Lanthanide determination

THE WAYS FOR INCREASING OF THE SENSIBILITY OF LANTHANIDES DETERMINATION BY LUMINESCENT METHOD... 

Enhanced Luminescence of Lanthanides Determination of Europium by Enhanced Luminescence 184... 

The question of coordination in aqueous solutions is not as clear as in solid state. Sped-ding s work [53] on the partial molar volumes of aquo ions of lanthanides and the irregular trends of these quantities in the lanthanides has been taken as evidence for change in coordination number in the lanthanide series [54]. The change in coordination from 9 to 8 in the lanthanide series has been confirmed by X-ray and neutron diffraction studies of LnCb solutions [55], The coordination numbers of lanthanides determined in aqueous solutions by various techniques along with the coordination numbers obtained are given below ... 

The phase relationships in the systems R Oj-Fe Oj-Fe (R Y and the lanthanides) determined by means of the gravimetric method with controlled oxygen partial pressure... 

Physical Properties. An overview of the metallurgy (qv) and soUd-state physics of the rare earths is available (6). The rare earths form aUoys with most metals. They can be present interstitiaUy, in soUd solutions, or as intermetaUic compounds in a second phase. Alloying with other elements can make the rare earths either pyrophoric or corrosion resistant. It is extremely important, when determining physical constants, that the materials are very pure and weU characteri2ed. AU impurity levels in the sample should be known. Some properties of the lanthanides are Usted in Table 3. 

Neutron-rich lanthanide isotopes occur in the fission of uranium or plutonium and ate separated during the reprocessing of nuclear fuel wastes (see Nuclearreactors). Lanthanide isotopes can be produced by neutron bombardment, by radioactive decay of neighboring atoms, and by nuclear reactions in accelerators where the rate earths ate bombarded with charged particles. The rare-earth content of solid samples can be determined by neutron... 

The production of cerium derivatives begins with ore beneficiation and production of a mineral concentrate. Attack on that concentrate to create a suitable mixed lanthanide precursor for later separation processes follows. Then, depending on the relative market demand for different products, there is either direct production of a cerium-rich material, or separation of the mixed lanthanide precursor into individual pure lanthanide compounds including compounds of pure cerium, or both. The starting mineral determines how the suitable mixed lanthanide precursor is formed. In contrast the separation... 

For elimination of intramolecular energy losses, we have synthesized ligands with high hydrophobisity - perfluoro-P-diketones R -CO-CH -CO-R, (R = CgF j or CgF R = phenyl or a-thienyl), that without second ligand eliminate completely water molecules from the inner coordination sphere. These ligands we have used in analysis at determination of Sm, Eu, Nd, Yb microamounts in high-purity lanthanide and yttrium oxides. 

There s it is required to keep unchangeable chemical forms of material components, as well as lanthanide concentration ratio in different degree of oxidation. Therefore, the main conception of this work is to combine process of the sample decomposition and analytical reaction of the determined chemical form. 

Flumequine is a representative of fluoroquinolones which are high-effective antimicrobial medicines used as fodder supplements in cattle-breeding. This causes the necessity in effective testing techniques to detenuine the content of flumequine in meat products. Fluorimetric determination based on sensitized luminescence of fluoroquinolone chelates with lanthanides is a promising one. The literature lacks information of flumequine detemiination with the aid of sensitized fluorescence. 

The aim of this work was to study the influence of a second ligand, the concentration and nature of surfactants on flumequine-sensitized fluorescence of lanthanides and the usage of such a mixed-ligand complex for fluorimetric determination of flumequine in hen meat tissues. 

Determination of cerium as cerium(IV) iodate and subsequent ignition to cerium(IV) oxide Discussion. Cerium may be determined as cerium(IV) iodate, Ce(I03)4, which is ignited to and weighed as the oxide, Ce02. Thorium (also titanium and zirconium) must, however, be first removed (see Section 11.44) the method is then applicable in the presence of relatively large quantities of lanthanides. Titrimetric methods (see Section 10.104 to Section 10.109) are generally preferred. 

Determination of thorium as sebacate and subsequent ignition to the oxide, ThOa Discussion. This procedure permits of the separation by a single precipitation of thorium from relatively large amounts of the lanthanides (Ce, La, Pr, Nd, Sm, Gd) and also from cerium(IV). 

A mercury cathode finds widespread application for separations by constant current electrolysis. The most important use is the separation of the alkali and alkaline-earth metals, Al, Be, Mg, Ta, V, Zr, W, U, and the lanthanides from such elements as Fe, Cr, Ni, Co, Zn, Mo, Cd, Cu, Sn, Bi, Ag, Ge, Pd, Pt, Au, Rh, Ir, and Tl, which can, under suitable conditions, be deposited on a mercury cathode. The method is therefore of particular value for the determination of Al, etc., in steels and alloys it is also applied in the separation of iron from such elements as titanium, vanadium, and uranium. In an uncontrolled constant-current electrolysis in an acid medium the cathode potential is limited by the potential at which hydrogen ion is reduced the overpotential of hydrogen on mercury is high (about 0.8 volt), and consequently more metals are deposited from an acid solution at a mercury cathode than with a platinum cathode.10... 

Bancroft and Gesser [870] conclude that kinetic factors are predominant in determining whether decomposition of a metal bromate yields residual bromide or oxide. The thermal stabilities of the lanthanide bromates [877] and iodates [877,878] decrease with increase in cationic charge density, presumably as a consequence of increased anionic polarization. Other reports in the literature concern the reactions of bromates of Ag, Ni and Zn [870] and iodates of Cd, Co, Mn, Hg, Zn [871], Co and Ni [872], Ag [864], Cu [867], Fe [879], Pb [880] andTl [874]. 

The lanthanide formates decompose above 670 K [1040] and the chemical changes proceed through the oxyformate [1041] and the oxy-carbonate to Ln203. Values of E determined by non-isothermal methods [1040] decreased with increase in atomic number for reaction in air but were approximately equal for reactions in vacuum. 

The conformational preference of the monosulfoxides of 1,2-, 1,3- and 1,4-dithianes (179-181) were determined by NMR experiments which included variable-temperature studies, double irradiation, solvent effects and the influence of lanthanide shift reagents167. For 179 and 181, the axial conformers were the dominant species in CD3OD, but for 180, the equatorial conformer was in excess. 

The enantiomeric purity of optically active sulphoxides can be determined by chiral lanthanide shift reagents such as tris(3-trifluoroacetyl-ti-camphorato)europium(III) and tris(heptafluorobutyryl-d-camphorato)europium(III)218-219-221, the latter shown in Scheme 23. 

H-NMR spectroscopy can be used to determine alkenesulfonates in mixtures [115]. Under normal conditions, 1-alkenesulfonate shows a signal separated from the other positional isomers [122]. Moreover, the utilization of a lanthanide shift reagent makes possible even the separation of the signals of isomeric alkenesulfonic acids and hydroxyalkanesulfonic acids as their methyl esters [124]. 13C-NMR spectroscopy, which is not as quantitative, simply gives the cis/trans ratio of the main positional isomer. 

Alternatively, complexation with lanthanide shift reagents allow the signals of the MTPA ester to be resolved and used to determine enantiomeric... 

A closely related method does not require conversion of enantiomers to diastereomers but relies on the fact that (in principle, at least) enantiomers have different NMR spectra in a chiral solvent, or when mixed with a chiral molecule (in which case transient diastereomeric species may form). In such cases, the peaks may be separated enough to permit the proportions of enantiomers to be determined from their intensities. Another variation, which gives better results in many cases, is to use an achiral solvent but with the addition of a chiral lanthanide shift reagent such as tris[3-trifiuoroacetyl-Lanthanide shift reagents have the property of spreading NMR peaks of compounds with which they can form coordination compounds, for examples, alcohols, carbonyl compounds, amines, and so on. Chiral lanthanide shift reagents shift the peaks of the two enantiomers of many such compounds to different extents. 

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