Adsorption and colloidal behaviour of traces of tellurium(IV) in aqueous solutions

Various NaCl solutions containing traces of tellurium(IV) have been prepared. The effects of tellurium(IV) concentration and pH on the adsorption of tellurium(IV) on filter paper have been studied by filtration method. The effects of NaCl concentration, tellurium(IV) concentration and pH on the formation of a colloid have been also studied by ultracentrifugation and ultrafiltration methods. It has been found that tellurium(IV), at concentrations below about 10^–10M, in neutral NaCl solutions is adsorbed on filter paper and shows colloidal behaviour.     

Ultraviolet spectrophotometric determination of tellurium

Summary An ultraviolet spectrophotometric method for the determination of tellurium is proposed which is based on the formation of tetrakis-1-pyrrolidinecarbodithioate tellurium(IV) which is extractable with chloroform. Conformity to Beer's law was observed. The molar absorptivity at 257 nm is 8.12 · 10⁴ 1. mole^–1, cm^–1.

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Zusammenfassung Ein UV-spektrophotometrisches Verfahren für die Bestimmung von Tellur wurde vorgeschlagen, das auf der Reaktion von Te(IV) mit vier Äquivalenten 1-Pyrolidindithiocarbamat und der Extraktion des Reaktionsproduktes mit Chloroform beruht. Das Beersche Gesetz ist erfüllt. Die molare Extinktion bei 257 nm beträgt 8,12 · 10⁴ 1.Mol^–1.cm^–1.

     

Spectrophotometric determination of tellurium in concentrates and brasses by chloroform extraction of the tellurium (IV) hexabromide-diantipyrylmethane complex after separations by iron collection and xanthate extraction

A method for determining 0.0001–0.10% of tellurium in copper, nickel, molybdenum, lead and zinc concentrates is described. After sample decomposition, tellurium is separated from most of the matrix elements by co-precipitation with hydrous ferric oxide from an ammoniacal medium. After reprecipitation of tellurium and iron, the precipitate is dissolved in 12M hydrochloric acid, tellurium(VI) is reduced to the quadrivalent state by heating, and separated from iron, lead and other co-precipitated elements by chloroform extraction of its xanthate. The yellow ion-association complex formed between tellurium(IV) hexabromide and diantipyrylmethane is extracted into chloroform from a 2M sulphuric acid-0.6M potassium bromide medium. The molar absorptivity of the complex is 1.82 × 10³ l.mole⁻¹.mm⁻¹ at 336 nm, the wavelength of maximum absorption. Small amounts of iron, copper and molybdenum are co-extracted as xanthates under the proposed conditions but do not cause error in the result. Interference from antimony, which is co-extracted as the chloro-complex, is eliminated by washing the extract with water. The proposed method is also applicable to brasses.     

Separation of99Mo from132Te using thiourea as complexing agent. Application to the separation of99Mo from fission products

A radiochemical method to isolate⁹⁹Mo from¹³²Te, both produced in the fission of²³⁵U, has been developed. The method is based on the formation of a cationic complex of tellurium with thiourea in acid medium which is retained (98.7±0.5)% on a cation exchange resin (Dowex 50W-X8, 100–200 mesh), while (99.8±0.05)%⁹⁹Mo passes through it, due to the non-formation of such complex in the same experimental conditions. The radionuclidic purity of⁹⁹Mo was found to be suitable for the preparation of⁹⁹Mo–^99mTc generators. The retention of⁹⁹Mo on an alumina column as a function of pH was investigated and the best pH range for this purpose was found to be 4.0–4.5.     

Verfeinerung der Kristallstruktur von Te2O3(SO4)

The crystal structure of ditellurium(IV)-trioxide sulfate, Te₂O₃(SO₄)—space group Pmn2₁–C _2v ⁷ ;a=8.879 (2),b=6.936 (2),c=4.646 (4) Å,Z=2—has been determined and refined by least-squares, using three-dimensionalX-ray data (1188 independent reflexions) to a final R-value of 6.3%.The crystal structure comprises puckered tellurium(IV)—oxygen layers in which the tellurium atoms are linked together by three oxygen bridges (Te–O 1.907, 1.945, 2.011 Å). The SO₄ groups are arranged between these layers. Two oxygen atoms of each SO₄ group are bonded to two adjacent tellurium atoms of one layer [Te–O(S) 2.270 Å] and the tellurium atoms show a (3+1) coordination. A third oxygen atom of the SO₄ group is in weak interaction with two adjacent tellurium atoms of the same layer (Te–O 2.603 Å) whereas the fourth oxygen atom has distances of 2.866 Å to two adjacent tellurium atoms of the next layer and effects a very weak interaction between the

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Mit 3 Abbildungen

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Herrn Prof. Dr.R. Kieffer zu seinem 70. Geburtstag gewidmet.     

Analytical separation of antimony(III) from bismuth(III), lead(II), gallium(III), thallium(III), tellurium(IV) and tin(IV) with cyanex 302

A method is proposed for the separation of antimony(III) (100–400 g) from bismuth(III), lead(II), gallium(III), thallium(III), tellurium(IV) and tin(IV) from an aqueous solution of pH 0.5–1.5 using 8×10^–3–1×10^–2 mol dm^–3 cyanex 302 dissolved in toluene as an extractant. The antimony is stripped from the cyanex phase with water and determined spectrophotometrically with iodide. Various experimental parameters are optimized and the probable 13 stoichiometry of the extracted species is evaluated. The method is applicable to the analysis of alloys and pharmaceutical samples. The separation and determination take only 20 min.     

Multicommutation as an environmentally friendly analytical tool in the hydride generation atomic fluorescence determination of tellurium in milk

The aim of this study is to show the advantages of the emerging multicommutation methodology based on the use of solenoid valves for Te determination in milk by hydride generation atomic fluorescence spectrometry (HG-AFS). The delivery of a series of alternating sequential insertions of small volumes of samples and reagents gives rise to new hydrodynamic processes and exciting analytical potentials by controlling the time of flow through the on/off-switched solenoid valves. This drastically reduces the reagent consumption by a factor of 4 and the generation of effluents (590 mL h^–1 instead of 750 mL h^–1 generated by the continuous-mode measurement) and also provides an improvement in the laboratory productivity by an increase of the sample throughput (85 h^–1 compared to 20 h^–1 found in the continuous mode). So, multicommutation is an environmentally and economically sustainable alternative to the methodology based on continuous measurements. The multicommutation-based method developed was applied to tellurium determination in commercially available milk samples; a calibration range of 0.0–0.5 ng mL^–1 and a detection limit of 0.20 ng L^–1 with average relative standard deviation of 2.1% were found. Comparable results were obtained for a series of samples using both continuous and multicommutation HG-AFS modes.     

Rapid determination of telmisartan in pharmaceuticals and serum by the parallel catalytic hydrogen wave method

The polarographic characteristics of telmisartan have been investigated in 0.8 mol L^–1 NH₃.H₂O–NH₄Cl (pH 8.9)–0.01 mol L^–1 H₂O₂ as supporting electrolyte. The results demonstrate that the polarographic reduction wave at ca. –1.30 V in the absence of H₂O₂ is a catalytic hydrogen wave, and the reduction wave enhanced by H₂O₂ is a so-called parallel catalytic hydrogen wave. The analytical sensitivity of the parallel catalytic hydrogen wave is ca. 60 times higher than that of the corresponding catalytic hydrogen wave. Based on the parallel catalytic hydrogen wave a novel method has been developed for determination of telmisartan by linear sweep polarography. The calibration curve is linear in the range 2.0×10^–8–2.0×10^–6 mol L^–1 and the detection limit is 1.0×10^–8 mol L^–1. The precision is excellent with relative standard deviations of 2.6% at a concentration of 1.0×10^–7 mol L^–1 telmisartan. The proposed method has been applied to the direct determination of the telmisartan in capsule forms and biological samples. The proposed method has been proved to be advantageous over existing CZE and MEKC methods in simplicity, rapidity, and reproducibility.     

Direct spectrophotometric method for the determination of cobalt with indane 1,2,3-trionetrioxime in aqueous medium

A simple, sensitive and selective Spectrophotometric method has been developed for the determination of cobalt using indane 1,2,3-trionetrioxime (ITT): The method is based on the colour reaction between ITT and cobalt(II) in sodium acetate-acetic acid buffer (pH 4.5–7.5) medium. The calibration graph for measurement at 320 nm is linear in the range 1.18–23.60g of cobalt per 25 ml, with molar absorptivity of 5.32×10⁴1mol^–1 cm^–1. The effect of interfering ions has been studied and the method was applied to the determination of cobalt in alloys, with good results.     

Spectrophotometric determination of trace amounts of cadmium using Cd(II)-KI-Crystal violet system in the presence of triton X-100 and PVA

A new highly sensitive spectrophotometric method for determination traces of cadmium using Cd-(II)-KI-Crystal Violet system in the presence of Triton X-100-poly(vinyl) alcohol (PVA) mixture has been developed. The apparent molar absorptivity of the system is 1.77 × 10⁵ 1-mol^–1 cm^–1 and its Sandell's sensitivity is 6.35 × 10^–4 g·Cd·cm^2–. Beer's law is obeyed up to 0.32 g·Cd(II)·ml^–1. The method has been applied to determine Cd(II) in waste water, rice and pork meat samples with satisfactory results.     

Adducts of tellurium and organotellurium(IV) chlorides with transition metal chelates of tetradentate schiff bases

Summary Coordinative interaction between tellurium tetrachloride or aryltellurium trichloride and transition metal chelates of tetradentate Schiff bases has yielded bimetallic molecular adducts of the general formula R_nTeCl_4–n · ML [n = 0 or 1, R = Ph,p-MeOC₆H₄ orp-EtOC₆H₄, M = nickel(II) or copper(II) and L^2– dianion of the Schiff bases derived from salicylaldehyde oro-hydroxyacetophenone and ethylenediamine]. The i.r. spectral and magnetic measurements on the complexes in the solid state indicate coordination of the metal chelates to tellurium(IV)via two phenolic oxygens. Planarity about the transition metal ion is thus retained.     

Spectrophotometric determination of palladium(II) with phenylfluorone in the presence of hexadecylpyridinium bromide

Phenylfluorone reacts with palladium(II) in the presence of hexadecylpyridinium bromide to form a water-soluble chelate with an absorption maximum at 630 nm, the absorbance being constant in the pH-range of 9.0–10.2. At this wavelength Beer's law is obeyed up to 7.25 × 10^–5 mol/L palladium(II). The sensitivity is very high and the molar absorptivity is 8.5 × 10⁴ L mol^–1 cm^–1, permitting the determination of palladium(II) at µg level. The ratio of palladium to phenylfluorone in the complex is 1:1. The method has successfully been applied to the determination of palladium in titanium alloys.     

Determination of traces of vanadium with the catalytic maximum wave in differential pulse polarography

Summary A differential pulse-polarographic method has been studied for the determination of vanadium employing the catalytic maximum wave. A well-defined differential pulse polarographic peak is observed in the potential range from –0.2 to –0.7 V vs. SCE for vanadium(V) in 10 mmol 1^–1 NaCl containing 10 mmol 1^–1 acetic acid, 40 mmol 1^–1 pyrocatechol, and 2.5 mmol 1^–1 KBrO₃. The peak current is very large and proportional to the concentration of vanadium(V) between 1×10^–7 and 1×10^–6 mol 1^–1. The relative standard deviation at 0.5 mol l^–1 vanadium(V) was 2.06% (n=7). This method has been successfully applied to the determination of vanadium in standard materials such as pond sediment.

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Spurenbestimmung von Vanadium mit Hilfe der katalytischen Maximumsstufe in der Differential-Puls-Polarographie

Zusammenfassung Ein gut definierter differentialpuls-polarographischer Peak wurde für Vanadium(V) in 10 mmol/l NaCl-Lösung, die 10 mmol/l Essigsäure, 40 mmol/l Brenzcatechin und 2,5 mmol/l KBrO₃ enthielt, beobachtet (Potentialbereich –0,2 bis –0,7 V gegen SCE). Der Peakstrom ist sehr groß und die Vanadiumkonzentration im Bereich von 1×10^–7 bis 1×10^–6 mol/l proportional. Die relative Standardabweichung betrug 2,06% (n=7) bei 0,5 mol/l Vanadium(V). Das Verfahren wurde mit gutem Erfolg zur Vanadiumbestimmung in Standardproben (z.B. Teichsediment) eingesetzt.

     

Enhancing effect of DNA on chemiluminescence from the decomposition of hydrogen peroxide catalyzed by copper(II)

In the absence of any special luminescence reagent, emission of weak chemiluminescence has been observed during the decomposition of hydrogen peroxide catalyzed by copper(II) in basic aqueous solution. The intensity of the chemiluminescence was greatly enhanced by addition of DNA and was strongly dependent on DNA concentration. Based on these phenomena, a flow-injection chemiluminescence method was established for determination of DNA. The chemiluminescence intensity was linear with DNA concentration in the range 2×10^–7–1×10^–5 g L^–1 and the detection limit was 4.1×10^–8 g L^–1 (S/N=3). The relative standard deviation was less than 3.0% for 4×10^–7 g L^–1 DNA (n=11). The proposed method was satisfactorily applied for determination of DNA in synthetic samples. The possible mechanism of the CL reaction is discussed.     

Spectrophotometric determination of manganese with derivatives of 1,3,3-trimethyl-2-[3-(1,3,3-trimethyl-1,3- H-indol-2-ylidene)propenyl]-3 H-indolium

A new, simple, rapid, and sensitive spectrophotometric method has been developed for the determination of manganese in sewage. The method is based on the reaction of manganese with derivatives of 1,3,3-trimethyl-2-[3-(1,3,3-trimethyl-1,3-H-indol-2-ylidene)propenyl]-3H-indolium to form a colored ion associate with a sensitive absorption maximum at 560 nm. The appropriate reaction conditions have been established: pH 8.5–10.0, 1.25–2.3×10^–3 mol L^–1 1-nitroso-2-naphthol, and 1.6–2.4×10^–4 mol L^–1 dye reagent. Beer's law is obeyed for manganese concentrations up to 4.2 mg L^–1. The limit of detection is 0.01 mg L^–1 Mn²⁺; the molar absorptivity of the ion associate was 7.5×10⁴ L mol^–1 cm^–1. The effect of various foreign ions was examined. A reaction mechanism is suggested. The developed procedure was tested for determination of manganese in sewage with satisfactory precision and accuracy.     

Spectrophotometric determination of iron after separation of its 9,10-phenanthrenequinone monoximate on microcrystalline naphthalene

A sensitive and selective spectrophotometric method has been developed for the determination of iron as Fe(II) or Fe(III) using 9,10-phenanthrenequinone monoxime (PQM) as the complexing agent. Fe(II) and Fe(III) react with PQM to form coloured water insoluble complexes which can be adsorbed on microcrystalline naphthalene in the pH ranges 3.7–6.2 and 2.0–8.4, respectively. The solid mass consisting of the metal complex and naphthalene is dissolved in DMF and the metal determined spectrophotometrically by measuring the absorbances Fe(II) at 745 nm and Fe(III) at 425 nm. Beer's law is obeyed over the concentration range 0.5–20.0 g of iron(II) and 20–170.0 g of Fe(III) in 10 ml of DMF solution. The molar absorptivities are 1.333 × 10⁴ 1 · mole^–1 · cm^–1 for Fe(II) and 2.428 × 10³1· mole^–1 · cm^–1 for Fe(III). The precision of determination is better than 1%. The interference of various ions has been studied and the method has been employed for the determination of iron in various standard reference alloys, bears, wines, ferrous gluconate, human hair and environmental samples.     

A New Polarographic Adsorptive Catalytic Wave for the Determination of Trace Tellurium in Smog Dust and Wheat Flour

Linear-sweep polarography of tellurium in sulfuric acid solution containing methylene blue produces a wave at −0.82 V (vs SCE). In a cathodic sweep, the derivative peak current is directly proportional to the concentration of tellurium over the range 4 × 10⁻⁹to 1 × 10⁻⁷g/ml, and the detection limit is 2 × 10⁻⁹g/ml. The polarographic wave is an adsorptive catalytic hydrogen wave. This method has been applied to the determination of trace amounts of tellurium in smog dust and wheat flour, with satisfactory results.     

A method of calibration of the formic acid monomer concentration in the gas phase

Pyrolysis of t-butyl formate, (CH₃)₃C-O-CHO, has been carried out in a carrier gas stream of Ar or N₂ in a temperature range of 200–400°C. Between 200 and 300°C, the pyrolysis yielded an equimolar mixture of HCOOH and (CH₃)₂C=CH₂. The results have been used as a calibration method for determining the concentration of the gas-phase HCOOH monomer without interference from the formation of the formic acid dimer. Using this technique, the gas-phase infrared absorption cross-section of HCOOH at 1105 cm^–1 (peak to valley) for the resolution of 0.5 cm^–1 has been determined to be 6.76×10^–19 cm² molecule^–1.     

Determination of traces of bismuth by quenching of solid-substrate room-temperature phosphorescence from morin-labeled silicon dioxide nano-particles

Silicon dioxide nano-particles, diameter 50 nm, containing morin (morin–SiO₂) have been synthesized by the sol–gel method. They emit strong and stable room-temperature phosphorescence (SS-RTP) on filter paper as substrate, and bismuth can quench the intensity of the SS-RTP. On this basis a new morin–SiO₂ solid-substrate room-temperature phosphorescence-quenching method has been established for determination of traces of bismuth. Reduction of phosphorescence intensity (I_p) is directly proportional to the concentration of bismuth in the working range 0.16–14.4 ag spot^–1 (sample volume 0.40 L spot^–1, corresponding to the concentration range 0.40–36.0 fg mL^–1). The regression equation of the working curve is I_p=14.86+5.279×[Bi³⁺] (ag spot^–1) (n=6, r=0.9982). The detection limit of this method is 0.026 ag spot^–1 (corresponding to a concentration of 6.5×10^–17 g mL^–1).This sensitive, reproducible and accurate method has been used for successful analysis of real samples.     

Voltammetric behaviour of the zirconium-phenylfluorone-hexadecyl pyridinium chloride system and the sensitizing effect of surfactants

The adsorptive voltammetric features of the zirconium-phenylfluorone (PF)-hexadecyl pyridinium chloride (CPC) system has been investigated. A sensitizing effect of the surfactant CPC on the adsorption current of the Zr-PF-CPC system were observed by linear potential sweep voltammetry. A new sensitive method determining Zr traces was established, the detection limit and linear relationship is 5.0×10^–9 mol/l and 7.7×10^–9–1.1×10^–7 mol/l, respectively. This method has been applied to mineral samples.