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.     

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.     

Separation of bismuth from gram amounts of thallium and silver by cation-exchange chromatography in nitric acid

Traces and small amounts of bismuth can be separated from gram amounts of thallium and silver by successively eluting these elements with 0.3M and 0.6M nitric acid from a column containing 13 ml (3 g) of AG50W-X4, a cation-exchanger (100-200 mesh particle size) with low cross-linking. Bismuth is retained and can be eluted with 0.2M hydrobromic acid containing 20% v/v acetone, leaving many other trace elements absorbed. Elution of thallium is quite sharp, but silver shows a small amount of tailing (less than 1 gmg/ml silver in the eluate) when gram amounts are present, between 20 and 80 mug of silver appearing in the bismuth fraction. Relevant elution curves and results for the analysis of synthetic mixtures containing between 50 mug and 10 mg of bismuth and up to more than 1 g of thallium and silver are presented, as well as results for bismuth in a sample of thallium metal and in Merck thallium(I) carbonate. As little as 0.01 ppm of bismuth can be determined when the separation is combined with electrothermal atomic-absorption spectrometry.     

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.     

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.     

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.     

Second harmonic a.c. anodic stripping voltammetry of metals at trace level: simultaneous determination of lead and thallium, and bismuth and antimony

Pairs of elements with very small differences in their half-wave potentials were determined at trace levels by second harmonic a.c. anodic stripping voltammetry. The simultaneous determination of lead and thallium as well as that of bismuth and antimony in 1M hydrochloric acid as supporting electrolyte was found to be possible in the range of concentration ratios: 7:1 > or = C(Pb):C(Tl) > or = 1:36 and 45:1 > or = C(Sb):C(Bi) > or = 1:35, with <5 % relative error due to mutual interference. The limit of detection was approximately 10(-8)M for all four elements, and the precision and error were 2-3%. The simultaneous determination of these metals in mixtures with concentration ratios outside the quoted ranges is still feasible by the standard-addition technique.     

Studies on metal — protein interactions: Inter-comparison among various approaches

Binding ability of mercury, thallium, lead and bismuth with Erythrina variegata seed protein have been investigated using tracer packet technique. Due to the lack of standard methods, inter-comparisons have been made among three different approaches, like trichloroacetic acid (TCA) precipitation, isoelectric precipitation and dialysis of protein after incubation with the metals. Good agreement was observed for all the cases except that of lead.     

The polarographic determination of thallium

A polarographic method is described for the determination of thallium in sodium triphosphate supporting electrolyte. The incorporation of 0.1% camphor in the electrolyte displaces the cathodic steps of many interfering ions, e.g., lead(II), copper(II), iron(III) and bismuth(III) to a more negative potential (1?.0 V), well away from the thallium step which remains unaffected.     

Solvent extraction separation of gallium with 18crown6 from chloride media

Gallium was quantitatively extracted with 0.02M 18crown6 in methylene chloride from 6M hydrochloric acid, then stripped with 1M acetic acid and determined with 2-(pyridylazo)naphthol with measurement at 545 nm. Gallium was separated from indium, thallium, lead, aluminium and bismuth. The method was applied to determination of gallium in bauxite.     

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.     

Application of polyethylene glycol for "electrochemical masking" in direct-current polarography

The use of polyethylene glycols (PEG) of molecular weight from 200 to 15,000 for electrochemical masking has been investigated. A pH-4.4 tartrate buffer was found to be the most suitable supporting electrolyte, and 0.1% the optimum PEG concentration. PEGs of m.w. below 600 had little effect on the waves examined, and are useless for electrochemical masking. Under the conditions chosen, the waves of Bi(III), Sb(III) and In(III) are completely suppressed; the Cd(II) and Pb(II) waves are shifted to more negative potentials, and the Tl(I) wave is scarcely affected by PEGs. The Cu(II) wave behaves differently from the others. A method is proposed for the determination of lead and/or thallium in the presence of up to 5000-fold w/w ratios of bismuth, antimony or indium. The determination of both lead and thallium is only possible when the amounts are not too different, as the waves are quite close. Copper(II) interferes.     

The Use of the Bismuth Film Electrode for the Anodic Stripping Voltammetric Determination of Tin

Bismuth coated glassy carbon electrodes have been applied to the square‐wave anodic stripping voltammetry (SWASV) of trace concentrations of tin. Optimization of Bismuth Film Electrode (BFE) performance was conducted after initial comparison with the more traditional mercury electrode. Simultaneous deposition of tin and bismuth at ?1.3 V for 2 minutes in a supporting electrolyte of 2.5 M sodium bromide utilizing a square‐wave stripping step, allowed analysis of tin at the μg L^?1 level. Parameters, such as deposition potential and time, bismuth concentration, square‐waveform settings including amplitude, step height and frequency were studied and optimized. The dependence of stripping current on deposition time indicates that using longer deposition time should facilitate sub μg L^?1 analysis. Tin was analyzed simultaneously with cadmium and either indium or thallium; Where as lead and copper were not resolved from the stripping peaks of tin and bismuth respectively. Finally, the method was applied to the analysis of tin in fruit juice.     

Amperometry with two polarisable electrodes-XI Determination of bismuth by EDTA titration

Optimum conditions have been found for a highly selective determination of bismuth via EDTA titration with biamperometric indication of the end-point. The influence of the applied potential, pH and stirring on the accuracy and selectivity of the determination has been studied. In a medium of 0.4M nitric acid only high concentrations of iron(III) and copper(II) interfere with the determination of bismuth. Zirconium, thallium(III) and indium interfere even in small concentrations. The average error of the determination of 5-100 mg of bismuth (when titrated with 0.05M EDTA solution) is +/-0-1 % rel. and for the determination of 0.5-10 mg it is +/-0.3% rel. (0.005M EDTA). The method has been verified by the analysis of a Wood's metal of known composition.     

The determination of thallium in rocks and biological materials at ng g−1 levels by differential-pulse anodic stripping voltammetry and electrothermal atomic absorption spectrometry

Thallium is volatilized from biological materials and rocks after admixture with silicic acid and cellulose/magnesium chloride, respectively, by combustion in oxygen in a quartz apparatus, and from rocks after admixture with magnesium chloride by fusion at 1250°C in a quartz tube drawn to a capillary at one end and sealed at the other end. The condensed thallium is dissolved in a small volume of acid which is used directly to determine thallium procedure was found to be 1 ng g^?1 (deposition time 10 min). The results are in satisfactory agreement with those obtained by electrothermal atomic absortion spectrometry after extraction.     

Analytical applications of a liquid anion-exchanger for the separation of uranium(IV) in malonate solution

Uranium was quantitatively extracted with 4% Amberlite LA-1 in xylene at pH 2.5-4.0 from 0.001 M malonic acid. It was stripped from the organic phase with 0.01 M sodium hydroxide and determined spectrophotometrically at 530 nm as its complex with 4-(2-pyridylazo) resorcinol. Of various liquid anion-exchangers tested, Amberlite LA-1 was found to be best. Uranium was separated from alkali and alkaline earth metal ions, thallium(I), iron(II), silver, arsenic(III) and tin(IV) by selective extraction, and from zinc, cadmium, nickel, copper(II), cobalt(II), chromium(III), aluminium, iron(III), lead, bismuth, antimony(III) and yttrium by selective stripping. The separation from scandium, zirconium, thorium and vanadium(V) was done by exploiting differences in the stability of chloro-complexes.     

Cation-exchange behaviour of the platinum group and some other rare elements in hydrobromic acid-thiourea-acetone media

Ion-exchange distribution coefficients and elution curves are presented for copper(I), silver, gold(I), palladium, platinum(II), rhodium(III), iridium(III), ruthenium(III), osmium(III), mercury(II), thallium(I), tellurium(II), lead and bismuth in mixtures of thiourea, hydrobromic acid, acetone and water, with the cation-exchange resin AGW50W-X4. The system affords excellent separations of rhodium, mercury, silver (or copper), tellurium, gold, and palladium (or platinum) from each other.     

Separation of gallium, indium and thallium by extraction with n-octylaniline in chloroform

Extraction of gallium(III), indium(III) and thallium(III) with n-octylaniline in chloroform at various concentrations of hydrogen halide acids (HCl, HBr, HI) has been studied and a scheme for their separation proposed. The procedure can be successfully applied to the separation and determination of gallium in presence of mercury, bismuth, manganese, zinc and lead; indium in presence of bismuth, antimony, lead, mercury, cadmium and zinc; and thallium in presence of mercury, cadmium, manganese, aluminium, tin and antimony. The advantage of the method is that the reagent can be recovered for reuse. The method is simple, rapid, and effects clear-cut separation.     

Separation of thallium-201 from Tl,Pb and Bi cyclotron target materials

Radiochemical methods of thallium-201 separation from proton-irradiated thallium, lead and bismuth targets have been developed. The procedures are based on the processes of coprecipitation, ion-exchange chromatography and high temperature gas chemistry. The purity of thallium samples complies with requirements of nuclear medicine for thallium-201 product.     

复杂高铋物料中铅的Na2EDTA滴定法测定

复杂高铋物料中,铋、砷、锑、锡四元素含量高且共存时会影响铅的测定。特别是铋含量高时对铅的测定影响大。实验用EDTA—酒石酸联合掩蔽铋、砷、锑、锡,在稀硫酸介质中以硫酸钾为沉淀剂,使铅生成硫酸铅钾复盐沉淀而与铋、砷、锑、锡、铁、铜、锌、铝、钴、镍等干扰离子分离,沉淀以乙酸-乙酸钠浸取,二甲酚橙为指示剂,Na2EDTA滴定法测定铅。试验进一步优化了测定条件,确定最佳条件：硫酸（1 1）加入量为7mL、硫酸钾用量为5g、煮沸时为5min、沉淀陈化时间为2h、EDTA 50g/L 加入量为10mL、酒石酸用量为0.5g,铅的回收率99.70% ～100.65%。将实验方法应用于测定复杂高铋物料中铅,标样BY0111-1与给定值一致,相对标准偏差（n=11）RSD 0.20%～0.23%,满足生产测试要求。