Simultaneous determination of rare earth elements by using substoichiometric separation of lanthanium

An analytical method for the simultaneous determination of rare earth elements by using substoichiometry with two chelating agents, a complexon and an extracting agent, is proposed. The principle of the method is that the element which has the lowest stability constant with the complexon is separated substoichiometrically, while other elements which have higher stability constants are separated quantitatively by a single extraction. This method was applied to neutron activation analysis of rare earth elements. Lanthanum, europium and terbium in orchard leaves were determined simultaneously by using substoichiometric separation with DTPA and TTA.     

Precise determination of rare earth elements in rocks by neutron activation analysis

A pre-irradiation group separation method has been developed for the neutron activation analysis of rare earth elements (REE) and Ba in silicate rocks. REE and Ba were quantitatively separated from other elements by cation exchange column method. The chemical yield of each separation was monitored with Pr added to the sample powder before decomposition. The accuracy and precision were tested by repeated analyses of JB-1 and one analysis of BCR-1. In addition, it was found that REE distribution in a granitic rock powder was inhomogeneous and therefore special care must be taken for the sampling of granitic rock powders.     

An optimum method for the determination of rare earth elements by neutron activation analysis

A scheme is described for the analysis of all 14 rare earth elements in rocks by neutron activation analysis using a group of radiochemical separation. The scheme takes particular account of the ‘difficult’ rare earth elements and is designed to minimise both γ-spectrometer counting time and overall analysis time.     

Determination of rare earth elements in phosphorites by neutron activation analysis

Fourty three phosphorite rocks from Western Iraq were analyzed for eleven REE as well as uranium by NAA using IRT Reactor with a neutron flux of 2.3·10¹³ n·cm^–2·s^–1. The gamma activity from each sample was counted with a Ge(Li) and well-type HPGe, each detector connected to an on-line computer. Uranium fission products and different reaction interferences were assessed and allowed for. The results were also checked against international reference materials.     

Selective preconcentration of rare earth elements by substoichiometric precipitation of calcium oxalate and its application to the neutron activation analysis of biological material

A preconcentration method for trace amounts of rare earth elements (REs) based on the substoichiometric precipitation of calcium oxalate was developed. RE(III) was quantitatively coprecipitated with calcium oxalate which had been precipitated from the calcium of a macrocomponent in a biological sample by addition of a substoichiometric amount of oxalate. In this way high selectivity for RE(III) from other elements was achieved. The method was applied to the neutron activation analysis of a biological sample (NBS SRM 1572 Citrus Leaves), and Sc, La, Ce, Pf, Nd, Sm, Eu, Th, Dy, Ho, Yb and Lu were determined with a relative standard deviation of less than 5%.     

Determination of rare earth elements in bauxites by instrumental neutron activation analysis

The instrumental neutron activation analysis method was used for determination of 12 rare earth elements in red and white bauxites. Consideration was given to those systematic errors which in a relative method of analysis can result from the effects of neutron self-shielding, photon self-absorption and fission interfering reactions, due to different chemical composition of bauxite samples and the standard of silicate rock. Also presented is the characteristics “V” shaped chondrite normalized rare earth pattern of white bauxites.     

Radioactive substoichiometric isotope-dilution procedure for the determination of rare earth metals

A theory is developed which describes the equilibrium conditions when solutions containing trace metals and substoichiometric amounts of EDTA are extracted with thenoyltrifluoroacetone. Experimental evidence is given to support the theory. A method for the determination of microgram quantities of rare earth metal is outlined as an application.     

Determination of rare earth elements in mineral raw materials and rare earth industry products by neutron activation analysis

To determine REE in mineral raw materials, high purity RE metals and their compounds, neutron activation analysis with extraction chromatographic REE separation has been developed. Combination of the developed RE extraction and separation procedures with subsequent -spectrometric analysis of the RE radionuclides allows to determine their content with the lower detection limit –10^–5–10^–8%. The relative standard deviation is 0.2–0.3.     

Radiochemical neutron activation analysis determination of rare earth elements in geological materials with ppb sensitivity

Rare earth elements are determined, with ppb sensitivity, by radiochemical activation analysis using a fusion dissolution process and a quantitative group separation scheme, followed by radioassaying. Spectral interference is avoided, or corrected for, by repeating the counting operation with a delay of four to six weeks. This allows for the decay of shorter lived interfering isotopes such as¹⁵⁵Eu on¹⁶⁰Tb and¹⁷⁵Yb on¹⁴¹Ce. The scheme is rapid, sensitive and uses standard radiochemical laboratory facilities and counters. It has been applied to a wide range of rocks and minerals and data for eleven rare earths (La, Ce, Nd, Sm, Eu, Gd, Tb, Ho, Tm, Yb and Lu) is presented here and compared with literature values.     

Sequential determination of ultra-trace highly siderophile elements and rare earth elements by radiochemical neutron activation analysis: Application to pallasite meteorites

An analytical scheme of radiochemical neutron activation for the sequential determination of ultra-trace rare earth elements (REEs) and highly siderophile elements (HSEs) in geological and cosmochemical samples is presented. Using this procedure, several selected elements of REEs and HSEs were successively determined for geological reference samples and olivine crystals separated from pallasite meteorites. Based on the data for geological reference samples, it was concluded that the procedure presented in this study could yield data usable for cosmochemical discussion of the genesis of pallasite meteorites.     

Determination of rare earth elements by charged particle activation analysis in geological materials

The rare earth elements (REE), Pr, Sm, Eu, Gd, Ho, Er and Tm have been determined by charged particle activation analysis using 40 MeV a-particles through radiochemical approach. The radiochemical separation of REE as a group has been carried out from the bulk matrix. It has been shown from the theoretical computation that the products obtained from (a,xn) reactions (x = 1, 2, 3) are more suitable compared to those from (a,pyn) reactions (y = 0, 1, 2) due to the former having higher cross section (of the order of thousand millibarns).     

Determination of rare earth elements in Taiwan monazite by chemical neutron activation analysis

Taiwan monazite is a unique mineral obtained from the heavy sand found in the river floor of Tzuo-suei river and En-suei river. Both rivers are flowing parallel with separated narrow area into the sea at southwestern coast of Taiwan. The characteristic of monazite is that it contains considerable rare earth elements (REEs). REEs are considered very useful elements in the local industries and scientific researches such as ceramic, semiconductors, and glass optics. In this study, chemical neutron activation analysis (CNAA) was used to determine the contents of REEs in Taiwan monazite. A few milligram of monazite was digested in the microwave oven for 25 minutes with mixed acid (conc. HNO₃ and HClO₄). REEs were preconcentrated by hydrated magnesium oxide and CNAA was performed.     

Use and automation of multielement substoichiometric extraction of metal chelates in activation analysis

The present status of forensic activation analysis (FAA) is critically discussed. The areas in forensic science in which it has contributed a new capability and those in which it has not, are both pointed out. The limitations and advantages in using FAA under different circumstances are noted. The value of FAA of hair, metal fragments, glass, soil, paint, fibre, heavy metal poisons and gunshot residue in comparison with conventional forensic techniques, is discussed.     

Radiochemical neutron activation analysis of rare earth elements in peridotitic rocks

The understanding of the geochemistry of basalt petrogenesis and the nature of the upper mantle requires the examination of such rocks as peridotites which in many cases are thought to represent upper mantle material. The mineralogical composition of peridotitic rocks in such that they accommodate large proportions of such trace elements as the transition elements but very small amounts of the rare earths and hygromagmaphile elements. The last two groups are often able to provide a large amount of information leading to petrogenetic models. Owing to the extremely low concentrations of the REE in peridotitic rocks it is necessary to separate them from other elements which will interfere with their precise determination. We have used a radiochemical neutron activation analytical method which is adapted from various published methods. It involves a post-irradiation sample fusion, two separate ion-exchange chromatographic stages and finally a fluoride precipitation. The RNAA procedure is capable of providing very precise REE data for perioditic samples and we have used it for the analysis of such rocks from several geodynamic environments.     

Determination of individual rare earth elements in Vietnamese monazite by radiochemical neutron activation analysis

Radiochemical neutron activation analysis (RNAA) has been applied for determination of rare earth elements (REE) in Vietnamese monazite. The chemical separation procedure used is based on the chromatographic elution of rare earth groups, after the separation of²³³Pa(Th) in irradiated monazite samples by coprecipitation with MnO₂, the rare earth elements were retained by Biorad AG1×8 resin column in 10% 15.4M HNO₃-90% methanol solution. The elution of heavy rare earth (HREE) and middle rare earth (MREE) groups was carried out with 10% 1M HNO₃-90% methanol and 10% 0.05M HNO₃-90% methanol solution, respectively; while the light rare earths (LREE) were eluted from the column by 0.1M HNO₃ solution. The accuracy of the method was checked by the analysis of granodiorite GSP-I and the rare earth values were in good agreement.     

156Dy as an activable yield tracer for determination of rare earth elements in biological materials by neutron activation analysis

Use of an enriched¹⁵⁶Dy isotope as an activable yield tracer for the determination of lanthanoid contents in various biological reference materials has been proposed. The method consists of preconcentration of the lanthanoid in the¹⁵⁶Dy doped samples followed by neutron irradiation and further chemical purification steps. The chemical behaviour of lanthanoid elements in the whole procedure was found, in separate runs, similar to that of the added¹⁵⁶Dy within experimental errors. Simple purification steps after irradiation allow the measurement of relatively short-lived nuclides and diminish the radiation dose received during the chemical treatment. The present results for orchard leaves (NBS SRM 1571) are generally in good agreement with the previously reported data. Some new data are obtained for other biological reference materials.     

The determination of rare earth alloying additives in special steels by neutron activation analysis

A procedure for neutron-activation analysis of cerium, lanthanum, praseodymium and neodymium, tested on more than thirty samples of steels, is described. After irradiation for 20 hrs with a neutron flux of 1.2·10¹³ n·cm⁻²·sec⁻¹ the steel samples were dissolved in aqua regia and extraction separation of iron from 6N HCl by ether was employed. The REE were separated as a group by precipitation as fluorides and hydroxydes. The individual rare-earth elements were separated from each other using a KU-2 cation exchange resin and a solution of ammonium α-hydroxyisobutirate as eluant. The separated samples were counted on a NaI(T1) γ-spectrometer.     

Determination of rare earth elements in recent and fossil shells by radiochemical neutron activation analysis

Seven rare earth elements (La, Ce, Sm, Eu, Tb, Yb and Lu) in marine shell samples were determined by neutron activation analysis. In order to measure γ-ray using a Ge(Li) detector without serious interference from the intense Compton background from²⁴Na, a simple radiochemical separation was performed by a co-precipitation method with hydrated iron(III) oxide. The chemical yields for shell samples (91–99%) were determined by a re-activation technique for Gd and Yb. The interference from the²³⁵U(n, fission) reaction was corrected for determination of La and Ce. The data obtained in this study showed the behavior of rare earth elements in shells during the process of fossilization.