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.     

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.     

Quantitative paper chromatography : The separation and gravimetric determination of copper

Up to 50 mg of copper can be separated from similar quantities of silver, gold, platinum, rhodium, mercury and bismuth by a chromatographic method which employs butanol saturated with both 2 N NH₄OH and dimethylglyoxime as solvent. The copper may be quantitatively determined by electro-deposition from nitric acid solutions of the filtrates obtained. Strips of paper-pulp, approximately 250 mm long, 25 mm wide and 6 mm thick, and capable of absorbing 2 ml of solution on a spot 25 mm in diameter, are utilised.     

Application of radioisotopes in column chromatography on substituted celluloses-VI The separation of antimony from manganese, iron and other metals

The Chromatographic behaviour of nanogram amounts of antimony in ethyl ether medium was studied by radioisotope techniques on cellobiose, cellulose and seven substituted celluloses. It was found that antimony is strongly retained and can be separated from macro amounts of manganese, iron, gold, uranium, mercury, arsenic and several other metals. Antimony could be quantitatively recovered by elution from natural cellulose and cellobiose. The method can be applied in several analytical problems concerning the separation of traces of antimony.     

Preparation and properties of macroreticular resins containing thiazole and thiazoline groups

Three macroreticular polystyrene-based resins with amino- or imino-thiazole and thiazoline groups as the functional groups have been prepared. The resins are highly stable in acid and alkaline solutions and have high selectivity for mercury(II). In the presence of hydrochloric acid, sorption of mercury attains equilibrium fairly rapidly, the time for 50% uptake of mercury being 3-6 min. There are practically no interferences. In a column operation, mercury is quantitatively recovered by elution with 0.1M hydrochloric acid containing 5% thiourea. The thiazoline resin column can be used to concentrate mercury from sea-water.     

Cation-exchange separations in organic solvent-dithizone media

Numerous elements can be adsorbed on a column of the strongly acidic cation-exchange resin Dowex 50 from a mixture consisting of tetrahydrofuran and 1 M nitric acid (19:1). These elements include Ag, Cu, Bi, Pb, rare earths, alkaline earth metals, alkali metals, U, Th, Fe, Co, Zn and Cd; Hg and Sb are not retained and so can be separated from the adsorbed elements. Fractionation of the adsorbed elements can be effected by using as eluent 0.01 M dithizone in tetrahydrofuran-1 M nitric acid(19:1);; the dithizonates of silver, copper and bismuth are selectively eluted while the other adsorbed metal ions are still retained. The technique is suitable for the separation of tracer and macro amounts of elements.     

Reversed-phase foam chromatography : Chemical enrichment and separation of gold in the tributylphosphate-thiourea-perchloric acid system

Gold(III) is quantitatively extracted from acidic solution of thiourea into tri-n-butyl phosphate (TBP). The extracted species contains one molecule of thiourea and four molecules of TBP for each atom of gold. On short columns of TBP-loaded polyurethane foam, gold(III) can be separated from many other elements by retention from 0.1 M perchloric acid solution containing 3% thiourea and 1% sodium perchlorate. Flow-rates of 50–60 ml min^?1 are possible. Trace amounts of gold can be separated quantitatively from high concentrations of Zn²⁺, Co²⁺, Ni²⁺, Fe³⁺, Sb³⁺, Cu²⁺, Bi³⁺ and Pd²⁺, which have a negligible effect on the rate of adsorption of the gold-thiourea complex. The chemical enrichment of gold from dilute aqueous solutions is also possible.     

Collection of mercury from artificial sea-water with activated carbon

Nanogram amounts of mercury(II) and methylmercury in artificial sea-water containing mineral acids as preserving reagents were shown to be collected quantitatively with activated carbon. Mercury concentrated on activated carbon was determined directly by combustion, trapping on gold and electrothermal atomic-absorption spectrophotometry. The activated carbon was purified by heating at 350 degrees for 2 hr. Sulphuric acid and hydrochloric acid were purified by treatment with activated carbon. Interference from iodide was eliminated by using a carbonate buffer wash before the atomic-absorption measurement. Less than 4 ng of mercury in 200-300 ml of artificial sea-water, whether acidified or not (with sulphuric, hydrochloric or nitric acid), was satisfactorily collected with 100 mg of activated carbon. Mercury was also collected quantitatively after oxidative treatment of artificial sea-water.     

The quantitative separation of calcium from magnesium,aluminium and other elements by cation-exchange chromatography in ethanol-hydrochloric acid

Magnesium can be separated from calcium by elution with 3.0 M hydrochloric acid containing 60% ethanol from a column of AG₅₀W-X8 cation-exchange resin. Calcium is retained and can be eluted with 3.0 M hydrochloric acid or 2.0 M nitric acid. The separation factor of (α_Mg^ca=5.6 is considerably higher than that in aqueous hydrochloric acid and comparable to those obtained with organic complexing reagents. Separations are sharp and quantitative; up to 10 mmol of magnesium can be separated from 0.01 mmol of calcium and vice versa on a 60-ml column. Al, Fe(III), Mn, Ni(II), Co(II), Zn, Cd, Cu(II), Pb(II), U(VI), Be, Ga, Ti(IV) in the presence of H₂O₂ and many other elements accompany magnesium and can be separated from calcium quantitatively. Sr, Ba, Zr, Hf, Th, Sc, La and the rare earths are retained together with Ca, but can be separated by other 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.     

Differential-pulse anodic-stripping voltammetric determination of traces of lead in high-purity copper after its separation by ion exchange

Trace amounts of lead in copper can be determined by differential-pulse anodic-stripping voltammetry after separating it from the matrix. Lead was quantitatively retained on a small Dowex 1-X4 ion-exchange column, without retaining copper when present as a copper-amine complex in solutions containing 0.2 M sodium hydroxide. Subsequent desorption was done with 2 M nitric acid. After deposition for 1 min on a hanging mercury drop electrode and subsequent stripping, the limit of detection was 2 ng ml^?1 and the limit of quantification was 6.6 ng ml^?1. Recoveries of lead were checked by standard addition to copper solution.     

Histidine as the functional group for a chelating ion exchanger

In the chelating ion exchanger synthesized, the amino group of histidine is attached chemically via the azide method to the carboxyl group of Amberlite IRC-50. A flow system based on a spectrophotometric detector, with 4-(2-pyridylazo) resorcinol as reagent, is described for fast assays of eluted cations. The pH dependence of the metal extraction is reported for Ag(I), Au(III), Cu(II), Fe(III), Hg(II), Ni(II) and Zn(II) ions. The resin exhibits no affinity for the alkali or alkaline earth metals. The uptake of traces of the specified elements from synthetic samples by a short (90 mm) column of the histidine-containing resin was in the range 94–100% and the retained metals were readily eluted by means of 2 M hydrochloric or hydrobromic acid. In column operation, mercury was quantitatively recovered even in the presence of large excesses of various ligands. The recoveries of the trace metals were good at the usual pH of natural waters.     

Preconcentration of silver(I), gold(III) and palladium(II) in sea water with p-dimethylaminobenzylidenerhodanine supported on silica gel

A water-insoluble chelating material, p-dimethylaminobenzylidenerhodanine on silica gel (DMABR—SG) is described for preconcentration of trace amounts of silver(I), gold(III) and palladium(II) from water samples. Radioactive tracers (^110mAg and ¹⁹⁵Au) were used to study the behavior of silver and gold; palladium was monitored spectrophotometrically as its 1-(2-pyridylazo)naphthol complex in chloroform. In batch experiments, silver was quantitatively retained on the DMABR—SG at acidities ranging from 1.7 M to pH 5, and gold from 3 M to pH 5; equilibrium was achieved within 1 min for both elements. From sea water, silver ion was completely retained at pH 1.0–6.5 and gold ion at pH 1.0–3.5. In the case of palladium, shaking for about 20 min was required for quantitative retention at pH 1.0–5.0 for aqueous solution and at pH 1.0–7.0 for sea water. The chelating capacity of the DMABR—SG was 23 μmol Ag, 11 μmol Au and 11 μmol Pd per g. Quantitative recovery of silver and gold on DMABR—SG columns from sea water was achieved at higher flow rates (1–2 l h^-1 and 2–3 l h^-1, respectively) than with other chelating resins, e.g., Chelex 100, palladium required slower flow rate (150 ml h^-1). Silver retained on the DMABR—SG column was completely eluted with 20 ml of 2.5% sodium thiosulfate solution but palladium remained on the column. Silver, gold and palladium were quantitatively eluted with 20 ml of 0.1% thiourea in 0.1 M hydrochloric acid.     

Solid-phase extraction and determination of ultra trace amounts of lead,mercury and cadmium in water samples using octadecyl silica membrane disks modified with 5,5′-dithiobis(2-nitrobenzoic acid) and atomic absorption spectrometry

A simple and fast method for preconcentration and determination of ultra trace amounts of lead(II), mercury(II) and cadmium(II) in water samples is presented. Lead, mercury and cadmium adsorbed quantitatively during passage of water samples (pH?=?7, flow rate?=?20 mL min^?1) through octadecyl silica membrane disks modified with 5,5′-dithiobis(2-nitrobenzoic acid). The retained lead, mercury and cadmium are then stripped from the disk with a minimal amount of 1 M hydrochloric acid solution as eluent, and determined by atomic absorption spectrometry. The influence of flow rates of the eluent and sample solution, the amount of ligand, type and least amount of eluent, pH of sample, effect of other ions and breakthrough volume are determined. The breakthrough volume of the method is greater than 2000 mL for lead and greater than 1500 mL for mercury and cadmium, which results in an enrichment factor of 200 for lead and an enrichment factor of 150 for both mercury and cadmium. The limit of detection of the proposed method is 177, 2 and 13 ng l^?1 for lead, mercury and cadmium, respectively.     

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.     

Separation of copper(II) from uranium(VI) and many other elements by cation-exchange chromatography in acetone-hydrobromic acid media: Improved selective separation of copper

Co(II), Ni(II), Mn(II), Li, Na, K, Rb, Cs, Be, Mg, Ca, Sr, Ba, Ti(IV), V(IV), Zr, Hf, Th, Al, Sc, Y, La, the lanthanides and also U(VI), which accompany copper(II) in hydrochloric acid-acetone mixtures, can be separated from copper by eluting copper(II) with 0.50 M hydrobromic acid in 85% acetone from a column of AG 50W-X8 resin, 200–400 mesh, while all these elements are retained by the column quantitatively. Separations are sharp and quantitative, as is demonstrated by results for some synthetic mixtures. Some relevant elution curves are presented.     

Separation of lithium from sodium,beryllium and other elements by cation-exchange chromatography in nitric acid-methanol

Lithium can be separated from sodium, beryllium and many other elements by eluting lithium with 1 M nitric acid in 80% methanol from a column of AG50W-X8 sulphonated polystyrene cation-exchange resin. The separation factor is not quite as large as that in 1 M hydrochloric acid in 80% methanol, but many elements, such as Zn, Cd, In, Pb(II), Bi(III) and Fe(III), which form chloride complexes in 1 M HCl-80% methanol are retained quantitatively together with Na, Be, Mg, Ca, Mn(II), Al, Ti(IV), U(VI), and many other elements, when 1 M HNO3-80% methanol is used for elution of lithium. A method for the accurate determination of traces of lithium in rock samples is described, and some results obtained are presented together with relevant distribution coefficients, elution curves and results for the analysis of synthetic mixtures.     

Ion-exchange resins containing s-bonded dithizone and dehydrodithizone as functional groups : Part 3. Determination of Gold,Platinum and Palladium in Geological Samples by means of a Dehydrodithizone Resin and Plasma Emission Spectrometry

A procedure is described for the determination of gold, platinum and palladium in sulphide ores, concentrates and mattes. The method is based on chromatographic separation and selective elution of precious metals on small resin beds (0.7 × 2.5 cm) of the sorbent P-TD. After roasting, the samples were digested with aqua regia, and the residues fused with sodium peroxide. The acid leaching solutions obtained from both procedures were separately passed through an ion-exchange column. The metals were quantitatively retained after one loading step and eluted by a sequence of 2 M perchloric acid and 5% (w/v) thiourea solution. Preconcentrated Au, Pt and Pd were finally quantified with a d.c. plasma emission spectrometer. The effect of roasting temperature on the recovery of precious metals as well as the efficiency of the aqua regia leaching from the different materials were investigated in detail. Repeated analyses of standard reference samples proved the proposed method to be reliable.     

Improved separation of cadmium from indium,zinc, gallium and other elements by anion-exchange chromatography in hydrobromic nitric acid mixtures

The separation of cadmium from indium, zinc and many other elements is considerably improved by eluting these elements with 0.1 M hydrobromic–0.5 M nitric acid solution from a column of AG1-X8 resin. Cadmium is retained very strongly and can be eluted with 2 M nitric acid or 1 M ammonia–0.2 M ammonium nitrate solution. Separations are sharp and quantitative and from microgram amounts up to 2 g of indium and zinc are separated from amounts of cadmium ranging from micrograms up to 100 mg on a 2-g (4.6 ml) resin column. Ga(II), Fe(III). Mn(II), Co(II), U(VI) and Ni(II) can be separated quantitatively from cadmium in the same way. The behaviour of numerous elements is discussed, with special attention to lead, and relevant elution curves and results from the analysis of synthetic mixtures are presented.     

Quantitative separation of lanthanides and scandium from barium,strontium and other elements by cation-exchange chromatography in nitric acid

The lanthanides plus yttrium and scandium are separated from Ba, Sr, Ca, Mg, Pb(II), Bi(III), Zn, Mn(II) and U(VI) by eluting these elements with 2.0 M nitric acid from a column of AG50W-X8 cation exchange resin (200-400 mesh). The lanthanides are retained and can then be eluted with 4 M nitric or hydrochloric acid. Separations are quantitative and applicable to microgram and millimolar amounts of the lanthanides and the other elements. Elements such as Cu(II), Co(II), Ni(II), Cd. Hg(II), T1(I). Ag, Be, Ti(IV) and the alkali metals should accompany barium quantitatively according to their known distribution coefficients. Relevant elution curves and results of analysis of synthetic mixtures are presented.