Electrochemical synthesis,magnetic, spectral and cyclic voltammetric studies on lactic acid complexes

Summary Complexes of iron, cobalt, nickel and copper with lactic acid (H₂LA) were prepared by electrochemical oxidation of the metal in non-aqueous solution; this new method gives a high yield (73–87%). The reaction mechanism and the electrochemical efficiency show that cobalt, nickel and copper give divalent complexes and the iron complex is trivalent. The isolated complexes were characterized by physicochemical techniques. C.v.s of the complexes indicate the irreversibility of the electrode processes and confirm the oxidation state of the metals.     

Thermal and structural studies of the chloro complexes of cobalt,nickel and copper with 3-phenylpyridine

The chloro complexes of cobalt, nickel and copper with 3-phenylpyridine were prepared in ethanolic solution from which solid compounds were isolated. The cobalt and copper complexes have stoichiometry M₂LCl₄ while the nickel complex has stoichiometry NiLCl₂. The suggested structure for the cobalt and copper complexes is tetrahedral, while for the nickel complex it is octahedral. Thermal analysis studies show that the cobalt and copper complexes form intermediate complexes before their metal oxides are produced. The nickel complex also forms an intermediate complex and then nickel chloride before the nickel oxide is obtained.     

Synthesis and characterization of iron(III), manganese(II), cobalt(II), nickel(II), copper(II) and zinc(II) complexes of salicylidene-N-anilinoacetohydrazone (H2L1) and 2-hydroxy-1-naphthylidene-N-anilinoacetohydrazone (H2L2)

Salicylidene-N-anilinoacetohydrazone (H(2)L(1)) and 2-hydroxy-1-naphthylidene-N-anilinoacetohydrazone (H(2)L(2)) and their iron(III), manganese(II), cobalt(II), nickel(II), copper(II) and zinc(II) complexes have been synthesized and characterized by IR, electronic spectra, molar conductivities, magnetic susceptibilities and ESR. Mononuclear complexes are formed with molar ratios of 1:1, 1:2 and 1:3 (M:L). The IR studies reveal various modes of chelation. The electronic absorption spectra and magnetic susceptibility measurements show that the iron(III), nickel(II) and cobalt(II) complexes of H(2)L(1) have octahedral geometry. While the cobalt(II) complexes of H(2)L(2) were separated as tetrahedral structure. The copper(II) complexes have square planar stereochemistry. The ESR parameters of the copper(II) complexes at room temperature were calculated. The g values for copper(II) complexes proved that the Cu-O and Cu-N bonds are of high covalency.     

Iron(II), cobalt(III), nickel(II) and copper(II) chelates of furan and thiophene azo-oximes

Summary Complexes of furan and thiophene azo-oximes with iron(II), cobalt(III), nickel(II) and copper(II) have been prepared and characterised. Iron(II), cobalt(III) and copper(II) complexes are diamagnetic in the solid state. The diamagnetism of the copper(II) chelates is suggestive of antiferromagnetic interaction between two copper centres.¹H n.m.r. spectral data suggest atrans-octahedral geometry for the tris-chelates of cobalt(III). Nickel(II) complexes are paramagnetic, in contrast to the diamagnetism of the analogous complexes of arylazooximes. The electronic spectra are suggestive of octahedral geometry for the iron(II), cobalt(III) and nickel(II) complexes, andD _4h -symmetry for copper(II). Infrared data indicate N-bonding of the oximino-group to the metal ions.     

Bis-cyclohexanone-oxalyldihydrazone as a spectrophotometric reagent for cobalt and nickel

Cobalt and nickel ions form yellow complexes with bis-cyclohexanone-oxalyldihydrazone in alkaline solutions. These complexes have maximum absorbances at 292 μg and 330 μg, respectively. The cobalt complex obeys Beer's law from 10^-4 to 5.10^-3 mg cobalt per ml and the molar extinction coefficient is 6500. The nickel complex obeys Beer's law from 10^-4 to 7.10^-3 rng nickel per ml and the molar extinction coefficient is 8750. Cobalt and copper or nickel and copper can be determined in presence of each other.     

Study on Determination of Six Transition Metal Ions in Biological Samples by SPE and RP‐HPLC

This paper reports the utilization of solid phase extraction and the reversed‐phase high‐performance liquid chromatography (RP‐HPLC) for the determination of six transition metal ions (iron, cobalt, nickel, copper, zinc and manganese) in biological samples. The samples were digested by microwave digestion. The iron, cobalt, nickel, copper, zinc and manganese ions in the digested samples can react with 2‐(2‐quinolinylazo)‐5‐diethylaminophenol (QADEAP) to form colored chelates in pH 4.0 acetic acid‐sodium acetic buffer solutions and cetyl trimethylammonium bromide (CTMAB) medium. These chelates were enriched by solid phase extraction with C₁₈ cartridge. Then the chelates were separated on a Waters Nova‐Pak‐C₁₈ column (3.9 × 150 mm, 5 μm) by gradient elution with methanol (containing 0.5% of acetic acid and 0.1% of CTMAB) and 0.05 mol/L pH 4.0 acetic acid‐sodium acetic buffer solution (containing 0.1% of CTMAB) as mobile phase at a flow rate of 0.5 mL/min. The detection limits of iron, cobalt, nickel, copper, zinc and manganese are 3 ng/L, 4 ng/L, 2 ng/L, 4 ng/L, 8 ng/L, 10 ng/L, respectively. This method was applied to the determination of iron, cobalt, nickel, copper, zinc and manganese in biological samples with good results.     

Simultaneous spectrophotometric determination of cobalt,copper and nickel using 1-（2-thiazolylazo）-2-naphthol by chemometrics methods

The simultaneous determination of cobalt, copper and nickel using 1-（2-thiazolylazo）-2-naphthol （first figure of this article） by spectrophotometric method is a difficult problem in analytical chemistry, due to spectral interferences. By multivariate calibration methods, such as partial least squares （PLS） regression, 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 for removing the information unrelated to the target variables based on constrained principal component analysis. OSC is a suitable preprocessing method for PLS calibration of mixtures without loss of prediction capacity using spectrophotometric method. In this study, the calibration model is based on absorption spectra in the 550-750-nm range for 21 different mixtures of cobalt, copper and nickel. Calibration matrices were formed from samples containing 0.05-1.05, 0.05-1.30 and 0.05-0.80 μg·mL^-1 for cobalt, copper and nickel, respectively. The root mean square error of prediction （RMSEP） for cobalt, copper and nickel with OSC and without OSC were 0.007, 0.008, 0.011 and 0.031,0.037, 0.032 μg· mL^-1, respectively. This procedure allows the simultaneous determination of cobalt, copper and nickel in synthetic and real samples and good reliability of the determination was proved.     

Liquid chromatographic determination of chelates of cobalt (II), copper (II) and iron (II) with 2-thiophonaldehyde-4-phenyl-3-thiosemicarbazone

Summary A new chelating reagent 2-thiophenaldehyde-4-phenyl-3-thiosemicarbazone (TAPT) has been examined for high performance liquid chromatographic (HPLC) separations of cobalt (II), copper(II) and iron (II) or cobalt (II), nickel (II), iron (II), copper (II) and mercury (II) as metal chelates on a C₁₈, 5μm column (250×4 mm i.d.) The chelates were eluted isocratically with methanol: acetonitrile: water containing sodium acetate and tetrabutylammonium bromide (TBA), and detected at 254 nm. A solvent extraction procedure was developed for simultaneous determination of the metals with detection limits within 0.02–2.5 μ g.mL⁻¹. The method was applied to the determination of copper, cobalt and iron in natural waters.     

Syntheses,Spectral, Thermal and Electrochemical Studies of 3-Carboxylacetonehydroxamic Acid and its Iron(Ii), Cobalt(Ii), Nickel(Ii), Copper(Ii) and Zinc(Ii) Complexes

3-Carboxylacetonehydroxamic acid (CAHA) and its iron(II), cobalt(II), nickel(II), copper(II) and zinc(II) complexes were synthesized and characterized by elemental analysis, UV-Vis and IR spectra and magnetic susceptibility. The pK _a1 and pK _a2 values of the ligand in aqueous solution were found to be 6.5 ± 0.1 and 8.6 ± 0.1, which correspond to dissociation of carboxyl and hydroxamic protons, respectively. The dianion CAH acts as a tetradentate ligand through the hydroxamate and carboxylate groups and coordinates to the divalent metal ions, forming coordination polymers with a metal-to-ligand ratio of 1 : 1 in the solid state. FTIR spectra and thermal decomposition of the ligand and its metal complexes were recorded and briefly discussed. The electrochemical behavior of the complexes was investigated by square wave voltammetry and cyclic voltammetry at neutral pH. In contrast to the solid state, the iron(II) and copper(II) cations form stable complex species with a metal-to-ligand ratio of 1 : 2 in solution. The iron(II), cobalt(II) and nickel(II) complexes show two-electron irreversible reduction behavior, while the copper(II) and zinc(II) complexes undergo quasi-reversible and reversible electrode reactions, respectively. The stability constants of the complexes were determined by square wave voltammetry.     

High performance liquid chromatographic separation and UV determination of cobalt, copper iron and platinum in pharmaceutical preparations using bis(isovalerylacetone)ethylenediimine as complexing reagent

The reagent bis(isovalerylacetone)ethylenediimine(H₂IVA₂en) has been examined for HPLC separation and UV determination of cobalt, copper, iron and platinum using off-line precolumn derivatization and extraction in chloroform. The complexes of cobalt(II), cobalt(III), iron(II), iron(III) and the reagent have been subsequently separated on a Microsorb C-18 column. The complexes were eluted isocratically using ternary mixtures of methanol/water/acetonitrile. Detection was achieved by UV monitoring. Detection limits for Co(II), Co(III), Fe(II) and Fe(III) were 2.5–5.0 ng/injection, based on 0.5–1.0 g/ml with 5 l/injection. The concentration of cobalt(II) and cobalt(III) in aqueous solution have been determined. The presence of oxovanadium(IV), platinum(II), and nickel(II) did not affect the determinations. The HPLC method developed has been applied to the determination of cobalt, copper, iron and platinum in pharmaceutical preparations at the 30 g/g to 15 mg/g level and the obtained results were compared to those of atomic absorption spectrometry.     

Simultaneous extraction of trace amounts of cobalt, nickel and copper ions using magnetic iron oxide nanoparticles without chelating agent

The present study investigates the application of Fe₃O₄ nanoparticles as an adsorbent for solid phase extraction and their subsequent determination of trace amounts of cobalt, nickel and copper from environmental water samples using flame atomic absorption spectrometry. The analyte ions were adsorbed on magnetic nanoparticles in the pH range of 10–12 and then, Fe₃O₄ nanoparticles were easily separated from the aqueous solution by applying an external magnetic field and decantation. Hence, no filtration or centrifugation was needed. After extraction and collection of magnetic nanoparticles, the analyte ions were desorbed using 1.0 M HNO₃. Several factors that may affect the preconcentration and extraction process, including pH, type and volume of eluent, sample volume, salt effect and matrix effect were optimized. Under the optimized conditions, linearity was maintained from 0.005–3.0 μg/mL for cobalt and nickel and 0.001 to 1.25 μg/mL for copper in the initial solution. The detection limits of this method for cobalt, nickel and copper ions were 0.9, 0.7 and 0.3 ng/mL, respectively. Finally, the method was successfully applied to the extraction and determination of the analyte ions in natural waters and reference plant samples.     

Spectral and thermal studies on new hydrazinium metal sulfite dihydrates

Some new hydrazinium transition metal sulfite dihydrate complexes of the formula (N₂H₅)₂M(SO₃)₂(H₂O)₂ where M=Fe, Co, Ni, Cu and Zn have been prepared and characterized by hydrazine and metal analyses, magnetic studies, electronic and infrared spectra and thermal analysis. The magnetic studies coupled with electronic spectra of iron, cobalt, nickel and copper complexes indicate their high spin octahedral nature. However the zinc complex is diamagnetic and show only the charge transfer transition. The infrared spectra shows that both the hydrazinium ions are coordinated to the metal ions, the sulfite ions are present as bidentate ligand. The simultaneous TG-DTA of these complexes were investigated in air and nitrogen atmospheres. In air, cobalt, nickel and zinc complexes give respective metal sulfate as the final residue while iron and copper complexes give the mixture of respective metal oxide and sulfate as the decomposition product. In nitrogen atmosphere respective metal sulfites are formed as the end residue.     

Electrothermal Atomic Absorption Spectrometric Determination of Cobalt,Copper and Nickel in Fresh Water After Their Preconcentration by Precipitate Flotation

Abstract

A method is developed for simultaneous separation and determination of μg/L levels of Co(II), Cu(II) and Ni(II) in fresh water by precipitate flotation. The optimal conditions of the experimental procedure with hydrated iron(III) oxide and iron(III) tetramethylenedithiocarbamate as collectors were investigated. The pH interval of the working medium, within which Co(II), Cu(II) and Ni(II) can be successfully separated, was determined from the aspect of collectors and surfactant stability. The amounts of the elements investigated were determined by electrothermal atomic absorption spectrometry. The detection limit of the method is 0.15 μg/L for cobalt, 0.03 μg/L for copper and 0.79 μg/L for nickel.     

Synthesis of certain pyridinyl and diazinyl hydrazones containing one or more ferroin groups, and their chromogenic reactions with iron, copper, cobalt and nickel

Fifteen new hydrazones with one or more ferroin groups were prepared, and their chelation and chromogenic properties with iron(II), copper(I), cobalt(II) and nickel(II) were investigated. Improved sensitivity in the spectrophotometric determination of cobalt, copper, and nickel is provided by several of the new compounds. Several others are capable of forming unusually stable and interesting binuclear iron(II) complexes.     

Determinations of Some Trace Metals in Dialysis Solutions by Atomic Absorption Spectrometry After Preconcentration

Abstract

A method is presented for the determination of copper, lead, iron, cadmium, cobalt and nickel in dialysis solution at μg/1 level by atomic absorption spectrometry after preconcentration. The preconcentration is based on chelate formation of the investigated metals with ammonium pyrrolydine dithiocarbamate and on retention of the chelates on Amberlite XAD-4 in a short column. The relative standard deviations for the determinations were found to be lower than 0.08.     

Transition metal complexes of acetamidomalondihydroxamate: synthesis,spectral, thermal and electrochemical studies

Acetamidomalondihydroxamate (K₂AcAMDH) and its manganese(II), iron(II), cobalt(II), nickel(II), copper(II) and zinc(II) complexes were synthesized and characterized by elemental analysis, UV–VIS, IR and magnetic susceptibility. The pK _a1 and pK _a2 values of the dihydroxamic acid in aqueous solution were found to be 8.0?±?0.1 and 9.7?±?0.1. The dihydroxamate anion AcAMDH behaves as a tetradentate bridging ligand through both hydroxamate groups, forming complexes with a metal to ligand ratio of 1?:?1 in the solid state. The FTIR spectra and thermal decompositions of the ligand and its metal complexes were recorded. The redox behavior of the complexes was investigated in aqueous solution by square wave voltammetry and cyclic voltammetry at neutral pH. In contrast to the solid state, in solution the copper(II) and zinc(II) ions form stable complex species with a metal to ligand ratio of 1?:?2. The iron(II) and nickel(II) complexes show a two-electron irreversible reduction behavior, while the copper(II) and zinc(II) complexes undergo reversible electrode reactions. The stability constants of the complexes were determined by square wave voltammetry.     

Spektrophotometrische Bestimmung von Nickel, Kobalt, Kupfer, Eisen und Zink in Niob

Zusammenfassung Nickel-, Kobalt-, Kupfer-, Eisen- und Zinkspuren werden als Diäthyldithiocarbamidatkomplexe durch Extraktion von Mob abgetrennt. Anschließend trennt man diese Elemente durch Anionenaustausch-Chromatographie voneinander und bestimmt sie in den einzelnen Fraktionen spektrophotometrisch. Die Nachweisgrenzen liegen für 0,5 g Einwaage bei 0,3 ppm Nickel, 0,1 ppm Kobalt, 0,3 ppm Kupfer, 0,3 ppm Eisen und 0,3 ppm Zink. Die Variationskoeffizienten der Bestimmungen schwanken in Abhängigkeit vom Spurengehalt bei den verschiedenen Elementen zwischen 4 und 24%.

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Summary Traces of nickel, cobalt, copper, iron and zinc are separated from niobium as diethyldithiocarbamidate complexes by extraction. Thereafter these elements are separated from each other by ion-exchange chromatography and determined spectrophotometrically. Amounts of 0.3 ppm of nickel, copper, iron and zinc and of 0.1 ppm of cobalt can be determined in 0.5 g of niobium. The relative standard deviations vary from 4 to 24% for the different elements in dependence of the contents of impurities.

     

Trace determination of iron,cobalt, nickel and copper in zirconium fluoride by substoichiometric radioactivation analysis

Trace amounts of transition elements (Fe, Co, Ni and Cu) in zirconium fluoride and NBS SRM's were determined by substoichiometric radioactivation analysis. The contents of impurities in sublimed sample were less than those of high-purity material and of reagent grade. The detection limits of these elements in zirconium fluoride were 10 ng/g for iron, 0.01 ng/g for cobalt, 1 ng/g for nickel and 0.1 ng/g for copper. The analytical results for iron, cobalt, nickel and copper in NBS SRM's were in good agreement with certified values.     

Electrochemical synthesis of benzoylglycine and ethylphthaloyl-glycine complexes of transition metal ions

Summary The direct electrochemical oxidation of metallic iron, cobalt, nickel and copper in Me₂CO solution of benzoylglycine and/or ethylphthaloylglycine gave products with high yields. For each of the complexes, the electrochemical efficiency is commensurate with the metals being divalent. Conventional physical and chemical studies were used to characterize the isolated complexes and octahedral geometry was suggested for them on the basis of magnetic and electronic spectral studies. The i.r. spectra show that the ligands coordinate in a bidentate fashion; the carboxylate ion is monodentate. The molar conductances agree with the complexes being non-electrolytes.     

New copper(II), nickel(II), and cobalt(II) chelates derived from 2-methyl-3-{[3-methyl-5-oxo-1-phenylpyrazol-4- ylidene)methyl]amino}-quinazolin-4-one

Ligand system derived from pyrazolone-5 and N-aminoquinazolinone was prepared, its structure was studied. Metal chelates ML₂ were prepared by reaction of the obtained ligand with copper(II), nickel(II), and cobalt(II) acetates. The complexes were studied by IR, electronic, and ESR spectroscopy, magnetochemistry, X-ray diffraction. Copper(II) complex was shown to have pseudo-tetrahedral structure, nickel(II) and cobalt(II) complexes are octahedral.