Cupferron Complexes Research Articles

Supporting Electrolyte Manipulation for Simple Improvement of the Sensitivity of Trace Vanadium(V) Determination at a Lead-Coated Glassy Carbon Electrode.

The paper presents a very simple way to extremely improve the sensitivity of trace V(V) determination. The application of a new supporting electrolyte composition (CH3COONH4, CH3COOH, and NH4Cl) instead of the commonly used acetate buffer (CH3COONa and CH3COOH) significantly enhanced the adsorptive stripping voltammetric signal of vanadium(V) at the lead-coated glassy carbon electrode (GCE/PbF). A higher enhancement was attained in the presence of cupferron as a complexing agent (approximately 10 times V(V) signal amplification) than in the case of chloranilic acid and bromate ions (approximately 0.5 times V(V) signal amplification). Therefore, the adsorptive stripping voltammetric system with the accumulation of V(V)-cupferron complexes at -1.1 V for 15 s in the buffer solution (CH3COONH4, CH3COOH, and NH4Cl) of pH = 5.6 ± 0.1 was selected for the development of a simple and extremely sensitive V(V) analysis procedure. Under optimized conditions, the sensitivity of the procedure was 6.30 µA/nmol L-1. The cathodic peak current of V(V) was directly proportional to its concentration in the ranges of 1.0 × 10-11 to 2.0 × 10-10 mol L-1 and 2.0 × 10-10 to 1.0 × 10-8 mol L-1. Among the electrochemical procedures, the lowest detection limit (2.8 × 10-12 mol L-1) of V(V) was obtained for the shortest accumulation time (15 s). The high accuracy of the procedure was confirmed on the basis of the analysis of certified reference material (estuarine water) and river water samples.

Application of adsorptive stripping voltammetry based on PbFE for the determination of trace aluminum released into the environment during the corrosion process

This work presents a new fast and sensitive method for voltammetric determination of Al(III) as Al(III)-cupferron complexes, which was used for the analysis of solution after exposure of aluminum alloy AA2024. Experimental conditions of voltammetric measurement such as preconcentration time, potential, and operating parameters were optimized. The formed Al(III)-cupferron complexes were adsorbed on an in situ plated lead film electrode (PbFE) using the potentials of −1.2 V (15 s) and −0.7 V (60 s) versus Ag/AgCl electrode. The promising results were obtained in 0.1 mol L−1 ammonia buffer at pH = 8.15 and 6 ∙ 10−5 mol L−1 Pb(II), 3 ∙ 10−4 mol L−1cupferron. The calibration graph was linear from 1 ∙ 10−10 to 2 ∙ 10−7 mol L−1 with the calculated detection limit of 3.3 ∙ 10−11 mol L−1, repeatability with RSD of 4.9% (n = 5). The accuracy was established by analysis of the synthetic sample.

Simple and Fast Simultaneously Determination of In(III) and Ti(IV) Using Lead Modified Glassy Carbon Electrode by Stripping Voltammetry

A new reliable adsorptive stripping voltammetry (AdSV) procedure was described regarding simultaneous determination of titanium and indium as cupferron complexes at trace concentrations. An in situ plated eco-friendly lead film electrode (PbFE) was chosen as a working electrode. Optimal conditions were found to be as follows: 0.2 mol l−1 acetate buffer (pH = 6.0), 7 × 10−5 mol l−1 Pb(II), 5 × 10−4 mol l−1 cupferron, accumulation potential of −0.9 V, and accumulation time of 30 s. The linear range of Ti(IV) and In(III) was observed over the concentration range from 5 × 10−9 mol l−1 to 3 × 10−7 mol l−1 and from 5 × 10−9 mol l−1 to 4 × 10−7 mol l−1, respectively. The developed procedure was examined towards potential interferences caused by different metal ions and different types of surfactants and humic substances. The method was satisfactorily applied to simultaneous quantification of titanium and indium in river water samples.

Electrochemical Reduction of Vanadium(V)‐Cupferron Complex, VO(cupf)2OH

AbstractElectrochemical reduction of vanadium(V) complex with cupferron (N‐nitroso‐N‐phenylhydroxylamine), VVO(cupf)2OH, has been studied by polarography in wide potential range to verify the catalytic mechanism of electroreduction of coordinated cupferron ligand. Reduction of the complex was studied in the concentration range from 2 ⋅ 10−5 M to 10−3 M. Depending on the process conditions kinetics of catalytic reduction of coordinated cupferron is either controlled by adsorption step or governed by mixed control of diffusion and chemical reaction. Kinetic parameters of the reduction process are reported.Reduction of VVO(cupf)2OH complex is accompanied by adsorption and autoinhibition phenomena. V(II) ion in the surface bound complex of vanadium with cupferron catalyzes reduction of coordinated cupferronate ligands. In 1 mM solutions, the catalytic reduction of coordinated cupferron ligand shifts to more cathodic potentials due to formation of a monolayer of adsorbed vanadium(III)‐cupferron complexes. Reduction kinetics in the presence of tetraalkylammonium salt is consistent with multilayer cooperative adsorption of anionic vanadium(II)‐cupferron complex and tetraalkylammonium cations.

Evaluation of cupferron on the selective separation of gallium from aluminum by flotation: The separation mechanism

Aluminum is an impure element in acidic solutions obtained from gallium sources. Therefore, the selective separation of gallium from aluminum, using cupferron as a ligand (chelating agent) and sodium dodecyl sulfate as an anionic collector was investigated by flotation. The effect of the solution pH, the molar ratio of cupferron to gallium, the collector concentration, the impeller speed, the conditioning time and the flotation time on the selective separation of Ga(III) from Al(III) were studied. The results indicate that the chelating agent cupferron, efficiently separated gallium from aluminum, owing to the higher chelating strength of the interaction between Ga(III) and cupferron. The Ga(III)-cupferron complexes, formed in the presence and absence of SDS, were spectroscopically confirmed and characterized by Fourier transform infrared (FTIR), UV–visible spectroscopy and scanning electron microscopy coupled with energy dispersive X-ray (SEM/EDX). The bonding of cupferron with Ga(III) was considered to be as a bidentate ligand, and gallium formed 1:1.5 complexes with cupferron in aqueous solution. The separation mechanism of flotation was proposed owing to the formation of a physical interaction between the Ga(III)-cupferron complex and SDS.

Graphene-Based Preconcentration System Prior to Energy Dispersive X-Ray Fluorescence Spectrometric Determination of Co, Ni, and Cu Ions in Wine Samples

A combination of dispersive micro solid-phase extraction (DMSPE), based on graphene as a solid sorbent, with energy dispersive X-ray fluorescence spectrometry (EDXRF) is proposed for preconcentration and determination of Co(II), Ni(II), and Cu(II) ions in wine samples. In the developed procedure, cupferron complexes of metal ions are adsorbed on graphene dispersed in aqueous samples. After the adsorption process, aqueous samples are passed through a membrane filter with the use of filtration assembly, and then loaded filters are directly measured using EDXRF. In order to obtain high recovery of the metal ions, various analytical parameters influencing sorption were optimized, such as pH, amount of graphene, Triton X-100 and cupferron, sample volume, and sorption time. Under optimal conditions, the calibration plots cover the 2 to 100 ng mL−1 range for Co(II) and Ni(II), and 2 to 150 ng mL−1 for Cu(II). The detection limits of 0.08, 0.08, and 0.07 ng mL−1 for Co(II), Ni(II), and Cu(II) were obtained using 50 mL sample volume and 200 μg of graphene. The precision (at a 20 ng mL−1 level for n = 10) is lower than 3.5 %. The proposed method was successfully applied to determination of Co, Ni, and Cu in wine samples.

A new sensitive electrochemical method for the determination of vanadium(IV) and vanadium(V) in Benfield sample

Vanadium(IV) and vanadium(V) can be determined by using differential pulse cathodic stripping voltammetry technique (DPCSV). Cupferron (ammonium N-nitrosophenylhydroxylamine) was used as ligand to form complex compounds with vanadium ions in Britton–Robinson buffer (BRB) solution. At concentration lower than 1.0×10−6M, both V(IV) and V(V) cupferron complexes showed a single cathodic peak at −0.576V in BRB of pH 4; thus V(IV) and V(V) ions cannot be differentiated at low concentration. However, the ionic species of vanadium can be differentiated at high concentration in the presence of cupferron. Parameters including pH of BRB solution, initial potential and accumulation potential were optimized. Under the optimized parameters, the limit of detection (LOD) was 0.09nM, and the peak current was linear in the concentration range 0.01–0.9µM total vanadium ions. The determination of V(IV) and V(V) ions was carried out at higher concentration in the sample using calibration plot method. At higher concentration range of 10–60µM V(IV) and V(V) ions were determined with LOD of 1.2 and 1.1µM, respectively. The developed method was successfully applied to 10,00,000 fold diluted Benfield sample and 0.6227M total vanadium ions were determined. The determination of V(IV) and V(V) ions were also successfully carried out in artificial sample as well as Benfield sample (dilution factor, 10,000). The concentration of V(IV) and V(V) ions was 22.52µM and 38.91µM, respectively, giving total vanadium concentration of 0.6143M in Benfield sample.

Simple and fast voltammetric procedure of U(VI) determination in the presence of high concentrations of surface active substances

In this work, a simple and fast procedure for elimination of interfering surface active substances and for U(VI) adsorptive stripping voltammetric determination was developed. The adsorption in the form of U(VI)-cupferron complexes was performed, because as it was proved before, U(VI) forms with cupferron stable complexes, which were employed in voltammetric procedures. The procedure is based on two steps: the first is an adsorption of surface active substances onto an Amberlite XAD-16 or XAD-7 resin and the second is a voltammetric determination of U(VI) with a pulsed potential of accumulation alternate –0.65–0.3 V with the frequency of 0.5 Hz and then the differential pulse voltammogram was recorded, whereas the potential was scanned from –0.65 to –1.2 V. The detection limit estimated from three times the standard deviation for a low U(VI) concentrations was equal to 1.7 × 10−10 mol L−1 (7.2 × 10−8 g L−1). The linear range of U(VI) was observed over the concentration range from 5.0 × 10−10 mol L−1 (2.1 × 10−7 g L−1) to 2.0 × 10−8 mol L−1 (8.5 × 10−6 g L−1) for an accumulation time of 60 s. The influence of different kinds of surfactants, such as non-ionic, cationic and anionic on the uranium voltammetric signal was studied. The results confirm the possibility of U(VI) determination in water samples containing high concentrations of surface active substances even up to 50 mg L−1.

A Highly Sensitive Adsorptive Stripping Voltammetric Method for Simultaneous Determination of Lead and Vanadium in Foodstuffs

This work describes a procedure for the simultaneous determination of vanadium and lead in some food and water samples using adsorptive stripping voltammetric method. The method is based on the adsorptive accumulation of cupferron complexes of these elements onto hanging mercury drop electrode, followed by reduction of adsorbed species by voltammetric scan using differential pulse modulation. Optimal analytical conditions were found to be cupferron concentration of 8.00 × 10−5 M, pH of 4.8 (phosphate buffer), an accumulation potential at −100 mV, and a scan rate of 80 mV s−1. With an accumulation time of 50 s, the peak currents proportional to the concentration of lead and vanadium over the 0.05–80.00 and 0.10–105.00 ng mL−1 ranges with detection limit of 0.02 and 0.01 ng mL−1, respectively. The procedure was applied to simultaneous determination of vanadium and lead in some food and water samples with satisfactory results.

Solvothermal routes to capped oxide and chalcogenide nanoparticles

Abstract We review our recent contributions to the use of solvothermal methods for the preparation of different oxide and chalcogenide nanoparticles. We have prepared sub 10-nm g-Fe2O3, ZnFe2O4, and CoFe2O4 particles by the decomposition of the corresponding cupferron complexes in the presence of n-octylamine or n-dodecylamine in solvothermal toluene. Similarly, dodecanethiol-capped chalcogenide nanoparticles of CdSe have been prepared by reacting cadmium stearates with H2Se under solvothermal conditions. The H2Se is generated in situ by the reduction of Se by tetralin. Using this latter technique, we have also been able to prepare PbSe and PbI2 in toluene under solvothermal conditions, albeit in bulk (rather than nanocrystalline) form. In the preparation of PbI2, HI is prepared by the in situ reduction of I2 by tetralin.

A solvothermal route to capped nanoparticles of γ-Fe2O3 and CoFe2O4

The decomposition of single or multiple transition metal cupferron complexes in organic solvents under solvothermal conditions and in the presence of long chain amines yields the corresponding oxide nanoparticles. The examples presented here are maghemite γ-Fe2O3 nanoparticles from an FeIII–cupferron complex and spinel CoFe2O4 nanoparticles starting from CoII–cupferron complex and FeIII–cupferron complex taken in suitable proportions. The nanoparticles are capped with n-octylamine or n-dodecylamine. The presence of amine in the reaction is found to be essential for the formation of the product. The magnetic behavior of pressed pellets of these nanoparticles is presented.

Separation and direct UV detection of lanthanides complexed with cupferron by capillary electrophoresis

Separation and detection of lanthanides by capillary zone electrophoresis in the presence of cupferron ( N-nitroso- N-phenylhydroxylamine) as UV absorbing complexing agent were investigated. The resolution of partially complexed positively charged cupferron complexes is improved by using a buffer ligand competing with cupferron for metal ions. When hydroxyisobutyric acid (HIBA) is used as buffer and competing ligand, it provides complete separation of all 14 lanthanides with good peak shapes. An on-column separation of 14 lanthanides was achieved in only 7 min using 0.1 mmol/l cupferron, 15 mmol/l HIBA at pH 4.9. The separation efficiencies for the optimum separation condition are between 77 000 and 208 000 theoretical plates. Determination of lanthanide complexes was performed by direct UV detection at 210 nm. Detection limits (signal-to-noise ratio=3) are ca. 0.24–0.47 μg/ml for lanthanides. Under optimum conditions, the complete separation of thorium and uranium from mixed lanthanides was achieved.

The Reaction of Nitroxyl (HNO) with Nitrosobenzene Gives Cupferron (N-Nitrosophenylhydroxylamine)

Nitroxyl (HNO), a penultimate product in the NOS-catalyzed conversion ofl-arginine tol-citrulline, generated from Angeli's salt (AS) was determined by trapping it with nitrosobenzene (NB) to produce cupferron. The cupferron thus produced was characterized by complexation with Fe3+, Al3+, Cu2+, or Sn2+. UV/VIS spectra of the solubilized (in CHCl3) precipitates formed from NB and nitroxyl generated from AS in the presence of the iron, aluminum, copper, or tin salts were identical to those of their corresponding cupferron complexes. The identities of the Fe3+and Cu2+complexes formed from NB and HNO were further confirmed by their identical retention times on HPLC when compared to authentic Fe3+and Cu2+cupferron complexes. It was possible to detect 5 × 10−6M of the cupferron Fe3+complex spectrophotometrically and to measure its production from the nitroxyl generators AS and methanesulfohydroxamic acid (MSHA) in the presence of 10−4M NB. The yield of cupferron was 51 and 62% of the amount of nitroxyl possible from AS or MSHA, respectively, after taking into account the relative rates of nitroxyl generation from these donors.

Study of the reduction mechanism and the adsorption properties of uranium (VI)-cupferron complexes using various electrochemical techniques

The reduction mechanism of uranium(VI)-cupferron was studied by different electrochemical techniques such as stripping voltammetry and cyclic voltammetry. It is proposed that the U(VI) ions in the form of adsorbed complexes with cupferron are reduced at -0.46 V to U(V). The further reduction to U(III) is followed by a parallel catalytic reaction, which results in a chemical re-oxidation of the latter to U(V), with cupferron playing the double role of complexing and oxidizing agent. The strong adsorption properties of the complexes were studied by applying the recently developed three-dimensional phase-sensitive alternating current voltammetry.

Visible and Near IR Spectra of Some Divalent Transition Metal Cupferron Complexes

The visible and near IR spectra of the ammonium salt of cupferron and manganese, cobalt, nickel and copper divalent cupferrate complexes are investigated. New absorption bands observed are given and assigned using the Tanabe-Sugano diagrams. In the absorption spectra of the divalent transition metal cupferrates a characteristic shift in the maxima and minima appears. Solvent effects on this shift were investigated.

Magnetic Properties of Some Divalent Transition Metal Cupferron Complexes

The magnetic susceptibilities and magnetic moments of the ammonium salt of cupferron and manganese, cobalt, nickel and copper divalent complexes are investigated. The ammonium salt of cupferron is diamagnetic while the divalent transition metal cupferron complexes exhibit paramagnetic behaviour. For manganese, cobalt and nickel cupferrates the magnetic moment is smaller than the spin-only value, which reflects the effect of the orbital angular momentum and electron delocalization. For copper cupferrate the magnetic moment is nearly equal to the spin-only value.

The thermal dissociation of some metal cupferrate chelates

The thermal dissociation of the cupferron complexes with Cu(II), Ni, Co(II), Zn, Cd, Mn(II), Hg(II), Mg, Ca, Ba, Sr, Al, Fe(III). Ce(III), La, and Nd was studied by differential thermal analysis (DTA) and by pyrolysis into a mass spectrometer. The DTA curves consisted mainly of endothermic peaks although some contained exothermic peaks as well. The mass spectrometer showed that cupferron decomposes slightly above room temperature, giving off N 2, NO, N 2O, NH 3 and H 2O. A mechanism for the thermal dissociation of the coppcr(II) cupferrate is proposed.

Thermogravimetric Pyrolysis of Cupferron Complexes of Scandium, Yttrium, and Rate Earth Elements

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTThermogravimetric Pyrolysis of Cupferron Complexes of Scandium, Yttrium, and Rate Earth ElementsW. W. WendlandtCite this: Anal. Chem. 1955, 27, 8, 1277–1278Publication Date (Print):August 1, 1955Publication History Published online1 May 2002Published inissue 1 August 1955https://doi.org/10.1021/ac60104a020RIGHTS & PERMISSIONSArticle Views73Altmetric-Citations35LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (222 KB) Get e-Alerts Get e-Alerts