Test determination of titanium(IV) and germanium(IV) in waste and natural waters in the presence of each other

It was demonstrated that trihydroxyfluorones immobilized on cellulose matrices can be used as the reagents for the rapid determination of titanium(IV) and germanium(IV). A high retention of trihydroxyfluorones on cellulose paper (78–98%) and strong chemically stable mixed fabric (74–97%) makes it possible to use these materials for the immobilization of the reagents. Mixed fabric (viscose with cotton) with immobilized phenylfluorone was used for the test determination of 0.05–5 mg/L titanium(IV) and 0.01–5 mg/L germanium( IV) by the color intensity of the reaction zone of the indicator matrix after passing 20 mL of the analyzed solution through it. A test procedure was developed for the determination of 1–200 mg/L titanium(IV) and 0.5–1000 mg/L germanium(IV) by the length of the colored zones of the test strips sealed in a polymer film. The time of the analysis is 10–15 min. The relative standard deviation of the results of the determination of germanium( IV) and titanium(IV) is no higher than 30%.     

Cathodic stripping voltammetric determination of selenium(IV) at a thin-film mercury electrode in a thiocyanate-containing electrolyte

The well-known method for the determination of selenium(IV), which is based on the cathodic stripping voltammetry of copper(I) selenide, has been adapted for application at the thin-film mercury electrode on glassy carbon (TFME). Insufficient reproducibility and sensitivity have been overcome by using a 0.1 mol/L HClO₄ electrolyte solution containing 0.02 mol/L thiocyanate ions. Thiocyanate ions have been found to increase the peak height of the selenium response and shift it to more positive potentials. This behaviour is explained by an adsorption of SCN^– at the interface glassy carbon/Cu₂Se and its action as an electron transfer catalyst between glassy carbon and copper(I) selenide. A 3σ-detection limit of 75 ng/L Se^(IV) has been achieved. The relative standard deviation is 5.2% at 5 μg/L selenium(IV). The influence of cadmium(II), arsenic(III), zinc(II), iron(III) and lead(II) ions on the selenium response has been studied. In case of lead ions, a new signal occurred at more negative potentials than the reduction of Cu₂Se. This signal, which is probably due to the reduction of PbSe, can also be used for the determination of selenium(IV). Received: 13 November 1996 / Revised: 19 December 1996 / Accepted: 24 December 1996     

Test analysis method using ion pairs of pyrocatechol azo derivatives and trihydroxyfluorones with cetylpyridinium and their chelates with metal ions immobilized on paper

A two-stage procedure is proposed for the immobilization of ion pairs of pyrocatechol azo derivatives and trihydroxyfluorones and their chelates with metal ions on paper. It is demonstrated that ion pairs of phenylfluorone and thiazolylazopyrocatechol with cetylpyridinium can be used for the test determination of 0.01-10 mg/L Ti(IV), 0.05-20 mg/L Mo(VI), and 0.1–20 mg/L W(VI) and V(V) by the length of the colored zone of test strips after their contact with a test solution and for the determination of 0.01-0.5 mg/L Al and Mo(VI) and 0.001-0.1 mg/L Ti(IV) by the color intensity of reactive papers after passing a test solution. Chelates of Mo(VI) with tiazolylazopyrocatechol and of Sb(III) with phenylfluorone are used for the test determination of 0.01-1000 mg/L cationic surfactants. The selectivity of reactions is studied, and procedures are proposed for the determination of the above elements in different materials. The relative standard deviation of the results of analysis is no higher than 50%.     

Spectrophotometric determination of traces of selenium(IV) in various environmental samples using the flow-injection technique (FIT)

A simple, sensitive, and rapid flow-injection spectrophotometric method was developed for the determination of trace amounts of selenium(IV). The method is based on the oxidation reaction of 3-methyl-2-benzothiazolinone hydrazone hydrochloride (MBTH) by selenium(IV) followed by the coupling reaction with chromotropic acid (4.5-dihydroxy naphthalene-2.7-disulphonic acid) in a basic medium (phosphate buffer, pH 10.5) to give a pink derivative with λ_max 530 nm that is stable for more than 7 days at 35°C. The reaction and flow conditions of the full experimental design were optimized. A detection limit (2s) of 0.25 μg/L Se(IV) was obtained at a sampling rate of 10 samples per hour. Beer’s law is obeyed for a Se(IV) concentration range of 0.05–0.5 μg/mL at the wavelength of maximum absorption. The detailed study of various interference ions indicates that the method is highly selective. The method was successfully applied to the determination of traces of selenium(IV) in various water samples. The results obtained were in good agreement with those obtained by the reported methods at the 95% confidence level. The text was submitted by the authors in English.     

Anodic stripping voltammetry of tellurium(IV) in aqueous solution and mixed solvents

The anodic stripping determination of Te(IV) using a rotating glassy carbon disc electrode is described. 0.1 ppm tellurium can be determined in 1 M HCl. Interfering effects of the metals forming intermetallic compounds with tellurium on the electrode are eliminated by solvent extraction. Te(IV) is determined either after its extraction — as an ion associate or as the chelate with diphenylthiocarbazone — in the organic phase which is adjusted for the stripping determination by the addition of methanolic solution of LiCl or after the separation of all interfering elements by an extraction procedure involving the extraction of Te(IV) into methylisobutylketone and back extraction of Te(IV) with water followed by the separation of the remaining interfering elements into diisopropylether. The proposed method enables the determination of 10 μg Te in the presence of 25 mg Pb and Sb and 0.5 mg Ag, Cu, Bi, As, Sn, Cd, Zn with reproducible results and error ±5%.     

Solid-phase fluorescence determination of gallium(III) with morin and lumogallion immobilized on cellulose matrices

It has been demonstrated that the fluorometric test determination of gallium(III) can be performed with morin and lumogallion immobilized on thin-layer cellulose matrices. Test procedures have been developed for the determination of Ga(III) in the range 0.5–90 mg/L by the length of fluorescence zone on a test strip sealed into a polymer film (after its contact with the test solution) in the ranges 0.001–1 and 0.01–1 mg/L with the visual detection of the fluorescence of the indicator matrix with morin and lumogallion, respectively (after passing 100 and 20 mL of a test solution through it), and in the range 0.0001–0.1 mg/L by detecting the fluorescence with a portable fluorimeter.     

Spectrophotometric determination of tellurium(IV) in environmental and telluride film samples

Three simple, rapid, and sensitive spectrophotometric methods for the determination of traces and ultratraces of tellurium(IV) were studied. These methods were based on either the oxidation of 4-bromophenylhydrazine (4-BPH) by tellurium in a basic medium and coupling with N-(1-naphthyl)ethylenediamine dihydrochloride (NEDA) to give a purple-colored product, the oxidation of 3-methyl-2-benzothazoline hydrazone hydrochloride (MBTH) by tellurium in a basic medium and coupling with chromotropic acid (CA) to yield a red-colored species, or the oxidation of 2,3-dimethoxystrychnidin-10-one (2,3-DMSO) by tellurium in an acidic medium to yield an orange-colored derivative. Beer’s law was obeyed in the range 1.0–25 μg/mL (purple-colored product), 0.7–20 μg/mL (red-colored species), and 0.3–15 μg/mL (orange-colored derivative). The reaction conditions and other analytical parameters were investigated to enhance the sensitivity of the proposed methods. The tolerance limit of various ions has been studied. The methods were applied to the analysis of tellurium in water samples (waste, river, lake, and spring), plant materials, soil samples, and telluride thin films. The results obtained were superior to those obtained using the reported method. The performances of the proposed methods were evaluated in terms of ‘t’-test and variance ratio ‘f’-test, which indicate the advances of the proposed methods over reported methods. The text was submitted by the authors in English.     

Coulometric determination of lead(II) and lead(IV) in high-T c superconductors containing copper and bismuth

The behavior of Pb(II) and Pb(IV) was studied by voltammetry in supporting electrolytes containing 0.1 M NaOH or 0.1 M NaOH + 0.1 M Na₃Cit at a graphite and a mercury thin-film electrodes. The best conditions were found for the coulometric determination of Pb by the oxidation of Pb(0) to Pb(II) in the presence of 5- to 20-fold amounts of Bi(III) and Cu(II) within the range 0.2–2 mg Pb(II) with an error and a relative standard deviation of less than 0.5%. Along with the procedure proposed previously for the determination of Pb(II) and Pb(IV) present simultaneously using a platinum gauze electrode, this procedure was applied to the determination of Pb(II) and Pb(IV) in samples of high-T_c. Cu-Bi superconductors. For samples of high-T_c. Bi-Pb-A-Cu-0 superconductors (A = Ba or Sr-Ca) containing from 2 to 12% Pb(II), the relative standard deviation was less than 0.5%; for 0.6–7% Pb(IV), it was 1-0.2%.     

Determination of Selenium(IV) by Stripping Voltammetry at a Mercury-Film Electrode

A procedure was proposed for the determination of selenium(IV) by stripping voltammetry on a mercury-film electrode at an electrolysis potential of +0.4 V versus the saturated silver–silver chloride reference electrode in a 1 M H₂SO₄ solution. The current of the cathodic peak is a linear function of the selenium(IV) concentration in the range from 5 × 10^–3 to 3 × 10^–1 mg/L (6.3 × 10^–8 to 3.8 × 10^–6 M) at a time of electrolysis of 30 s (t _el). The detection limit for selenium is 1 × 10^–4 mg/L (1.3 × 10^–9 M) at t _el = 300 s. It was shown that selenium(IV) can be determined in the presence of 10 mg/L Zn(II), 1 mg/L Cd(II), 0.5 mg/L Pb(II), and 0.2 mg/L Cu(II). A procedure for the determination of selenium in natural, mineral, and potable water was proposed.     

Xerogels doped with phosphomolybdic heteropoly compounds: Indicator tubes and indicator powders for determining hydrazines and tin(II) in solution

Xerogels were prepared on the basis of silicon dioxide and doped with phosphomolybdic heteropoly acid, its ammonium salt, and the Vavele reagent. Reactions of modified xerogels with hydrazines, ascorbic acid, hydroquinone, iodide ion, and iron(II) and tin(II) ions were studied by solid-phase spectrophotometry. It was found that the oxidizing properties of heteropoly compounds enhance when they are included into xerogels. It was found that the formal redox potential of phosphomolybdic acid in xerogel is +0.751 V at pH 3.6. Indicator tubes were proposed for the test determination of 10–80 mg/g tin(II) in reagents used in the synthesis of radiopharmaceutical preparations. Indicator powders and indicator tubes were proposed for the test determination of hydrazines in solution (analytical ranges 0.08-6 mg/L and 0.02-1 mg/L, respectively). Deceased.     

Ceramic composite electrode for the determination of selenium(IV) by stripping voltammetry

A ceramic composite electrode for the determination of selenium(IV) was manufactured using solgel and screen-printing technologies. This electrode exhibits a higher sensitivity and selectivity in comparison with the other studied carbon-containing electrodes. The effect of the type and amount of graphite powder, modifier, catalyst, and pore-forming agent on the properties of the ceramic composite electrode was investigated. It was found that an increase in the pore size in the electrode reduced the selectivity of selenium(IV) determination. The calibration plot was linear over the range 0.1–20 μg/L at an accumulation time of 10 s. The relative standard deviation for the determination of 1.0 and 0.05 μg/L of selenium(IV) (n = 5) was 3% and 8%, respectively. The detection limit of selenium(IV) was 0.02 μg/L at an accumulation time of 90 s. The results of selenium(IV) determination in natural and mineral waters are presented.     

Solid-phase spectrophotometric iodometric determination of nitrite and selenium(IV) using a polymethacrylate matrix

Procedures for the iodometric solid-phase spectrophotometric determination of nitrite and selenium( IV) using a polymethacrylate matrix are proposed. The procedures are based on the reaction of nitrite and selenium(IV) with iodine in an acidic medium with the release of free iodine in amounts equivalent to those of the substances to be determined, extraction of the iodine formed with a polymethacrylate matrix, and measurement of absorbance of the matrix at 370 nm. The developed procedures ensure the determination of 0.01–0.12 mg/L of nitrite and 0.05–0.40 mg/L of selenium(IV) with limits of detection of 0.005 and 0.03 mg/L, respectively. It was shown that the proposed procedures can be applied to the determination of selenium(IV) in mineral water and nitrites in vegetables and soil.     

Determination of selenium(IV) and tellurium(IV) by differential pulse polarography

Differential pulse polarographic methods for the determination of selenium(IV) and tellurium(IV) in nitric acid medium are described. The peak current is maximal when 0.25M nitric acid medium is used, the DPP peaks for Se(IV) and Te(IV) being at -0.54 and -0.8 V vs. Ag/AgCl respectively. The peak current is a linear function of selenium concentration over three ranges, 5.1 x 10(-6)-1.3 x 10(-5), 1.27 x 10(-5)-1.27 x 10(-4) and 1.27 x 10(-4)-7.60 x 10(-4)M Se(IV), with different slopes. The plot for Te(IV) is linear over the range 0.78 x 10(-6)-9.40 x 10(-5)M.     

Optimization of the reduction of Se(VI) to Se(IV) in a microwave oven

 Parameters for the reduction of Se(VI) to Se(IV) in HCl medium by heating in a microwave oven have been optimized. The reduction resulted to be quantitative applying 100% power, corresponding to 600 W heating for 2 min in 6 mol/L or for 3 min in 4 mol/L HCl. The behavior of selenomethionine and selenocystine under the optimized reduction conditions was studied in order to evaluate a possible interference of these selenium species in the determination of Se(VI). The final determination of Se(IV), and Se(VI) were done by hydride generation-atomic absorption spectrometry. The analytical merits of the method are reported. The method was applied to the selective determination of Se(IV), and Se(VI) in spiked river and lake water. Received: 6 December 1996/Revised: 1 April 1997/Accepted: 3 April 1997     

Separation of selenium(IV) and tellurium(IV) from mixtures by extraction chromatography with trioctylphosphine oxide

The reversed-phase extraction chromatographic separation of selenium(IV) and tellurium(IV) from several elements with trioctylphosphine oxide as extractant is reported. Selenium was extracted from 6M hydrochloric acid containing 7M lithium chloride was stripped with 4M hydrochloric acid, and tellurium was extracted from either the same medium as selenium or from 4M hydrochloric acid, and stripped with 1-2M hydrochloric acid. Selenium and tellurium can be separated from multicomponent mixtures.     

Chemiluminescence system of Ce(IV)-RhB-bismerthiazol

A novel chemiluminescence system for the determination of bismerthiazol is first described in this paper. It is based on the chemiluminescence reaction of bismerthiazol and Ce(IV) in nitric acid solution. The emission intensity could be enhanced greatly by Rhodamine B. The chemiluminescence intensity was proportional to bismerthiazol concentration over the range 30–1000 μg/L. The detection limit was 12 μg/L (3σ) and the relative standard deviation is 2.4% for 500 μg/L of bismerthiazol (n = 11). The proposed method was successfully applied to the determination of bismerthiazol in water and in rice. The recovery was 96.4%–104.1%. __________ Translated from Chinese Journal of Applied Chemistry, 2007, 24(5): 593–595     

Kinetic studies on the reduction of a nickel (III) oxime-imine complex by sulphur(IV) and selenium(IV)

The kinetics of the reduction of [Ni^III(L¹)]²⁺ (where HL¹ = 15-amino-3-methyl-4,7,10,13-tetraazapentadec-3-en-2-one oxime) by sulphur(IV) and selenium (IV) over the regions pH 2.50–8.02 and 2.01–4.00 respectively have been investigated at 30°C. Attempts were made to evaluate the reactivity of all the reacting species, of sulphur(IV) and selenium(IV) by considering suitable pH ranges. The oxidation of SC₂·H₂O and HSO ₃ ⁻ is proposed to proceed through the formation of a hydrogen-bonded adduct. The reaction with SO ₃ ²⁻ seems to follow a direct outer-sphere route which is well supported by Marcus crossrelation calculation. The oxidation of HSeO _l3 ⁻ is ≈ 10³ times slower than that of H₂SeO₃. The kinetic data indicate that the oxidation of sulphur(IV) by [Ni^IIIL¹)]²⁺ is much more favourable as compared to the corresponding oxidation of selenium(IV).     

Indicator Tubes and Indicator Powders for Determining Fluoride and Chloride Ions

Noncovalent immobilization of Arsenazo I, Alizarin Red, Xylenol Orange, and diphenylcarbazone by incorporation into silicic acid xerogels and modification of silica gels was studied, and procedures for determining fluoride and chloride ions by solid-phase spectrophotometry and test methods were developed. Reactions of immobilized reagents with aluminum(III), zirconium(IV), and mercury(II) were studied. The possibility of using immobilized reagent–metal ion–halide ion systems for the determination of halide ions was assessed. Indicator powders were proposed for determining 0.5–10 mg/L fluoride ions and 1–30 mg/L chloride ions, and indicator tubes were developed for determining 20–200 mg/L chloride ions. The determination of fluoride and chloride ions is based on exchange complexation reactions proceeding in the systems immobilized Xylenol Orange–zirconium(IV) and immobilized diphenylcarbazone–mercury(II), respectively. Performance characteristics of the developed procedures were estimated. The procedures were verified by determining halide ions in Narzan mineral water.     

Determination of Zirconium (IV) and Aluminium (III) in Waste Water

 Zirconium (IV) was determined spectrophotometrically by reaction with quercetin as primary ligand and oxalate as secondary ligand. Polyvinylpyrrolidone (PVP) was used as protective colloid to solubilize the formed zirconium quercetin oxalate ternary complex. The molar absorptivity of the 1:3:1 (zirconium–quercetin–oxalate) complex is 7.31 × 10⁴ L·mol⁻¹ cm⁻¹ at 430 nm with a stability constant of 8.2 × 10²⁰ and its detection limit is 0.16 mg/L. Beer’s law is rectilinear up to 1.46 mg/L of zirconium (IV). The sensitivity index is 1.25 ng cm⁻². The reaction of aluminium (III) with quercetin in presence of PVP as a surfactant has been studied spectrophotometrically. The molar absorptivity of the 1:3 (aluminium–quercetin) complex is 8.09 × 10⁴ × L·mol⁻¹·cm⁻¹ at 433 nm, its stability constant is 2.6 × 10¹³ with sensitivity index of 0.33 ng·cm⁻² and its detection limit is 0.08 mg/L. The optimal conditions for the quantitative determination of zirconium and aluminium were studied. The proposed methods are examined by statistical analysis of the experimental data. The methods are free from interference of most cations and anions. The proposed methods have been used to determine zirconium and aluminium in industrial waste water. Received May 30, 2001; accepted November 2, 2001; published online July 15, 2002     

A visual test method for determining selenium(IV) with indigocarmine immobilized on silica

A solid reagent based on silica successively modified by quaternary ammonium salt and indigocarmine is proposed for the test determination of selenium(IV). The detection limit for selenium is found to be 10 μg/L using catalytic reaction of the reduction of immobilized indigocarmine by sulfide as an indicator reaction. The calibration graph is linear in the range of selenium concentrations from 50 to 400 μg/L. Alkali and alkaline-earth metals, NH ₄ ⁺ , Cl^?, NO ₃ ^? , and SO ₄ ^2? do not interfere with the determination of selenium. The interference from heavy metals is eliminated by introducing EDTA. The procedure was tested in determining selenium in preparations of vitamins and biologically active supplement.