Electrochemical properties of silver–copper alloy microelectrodes for use in voltammetric field apparatus

Microelectrodes of silver–copper alloys have been evaluated for use in voltammetric analyses. Increased overpotential towards the hydrogen overvoltage reaction (HER) was found as a function of increased copper content in the silver. A study of oxidizing products by cyclic voltammetry (CV) in NaOH solution showed ten anodic and eight cathodic peaks which are described in the present paper. The behaviour of these alloy electrodes is somewhere between pure silver and pure copper electrodes. Differential pulse anodic stripping voltammetry (DPASV) was used to measure zinc, cadmium and lead in ultrapure water only (18 MΩcm), and good linearity was found for all metals (r ²=0.998) in the range of 0.5 to 5 ppb with a 600- to 1,200-s plating time. It was additionally found that cadmium and lead were better separated on the alloy electrodes compared to pure silver electrodes. Measurements of nickel were carried out on alloy electrodes by use of adsorptive differential pulse cathodic stripping voltammetry (Ad-DPCSV), and good linearity (r ²=1.000) was found in the range from 0.5 to 5 ppb with an adsorption time of 120 s. The alloy electrodes were also found to be sensitive to nitrate, and good linearity (r ²=0.997) was found in the range from 1 mg L⁻¹ to 100 mg L⁻¹ using differential pulse voltammetry (DPV) scanning from −450 mV to −1,500 mV. Addition of nitrate in ultrapure water afforded two different peaks related to the successive reductions of nitrate and nitrite. In ammonium buffer solution (pH 8.6) only one peak resulting from reduction of nitrate was observed. Furthermore, the use of alloy electrodes containing 17% Cu was tested in real samples, by installing it in a voltammetric system for monitoring of zinc and lead in a polluted river, the river Deûle, near the town of Douai in northern France. Results were found to be in agreement with parallel measurements carried out by ICP-MS.     

Synthesis,crystal structure,and electroluminescent properties of zinc and cadmium tetradentate azomethine complexes

Chemical and electrochemical syntheses of zinc(II) and cadmium(II) complexes based on tetradentate Schiff bases (H₂L¹ and H₂L²) resulting from condensation of 2-tosylaminobenzaldehyde with 3,6-dioxa-1,8-octanediamine or 4,9-dioxa-1,12-dodecanediamine were performed. The structure, composition, and properties of the complexes were studied by elemental analysis, IR, ¹H NMR, and UV spectroscopy, X-ray absorption spectroscopy, and X-ray diffraction. The zinc(II) and cadmium(II) complexes luminesce in a DMF solution in the blue spectral region (λ_PL = 425–433 nm), the photoluminescence quantum yield φ being 0.25–0.30. Multilayer zinc(II)- and cadmium(II)-based electroluminescent structures with green-blue emission of the exciplex nature were fabricated.     

Electrochemical Properties and Application of Mixed Silver‐Bismuth Electrodes

Electrochemical properties of silver electrodes with 2, 4, 6, 10 and 15% bismuth have systematically been investigated with cyclic voltammetry (CV), differential pulse voltammetry (DPV), and electrochemical impedance spectroscopy (EIS). Increased overpotential towards hydrogen evolution reaction (HER) was found as a result of increasing amount of added bismuth. This was also demonstrated in acid solution where zinc was successfully detected on mixed electrodes, but failed on pure silver electrodes. Formation and decomposition of oxide products formed on the different electrode surfaces were studied by cyclic voltammetry, and in addition to known species found on sliver, also peaks attributed to bismuth were achieved and examined. Zinc, cadmium, and lead were measured in the low μg/L range on the mixed electrodes, and good linearity (r²=0.998) was found for 2 to 10 μg/L. Lead was measured down to 0.1 μg/L. Further it was found in DPASV that the zinc peak significantly shifted towards a more negative value with increasing amount of bismuth in the silver electrodes. The same was also observed for cadmium and lead, but in a less extent. Finally a silver electrode containing 15% bismuth was used for continuous analyses in a polluted river for 6 weeks.     

Sampling and analytical methods for the determination of copper,cadmium, zinc,and nickel at the nanogram per liter level in sea water

Sea-water samples collected by a variety of clean sampling techniques yielded consistent results for copper, cadmium, zinc, and nickel, which implies that representative, uncontaminated samples were obtained. A dithiocarbamate extraction method coupled with atomic absorption spectrometry and electrothermal atomization is described which is essentially 100% quantitative for each of the four metals studied, has lower blanks and detection limits, and yields better precision than previously published techniques. A more precise and accurate determination of these metals in sea water at their natural ng l^-1 concentration levels is therefore possible. Samples analyzed by this procedure and by concentration on Chelex-100 showed similar results for cadmium and zinc. Both copper and nickel appeared to be inefficiently removed from sea water by Chelex-100. Comparison of the organic extraction results with other pertinent investigations showed excellent agreement.     

Electrochemical and chemical syntheses,structures, and optical properties of the zinc and cadmium complexes in the N,N,O,S-ligand environment

The chemical and electrochemical syntheses of the zinc (I) and cadmium (II) complexes are carried out on the basis of the tridentate Schiff base (H₂L), the condensation product of (2-tosylaminoaniline) N-(2-aminophenyl)-4-methylbenzenesulfunamide with 1-phenyl-3-methyl-4-formylpyrazole-5-thiol. The structures and compositions of the synthesized metallochelates are proved by the data of C, H, and N elemental analyses, IR spectroscopy, and ¹H NMR spectroscopy. X-ray absorption spectroscopy is used to determine the structure of the zinc complex. The binuclear structure of the cadmium complex is confirmed by the X-ray diffraction data (CIF file CCDC no. 1471159). The optical properties of H₂L and the zinc and cadmium complexes in dimethyl sulfoxide (DMSO) solutions are studied.     

Determination of cadmium,indium and zinc in nickel—base alloys by atomic absorption spectrometry with introduction of solid samples into furnaces

Atomic absorption spectrometry with an induction furnace is used for the determination of cadmium (0.002–2 μg g^-1), indium (0.6–350 μg g^-1) and zinc (0.05–26 μg g^-1) in 0.8–35 mg samples of nickel—base alloys dropped into the furnace. A resistively-heated furnace is employed for the determination of lower concentrations of indium (<0.6 μg g^-1). Standardised alloys were used for calibration. Accuracy, precision and detection limits are described for numerous nickel—base alloys. With alloys containing zinc, > 0.1 μg Cd g^-1 and >0.6 &,mu;g In g^-1, the relative standard deviations are 12%, 8% and 7%, respectively. Calculated detection limits for cadmium, indium and zinc are 2 ng g^-1, 10 ng g^-1 and 10 ng g^-1, respectively.     

Chronopotentiometric and controlled-potential electrolytic studies of the formation of intermetallic compounds in copper-zinc,platinum-zinc,and other amalgams

The behaviors of amalgams containing: copper and zinc; platinum and zinc; platinum and cadmium; silver and zinc; silver and cadmium; cadmium and copper; cadmium, copper and platinum; and silver, nickel and zinc were investigated by controlled-potential electrolysis and chronopotentiometry. Copper-zinc amalgams contain the compound CuZn, for which the solubility product at 25°C is equal to (3.8±0.6)×10^?6M², and also a soluble but sparingly dissociated compound that is richer in zinc. Platinum-zinc amalgams contain PtZn₂, PtZn₃ and PtZn₄ in metastable equilibrium. Gold-cadmium amalgams contain the compound AuCd, whose solubility product at 25°C is equal to (1.7±0.1)×10^?5M². Compound formation could not be detected in silver-zinc, silver-cadmium, cadmium-copper, platinum-copper or cadmium-copper-platinum amalgams, but there was an uncertain indication that silver-nickel-zinc amalgams might contain the first ternary intermetallic compound found in amalgams.     

Influence of Zn2+ ion on the organometallic l-alanine cadmium chloride single crystals

The single crystals of pure and zinc chloride-doped l-alanine cadmium chloride (LACC), an organometallic nonlinear optical material, are grown by a slow evaporation technique. The grown crystals were subjected to X-ray diffraction analysis, scanning electron microscopic study, and energy-dispersive analysis by X-ray and thermal studies. The second harmonic generation was confirmed by the Kurtz and Perry powder technique. The dielectric measurements were carried out for different frequencies at different temperatures. The second harmonic efficiency and dielectric constant increases significantly due to introduction of smaller ionic radii Zn²⁺ ion into the lattice of pure LACC crystal; so that the zinc chloride-doped LACC crystals are found to be potential material for nonlinear frequency conversion.     

Zinc(II) and cadmium(II) <Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>'-Bis(2-<Emphasis Type="Italic">N</Emphasis>-Tosylaminobenzylidene) diaminodipropyliminates: Syntheses,structures, and photoluminescence properties

Chemical and electrochemical syntheses of the zinc(II) and cadmium(II) complexes with the tetradentate Schiff base (H₂L), the condensation product of 2-N-tosylaminobenzaldehyde with diaminodipropylamine, are carried out. The structures, compositions, and properties of the synthesized metal complexes are studied by elemental analyses, IR spectroscopy, ¹H NMR, UV spectroscopy, X-ray absorption spectroscopy, and quantum-chemical calculations. The structure of the cadmium(II) complex is determined by X-ray diffraction analysis (CIF file CCDC no. 1446393). The cadmium(II) and zinc(II) complexes exhibit luminescence in a CH₂Cl₂ solution in the blue spectral range (λ_PL = 425–428 nm) with the photoluminescence quantum yields ? = 0.20 and 0.75, respectively.     

Meso位单取代卟啉及其配合物的合成、表征和光谱性质

设计合成了一系列新型的meso位N,N-二甲氨基苯基或N-苯基咔唑基单取代卟啉（5a~c）及其锌配合物（6a~c）,用高分辨质谱、¹H NMR、紫外-可见光谱及X射线单晶衍射方法等对结构进行了表征;研究了卟啉化合物及其配合物的热稳定性及荧光性质。结果表明,这些卟啉化合物及其锌配合物在400~410 nm之间具有强的吸收且具有很好的热稳定性,荧光量子产率在0.05~0.09;另外还分析了meso位不同取代基对光谱性质的影响。     

Characterization of Heavy Metal Air Pollution in Romania Using Moss Biomonitoring,Neutron Activation Analysis,and Atomic Absorption Spectrometry

ABSTRACT

Heavy metal air pollution in Romania was investigated by using passive moss biomonitoring. This study is a component of an international UNECE ICP Vegetation Program – moss survey. A total of 330 samples of Hypnum cupressiforme, Hylocomium splendens, Pleurozium schreberi, and other mosses were collected in Romania in the summer and autumn of 2010. The concentrations of aluminum, cadmium, chromium, copper, iron, lead, nickel, vanadium, and zinc were determined by graphite furnace/flame atomic absorption spectrometry and instrumental neutron activation analysis. The results were statistically processed to obtain spatial distribution maps of factor scores based on elemental concentrations in the moss, together with the spatial distribution maps of heavy metals in moss. The median concentrations of cadmium, 1.20?mg/kg dry weight, and lead, 30.8?mg/kg dry weight, were high compared with other European countries. The results revealed that the atmospheric deposition of these metals is a problem in north and northwest Romania.     

Ion-selective characteristics of heavy metal myristate liquid membrane electrodes

Liquid membrane electrodes of myristate soaps of heavy metals, namely copper, cadmium, zinc, nickel, cobalt, strontium and barium in a benzene-n-butanol mixture were prepared. Each electrode showed nernstian response in common metal ion test solution. The range of concentration of the test solution for the Nernstian behaviour lies between 10^?4 and 10^?1M. With a dissimilar metal ion in test solution the metal soap liquid membrane electrode indicates deviations from Nernst's equation depending on the nature of the metal ion, suggesting different selectivities for different ions. The selectivity ratios are therefore calculated.     

Effects of various elements on arsenic accumulation of the alga Dunaliella salina

The effect of 23 various elements (nitrogen, manganese, magnesium, molybdenum, zinc, selenium, gallium, nickel, cobalt, lithium, strontium, vanadium, tin, antimony, bismuth, cadmium, chromium, lead, iron, silver, copper, potassium and calcium) in water on growth and arsenic accumulation in Dunaliella saline was investigated. The order of growth inhibition of D. salina by these elements was Ag>Cd>Co>Ni>Cu>Zn>Fe>Sb>Ga>Cr>Bi>Sr>Mn>Sn>Se>Pb>V>Ca, Mg, Mo, K, Li. Arsenic accumulation in D. salina was unaffected by an increase in calcium and chromium. Also, the arsenic content in D. salina decreased at a potassium concentration of 100 mg dm^?3, and was also reduced by the addition of cadmium and nitrogen; however, it was increased by the addition of lithium at 100 mg dm^?3, tin, gallium, bismuth, strontium, vanadium, iron and manganese at 10 mg md^?3, lead, antimony, zinc, copper cobalt and nickel at 1 mg dm^?3, selenium at 0.1 mg dm^?3, and silver at 0.005 mg dm^?3, respectively. These results imply that arsenic accumulation by D. salina depends upon biological activity and physical adsorption.     

Electrodeposition of zinc + cobalt alloys.: Relation between the electrochemical response and the composition and morphology of the deposits

The electrodeposition of cobalt and zinc + cobalt alloy in aqueous chloride solution has been studied on vitreous carbon electrodes under different concentration conditions (total concentration of metallic ion 0.1 mol dm ⁻³, chloride ion 1 mol dm ⁻³, pH = 3), particularly during the initial stages of the deposition process. For the alloy a relation has been found between the shape of the current-time transients, the morphology of the deposits, the stripping analysis and the results of X-ray microanalysis. The different alloy phases present in the deposits were identified using X-ray microanalysis data, stripping voltammetry results and literature data.The results indicate that the electrocrystallization of cobalt is inhibited even at very low concentrations of zinc in solution: voltammetric and galvanostatic results indicate that the deposition potentials always correspond to more negative values than those for cobalt deposition. This inhibition depends strongly on both the metallic ion ratio in solution and the applied overpotential (or current density). For Zn(II)/Co(II) ratios greater than 1/9, low overpotentials (or low current densities) favoured homogeneous and compact deposits that were rich in zinc and were mainly composed of γ-phases of zinc + cobalt alloy. However, when high overpotentials or current densities were used and/or when the Zn(II)/Co(II) ratio was very low (< 1/9), dendritic and non-homogeneous cobalt-rich deposits were obtained.     

Synthesis,characterization, thermal,and redox properties of a vic-dioxime and its metal complexes

A new vic-dioxime ligand containing benzophenone hydrazone units, N′-(benzophenone hydrazone)glyoxime [LH₂] has been prepared from benzophenone hydrazone and anti-chloroglyoxime in absolute ethanol. Mononuclear nickel(II), cobalt(II), copper(II), zinc(II), and cadmium(II) complexes were also synthesized. Ligand and complexes were characterized by elemental analyses, FT-IR, ¹H NMR, and ¹³C NMR spectroscopy, magnetic moments, and DTA/TG techniques. On the basis of the magnetic and spectral evidences a square-planar geometry for Ni(II) and Cu(II) complexes, tetrahedral for Cd(II) and Zn(II) complexes, and octahedral for Co(II) complex were proposed. Redox behaviors of ligand and its complexes were also investigated by cyclic voltammetry at the glassy carbon electrode.     

Screen-printed electrodes incorporated in a flow system for the decentralized monitoring of lead,cadmium and copper in natural and wastewater samples

Mercury-based screen-printed electrodes (SPE) combined with square-wave anodic stripping voltammetry (SWASV) techniques for the analysis of copper, cadmium, lead, and zinc in different water samples have been applied. The detection system has been implemented in a flow cell and different experimental conditions have been tested in view of its application for in-situ monitoring. In particular, an acetate buffer together with a low chloride concentration (0.025?M NaCl) provided best performance and reproducible results. Additionally, the flow system was validated for the first time in terms of limits of detection, linearity, repeatability and recovery. Limits of detection of 2.8?µg?L^?1, 4.1?µg?L^?1, and 7.5?µg?L^?1 for cadmium, lead and copper respectively and repeatabilities lower than 10% (as RSD) were found. Good recoveries have been obtained for the three cations and in particular for copper, even in the presence of zinc. Finally, the method has shown its efficiency for the rapid screening of lead, cadmium and copper contained in both natural waters and wastewater samples.     

Properties of Zinc alloy electrodeposits produced from acid and alkaline electrolytes

Zinc–cobalt (Zn–Co) and zinc–nickel (Zn–Ni) alloy electrodeposits each prepared from acid and alkaline formulations were compared for their properties. Compared to alkaline baths, acid baths offer higher metal percent of the alloying element and higher current efficiency. In alkaline baths, the variation of metal percent in deposit with current density is less significant, but that of current efficiency with current density is more. Electrolyte pH does not change significantly in alkaline solutions compared to acid solutions. X-ray diffraction evaluation of Zn–Co deposits from both electrolytes indicated their presence in the η-phase, while Zn–Ni shows pure γ-phase for deposits obtained from alkaline solutions and the existence of γ-phase with traces of η-phase of zinc for deposits obtained from the acid electrolytes. Scanning electron microscope examination shows finer grain structure for deposits obtained from alkaline solutions, and atomic force microscope studies confirm their nanostructure with reduced surface roughness. Deposits obtained from the alkaline baths exhibited higher corrosion resistance probably due to their nanostructure.     

Determination of copper,nickel, and cadmium in sea water by apdc chelate coprecipitation and flameless atomic absorption spectrometry

Copper, nickel, and cadmium can be determined in 100 ml of sea water by coprecipitation with cobalt pyrrolidinedithiocarbamate and graphite atomizer atomic absorption spectrometry. Concentration ranges likely to be encountered and estimated (1 σ ) analytical precisions are 1–6 nmol kg^-1 (±0.1) for copper, 3–12 nmol kg^-1 (±0.3) for nickel and 0.0–1.1 nmol kg^-1 (±0.1) for cadmium. The technique may be applied to fresh-water samples with slight modification.     

Simultaneous Determination of Nickel and Cadmium by Adsorptive Stripping Voltammetry

A sensitive and fast method for the simultaneous determination of trace amounts of nickel and cadmium in real samples has been described using differential pulse adsorptive stripping voltammetry (DPASV) by adsorptive accumulation of the N,N′‐bis(salicylaldehydo)4‐carboxyphenylenediamine (BSCPDA)–complex on the hanging mercury drop electrode (HMDE). As supporting electrolyte 0.02 mol L^?1 ammonia buffers containing ligand has been used. Optimal analytical conditions were found to be: BSCPDA concentration of 42 μM, pH 9.6 and adsorption potential at ?50 mV versus Ag/AgCl. With an accumulation time of 20 s, the peaks current are proportional to the concentration of nickel and cadmium over the 1–180, and 0.5–200 ng mL^?1 with detection limits of 0.06 and 0.03 ng mL^?1 respectively. The sensitivity of method for determination of nickel and cadmium were obtained 0.54 and 0.98 nA mL ng^?1, respectively. The procedure was applied to simultaneous determination of nickel and cadmium in some real and synthetic artificial samples with satisfactory results.     

A Study of Nafion‐Coated Bismuth‐Film Electrode for the Determination of Zinc,Lead, and Cadmium in Blood Samples

In this article a sensitive differential pulse stripping voltammetry technique on Nafion‐coated bismuth‐film electrode (NCBFE) was studied for the simultaneous determination of zinc, cadmium, and lead ions in blood samples at ultra trace levels. The measurement results were in excellent agreement with those obtained from atomic absorption spectroscopy. Various operational parameters were investigated and discussed in terms of their effect on the measurement signals. Under optimal conditions, calibration curves for the simultaneous determination of zinc, cadmium, and lead ions were achieved, based on three times the standard deviation of the baseline, the limits of detection were 0.09 μg L^?1 for Cd(II), 0.13 μg L^?1 for Pb(II), and 0.97 μg L^?1 for Zn(II) respectively.