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The flotation separation of smithsonite and calcite is difficult due to their similar surface properties. In this study, cupferron was applied as a collector to realize the separation of smithsonite and calcite. Micro-flotation experiment results indicated that smithsonite and calcite express different floatability after treatment with cupferron. The maximum recovery difference was 63%, from a cupferron concentration of 2 × 10−4 mol/L at pH 8. Based on a series of tests, including an adsorption test, Fourier-transform infrared (FTIR), zeta potential and X-ray photoelectron spectroscopy (XPS), the selective collection mechanism of cupferron was studied. It was found that the cupferron was more easily adsorbed on the surface of smithsonite and the reaction was violent. The adsorption capacity of the cupferron on the surface of smithsonite was higher than that of calcite, and the surface potential shift was greater. The cupferron chelated with the exposed Zn sites on the smithsonite surface to form a N-O-Zn ring structure. This special chelate structure caused the smithsonite surface to be more hydrophobic, which confirmed that the cupferron can selectively collect smithsonite instead of calcite. [ABSTRACT FROM AUTHOR]

Candida albicans is an opportunistic yeast accounting for about 50–90 % of all cases of candidiasis in humans, ranging from superficial to systemic potentially life-threatening infections. The presence of several virulence factors, including biofilm, hyphal transition, and proteolytic enzymes production, worsens the fungal infections burden on healthcare system resources. Hence, developing new bioactive compounds with antifungal activity is a pressing urgence for the scientific community. In this perspective, we evaluated the anti- Candida potential of the N-Nitroso-N-phenylhydroxylamine ammonium salt (cupferron) against standard and clinical C. albicans strains. Firstly, the in vitro cytotoxicity of cupferron was checked in the range 400–12.5 μg/mL against human microglial cells (HMC-3). Secondly, its antifungal spectrum was explored via disk diffusion test, broth-microdilution method, and time-killing curve analysis, validating the obtained results through scanning electron microscopy (SEM) observations. Additionally, we evaluated the cupferron impact on the main virulence determinants of Candida albicans. At non-toxic concentrations (100–12.5 μg/mL), the compound exerted interesting anti- Candida activity, registering a minimum inhibitory concentration (MIC) between 50 and 100 μg/mL against the tested strains, with a fungistatic effect until 100 μg/mL. Furthermore, cupferron was able to counteract fungal virulence at MIC and sub-MIC values (50–12.5 μg/mL). These findings may propose cupferron as a new potential antifungal option for the treatment of Candida albicans infections. • Antifungal evaluation of cupferron against planktonic and sessile Candida albicans. • Reduction of biofilm, hyphal transition and proteolytic enzymes production. • MIC at 50 μg/mL, with a fungistatic effect until 100 μg/mL. • The cytotoxicity in the range 100–12.5 μg/mL against HMC-3. [ABSTRACT FROM AUTHOR]

[Display omitted] • An approach for separating Ga/Fe and Al from CG/CFA HNO 3 leach liquor was proposed. • Ga/Fe and Al can be separated with cupferron as a Ga-Fe synchronous chelation agent. • The oxygen of cupferron acted as the coordination atom chelated with Ga and Fe. • Cupferron was able to regenerate in the presence of NH 4 OH. Coal gangue and fly ash are typical coal-based solid waste and can be considered as Al and Ga resources. The HNO 3 leaching technology was proposed by our team for the economical and efficient co-extraction of Al and Ga, whereas the separation and recovery of metal elements became a challenge due to the variety of co-existing ions in the leach liquor. In this work, a Ga-Fe iso precipitation strategy with cupferron (C 6 H 9 N 3 O 2) as a selective precipitant followed by regeneration and circulation of cupferron was proposed. The feasibility of the technique was assessed by thermodynamic analysis. The systematic precipitation experiments showed that 99.05 % of Ga, 99.89 % of Fe, and 4.74 % of Al were transferred into the complex precipitation product at optimal conditions. And the separation factor of Ga vs. Al and Fe vs. Al were as high as 2101.74 and 17713.93, respectively. The precipitation mechanism was revealed via a suite of characterization methods to be the chelation of metal ions and cupferron, with the terminal oxygen (N = O) and hydroxyl oxygen (O–H) as ligating atoms. The regeneration rate of cupferron reached 81.28 % with an ammonium hydroxide (NH 3 ·H 2 O) concentration of 8 mol/L. And the circulation experiment demonstrated the excellent performance of the regenerated cupferron. This work provides a new insight into the deep removal of Fe and the enrichment of Ga from the acidic solution. [ABSTRACT FROM AUTHOR]

This paper presents for the first time the use of an environmentally friendly solid bismuth microelectrode for the voltammetric quantification of V(V) in natural water samples. These studies were designed to replace the film bismuth electrode that had been introduced to eliminate the conventional sensors based on highly toxic mercury. In the proposed procedure, V(V) is preconcentrated at the solid bismuth microelectrode surface via the formation of electroactive complexes with cupferron from a solution of 0.1-mol L−1 acetate buffer, pH = 4.6 at a potential of −0.4 V. The linearity of the calibration graph is in the V(V) concentration range from 8 × 10−10 to 1 × 10−7 mol L−1 with a preconcentration time of 1 min. The limit of detection (calculated as 3 σ) is 2.5 × 10−10 mol L−1 for a preconcentration time of 1 min. It was also demonstrated that significant improvement in analytical parameters was achieved as a result of the activation of the solid electrode surface at a potential of −2.5 V for 2 s. The developed procedure is highly selective for the presence of foreign ions and organic compounds in tested samples. The accuracy of the recommended procedure was checked using SPS-WW1 waste water-certified reference materials of a complex composition, in which the concentration of V(V) determined by the proposed method was 95.1 ± 1.6 ng mL−1. Moreover, in keeping with the outlined procedure, river, tap and rain water samples were analyzed without any pretreatment, and recovery values from 96% to 106% were obtained. [ABSTRACT FROM AUTHOR]

• Cupferron can selective flotation separation of smithsonite from calcite. • Cupferron are preferentially adsorbed on the surface of smithsonite. • Stronger adsorption of cupferron on the surface of smithsonite than calcite. • An adsorption model are finally obtained. Considering that smithsonite has a similar crystal structure to calcite, more selective collectors are required to achieve its flotation separation. In this study, a new collector, cupferron, was used for the selective flotation of smithsonite from calcite. The selective mechanism of the effect of cupferron was investigated by FTIR analysis, zeta potential experiments, adsorption measurements, and DFT studies. Results of the microflotation test showed that the flotation recovery of smithsonite was 90.45 % at pH 8.0 with 10 × 10−4 mol/L of cupferron, whereas the flotation recovery of calcite was lower than 15.00 %. The FTIR results demonstrated that the cupferron was chemisorbed on the surface of smithsonite through a five-membered chelate ring formed with zinc atoms, whereas the adsorption on the surface of calcite was weak. The results of the zeta potential test further indicated that the cupferron was adsorbed selectively on the surface of smithsonite, whereas almost no adsorption was observed on the surface of calcite. In addition, the adsorption amount test results illustrated that the adsorption amount of cupferron on the surface of smithsonite was higher than that on the surface of calcite, which led to the difference in the flotation recovery of smithsonite and calcite under the same conditions. The results of the DFT study proved that the adsorption energy of cupferron acting on the surface of smithsonite is lower than that on the calcite surface. Moreover, the stronger covalent nature of Zn-O 2 bonds than Ca-O 2 bonds is responsible for the selective collection of smithsonite from calcite by cupferron. Therefore, cupferron can be applied as a potential collector for the flotation separation of smithsonite from calcite. Meanwhile, this study also provides a reference for the development of collectors for the flotation separation of smithsonite and calcite. [ABSTRACT FROM AUTHOR]

This paper presents for the first time the use of an environmentally friendly solid bismuth microelectrode for the voltammetric quantification of V(V) in natural water samples. These studies were designed to replace the film bismuth electrode that had been introduced to eliminate the conventional sensors based on highly toxic mercury. In the proposed procedure, V(V) is preconcentrated at the solid bismuth microelectrode surface via the formation of electroactive complexes with cupferron from a solution of 0.1-mol L−1 acetate buffer, pH = 4.6 at a potential of −0.4 V. The linearity of the calibration graph is in the V(V) concentration range from 8 × 10−10 to 1 × 10−7 mol L−1 with a preconcentration time of 1 min. The limit of detection (calculated as 3 σ) is 2.5 × 10−10 mol L−1 for a preconcentration time of 1 min. It was also demonstrated that significant improvement in analytical parameters was achieved as a result of the activation of the solid electrode surface at a potential of −2.5 V for 2 s. The developed procedure is highly selective for the presence of foreign ions and organic compounds in tested samples. The accuracy of the recommended procedure was checked using SPS-WW1 waste water-certified reference materials of a complex composition, in which the concentration of V(V) determined by the proposed method was 95.1 ± 1.6 ng mL−1. Moreover, in keeping with the outlined procedure, river, tap and rain water samples were analyzed without any pretreatment, and recovery values from 96% to 106% were obtained.

A radiochemical method was developed for the accurate 55Fe determination in various radioactive waste, in particular samples contaminated with 241Pu. It consisted of three purification steps based on first ammonium hydroxide precipitation, and then anion exchange separation followed by TRU®-based extraction chromatography. It was characterized by an iron recovery yield of about 80% for all the studied samples and a 60Co decontamination factor of 106. In comparison to a standard protocol based on iron cupferrate extraction in chloroform, an improvement of a 30-fold factor was achieved towards plutonium. The developed TRU®-based procedure was validated by participating in interlaboratory exercises. [ABSTRACT FROM AUTHOR]

An analytical procedure regarding the trace determination of molybdenum in natural water samples by adsorptive stripping voltammetry (AdSV) using the in situ plated lead film electrode (PbFE) was described. The method is based on adsorptive accumulation of the Mo(VI)-cupferron complex at the PbFE surface. The optimum analytical conditions include the supporting electrolyte containing 0.2-mol L−1 acetic buffer pH = 5.3, 1.45 × 10−4-mol L−1 Pb(II), and 2.0 × 10−4-mol L−1cupferron. A linear response of Mo(VI) in the concentration range of 3.0 × 10−8 to 1.0 × 10−6 mol L−1 (r = 0.997) was obtained with detection limit of 9.0 × 10−9 mol L−1 using accumulation time of 50 s. The selectivity of the method was determined by investigating how the presence of foreign ions affects the determination of molybdenum. The interferences of surface-active substances and humic substances on the molybdenum voltammetric signal were precisely examined and effectively minimized by preliminary mixing with Amberlite XAD-7 resin. The application of the proposed procedure to the analysis of natural water samples was validated by the determination of molybdenum in certificate reference materials SPS-SW1 surface water, Bystrzyca river, tap, and mineral water. [ABSTRACT FROM AUTHOR]

The decommissioning and dismantling of nuclear plants and the subsequent management of the wastes require a large number of radiochemical analyses in the timeline of the operations. Validated analytical methods for radionuclides measurements are employed to ensure reliable sample characterizations. The radioactivity of the samples, which induces handling and shipment constraints, and the use of harmful chemical reactants in some analytical procedures, are among the motivations to use miniaturized techniques that would considerably lower the amounts of samples and chemicals. Moreover the decrease of the analytical time is a major concern considering the increasing demand for radiochemical analyses. The purpose of this work is to develop a microsystem-based protocol for the recovery of 55Fe from samples. Analytical solvent extraction protocols adapted to co-flow glass microsystems, were developed and tested on iron extraction into ethyl acetate. A first extraction protocol consists of the partitioning of the Fe(cupferrate)3 chelate, from the aqueous phase to the organic phase. A second extraction protocol is based on the reactive transfer of iron using the cupferron in the organic phase. The two protocols were tested on a single Y-junction and a double stage Y-junction glass microsystems. After optimization of the liquid flow rates, the iron extraction was achieved within about 2 s or less. While the best extraction yield of (60.3 ± 4.9) % was obtained with the former protocol in the double stage Y-junction, higher values of (83.1 ± 5.2) % and (81.7 ± 2.0) % were obtained with the single and double stage microsystems, respectively, with the second protocol. These last results compare well with the yield of (93.0 ± 2.3) % measured in batch and could even be optimized by using slightly longer microchannels. Such microsystem-based extractions will be further applied to the analysis of 55Fe by liquid scintillation. [ABSTRACT FROM AUTHOR]

Electrochemical 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. [ABSTRACT FROM AUTHOR]

Abstract Two novel mixed-ligand complexes of lead(II), [Pb(Cup) 2 (Phen)] 2 ](DPE) (1) and [Pb(Cup)(ONO 2)(Phen)] (2) (Cup = cupferronato, Phen = 1,10-phenanthroline, and DPE = 1,2-di(4-pyridyl)ethylene), were synthesized in the presence of common bridging ligands which are usually used in synthesis of lead(II) coordination polymers as well as utilization of Cup and Phen as O,O′- and N,N′- chelates, respectively. Structural features of 1 and 2 in solution were investigated by 1H and 13C NMR experiments. The accurate assignment of these signals was inferred from a series of 1H–1H COSY, 1H–13C HSQC, and 1H–13C HMBC spectra. The solid-state structures of 1 and 2 were also investigated via single crystal XRD. By considering the obtained structural parameters, the coordination of 1 is hemidirected while 2 is suggested to be holodirectional. Additionally, complex 1 consist of dimers which are further associated via π-π stacking to a one-dimensional coordination polymer while complex 2 forming a step-like one-dimensional chain by an intermolecular interaction between each molecule and two nitrato groups of the two adjacent molecules. Both complexes showed significant antibacterial and antifungal characteristics in disc diffusion tests and they could be considered as new potent antimicrobial material. Graphical abstract Image 1 Highlights • Two novel mixed-ligand complexes of lead(II) were prepared. • The structures in solution were investigated by different NMR spectroscopies. • The molecular structures showed hemidirected and holodirected coordinations. • 1 consists of associated dimers via π-π stacking and forms 1D coordination polymer. • Complex 2 forms a step-like one-dimensional chain. [ABSTRACT FROM AUTHOR]

Graphical abstract 3D-QSAR methods were innovatively applied to correlate the field-based descriptors with the separation efficiencies of substituted cupferrons. Highlights • 3D-QSAR first introduced into the structure-activity relationship of flotation collectors. • Hydrophobic effect, steric effect and electrostatic interaction considered simultaneously. • Theoretically predicted separation efficiencies match with experimentally observed values. • Novel cupferron-based molecules with potentially higher performance proposed. Abstract Three-dimensional quantitative structure-activity relationship (3D-QSAR) methods were innovatively introduced into the structure-performance study of flotation collectors using topomer comparative molecular field analysis (Topomer CoMFA) and comparative molecular similarity indices analysis (CoMSIA). A total of eighteen cupferron derivatives was used to build up the 3D-QSAR models. The resultant Topomer CoMFA and CoMSIA models are both statistically significant. The Topomer CoMFA model yielded the non-cross-validated correlation coefficient (r 2) and the leave-one-out correlation coefficient (q 2) of 0.931 and 0.707, respectively. The corresponding r 2 and q 2 of the CoMSIA model were 0.816 and 0.651, respectively. The theoretically predicted separation efficiencies are in excellent agreement with the experimentally measured values, validating the high predictive ability of the 3D-QSAR models. Valuable information concerning the hydrophobic, steric and electrostatic properties of substituted cupferrons has been obtained and analysed in detail. The 3D-QSAR contour maps indicate that the aliphatic chains with significant hydrophobicity together with electron rich groups at 4-position of the benzene are of utmost importance for the flotation performance of substituted cupferrons. The addition of the electron-withdrawing group to the 2, 3-positions of the benzene ring is undesirable for enhancing the separation efficiencies. Structural modification of substituted cupferrons has been evaluated and novel cupferron derivatives with theoretically improved separation efficiency have been proposed. Despite the fact that 3D-QSAR methods have matured into a wide variety of applications such as drug discovery, catalyst science, environmental science, pesticide science, computational toxicology and material science, this work is the first attempt of introducing 3D-QSAR into the structure-activity relationship of flotation collectors. The generated 3D-QSAR models in this work could provide a new perspective on the structure-activity relationship of flotation collectors and potentially hold great promise for the rational design, selection and prediction of untested flotation collectors through virtual screening of chemical database. [ABSTRACT FROM AUTHOR]

• A novel multiple ligand complex collector Pb–BHA–CPF was designed. • Pb–BHA–CPF exhibited stronger collecting ability at a lower reagent dosage. • Pb–BHA–CPF may possessed molecular structure of Pb(L 1) n (L 2) m. • Pb–BHA–CPF had stronger electrostatic attraction and chemical adsorption ability. Pb–BHA (lead complexes of benzohydroxamic acid) as metal-group collectors have been recently used for mineral flotation collector. This complex possessed high selectivity but low flotation efficiency due to extensive dosage. To improve the flotation performance of Pb–BHA, we designed a novel multiple ligand complex collector assembled from Pb2+, BHA, and cupferron (CPF) (i.e., Pb–BHA–CPF). The flotation performance of Pb–BHA–CPF was studied through the flotation test. The structure of Pb–BHA–CPF was analyzed by Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS), and the adsorption mechanism of Pb–BHA–CPF at the solid–liquid interface was investigated and discussed through the zeta potential, FTIR, XPS, and crystal chemistry analyses. Based on the results, Pb–BHA–CPF exhibited stronger collecting ability and selectivity than Pb–BHA at a lower reagent dosage. Structural analysis revealed that BHA and CPF could coordinate with Pb2+ to form novel multiple ligand complexes with lead groups, and CPF may replace BHA to form the molecular structure of Pb(L 1) n (L 2) m (HL 1 = BHA, NH 4 L 2 = CPF, n > m). The adsorption mechanism analysis indicated that Pb–BHA–CPF had stronger electrostatic attraction than Pb–BHA and showed stronger chemical adsorption strength with the active oxygen atoms on the mineral surface. This study proposed a method for designing and assembling a multiple ligand metal-group collector. [ABSTRACT FROM AUTHOR]

Background: The present study describes glycerosomes (vesicles composed of phospholipids, glycerol and water) as a novel drug delivery system for topical application of celecoxib (CLX) and cupferron (CUP) compound. Aim: The goal of this research was to design topical soft innovative vesicles loaded with CLX or CUP for enhancing the efficacy and avoiding systemic toxicity of CLX and CUP. Methods: CLX and CUP loaded glycerosomes were prepared by hydrating phospholipid-cholesterol films with glycerol aqueous solutions (20-40%, v/v). Box-Behnken design, using Design-Expert® software, was the optimum choice to statistically optimize formulation variables. Three independent variables were evaluated: phospholipid concentration (X1), glycerol percent (X2) and tween 80 concentration (X3). The glycerosomes particle size (Y1), encapsulation efficiency percent (Y2: EE %) and drug release (Y3) were selected as dependent variables. The anti-inflammatory effect of CLX and CUP glycerosomal gel was evaluated by carrageenan-induced rat paw edema method followed by histopathological studies. Results: The optimized formulations (CLX2* and CUP1*) showed spherical morphology under transmission electron microscopy, optimum particle size of 195.4 ± 3.67 nm, 301.2 ± 1.75 nm, high EE of 89.66 ± 1.73%, 93.56 ± 2.87%, high drug release of 47.08 ± 3.37%, 37.60 ± 1.89% and high cumulative amount of drug permeated in 8 h of 900.18 ± 50.24, 527.99 ± 34.90 µg.cm−2 through hairless rat skin, respectively. They also achieved significant remarkable paw edema inhibition in comparison with the control group (p < .05). Conclusion: Finally, the administration of CLX2* and CUP1* loaded glycerosomal gel onto the skin resulted in marked reduction of edema, congestive capillary and inflammatory cells and this approach may be of value in the treatment of different inflammatory disorders. [ABSTRACT FROM AUTHOR]

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Large concentrations and oscillations of ammonium nitrogen (NH4+-N) in municipal landfill leachate pose considerable constraints to its further treatment in central wastewater treatment plants. The aim of this study was to evaluate and optimize two technologies for the pre-treatment of 600 L/day of landfill leachate: in particular, to optimize their operational conditions for NH4+-N removal up to a level appropriate for discharge to sewers, i.e. <200 mg/L. Both technologies were based on a sequencing batch reactor (SBR), with two different biomass processes: (A) SBR with dispersed/ flocculated biomass and (B) SBR with biomass attached to carriers. The results revealed that both technologies successfully reduced the NH4+-N from 666 mg/L (on average) at the inflow to below 10 mg/L at the outflow with alkalinity adjustment in a 12-hour cycle. Both technologies achieved 96% removal efficiencies for NH4+-N. However, SBR with dispersed biomass showed higher flexibility under varying conditions due to the shorter adaptation time of the biomass. [ABSTRACT FROM AUTHOR]

In this paper, the interaction of cupferron (Cup) and lead (II) complex [Cup-Pb (II)] with chondroitin sulfate (CS) was investigated by linear sweep voltammetric method. In the selected medium of pH 5.5 (acetic acid-hexamine buffer solution), Cup can interact with Pb (II) to form a stable complex of [Cup-Pb(II)], which has a sensitive second order derivative polarographic reductive peak at -0.64V (vs.SCE). After the addition of CS into Cup-Pb (II) complex solution, the reductive peak current decreased without any shift of the peak potential and no new peak appeared, which indicated that an unelectroactive supramolecular complex of CS with [Cup-Pb(II)] was formed. The binding reaction conditions were carefully investigated. Under the optimal conditions, the interaction mechanism was discussed. The decrease of reductive peak current was directly proportional to the CS concentration, thus a new quantitative determination method for CS was established with the linear regression equation as ΔIp″(nA)=36.97 C/mg L-1+12.45 (n=10, γ=0.995). The effects of other substances on the determination were carefully investigated and three synthetic samples were determined with satisfactory results. The binding constant (βs) and the binding number (m) of CS with [Cup-Pb(II)] complex were calculated from the voltammetric data with the results as βs=1.89×1010 and m≈2.5.

A simple, fast, and inexpensive voltammetric method for the simultaneous determination of trace bismuth(III) and lead(II) using (Hg(Ag)FE) as a working electrode was optimized. For adsorptive stripping voltammetric determination of Bi(III) and Pb(II) in a single scan, the cupferron was applied as a complexing agent. Experimental conditions under which these elements can be simultaneously detected include 0.1 mol L−1 acetate buffer (pH = 4.6), 1 × 10−4 mol L−1 cupferron, accumulation potential −0.05 V, and accumulation time 30 s. The experiments were performed without deaeration of the solutions. The calibration graph was linear from 2 × 10−9 mol L−1 to 1 × 10−7 mol L−1 for the simultaneous presence of bismuth and lead. The detection limits for preconcentration time of 30 s were 6.7 × 10−10 mol L−1 and 8.8 × 10−10 mol L−1 for bismuth and lead, respectively. The application of this procedure was tested by analyzing certified reference material (SPS-WW1 Wastewater) and Lake Zemborzyce water (eastern areas of Poland). [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

In the present study, nanocrystallite copper ferrite (CuFeO) has been obtained via two different methods. In the first method, CuFeO with an average particle size of 7.6 ± 0.5 nm was synthesized by pyrolysis of iron and cupferron as a chelating agent. In the second method, CuFeO nanoparticles with an average particle size of 22.3 nm were synthesized by combined microemulsion and homogenous precipitation methods. The effective parameters for the synthesis procedures were determined and optimized using L and L Taguchi designs. Different techniques to characterize the structure and morphological properties of nanoparticles are X-ray diffraction, thermogravimetric analysis, scanning electron microscopy, Brunauer-Emmett-Teller, transmission electron microscopy, Dynamic light scattering, and elemental micro analysis. Crystal violet (CNHCl) as a model pollutant and UV lamp as an energy source were applied for the investigation of the photocatalytic activity of nanocrystalline CuFeO powders. The 97 % degradation of crystal violet could be obtained around 100 min. [ABSTRACT FROM AUTHOR]

A sequential voltammetric procedure for the determination of uranium, cadmium and lead was investigated at an ex situ bismuth film electrode (BiFE). First, the adsorptive stripping voltammetry was applied to assay the U(VI)-cupferron complex in the differential pulse mode (detection limit of 1.0 µg L−1, 200 s accumulation time). Through the manipulation of the same aliquot of the sample, efforts were made to quantify cadmium and lead by square wave anodic stripping voltammetry. Detection limits of 2.03 µg L−1 for Cd (II) and 2.43 µg L−1 for Pb (II) were calculated (100 s accumulation time). The methodology was successfully applied to phosphate fertilizer samples after open vessel wet decomposition (HNO3/H2O2). The following value ranges were evaluated: U (VI) 37.2-150 mg kg−1, Pb (II) 78.3-204 mg kg−1 and Cd (II) 44.1-71.6 mg kg−1. Validation was performed by using the standard reference materials SRM-695 - phosphate fertilizer - and SRM-1643e - water. [ABSTRACT FROM AUTHOR]

Surface catalytic polarograpfic wave in vanadium(V)–cupferron system has been studied in the buffer media with pH 5 ÷ 7.5. The catalytic wave is observed at − 0.6 ÷ − 0.7 V (SCE), and it could be enhanced by addition of quaternary ammonium salts. This fact implies that catalytically active vanadium species are anionic. As the height of this wave is proportional to vanadium concentration, it may be useful as an analytical signal. Adsorbed anionic vanadium(II) complex with cupferron is supposed to be a catalyst in this process. A peak shaped wave at more negative potentials is assumed to be a result of catalytic action of vanadium(II) hydroxide. Some kinetic parameters of the catalytic wave in vanadium–cupferron system are presented. The mechanism of catalytic reaction has been considered, and the rate constant of the surface chemical reaction between adsorbed vanadium(II) and cupferron has been evaluated: k = (3 ± 1)·10 6 cm 3 ·mol − 1 ·s − 1 . pH dependence of k has not been observed; it implies that no prior protonation is encountered. The catalytic reduction of cupferron and its direct electrochemical reduction differ in some important aspects such as number of electrons transferred or presence of prior protonation reaction. [ABSTRACT FROM AUTHOR]

A method for the determination of cadmium by flame atomic absorption spectrometry (FAAS) after its preconcentration onto a column containing silica gel modified with cupferron was developed. The pH, amount of adsorbent material, concentration of eluent, volume of sample and amount of Cd were optimized. The effect of several foreign ions was also investigated and showed that the retention of cadmium depended on the amounts of Zn(II) and Cu(II) present and that these interferences could be overcome by using a 0.05 mmol KI. An enrichment factor of up to 30 was obtained , the LOD was 0.5 µg L-1 (3sigma) and the LOQ was 2.0 µg L-1 (10sigma) with rsd of 1.1% (n = 10). The accuracy of the proposed method was ascertained by using certified reference material and the obtained result (3.93 ± 0.01 µg g-1) agrees with the certified value (4.15 ± 0.38 µg g-1). The determination of Cd in nail polish showed quantitative recoveries for the spiked samples. The proposed method is characterized by simplicity, efficiency and low cost.

The determination of trace gallium using adsorptive stripping voltammetry at an in situ plated bismuth film electrode was described. The method was based on simultaneous film formation and the Ga(III)–cupferron complex preconcentration at −0.65 V and its cathodic stripping during the potential scan. The effect of Bi(III) and cupferron concentration, the influence of deposition potential and time, and the scan rate on the determination of Ga(III) were studied. A linear response in the concentration range of 3×10 −10 to 3×10 −7 mol L −1 ( r =0.998) was obtained with detection limit of 1.05×10 −10 mol L −1 using accumulation time of 180 s. Finally, the bismuth film electrode was successfully applied for the determination of Ga(III) in certified reference material seawater NASS-5 with satisfactory results. [ABSTRACT FROM AUTHOR]

Dynamic covalent libraries (DCLs) of quaternary ammonium cations were set up by reversible nucleophilic substitution (SN2′ and SN2) exchange reactions of ammonium salts and tertiary amines. The reactions were conducted at 60 °C to generate thermodynamically and kinetically controlled mixtures of quaternary ammonium compounds and tertiary amines, and were accelerated by using iodide as a nucleophilic catalyst. Microwave irradiation was used to assist the exchange reaction between the pyridinium salts and pyridine derivatives. Finally, experiments towards the generation of dynamic ionic liquids were performed. The results of this study pave the way for the extension of dynamic combinatorial chemistry to nucleophilic substitution reactions. [ABSTRACT FROM AUTHOR]

A new tin complex, [µ-(4-bpdb){MeSn(cupf)}] ( 1), was prepared by reacting dimethyltin(IV) dichloride, with 1,4-bis(4-pyridyl)-2,3-diaza-1,3-butadiene (4-bpdb) and cupferron in a fast and facile process. The complex was fully characterized based on its H and C NMR, IR, and UV spectra and elemental analysis. The nanostructure of the prepared compound was synthesized by the sonochemical method. The new nanostructure was characterized by scanning electron microscopy (SEM), X-ray powder diffraction (XRD), IR spectroscopy and elemental analysis. Thermal stability of single crystalline and nanosize samples of the prepared compound was studied by thermal gravimetric and differential thermal analysis. The prepared complexes, as bulk and as nanoparticles, were utilized as a precursor for preparation of SnO nanoparticles by direct thermal decomposition at 600 °C in air. The morphology and size of the SnO nanoparticles were determined by scanning electron microscopy, XRD and IR spectroscopy and the results showed that particle size of the SnO nanoparticle depend on the initial particles size of 1. Photoluminescence properties of the nanostructured and crystalline bulk of the prepared complex and SnO nanoparticles core of them were investigated. [ABSTRACT FROM AUTHOR]

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 −6 M, both V(IV) and V(V) cupferron complexes showed a single cathodic peak at −0.576 V 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 0.09 nM, and the peak current was linear in the concentration range 0.01–0.9 µM 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 10–60 µM V(IV) and V(V) ions were determined with LOD of 1.2 and 1.1 µM, respectively. The developed method was successfully applied to 10,00,000 fold diluted Benfield sample and 0.6227 M 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 22.52 µM and 38.91 µM, respectively, giving total vanadium concentration of 0.6143 M in Benfield sample. [ABSTRACT FROM AUTHOR]

We report a very sensitive stripping voltammetric procedure for determination of ultra-trace quantity of U(VI) in water samples. A very low detection limit was achieved owing to the application of a new construction of the voltammetric electrode cell with two built-in working electrodes that differed significantly in their surface area. The procedure was based on the double adsorptive accumulation of the U(VI)-cupferron complex onto two lead film working electrodes. Under optimal conditions the detection limit for accumulation time of 120 s for the big electrode and 120 s for the small electrode was about 3.1 x 10-11 mol L-1, whereas for accumulation time of 480 s for the big electrode and 240 s for the small electrode it was about 1.1 x 10-11 mol L-1. The proposed method was successfully validated using certified reference material seawater NASS-5. [ABSTRACT FROM AUTHOR]

This article describes a differential pulse adsorptive stripping voltammetric method for the trace determination of gallium in environmental water samples. It is based on the adsorptive deposition of the complex Ga(III)-cupferron at the hanging mercury drop electrode (HMDE) at −0.4 V (versus Ag/AgCl) and its cathodic stripping during the potential scan. The method was optimized as concerns the main electrochemical parameters that affect the voltammetric determination (supporting electrolyte, pH, cupferron concentration, deposition potential and time). The calibration graph is linear from 5 × 10−10to 5 × 10−7mol L−1with a detection limit calculated as 1.3 × 10−10mol L−1for deposition time of 30 s. The influence of interfering substances such as surfactants and humic substances present in the matrices of natural water samples on the Ga(III) signal was examined and a satisfying minimization of these interferences was proposed. The procedure was applied to direct determination of gallium in environmental water samples. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Abstract: Competitive Ligand Exchange–Adsorptive Stripping Voltammetry (CLE–AdSV) was used for determining the speciation of aluminium in commonly consumed beverages (water, tea, infusion, coffee, orange juice, tomato juice, beer and red wine). Aluminium determination involves the adsorption of Al-complexes with the ligand cupferron onto a hanging mercury drop electrode. All samples were studied at pH 6.5 with an accumulation step at –0.60V (all potential values in the paper are given versus the Ag/AgCl, [KCl]=3M reference electrode) during 60s, and a final cupferron concentration of 4×10−4 M. These conditions were used to establish (i) the concentration of electro-labile aluminium, (ii) the range of ligand concentrations and (iii) the conditional stability constants of beverage samples using titration procedures. The results based on Ruzic plots were compared to computer simulation with Visual MINTEQ. This comparison suggests that labile monomeric Al-forms and soluble organic complexes of low molecular weight can be quantified by the CLE–AdSV procedure. Overall the relative uncertainties on the determination of the electro-active Al fraction and the complexing parameters, i.e., concentration and conditional stability constant of natural ligands in the samples, are less than 15%. Thanks to these results, information on Al bioavailability in beverages was collected and discussed. This study also illustrates the value of computer simulations when complex, time-consuming voltammetric techniques are applied. [Copyright &y& Elsevier]

In this paper, the interaction of cupferron (Cup) and its lead(II) complex [Cup--Pb(II)] with chondroitin sulfate (CS) was investigated by the linear sweep voltammetric method. In the selected medium of pH 5.5 (acetic acid--hexamine buffer solution), Cup can interact with Pb(II) to form a stable complex of [Cup--Pb(II)], which has a sensitive second order derivative polarographic reductive peak at -0.64 V vs. SCE. After the addition of CS into a solution of the Cup--Pb(II) complex, the reductive peak current decreased without any shift of the peak potential and no new peak appeared, which indicated that a non-electroactive supramolecular complex of CS with [Cup--Pb(II)] was formed. The binding reaction conditions were carefully investigated. The interaction mechanism under the optimal conditions was discussed. The decrease of reductive peak current, Ip", was directly proportional to the CS concentration, thus a new quantitative determination method for CS was established with the linear regression equation as ΔIp" / nA =36.97(c / mg L-1) + + 12.45 (n = 10, γ = 0.995). The effects of other substances on the determination were carefully investigated and three synthetic samples were determined with satisfactory results. The binding constant (βs) and the binding number (m) of CS with [Cup--Pb(II)] complex were calculated from the voltammetric data with the results βs = 1.89 x 1010 and m ≈ 2.5. [ABSTRACT FROM AUTHOR]

A simple and sensitive adsorptive stripping voltammetry method was developed for determination of Zn using N-nitrozo-N-phenylhydroxylamine (cupferron) as a selective complexing agent. This complex absorbed on the hanging mercury drop electrode and created a sensitive peak current. The peak current and concentration of zinc accorded with a linear relationship in the range of 0.85-320 ng mL-1. The influence of pH and the nature of supporting electrolytes, concentration of ligand, preconcentration time and applied potential were investigated. The relative standard deviation at a concentration level of 50 ng mL-1 was 1.8%. The method was applied to the determination of zinc in city, river and mineral water samples, with satisfactory results. [ABSTRACT FROM AUTHOR]

Based on the interaction of cupferron and lead(II) complex [Cup-Pb(II)] with double-stranded DNA (dsDNA) a new voltammetric method for the detection of DNA was described in this paper. In pH 4.0 HAc-hexamine buffer solution, [Cup-Pb(II)] complex showed a sensitive second order derivative polarographic reductive peak at -0.554 V (vs. SCE). After the addition of dsDNA into [Cup-Pb(II)] mixture solution the reductive peak current decreased with the positive shift of reductive peak potential, which was the typical characteristic of intercalation mode. Under the optimum conditions, the decrease of reductive peak current was directly proportional to the dsDNA concentration in the range from 1.0 to 25.0 mg/L with the linear regression equation as ΔIp″ (nA) = 129.30 + 62.51 C (mg/L) (n = 13, γ = 0.991). The detection limit of 0.90 mg/L (3σ) and the relative standard derivation (RSD) of 2.43% for 10 parallel determinations of 10.0 mg/L dsDNA were found. The method was successfully applied to synthetic samples with good results, and the stoichiometry of dsDNA with [Cup-Pb(II)] complex was calculated by the voltammetic data with the binding number as 2 and the binding constant as 2.82 × 109. [ABSTRACT FROM AUTHOR]

This paper reports the use of an adsorptive voltammetric technique for Pb(II) determination using cupferron as a selective complexing agent. After accumulation of the complex onto a hanging mercury drop electrode, the electrode potential was scanned with differential pulse modulation and the reduction current of lead was observed at about −0.5 V. Under optimum conditions (5 × 10−4 mol L−1cupferron concentration, 0.1 mol L−1acetate buffer (pH 5.5), adsorption at −50 mV for 30 s) the detection limit was 5.1 × 10−10 mol L−1. The relative standard deviation of five measurements for low lead concentration was 3.1%. The accuracy of the method was tested by analysing certified reference material (SPS-WW1 Waste Water). Finally, the method was successfully applied to the determination of Pb(II) in river water samples without any pretreatments. [ABSTRACT FROM AUTHOR]