe (therefore Kd for Fe oxyhydroxides), demonstrating that plume particles in both oceans reflect to a first degree the local seawater REE composition. Within-plume REE variations at 9°45′N were investigated using a simple mixing model which accounts for the bulk Fe-Al-Mn variations in the plume using two endmembers: fresh hydrothermal oxyhydroxide precipitates and ridge-crest background particles (composed largely of locally resuspended sediment). Sm/Fe and Nd/Er plot linearly with mixing ratio (R > 0.96), implying that the observed REE trends result from mixing of these two endmembers. Extrapolation to the composition of pure hydrothermal precipitates suggests that Nd/Er is fractionated relative to seawater by a factor of 1.8 during adsorption onto fresh Fe oxyhydroxide particles. The ridge-crest background particles are 5 fold higher in Sm/Fe and Nd/Er is 2.49 relative to seawater, partly a result of enriched terrigenous component in the resuspended matter. A reinterpretation of REE at TAG reveals that positive curvature in REE vs. Fe plots, argued previously to reflect continuous REE uptake (i.e., increasing Kd; German et al., 1990), may result from local depletion of the dissolved REE pool by partitioning onto Fe particles at Fe > 100 nM. Similar drawdown effects could contribute to the variable degrees of curvature observed for all seawater-source particle-reactive species in plumes that are sampled at high particulate Fe concentration. In sum, REE behavior in hydrothermal plumes is more consistent with equilibrium adsorption and mixing of distinct particle types, than with kinetic uptake control. Precise measurements of REEs in modern ridge-crest metalliferous sediments could be compared to the endmember composition calculated from the plume data to evaluate long-term changes in REE of the hydrothermal component.

The incorporation of rare earth elements in modern coral

We report measurements of rare earth elements (REEs) which show that these trace elements are being incorporated in modern coral in proportion to their seawater concentrations. Four Bermuda North Rock coral species, Diploria strigosa, Diploria labyrinthiformis, Montastrea annularis, and Porites astreoides and two Tarawa atoll samples of the species Hydnophora microconos were analyzed by TI-IDMS following cleaning techniques to isolate the lattice-bound REEs. Based on the replicate analyses of the same piece of Diploria strigosa, excellent reproducibility was achieved. The REE/Ca ratios (0.1–3 nmol/mol) of the Bermuda and Tarawa corals are similar to those of Cd/Ca, the trace metal with the lowest seawater concentration used in coral studies.With the exception of Ce, the distribution coefficients (e.g., DNd = [Nd coral/Nd seawater] × [Ca seawater/Ca coral]) between Bermuda coral lattice and Sargasso seawater have fairly flat patterns across the REE series. The values of D range from 1 to 3, like those reported for other trace elements in corals. This suggests, but does not prove, that REEs are incorporated in the aragonite lattice of these corals. The shale-normalized REE patterns of the Tarawa corals also have seawater-like distributions; however, no local seawater data are available to calculate values of D. Two Bermuda species (D. labyrinthiformis and P. astreoides) have values of D for Ce that are high with respect to the D values of La and Nd, implying that there is preferential uptake of Ce into the lattice. This may be related to the fact that Ce is the only REE with an active redox chemistry in seawater.There is considerable interest in using the chemical and isotopic composition of coral as indicators of climatic variations. The combination of REE/Ca ratios and neodymium isotopic composition of coral has the potential to help understand important natural processes. A primary application could be directed toward a tracer for river water discharge in tropical regions and, by inference, a proxy for rainfall, climate variation, and weathering history. This application would exploit the fractionated composition of REEs in river water as a terrigenous signature in coastal corals.

Radionuclide detection by ion-chromatography and on-line ICP/MS and beta detection: Fission product rare earth element measurements

Separation and analysis of235U fission produced rare earth elements (REE) is described. Rare earth elements were separated using a high presure ion chromatographic separation where by each rare earth is isolated and individually detected. Detection is performed by inductively coupled plasma mass spectrometry (ICP/MS) and solid scintillation beta counting. The resulting detection methods allow complete evaluation of all stable (non-radioactive) and many radioactive REE fission products. The two detection methods (ICP/MS and Beta) illustrate how mass selective and radiometric data can be used to provide complimentary information regarding the isotopic characterization of radioactive samples.

Electrothermal vaporization using a tungsten furnace for the determination of rare-earth elements by inductively coupled plasma mass spectrometry

In electrothermal vaporization inductively coupled plasma mass spectrometry (ETV-ICP-MS) using a tungsten furnace, the effect of vaporizing parameters on signals and the performance of the ETV technique in the measurement of rare-earth elements (REEs) have been investigated. The precision for La was 1-2% at absolute amounts above 1 pg. The detection limits for 14 REEs were 0.0001-0.0006 ng mL −1 , 1 order of magnitude better than those obtained by NEB-ICP-MS

Ion probe measurement of rare earth elements in biogenic phosphates

The rare earth element (REE) distributions in individual fish teeth and conodonts have been measured by ion probe. Concentrations and La Yb ratios show little variations, except in the enamel, which suggests that REE uptake from the sedimented biogenic debris takes place at the water-sediment interface as an essentially quantitative process without fractionation. Late diagenetic disturbances remained of marginal importance. Hence, REE in phosphatic debris might reflect the input from the overlying water column.

A method for the quantitative measurement of rare earth elements in the ion microprobe

An ion probe method for the quantitative measurement of rare earth elements (REE) in phosphates is presented. The measurements are made with a Cameca IMS 3F ion microprobe. All complex molecular interferences are removed effectively with moderate energy filtering and the remaining mass spectrum is deconvoluted into contributions from REE and their monoxides only. Corrections for fluorides, which are present in fluorapatites, can be made. Sensitivity factors relative to Ca are determined from a terrestrial apatite standard. Comparison with other standards of known REE concentrations shows that working curves are linear over a wide range of concentrations. The method allows the measurements of all REE in spots of 5–20 μm in diameter. Detection limits depend on the overall REE pattern but are generally ⩽ 50 p.p.b. for the light REE and ∼ 200 p.p.b. for the heavy REE. Preliminary measurements on oxides show that this technique can be extended successfully to other phases.

A large volume sediment squeezing system for the analysis of rare earth elements in deep ocean pore waters

The measurement of rare earth elements (REE) in pore waters raises a number of analytical problems. Relatively high sample volumes are required to obtain sufficient concentrations for measurement along with a strict control over temperature and oxygen contact. As part of a study of REE in marine systems, we have developed a sampling technique which has proved its capability to provide good quality samples of sufficient size for this work.

Rare earth contents in carbonatites

Mass spectrometric measurements of rare earth elements have been made by isotope dilution in several carbonatites. The results show a great enrichment of total rare earth content and a large fractionation between heavy and light rare earths. The patterns observed permit an easy distinction between limestones and carbonatites. This result suggests that in the carbonatite process the gas phase might play an important role.