Spectrophotometric determination of copper in environmental samples by solid-liquid extraction of its 9, 10-phenanthrenequinone monoximate complex into molten naphthalene

A fairly selective and sensitive spectrophotometric method has been developed for determination of copper after extraction of its 9, 10-phenanthrenequinone monoximate complex into molten naphthalene in the pH range of 6.1-8.4. At room temperature, the solid naphthalene containing the metal complex is separated by filtration, dissolved in dimethylformamide (DMF) and the absorbance measured at 470 nm against the reagent blank. Beer's law is obeyed in the concentration range, 0.0-9.6 micrograms of copper in 10ml of DMF. The molar absorptivity and sensitivity are 6.30 X 10(4) 1 mol-1 cm-1 and 0.001 micrograms cm-2, respectively. The interference of various ions has been studied and the method has been applied for the determination of copper in various standard reference materials, beers, wines, human hair and environmental samples.     

Complexes of Ruthenium and Osmium with 4-Amino-2-Mercapto-5-Nitroso-6-Pyrimidinol

Ruthenium(III) and osmium(VIII) form coloured complexes with 4–amino ?2-mercapto-5-nitroso-6-pyrimidinol (ammonium salt). The complexes have been spectrophotometrically studied and made use of in determination of the two metals; the reaction with ruthenium is particularly sensitive (0.006 μg of ruthenium/cm²for 0.001 absorbance). Many ions do not interfere in the determination.     

Spectrophotometric and derivative spectrophotometric determination of copper (II) with dithizone in aqueous phase

A Spectrophotometric and derivative Spectrophotometric study of Cu-dithizonate complex in aqueous phase in the presence of Triton X-100, a neutral surfactant, is reported. The system obeys Beer's law between 1.0 × 10^–6–9.0 × 10^–6 mol/l of Cu²⁺; detection limit is 12 ng/ml. The molar absorption coefficient, specific absorptivity and Sandell's sensitivity of the complex are 3.06 × 10⁴ 1 mol^–1 cm^–1, 0.4825 ml g^–1 cm^–1 and 2.1 × 10^–3 g cm^–2, respectively. The conditional stability constant of the 1 2 complex, calculated considering simultaneously existing equilibria, has been found to be 1.73 × 10¹¹ I² mol² (I = 0.07, pH 1.4, temperature = 10 °C). Absorption studies in the derivative mode have been carried out to determine the absorption maximum of the complex and to overcome interference due to the presence of certain metal ions. The method has been validated by determination of copper in beers, wines, human hair, goat liver and fly ash samples.     

Complexation reactions of pyridinols

Complexation of iron(III) with several pyridinols has been studied and used in selective detection and determination (spectrophotometric and chelatometric) of the metal. Iron(III)-pyridinol complexes are also used as indicators in acid-base titrations. A thiol group vicinal to a phenol group in a pyridine molecule provides a reagent that is a suitable ligand for palladium(II) determination. Stability constants of bivalent metal complexes with pyridinols have been determined potentiometrically.     

Structural and magnetic properties of nano nickel-zinc ferrite synthesized by reverse micelle technique

Nanocrystalline nickel-zinc ferrites (Ni_0.58Zn_0.42Fe₂O₄) at different pH values (less than 9.6, 9.6, 10.96, and 11.40) for the alkali-precipitating reaction were synthesized by reverse micelle technique. X-ray diffraction reveals a well-defined nickel-zinc ferrite crystal phase at pH=9.6. Increase in pH value obstructs pure-phase formation and results in partial formation of α-Fe₂O₃. The magnetic behaviour of the samples was studied by superconducting quantum interference device. All the samples show superparamagnetic behaviour at room temperature (300 K) and negligible hysteresis at low temperature (5 K). The low value of saturation magnetization is explained on the basis of spin canting. The high-field irreversibility and shifting of the hysteresis loop detected in single-phase sample has been assigned to a spin-disordered phase, which has a spin-freezing temperature of approximately 42 K and other two samples have an antiferromagnetic phase (α-Fe₂O₃) coupled to the ferromagnetic phase.     

Vanadium(III) Acetylacetonate as an Efficient Soluble Catalyst for Lithium–Oxygen Batteries

High donor number (DN) solvents in Li—O₂ batteries that dissolve superoxide intermediates in lithium peroxide (Li₂O₂) formation facilitate high capacities at high rates and avoid early cell death. However, their beneficial characteristics also result in an instability towards highly reactive superoxide intermediates. Furthermore, Li—O₂ batteries would deliver a superior energy density, but the multiphase electrochemical reactions are difficult to achieve when operating with only solid catalysts. Herein we demonstrate that vanadium(III) acetylacetonate (V(acac)₃) is an efficient soluble catalyst that can address these problems. During discharge, V(acac)₃ integrates with the superoxide intermediate, accelerating O₂ reduction kinetics and reducing side reactions. During charge, V(acac)₃ acts as a redox mediator that permits efficient oxidation of Li₂O₂. The cells with V(acac)₃ exhibit low overpotential, high rate performance, and considerable cycle stability.