Rare earth element analysis

Trace elements and rare-earth elements (REEs) of the same calcite samples used for the stable isotope analysis have significantly lower concentration of REE as well as most trace elements relative to typical carbonatites. The total REE contents of the Ulsan carbonates range from 3 to 17 ppm, which are much lower than any igneous rocks and even lower than those of some sedimentary rocks. REE and trace-element abundances may have changed sufficiently due to alteration, thus, affecting petrogenetic... 

These compounds are prepared by synthesis from the elements. The rare earth metal powder, as pure as possible, is placed in one of the arms of an L-shaped glass tube. The other arm contains the stoichiometric quantity of S, Se or Te (1 1 ratio). The tube is melt-sealed in vacuum and heated in an electric furnace until the non-metal is completely consumed. The temperature should reach 400-450 °C by the end of 2-3 days. Powder pattern analysis of the products indicates the formation of nonhomogeneous materials containing LngXa and LngX, but not LnX, which starts to form at1000-1100°C. 

Iieser et al. [628] studied the application of neutron activation analysis to the determination of trace elements in seawater. The rare earths included in this study were cerium and europium. The element concerned were adsorbed onto charcoal. Between 75% and 100% of the elements were adsorbed onto the charcoal which was then subjected to analysis by neutron activation analysis. Cerium (300 p,g/l) and europium (0.00082 pg/1) were found in North Sea water by this method. 

Elderfield and Greaves [629] have described a method for the mass spectromet-ric isotope dilution analysis of rare earth elements in seawater. In this method, the rare earth elements are concentrated from seawater by coprecipitation with ferric hydroxide and separated from other elements and into groups for analysis by anion exchange [630-635] using mixed solvents. Results for synthetic mixtures and standards show that the method is accurate and precise to 1% and blanks are low (e.g., 1() 12 moles La and 10 14 moles Eu). The method has been applied to the determination of nine rare earth elements in a variety of oceanographic samples. Results for North Atlantic Ocean water below the mixed layer are (in 10 12 mol/kg) 13.0 La, 16.8 Ce, 12.8 Nd, 2.67 Sm, 0.644 Eu, 3.41 Gd, 4.78 Dy, 407 Er, and 3.55 Yb, with enrichment of rare earth elements in deep ocean water by a factor of 2 for the light rare earth elements, and a factor of 1.3 for the heavy rare earth elements. 

Elution volume calibrations were performed using radioactive tracers of the rare earth elements and 133Ba, with atomic-absorption or flame-emission analysis of iron, sodium, potassium, calcium, and magnesium. As shown in Fig. 5.14, any barium added to the second columns is eluted at the start of the light rare earth element fraction . To ensure barium removal the sample can be put through the first column again. 

The chemistry of rare earth elements makes them particularly useful in studies of marine geochemistry [637]. But the determination of rare earths in seawater at ultratrace levels has always been a difficult task. Of the various methods applied, instrumental neutron activation analysis and isotope dilution mass spectrometry were the main techniques used for the determination of rare earths in seawater. However, sample preparation is tedious and large amounts of water are required in neutron activation analysis. In addition, the method can only offer relatively low sample throughputs and some rare earths cannot be determined. The main drawbacks of isotopic dilution mass spectrometry are that it is time-consuming and expensive, and monoisotopic elements cannot be determined as well. 

ABSTRACT A geochemical analysis of major, trace and rare earth elements was carried out in beach sands collected from the Northeastern coast of Mexico in order to observe the spatial trends along three different beaches. Results show that major elements patterns along the beaches are controlled by heavy minerals and plutonic and sedimentary input towards the coast. In addition, trace elements tendencies indicate that the beach sands are influenced by the presence of magnetite. Finally, the differences in Eu anomalies indicate a mix of felsic to mafic and intermediate rocks and feldspar weathering. 

The rare earth elements (REE) are the lanthanides (defined as those elements with valence electrons in 4/orbitals), La, Ce, Pr, Nd, (Pm), Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, and Yb. Often included for analysis, because they behave in a chemically similar way, although strictly not REE, are the Group 3 transition metals Y and Lu. The radioactive lanthanide element promethium (Pm) is excluded from analysis, since it is not found in samples because of its short half-life. 

Balaram, V. (1996). Recent trends in the instrumental analysis of rare earth elements in geological and industrial materials. Trends in Analytical Chemistry 15 475 486. 

Cousin, H. and Magyar, B. (1994). Precision and accuracy of laser ablation-ICP-MS analysis of rare earth elements with external calibration. Mikrochimica Acta 113 313-323. 

A significant proportion of the needs for reference materials for seawater trace metal studies would be addressed by the preparation of these materials. Although the total iron concentration of these reference materials should be provided, these materials clearly will be useful for studies of other important metals such as zinc, manganese, copper, molybdenum, cobalt, vanadium, lead, aluminum, cadmium, and the rare earth elements. With careful planning, such water samples should be useful for analysis of dissolved organic substances as well. The collection sites should be chosen carefully to provide both a high and a low concentration reference material for as many metals as possible. 

The basis for the claim of discovery of an element has varied over the centuries. The method of discovery of the chemical elements in the late eightenth and the early nineteenth centuries used the properties of the new sustances, their separability, the colors of their compounds, the shapes of their crystals and their reactivity to determine the existence of new elements. In those early days, atomic weight values were not available, and there was no spectral analysis that would later be supplied by arc, spark, absorption, phosphorescent or x-ray spectra. Also in those days, there were many claims, e.g., the discovery of certain rare earth elements of the lanthanide series, which involved the discovery of a mineral ore, from which an element was later extracted. The honor of discovery has often been accorded not to the person who first isolated the element but to the person who discovered the original mineral itself, even when the ore was impure and that ore actually contained many elements. The reason for this is that in the case of these rare earth elements, the earth now refers to oxides of a metal not to the metal itself This fact was not realized at the time of their discovery, until the English chemist Humphry Davy showed that earths were compounds of oxygen and metals in 1808. 

At first praseodymium was called didymium, which is Greek for twin, because it was always found with another rare-earth element. Using spectroscopic analysis, the two different color bands, one green and one yellow, indicated that there were two elements in didymium, but no one could identify the new elements. 

In the 1800s chemists searched for new elements by fractionating the oxides of rare-earths. Carl Gustaf Mosander s experiments indicated that pure ceria ores were actually contaminated with oxides of lanthanum, a new element. Mosander also fractionated the oxides of yttria into two new elements, erbium and terbium. In 1878 J. Louis Soret (1827—1890) and Marc Delafontaine (1837-1911), through spectroscopic analysis, found evidence of the element holmium, but it was contaminated by the rare-earth dysprosia. Since they could not isolate it and were unable to separate holmium as a pure rare-earth, they did not receive credit for its discovery. 

First, we analyzed samples for a large number of elements to Identify any elements, regardless of toxicity or typical concentration, that would provide signals for the presence of material from certain types of sources. Both ambient samples and particles from sources were analyzed by Instrumental neutron activation analysis (INAA), by which one can often measure about 35 elements In Individual samples (17), As the Important elements Pb, N1 and Cd are not consistently, If ever, observed by INAA, they were often measured by other methods. As INAA Is sensitive to very small amounts of obscure elements, we have obtained reliable data for elements such as Ga, Hf, Sc, In, W and many rare earths which pose no known health hazard at present levels and contribute Insignificant amounts of mass to TSP. However, as discussed below, many trace elements have already been shown to be Important In receptor... 

However, when Moseley and Urbain examined the rare-earth residues supposed to contain the new element, they found only about ten lines, all of which could he attributed to lutetium and ytterbium. In 1922, after a long period of interruption because of military duties, Professor Urbain resumed his search for element 72 in the same rare-earth.residues which he and Moseley had examined before the war. At his suggestion M. A. Dauvillier used de Broglie s improved method of X-ray analysis and observed two faint lines which almost coincided with those predicted for element 72 (15, 16). 

Georg von Hevesy. Hungarian chemist who, with Dr. Dirk Coster of the University of Groningen, discovered the element hafnium in zirconium ores and made a thorough study of its properties. Author of many papers on chemical analysis by X-rays, radioactivity, the rare earths, and electrolytic conduction. In 1943 he was awarded the Nobel Prize in Chemistry and in 1959 he received the Atoms for Peace Award. 

For many elements, the atomization efficiency (the ratio of the number of atoms to the total number of analyte species, atoms, ions and molecules in the flame) is 1, but for others it is less than 1, even for the nitrous oxide-acetylene flame (for example, it is very low for the lanthanides). Even when atoms have been formed they may be lost by compound formation and ionization. The latter is a particular problem for elements on the left of the Periodic Table (e.g. Na Na + e the ion has a noble gas configuration, is difficult to excite and so is lost analytically). Ionization increases exponentially with increase in temperature, such that it must be considered a problem for the alkali, alkaline earth, and rare earth elements and also some others (e g. Al, Ga, In, Sc, Ti, Tl) in the nitrous oxide-acetylene flame. Thus, we observe some self-suppression of ionization at higher concentrations. For trace analysis, an ionization suppressor or buffer consisting of a large excess of an easily ionizable element (e g. caesium or potassium) is added. The excess caesium ionizes in the flame, suppressing ionization (e g. of sodium) by a simple, mass action effect ... 

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