The titrimetric determination of calcium and magnesium in silicate rocks

A cation-exchange scheme is described for the separation of calcium and magnesium from interfering elements in rapid silicate analysis. Interfering elements can be eluted from the ammonium form of Zeo-Karb 225 with a solution of the ammonium salt of ethylenediaminetetraacetic acid at pH 4.5. Calcium and magnesium are not eluted with this reagent but can be eluted consecutively with ammonium chloride solution and titrated photometrically with EDTA. Calcium and magnesium can be separated quantitatively from Al, Fe, Ti, Mn, Bi, Cd, Cr, Co, Cu, Pb, Mo, Ni, U, V, rare earths, and Zn.     

Liquid-liquid extraction separation and sequential determination of plutonium and americium in environmental samples by alpha-spectrometry

A procedure is described by which plutonium and americium can be determined in environmental samples. The sample is leached with nitric acid and hydrogen peroxide, and the two elements are co-precipitated with ferric hydroxide and calcium oxalate. The calcium oxalate is incinerated at 450 degrees and the ash is dissolved in nitric acid. Plutonium is extracted with tri-n-octylamine solution in xylene from 4M nitric acid and stripped with ammonium iodide/hydrochloric acid. Americium is extracted with thenoyltrifluoroacetone solution in xylene at pH 4 together with rare-earth elements and stripped with 1M nitric acid. Americium and the rare-earth elements thus separated are sorbed on Dowex 1 x 4 resin from 1M nitric acid in 93% methanol, the rare-earth elements are eluted with 0.1M hydrochloric acid/0.5M ammonium thiocyanate/80% methanol and the americium is finally eluted with 1.5M hydrochloric acid in 86% methanol. Plutonium and americium in each fraction are electro-deposited and determined by alpha-spectrometry. Overall average recoveries are 81% for plutonium and 59% for americium.     

Separation and electrodeposition of226Ra

The chemical behavior of calcium, barium and radium in the ion exchange resins Dowex 50W-X8, AG 50W-X8 and Merk I in the presence of ammonium tartrate, EDTA, and citrate has been studied. No differences were observed in results while using any one of the three resins. Calcium, barium and radium were fixed to the exchange column at pH 4.8 EDTA solution. Calcium was eluted in an EDTA solution at pH 5.3, barium and radium between pH 8–11. Elution in citrate media for calcium was achieved at pH 6.1 and for radium at pH 10. In ammonium tartrate, calcium was eluted at pH 6, barium and radium at pH 11.5. Radium was also eluted from the ion exchange resins with a 2M nitric acid solution. The radium free of calcium was electrodeposited onto a stainless steel disc cathode using a 0.1 M potassium fluoride solution, pH 12–14, with a yield of >50%. The energies of²²⁶Ra were analyzed through high resolution -spectra. The²²⁶Ra utilized for these experiments was separated from Mexican carnotite.     

Atomic-absorption determination of beryllium in liquid environmental samples

A method is described for the atomic-absorption determination of beryllium in liquid environmental samples after separation by solvent extraction and cation-exchange. The beryllium is first isolated from natural waters and beverages by chloroform extraction of its acetylacetonate from a solution at pH 7 and containing EDTA. The chloroform extract is then mixed in the ratio of 3:6:1 with tetrahydrofuran and methanol containing nitric acid, and passed through a column of Dowex 50 x 8 (H(+)-form). After removal of acetylacetone, chloroform and tetrahydrofuran by washing the resin bed with methanol-HNO(3), beryllium is eluted with 6M hydrochloric acid and determined by atomic-absorption spectroscopy. The method was successfully applied to determine beryllium in tap-, river- and sea-water samples, mineral waters and wines. Beryllium contents in the range from < 0.01 to 2.3 microg/l were found in these materials.     

Chemical analysis of manganese nodules : Part II. Determination of uranium and thorium after anion-exchange separation

A method is described for the determination of uranium and thorium in manganese nodules. After dissolution of the sample in a mixture of perchloric and hydrofluoric acids, uranium is adsorbed on the strongly basic anion-exchange resin Dowex 1 (chloride form) from 6 M hydrochloric acid. The effluent is evaporated and the residue is taken up in 7 M nitric acid—0.25 M oxalic acid; thorium is then isolated quantitatively by anion-exchange on Dowex 1 (nitrate form). Thorium is eluted with 6 M hydrochloric acid and determined spectrophotometrically by the arsenazo III method. Uranium is eluted from the resin in the chloride form with 1 M hydrochloric acid and then separated from iron, molybdenum and other co-eluted elements on a column of Dowex 1 (chloride form); the medium consists of 50% (v/v) tetrahydrofuran, 40% (v/v) methyl glycol and 10% (vv) 6 M hydrochloric acid. After removal of iron and molybdenum by washing the resin with a mixture of the same composition and with pure aqueous 1 M hydrochloric acid, the adsorbed uranium is eluted with 1 M hydrochloric acid and determined by fluorimetry. The method was used successfully for the determination of ppm-quantities of uranium and thorium in 60 samples of manganese nodules from the Pacific Ocean.     

Application of ion-exchange separations to determination of trace elements in natural waters-IX: simultaneous isolation and determination of uranium and thorium

A method is described for the determination of uranium and thorium in samples of natural waters. After acidification with citric acid the water sample is filtered and sodium citrate and ascorbic acid are added. The resulting solution of pH 3 is passed through a 4-g column of Dowex 1 x 8 (citrate form) on which both uranium and thorium are adsorbed as anionic citrate complexes. Thorium is eluted with 8M hydrochloric acid and separated from co-eluted substances by anion-exchange in 8M nitric acid medium on a separate 2-g column of the same resin in the nitrate form. After complete removal of iron by washing with a mixture consisting of IBMK, acetone and 1M hydrochloric acid (1:8:1 v v ) and treatment of the resin with 6M hydrochloric acid, the uranium is eluted from the 4-g column with 1M hydrochloric acid. In the eluate thorium is determined spectrophotometrically (arsenazo III method) while fluorimetry is employed for the assay of uranium. The procedure was used for the determination of uranium and thorium in numerous water samples collected in Austria, including samples of mineral-waters. The results indicate that a simple relationship exists between the uranium and thorium contents of waters which makes it possible to calculate the approximate thorium content of a sample on the basis of its uranium concentration and vice versa.     

Anion exchange studies of lead in chloride and malonate solutions separation from mixtures

Summary Lead forms anionic chloride complexes in 4 M hydrochloric acid and a malonate complex at pH 4.8 with malonic acid. The behaviour of these complexes has been studied on Dowex 21-K resin with various eluants and methods have been developed for the separation of lead from several elements. The technique has been extended to the analysis of lead-based alloys. Satisfactory results are obtained.

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Zusammenfassung Die anionischen Chlorid- und Malonatkomplexe des Bleis wurden in ihrem Verhalten am Ionenaustauscher Dowex 21-K untersucht und Methoden zur Abtrennung des Bleis von mehreren anderen Elementen ausgearbeitet. An einem Beispiel wird die Analyse einer Bleilegierung beschrieben. Es werden zufriedenstellende Ergebnisse erhalten.

     

Atomic-absorption determination of vanadium and molybdenum in tap water and mineral waters after anion-exchange separation.

A method is described for the determination of vanadium and molybdenum in samples of tap and bottled mineral water. After acidification with citric acid the water sample is heated to about 80°C to remove CO₂; sodium citrate and ascorbic acid are added and the resulting solution of pH 3 is passed through a column of the strongly basic anion-exchange resin Dowex 1-X8 (citrate form) on which both vanadium and molybdenum are adsorbed as anionic citrate complexes. Vanadium is eluted with 6 M hydrochloric acid; molybdenum is recovered with 2 M perchloric acid-1 M hydrochloric acid. Vanadium and molybdenum are determined in the eluates by atomic-absorption spectrometry. The samples analysed contained 0.1–0.9 μg l^?1 vanadium and 0.2–13 μg l^?1 molybdenum.     

Cation-exchange separation of uranium in dimethylsulphoxide medium

Cation-exchange chromatography in a dimethylsulphoxide (DMSO) medium is a suitable means for separating uranium from metal ions, including copper, iron, nickel and molybdenum. Quantitative separations of uranium from 26 elements can best be effected on a column of Dowex 50W-X8 (200-400 mesh), using as the eluent a 20% v/v DMSO solution which is 0.6Min hydrochloric acid and 0.25M in sodium acetate. Only calcium is eluted with the uranium and all other elements studied are eluted either before or after uranium. The elution characteristics of uranium and of other metal ions were investigated with respect to changes in eluent and resin compositions. Separations were much less effective at higher concentrations of sodium ion or DMSO. None of the organic solvents methanol, ethanol, methyl glycol, acetone, dioxan or acetic acid was found to produce favourable separation conditions. Results with Dowex 50 resins of lower or higher cross-linkage were inferior to those obtained with the X8 resin.     

Selective and quantitative separation of zinc and lead from other elements by cation-exchange chromatography in hydrohalic acid-acetone solutions

Zinc and lead can be separated from Cd, Bi(III), In and V(V) by eluting these elements with 0.2M hydrochloric acid in 60% acetone from a column of AG50W-X8 cation-exchange resin, zinc and lead being retained. Mercury(II), Tl(III), As(III), Au(III), Sn(IV), Mo(VI), W(VI) and the platinum metals have not been investigated quantitatively, but from their distribution coefficients, should also be eluted. Vanadium(V), Mo(VI) and W(VI) require the presence of hydrogen peroxide. Zinc and lead can be eluted with 0.5M hydrochloric acid in 60% acetone or 0.5M hydrobromic acid in 65% acetone and determined by AAS; the alkali and alkaline-earth metal ions, Mn(II), Co, Ni, Cu(II), Fe(III), Al, Ga, Cr(III), Ti(IV), Zr, Hf, Th, Sc, Y, La and the lanthanides are retained on the column, except for a small fraction of copper eluted with zinc and lead. Separations are sharp and quantitative. The method has successfully been applied to determination of zinc and lead in three silicate rocks and a sediment.     

Chemical analysis of manganese nodules: Part III. Determination of Thallium,Molybdenum and Vanadium after Anion-Exchange Separation

A method is described for the determination of thallium, molybdenum and vanadium in manganese nodules. After dissolution of the sample in a mixture of perchloric and hydrofluoric acids, thallium and molybdenum are adsorbed on the strongly basic anion-exchange resin Dowex 1 (chloride form) from 6 M hydrochloric acid containing bromine. Molybdenum is eluted with 2 M perchloric acid-1 M hydrochloric acid and determined by a.a.s. with a nitrous oxide—acetylene flame. Thallium is eluted with an aqueous solution of sulphur dioxide and, after evaporation of the eluate, this element is determined by a.a.s. with an air—acetylene flame. The same method is used for the assay of vanadium in the 6 M hydrochloric acid effluent. The method was used successfully for the determination of thallium, molybdenum and vanadium at the ppm level in numerous samples of nodules from the Pacific Ocean and Lake Michigan.     

Improved separation of cadmium-109 from silver cyclotron targets by anion-exchange chromatography in nitric acid—hydrobromic acid mixtures

A method is presented for improved separation of ¹⁰⁹Cd from silver cyclotron targets. After dissolution of the target material in nitric acid and removal of silver by precipitation with copper metal, at pH 5, the cadmium is separated from zinc, copper and other elements by anion exchange chromatography. The solution in 0.5 M nitric acid plus 0.1 M hydrobromic acid is percolated through a column containing 4 ml of AG1-X8 anion-exchange resin (100–200 mesh), equilibrated with the same acid mixture. Zinc, copper(II) and other elements are eluted with 50 ml of this mixture. Cadmium is retained and finally eluted with 50 ml of 3 M nitric acid. The cadmium is retained much more strongly from the hydrobromic acid mixture than from the 0.02 M hydrochloric acid used for such separations previously; the presence of the strongly absorbed nitrate anion in fairly high concentration completely eliminates the tailing of zinc observed in 0.02 M hydrochloric acid. A typical elution curve and results of quantitative separations are presented.     

Adsorption of chloro-complexes of the first row transition elements by Dowex A-1

A study has been made of the adsorption of chlorocomplexes of the first row transition metals by the chelating resin Dowex A-1, and possible mechanisms for adsorption have been reviewed. Relative adsorption follows the series Zn(II) > Co(II) = Fe(III) Cu(II) > Mn(II). Negligible adsorption occurred with Cr(III) and none with V(IV) and Ni(II). Maximum adsorption of Zn(II) occurred from 3M hydrochloric acid and for the other metals from 8M acid.     

Quantitative separation of gallium from zinc, copper, indium, iron(III) and other elements by cation-exchange chromatography in hydrobromic acid-acetone medium

Gallium can be separated from Zn, Cu(II), In, Cd, Pb(II), Bi(III), Au(III), Pt(IV), Pd(II), Tl(III), Sn(IV) and Fe(III) by elution of these elements with 0.50M hydrobromic acid in 80% acetone medium, from a column of AG50W-X4 cation-exchange resin. Gallium is retained and can be eluted with 3M hydrochloric acid. Separations are sharp and quantitative except for iron(III) which shows extensive tailing. With 0.20M hydrobromic acid in 80% acetone as eluting agent, all the species above except iron(III) and copper(II) can be separated from gallium with very large separation factors. Only a 1-g resin column and small elution volumes are required to separate trace amounts and up to 0.5 mmole of gallium from more than 1 g of zinc or the other elements. Hg(II), Rh(III), Ir(IV), Se(IV), Ge(IV), As(III) and Sb(III) have not been investigated, but should be separated together with zinc according to their known distribution coefficients. Relevant elution curves, results for the analysis of synthetic mixtures and for amounts of some elements remaining in the gallium fraction are presented.     

Ion flotation behaviour of thirty-one metal ions in mixed hydrochloric/nitric acid solutions

The ion flotation of 31 metal ions in hydrochloric/nitric acid solution with the cationic surfactant cetylpyridinium chloride was investigated. A 25-ml portion of 0.27-2.87 x 10(-4)M metal ion and 1.8-6.0 x 10(-4)M cetylpyridinium chloride solution in 0.17-3.4M acid mixture ([HCl]:[HNO(3)] = 2.4:1) was subjected to flotation in a cell, 22.5 cm high and 4.0 cm in diameter, for 5 min, with nitrogen bubbles. Ir(IV), Pt(IV), Ge(IV), Sn(IV), Bi(III), Au(III), Tl(III), Pd(II) and Sn(II) were floated from solution in 95-100% yield; Ru(III), Rh(III), Ir(III), Hg(II), Ag(I) and Tl(I) were partly floated, while Cr(VI), Ti(IV), Zr(IV), Ga(III), In(III), Fe(III), Sb(III), Al(III), Mn(II), Fe(II), Co(II), Ni(II), Cu(II), Zn(II), CD(II) and Pb(II) were floated with less than 20% yield. The flotation behaviour of these metal ions in the mixed acid system was compared with that in hydrochloric acid. The flotation is more efficient in the mixed acid system.     

Multifunctional modified silver nanoparticles as ion and pH sensors in aqueous solution

Silver nanoparticles capped with mercaptoacetic acid and 2-aminoethanethiol short-chain alkanethiols were prepared by a one-step method in aqueous solution for monitoring pH and a range of heavy metal ions. The mode of transduction is optical, based on the change in aggregation of the nanoparticles in solution. Because of the different ionic interactions between the modified nanoparticles, these nanoparticle sensors can rapidly detect Pb(2+), Cu(2+) and Fe(2+), with detection limits as low as 1 × 10(-5) M, 5 × 10(-7) M and 5 × 10(-5) M respectively, as well as having the ability to detect Cu(2+) ions from Pb(2+) and Fe(2+). Furthermore, the same functionalised nanoparticles are also sensitive to pH; exhibiting a good linear dynamic response between pH 1 and 10.     

Calcon-modified silica gel sorbent. Application to preconcentration or elimination of trace metals

Silica gel impregnated with a mixture of Aliquat 336 and Calcon was used as chelating sorbent for preconcentration of metals from dilute aqueous solutions and their separation as well as for additional purification of analytical grade sodium and potassium salts from other metals. The relative capacities of sorbent towards 33 metal ions were determined in the pH range 1-9 as well as the concentrations of hydrochloric and perchloric acid eluting the retained metals. It was found that Calcon was not eluted from sorbent with 5M perchloric and 10M hydrochloric acids. The rate of sorption for Mg, Ca, Cu, Zn, Al, Cr(III) and Fe(III) was also studied and it was found that relatively high flow-rates (up to 5 ml/min) can be used for solutions passed through the column. The sorbent was used for preconcentration of traces of some metals from aqueous solutions before their determination by AAS, for separation of metal ion mixtures by column extraction chromatography and for additional purification of potassium chloride solutions used as supporting electrolyte in determination of some heavy metals by anodic stripping voltammetry.     

Application of the fission-track technique to the determination of uranium in natural waters

A procedure for the determination of the uranium content of natural waters is presented. To 100 ml of natural waters, 200 ml of conc. hydrochloric acid are added and this solution is passed through a 6-ml column of Dowex 1-X8. The uranium is eluted with 60 ml of 0.1M hydrochloric acid, and the eluate is evaporated to dryness. The residue is subjected to the fission-track technique described previously. The uranium content of the river waters in Fukuoka City was determined.     

A ratiometric fluorescent chemosensor for iron: discrimination of Fe2+ and Fe3+ and living cell application

A newly designed probe, 6-thiophen-2-yl-5,6-dihydrobenzo[4,5]imidazo-[1,2-c] quinazoline (HL(1)) behaves as a highly selective ratiometric fluorescent sensor for Fe(2+) at pH 4.0-5.0 and Fe(3+) at pH 6.5-8.0 in acetonitrile-HEPES buffer (1/4) (v/v) medium. A decrease in fluorescence at 412 nm and increase in fluorescence at 472 nm with an isoemissive point at 436 nm with the addition of Fe(2+) salt solution is due to the formation of mononuclear Fe(2+) complex [Fe(II)(HL)(ClO(4))(2)(CH(3)CN)(2)] (1) in acetonitrile-HEPES buffer (100 mM, 1/4, v/v) at pH 4.5 and a decrease in fluorescence at 412 nm and increase in fluorescence at 482 nm with an isoemissive point at 445 nm during titration by Fe(3+) salt due to the formation of binary Fe(3+) complex, [Fe(III)(L)(2)(ClO(4))(H(2)O)] (2) with co-solvent at biological pH 7.4 have been established. Binding constants (K(a)) in the solution state were calculated to be 3.88 × 10(5) M(-1) for Fe(2+) and 0.21 × 10(3) M(-1/2) for Fe(3+) and ratiometric detection limits for Fe(2+) and Fe(3+) were found to be 2.0 μM and 3.5 μM, respectively. The probe is a "naked eye" chemosensor for two states of iron. Theoretical calculations were studied to establish the configurations of probe-iron complexes. The sensor is efficient for detecting Fe(3+)in vitro by developing a good image of the biological organelles.     

Determination of uranium in minerals and rocks

A method is described for the determination of uranium in minerals and rocks by spectrophotometry and fluorimetry. After treatment of the sample with hydrochloric acid, uranium is separated from matrix elements by adsorption on a column of the strongly basic anion-exchange resin Dowex 1 x 8 from an organic solvent system consisting of IBMK, tetrahydrofuran and 12M hydrochloric acid (1:8:1 v v ). Following removal of iron, molybdenum and co-adsorbed elements by washing first with the organic solvent system and then with 6M hydrochloric acid, the uranium is eluted with 1M hydrochloric acid. In the eluate, uranium is determined by means of the spectrophotometric arsenazo III method or fluorimetrically. The suitability of the method for the determination of both trace and larger amounts of uranium was tested by analysing numerous geochemical reference samples with uranium contents in the range 10(-1)-10(4) ppm. In practically all cases very good agreement of results was obtained.