Selective complexometric determination of bismuth with mercaptans as masking agents, and its estimation in alloys

A method is proposed for selective complexometric determination of bismuth. To a solution containing bismuth and other cations, excess of EDTA is added and the surplus is back-titrated at pH 5-6 with lead nitrate (Xylenol Orange as indicator). Thioglycollic or mercaptopropionic acid is then added to decompose the bismuth-EDTA complex and the liberated EDTA is titrated with lead nitrate. The interference of various cations has been studied and the method employed to determine bismuth in a variety of alloys.     

Spectrophotometric determination of vitamin E (alpha-tocopherol) using copper(II)-neocuproine reagent

A coated graphite-epoxy ion-selective electrode for bismuth(III), based on the ion-pair between the [Bi(EDTA)](-) anion and tricaprylylmethylammonium cation (Aliquat 336S) incorporated onto a poly(vinylchloride) (PVC) matrix is constructed. A thin membrane film of this ion-pair, dibutylphthalate (DBPh) or ortho-nitrophenyloctylether (o-NPOE) in PVC was deposited directly onto a Perspex(R) tube which contained a graphite-epoxy conductor substrate attached to the end of a glass tube. The coating solution was prepared by dissolving 30% (w/w) of PVC in 10 ml of tetrahydrofuran following addition of 65% (w/w) DBPh or o-NPOE and 5% (w/w) of the ionic pair. The effect of pH, EDTA concentration and some cation and anion on the electrode response is investigated. The bismuth(III) ion-selective electrode shows a linear response in the bismuth(III) concentration range from 1.0 x 10(-8) to 1.0 x 10(-1) mol 1(-1) and 1.0 x 10(-7) to 1.0 x 10(-1) mol 1(-1) and a slope of 56.8 and 59.2 mV dec.(-1) for the polymeric membranes containing DBPh and o-NPOE, respectively. The lifetime of this electrode was superior to 1 year (over 1600 determinations for each polymeric membrane), with practical detection limits of 6.3 x 10(-9) and 4.4 x 10(-8) mol 1(-1) with these plasticizers. Application of this electrode with bismuth(III) determination in a stomach anti-acid sample is described.     

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.     

Spectrophotometric determination of bismuth(III) with o-hydroxyhydroquinonephthalein in the presence of Brij 58

A simple and sensitive spectrophotometric determination of bismuth(III) is based on the reaction between bismuth(III) and o-hydroxyhydroquinonephthalein in the presence of Brij 58 in acidic media. The calibration graph is linear over the range 0-3.5 mug/ml bismuth(III) in the final solution, and the apparent molar absorptivity at 520 nm is 9.03 x 10(4) l. mole(-1). cm(-1). The proposed method is 2-10 times more sensitive than other methods, and simpler. It has been applied to the assay of bismuth(III) in pharmaceutical preparations, such as dermatol and bismuth subnitrate, with good results.     

New spot-test for silver(I) based on double iodide formation with bismuth(III)

The formation of an intense brownish-maroon or maroon-red product by the interaction of silver(I) and bismuth(III) solution in the presence of iodide forms the basis of a new and specific spot-test procedure for silver. The test is conducted on a spot plate with 2 or 3 drops of 2% potassium iodide solution, 1 drop of 1% bismuth(III) nitrate solution, and 1 drop of test solution. Limit of detection is 0.01 mug; limit of dilution is 1:5 x 10(6). Most cations and anions do not interfere. Only Tl(I), Cs, S(2)O(2-)(3), EDTA, pyridine, excess of thiourea, oxidizing ions (NO(-)(2), IO(-)(3), IO(-)(4), MnO(-)(4), BrO(-)(3), and S(2)O(2-)(8)) and ions such as Cl(-), Br(-), I(-), SCN(-), and N(-)(3) which cause precipitation of silver, interfere. The product formed is most probably Ag(2)BiI(5).     

Spectrophotometric titration of bismuth with EDTA

A new spectrophotometnc method for the estimation of bismuth with EDTA, using iron-salicylate complex as the indicator, has been developed. The determinations were carried out by measuring the absorbance at 520 mmu. of solutions containing bismuth, iron(III), salicylic acid and various quantities of EDTA, at pH 0.5. It has been shown from the stability constants of the complexes present that before the end-point iron(III) will not react appreciably with the Bi-EDTA complex. The interference from iron(III) in the estimation of bismuth, which is a serious drawback in many other methods, is eliminated in the present method, as iron(III) acts as the indicator.     

Spectrophotometric determination of sulfide in the presence of sulfite and thiosulfate via the precipitation of bismuth(III) sulfide.

A photometric method has been developed for the determination of sulfide at 10(-5) mol dm(-3) levels, which is based on the reaction of sulfide with a given excess amount of bismuth(III) to form a precipitate of bismuth(III) sulfide and on the spectrophotometric measurement of the residual bismuth(III) at 335 nm after extracting with bismuthiol II reagent from an aqueous solution containing acetate buffer into benzene. The presence of sulfite and thiosulfate up to 0.002 mol dm(-3) did not cause any interference in the determination of sulfide, because both sulfite and thiosulfate do not produce any precipitate with bismuth(III). A linear calibration plot with a negative slope was obtained for sulfide over the range of 5.00 x 10(-7) - 3.00 x 10(-5) mol dm(-3) (16.0 - 960 ppb). An experimental calibration plot was in accord with the theoretical plot, taking into account the known excess of bismuth(III), showing that the reaction of sulfide with bismuth(III) proceeded to completion. The relative standard deviation of results from 10 replicate determinations of standard sulfide (2.00 x 10(-5) mol dm(-3)) was 0.44%. The proposed method was successfully applied to the determination of sulfide in hotspring water samples without any pretreatment.     

Synthesis of cross-linked chitosan modified with the glycine moiety for the collection/concentration of bismuth in aquatic samples for ICP-MS determination.

A chelating resin, cross-linked chitosan modified with the glycine moiety (glycine-type chitosan resin), was developed for the collection and concentration of bismuth in aquatic samples for ICP-MS measurements. The adsorption behavior of bismuth and 55 elements on glycine-type chitosan resin was systematically examined by passing a sample solution containing 56 elements through a mini-column packed with the resin (wet volume; 1 ml). After eluting the elements adsorbed on the resin with nitric acid, the eluates were measured by ICP-MS. The glycine-type chitosan resin could adsorb several cations by a chelating mechanism and several oxoanions by an anion-exchange mechanism. Especially, the resin could adsorb almost 100% Bi(III) over a wide pH region from pH 2 to 6. Bismuth could be strongly adsorbed at pH 3, and eluted quantitatively with 10 ml of 3 M nitric acid. A column pretreatment method with the glycine-type chitosan resin was used prior to removal of high concentrations of matrices in a seawater sample and the preconcentration of trace bismuth in river water samples for ICP-MS measurements. The column pretreatment method was also applied to the determination of bismuth in real samples by ICP-MS. The LOD of bismuth was 0.1 pg ml(-1) by 10-fold column preconcentration for ICP-MS measurements. The analytical results for bismuth in sea and river water samples by ICP-MS were 22.9 +/- 0.5 pg ml(-1) (RSD, 2.2%) and 2.08 +/- 0.05 pg ml(-1) (RSD, 2.4%), respectively.     

Effect of complexants on the adsorption and color reactions of lanthanum(III), uranium(VI), thorium(IV), and zirconium(IV) with Arsenazo M in the solid phase of an ANKB-50 fibrous ion-exchanger

The effect of complexants—acetic, aminoacetic, tartaric, malonic, and oxalic acids; EDTA; and Na₂CO₃—on the adsorption and subsequent determination of thorium(IV), lanthanum(III), uranium(VI), and zirconium(IV) with Arsenazo M in the solid phase of polyacrylonitrile fiber filled with an ANKB-50 anion exchanger was studied. Complexing agents were introduced into the solution at the step of metal ion adsorption. It was shown that zirconium and uranium interacted with the iminodiacetate groups of the adsorbent in the course of adsorption; the adsorption of elements from 10^?3 to 10^?2 M complexant solutions (except for tartaric and oxalic acids and EDTA) under the optimum conditions was enhanced as compared to their adsorption from pure solutions; complexation with Arsenazo M in the solid phase proceeded at a higher acidity than in the solution. When the elements were present simultaneously, their total concentration and individual thorium could be determined from malonic acid solutions with Arsenazo M by varying the concentration of acid and the adsorption pH.     

Determination of thallium in bismuth by differential pulse anodic-stripping voltammetry without preliminary separation

The determination of trace levels of thallium in bismuth and bismuth salts by differential pulse anodic-stripping voltammetry has been made possible by using a surfactant as an electrochemical masking agent, in addition to a complexing agent. In 0.2M EDTA at pH 4.5 as supporting electrolyte in the absence of surfactant, bismuth at concentrations below 10(-4)M does not interfere. When the electrolyte also contains tetrabutylammonium ions at 0.01 M concentration, bismuth can be tolerated at concentrations up 0.05M, and the height of the thallium peak is unaffected. It is thus possible to determine 1 nM Tl(I) in the presence of 0.05M Bi(III), i.e., Tl at the 1 x 10(-6)% level in bismuth. The precision of the determination and the recovery are satisfactory. Neither an 800-fold ratio of Cu(II) nor a 10(7)-fold ratio of Pb(II) to Tl(I) interferes in the determination. Other cations such as Zn(2+), Cd(2+), In(3+), Hg(2+), Fe(3+), Sb(3+) and Sn(4+) in 10(4)-fold molar ratio to Tl(I) have no effect on the determination. Thallium has been determined in bismuth metal and in bismuth nitrate of various degrees of purity.     

Determination of free acid in antimony(III) and bismuth(III) solutions

A method for the determination of free acid in antimony(III) and bismuth(III) solutions is given. A solution of the disodium salt of EDTA, 2-3 % in excess of the stoichiometric amount, is added to the metal salt solution and titrated with sodium hydroxide solution potentiometrically or visually using a mixed indicator. The error in the method is less than 0.5 %.     

Adsorption of chromium from aqueous solution using chitosan beads

A basic investigation on the removal of Cr(III) and Cr(VI) ions from aqueous solution by chitosan beads was conducted in a batch adsorption system. The chitosan beads were prepared by casting an acidic chitosan solution into an alkaline solution. The influence of different experimental parameters; pH, agitation period and different concentration of Cr(III) and Cr(VI) ions was evaluated. A pH 5.0 was found to be an optimum pH for Cr(III) adsorption, and meanwhile pH 3.0 was the optimum pH for the adsorption of Cr(VI) onto chitosan beads. The Langmuir and Freundlich adsorption isotherm models were applied to describe the isotherms and isotherm constants for the adsorption of Cr(III) and Cr(VI) onto chitosan beads. Results indicated that Cr(III) and Cr(VI) uptake could be described by the Langmuir adsorption model. The maximum adsorption capacities of Cr(III) and Cr(VI) ions onto chitosan beads were 30.03 and 76.92 mg g⁻¹, respectively. Results showed that chitosan beads are favourable adsorbents. The Cr(III) and Cr(VI) ions can be removed from the chitosan beads by treatment with an aqueous EDTA solution.     

Compleximetric back-titrations of traces of indium

Indium(III) has been determined in the microgram range by compleximetric back-titration with EDTA, bismuth(III) serving as the back-titrant. About 5 μg of indium(III)can be determined by means of a spectrophotometric indication method, the absorbance of the bismuth(III)-EDTA complex being measured at 260 nm. Smaller amounts of indium, down to 0.1 μg, can be determined by amperometric indication of EDTA at a rotating mercury electrode. A good selectivity is obtained by working at pH values between 1 and 2.     

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.     

Indirect Complexometric Determination of Bismuth Using 2-Mercaptoethanol as Masking Agent

 A new method for the complexometric determination of Bi in the presence of co-ions using 2-mercaptoethanol as selective masking agent has been proposed. Bismuth along with other ions in a given sample solution are initially complexed with excess of EDTA. The pH of the solution is adjusted to 5.0–6.0 using solid hexamine (10 ± 2 g) and the remaining uncomplexed EDTA is titrated with lead-nitrate solution using xylenol orange indicator. A known excess of 2-mercaptoethanol solution (5% alcoholic) is then added, the mixture is shaken well and the released EDTA from the Bi(III)-EDTA complex is titrated against standard lead-nitrate solution. The method is applied to the determination of bismuth in Wood’s alloy. Reproducible and accurate results are obtained for 2–40 mg of bismuth with relative errors ≤ 0.5% and standard deviations ≤ 0.04 mg. Received January 15, 1999. Revision March 29, 1999.     

Determination of bismuth(III) by direct potentiometry and potentiometric titration, with an electrode sensitive to Bi(3+)

A liquid-state ion-exchange electrode containing the chelate bismuth(III) complex with 5-mercapto-3-(naphthyl-2)-1,3,4-thiadiazole-2-thione in tetrachloroethane is applied to the determination of bismuth(III) by direct potentiometry and potentiometric titration. The influence of various interfering cations is discussed. In the presence of potassium cyanide as masking agent, Ni(II), Co(II), Cu(II), Ag(I) and Hg(II) do not interfere in the potentiometric EDTA titration. Satisfactory results have been obtained for the determination of bismuth(III) in Wood's metal and two pharmaceuticals.     

Electrochemical behavior and composition of bismuth sulfide coatings

Cyclic potentiodynamic voltammetry and X-ray photoelectron spectroscopy were used to study the electrochemical behavior and composition of bismuth sulfide coatings deposited by successive ionic layer adsorption and reaction on glassy carbon in a colloid solution of bismuth(III) compounds, with Na₂S as a sulfidizing agent.     

The complexes of bismuth(III) and nitrilotriacetic acid

The reaction between bismuth(III) and nitrilotriacetic acid (NTA or H(3)X) has been investigated by ultraviolet spectrophotometry. It has been established that bismuth(III) and NTA form two complexes with compositions bismuth(III): NTA = 1:1 and 1:2. The absorption maxima are at 243 nm (1:1) and 271 nm (1:2), the molar absorptivities being 8.00 x 10(3) and 8.20 x 10(3) l.mole(-1).cm(-1) respectively. The stability constants (at mu = 1.0) are: log beta(BiX) = 17.53 +/- 0.06 and log beta(B)(2)(3-) = 26.56 +/- 0.07. The possibility of the analytical application of BiX is briefly discussed.     

An analytically useful coulometric generation of micro amounts of metal ions : Part I. Electrogeneration of bismuth(III)

Bismuth(III) can be generated in a solution by electrolytically oxidizing dilute bismuth amalgam. Oxygen present in the solution contacting the amalgam also oxidizes the amalgam. Therefore normal coulometric circuits are not suitable for the generation of trace quantities of bismuth(III), even after prolonged passage of nitrogen. A procedure is described by which the interference of oxygen is eliminated so that amounts of bismuth(III) down to 5·10^-8 moles (in 30 ml) can be generated with 100% current efficiency.     

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。