Thin-layer chromatographic behaviour and separation of rare earths in silica gel-aqueous alkali metal chloride systems

Summary The thin-layer chromatographic behaviour of all the rare earths except Pm on silica gel in aqueous solutions of five alkali metal chlorides has been surveyed. The Rf-values and the logarithms of the separation factors relative to Gd vary in a regular and peculiar way with increasing atomic number, through a reflection of the strong tetrad effect. A discussion concerning the effects on the Rf-values of the solvent cations and the solvent anions, and typical chromatograms for the separations of multi-component mixtures containing adjacent lanthanoids are also presented.     

Thin-layer chromatographic behaviour and separation of rare earths in silica gel-aqueous alkali metal nitrate systems

Summary The thin-layer Chromatographic behaviour of all rare earths except P_m on silica gel in aqueous alkali metal nitrate solutions has been investigated. In all the solutions the tetrad effect is clearly observed in the variations of both the R_f-values and the logarithms of the separation factors relative to Gd with the atomic numbers of the lanthanoids. A brief discussion concerning the effect of the solvent cations and typical chromatograms for the separations of multicomponent mixtures containing adjacent lanthanoids are presented.

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Dünnschicht-chromatographisches Verhalten und Trennung von seltenen Erden in den Systemen Silicagel — alkalische Metallnitratlösung

     

Thin-layer chromatographic behavior of rare earths on silica gel with aqueous alkaline earth metal nitrate solutions as mobile phases

The TLC behavior of all the rare earths except Pm has been surveyed on silica gel (pH 7.0) pretreated with 0.1 mol L(-1) tris(hydroxymethyl)aminomethane and 0.1 mol L(-1) HCl with aqueous nitrate solutions of alkaline earth metals as mobile phases. The RF values of the lanthanides varied in a regular and characteristic way accompanied by the tetrad effect with increasing atomic number, and when the mobile phases were changed the RF values of each metal decreased in the order Mg2+ > Ca2+ > Sr2+ > Ba2+, as the crystal ionic radii of the alkaline earth metals increased. This adsorption sequence was not observed with alkali metal nitrate and alkali metal chloride mobile phases. A brief discussion concerning the effect on RF values of the solvent cations and the adsorption mechanism is included; also presented are typical chromatograms for the separation of multi-component mixtures containing adjacent lanthanides.     

Thin-layer chromatographic behavior of rare earths on silica gel with aqueous alkaline earth metal nitrate solutions as mobile phases

The TLC behavior of all the rare earths except Pm has been surveyed on silica gel (pH 7.0) pretreated with 0.1 mol L^–1 tris(hydroxymethyl)aminomethane and 0.1 mol L^–1 HCl with aqueous nitrate solutions of alkaline earth metals as mobile phases. The R_F values of the lanthanides varied in a regular and characteristic way accompanied by the tetrad effect with increasing atomic number, and when the mobile phases were changed the R_F values of each metal decreased in the order Mg²⁺ > Ca²⁺ > Sr²⁺ > Ba²⁺, as the crystal ionic radii of the alkaline earth metals increased. This adsorption sequence was not observed with alkali metal nitrate and alkali metal chloride mobile phases. A brief discussion concerning the effect on R_F values of the solvent cations and the adsorption mechanism is included; also presented are typical chromatograms for the separation of multi-component mixtures containing adjacent lanthanides. Received: 9 October 2000 / Revised: 20 February 2001 / Accepted: 26 February 2001     

Activation analysis of rare earths : Separation of rare earths from accompanying elements

A scheme for the separation of rare-earth elements from gadolinite and tantalocolumbite minerals is discussed. The possibility of interference from traces of nonseparated elements in the subsequent separation of rare-earth elements from each other by cation exchange with α-hydroxyisobutyrate as the eluting agent is investigated.     

Electrodeposition studies of rare earths

The combination of neutron activation analysis (NAA) and electrochemistry has been used to study the deposition behavior of rare earth elements, as it is reported that excepting La, no other rare earths are electrodeposited. The radiotracers of rare earth elements were electrolyzed in an aqueous medium on a graphite electrode by varying the voltage and time of electrodeposition, thereby optimizing the final experimental conditions for quantitative deposition of rare earth elements. The observations are reported in this work.     

Activation analysis of rare earths : The determination of rare earths in minerals by the single comparator technique

The determination of rare earths in minerals by activation analysis is described. The rare earths are separated as a group from the bulk of the material before irradiation. After irradiation the rare earths are separated from each other by gradient elution with ammonium α-hydroxyisobutyrate on a cation-exchange column. The elements are determined by the single comparator technique. This method permits a practical application of activation analysis to the routine determination of rare earths in complex matrices,     

Separation of thorium from rare earths

Summary A method for separation of thorium from rare earths in monazite based on the difference of stability of EDTA complexes towards oxine is described.     

Separation of cephalosporins on thin silica gel layers impregnated with transition metal ions and by reversed-phase TLC

Cephalosporin antibiotics were separated on thin layer plates impregnated with transition metal ions, Mn(2+), Fe(2+), Co(2+), Ni(2+) and Cu(2+), using different concentrations. Various solvent systems were developed for the study and were used for separation of these analytes. Impregnation was observed to have an effect on hR(F) values, removed tailing of analytes and improved the resolution. The results have been discussed for each metal ion and compared, and the best conditions of separation have been identified. Activation time of thin layer plates impregnated with 0.1% FeSO(4) was found to affect both hR(F) values and resolution of cephalosporins. New solvent systems are reported for both normal phase and reversed-phase TLC.     

Sorption behaviour of some actinides on silica gel from mineral acids and alcoholic solutions

Sorption of Th, Pa, U, Np and Pu on silica gel from HNO₃, HCl and HCl−ROH solutions was investigated. Equilibrium studies indicated sorption behaviour to vary greatly with the acid used. In mixtures of HCl with different alcohols, distribution coefficints were found to depend on alcohol percentage as well as on acidity. Results were discussed and conditions for possible separations were indicated.     

Neutron activation analysis of heavy rare earths

A method of nondestructive activation analysis of heavy rare earth elements (Sm−Lu) is described. Intensities of γ-ray peaks are compared to that of an internal reference after irradiations by both thermal and fission spectrum neutrons. Results are obtained from computer comparisons of peak areas. Work was performed at the Ames Laboratory of the U.S. Atomic Energy Commission. Contribution No. 2895.     

Ion-exchange chromatography of glycolatocomplexes of rare earths

Summary The ion-exchange behavior of glycolatocomplexes of the rare earths (Sc, Y and lanthanides) with 1-octanesulfonate as the hydrophobic ion has been investigated in aqueous glycolate media. The system is capable of separating adjacent light intra rare earths, La-Ce-Pr-Nd-Y-Sm, and heavy rare earths, Ho-Er-Tm-Yb-Lu-Sc, from each other with good resolution by gradient elution at room temperature. Intermediate rare earths, Dy-Tb-Gd-Eu-Sm, are difficult to separate from each other. The position of Y in the eluate is different from that found with most other eluent systems used for rare earth separations, being between Nd and Sm.