241Am-XRF analysis of rare earths in geological samples

Rare earths in sediments are analyzed by X-ray fluorescence using²⁴¹Am as an excitation source. The analytical sensitivity lies in the ppm range.     

Determination of rare earths in geological samples by neutron activation analysis

The significance of rare earth distribution patterns in trace element geochemistry is briefly reviewed. Established methods for their determination at the Reactor Centre by instrumental and radiochemical techniques are described, and examples of recent applications discussed.     

Review of methods for the determination of lanthanides in geological samples

The following methods of determining lanthanides in geological samples are reviewed, together with the separation techniques necessarily associated with them: neutron-activation analysis, atomic-absorption and flame-emission spectrometry, plasma-source emission spectrometry, mass spectrometry, X-ray fluorescence spectrometry, and spectrophotometry.     

Potentiometric determination of rare earths with sodium ortho-vanadate

Ohne Zusammenfassung     

Spectrographic determination of the rare earths in high-purity graphite

A spectrographic method has been developed for determination of the rare-earth elements in graphite. The rare earths are concentrated from ignited graphite on a calcium base. The impurities (Fe, V, Mn, Al, Ti) associated with the rare earths are separated by precipitation of the rare earths as hydroxides in the presence of Fe as a carrier, followed by precipitation of the rare earths as oxalates in the presence of Ca carrier. The mixture of calcium and rare-earth oxides obtained after ignition of the corresponding oxalates is mixed with graphite in 1:1 ratio and excited in a 15-A d.c. arc, with Nd as internal standard. The concentration ranges of determination are as follows: 0.006-0.125 ppm for Eu, 0.006-0.25 ppm for Gd, 0.006-0.06 ppm for Dy, 0.06-0.5 ppm for Sm. This sensitivity is achieved with 35-g samples of graphite. Higher enrichment factors are needed in order to enhance the sensitivity of the method.     

Potentiometric determination of rare earths with sodium tungstate

Ohne Zusammenfassung     

Solvent extraction-spectrophotometric determination of rare earths with chlorophosphonazo-III

The rare-earth chlorophosphonazo III chelates are easily extracted from an aqueous solution (pH 1.1-1.5) into n-butanol. The absorbance at the absorption maximum (at 668 nm) is about 3 times that in aqueous solution. The spectrophotometric determination of rare earths has been investigated.     

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 and gravimetric determination of rare earths with N-m-Tolyl-m-nitrobenzohydroxamic acid

N-m-Tolyl-m-nitrobenzohydroxamic acid is used as a reagent for separation and gravimetric determination of Ce(3+), La(3+), Pr(3+), Nd(3+), Sm(3+) and Gd(3+). By proper control of pH and use of masking agents these metal ions can be separated from several others and determined gravimetrically. The complexes can be weighed as (C(14)H(11)N(2)O(4))(3)M after drying.     

Simultaneous spectrofluorimetric determination of the rare earths with calcein

The reactivity of the fluorescent reagent calcein with the trivalent cations of the rare earths has been spectrofluorimetrically studied in aqueous solution. Optimum excitation and emission wavelengths were 492-497 and 519-522 nm, respectively. Optimum pH was in the range 6.0-9.2. The stoichiometry of the complexes was 1:1. A direct, rapid and sensitive method for the determination of rare earth mixtures has been proposed with a detection limit of 4.49x10(-8) M and a coefficient of variation of 0.82%.     

Electrothermal atomisation for atomic-absorption determination of some rare earths in silicate rocks and minerals

Summary The interfering effects due to the composition of the silicate matrix of a common geological sample have been overcome by an ion-exchange separation procedure.The early described cation-exchange device allows a complete separation of the rare earth element group (plus barium, yttrium and scandium) from the major and minor elements of the matrix (i. e. calcium, iron, aluminium, sodium, etc.).Some analytical flameless atomic absorption procedures have been carried out on the eluate fraction: dysprosium, holmium, thulium, ytterbium and europium are determined in international standard rocks and minerals. The REE (rare earth elements) values fall well into the range reported in literature.

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Elektrothermische Zerstäubung einiger Seltener Erden in Silikatgesteinen und Mineralen zum Zweck ihrer Bestimmung durch AAS

Zusammenfassung Die auf die Zusammensetzung von Silikaten zurückzuführenden Störungen bei der Analyse gewöhnlicher geologischer Proben lassen sich durch Ionenaustausch beseitigen. Der früher beschriebene Kationenaustausch ermöglicht die vollständige Abtrennung der Seltenen Erden (mit Barium, Yttrium und Scandium) von den Haupt- und Nebenbestandteilen der Matrix (d. h. Calcium, Eisen, Aluminium, Natrium usw.). Einige Verfahren zur analytischen AAS des Eluats wurden ausgearbeitet. Dysprosium, Holmium, Thulium, Ytterbium und Europium wurden in internationalen Standard-Gesteinsproben bestimmt. Die Ergebnisse liegen gut im Bereich der Literaturangaben.

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Presented at the 8th International Microchemical Symposium, Graz, August 25–30, 1980.

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This work was carried out with a financial contribution of the Consiglio Nazionale delle Ricerche of Italy.     

Preconcentration of rare earths in geological materials with ascorbic acid for their neutron activation analysis

The potential use of ascorbic acid as a complexing reagent in the separation and preconcentration of rare earth elements (REE) in geological materials in a suitable solid matrix has been demonstrated. Traces of REE from some USGS standard rock samples, viz., GSP-1, G-2, AGV-1 and PCC-1, have been separated after acid dissolution in two ways: (1) by ion exchange chromatography on Dowex 50×8 column and Na-ascorbate as eluent and (2) by direct complexation with ascorbic acid under specific experimental conditions. The separated REE were coprecipitated with the non isotopic diluent, calcium fluoride, before neutron activation analysis. Radiometric determinations showed that the overall recovery of REE in both cases was practically quantitative.     

An extraction-photometric method for the determination of rare earths using mixed ligands

Summary A new procedure has been developed for the photometric determination of rare-earth metal ions with 4-(2-pyridyl azo)resorcinol (PAR), antipyrine and perchlorate and extraction into nitrobenzene of the mixed ligand complex formed at pH 6.5. Optimum conditions for the photometric determination, Beer's law range, sensitivity of the colour reaction, photometric precision and the interference of various foreign ions are reported. The method is simple, sensitive and fairly accurate. The composition of the mixed-ligand complexes and their conditional extraction constants have been determined.

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Eine Methode zur Extraktion und photometrischen Bestimmung Seltener Erden mit gemischten Liganden

Zusammenfassung Ein neues Verfahren zur photometrischen Bestimmung Seltener Erden mit 4-(2-Pyridylazo)~resorcin (PAR), Antipyrin und Perchlorat nach Extraktion der Komplexverbindung bei pH 6,5 mit Nitrobenzol wurde beschrieben. Die optimalen Arbeitsbedingungen, das Gültigkeitsgebiet des Beerschen Gesetzes, die Empfindlichkeit der Farbreaktion, die photometrische Genauigkeit und die Störung durch verschiedene Fremdionen wurden be- schrieben. Das Verfahren ist einfach, empfindlich und genau. Die Zusammensetzung der Komplexverbindungen und deren jeweilige Extraktionskonstanten wurden ermittelt.

     

Comparative study of activation analyses for the determination of trace halogens in geological and cosmochemical samples.

Halogens (fluorine, chlorine, bromine and iodine) were determined by activation analyses (neutron activation analysis (NAA), photon activation analysis (PAA) and prompt gamma-ray analysis (PGA)) for geological and cosmochemical solid samples. We studied how each analytical method was for the determination of trace amounts of halogens in rock samples. Radiochemical NAA (RNAA) showed the highest analytical reliability for three halogens (chlorine, bromine and iodine), whereas a set of four halogens (fluorine, chlorine, bromine and iodine) could be determined in principle by radiochemical PAA (RPAA) from a single specimen. Although it is a non-destructive method, PGA showed an analytical sensitivity for chlorine comparable to those of RNAA and RPAA.     

Successive determination of thorium and the rare earths with triethylenetetraminehexaacetic acid

Triethylenetetraminehexaacetic acid (TTHA) is proposed for the successive determination of thorium and rare earths in mixtures by titrating first for thorium at pH 2, then adding an excess of TTHA to complex the rare earth ions completely, and titrating the excess of TTHA with standard zinc solution. Xylenol Orange and 3',3'-bis {[N,N-bis (carboxymethy 1)amino]methyl} thymolsulphonephthalein (TMS) have been tested as indicators for the titration.     

Substoichiometric determination of heavy rare earths by isotopic dilution analysis

A substoichiometric method for the determination of heavy rare earths (holmium, thulium) has been developed. After the addition of a substoichiometric amount of EDTA to the test sample of rare earth labelled with its radioactive isotopes, the negatively charged complex formed was separated by passage through a column of Dowex 50 x 8. Interfering metals can be removed by preliminary cupferron and diethylammonium diethyldithiocarbamate extraction. Concentrations of rare earth down to 4 x 10(-7)g 5 ml have been determined.     

A note on successive complexometric determination of thorium and rare earths

An improved method for successive determination of thorium and rare earths is described. It is based on the EDTA titration of thorium at pH 2 (Xylenol Orange as indicator) followed by addition of acetylacetone-acetone mixture, adjustment of the pH to 5-5.5 with hexamine, and by further EDTA titration of rare earths with the same indicator.     

遗传-因子分析光度法用于地质样品中15个稀土元素同时测定的研究

遗传因子分析方法（GFA）综合了遗传算法（GA）和迭代目标因子分析法（FA）的优点，不仅实现了校准模型的动态化，而且解决了多组分同时测定时收敛滞缓的问题。遗传-因子分析方法应用于15种稀土的同时测定，提高了分析结果的准确度。