Rare earth elements determination

Rare earth elements, determination by x-ray emission spectrography, 199, 328... 

Kramer KJM, Dorten WS, Groenewoud H van hex, de Haan E, Kramer GN, Monteiro L, Muntau H, Quevauviller Ph (1999) Collaborative study to improve the quality control of rare earth element determinations in environmental matrices. J Environ Monit 1 83-89. 

Bonhoure, J., Kister, P., Cuney, M., Deloule, E., 2007. Methodology for rare earth element determinations of uranium oxides by ion microprobe. Geostandards and Geoanalytical Research, 31, 209-225. Bonhoure, J. 2007. Geochimie des elements de terres rares et du plomb dans les oxydes d uranlum naturels. Ph.D Thesis, INPL, Nancy, France, 390 p. 

Zhu,W., De Leer, E.W. B., Keimedy, M., and Kelderman, P. (1997). Study of a partial least-squares regression model for rare earth element determination by inductively coupled plasma mass spectrometry.J./l [Pg.287]

The total cerium content in the single crystal samples on the basis of rare-earth elements is determined by photometry after Ce(III) oxidation by ammonium persulfate. The Ce(III) content is calculated from the difference. Comparison of the determination results of the total cerium content obtained by photometric and atomic emission methods for Li GdlBO ljiCe demonstrated the elaborated procedure precision and systematic error absence. 

SPECTROPHOTOMETRIC DETERMINATION OF RARE EARTH ELEMENTS IN MONO CRYSTALS AND STARTING LEAD MOLYBDATE RAW MATERIAL... 

The X-ray determination of REE in geological samples is normally complicated by the relatively low concentrations of the REE, their complex X-ray spectra, the high concentration of matrix elements and the lack of reference standards with certified values for REE. A rapid and sensitive ion exchange and X-ray fluorescence procedure for the determination of trace quantities of rare earths is described. The REE in two U.S.G.S. standards, two inhouse synthetic mixtures and three new Japanese standards have been determined and corrections for inter-rare earth element interferences are made. 

Inductively coupled plasma-mass spectrometry (ICP-MS) is a multielement analytical method with detection limits which are, for many trace elements, including the rare earth elements, better than those of most conventional techniques. With increasing availability of ICP-MS instalments in geological laboratories this method has been established as the most prominent technique for the determination of a large number of minor and trace elements in geological samples. 

An interesting variant of Group I is the determination of thorium in monazite concentrates.73 Here the variations that may occur in the chemical composition of the matrix leave its x-ray absorbance virtually unaltered. This simplicity is possible because the principal individual rare-earth elements present in the samples lie in the range of atomic numbers from 57 to 60, a range so small as to preclude marked variations in the over-all mass absorption coefficient. 

Tracer materials are defined as any product included in the test substance that can be recovered analytically for determining the drift from the application. This may be the active ingredient in an actual tank mix, or it may be a material added to the tank mix for subsequent detection. The selection of an appropriate tracer for assessing deposition rates in the field is critical to the success of a field study. Tracer materials such as low-level active ingredient products, colored dyes, fluorescent dyes, metallic salts, rare earth elements and radioactive isotopes have been used with varying degrees of success in the field. An appropriate tracer should have the following characteristics ... 

Itoh, A., Hamanaka, T., Rong, W., Ikeda, K., Sawatari, H., Chiba, K., and Haraguchi, H., Multielement determination of rare earth elements in geochemical samples by liquid chromatography/inductively coupled plasma mass spectrometry, Anal. Sci., 15, 17, 1999. 

Leddicotte, G. W. (1956). Some methods for determination of rare earth elements, page 63 in Rare Earths in Biochemical and Medical Research ... 

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. 

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. 

Tian-Hong Zhang et al. [652] have reported a new ion exchange chelating fibre with aminophosphonic and dithiocarbamate groups, based on polyacrylonitrile for the preconcentration of rare earth elements in seawater prior to their determination by inductively coupled plasma mass spectrometry. Rare... 

Dulski, P. (1994). Interferences of oxide, hydroxide and chloride analyte species in the determination of rare earth elements in geological samples by inductively coupled plasma-mass spectrometry. Fresenius Journal of Analytical Chemistry 350 194-203. 

Jarvis, K. E. (1988). Inductively coupled plasma mass spectrometry a new technique for the rapid or ultra-trace level determination of the rare-earth elements in geological materials. Chemical Geology 68 31-39. 

Jarvis, K. E. and Williams, J. G. (1993). Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) a rapid technique for the direct, quantitative determination of major, trace and rare-earth elements in geological samples. Chemical Geology 106 251—262. 

Lichte, F.E., Meier, A. L., and Crock, J. G. (1987). Determination of the rare-earth elements in geological materials by inductively coupled plasma mass spectrometry. Analytical Chemistry 59 1150-1157. 

Pillay, A. E. and Punyadeera, C. (2001). An enhanced procedure for the rapid digestion of high silicate archeological specimens followed by ICP-MS determination of traces of rare earth elements (REEs). Journal of Trace and Microprobe Techniques 19 225-241. 

Nance WB, Taylor SR (1976) Rare earth element patterns and crustal evolution—I. Australian post-Archean sedimentary rocks. Geochim Cosmochim Acta 40 1539-1551 Nishio Y, Nakai S (2002) Accurate and precise lithium isotopic determinations of igneous rock samples using multi-collector inductively coupled plasma mass spectrometry. Anal Chim Acta 456 271-281 Nishio Y, Nakai S, Hirose K, Ishii T, Sano Y (2002) Li isotopic systematics of volcanic rocks in marginal basins. Geochim Cosmochim Acta 66 A556... 

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. 

The discovery of the rare earth elements provide a long history of almost two hundred years of trial and error in the claims of element discovery starting before the time of Dalton s theory of the atom and determination of atomic weight values, Mendeleev s periodic table, the advent of optical spectroscopy, Bohr s theory of the electronic structure of atoms and Moseley s x-ray detection method for atomic number determination. The fact that the similarity in the chemical properties of the rare earth elements make them especially difficult to chemically isolate led to a situation where many mixtures of elements were being mistaken for elemental species. As a result, atomic weight values were not nearly as useful because the lack of separation meant that additional elements would still be present within an oxide and lead to inaccurate atomic weight values. Very pure rare earth samples did not become a reality until the mid twentieth century. 

Trace elements also exhibit systematic changes in concentration with depth. Figure 8.37 shows, for instance, concentration profiles of rare earth elements (REE) determined by De Baar et al. (1985) in Pacific and Atlantic waters. Note that the concentration profiles differ for the various elements in the series in particular, the amount of Ce is quite high in surface waters of the Atlantic Ocean. 

Linsalata P, Franca EP, Eisenbud M. 1985. Determination of the human intake of thorium and the light rare earth elements from high and typical natural radiation environments. Trace Subst Environ Health 19 257-263. 

Because Sm and Nd are both rare Earth elements and have similar chemical properties, and because they often occupy crystalline sites that are not easily altered, this system is resistant to alteration by later events (such as a later metamorphic event). Hence, this system is often applied to determine old and formation ages, whereas other systems (such as K-Ar) may be applied to obtain metamorphic ages. 

Two specific features determine the similarity and difference of energy levels in di- and trivalent ions of rare-earth elements. First, isoelectronic configurations of TR " and of the next elements in the periodic system determines a qualitatively similar pattern of terms and multiplet levels, namely for TR the order of the 4/ -configuration levels and of excited 4f 5d-configuration levels... 

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