Application of a ternary complex of tungsten(VI) with 4-nitrocatechol and thiazolyl blue for extraction-spectrophotometric determination of tungsten

A new ternary ion-association complex of tungsten(VI), 4-nitrocatechol (NC), and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (Thiazolyl Blue, MTT) was obtained and studied using an extraction-spectrophotometric method. The optimum pH, reagent concentrations, and extraction time were determined. The composition of the complex was found to be W(VI): NC: MTT = 1: 2: 2. The extraction process was investigated quantitatively and the key constants were calculated. The molar absorptivity of the chloroform extract at λ_max = 415 nm was 2.8 × 10⁴ dm³ mol⁻¹ cm⁻¹, and the Beer’s law was obeyed up to 8.8 μg cm⁻³ tungsten(IV). The limit of detection and limit of quantification were calculated to be 0.27 μg cm⁻³ and 0.92 μg cm⁻³, respectively. The effect of foreign ions and reagents was studied and a competitive method for determination of tungsten in products from ferrous metallurgy was developed. The residual standard deviation and the relative error were 0.53 % and 0.2 %, respectively.     

Spectrophotometric determination of cationic surfactants by formation of ternary complexes with Fe(III) and chrome azurol

An extraction-free spectrophotometric method for the determination of cationic surfactants, such as cetylpyridinium chloride, cetyltrimethylammonium bromide and zephiramine is proposed, which is based on the formation of ternary complexes with Fe(III) and chrome azurol S. The molar ratio of the complex is 2:1:1 (Fe(III):chrome azurol S: cationic surfactant). The method is simple, rapid and sensitive, giving an apparent molar absorptivity of 4.5×10⁴ L·mol^?1-cm^?1 and a linear range of 0.1–6.0 μmol/L cationic surfactants. The total cationic surfactant content can be determined directly in aqueous solutions by measuring the absorbance at 680 nm (pH 5.8). The method has been successfully applied to water samples.     

Catalytic spectrophotometric determination of molybdenum (VI) with the hydrazine-metanil yellow system

A new catalytic Spectrophotometric method for the determination of trace amounts of molybdenum (VI) has been proposed. The method is based on the catalytic effect of Mo(VI) on the reduction of metanil yellow by hydrazine dihydrochloride. Under experiment condition, the linear range of determination is 20–160 ng/mL for molybdenum and the detection limit is 11.2ng/mL. The method has been used to determine trace molybdenum in bean samples with the recovery of 96.0–99.0%, with relative standard deviations of 1.50–2.53%.     

Spectrophotometric determination of trace amounts of uranium(VI) in water samples after mixed micelle-mediated extraction

A cloud point extraction process using mixed micelle of the cationic surfactant CTAB and non-ionic surfactant TritonX-114 to extract uranium(VI) from aqueous solutions was investigated. The method is based on the color reaction of uranium with pyrocatechol violet in the presence of potassium iodide in hexamethylenetetramine buffer media and mixed micelle-mediated extraction of complex. The optimal extraction and reaction conditions (e.g. surfactant concentration, reagent concentration, effect of time) were studied and the analytical characteristics of the method (e.g. limit of detection, linear range, preconcentration, and improvement factors) were obtained. Linearity was obeyed in the range of 0.20-10.00 ng mL⁻¹ of uranium(VI) ion and the detection limit of the method is 0.06 ng mL⁻¹. The interference effect of some anions and cations was also tested. The method was applied to the determination of uranium(VI) in tap water, waste-water and well water samples.     

Chemically selective membrane optode for Cr(VI) determination in aqueous samples

A methodology for simultaneous preconcentration and determination of Cr(VI) from aqueous samples was developed using a membrane optode formed by physical inclusion of a Cr(VI) selective chromophore 1,5-diphenylcarbazide (DPC) into a plasticized cellulose triacetate matrix. The inclusion of an anion exchanger (Aliquat-336) was found to be effective for immobilization of both DPC and Cr(VI)-DPC complex in the optode matrix itself. The proportionality in intensity of the magenta color on the optodes loaded with varying amounts of Cr(VI) suggests its potential applications for screening of Cr(VI) in aqueous samples by visual colorimetry. On loading high amounts of Cr(VI) in the membrane optode, its color changes from magenta to yellow, which indicates the possibility of using it as a threshold detector for Cr(VI). The membrane optode was optimized in terms of obtaining maximum preconcentration efficiency for Cr(VI) and subsequent stable optical response proportional to the amount of Cr(VI) in the membrane optode sample. The membrane optodes were tested for Cr(VI) determination in tap water and seawater samples. Using this optode, Cr(VI) even at levels of 13.6 ppb could be quantitatively detected. The optodes developed in the present work were found to be stable, cost effective, easy to prepare and efficient for direct preconcentration and determination of Cr(VI) in a variety of aqueous samples using spectrophotometry. However, this membrane optode is for one time use only as the reaction of Cr(VI) with DPC is irreversible.     

2-(2-喹啉偶氮)-5-二甲氨基苯酚光度法测定铀的研究

铀的测定一般采用铀试剂-Ⅲ或5-Br-PADAP光度法。2-喹啉偶氮类试剂已用于一些金属离子的测定,由于其共轭体系大,比吡啶偶氮类试剂具有更高的灵敏度。我们合成了2-(2-喹啉偶氮)-5-二甲氨基苯酚(QADMAP),产品经IR,MS及^1H NMR表征(谱图略)。研究其和铀的显色反应,建立了一种测定矿石中铀的方法。     

Catalytic adsorptive stripping determination of trace chromium (VI) at the bismuth film electrode

A sensitive adsorptive stripping voltammetric protocol at a bismuth-coated glassy-carbon electrode for trace measurements of chromium (VI) in the presence of diethylenetriammine pentaacetic acid (DTPA) is described. The new protocol is based on accumulation of the Cr-DTPA complex at a preplated bismuth film electrode held at −0.80 V, followed by a negatively-going square-wave voltammetric waveform. Factors influencing the stripping performance including the film preparation, solution pH, DTPA and nitrate concentrations, deposition potential and deposition time, have been optimized. The resulting performance compares well with that observed for analogous measurements at mercury film electrodes. A preconcentration time of 7 min results in a detection limit of 0.3 nM Cr(VI) and after 2 min a relative standard deviation at 20 nM of 5.1% (n = 25). Applicability to river water samples is demonstrated. The attractive behavior of the new “mercury-free” chromium sensor holds great promise for on-site environmental and industrial monitoring of chromium (VI). Preliminary data in this direction using bismuth-coated screen-printed electrodes are encouraging.     

Ternary complexes in the spectrophotometric determination of trace amounts of silver(I) and cadmium(II)

The reaction of silver(I) and cadmium(II) with 1,10-phenanthroline (PHEN) and Eosin (2,4,5,7-tetrabromofluorescein) gives coloured association complexes. The solution spectra of the mixed-ligand complexes are characterised by high intensity (∈ ≈ 10⁴) metal-to-ligand charge-transfer bands at 540–555nm. The optimum conditions for the spectrophotometric determination of Ag(I) or Cd(II) have been established. A simple, sensitive and selective method was proposed for the determination of traces of the metal ions either in aqueous or organic media. In the presence of EDTA only aluminium and cyanide interfere.     

A study of the spectrophotometric method for the determination of uranium(VI) in trialkylamine/kerosene extracts using 1-(2-pyridylazo)-2-naphthol

Summary The Spectrophotometric method for the determination of uranium(VI) in trialkylamine extracts using 1-(2-pyridylazo)-2-naphthol (PAN) as a colorimetric reagent has been examined. The Job and Mole Ratio methods suggest that the coloured product is a 11 complex of uranium and PAN. The method can be applied to cover the concentration range 0 to 5 g uranium per litre of extract. Sulphate interference is eliminated in the method by removal with calcium ions before colour development. Interferences from other ions likely to be present in the aqueous liquor appear to arise largely from inhibition of the uranium partition into the amine phase.

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Untersuchung der spektralphotometrischen Uran(VI)-Bestimmung in Trialkylamin/Kerosin-Extrakten mit Hilfe von 1-(2-Pyridylazo)-2-naphthol

Zusammenfassung Das Verfahren, bei dem ein Uran-PAN-Komplex der Zusammensetzung 11 gebildet wird, kann für einen Konzentrationsbereich von 0 bis 5 g U pro l Extrakt eingesetzt werden. Eine Störung durch Sulfat wird durch dessen Entfernung mit Calciumionen vor der Farbentwicklung verhindert. Störungen durch andere Ionen werden hauptsächlich durch Beeinflussung der Uranextraktion hervorgerufen.

     

Solvent extraction and spectrophotometric determination of uranium (VI)

Summary Solvent extraction of uranium-sodium diethyldithiocarbamate with ethylmethyl ketone and separation from titanium, zirconium, thorium, lanthanum and cerium has been described. It has been found that 11.75 to 47.00 mg of uranium can be extracted from a binary mixture containing 4.78 to 19.04 mg of titanium, 9.12 to 36.48 mg of zirconium, 116.0 to 460.0 mg of thorium, 6.95 to 27.8 mg of lanthanum or 7.06 to 28.24 mg of cerium at pH 3.0. The pH range between which the separations may be carried out successfully is 2.0 to 3.5. The following cations interfere in the separations: Cu^II, Fe^III, Co^II, Bi^III, Ni^II, Cr^VI, Te^IV, Se^IV, Ag^I, Hg^II, As^III, Sn^IV, Pb^IV, Cd^II, Mo^VI, Mn^II, V^V, Zn^II, In^III, Tl^I, W^VI, Os^VIII and Nb^V.

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Zusammenfassung Uran kann durch Extraktion als Diäthyldithiocarbamidat mit Methyläthylketon von Ti, Zr, Th, La oder Ce getrennt werden. Der günstigste pH-Bereich liegt zwischen 2,0 und 3,5. Die Trennungen wurden mit folgenden Mengen durchgeführt: U (11,75–47,00 mg); Ti (4,78 bis 19,04 mg), Zr (9,12–36,48 mg) Th (116,0–460,0 mg), La (6,95–27,8 mg), Ce (7,06–28,24 mg). Folgende Ionen verursachen Störungen: Cu^II, Fe^III, Co^II, Bi^III, Ni^II, Cr^VI, Te^IV, Se^IV, Ag^I, Hg^II, As^III, Sn^IV, Pb^IV, Cd^II, Mo^VI, Mn^II, V^VI, Zn^II, In^III, Tl^I, W^VI, Os^VIII sowie Nb^V.

     

溶液中Fe(VI)向Fe(IV)转化反应的分光光度法跟踪

Different concentrations of ferrate(VI) with ClO^- and without ClO^- in alkaline solution were traced by visible spectrometry, and the conversion reaction of Fe(VI) to Fe(IV) was found to exist, in condition that c was ≥ 6 mol·L^-1. ClO^- would slow down the decomposition reaction rate of Ferrate(VI) and increase the product concentration of Fe(IV) in the system.     

Simultaneous determination of molybdenum(VI) and tungsten(VI) and its application in elemental analysis of polyoxometalates

Spectrophotometric determination of molybdenum(VI) and tungsten(VI) with application of Artificial Neural Networks is proposed and it was applied for elemental analysis of solid polyoxometalates. Better results in comparison with previously those achieved by previous published method were demonstrated. MALDI-TOF Mass Spectrometry was tested for possible determination of molecular weight of polyoxometalates utilizing different matrices. Phenomena observed during desorption-ionisation processes are discussed. LDI-TOF MS was found to be suitable for the determination of Mo:W ratio in polyoxometalates as a rapid screening method to follow synthetic procedure.     

A new experimental approach for liquid-liquid extractive spectrophotometric determination of chromium(VI) in tannery wastewater and alloy samples

In this research work, a new approach is developed for the extractive determination of chromium. The principle of this approach is based on the complexation reaction between 4-(4?-chlorobenzylideneimino)-3-methyl-5-mercapto-1,2,4-triazole (CBIMMT) in dichloromethane as a complexing reagent and chromium(III) in presence of potassium iodide to form a yellow coloured complex at room temperature. The 1:2:2 [Cr(III)-CBIMMT-iodide] ternary complex was quantitatively extracted in dichloromethane from 2.5 mol L^?1 of hydrochloric acid medium which showed maximum absorption intensity at λ_max 411 nm and was stable for more than 72 h. The values of molar absorption coefficient and Sandell’s sensitivity of the complex were found to be 0.7019 × 10⁴ L mol^?1 cm^?1 and 0.00748 µg cm^?2, respectively. The system adheres to Beer’s law from 1.5 to 6.0 µg mL^?1; however, Ringbom’s plot suggests optimal concentration range was 1.8–5.8 µg mL^?1. The limit of detection and limit of quantification of the approach is 0.26 and 0.79 µg mL^?1. This approach was successfully used for the determination of chromium from wastewater effluents from the tannery industries (Kolhapur, MS, India), alloy samples and for separation of it from synthetic mixtures. The present experimental approach is apparently much simpler than the conventional method comprising multistep processes.     

A sensitive spectrophotometric method for the determination of trace amounts of uranium (VI) using o-hydroxypropiophenone isonicotinoyl hydrazone

The reaction between uranium (VI) and o-hydroxypropiophenone isonicotinoyl hydrazone (OHPINH) has been investigated in HCl-sodium acetate buffers and a highly sensitive and simple procedure for the determination of uranium (VI) is suggested. The yellow colored complex showed maximum absorption at 380 nm in buffer solutions of pH 3. Beer's law is obeyed in the range of 0.47–17 g ml^–1. The molar absorptivity and Sandell sensitivity are found to be 1.15×10⁴ dm³ mol^–1 cm^–1 and 0.02 g cm^–2, respectively. The composition of the complex is found to be 11 between metal and reagent.     

Dioxomolybdenum(VI) and dioxotungsten(VI) complexes: efficient catalytic activity for crosslinking reaction in ethylene‐vinyl acetate copolymer/alkoxysilane composites

The catalytic performances of several bis(acetylacetonato)metal complexes [Cu(acac)₂, Zn(acac)₂, TiO(acac)₂, VO(acac)₂, MoO₂(acac)₂, and WO₂(acac)₂] were investigated for the crosslinking reaction via transesterifications in the ethylene‐vinyl acetate copolymer/tetraethoxysilane (EVA/TEOS) composite system by means of dynamic attenuated total reflectance Fourier transform infrared, solvent swelling, and solid‐state ²⁹Si cross polarization/magic angle spinning nuclear magnetic resonance techniques. Results of the kinetic examination revealed that MoO₂(acac)₂ and WO₂(acac)₂ exhibited a higher catalytic activity than di‐n‐butyltin(IV) oxide, which is a catalyst most commonly used for the transesterification process in polymer system, but has a toxic effect on the environmental health. And furthermore, the crosslink density and final siloxane network structure of crosslinked EVA/TEOS composites are found to be greatly correlated with the catalyst used. On the basis of the S_N2‐Si pathway, a plausible catalytic mechanism of MoO₂(acac)₂ and WO₂(acac)₂ was proposed for the crosslinking reaction via transesterifications of the vinyl acetate moieties in EVA backbone with the ethoxysilane groups in one TEOS molecule. The findings in this study may fill the blank in the high performance and environmentally friendly catalyst in the field of the crosslinking reactions in polymer system and provide useful clue for other transesterifications. Copyright © 2015 John Wiley & Sons, Ltd.     

Rapid determination of chromium(VI) in electroplating waste water by use of a spectrophotometric flow injection system

A new rapid and sensitive FI method is reported for spectrophotometric determination of trace chromium(VI) in electroplating waste water. The method is based on the reaction of Cr(VI) with sodium diphenylamine sulfonate (DPH) in acidic medium to form a purple complex (lambda(max) = 550 nm). Under the optimized conditions, the calibration curve is linear in the range 0.04-3.8 microg ml(-1) at a sampling rate of 30 h(-1). The detection limit of the method is 0.0217 microg ml(-1), and the relative standard deviation is 1.1% for eight determinations of 2 microg ml(-1) Cr(VI). The proposed method was applied to the determination of chromium in electroplating waste water with satisfactory results.     

Application of specific ion interaction theory and parabolic models for the molybdenum(VI) and tungsten(VI) complexes with NTA and IDA at different ionic strengths

The interaction of nitrilotriacetic acid (NTA) and iminodiacetic acid (IDA) with tungsten(VI) (pH 7.5) and molybdenum(VI) (pH 6.00) has been studied in aqueous solutions at 25 ℃, and different ionic strengths (0.1 相似文献