Trace Analysis of Heavy Metals with Two New Disodium Bisdithiocarbamates

Two chelating reagents, disodium N,N′-dibenzylethylenebisdithiocarbamate 1 and disodium piperazinebisdithiocarbamate 2, were synthesized and used to preconcentrate trace metals in aqueous samples. For analysis of Cu(II) using a UV-vis spectrometer, Beer's law was obeyed from 5.0 μg L^?1 to 6.0 mg L^?1 for reagent 1, and from 0.2 mg L^?1 to 6.0mg L^?1 for reagent. 2. The chelation ratio for reagent 1 to Cu(II) was determined to be 1:1, with a formation constant 1.0 × 10⁹ M^?l. The dependence of extraction and extraction efficiency of reagent 1 on pH was also studied with an atomic absorption spectrometer for nine heavy-metal ions-Cu(II), Fe(III), Pb(II), Co(II), Cr(VI), Ni(II), Zn(II), Mn(II) and Cd(II). Except Cr(VI) and Mn(II), the recovery yields of the other seven metal ions were almost quantitative at pH = 4 ? 6. The recovery was 82% for Cr(VI) at pH = 4 ? 5, and 52% for Mn(II) at pH = 6 ? 7.     

Synthesis of bidentate pyridylazo and thiazolylazo reagents and the spectrophotometric determination of copper in a flow-injection system

Some pyridylazo and thiazolylazo compounds were synthesized as spectrophotometric reagents for copper(II). The water-soluble bidentate ligand, 4-(3,5-dibromo-2-pyridylazo)-N-ethyl-N-(3-sulfopropyl)aniline (3,5-diBr-PAESA), provides the greates sensitivity, forming a 1:2 Cu:L in the presence of sodium dodecylsulfate. The molar absorptivity of the complex is 1.24 × 10⁵ l modl^?1 cm^?1 at 638 nm. Copper(II) (10–200 μg l^?1) is easily and quickly (60 h^?1) determined in a flow-injection system. Application to the determination of copper(II) in serum is described.     

The masking effect of iron(III) on the interference from nickel and copper in the determination of tellurium by hydride generation/atomic absorption spectrometry

Iron(III) can minimize the serious interferences from copper(II) and nickel(Il) on the determination of tellurium by hydride generation/atomic absorption spectrometry. The optimal concentrations were found to be 1 g l^?1 and 2 g l^?1 Fe (III) in 4.0 mol l^?1 HCl in presence of nickel (II) and copper (II), respectively. The signals were only 25 % lower in a solution of 1.6 g 1^?1 Ni(II) than for a nickel-free solution. For copper (II), reasonable sensitivity was retained in the presence of 100 mg l^?1 Cu(II).     

Continuous-flow extraction of organophosphorus pesticides coupled on-line with high-performance liquid chromatography

A continuous-flow extraction system coupled on-line with a high-performance liquid chromatograph with an ultraviolet detector is used to study the extraction of three organophosphorus pesticides (fenthion, azinphos methyl and diazinon) from aqueous samples with n-heptane as the organic solvent. Diazinon was not extracted significantly. The influence on the extraction of different parameters (coil length, flow rate and phase volume ratio) were studied. The calibration graphs are linear for 0.5–7 mg l^?1 and 8–20 mg l^?1 foor azinphos methyl where the percentage extraction (E%) is 90% and 70%, respectively, and up to 4 mg l^?1 for fenthion, where the E% is 33%. The detection limits and the relative standard deviations are 0.04 and 0.09 mg l^?1, and 3.4 and 5.3%, for azinphos methyl fenthion, respectively. Other pesticides and related compounds were found not to interfere. The sample throughput of this method was 15 h^?1.     

Flow-injection spectrophotometric determination of glucose in blood plasma with bindschedler's green leuco base as color reagent

The hydrogen peroxide produces in the oxidation of glucos in an immobilized glucose oxidase reactor is determined by using Bindschedler's green (leuco base) as color reagent with iron(II) as catalyst; the increase in the absorbance at 725 nm is measured. For 100-μl samples, calibration was almost linear in the range 0–2.5 mg l^?1 glucose; the relative standard deviation for 1 mg l^?1 glucose was 0.6% (n=10) and the detection limit (S/N= 2) was 0.02 mg l^?1. The injection rate was 20 h^?1. Glucose was determined satisfactorily in control sera and in real blood sera.     

Fluorescence spectra of the mixed crystal system anthracene-perdeuteroanthracene. Mixed exciton band

The fluorescence spectra of the mixed crystal system anthracene (A-h₁₀)-perdeuteroanthracene (Ad₁₀) have been studied over the full concentration range at temperatures between 1.6 and 77°K. There exists a collective (mixed) A-h₁₀-A-d₁₀ S₁ exciton band at all concentrations, the lower edge of which represents the emitting level for the intrinsic fluorescence at low temperatures. This edge shifts from 25097 cm^?1 in the neat A-h₁₀ crystal to 25156 cm^?1 in the neat A-d₁₀ crystal. The edge position is a non-linear function of the mixed crystal concentration. From that one gets the “critical” distances U_cr⁺ = 92 cm^?1 and U_cr^? = 131 cm^?1 between the molecular S₁ levels of a guest and the host anthracene (non-deuterated or deuterated), using a formula given by Lifshitz. For the critical distance U_cr⁺ one finds just a bound guest state above the host band, and for U_cr^?1 a bound guest state below the host band.The transition from the S₁ band edge to the S₀ ground state is always forbidden, in the same way as in the neat A-h₁₀ crystal. Only transitions to levels of intramolecular and lattice vibrations of the ground state have been observed. At all concentrations the fluorescence transitions from the lower S₁ band edge of the mixed crystal take place to the vibronic levels of both A-h₁₀ and A-d₁₀. The difference in the frequencies of equivalent intramolecular vibrations of A-h₁₀ and A-d₁₀ results in the appearance of vibronic doublets in the intrinsic fluorescence. The relative intensities of the two doublet components depend strongly on both concentration and temperature. This is due to the influence of quasi-resonance and exciton-superexchange upon the guest states inside the mixed exciton band.For all concentrations one observes two transitions originating from levels inside the S₁ exciton band.     

Preconcentration of antimony(III) from water with thionalide loaded on glass beads with the aid of collodion

2-Mercapto-N-2-naphthylacetamide (thionalide) loaded on glass beads with the aid of collodion is used for preconcentration of microgram levels of antimony(III) from aqueous solution. Antimony is quantitatively retained on the loaded beads from 0.4–0.8 mol l^?1 hydrochloric acid solutions; equilibration is achieved within 1 min. The retention capacity of the beads is 0.2 μml Sb g^?1 at 0.6 mol l^?1 hydrochloric acid. The maximum flow rate for quantitative retention is 1.27 ml min^?1 cm^?2. Antimony retained on the column is completely eluted with 10 ml of 6.0 mol l^?1 hydrochloric acid at flow rates<1.9 ml min^?1 cm^?2.     

Differential pulse voltammetric study of a typical anaerobic adhesive formulation coated on a glassy carbon electrode

The determination of copper (II) and iron (III) added to an anaerobic adhesive formulation was investigated by differential pulse voltammetry after application of a solution of the adhesive in acetone to a glassy carbon electrode. The best supporting electrolyte was 0.1 M sodium dodecyl sulphate, which ensured adequate surface contact with the adhesive coating. Under optimum conditions, copper (II) (as CuEDTA ^2?) could be determined at levels down to 0.1 mg l^?1 and iron (III) (in some complexed form) down to 2.0 mg l^?1. The method is also capable of detecting the presence of poly (ethylene glycol) dimethacrylate, cumene hydroperoxide and N,N-dimethyl-p-toluidine in a typical formulation.     

Preconcentration of copper,lead, cadmium and zinc ions from water with 2-mercaptobenzothiazole loaded on glass beads with the aid of collodion

2-Mercaptobenzothiazole (MBT) loaded on glass beads with the aid of collodion was prepared and used for selective preconcentration of μg l^?1 levels of copper(II) and lead from aqueous solutions. Copper and lead were quantitatively retained on the loaded beads from solutions of pH 5.0–6.0 and >5.0, respectively, while cadmium(II) and zinc(II) were retained at ? pH 6.0 and 7.0, respectively. The retention capacity of the loaded beads was ca. 108 μg Cu g^?1 (1.7 μmol g^?1) at pH 5.5 for beads of 0.3–0.4 mm diameter. The mole ratios of MBT to copper(II) and lead(II) were ca. 10 and 45, respectively, regardless of the amount of MBT loaded on the beads. Copper was completely retained on the column at a high flow rate (21.7 ml min^? cm^?2) and lead(II) at up to 12.7 ml min^? cm^?2. Cadmium(II) and zinc(II) were not retained quantitatively even at low flow rates (< 1.2 ml min^?1 cm^?2). Thus, selective preconcentration of copper and lead was achieved by passing the sample through the column at high flow rate at pH 6.5. The copper and lead retained on the column were complete eluted together with the collodion with 5 ml of MIBK by batch-mode elution, and determined directly by one-drop atomic absorption spectrometry. Copper(II) and lead(II) in several kinds of water were determined.     

Ion chromatographic determination of alkaline earth metals and some heavy metals

The method is described for ion chromatographic determination of Ba, Ca, Cd, Cu, Mn, Ni, Sr, Pb and Zn. Ethylenediammonium chloride or tartrate solutions are used as eluents with a suppressor column. The detection limits for the listed elements are (in μg l^?1): Ba 1.4, Ca 0.045, Cd 0.6, Cu 0.3, Mn 0.8, Ni 0.5, Pb 6.3, Sr 0.3, Zn 1.2. Relative standard deviations are 0.015–0.050 ar the 20 mg l^?1 level (n = 5, p = 0.95). Interferences are considered.     

Application of the iron(III)/3,4-dihydroxybenzaldehyde 4-nitrophenylhydrazone complex for the analysis of sulphide/fluoride/phosphate mixtures by spectrophotometry or atomic absorption spectrometry

3,4-Dihydroxybenzaldehyde 4-nitrophenylhydrazone reacts with iron(III) to form a red complex extractable into methyl isobutyl ketone. Sulphide, fluoride and phosphate inhibit the formation of the complex. Sulphide and fluoride are masked with Cu(II) and Al(III), respectively. These properties are used to determine sulphide (0.15–4 mg l^?1), fluoride (0.3–9 mg l^?1) and phosphate (0.3–8 mg l^?1) in mixtures by spectrophotometry or atomic absorption spectrometry.     

Determination of lead in whole blood with a simple flow-injection system and computerized stripping potentiometry

An automated (24 samples/hour) procedure is described for the determination of lead (0–1000 μg l^?1) in human blood based on flow-injection stripping potentiometry. The samples are diluted 20-fold with 0.5 M hydrochloric acid containing 100 mg l^?1 mercury and 40 μg l^?1 cadmium (II), and a 1.1 ml aliquot is injected into the flow system. With a mercury-coated carbon fibre as working electrode, lead (II) is determined by using cadmium (II) as internal standard and a calibration graph prepared from bovine blood. Analyses of two human blood reference samples yielded results of 335±37 and 691±24 μg l^?1 lead, the certified values being 332 and 663 μg l^?1, respectively.     

Inductively coupled plasma-atomic emission spectrometry method for determination of trace metals in alkaline-earth matrices after flotation separation

An inductively coupled plasma-atomic emission spectrometry (ICP-AES) method is developed for determination of Cd, Co, Cr, Cu, Ni, Tl and Zn in traces in calcite, CaCO₃, dolomite, CaMg(CO₃)₂, and gypsum, CaSO₄. Interferences of a Ca/Mg matrix on analyte intensities were investigated. The results reveal that Ca does not interfere with Cr, Ni and Zn, but tends to decrease the intensity of the other elements. Magnesium as a matrix element does not interfere on with Zn, but increases the intensities of Ni, Cr and Cu, and decreases the intensities of Cd, Co and Tl. To eliminate these matrix interferences on trace element intensities, a flotation separation method is proposed. Lead(II) hexamethylenedithiocarbamate, Pb(HMDTC)₂, is applied as a collector for flotation of trace elements from acidic solutions of mineral samples. The flotation of acidic aqueous solutions of calcite, dolomite and gypsum was performed at pH 6.0, using 10 mg l⁻¹ Pb and 0.3 mmol l⁻¹ HMDTC⁻ added to 1 l of solution tested. The method detection limits of analytes in different minerals range from 0.02 to 0.06 μg g⁻¹ for Cd, 0.04 to 0.10 μg g⁻¹ for Co, 0.03 to 0.13 μg g⁻¹ for Cr, 0.02 to 0.16 μg g⁻¹ for Cu, 0.09 to 0.30 μg g⁻¹ for Ni, 6.45 to 7.71 μg g⁻¹ for Tl and 0.18 to 0.20 μg g⁻¹ for Zn.     

Spectrophotometric Determination of Copper(II) as the Azide Complexes,in the Presence of Iron(III) Cations

Abstract

A method for the spectrophotometrio determination of copper(II), in the presence of iron(III) cations (excess), was stablished. The masking of iron is made with sodium fluoride salt in 50 % (v/v) water/acetone medium. In the recommended conditions, absorbances for cupric complexes are measured at 435 nm where molar absorptivity is 6.00 × 10³ 1 mol^?1 cm^?1.

The stable ayetern obeys Beer's law and is suitable for the copper determination in concentration range from 2.0 to 9.0 mg 1^?l. The iron(III) ion interference (until ca. 600 mg 1^?l) can be completely suppressed. The influence of diverse ions and several others factore were studied.

The results show that copper(II) can be accurately determined by azide apectrophotometric method, if the samples were suitablely treated by the recommended procedure.     

Isothiocyanate controlled architecture,spectroscopic, and magnetic behavior of copper(II) l–arginine complexes

Abstract

We synthesized an l–arginine complex with the formula [Cu(l–Arg)₂(NCS)]·(NCS)·H₂O (1) (l–Arg = l–arginine). Two cis-chelated l–arginine zwitterions form the basal plane, while the weakly N-bonded isothiocyanate is located at the apex of the distorted square pyramidal structure (τ?=?0.143). The non-coordinated NCS^? anions held layers together in a 3-D supramolecular network. The crystal structure, spectroscopic (FT–IR, Raman, NIR–Vis–UV, EPR) and magnetic properties of 1 have been compared with [Cu(l–Arg)(NCS)₂] (2). For 1, two absorptions are observed for ν(C?=?N) stretching vibrations, corresponding to NCS^? ions N-bonded to the central Cu(II) (2077?cm^?1) and in the lattice (2057?cm^?1). In 2 a single band is observed at 2102?cm^?1, indicating equivalent NCS^? ions in the structure. The EPR spectra of complexes show anisotropic signal with g_⊥ and g_|| 2.062, 2.235 (1), and 2.08, 2.225 (2) characteristic for cis-N₂O₂ and N₃O donor sets in the xy plane, respectively. The unpaired electron mainly occupies the d_x2–y2 orbital, also confirmed by the single envelope of d–d bands at ca. 16,000?cm^?1 for 1 and 16,500?cm^?1 for 2. The magnetic properties ofcompounds are characteristic of a very weak antiferromagnetic interaction with J?=??0.055?cm^?1 and J?=??0.096?cm^?1 for 1 and 2, respectively.     

Synthesis and properties of the copper(Ⅱ) complexes with stable radical

Four novel copper(Ⅱ) complexes have been synthesized,namely Cu(hfac)2NITPhNO2 (1),Cu(hfac)2NITPhCH3 (2),Cu(pfpr)2NITPhNO2,(3) and Cu(Pfpr)2NITPhCH3 (4),where hfac= hexafluoro-acetylacetonate,pfpr=pentafluoropropionate,NITR.=2-R-4,4,5,5-tetraniethyl-4,5-dihydro-1H-imidazolyl-1-oxyl-3-oxide.(R=4-nitrophenyl,4-methylphenyl).These complexes were rharicter-ized by elemental analyses,IR,electronic spectra and molar conductance.The temperature-dependent magnetic susceptibility of complexes 1 and 3 have been studied in the 4 300 K range,giving I he exchange integral J=10.56 cm-1 for complex 1 and J =-30.9 cm-1 for complex 3.     

Spectrophotometric determination of silver with 4-(3,5-dibromo-2-pyridylazo)-N,N-diethylaniline in the presence of sodium dodecylsulfate

The bidentate ligands, 4-(3,5-DiBr-PAEA) and 4-(3,5-DiBr-PAESA) react with silver(I) ion to form the Agl2 chelate in the presence of anionic or nonionic surfactant. The molar absorptivity at 600 nm is 80 000 l mol^?1 cm^?1 in 0.1% sodium dodecylsulfate solution. Optimum conditions for the spectrophotometric determination of silver in the range 0.1–1.0 mg l^?1 with 3,5-diBr-PAEA are reported. A flow-injection procedure is also presented.     

Iron(III) as releasing agent for copper interference in the determination of selenium by hydride-generation atomic absorption spectrometry

Iron(III0 has a very effective releasing effect on the depressive interference from copper(II) on the determination of selenium by hydride-generation atomic absorption spectrometry. In solutionwith 100 mg 1^?1 Cu(II), 10 μg 1^?1 Se(IV) and 2.0 mol l^?1 HCl, the absorbance obtained was much higher when 8 g 1^?1 Fe(III) was added than for any earlier releasing agent.     

The Study of Indirect Determination of Tiopronin by Extraction Flotation Copper(II) with an Ammonium Sulfate‐Water‐n‐Propyl Alcohol System

A novel method for indirect determination of tiopronin by extraction flotation of copper(II) with an ammonium sulfate‐water‐n‐propyl alcohol system was developed. The effects of different parameters, such as acidity, the amount of NH₄SCN and various salts on the flotation yield of Cu(II), have been studied to optimize the experimental conditions. Under the optimum conditions, Cu(II) is reduced to Cu(I) by tiopronin, and the resulting Cu(I) can react with SCN^? to form a white emulsion precipitate CuSCN. In the presence of (NH₄)₂SO₄, the mixture consisting of n‐propyl alcohol and water can be separated into an n‐propyl alcohol phase and a water phase. In the process of phase separation of n‐propyl alcohol from water, the precipitated CuSCN is extracted and stays in the interface of n‐propyl alcohol and water. The amount of tiopronin can be determined by measuring the flotation yield of Cu(II). The detection limit is 0.32 mg L^?1 and the linear range is maintained in the range of 0.40±13.0 mg L^?1 with a correlation coefficient of 0.9991. This proposed method has been successfully applied to the determination of tiopronin in tablets, urine and human plasma with satisfactory results.     

Trace Analysis of Lead and Copper Ions in Fish Tissue Using Paste Electrodes

Abstract

DNA was immobilized onto a carbon nanotube surface through cyclic voltammetry, in which paste electrode (PE) was subjected to lead and copper trace ion analysis. Optimized conditions for square‐wave stripping voltammetry were then searched. The results indicated three other linear working ranges—3–21 mg l^?1, 2–16 µg l^?1, and 3–17 ng l^?1 Pb(II) Cu(II)—within an accumulation time of 190 s in 0.1‐M ammonium phosphate electrolyte solutions of pH 10.0. At the optimized conditions, the detection limit (S/N) was pegged at 0.4 ng l^?1 (1.93×10^?12 M Pb(II) and 6.29×10^?12 M Cu(II)). And the relative standard deviation at 10 mg l^?1 Pb(II) and Cu(II) was a 0.074 and 0.069% precision, in 15 measurements. The method can be applied to assays of fish tissue.