Separation of traces of manganese,cobalt, nickel and copper from gram amounts of tellurium by cation-exchange chromatography in hydrochloric acid/acetone media

Traces of Mn(II), Co(II), and Ni(II) and minor amounts (up to 20 mg of these elements are separated from gram amounts of tellurium by cation-exchange chromatography on small columns (3 g) of macroporous AG MP-50 resin or larger colunns (5 g) of microporous AG 50W-X8 resin. The trace elements are retained from 0.5 M HCl containing 70% acetone while tellurium passes through and is eluted completely with this solution. The trace elements are then eluted with 3.0 M HCl and can be determined by atomic absorption spectrometry. Copper (II) can also be separated but requires a 10-g column of AG MP-50 resin. Separations are sharp and quantitative and only microgram amounts of tellurium remain in the trace element fraction when a 3-g sample of tellurium dioxide is taken; 10-μg amounts of the trace elements were separated from such samples and determined with standard deviations of <1%. Relevant elution curves and results for the analysis of synthetic mixtures are presented.     

Selective separation of uranium from other elements by cation-exchange chromatography in hydrobromic acid and hydrochloric acid-acetone mixtures

U(VI) can be separated from Ga, Fe(III), Bi, Pb, Cd, Zn, Cu(II) and Au(III) by quantitative elution with 0.50M HBr in 86% acetone or with 0.35M HBr in 90% acetone from a column of AG50W-X4 cation-exchange resin of 200-400 mesh particle size. U(VI) and many other ions are retained. U(VI) then can be eluted selectively with 0.50M HCl in 83% acetone or with 0.35M HCl in 85% acetone. Co(II), Mn(II), Mg, Ca, Ti(IV), Al, Zr, Th and La are quantitatively retained by the column. These elements then can be eluted with 5M HNO(3). At the higher acid concentration (0.50M) the separation between U(VI) and Li is not satisfactory but is excellent at the lower acid concentration; the U(VI) peak is sharper at the higher acid concentration. Separations are sharp and quantitative, as is demonstrated by results for some synthetic mixtures. Distribution coefficients and elution curves are presented.     

Quantitative separation of traces of lead,cadmium and many other elements from gram amounts of thallium by cation-exchange chromatography

Traces of lead and minor amounts up to 20 mg, can be separated from gram amounts of thallium by cation-exchange chromatography on a column containing only 2 g of AG50W-X4 resin. Thallium passes through the column in 0.1 M HCl in 40% acetone. The retained lead can be eluted with 3 M HCl or HNO₃. Other elements, including Cd, Zn, In, Ga, Cu(II), Fe(III). Mn(II), Co(II). Ni(II), U(VI) and Al, are retained quantitatively with lead. Only Hg(II), Au(III), the platinum metals, bismuth and elements forming oxyanions accompanying thallium. Results for the determination of trace elements in 99.999% pure thallium are presented.     

Quantitative separation of gold from cadmium, indium, zinc and other elements by cation-exchange chromatography in hydrochloric acid-acetone medium

Gold(III) can be separated from Cd, In. Zn, Ni, Cu(II), Mn(II), Co(II), Mg, Ca, Al, Fe(III), Ga and U(VI) by adsorbing these elements on a column of AG50W-X8 sulphonated polystyrene cation-exchange resin from 0.1M HCl containing 60% v v acetone, while Au(III) passes through and can be eluted with the same reagent. Separations are sharp and quantitative. The amounts of gold retained by the resin are between 1 and 2 orders of magnitude lower than encountered during adsorption from aqueous 0.1M HCl. Recoveries for mg amounts of gold are 99.9% or better and for ng amounts are still better than 99%, as shown by radioactive tracer methods. Hg(II), Bi, Sn(IV), the platinum metals and some elements which tend to form oxy-anions in dilute acid accompany gold. All other elements, though not investigated in detail, should be retained, according to their known distribution coefficients. Relevant elution curves, results of quantitative separations of binary mixtures and of recovery tests are presented.     

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.     

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.     

Selective separation of indium from zinc, lead, gallium and many other elements by cation-exchange chromatography in hydrohalic acid-acetone medium

Indium can be separated from Zn, Pb(II), Ga, Ca, Be, Mg, Ti(IV), Mn(II), Fe(III), Al, U(VI), Na, Ni(II) and Co(II) by selective elution with 0.50M hydrochloric acid in 30% aqueous acetone from a column of AG50W-X8 cation-exchange resin, all the other elements being retained by the column. Lithium is included in the elements retained by the column when 0.35M hydrochloric acid in 45% aqueous acetone is used for eluting indium, but the elution of indium is slightly retarded. Ba, Sr, Zr, Hf, Th, Sc, Y, La and the lanthanides, Rb and Cs should also be retained according to their distribution coefficients. Cd, Bi(III), Au(III), Pt(IV), Pd(II), Rh(III), Mo(VI) and W(VI) can be eluted with 0.20M hydrobromic acid in 50% aqueous acetone before the elution of indium, and Ir(III), Ir(IV), As(III), As(V), Se(IV), Tl(III), Hg(II), Ge(IV), Sb(III) and Sb(V), though not investigated in detail, should accompany these elements. Relevant distribution coefficients and elution curves and results for analyses of synthetic mixtures of indium with other elements are presented.     

Iodometric determination of peroxydiphosphate in the presence of copper(II) or iron(II) as catalyst

Peroxydiphosphate can be determined iodometrically in the presence of a large excess of potassium iodide with copper(II) or iron(II) as catalyst through the operation of the Cu(II)/Cu(I) or Fe(II)/Fe(III) cycle. The method is applicable in HClO(4), H(2)SO(4), HCl and CH(3)COOH acid media in the range 0.1-1.0M studied. Nickel, manganese(II), cobalt(II), silver, chloride and phosphate are without effect.     

Distribution coefficients and ion-exchange selectivities for 46 elements with a macroporous cation-exchange resin in hydrochloric acid-acetone medium

Distribution coefficients with the macroporous cation-exchange resin AG MP-50 in HCl-acetone mixtures ranging from 0.2 to 4.0M HCl and from 0 to 95% acetone have been determined for 46 elements. The ion-exchange behaviour of the elements is discussed, some possible separations are indicated, and elution curves demonstrating separations of the combinations Au(III)BiZnPbSr; Rh(III)InGaCuNi and CdFe(III)LiAlYb are presented.     

Analytical procedures for the simultaneous voltammetric determination of heavy metals in meals

An analytical procedure regarding the determination of copper(II), lead(II), cadmium(II), zinc(II) and antimony(III) in matrices involved in foods and food chain as wholemeal, wheat and maize meal is proposed. The digestion of each matrix was carried out using concentrated HCl suprapure at 130 °C for 3 h. Differential pulse anodic stripping voltammetry (DPASV) was employed for simultaneously determining all the elements, using a conventional three-electrode cell and 0.5 M HCl as supporting electrolyte. The analytical procedure has been verified on the reference standard materials Wholemeal BCR-CRM 189, Wheat Flour NIST-SRM 1567a and Rice Flour NIST-SRM 1568a. For all the elements in the certified matrix, the precision as repeatability, expressed as relative standard deviation (s_r), and the accuracy, expressed as relative error (e), were of the order of 3 to 6%. The limits of detection were in the range 0.009–0.096 μg/g.     

The separation of W(V) from HCl-KSCN medium on polyurethane foam sorbents for its spectrophotometric determination in steels and silicates

A simple procedure for selective sorption of tungsten is described. The method involves reduction of W(VI) to W(V) with tin(II) chloride (2%, w/v) at 8-9M hydrochloric acid, formation of the W(V)-SCN complex with 0.2M KSCN and its sorption on polyurethane foam within 20 min. The sorbed complex is then eluted with acidified acetone (1 ml of 1M hydrochloric acid and 8 ml of acetone) followed by addition of 1 ml of 0.1M KSCN to the eluent. The method has been applied to the spectrophotometric determination of tungsten in steels and silicates by measuring the absorbance of the eluted solution at 400 nm. Beer's law is obeyed for the range 0.1-12 mug W/ml. Other elements, e.g., Co(III) (50 mug/ml), Cu(II) (10 mug/ml), Ti(IV) (20 mug/ml), V(V) (10 mug/ml) and Mo(VI) (0.5 mug/ml) have no effect on the method. Interference of copper, up to 100 mug/ml has been eliminated by masking with thiourea and that due to molybdenum by prior separation with thioglycollic acid on PUF. The method has been verified with standard samples.     

Separation of trace amounts of indium, gallium and aluminium from each other by cation-exchange chromatography on AG50-X4 resin

Traces and minor amounts of indium, gallium and aluminium can be separated from gram amounts of thallium and from each other by cation-exchange chromatography on a column containing as little as 2 g of AG50W-X4, a cation-exchange resin with low cross-linking. An elution sequence of 0.1 M HBr in 40% acetone [for Tl(III)], 0.2M HBr in 80% acetone for In, 0.3M HCl in 90% acetone for Ga and 3M aqueous HCl for Al is used. The separations are very sharp and even 10-mug amounts of In, Ga and Al in synthetic mixtures are recovered quantitatively, with a standard deviation of 0.3 mug. The separation factors between neighbouring ions are extremely large (> 5000).     

Extraction of manganese(II) with dithizone and potassium thiocyanate on foam sorbents for spectrophotometric determination in silicates

A method for selective extraction of Mn(II) with dithizone and potassium thiocyanate has been described. The method involves formation of a Mn(II)-thiocyanate-dithizone complex in a hexamine medium containing potassium thiocyanate (2.8M), dithizone (5.5-6.5 x 10(-5)M) and hydroxylamine hydrochloride (0.25%) at pH approximately 6 followed by extraction of the complex on polyurethane foam using batch squeezing mode within 1 hr. The sorbed Mn-thiocyanate-dithizone complex is eluted with acetone and made alkaline with 0.5 ml of a stabilizer solution (19 ml 2M NH(3) solution + 1 ml 5% hydroxylamine hydrochloride). The absorbance of the solution is measured at 506 nm. The adverse effect due to Pb may be obviated by separating the Pb as the sulphate during decomposition of sample and that due to iron may be removed before extraction of Mn by any suitable method. The other interfering elements (Cd, Zn, Ni, Co, Cu, etc.) are masked with KCN (6 x 10(-3)M optimum) solution. The method obeys Beer's Law from 0.1 to 2.0 mug Mn/ml. The method has been applied to various silicates, carbonates and glasses.     

Features of the Sorptive Extraction of Osmium in Different Oxidation States with Silica Gels Chemically Modified with Mercapto and Disulfide Groups

The sorptive extraction of osmium(VIII, VI, IV) from HCl solutions with silica gels chemically modified with mercapto groups (MPS) and disulfide groups (DPDSS) was studied. The recovery of osmium(VIII) from 0.5–4 M HCl is 99 and 25% with the sorption equilibration time 5 and 20 min for MPS and DPDSS, respectively. The equilibration time for the extraction of Os(VI) with MPS is no longer than 1 min. The recovery from 0.1–4 M HCl is up to 99.9%. The recovery of osmium(VI) with DPDSS decreases from 96 and 80% when going from 0.5 M to 4 M HCl. The quantitative extraction of osmium(IV) is attained at 95°C in the presence of tin(II) chloride and the equilibration time 60 min. Without tin(II) chloride, osmium(IV) is not extracted with these sorbents. The difference in the sorption ability of chemically modified silica gels with respect to osmium in different oxidation states can be used for the extraction of osmium(VI) and osmium(IV) and their separate determination directly in the MPS phase with the use of diffuse reflectance spectrometry.     

Distribution coefficients and cation-exchange behaviour of 45 elements with a macroporous resin in hydrochloric acid/methanol mixtures

Cation-exchange distribution coefficients are presented for 45 elements with the macroreticular (macroporous) cation-exchange resin AG MP-50 in mixed hydrochloric acid/methanol media, with acid concentrations ranging from 0.5 to 6.0 M, and methanol concentrations from 0 to 90%. The ion-exchange behaviour of the elements is discussed, some possible separations are indicated, and 3 multi-element elution curves are presented, demonstrating the separations of the combinations In-Zn-Ga-Al-Yb; Cd-Li-Cu(II)-Mg-Ca; and Pt(IV)-Te(IV)-V(IV)-Fe(III)-Mn(II).     

Highly accurate determination of trace amounts of uranium in standard reference materials by spectrophotometry with chlorophosphonazo III after complete separation by anion and cation exchange chromatography

Summary A method is described for the highly accurate determination of trace amounts of uranium in standard reference materials. The uranium is separated from the bulk elements by anion-exchange chromatography, eluting most elements with 6 M hydrochloric acid and iron(III) with 0.5 M hydrochloric acid in 90% acetone. After elution of uranium with 0.1 M hydrochloric acid, residual traces of other elements are separated by a very selective cation-exchange procedure using a 3 g resin column. Finally the uranium is determined in the hexavalent state by spectrophotometry at 672 nm of its complex with chlorophosphonazo III at pH 1.1±0.2 in the presence of DTPA. Results are very accurate and precise even on a semi-routine basis. Relevant elution curves and results are presented for recovery tests and for the analysis of the 10 South African UREM standard materials.

---

Methode hoher Genauigkeit zur spektalphotometrischen Bestimmung von Uranspuren in Standard-Referenzmaterialien mit Chlorphosphonazo III nach Abtrennung durch Anionen- und Kationen-Austausch-Chromatographie

Zusammenfassung Das Uran wird von den Hauptelementen durch Anionenaustausch abgetrennt, wobei die meisten Elemente mit GM HCl und Eisen(III) mit 0,5 M HCl in 90 %igem Aceton eluiert werden. Nach der Elution von Uran mit 0,1 M HCl werden die restlichen Spuren anderer Elemente durch ein selektives Kationenaustauschverfahren (3 g Harz) abgetrennt. Das Uran wird schließlich in der sechswertigen Form als Chlorphosphonazo-III-Komplex in Gegenwart von DTPA bei 672 nm (pH 1,1±0,2) spektralphotometrisch bestimmt. Selbst bei halbroutinemäßiger Ausführung werden sehr genaue Resultate erhalten (Wiederfindung 99,7–100%). Analysenergebnisse für 10 Südafrikanische Standardmaterialien werden angegeben.

Dedicated to Prof. Dr. E. Blasius on occasion of his 60th birthday     

Direct extraction of nickel from model sulfate solution with hydrazide of versatic <Emphasis Type="Italic">tert</Emphasis>-Carboxylic acids

Possibility of direct extraction of 0.66 g L–1 Ni(II), 0.048 g L^–1 Co(II), and 0.024 g L^–1 Zn(II) in the presence of the nine commonly accompanying elements from a model solution for underground sulfuric acid leaching of an oxidized Ni ore with a 0.4–0.6 M solution of a hydrazide of Versatic C₁₅–C₁₉ acids in kerosene was considered. The optimal conditions of extraction, extract washing to remove impurities, and re-extraction of Ni and Co were determined. It was found that the direct extraction of up to 90% of nickel, cobalt, and zinc is possible with an at least fivefold concentration in the extraction stage. The separation of Ni from Co and co-extracted Fe, Zn, and Mn is possible in the re-extraction stage by washing of the organic phase with a 0.5 M HCl solution.     

The determination of U,Np and Pu in urine by sequential extraction with ALAMINE-336 from hydrochloric acid medium

A method has been developed for the extraction of uranium, neptunium and plutonium from human urine using the comparatively cheap technical amine ALAMINE-336. These elements are coprecipitated with a calcium phosphate carrier, which is then subjected to a wet-ashing procedure with NHO₃/H₂O₂ and HCl/H₂O₂. The residue is dissolved in 10M hydrochloric acid and U, Np and Pu are extracted with a 10% ALAMINE-336/xylene solution, followed by subsequent back-extraction with 10M HCl/NH₄I (Pu), 4M HCl/HF (Np) and 0.1M HCl (U), respectively. The average recoveries are around 95%.     

Palladium(II) Extraction by Pyridinecarboxylic Acid Esters

The commercial extractant Acorga CLX-50 and model individual di-2-ethylhexyl pyridine-3,5-dicarboxylate and 2-ethylhexyl pyridine-3-carboxylate in toluene were used for palladium(II) extraction from aqueous HCl solutions. The studies of extraction rate and equilibrium were carried out in systems containing palladium(II) ions in 3.0, 0.1, and 0.1M HCl in the presence of 0.5M sodium chloride and in 0.1M HCl in the presence of 0.1–6.0M lithium chloride and in 0.1M HCl in the presence 0.1–3.5M sodium nitrate. The examined extractants can efficiently extract palladium(II) from aqueous hydrochloric acid and nitrate solutions. The extraction is slow and equilibrium is obtained after 2 hours. The best extraction of palladium(II) is observed from 0.1M HCl solution in the presence of 3.5M sodium nitrate. A spontaneous transfer of palladium(II) to the toluene phase without any phase mixing is also observed.     

Sorption-spectroscopy and test determination of uranium(VI) and iron(III) from a single sample on the solid phase of fiber materials filled with an AB-17 ion exchanger

Diffuse reflectance spectroscopy has been used for the study of the sorption of malonate and glycolate complexes of uranium(VI) and iron(III), present simultaneously in solution, onto the solid phase of fiber materials filled with an AB-17 anion exchanger. In the form of malonate complexes uranium(VI) is determined in 0.5 M HCl on substrate discs with immobilized Arsenazo III, while iron(III) is determined on substrate discs with potassium thiocyanate in 0.5 M HCl. The dependence of the analytical signals on the concentrations of U(VI) and Fe(III) is linear in the ranges 0.02–0.16 μg/mL; the detection limit is 0.01 μg/mL. The possibility of analysis of U(VI) and Fe(III) mixtures in ratio from 1: 5 to 5: 1 in the presence of 2-fold concentrations of Zr(IV), Th(IV), and Ti(IV), 5-fold concentrations of Bi(III), 10-fold concentrations of Cu(II), 20-fold concentrations of La(III), 100-fold concentrations of Ni(II) and Zn(II), and 200-fold concentrations of Co(II) and Ca(II) has been demonstrated. Standard color scales in the concentration range from 0.02 to 0.2 μg/mL have been used for the visual determination of uranium(VI) and iron(III).