Study on the Spectrophotometric Determination of Rare Earths with a New Chromogenic Reagent Dibromo-p-methyl-chlorosulfonazo(DBMCSA)

IntroductionAbstract:Anewmethodforthedeterminationofceriumsubgrouprareearthswasstudiedandreportedinthispaper.ItwasfoundthaiceriumsubgrouprareearthelementsreactwithDBMCSAin0.6mol/Lhydrochloricacidmediumtol'ormstablebluecomplexes.Theabsorbancesofequalamountsofceriumsubgrouprareearthsareclosetoeachotherattheirmaximumadsorptivewavelength(641"m).Beer'slawisobeyedfor0-20igofrareearthsin25mlofsolution.Themethodhasbeenappliedtothedeterminationofthetotalamountofceriumsubgrouprareearthsinsteelandcas…     

稀土-氨基J酸偶氮氯膦-氯代十四烷基吡啶-乙醇多元络合物的研究及分析应用

本文研究了氨基-J酸偶氮氯膦在阳离子表面活性剂存在下与稀土元素形成多元络合物的显色反应,并进行了实样分析。     

铈(Ⅲ)-三乙四胺六乙酸的配合物及其应用于铈的导数分光光度测定

多氨基多羧酸可与稀土离子生成稳定的配合物,EDTA、二乙三胺五乙酸(DTPA)和四乙五胺七乙酸(TPHA)曾用于测定某些单一稀土,但铈(Ⅲ)的测定尚未见报道.本文研究了三乙四胺六乙酸(TTHA)与铈(Ⅲ)的配合物在紫外区的吸收光谱,用导数分光光度法选择测定了混合稀土氧化物中铈的含量。     

钪-稀土-对乙酰基偶氮氯膦体系共显色效应的研究

钪－稀土－对乙酰基偶氮氯膦体系共显色效应的研究刘双成,徐钟隽,潘教麦（华东师范大学化学系,上海,２０００６２）关键词钪,稀土,对乙酰基偶氮氯膦,共显色效应不则称偶氮氯膦试剂与稀土元素的β型显色反应,已被广泛用于稀土的测定［１,２］．但是当多种稀土或某...     

Spectrophotometric determination of cerium with sulphanilic acid

In the presence of other rare earths, cerium(IV) can be determined spectrophotometrically by its reaction with sulphanilic acid with which it produces a red colour. Solutions containing 28-210 ppm of cerium absorb at 495 mmicro according to Beer's law. Other rare earths, except neodymium, and many common ions do not interfere. Strong oxidising agents and neodymium in greater than fifty times the concentration of cerium interfere with this method. The precision depends on the control of pH and time. Cerium alloys have been analysed by this method and the results are compared with those obtained by another spectrophotometric method.     

Simultaneous determination of lanthanum and cerium in mixed rare earths with p-acetylarsenazo by spectrophotometry

A new method has been developed for the simultaneous spectrophotometric determination of small amounts of lanthanum and cerium in the presence of large amounts of rare earth elements. Lanthanum (III) and cerium (III) were determined spectrophotometrically with p-acetylarsenazo as the color reagent in the chloroacetic acid medium at pH 3.1 by measuring the absorbances of the complexes at 670 nm. The remained rare earths were masked with ethylenediaminetetracetic acid and ethylenediaminetetracetic acid-zinc during the analysis. The optimum conditions for the simultaneous determination of lanthanum and cerium have been defined. The individual content of lanthanum (III) and cerium (III) were determined by varying the amounts of EDTA and EDTA-Zn used in the analysis and solving the simultaneous absorbance equations based on the Beer's law. The proposed method has been successfully applied to the determination of lanthanum and cerium in Longnan mixed rare earth oxides and other heavy rare earths without preliminary separation with satisfactory results. The relative errors of all analytical results of the method were not more than 2% with good precision. The procedure does not require separation of lanthanum, cerium and the other rare earth elements.     

Simultaneous spectrophotometric determination of thorium and rare earth metals with m-carboxychlorophosphonazo (CPAmK) and cetylpyridinium chloride

Th and rare earth elements (REE) react with m-carboxychlorophosphonazo (CPAmK) in the absence of cetylpyridinium chloride (CPC) to form colour complexes. The molar absorptivities for Th and Ce are 1.03 x 10(5) and 1.06 x 10(5) 1.mole(-1).cm(-1) respectively. In the presence of CPC, REE-complexes are not formed because of micellar masking, while Th gives a more sensitive reaction with CPAmK ( = 1.50 x 10(5)). Most of the foreign ions are tolerated in considerable amounts; 360-1000-fold amounts of rare earths do not interfere with the determination of Th. The optimum conditions of the complex-formation reactions and the compositions of Th-CPAmK complexes are described. A simple method is proposed for simultaneous determination of Th and rare earths without previous separation.     

Spectrophotometric study and analytical application of rare-earth Tiron complexes-II Determination of europium

The absorption spectra of europium-Tiron complexes in aqueous solution have been measured from 340 to 600 nm. The absorbance at 390 and 420 nm follows Beer's law up to 0.8 mg ml (pH 6.2-6.6). Other rare earths except for cerium(III) did not interfere. The interference of cerium could be removed by addition of ascorbic acid. The combining ratio of Tiron to europium has been found to be 1:1.     

Enrichment of trace cerium subgroup rare earths by means of ion flotation

The possibility of ion flotation of cerium subgroup rare earths (Ce-subgroup) wasexplored. Various factors affecting the flotation efficiency were investigated. The results showedthat, by using sodium tetradecyl sulfate as the collector of trace Ce-subgroup and frother, over 95%of Ce-subgroup at ng/g levels could be separated from pH 2.3 media in 10--15 min. The proposedmethod has been applied to the determination of Ce-subgroup in a polluted farmland soil referencematerial (GBW 08303) with satisfactory results.     

Spectrophotometric determination of scandium based on the cocoloration effect in scandium-cerium-p-acetylchlorophosphonazo (CPApA) system

Scandium in the presence of cerium(III) forms, with p-acetylchlorophosphonazo (CPApA), a heteropolynuclei ternary β-complex of scandium-cerium-CPApA. The complex gives a very sensitive reaction for scandium with a molar absorptivity of _Sc = 2.29 × 10⁵ l mol⁻¹ cm⁻¹ due to the cocoloration effect. Most foreign ions can be tolerated in considerable amounts. The optimum conditions and the mechanism of the complex formation reaction are discussed. A simple method is proposed for the determination of scandium in alloys, with satisfactory results.     

Ensuring complete absence of Ce(IV) and measurement of the stability constant of the fluoride complex of Ce(III)

Literature survey revealed a wide variation in the measured stability constant values of the aqueous fluoride complexes of trivalent cerium. This could be due to inadequate care for full conversion and maintenance of the oxidation state of cerium to trivalent state. In the present work quinhydrone has been used to ensure complete absence of Ce(IV) and the stability constant of CeF(2+) in 1 M NaClO(4) has been measured potentiometrically using a fluoride ion selective electrode. Log beta(1) obtained in this work was 2.936+/-0.024 and fitted well with the general trend of stability constants of the lanthanide (rare earths) fluorides in aqueous solution.     

稀土离子选择电极在非线性响应区域响应特性及其数学模拟

离子选择电极(ISE)通常是基于能斯特响应来测定离子活度或浓度的。每一种ISE都存在着一个线性电位响应区域。为了满足线性响应的要求,待测组份浓度,介质酸碱度及共存的其它组份均受到较严格的限制。而许多实际体系(如混合稀土萃取体系)十分复杂,不仅待测组份浓度高,而且共存组份多,酸度变化也较大,电极在这类体系中常呈非线性响应。本工作报导CeO₂膜稀土ISE在非线性响应区域对单一稀土和混合稀土的响应特性,和半经验数学模型的探讨。     

Identification of cerium in the presence of other rare earths

In the presence of other rare earths, cerium is best identified with redox indicators. p-Sulfanilic acid is a fairly specific indicator for cerium(IV), giving a red coloration with more than 6 p.p.m. o-Tolidine and diphenylamine sulfonate can identify smaller amounts of cerium(IV), but many oxidants interfere.     

A study of fast reactions of trilon B with colored complexes formed by Xylenol orange with rare earth elements of the cerium subgroup

The stopped-flow method has been used to study the reaction of Trilon B with the colored complexes formed by Xylenol Orange with the rare earth elements of the cerium subgroup. It has been shown that the limiting stage in this reaction is the stage involving dissociation of the colored complex. The rate constants and energy and entropy of activation of the dissociation of the complexes formed by the rare earth elements of the cerium subgroup with Xylenol Orange have been determined.     

Photochemical precipitation of thorium and cerium and their separation from other ions in aqueous solution

Thorium was precipitated from homogeneous solution by exposing solutions of thorium and periodate in dilute perchloric acid to 253.7 nm radiation from a low-pressure mercury lamp. Periodate is reduced photochemically to iodate which causes the formation of a dense precipitate of the basic iodate of thorium(IV). The precipitate was redissolved, the iodate reduced, the thorium precipitated first as the hydroxide, then as the oxalate and ignited to the dioxide for weighing. Thorium(IV) solutions containing 8-200 mg of ThO(2) gave quantitative results with a standard deviation (s) of 0.2 mg. Separations from 25 mg each of iron, calcium, magnesium, 50 mg of yttrium and up to 500 mg of uranium(VI) were quantitative (s = 0.25 mg). Separations from rare earths, except cerium, were accomplished by using hexamethylenetetramine rather than ammonia for the precipitation of the hydroxide. Cerium(III) was similarly precipitated and converted into CeO(2) for weighing. Quantitative results were obtained for 13-150 mg of CeO(2) with a standard deviation of 0.2 mg. Separations from 200 mg of uranium were quantitative. Other rare earths and yttrium interfered seriously. The precipitates of the basic cerium(IV) and thorium iodates obtained are more compact than those obtained by direct precipitation and can be handled easily. Attempts to duplicate Suzuki's method for separating cerium from neodymium and yttrium were not successful.     

Derivative spectrophotometric determination of praseodymium in rare earth mixtures with lomefloxacin

Praseodymium forms a Pr(LMFX)(3) complex with lomefloxacin. In this paper, the absorption spectra of the complex has been investigated by applying conventional and derivative spectrophotometric methods. It was found that lomefloxacin could form a stable complex with praseodymium in the pH 6.5-8.5 media. The absorption intensity of the complex is 4.5-fold more than PrCl(3). Using the second derivative spectra, the sensitivity is 7.4 times higher for Pr than in the normal method (zero derivative spectra). The second derivative spectrophotometry for determination of praseodymium in the presence of other rare earths has been developed. The calibration curves were linear in the range of 3.5-65 mug ml(-1) for Pr. The detection limit is 0.85 mug ml(-1). The method is satisfactory for the determination of praseodymium in mixed rare earths.     

The determination of lanthanum,cerium and thorium without separations: The determination of lanthanum and cerium in thorium

A method is proposed for the spectrophotometric determination of small quantities of lanthanum, cerium and thorium in the presence of one another without separations. Cerium is estimated from its absorption peak in the ultraviolet region, thorium with thorin, and the 3 elements together with arsenazo. The lanthanum is calculated after subtraction of the combined absorbances of the arsenazo complexes of the thorium and cerium. The procedure can be readily applied to the determination of microgram amounts of the 2 rare earths in thorium. In this case the majority of the thorium is removed from the solution by solvent extraction with TTA before the estimation of the rare earths. The interference of iron is considered and proposals made for its removal.     

Dynamic ion-exchange chromatography with post-column reaction detection for the determination of the rare earth elements in monazites

Summary Separation and determination of lanthanum, cerium, praseodymium, neodymium and samarium in monazites have been achieved by dynamic ion-exchange chromatography. The ore samples are decomposed by sulfuric acid and the rare earths are separated in a group as oxalates. The rare earth elements are then separated from each other on a column of bonded phase silica by gradient elution with 0.05 to 0.5 M lactic acid (pH 3.5) in the presence of 0.01 M sodium 1-octanesulfonate. Post-column reaction with Arsenazo III is used for detection and quantification of the individual rare earth elements. Results are quoted for lanthanum, cerium, praseodymium, neodymium and samarium in monazites. Detection limit is 1 μg ml⁻¹ with a S/N ratio of 3. The separation is complete within 27 min valley to valley resolution. Precision of better than 1% can usually be obtained.     

Extraction of rare earth elements with 1-(diphenylphosphorylmethoxy)-2-diphenylphosphoryl-4-ethylbenzene with the use of 1,1,7-trihydrododecafluoroheptanol as a solvent

Extraction of rare earth elements from nitric acid solutions in a 1,1,7-trihydrododecafluoroheptanol-water system with the use of phosphoryl-containing podand 1-(diphenylphosphorylmethoxy)-2-diphenylphosphoryl-4-ethylbenzene (L) was studied. The content of metals in organic phase was shown to be negligible at nitric acid concentration lower 1 mol/L. Distribution ratio sharply increases with nitric acid concentration from 1 mol/L and reaches 5.5 for the yttrium subgroup elements at HNO₃ concentration of 6 mol/L. The rare earth elements of the yttrium subgroup were found to be extracted much better than the rare earth elements of the cerium subgroup under the same conditions, the distribution ratios in both subgroups smoothly rise with atomic number of element. It was shown using the shift of extraction equilibrium that the M: L ratio in extracted complexes is 1: 2 irrespective of the nature of rare earth element. The structure of complex {Yb[η²-(O,O′)-L]₂(η²-O₂NO)₂}(O₂NOHNO₃), whose single crystals were isolated from extraction solution, was established by X-ray diffraction study. The system can be used for the isolation and separation of rare earth elements.     

Study of the absorption spectra of the 4f electron transitions of the praseodymium complex with ciprofloxacin and its analytical application

Ciprofloxacin (CPFX) is proposed as a reagent for the derivative spectrophotometric determination of praseodymium in mixed rare earths. The absorption spectra of 4f electron transitions of the praseodymium complex with CPFX was studied by normal and derivative spectrophotometry. The stoichiometry of the praseodymium-CPFX complex was calculated by the molar ratio and continuous variations methods. A ratio of Pr to CPFX of 1:3 was found. The absorption bands of the 4f electron transitions of the complex were enhanced markedly. Using the third derivative spectrum. Beer's law was obeyed up to 35 microg cm(-3) of praseodymium. The relative standard deviation is 0.62% for 14 microg cm(-3) of praseodymium. The detection and quantification limits were 0.17 and 0.56 microg cm(-3) of praseodymium, respectively. A method for the direct determination of praseodymium in mixtures of rare earths with good accuracy and selectivity is described.