Utilization of an Hg(2+)-sensitive membrane-electrode in the complexometric determination of Bi(3+), Fe(3+) and Cr(3+)

The paper reports the results obtained in the complexometric determination of Bi(3+), Fe(3+) and Cr(3+) by using an Hg(2+)-sensitive membrane-electrode for the end-point indication. The determination of Bi(3+) and Fe(3+) is performed after addition of mercuric complexonate from which these cations release Hg(2+) by means of which the electrode senses the equivalence point. In the case of Cr(3+) an excess of complexone is added and the surplus is titrated with a standard solution of Hg(2+) in the presence of the Hg(2+)-sensitive membrane-electrode.     

Solvent sublation and spectrometric determination of iron(II) and total iron using 3-(2-pyridyl)-5,6-bis(4-phenylsulfonic acid)-1,2,4-triazine and tetrabutylammonium bromide.

Solvent sublation has been studied for the separation and determination of trace iron(II) in various kinds of water samples. A strongly magenta-colored anionic [Fe(FZ)3](4-) complex was formed at pH 5.0 upon adding 3-(2-pyridyl)-5,6-bis(4-phenylsulfonic acid)-1,2,4-triazine (ferrozine, FZ) to the sample solution. Tetrabutylammonium bromide (TBAB) was added in the solution to form the (TBA)4[Fe(FZ)3)] ion pair, and an oleic acid (HOL) surfactant was added. Then, the (TBA)4[Fe(FZ)3] ion pairs were floated by vigorous shaking in the flotation cell and extracted into methyl isobutyl ketone (MIBK) on the surface of the aqueous solution. The iron collected in the MIBK layer was measured directly by spectrophotometry and/or flame atomic-absorption spectrophotometry. Different experimental variables that may affect the sublation efficiency were thoroughly investigated. The molar absorptivity of the (TBA)4[Fe(FZ)3] ion pair was 2.8 x 10(4) l mol(-1) cm(-1) in the aqueous layer. Beer's law held up to 1.0 mg L(-1) Fe(II) in the aqueous as well as in the organic layers. The adopted solvent sublation method was successfully applied for the determination of Fe(II) in natural water samples with a preconcentration factor of 200. The application was extended to determine iron in pharmaceutical samples.     

Chemiluminescence determination of barbituric acid using Ru(phen)(3)(2+)-Ce(IV) system

A chemiluminescence (CL) method for the determination of barbituric acid (BA) was proposed, which is based on the enhancement of BA to the CL intensity of Tris-(1,10-phenanthroline)ruthenium(II) (Ru(phen)₃²⁺)-cerium(IV) (Ce(IV)) system. The concentration of BA is proportional to the CL intensity in the range of 5.0×10⁻³-2.0 μg ml⁻¹. The detection limit is 6.9×10⁻⁴ μg ml⁻¹. The relative standard deviation (R.S.D.) of determining 11 samples containing 0.20 μg ml⁻¹ BA is 3.2%. This CL method has been successfully applied to the determination of BA in the synthetic samples. The mechanism of CL reaction was studied.     

Polarographic determination of iron(II) and iron(III) complexes with edta

The iron(II) and iron(III) complexes with EDTA can be determined separately and in mixtures in acetate-buffered medium at pH 4.0. The E_{$\text{1}\text{2}$}values are in the range ?0.105 to ?0.112 V vs. SCE. Linear calibration plots are obtained over the range 0–1.0 mM for each oxidation state. A sample-handling procedure for avoiding oxidation of iron(II) species is described. It is shown that the acetate buffer system does not affect the stability of the iron-EDTA complexes.     

Fe^3＋与S^2-反应再探究

Fe3 与S2-的反应一直是中学化学的敏感问题。若乱说,会谬种流传;若回避,会束之高阁,不利于化学教育的发展。1回顾回顾过去,大概有4种情型:笼统型?讨论型?否定型?回避型。1.1笼统型认为Fe3 与S2-反应是2Fe3 S2-=2Fe2 S↓,未考虑是否与滴加顺序有关。(1)梁大鹏主编的《高考三人     

Polarographic behaviour of 3-(2′-thiazolylazo)-2, 6-diaminopyridine using DC and differential pulse polarography

The polarographic behaviour of 3-(2-thiazolylazo)-2,6-diaminopyridine (2,6-TADAP) has been studied in aqueous buffer solutions and aqueous-ethanol mixtures of different pH's using DC and DP polarographic methods. The reduction of the azo linkage takes place via two electrons in both aqueous and aqueous-ethanol mixtures. The linear relationship between the current and 2,6-TADAP concentration allowed the polarographic determination of 2,6-TADAP over a wide concentration range. The values of the adsorption parameters in the presence of both Triton X-100 (non-ionic) and a new non-ionic surfactant, nonylphenol polyoxypropylene polyoxyethylene (NPE 1800) have been computed. The kinetic parameters of the electrode reaction have been calculated.On leave from An-Najah National University, Nablus, West Bank, Via Israel.     

Polarographic determination of uranyl ions in a hydrolyzed system

Summary A method for the polarographic determination of non-hydrolyzed uranyl ions in the presence of their hydroxo complexes was developed. Neither hydroxo complex reduction, nor catalytic reduction of nitrate, nor UO ₂ ⁺ disproportionation (negligible at pH values>1) interfere with this determination. A 0.1 M NaNO₃ or NaClO₄ solution is used as the supporting electrolyte. For determination of the total uranium concentration in a hydrolyzed solution, the presence of the corresponding acid in a concentration of about 5·10^–2 M is necessary in addition to the sodium salt mentioned above.

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Zusammenfassung Es wird eine Methode beschrieben zur polarographischen Bestimmung nicht-hydrolysierter Uranylionen in Gegenwart ihrer Hydroxokomplexe. Das Verfahren wird durch Reduktion der Hydroxokomplexe, katalytische Nitratreduktion oder Disproportionierung des UO ₂ ⁺ (die bei pH>1 vernachlässigbar ist) nicht gestört. 0,1 m NaNO₃ oder NaClO₄ dienen als Leitsalzlösung. Zur Bestimmung des Gesamturans in einer hydrolysierten Lösung muß noch die entsprechende Säure (5 · 10^–2 M) zugesetzt werden.

     

Redox thermodynamics of the Fe(3+)/Fe(2+) couple in horseradish peroxidase and its cyanide complex.

The thermodynamics of Fe3+ to Fe2+ reduction for the five-coordinate high-spin native form of horseradish peroxidase and for its six-coordinate low-spin cyanide adduct have been determined from variable-temperature UV-vis spectroelectrochemical experiments. In both cases, the DeltaH degrees 'rc and DeltaS degrees 'rc values are positive. Hence, the negative reduction potentials turn out to be the result of two opposing and partially compensating contributions: a large enthalpic term, which is the determinant of the negative E degrees ' values for both species, and a smaller, yet relevant, entropic contribution. The decrease in E degrees ' of the Fe3+/Fe2+ couple on cyanide binding turns out to be a fully entropic effect, unequivocally demonstrating the importance of entropic effects in determining the E degrees ' values of redox metal centers.     

Fluorescent graphene oxide logic gates for discrimination of iron (3+) and iron (2+) in living cells by imaging

A combinational logic gate based on fluorescent graphene oxide has been reported to discriminate Fe(3+), Fe(2+) and their mixture in living cells by fluorescence imaging.     

Spectrophotometric determination of chloride in PtAl(2)O(3)/SiO(2) catalysts with Hg(SCN)(2)Fe(3+) reagent

A method is described for the determination of chloride in PtAl(2)O(3)/SiO(2) catalysts, based on its extraction with alkali followed by reaction with Hg(SCN)(2)Fe(3+) reagent and spectrophotometric measurement at 460 nm. Beer's law is obeyed in the concentration range 5-75 mug of chloride in 25 ml of aqueous solution. The molar absorptivity is 1.99 x 10(3) l.mole(-1).cm(-1). The rapid colour development, excellent reproducibility and absence of interference from the species most often present in the catalysts are the advantages of the method.     

The calculation of the thermodynamic equilibrium in Fe3+/MoO 4 2− /H+(OH−)/H2O system and determination of reasonable conditions for iron molybdate deposition

The thermodynamic data on the Fe³⁺/MoO₄ ^2?/H⁺(OH^?)/H₂O system were analyzed. The iron(III) molybdate precipitates were studied by the X-ray phase analysis and electron probe microanalysis. It was shown that the content of the iron(III) oxide impurity in the precipitates depends on method and conditions of mixing of an iron precursor solution and an molybdenum precursor solution.     

苯噻草胺的极谱特性研究

在 p H3.4 H3PO4-Na H2 PO4缓冲溶液中 ,苯噻草胺在 -1 .1 0 V左右产生一灵敏示波极谱波 ,利用此波可测定微量苯噻草胺 ,线性范围为 3.0× 1 0 - 8～ 2 .0× 1 0 - 5 mol/L,检出限为 1 .8× 1 0 - 8mol/L。     

Efficient white light emission by upconversion in Yb(3+)-, Er(3+)- and Tm(3+)-doped Y2BaZnO5

We report efficient white upconversion luminescence in Yb(3+)-, Er(3+)- and Tm(3+)-doped monophasic and biphasic Y(2)BaZnO(5) phosphors under 977 nm near-infrared excitation and at low excitation power densities (down to ～25 mW mm(-2)).