Determination of silver in copper and lead metals and alloys and in zinc and selenium by atomic-absorption spectrometry after separation by extraction of the tri-n-octylmethylammonium-silver bromide complex

A simple and sensitive combined solvent extraction and atomic-absorption spectrometric method has been developed for the determination of silver in copper and lead metals and alloys and in zinc and selenium. Optimal conditions have been established for the extraction and determination of silver. Silver is extracted as the tri-n-octylmethylammonium-silver bromide complex and determined by atomic-absorption spectrometry by spraying the extract directly into the flame. As little as 0.2 mug of silver in a sample can be determined.     

Differential determination of tellurium(IV) and tellurium(VI) with sodium diethyldithiocarbamate, ammonium pyrrolidinedithiocarbamate and dithizone by atomic-absorption spectrophotometry with a carbon-tube atomizer

The extraction behaviour of tellurium(IV) and tellurium(VI) with sodium diethyldithiocarbamate, ammonium pyrrolidinedithiocarbamate and dithizone in organic solvents has been investigated by means of flameless atomic-absorption spectrophotometry with a carbon-tube atomizer. The selective extraction of tellurium(IV) and differential determination of tellurium(IV) and tellurium(VI) have been developed. With sodium diethyldithiocarbamate and carbon tetrachloride, when the aqueous phase/organic solvent volume-ratio is 5 and the injection volume in the carbon tube is 20 microl, the sensitivity for tellurium is 0.3 ng/ml for 1% absorption. The relative standard deviations are ca. 2%. The proposed methods have been applied satisfactorily to determination of tellurium(IV) and tellurium(VI) in various types of water.     

Determination of gold in silver, copper, lead, selenium and anode slime by atomic-absorption spectrometry

A simple and sensitive combined solvent-extraction and atomic-absorption spectrometric method has been developed for the determination of gold in silver, copper, lead, selenium and anode slime. Samples are decomposed with hydrochloric and nitric acids, and gold is extracted as the trioctylmethylammonium-gold bromide complex and determined by atomic-absorption spectrometry by direct spraying of the extract into the flame. Optimal conditions for the extraction and determination of gold have been established. As little as 0.5 mug of gold in a sample can be determined. The extraction of gold from hydrochloric or hydrobromic acid solution with trioctylamine or trioctylmethylammonium chloride (or bromide) has also been investigated.     

Determination of gold, indium, tellurium and thallium in the same sample digest of geological materials by atomic-absorption spectroscopy and two-step solvent extraction

A rock, soil, or stream-sediment sample is decomposed with hydrofluoric acid, aqua regia, and hydrobromic acid-bromine solution. Gold, thallium, indium and tellurium are separated and concentrated from the sample digest by a two-step MIBK extraction at two concentrations of hydrobromic add. Gold and thallium are first extracted from 0.1M hydrobromic acid medium, then indium and tellurium are extracted from 3M hydrobromic acid in the presence of ascorbic acid to eliminate iron interference. The elements are then determined by flame atomic-absorption spectrophotometry. The two-step solvent extraction can also be used in conjunction with electrothermal atomic-absorption methods to lower the detection limits for all four metals in geological materials.     

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.     

Titrimetric determination of selenium in anodic slimes

The determination of selenium in the presence of tellurium and copper has been studied, to allow analysis of anodic slimes from electrolytic copper refining. Three methods have been developed for the determination of selenium in these slimes. They are based on the extraction of selenium with sodium sulphite, reduction of selenite with sodium sulphite, and separation of selenium and tellurium by adjustment of pH. Selenium (10(-3)-10(-2)M) is determined in the presence of tellurium, copper, iron, silver and lead. The methods are fast and simple, do not need expensive reagents, and give satisfactory results.     

Rapid determination of selenium and tellurium by atomic-absorption spectrophotometry

A rapid method has been developed for the determination of selenium and tellurium in geological and biological samples. It involves acid digestion of the sample with mineral acids, addition of arsenic as a carrier, reduction of arsenic to co-precipitate selenium and tellurium, dissolution of the precipitate in dilute nitric acid and subsequent determination of selenium and tellurium by conventional atomic-absorption spectrophotometry. Selenium and tellurium have been measured on a routine basis, down to 0.1 ppm.     

Application of APCD/DIBK extraction system in strongly acidic media: Determination of traces of copper and nickel in titanium metals by extraction-flame atomic-absorption spectrometry

Extraction of nickel in strongly acidic solution (0.01 approximately 8M hydrochloric acid) with ammonium 1-pyrrolidinecarbodithioate (APCD) into di-isobutyl ketone (DIBK) has been studied, and the APCD/DIBK system has been applied to simultaneous extraction and flame atomic-absorption spectrometric determination of trace amounts of copper and nickel in titanium metal. Nickel could be extracted with copper from strongly acidic solution such as up to 5M hydrochloric acid with APCD/DIBK system. The extraction from such a strongly acidic media made it possible to extract nickel with copper, since it did not require the addition of a large amount of the masking agent which prevents the hydrolysis of the matrix titanium and also prevents the extraction of nickel. Thus, they could be extracted directly from the titanium metal sample digested by concentrated hydrochloric acid with a small amount of tetrafluorohydroboric acid. Effect of coexistence of a large amount (at least 0.2 g) of iron on the extraction of both elements could be prevented by keeping most of the matrix titanium as Ti(III). With the method described here, mug/g levels of copper and nickel in titanium metal could be rapidly determined with good precision and accuracy.     

Rapid determination of nanogram amounts of tellurium in silicate rocks

A hydride-generation flameless atomic-absorption technique is used to determine as little as 5 ng g^-1 tellurium in 0.25 g of silicate rock. After acid decomposition of the sample, tellurium hydride is generated with sodium borohydride and the vapor passed directly to a resistance-heated quartz cell mounted in an atomic-absorption spectrophotometer. Analyses of 11 U.S. Geological Survey standard rocks are presented.     

Determination of arsenic in ores, concentrates and related materials by continuous hydride-generation atomic-absorption spectrometry after separation by xanthate extraction

A recent graphite-furnace atomic-absorption method for determining approximately 0.2 mug/g or more of arsenic in ores, concentrates, rocks, soils and sediments, after separation from matrix elements by cyclohexane extraction of arsenic(III) xanthate from approximately 8-10M hydrochloric acid, has been modified to include an alternative hydride-generation atomic-absorption finish. After the extract has been washed with 10M hydrochloric acid-2% thiourea solution to remove co-extracted copper and residual iron, arsenic(III) in the extract is oxidized to arsenic(V) with bromine solution in carbon tetrachloride and stripped into water. Following the removal of bromine by evaporation of the solution, arsenic is reduced to arsenic(III) with potassium iodide in approximately 4M hydrochloric acid and ultimately determined to hydride-generation atomic-absorption spectrometry at 193.7 nm, with sodium borohydride as reductant. Interference from gold, platinum and palladium, which are partly co-extracted as xanthates under the proposed conditions, is eliminated by complexing them with thiosemicarbazide before the iodide reduction step. The detection limits for ores and related materials is approximately 0.1 mug of arsenic per g. Results obtained by this method are compared with those obtained previously by the graphite-furnace method.     

Influence of volatile hydride-forming elements on antimony determination by atomic-absorption spectrometry with hydride-generation

A study was undertaken to determine the interfering effects of arsenic, bismuth, germanium, lead, selenium, tin and tellurium on trace determination of antimony by atomic-absorption spectrometry with hydride-generation. A 1% NaBH(4) solution was used as reductant and a small amount of oxygen was added to the hydrogen produced, to support the combustion and atomization of SbH(3). The interference from selenium in the determination of antimony is removed if potassium iodide-ascorbic acid solution or copper sulphate is added to the sample solution. The interference of tin and tellurium can also be avoided by adding potassium iodide-ascorbic acid solution. A possible interference mechanism is discussed.     

Trace metal analysis of rocks by flameless atomic-absorption spectrometry with a metal micro-tube atomizer

Flameless atomic-absorption spectrometry with a metal micro-tube atomizer has been studied. The element to be determined was atomized by electrical heating of the micro-tube in an inert atmosphere within a glass chamber. A detailed study of the atomic-absorption characteristics of the micro-tube atomizer is presented. The absolute sensitivities were 2.6 x 10(-12), 2.9 x 10(-11), 2.5 x 10(-10), 1.1 x 10(-10) and 1.4 x 10(-10)g for copper, cobalt, aluminium, palladium and selenium, respectively. The interferences of cations were studied for determination of cobalt and copper. Cobalt and copper in rock samples were determined in order to evaluate the metal micro- tube atomizer.     

Extraction and separation studies of tellurium(IV) with tris-(2-ethyl hexyl) phosphate

A method is proposed for the extraction of microgram levels of tellurium(IV) from halide media with tris-(2-ethyl hexyl) phosphate dissolved in toluene as extractant. The optimum conditions have been evaluated from a critical study of acid concentration, extractant concentration, period of equilibration and effect of solvent. Tellurium ion from the organic phase is stripped with water and determined spectrophotometrically with stannous chloride. The method affords binary separation of tellurium from copper, bismuth, gold and selenium and is applicable to the analysis of alloy samples and synthetic mixtures. The method is fast, accurate and precise.     

Determination of antimony in ores and related materials by continuous hydride-generation atomic-absorption spectrometry after separation by xanthate extraction

A continuous hydride-generation atomic-absorption spectrometric method for determining approximately 0.02 mug/g or more of antimony in ores, concentrates, rocks, soils and sediments is described. The method involves the reduction of antimony(V) to antimony(III) by heating with hypophosphorous acid in a 4.5M hydrochloric acid-tartaric acid medium and its separation by filtration, if necessary, from any elemental arsenic, selenium and tellurium produced during the reduction step. Antimony is subsequently separated from iron, lead, zinc, tin and various other elements by a single cyclohexane extraction of its xanthate complex from approximately 4.5M hydrochloric acid/0.2M sulphuric acid in the presence of ascorbic acid as a reluctant for iron(III). After the extract is washed, if necessary, with 10% hydrochloric acid-2% thiourea solution to remove co-extracted copper, followed by 4.5M hydrochloric acid to remove residual iron and other elements, antimony(III) in the extract is oxidized to antimony(V) with bromine solution in carbon tetrachloride and stripped into dilute sulphuric acid containing tartaric acid. Following the removal of bromine by evaporation of the solution, antimony(V) is reduced to antimony(III) with potassium iodide in approximately 3M hydrochloric acid and finally determined by hydride-generation atomic-absorption spectrometry at 217.8 nm with sodium borohydride as reluctant. Interference from platinum and palladium, which are partly co-extracted as xanthates under the proposed conditions, is eliminated by complexing them with thiosemicarbazide during the iodide reduction step. Interference from gold is avoided by using a 3M hydrochloric acid medium for the hydride-generation step. Under these conditions gold forms a stable iodide complex.     

Determination of copper, cadmium, lead and bismuth in phosphoric acid solutions by atomic-absorption spectrometry after extraction with diethylammonium diethyldithiocarbamate and butyl acetate

The possibility of applying diethylammonium diethyldithiocarbamate and butyl acetate for the extraction of copper, cadmium, lead and bismuth from molar solutions of orthophosphoric acid, and from solutions containing up to 55% pyrophosphoric acid and 20% tripolyphosphoric acid has been investigated. Some characteristics of the various diethylammonium diethyldithiocarbamate-butyl acetate-phosphoric acid systems are described. Suitable conditions have been found for flame atomic-absorption spectrometric determination of the ions extracted. This extraction/AAS approach has been used to determine copper, cadmium, lead and bismuth in some iron-, aluminium- and tin-containing samples dissolved in concentrated orthophosphoric acid. The same approach is used for determining 10(-5)-10(-6)% copper, cadmium and lead in orthophosphoric acid and in alkali-metal mono and dihydrogen phosphates.     

Atomic absorption spectrometry of tellurium with electrothermal atomization in a molybdenum microtube

Hydrogen, added to argon purge gas, is necessary to protect the molybdenum microtube atomizer from oxidation, but it increases the atomization temperature and decreases the maximum absorbance of tellurium. A mixture of thiourea and copper removes the interfering effects of diverse elements and counteracts the effect of hydrogen. Tellurium (20–200 ppm) in copper can be determined after extraction as a chloride complex.     

APDC-MIBK extraction system for the determination of trace elements in saline waters by atomic-absorption spectrophotometry

A technique has been developed for the determination of "soluble" cobalt, copper, iron, lead, nickel and zinc in saline waters by simultaneous extraction of their complexes with ammonium pyrollidine dithiocarbamate (APDC) into methyl isobutyl ketone (MIBK) and subsequent analysis by atomic-absorption spectrophotometry. Particulate matter is analysed separately by dissolving millipore filters in an acetone-hydrochloric acid mixture. Various analytical and instrumental parameters have been evaluated. The method is selfcompensating in that it makes allowance for any incomplete extraction of the complexes. The technique has been applied to the determination of these elements in sea-water and saline lakes.     

The spectrophotometric determination of tellurium with bismuthiol II after separation with 4,4'-methylenediantipyrene and 1,1,2,2-tetrachloroethane

Tellurium can be isolated from most other elements by the extraction of its complex with 4,4'-methylenediantipyrene into 1,1,2,2-tetrachloroethane. After isolation tellurium can be determined photometrically as its complex with bismuthiol II in chloroform. The procedure can be applied to copper and copper-based materials in the presence of many elements normally associated with copper, including selenium. The procedure is lengthy but straightforward, precise and subject to few interferences.     

Application of platinum gauze activated by hydrogen to the adsorption separation of silver traces and their determination by aas or spectrophotometry

A method ("electrosorption") has been developed for separation of silver from copper by its deposition through internal electrolysis with hydrogen adsorbed on a platinum surface. The silver can then be stripped and determined by atomic-absorption spectrometry or the dithizone method. The activation of the platinum surface with adsorbed hydrogen can be achieved either electrolytically or by passing hydrogen gas through the solution in which the platinum is immersed. The method of electrosorption has been successfully applied to determination of trace levels of silver in copper metal.     

Determination of tellurium in geochemical materials by flameless atomic-absorption spectroscopy

A method is described for the determination of tellurium at nanogram levels in rocks and in other complex materials by the use of flameless atomic-absorption spectroscopy. A very selective organic extraction procedure is applied to avoid matrix interference effects during extraction of Te and the atomization stage in the graphite furnace. Prior separation of iron and other interfering elements is achieved by a combined cupferron-ethyl acetate extraction. Tellerium is extracted from 6M hydrochloric acid with MIBK and stripped into aqueous medium. Pipetting of the aqueous extract into the graphite furnace gives fairly good instrumental reproducibility (2-3% error). Detection limits of about 10 ppM Te for a 0.5-g sample have been achieved with the medium-performance apparatus used. Results for Te in some geochemical reference materials are reported. Indications are given for the determination of Sb and Mo in the same solutions.