Determination of rare earth impurities in high purity uranium by isotope dilution analysis

Summary An isotope dilution method for the determination of rare earth impurities in uranium has been developed and Ce, Nd, Sm, Eu and Gd have been determined in uranium oxide samples. The method involves isotopic dilution with enriched isotopes of the rare earths being measured, followed by the separation of rare earths from uranium. A mass spectrometer with thermionic source was used to determine the relative isotopic abundances in each of these rare earths. All these five elements were analysed selectively by preferential evaporation technique. Trace concentrations down to parts per billion range can be measured with good sensitivity and accuracy.

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Bestimmung von Verunreinigungen an Seltenen Erden in hochreinem Uran durch Isotopenverdünnungsanalyse

Zusammenfassung Eine Isotopenverdünnungsmethode wurde ausgearbeitet zur Bestimmung von Ce, Nd, Sm, Eu und Gd in Uranoxidproben. Das Verfahren umfaßt isotopische Verdünnung mit angereicherten Isotopen der zu bestimmenden Elemente und nachfolgende Abtrennung der Seltenen Erden von Uran. Die relativen Isotopenhäufigkeiten wurden mit Hilfe eines Massenspektrometers mit thermischer Ionenquelle bestimmt. Alle fünf Elemente wurden durch selektive Verdampfung analysiert. Spurenkonzentrationen bis herab zum ppb-Bereich konnten mit guter Empfindlichkeit und Genauigkeit erfaßt werden.

     

高纯氧化钇的感耦等离子体发射光谱分析及基体效应的研究

以高纯氧化钇中稀土杂质的ICP-AES测定为例, 研究了基体对分析元素谱线强度的影响及基体效应与工作条件的关系, 指出基体效应除主要来自分析物进样效率的降低外, 大量基体进入ICP降低了激发温度并对分析物的电离产生抑制作用, 提出用Se内标法代替通常的基体匹配法来补偿基体效应。进行了折衷条件选择及联样量确定等研究。实样分析表明, 内标法和基体匹配法所得结果一致, 加入回收率为87-120%, 精度也符合分析要求。     

Neutron activation analysis of rare earth impurities in metallic uranium

A method with a sensitivity of 2·10⁻⁷ to 1·10⁻¹⁰% has been developed for determining Yb, Ho, Dy, Gd, Eu, Sm and La impurities in metallic uranium by means of neutron activation. The method is based on a preliminary chromatographic separation of the total amount of rare earth elements from uranium by passing the solution in sulphuric acid through KU-2 cation exchange resin and eluting the traces of uranium retained by the resin with a solution of ascorbic acid. The rare earth impurities are then eluted from the resin with 4–5N HCl, evaporated, and irradiated for 20 hours with a neutron flux of 1.2·10¹³ n·cm⁻²·sec⁻¹. Subsequently the traces of the rare earth elements are co-precipitated with Fe(OH)₃, dissolved in concentrated HCl and separated from the iron and other impurities by passing the solution through Dowex 1X8 anion exchange resin in the chloride form. The individual rare earth elements are then separated from each other using KU-2 cation exchange resin and a solution of ammonium α-hydroxyisobutyrate as the eluant.     

An XRF method for the determination of common rare earth impurities in high purity yttrium oxide

Summary An XRF method for the determination of Eu, Gd, Tb, Dy, Ho, Er and Yb in yttrium oxide has been developed. The samples are converted to yttrium oxalate and presented to the spectrometer in the form of pressed pellets. Philips PW-1220, semiautomatic X-ray spectrometer is used for analysis. Analysis lines have been chosen after careful study of line interferences. The lower estimation limit for Yb is 0.01% and for other elements it is 0.005%. The method has been tested for its accuracy by analysing synthetic samples with known composition.

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Bestimmung von häufig vorkommenden Verunreinigungen an Seltenen Erden in Yttriumoxid hoher Reinheit mit Hilfe der Röntgenfluorescenzanalyse

Zusammenfassung Ein Verfahren zur röntgenfluorescenzanalytischen Bestimmung von Eu, Gd, Tb, Dy, Ho, Er und Yb in Yttriumoxid wurde ausgearbeitet. Die Probe wird zu Yttriumoxalat umgesetzt und in Form von Preßtabletten der RFA unterworfen. Das halbautomatische Röntgenfluorescenz-Spektrometer Philips PW-1220 wurde verwendet. Eine sorgfältige Untersuchung der Interferenzen führte zur Wahl der Analysenlinien. Die untere Bestimmungsgrenze liegt für Yb bei 0,01%, für die anderen Elemente bei 0,005%. Die Zuverlässigkeit des Verfahrens wurde anhand von synthetischen Proben bekannter Zusammensetzung geprüft.

     

辉光放电质谱法测定稀土矿中的15种稀土元素

利用高纯铜粉与稀土矿石粉末均匀混合压片制样.混合15种高纯稀土氧化物制样建立标准工作曲线,校正15种稀土元素相对灵敏度因子,再进行定量分析.结果 表明,稀土元素工作曲线的线性方程相关系数R2均大于0.996,相对标准偏差(RSD)小于5％,满足定量分析要求.测定结果与电感耦合等离子体质谱法(ICP-MS)和电感耦合等离...     

Determination of rare earth impurities in high purity gadolinium oxide by inductively coupled plasma mass spectrometry after 2-ethylhexylhydrogen-ethylhexy phosphonate extraction chromatographic separation

A method was developed for the determination of rare earth impurities in high purity Gd(2)O(3) by inductively coupled plasma mass spectrometry (ICP-MS). The matrix suppression effect of Gd(2)O(3) on signals of rare earth impurities was compensated for by Re internal standardization. The spectra overlap interferences from GdH, GdO, GdOH(n) (n=1-3) on Tb, Tm, Yb and Lu were eliminated by 2-thylhexylhydrogen-2-ethylhexy phosphonate (EHEHP) extraction chromatographic separation. The detection limits for REEs were 0.005-0.017 ng ml(-1) in solution and 0.002-0.05 mug g(-1) in solid. Recoveries of spiked sample for REEs were from 88 to 121% with the precision of 1.0-7.5% RSD. Determination of trace REEs in two Gd(2)O(3) samples were performed. The method can be applied to analysis of 99.99-99.9999% high purity Gd(2)O(3).     

Trace analysis of rare earth elements and other impurities in high purity scandium by inductively coupled plasma mass spectrometry after liquid-liquid extraction of the matrix

Bis(2-ethyl hexyl)-orthophosphoric acid in toluene has been used to extract scandium selectively from an aqueous phase containing nearly thirty elements at various concentrations. The trace elements (Li, Mg, Al, Mn, Co, Ni, Cu, Zn, Ga, Sr, Y, Cd, In, Sb, Ba, REE, Hf, Pt, Tl, Pb, Bi and u) have been determined quantitatively in the aqueous phase using inductively coupled plasma mass spectrometry (ICP-MS). The recoveries have been quantitative for most of the analytes studied and ICP-MS has been found suitable for the determination of trace quantities of these elements in the aqueous extract. The procedure has been applied to the quantitative ultra-trace analysis of rare earth elements (REE) and other trace impurities in high purity scandium metal (4N) using ICP-MS and ID-ICP-MS techniques.Presented in part at the 2nd Regensburger Symposium Massenspektrometrische Verfahren der Elementspurenanalyse, 6.-8.10.93, Regensburg, Germany     

Determination of rare earth elements at trace levels in uranium process stream samples by ion-interaction chromatography

To accurately determine ²⁴¹Am by mass spectrometry, interfering elements (IEs) including Bi, Hf, Hg, Pb, Pt, Pu and Tl need to be decontaminated. In this study, the extraction behaviors of IEs in HNO₃ and HCl mediums were systematically studied for the employed extraction resins (TRU, DGA-N and DGA-B). Based on the results, chemical separation procedures were proposed. After cooperation with proper co-precipitation methods, the proposed procedures can be used to determine ²⁴¹Am in environmental samples. The results of evaluation showed that IEs in soil samples were completely removed and ²⁴¹Am was accurately determined for all proposed procedures.     

Sorption of rare earth elements of waste solution of leaching uranium

The possibility of sorption recovery of rare earth elements from the waste sulfate solutions of uranium leaching, which contain a few tens of milligrams per liter of the rare earth elements, up to 1 g L^?1 of aluminum, and 2 g L^?1 of iron, with using a carboxyl sorbent CYBBER LX 280, hydrated titanyl hydrogen phosphate and its analogue modified with zirconium(IV). It was shown that 95% of the rare earth elements and more can be recovered by neutralizing the solution by sodium hydroxide to pH ≈ 4.2, separating the resulting precipitate based on iron hydroxide, and subsequent sorption at the CYBBER LX 280 sorbent.     

Determination of rare earth impurities in high purity europium oxide by inductively coupled plasma-mass spectrometry and evaluation of concentration values for europium oxide standard material

Direct determinations of 13 rare earth elements (La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Yb, Lu and Y) in high purity europium oxide by inductively coupled plasma mass spectrometry (ICP-MS) have been reported. The operating parameters of the instrument were optimized and the spectral interferences and the matrix effects were investigated. Using Ga or Rh as the internal standard can eliminate most of the matrix effects. The detection limits (3 sigma, n=10, integral time=1s) are 0.013-0.085 ng mL(-1) and the reproducibility (n=11) is 0.9-3%. The recoveries of spiking samples are 80-108%. Europium oxide standard material was made and its concentration values were evaluated by various techniques from 10 collaborating laboratories. By comparison of the results of ICP-MS with the results of other techniques, we have validated that ICP-MS is an accurate and reliable technique for analysis of ultratrace impurities in high purity rare earth matrix.     

Rare earth impurities in high purity lanthanum oxide determined by neutron activation analysis

Individual rare earth impurities in high purity La₂O₃ (99.9%) have been determined by NAA after pre-separation of the matrix (La). The separation is carried out on an anion exchanger (Dowex 1×8) using different mixtures of methanol/nitric acid as eluants. The rare earth elements from Dy to Lu are eluted quantitatively using a 10% 1M HNO₃-90% methanol mixture, while the light rare earths from Ce to Gd are eluted quantitatively using a 10% 0.05M HNO₃-90% methanol mixture. La, which is retained on the column, is eluted using 0.1M HNO₃. The recoveries of the various rare earth elements have been checked using radiotracers and also by spiking the sample with known amount of elements, and the recoveries are found to be quantitative. Results obtained on a typical high purity lanthanum oxide are reported here.     

Direct determination of rare earth impurities in high purity erbium oxide dissolved in nitric acid by inductively coupled plasma mass spectrometry

A novel method was developed for the direct determination of trace quantities of rare earth elements (REEs) in high purity erbium oxide dissolved in nitric acid by inductively coupled plasma mass spectrometry (ICP-MS) in this work. The mass spectra overlap interferences arose from Er matrix on the neighbouring and monoisotopic analytes of ¹⁶⁵Ho(100) and ¹⁶⁹Tm(100) were eliminated by adjusting instrumental peak resolution value from 0.7 to 0.3 amu. The matrix suppression effect of Er on the ion peak signals of REEs impurities was effectively compensated with spiking In as internal standard element. The limit of quantitation (LOQ) of REEs impurities was from 0.0090 to 0.025 μg g⁻¹, the recoveries of spiked sample for REEs were found to be in the range of 90.3-107% through using the proposed method and relative standard deviation (R.S.D.) varied between 2.5% and 6.7%. The novel methodology had been found to be suitable for the direct determination of trace REEs impurities in 99.999-99.9999% high purity Er₂O₃ and the results obtained from this method keep in good agreement with that acquired from high resolution ICP-MS.     

Determination of traces of rare earth elements in high-purity uranium by ion-exchange separation and neutron activation γ-spectrometry

Neutron activation γ-spectrometry is sufficiently sensitive for the determination of traces of rare earth elements but quantitative separation from uranium is essential. The rare earth elements in 0.2 M ammonium carbonate medium are quantitatively retained on Chelex-100, and are quantitatively separated from uranium by recycling the eluate. When 10-g samples are used, neutron activation provides detection limits of 1–20 μg kg^?1. Recoveries of rare earths, checked by spiking with radiotracers, are essentially complete.     

An ICP-AES method for the determination of heavy rare earth elements (Eu-Lu) in high purity yttrium oxide

Traces of heavy rare earth elements (Eu-Lu) were determined in high purity yttrium oxide by inductively coupled plasma atomic emission spectrometry. The yttrium oxide samples were dissolved in nitric acid and the solutions analyzed with a plasma produced by a 56 MHz RF generator at an output power of 1.5 kW. Using a high resolution sequential monochromator, interference-free spectral lines for Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu could be found for calibration. The detection limits for the above elements have been found to be slightly higher in the presence of yttrium matrix, than in aqueous solution. This could be attributed to background enhancements due to the presence of yttrium. The mean RSD of the method varied between 2.3% and 6.3% in the concentration range 0.01 and 0.5 g/ml. The percentage recovery ranged from 84 to 106 for the different rare earth elements.     

Determination of rare earth impurities in ytterbium oxide by X-ray fluorescence spectrometry

Summary Determination of Kare Earth Impurities in Ytterbium Oxide by X-ray Fluorescence Spectrometry An X-ray fluorescence spectrometric method for the determination of traces of Ho, Er, Tm, Lu and Y oxides in the concentration range of 0.005–1% in ytterbium oxide is developed. The precision at various concentrations of the standards is given. Intensity corrections for line overlaps have been determined.     

Determination of traces of rare earth elements in geological samples

A procedure for the determination of traces of rare earth elements by inductively coupled plasma-optical emission spectrometry (ICP-OES) and X-ray fluorescence spectrometry (XRF) is presented. The samples are decomposed either by fusion with lithium tetraborate or by acid attack in a microwave oven. Separation of the rare earth elements from accompanying elements is achieved by anion exchange. For the determination by ICP-OES the samples are injected in hydrochloric acid solution, for the determination by XRF the rare earth element traces are co-precipitated with rhodizonate and tannin and measured as a thin film on a membrane filter. All preconcentration steps have been optimized and tested using radiotracers. Furthermore the rare earth element contents of some international standard reference rocks have been determined; the results are compared to the certified values and other values given in the literature. The procedure is applied to a series of petrographically identical metabasites with different degrees of metamorphism to show the mobility of those ions under metamorphic conditions.     

Determination of rare earth elements in international geochemical reference materials

Instrumental neutron activation analysis of eight geochemical standard materials has been carried-out and the concentration values of nine rare-earth elements (REE) (La, Ce, Nd, Sm, Eu, Gd, Tb, Yb and Lu) have been determined. Discussion of some problems in the determination of those elements is presented and the results obtained are compared with literature values. In general, good agreement with available data was obtained but discrepancies with concentration values for a number of elements in some of these standards are discussed.     

O-TOF-ICP-MS analysis of rare earth elements,noble elements,uranium and thorium in river-relating species

The determination of rare earth elements (REEs), Au, Pt, Ir, Pd, Th and U in various river species was performed by the orthogonal time-of-flight inductively coupled plasma mass spectrometry (o-TOF-ICP-MS). The method working conditions were optimised in order to minimise the presence and possible spectral interferences of oxides. Ratios MO⁺/M⁺ as well as interference of light REE and Ba oxides/hydroxides with high REEs were evaluated and confirmed to be insignificant. Using the internal standard Re, non-spectral matrix effects (originally decreasing of intensities up to 15%) were overcome and recoveries were found from 92 to 105% for all matrices analysed. For solutions, limits of detection (3σ) were 0.14–0.82 for REEs, Th, U and Y, 1.18 for La, 4.3–5.6 for Au, Pt, Ir and Pd 11 for Sc (all in ng L^?1). The Principal component analysis was used for classification of samples according to their places of origin successfully. The o-TOF-ICP-MS was proved to be a very sensitive and suitable technique for bio-monitoring purposes and was employed in the analysis of biota samples (fish, insect, profiles, benthal growths) originated from five different places in the river Elbe (Czech Republic).     

Concentration of all rare earth impurities of cerium sub-group rare earth matrices

The separability of all rare earth impurities from cerium sub-group matrices was investigated. It was found that anion exchange chromatography carried out with aqueous methanol solutions of nitrates provides a useful method for the concentration of all rare earth impurities in neodymium and gadolinium matrices. The concentrate of the impurities can be processed further as required by the method chosen for their analytical determination.