Determination of Sn(II) and Sn(IV) after mixed micelle-mediated cloud point extraction using alpha-polyoxometalate as a complexing agent by flame atomic absorption spectrometry

The cloud point extraction behavior of Sn(II) and Sn(IV) using alpha-polyoxometalate and mixed surfactants solution was investigated. The mixture of a nonionic surfactant (Triton X-100) and a cationic surfactant (CTAB) was utilized as a suitable micellar medium for preconcentration and extraction of tin complexes. Sn(II) in the presence of Sn(IV) was extracted with alpha-polyoxometalate, 0.3% (w/v) Triton X-100 and 3.5x10(-5) mol L(-1) CTAB at pH 1.2. Whereas the pH value of 3.7 were used for the individual determination of Sn(II) and Sn(IV) and also for total tin determination at the same conditions. Enrichment factors of 100 were obtained for the preconcentration of both metal ions. Under the optimal conditions, linearity was obeyed in the ranges of 55-670 microg L(-1) of Sn(II) and 46-750 microg L(-1) of Sn(IV) ion concentration. The detection limit of the method was also found to be 12.6 microg L(-1) for Sn(IV) and 8.4 microg L(-1) for Sn(II). The relative standard deviation of seven replicate determination of 100 microg L(-1) both metal ions were obtained about 2.4%. The diverse ion effect of some anions and cations on the extraction efficiency of target ions were tested. Finally, the optimized conditions developed were successfully utilized for the determination of each metal ion in various alloy, juice fruit, tape and waste water samples with satisfactory results.     

Polarographic Studies of the Reduction of Sn(II) in Dimethylsulphoxide and its Mixtures with Water and Acetonitrile

Abstract

The polarographic reduction of Sn(II) in DMSO, H₂O-DMSO and AN-DMSO mixtures was characterized as being reversible. When the reduction was carried out in an the process was found to be irreversible and in this case the kinetic parameters were determined by Meites and Israel's method. the effect of DMSO on the reduction of Sn(II) in an shows that the Sn(II) forms six successive complexes with DMSO, whose stability constants were determined by Deford and Hume's method.

The Walden product was determined for the mixtures under study. In AN-DMSO it decreases up to 20 vol.% DMSO, and from there remains approximately constant. In the H₂O-DMSO mixtures the Walden product passes through a broad minimum between 60 and 70 vol.% DMSO. the free energy of transfer in the hydro-organic mixture changes gradually with the increase in DMSO content, whereas in the AN-DMSO mixture this energy increases rapidly in very low DMSO content mixtures.     

Simultaneous Spectrophotometric Determination of Zinc and Nickel in Water Samples by Mean Centering of Ratio Kinetic Profiles

The mean centering of ratio kinetic profiles method was used for the simultaneous determination of binary mixtures of Ni(II) and Zn(II) in water samples, without prior separation steps. The method is based on the difference in the rate of the reaction of Ni(II) and Zn(II) with xylenol orange at pH 5.3. The method allows rapid and accurate determination of Ni(II) and Zn(II). The analytical characteristics of the methods for the simultaneous determination of binary mixtures of Ni(II) and Zn(II) were calculated. The linear range was 0.025‐2.400 μg mL^?1 and 0.025‐2.20 μg mL^?1 for Zn(II) and Ni(II), respectively. Interference effects of common anions and cations were studied, and the method was successfully applied to the simultaneous determination of Zn(II) and Ni(II) in water samples.     

Combined X-ray diffraction and diffuse reflectance analysis of nanocrystalline mixed Sn(II) and Sn(IV) oxide powders

Nanocrystalline mixtures of Sn(II) and Sn(IV) oxide powders, potential gas sensor materials, are synthesized via a simple precipitation route using SnCl(2) as the precursor. Materials are characterized by powder X-ray diffraction, thermogravimetric analysis, UV-visible diffuse reflectance spectroscopy (DRS), and Fourier transform infrared spectroscopy. The ratio of Sn(II)/Sn(IV) in powders precipitated at room temperature, as well as the identity of the primary Sn(II) product (SnO or Sn(6)O(4)(OH)(4)), can be varied by adjusting aging time and washing procedures. The identity of the initial Sn(II) product influences the subsequent phase composition and degree of disorder in the tetragonal SnO(2) phase obtained following sintering in air. Analysis of the DRS absorption edge and long-wavelength (Urbach) absorption tail is used to determine the SnO(2) optical band gap and extent of disorder. SnO(2) obtained by heating the SnO/SnO(2) mixture at 600 or 800 degrees C has a smaller optical band gap and a broader Urbach tail than the analogous sample obtained from heating Sn(6)O(4)(OH)(4), indicating a more disordered material.     

Artificial neural networks for simultaneous spectrophotometric differential kinetic determination of Co(II) and V(IV)

A method for simultaneous analysis of V(IV) and Co(II) has been developed by using artificial neural network (ANN). This method is based on the difference of the chemical reaction rate of V(IV) and Co(II) with Fe(III) in the presence of chromogenic reagent, 1,10-phenanthroline. The reduced product of the reaction, Fe(II), can form a colored complex with 1,10-phenanthroline and make a visible spectrophotometric signal for indirect monitoring of the V(IV) and Co(II) concentrations. Feed forward neural networks have been trained to quantify considered metal ions in mixtures under optimum conditions. The networks were shown to be capable of correlating reduced spectral kinetic data using principal component analysis (PCA) of mixtures with individual metal ion. In this way an ANN containing three layers of nodes was trained. Sigmoidal and linear transfer functions were used in the hidden and output layers, respectively, to facilitate nonlinear calibration. Both V(IV) and Co(II) were analyzed in the concentration range of 0.1-4.0 μg ml⁻¹. The proposed method was also applied satisfactorily to the determination of considered metal ions in several synthetic and water samples.     

Distribution studies of metal ions on arsenophosphates of Sn(IV) and Cr(III) and on amine Sn(II) hexacyanoferrates (II) using radio tracers: Separation of Sr2+−Cs+, Hg2+−Ag+ and Hg2+−Zn2+

Summary Distribution studies of some metal ions have been made on Sn(IV) and Cr(III) arsenophosphates and on some samples of Sn(II) amine hexacyanoferrates(II), using radiotracers. The K_d values of Cs⁺ and Rb⁺ have been followed at varying HNO₃ concentrations also. As a result 3 useful binary separations have been achieved on Sn(IV) and Cr(III) arsenophosphates, such as Sr²⁺–Cs⁺, Hg²⁺–Ag⁺ and Hg²⁺–Zn²⁺.     

The nature of the salt error in the Sn(II)-reduced molybdenum blue reaction for determination of dissolved reactive phosphorus in saline waters

Sn(II) is a well-known reductant used in the formation of phosphomolybdenum blue for the determination of dissolved reactive phosphorus (DRP) in waters because it provides rapid and quantitative reduction. However, in saline waters, this method suffers from a salt error which causes a significant decrease in sensitivity. This phenomenon has never been adequately explained in the literature. The Murphy and Riley method, which uses Sb(III) and ascorbic acid for the reduction step, is preferred for DRP determination in saline waters because it is unaffected by salinity, but it exhibits a sensitivity approximately 30% lower than that when Sn(II) is used as the reductant without Cl⁻ interference. This study investigates the processes causing the salt error and possible ways of minimizing it, so that the benefits of Sn(II) reduction on the molybdenum blue reaction rate and sensitivity may be exploited in the determination of low levels of DRP in marine and estuarine waters. It has been established that the salt error is caused by the formation of Sn(IV) chloro-complexes which compete with the formation of Sn(IV)-substituted phosphomolybdenum blue, forcing the reaction to proceed via the much slower, less favourable process of direct reduction that occurs in methods using organic reductants such as ascorbic acid.     

N → Sn coordination in the complexes of tin halides with pyridine: A comparison between Sn(II) and Sn(IV)

The experimentally well‐known complexation of tin(II) and tin(IV) halides with pyridine (py) leads to structures showing N → Sn coordination. In the present work, the complexes SnX_n·mpy (where X = F, Cl, Br, I; n = 2, 4; m = 1, 2) possessing this kind of coordination were studied using a computational quantum chemical approach. Various aspects in the theoretical picture of these complexes were examined to find similarities and differences in their N → Sn coordination. The aspects included, among others, the physical nature of intermolecular interactions, and their role in establishing the structure and energetic stabilization of the complexes. In this context, the effect of tin valency was inspected in great detail. As proven by several theoretical methods, a largely ionic character with a certain covalent component can be attributed to the studied N → Sn coordination, irrespective of tin valency. All complexes are destabilized by py‐py and three‐body interactions, but the Sn(II) complexes experience it to a greater extent. Marked differences are observed in the structural behavior of N → Sn and SnX_n during complex formation. This affects the energetics of complexation and, in consequence, the penta‐coordinated Sn(IV) center shows a higher propensity to expand its coordination number, compared with the tri‐coordinated Sn(II) center. The present study supplements the experimental characterization of SnX_n·mpy and, in general, it sheds light on the coordination of heteroaromatic nitrogen to tin. The survey of the Cambridge Structural Database revealed that such coordination occurred in a number of crystal structures.     

Syntheses,characterization, and Mossbauer study of Sn(II and Sn(IV) complexes of the cyclopentadienedithiocarboxylate ligand

The preparation and physical characterization of the tetraethylammonium salts of bis(cyclopentadienedithiocarboxylate)stannate(II) and tris(cyclopentadienedithiocarboxylate)stannate(IV) are reported. The coupling constants for the ring protons of the coordinated and uncoordinated ligand indicate that the oxidation state variation of the metal has little effect on the electronic structure of the ligand. The Mössbauer parameters for the Sn(IV) complex (δ = 1.05 ± 0.02 mm/sec with respect to SnO₂, Line width = 1.05 mm/sec) are normal for a pseudo-octahedral complex. The values for the Sn(II) complex are somewhat abnormal for a Sn(II) complex (δ = 0.29 mm/sec, Line width = 1.65 mm/sec) and are interpreted as indicative of metalmetal bonding in the molecular structure.     

Spectrophotometric simultaneous determination of manganese(II) and iron(II) in pharmaceutical by orthogonal signal correction-partial least squares

The simultaneous determination of manganese(II) and iron(II) mixtures by using spectrophotometric methods is a difficult problem in analytical chemistry, due to spectral interferences. By multivariate calibration methods, such as partial least squares (PLS), it is possible to obtain a model adjusted to the concentration values of the mixtures used in the calibration range. Orthogonal signal correction (OSC) is a preprocessing technique used to remove the information unrelated to the target variables based on constrained principal component analysis. OSC is a suitable preprocessing method for partial least squares calibration of mixtures without loss of prediction capacity using spectrophotometric method. In this study, the calibration model is based on absorption spectra in the 450-600 nm range for 21 different mixtures of manganese(II) and iron(II). Calibration matrices were containing 0.05-1.2 and 0.1-2.3 microg mL(-1) Mn(II) and Fe(II), respectively. The RMSEP for manganese(II) and iron(II) with OSC and without OSC were 0.0316, 0.0291, and 0.0907, 0.115, respectively. This procedure allows the simultaneous determination of manganese(II) and iron(II) in synthetic and real matrix samples with good reliability of the determination.     

Supramolecular tetrads containing Sn(IV) porphyrin, Ru(II) porphyrin, and expanded porphyrins assembled using complementary metal-ligand interactions

Two examples of supramolecular tetrads containing Sn(IV) porphyrin, expanded thiaporphyrins such as sapphyrin and rubyrin, and Ru(II) porphyrin assembled using non-interfering cooperative tin(IV)-oxygen and ruthenium(II)-nitrogen coordination properties are described. These are the first examples in which the expanded porphyrins are used as axial ligands. The tetrads were prepared by adopting one step as well as stepwise approaches. In a one pot approach, the mono meso-pyridyl dihydroxy Sn(IV) porphyrin, meso-hydroxyphenyl expanded thiaporphyrin, and Ru(II) porphyrin were reacted in benzene under refluxing conditions followed by column chromatographic purification on alumina to afford tetrads. In a stepwise approach, the axial bonding type of triads containing Sn(IV)porphyrin as central unit and expanded thiaporphyrins as axial ligands were synthesized first by reacting meso-pyridyl dihydroxy Sn(IV) porphyrin with meso-hydroxyphenyl expanded thiaporphyrin in benzene at refluxing temperature. In the next step, the triads were reacted with Ru(II) porphyrin under mild reaction conditions to afford tetrads in decent yields. Both methods worked efficiently and produced stable, soluble tetrads in decent yields. One-dimensional (1D) and two-dimensional (2D) NMR techniques were used to confirm the identity of these novel tetrads. Absorption and electrochemical studies indicated that the components in tetrads interact weakly and retain their individual characteristic features. The steady state photophysical studies revealed that the quantum yield of Sn(IV) porphyrin in tetrads was reduced significantly because of non-radiative decay pathways operating in these systems.     

A novel salicylate-selective electrode based on a Sn(IV) complex of salicylal-imino acid Schiff base

A novel poly(vinyl chloride) membrane electrode with high selectivity toward salicylate (Sal^–), based on the use of the salicylal-imino acid Schiff base dibenyl complex of Sn(IV) [Sn(IV)-SIADBen] as ionophore is described. The influence of lipophilic charged additives on the performance of the electrode was studied. The results suggested that Sn(IV)-SIADBen according to a positively-charged carrier mechanism. The influence of several other variables was investigated in order to optimize the potentiometric response and selectivity of the electrode. The electrode based on Sn(IV)-SIADBen, with 30.44 wt% PVC, 64.55 wt% plasticizer [dioctyl phthalate (DOP)], 3.81 wt% ionophore, and 1.2 wt% anionic additive exhibited a linear response for the Sal^– ion over the concentration range 1.0×10^–1 to 2.5×10^–6 mol l^–1, and displayed an anti-Hofmeister selectivity sequence as follows: salicylate perchlorate > thiocyanate > benzoate > iodide > nitrate > chloride > nitrite acetate > citrate > sulfate. UV-Visible absorption spectra were used to examine the specific interaction of salicylate with the ionophore. The electrode was applied to clinical medical analysis, and the results obtained were consistent with those obtained by conventional methods.     

H-point standard addition method for simultaneous determination of Fe(II), Co(II) and Cu(II) in micellar media with simultaneous addition of three analytes

H-point standard addition method, HPSAM, with simultaneous addition of three analytes is proposed for the resolution of ternary mixtures. It is a modification of the previously described H-point standard addition method that permits the resolution of three species from a unique calibration set by making the simultaneous addition of the three analytes. The method calculates the analyte concentration from spectral data at two wavelengths where the two species selected as interferents present the same absorbance relationship. These wavelength pairs are easily found, and can be selected to give the most precise results. Diethyldithiocarbomate (DDC) in a cationic micellar solution of cetyltrimethylammonium bromide (CTAB) was used for determination of Fe(II), Co(II) and Cu(II) at pH 5.50. The results showed that simultaneous determination of Fe(II), Co(II) and Cu(II) could be preformed in the range of 0.0–6.0, 0.0–8.0 and 0.0–12.0 μg ml⁻¹, respectively. The proposed method was successfully applied to the simultaneous determination of Fe(II), Co(II) and Cu(II) in several synthetic mixtures containing different concentration of Fe(II), Co(II) and Cu(II).     

Extraction of Ag(I), Cd(II), In(III), Sn(II), Sn(IV), Sb(III), and U(VI) from aqueous solutions by ketone solutions using single-step batch and continuous SISAK methods1,2

The extraction properties of Ag(I), Cd(II), In(III), Sn(II), Sn(IV), Sb(III), and U(VI) from aqueous KI/H₂SO₄ solution into a mixture of 4-methyl-2-pentanone (methyl isobutyl ketone, MIBK) and cyclohexanone (CHO) were studied. Both single-step batch and SISAK² methods were used. The oxidation of Sn(II) to Sn(IV) by iodine and complexation of Sn(IV) by 2,3-dimercapto-propanol-1 (BAL) were also investigated. A method for rapid and continuous separation of indium from tin was developed for investigation of short-lived indium fission products.     

Simultaneous determination of cobalt(III)-copper(II) and cobalt(III)-nickel(II) mixtures by differential kinetic methods

A procedure is reported for the simultaneous determination of binary mixtures of cobalt(III)-copper(II) and cobalt(III)-nickel(II) by differential kinetic methods based on complex formation reactions with 3-(1H-1,2,4-triazolyl-3-azo)-2,6-diaminotoluene. The single-point method is used in both cases. The simultaneous determination of Co-Cu and Co-Ni is possible in the concentration range from 10/1 to 1/1. The interference caused by various ions is also studied. The method has been used to determine cobalt-copper and cobalt-nickel mixtures in synthetic samples, hydrofining catalysts and low alloy steels.     

Simultaneous spectrophotometric determination of cobalt and nickel by partial least square regression in micellar media

Diphenycarbazone has been used for the simultaneous determination of cobalt and nickel by partial least square regression method. DPC complexes of cobalt and nickel at pH 7-10 are of pink color, which are soluble in TX-100 micellar media. A partial least square multivariate calibration method for the analysis of binary mixtures of cobalt and nickel was developed. The total relative standard error for applying the PLS method was calculated. The accuracy and reproducibility of the determination method for various known amounts of Co(II) and Ni(II) in their binary mixtures were tested. The effects of diverse ions on the determination of cobalt and nickel to investigate the selectivity of the method were also studied. The proposed method was applied to the synthetic binary mixtures, alloys and pharmaceutical samples.     

Photolysis of oxygen saturated ethers in the presence of Sn(Ⅱ) or Cu(Ⅱ) salts

Photolysis of diethyl ether-oxygen charge transfer complex in the presence of Sn(Ⅱ)or Cu(Ⅱ)salts gave higher yields of the oxidation products,ethyl acetate,acetaldehyde,ethanol,ethyl formate and methanol compared with those without the salts.In addition,the photolysis of an oxygen saturated te-trahydrofuran(THF)or dibutyl ether solution gave y-butyro-lactone or butanol and butyl butyrate as major products with small amounts of undetermined compounds,respectively.Their yields were also affected by the addition of Cu(Ⅱ)or Sn(Ⅱ)salts.     

Potentiometric membrane sensor based on 6-(4-nitrophenyl)-2,4-diphenyl-3,5-diaza-bicyclo[3.1.0]hex-2-ene for detection of Sn(II) in real samples

A Sn²⁺ ion-selective electrode which was prepared with a polymeric membrane based on 6-(4-nitrophenyl)-2,4-diphenyl-3,5-diaza-bicyclo[3.1.0]hex-2-ene (NDDBH) as a ionophore. Effects of experimental parameters such as membrane composition, nature and amount of plasticizer, the amount of additive and concentration of internal solution on the potential response of Sn²⁺ sensor were investigated. The electrode exhibited a Nernstian slope of 28.8 ± 1.1 mV/decade of Sn²⁺ over a concentration range of 1.0 × 10⁻⁵ to 1.0 × 10⁻¹ M of Sn²⁺ in an acidic solution (pH 1). The limit of detection was 4.0 × 10⁻⁶ M. The results show that this electrode can be used in ethanol media until 20% (v/v) concentration without interference. It can be used for more than 6 weeks without any considerable divergence in the potentials. The proposed membrane electrode revealed very good selectivity for Sn(II) ions over a wide variety of other cations and could be used in acidic media. The standard electrode potentials were determined at different temperatures and used to calculate the isothermal coefficient of the electrode. The stability constant (log K_s) of the Sn(II)-ionophore complex was determined at 25 °C by potentiometric titration in mixed aqueous solution. It was used as indicator electrode in potentiometric determination of Sn(II) ion in real samples.     

Titrimetric determination of U(iv) alone and in mixtures with V(IV), Mn(II), Ce(III) and Fe(II)

Summary A rapid and accurate method is described for the potentiometric determination of uranium(IV) with permanganate at room temperature using trace amounts of ortho-phosphoric acid as a catalyst. The procedure has been extended for the differential potentiometric determination of mixtures with vanadium, manganese or cerium. The methods are easy, non-time consuming and free from interference by a large number of foreign ions. Conditions are also developed for the differential photometric determination of uranium and iron in mixtures.Based on these procedures, a differential titrimetric procedure has been developed for determination of iron(III), vanadium(V), chromium(VI) and manganese(VII) [or cerium(IV)] in a single solution at room temperature. This procedure has also been tested on Bureau of Standard samples.

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Titrimetrische Bestimmung von U(IV) allein und in Mischungen mit V(IV), Mn(II), Ce(III) und Fe(II)Anwendung auf die Analyse von Stählen und Legierungen

Zusammenfassung Eine schnelle und genaue Methode wird beschrieben zur potentiometrischen Bestimmung von Uran(IV) mit Permanganat bei Raumtemperatur unter Verwendung von Spuren Orthophosphorsäure als Katalysator. Das Verfahren wurde auf die differentialpotentiometrische Bestimmung im Gemisch mit V, Mn und Ce ausgedehnt. Die rasch und einfach ausführbare Methode wird durch zahlreiche Fremdionen nicht gestört. Eine differentialphotometrische Bestimmung von U(IV) und Fe(II) im Gemisch wird ebenfalls angegeben, außerdem eine differentialtitrimetrische Bestimmung von Fe(III), V(V), Cr(VI), Mn(VII) [oder Ce(IV)] in einer Lösung. Anwendungsbeispiele für Stähle und Legierungen werden beschrieben.

     

Synthesis and ion exchange behaviour of polyaniline Sn(IV) arsenophosphate: a polymeric inorganic ion exchanger

Incorporation of a polymer material into an inorganic ion exchanger provides a class of hybrid ion exchangers with a good ion exchange capacity, high stability, reproducibility and selectivity for heavy metals. Such a type of ion exchanger ‘polyaniline Sn(IV) arsenophosphate’ has been synthesized by mixing polyaniline into inorganic material. This material is characterized using X-ray, IR, TGA studies in addition to ion exchange capacity, pH-titration, elution and distribution behaviour. On the basis of distribution studies, the material has been found to be highly selective for Pb(II). Kinetic study of exchange for the metal ions has been performed and some physical parameters such as self diffusion coefficient D₀, energy E_a and entropy ΔS* of activation have been determined.