Separation of traces and larger amounts of bismuth from gram amounts of thallium, mercury, gold and platinum by cation-exchange chromatography on a macroporous resin

Traces and larger amounts of bismuth (up to 50 mg) can be separated from gram amounts of thallium, mercury, gold and platinum (up to 5 g) by sorption from a mixture of 0.1M hydrochloric acid and 0.4M nitric acid on a column containing just 3 g (8.1 ml) of AGMP-50, a macroporous cation-exchange resin. This resin retains bismuth much more strongly than does the usual microporous resin (styrene-DVB with 8% cross-linkage). Other elements are eluted with the same acid mixture as that used for sorption, and bismuth is finally eluted with 1.0M hydrochloric acid. Separations of bismuth are sharp and recoveries quantitative. Only microgram amounts of the other elements remain in the bismuth fraction. Amounts of bismuth as little as 5 mug have been separated from 5 g of thallium, and determined (r.s.d. = 2%) by flame atomic-absorption. Only 100-mug amounts of bismuth have been separated from gram amounts of mercury, gold, and platinum, but there is no reason to believe that smaller or larger amounts of bismuth cannot be separated from these elements and recovered with the same accuracy as that for the separation from thallium. The lower limit of the method is determination of 0.4 mug of bismuth in 10 ml of solution (0.004 absorbance). An elution curve, the relevant distribution coefficients and the results of analysis of synthetic mixtures and two practical samples [thallium metal and mercury(II) nitrate] are presented.     

Determination of silver, antimony, bismuth, copper, cadmium and indium in ores, concentrates and related materials by atomic-absorption spectrophotometry after methyl isobutyl ketone extraction as iodides

Methods for determining ~ 0.2 mug g or more of silver and cadmium, ~ 0.5 mug g or more of copper and ~ 5 mug g or more of antimony, bismuth and indium in ores, concentrates and related materials are described. After sample decomposition and recovery of antimony and bismuth retained by lead and calcium sulphates, by co-precipitation with hydrous ferric oxide at pH 6.20 +/- 0.05, iron(III) is reduced to iron(II) with ascorbic acid, and antimony, bismuth, copper, cadmium and indium are separated from the remaining matrix elements by a single methyl isobutyl ketone extraction of their iodides from ~2M sulphuric acid-0.1M potassium iodide. The extract is washed with a sulphuric acid-potassium iodide solution of the same composition to remove residual iron and co-extracted zinc, and the extracted elements are stripped from the extract with 20% v v nitric acid-20% v v hydrogen peroxide. Alternatively, after the removal of lead sulphate by filtration, silver, copper, cadmium and indium can be extracted under the same conditions and stripped with 40% v v nitric acid-25% v v hydrochloric acid. The strip solutions are treated with sulphuric and perchloric acids and ultimately evaporated to dry ness. The individual elements are determined in a 24% v v hydrochloric acid medium containing 1000 mug of potassium per ml by atomic-absorption spectrophotometry with an air-acetylene flame. Tin, arsenic and molybdenum are not co-extracted under the conditions above. Results obtained for silver, antimony, bismuth and indium in some Canadian certified reference materials by these methods are compared with those obtained earlier by previously published methods.     

Separation of silver from zinc, cadmium, copper, nickel and other elements in nitric acid with a macroporous resin

Traces of silver and amounts up to 50 mg can be separated from up to gram amounts of Zn, Cu(II), Ni, Co(II), Mg, Be, Ti(IV), V(IV), Li and Na by eluting these with 2.0M nitric acid from a column containing 54 ml (20 g) of macroporous AG MP-50 cation-exchange resin of 100-200 mesh particle size, in the H(+)-form. Silver is retained and can be eluted with 0.5M hydrobromic acid in 9:1 v v acetone-water. Separations are sharp and quantitative and only a few microg of the other elements are found in the silver fraction. Cadmium and manganese (II) can also be separated quantitatively but show tailing and require larger elution volumes. Some typical elution curves and results of analyses of synthetic mixtures 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.     

Determination of cobalt, nickel, lead, bismuth and indium in ores, soils and related materials by atomic-absorption spectrometry after separation by xanthate extraction

A method for determining approximately 0.5, mug/g or more of cobalt, nickel and lead and approximately 3 mug/g or more of bismuth and indium in ores, soils and related materials is described. After sample decomposition and dissolution of the salts in dilute hydrochloric-tartaric acid solution, iron(III) is reduced with ascorbic acid and the resultant iron(II) is complexed with ammonium fluoride. Cobalt, nickel, lead, bismuth and indium are subsequently separated from iron, aluminium, zinc and other matrix elements by a triple chloroform extraction of their xanthate complexes at pH 2.00 +/- 0.05. After the removal of chloroform by evaporation and the destruction of the xanthates with nitric and perchloric acids, the solution is evaporated to dryness and the individual elements are ultimately determined in a 20% v/v hydrochloric acid medium containing 1000 mug/ml potassium by atomic-absorption spectrometry with an air-acetylene flame. Co-extraction of arsenic and antimony is avoided by volatilizing them as the bromides during the decomposition step. Small amounts of co-extracted molybdenum, iron and copper do not interfere.     

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).     

Comparison of silver results for canadian reference ores and concentrates and zinc-processing products by acid decomposition, tribenzylamine/chloroform extraction and fire-assay combined with atomic-absorption spectrophotometry

The results obtained for silver in Canadian reference ores and concentrates and in zinc-processing products by three atomic-absorption spectrophotometric methods are compared. "Wet chemical" methods based on the decomposition of the sample with mixed acids yield more accurate results than those based on fire-assay collection techniques. A direct acid-decomposition method involving the determination of silver in a 20% v/v hydrochloric acid-1% v/v diethylenetriamine medium is recommended for the determination of approximately 10 mug g or higher levels of silver. A method based on chloroform extraction of the tribenzylamine-silver bromide ion-association complex from 0.08M potassium bromide-2M sulphuric acid is recommended for samples containing < 10 mug of silver per 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 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.     

Solvent extraction of lead,silver, antimony and thallium with zinc dibenzyldithiocarbamate and its application to the separation of bismuth from large amounts of lead

Solvent extraction of lead, silver, antimony and thallium from various acid solutions was investigated with zinc-DBDTC as chelating reagent. These metals were quantitatively extracted over a wide range of acidity with 0.03% zinc-DBDTC solution in carbon tetrachloride. A separation procedure for bismuth from large amounts of lead was developed; bismuth was extracted from 1 M nitric acid with zinc-DBDTC and was separated from lead by subsequently washing the organic phase once with 3.5 M hydrochloric acid or twice with 3 M hydrochloric acid. Satisfactory results were obtained in separating microgram amounts of bismuth from 1 g of lead.     

Determination of antimony in concentrates, ores and non-ferrous materials by atomic-absorption spectrophotometry after iron-lanthanum collection, or by the iodide method after further xanthate extraction

Methods for determining trace and moderate amounts of antimony in copper, nickel, molybdenum, lead and zinc concentrates and in ores are described. Following sample decomposition, antimony is oxidized to antimony(V) with aqua regia, then reduced to antimony(III) with sodium metabisulphite in 6M hydrochloric acid medium and separated from most of the matrix elements by co-precipitation with hydrous ferric and lanthanum oxides. Antimony (>/= 100 mug/g) can subsequently be determined by atomic-absorption spectrophotometry, at 217.6 nm after dissolution of the precipitate in 3M hydrochloric acid. Alternatively, for the determination of antimony at levels of 1 mug/g or more, the precipitate is dissolved in 5M hydrochloric acid containing stannous chloride as a reluctant for iron(III) and thiourea as a complexing agent for copper. Then tin is complexed with hydrofluoric acid, and antimony is separated from iron, tin, lead and other co-precipitated elements, including lanthanum, by chloroform extraction of its xanthate. It is then determined spectrophotometrically, at 331 or 425 nm as the iodide. Interference from co-extracted bismuth is eliminated by washing the extract with hydrochloric acid of the same acid concentration as the medium used for extraction. Interference from co-extracted molybdenum, which causes high results at 331 nm, is avoided by measuring the absorbance at 425 nm. The proposed methods are also applicable to high-purity copper metal and copper- and lead-base alloys. In the spectrophotometric iodide method, the importance of the preliminary oxidation of all of the antimony to antimony(V), to avoid the formation of an unreactive species, is shown.     

Spectrophotometric determination of bismuth in concentrates and non-ferrous alloys by the iodide method after separations by diethyldithiocarbamate and xanthate extraction

A method for determining 0.0001-1% of bismuth in copper, molybdenum, lead, zinc and nickel sulphide concentrates is described. After sample decomposition, bismuth is separated from matrix and other elements, except lead and thallium(III), by chloroform extraction of its diethyldithiocarbamate complex, pH 11.5-12.0, from a sodium hydroxide medium containing citric acid, tartaric acid, EDTA and potassium cyanide as complexing agents. Following back-extraction of bismuth into 12M hydrochloric acid and reduction of thallium to the univalent state, bismuth is separated from co-extracted lead and thallium by chloroform extraction of its xanthate from a 2.5M hydrochloric acid-tartaric acid-ammonium chloride medium. Bismuth is then determined spectrophotometrically, at 337 or 460 nm, as the iodide. Interference from lead, which is co-extracted in mug-amounts as the xanthate and causes high results at 337 nm, is eliminated by washing the extract with a hydrochloric acid solution of the same composition as the medium used for extraction. The proposed method is also applicable to lead-, tin- and copper-base alloys.     

Separation of lead-203 from cyclotron-bombarded thallium targets by ion-exchange chromatography

A simple method is presented for the separation of lead-203 from copper-backed thallium cyclotron targets. The procedure involves cation-exchange chromatography in hydrochloric acid and hydrochloric acid-acetone mixtures. Further purification involves anion-exchange chromatography in nitric acid-hydrobromic acid mixtures. A cation-exchange column containing 3.0 g of resin can handle as much as 15 g of thallium and 160 mg of copper. An anion-exchange column containing 3.0 g of resin can separate lead from up to 200 mg of thallium and 10 mg of copper. Separations are extremely sharp and less than 0.1 mug of thallium and less than 0.1 mug of copper remain in the lead-203 fraction.     

Determination of silver in ores, concentrates, zinc process solutions, copper metal and copper-base alloys by atomic-absorption spectrophotometry after separation by extraction of the tribenzylamine-silver bromide complex

A method for determining 0.1 μg/g or more of silver in ores and concentrates and 0.001 μg/ml or more of silver in zinc process solutions is described. Silver is separated from the matrix elements by chloroform extraction of the tribenzylamine—silver bromide ion-association complex from 0.08M potassium bromide—2M sulphuric acid and stripped with 9M hydrobromic acid. This solution is evaporated to dryness and organic material is destroyed with nitric and perchloric acids. Silver is determined by atomic-absorption spectrophotometry in an air—acetylene flame, at 328.1 nm, in a 10% v/v hydrochloric acid—1% v/v diethylenetriamine medium. Cadmium, bismuth and molybdenum are partly co-extracted but do not interfere. The method is also applicable to copper metal and copper-base alloys. Results obtained by this method are compared with those obtained by a fire-assay/atomic-absorption method.     

Spectrofluorimetric analysis of cefoxitin in pharmaceutical dosage

A fluorescence method involving sample pre-treatment is investigated concerning the determination of cefoxitin. A fluorescent product is formed when samples containing cefoxitin are subjected to alkaline hydrolysis with 1.0M sodium hydroxide and heated for 60 min at 90 degrees . The fluorescence is measured in ethanol/water medium (50% v/v) at approximately pH 2.0 provided by adding of 0.1M hydrochloric acid. The fluorescence excitation and emission maxima were 317 and 400 nm, respectively. The quantitative range is between 0.020 and 1.40 mug/ml. A detection limit of 2 x 10(-3) mug/ml was found. The proposed method has been applied to the determination of cefoxitin in commercial injections, saline and glucosed physiological serum.     

Spectrophotometric determination of bismuth and EDTA by means of the reaction of bismuth with pyrocatechol violet in the presence of septonex

The reaction of bismuth(III) with Pyrocatechol Violet in the presence of the cationic surfactant Septonex was studied and the optimal conditions for its analytical use were found (lambda = 612 nm, pH = 3.1, C(PV) = 4 x 10(-5)M, C(Sept), = 5 x 10(-4)M). The Lambert-Beer law is obeyed over the bismuth range 0.1-7.5 mug/ml. Decomposition of the Bi-PV-Septonex complex was utilized for indirect determination of ethylenediaminetetra-acetic acid at concentrations of 0.3-7.4 mug/ml.     

Charged particle activation analysis applied to the detection of heavy elements

Trace analysis methods have been developed for determining thallium, lead and bismuth. Proton or deuteron activation is used followed by a radiochemical separation of the reaction products:²⁰³Pb from thallium,²⁰⁶Bi from lead, and²⁰⁷Po from bismuth. Activation curves are presented for different nuclear reactions occuring on the elements studied. Determinations have been carried out on high purity samples containing varying amounts of thallium, lead, and bismuth. Based on experimental data, the detection limits are estimated at 0.01 ppm for lead, and 0.001 ppm for thallium and bismuth, respectively.     

Determination of tellurium in ores, concentrates and related materials by graphite-furnace atomic-absorption spectrometry after separations by iron collection and xanthate extraction

A method for determining approximately 0.01 mug/g or more of tellurium in ores, concentrates, rocks, soils and sediments is described. After sample decomposition and evaporation of the solution to incipient dryness, tellurium is separated from > 300 mug of copper by co-precipitation with hydrous ferric oxide from an ammoniacal medium and the precipitate is dissolved in 10M hydrochloric acid. Alternatively, for samples containing 300 mug of copper, the salts are dissolved in 10M hydrochloric acid. Tellurium in the resultant solutions is reduced to the quadrivalent state by heating and separated from iron, lead and various other elements by a single cyclohexane extraction of its xanthate complex from approximately 9.5M hydrochloric acid in the presence of thiosemicarbazide as a complexing agent for copper. After washing with 10M hydrochloric acid followed by water to remove residual iron, chloride and soluble salts, tellurium is stripped from the extract with 16M nitric acid and finally determined, in a 2% v/v nitric acid medium, by graphite-furnace atomic-absorption spectrometry at 214.3 nm in the presence of nickel as matrix modifier. Small amounts of gold and palladium, which are partly co-extracted as xanthates if the iron-collection step is omitted, do not interfere. Co-extraction of arsenic is avoided by volatilizing it as the bromide during the decomposition step. The method is directly applicable, without the co-precipitation step, to most rocks, soils and sediments.     

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.     

Determination of arsenic in ores, concentrates and related materials by graphite-furnace atomic-absorption spectrometry after separation by xanthate extraction

A method for determining approximately 0.2 mug/g or more of arsenic in ores, concentrates and related materials is described. After sample decomposition arsenic(V) is reduced to arsenic(III) with titanium(III) and separated from iron, lead, zinc, copper, uranium, tin, antimony, bismuth and other elements by cyclohexane extraction of its xanthate complex from approximately 8-10M hydrochloric acid. After washing with 10M hydrochloric acid-2% thiourea solution to remove residual iron and co-extracted copper, followed by water to remove chloride, arsenic is stripped from the extract with 16M nitric acid and ultimately determined in a 2% nitric acid medium by graphite-furnace atomic-absorption spectrometry, at 193.7 nm, in the presence of thiourea (which eliminates interference from sulphate) and palladium as matrix modifiers. Small amounts of gold, platinum and palladium, which are partly co-extracted as xanthates under the proposed conditions, do not interfere.