Evidence for Reversible Anodic Stripping of Gallium Potentially Useful for the Rapid Assay Of Gallium

Abstract

Electrolyte compositions known to promote reversible a.c. polaro-graphic reduction of Ga(III) at the D.M.E. were examined for use in the ohase-selective anodic stripping [PSAS] of trace gallium using the micrometer hanging mercury drop electrode. Rapidly obtained, sharp gaussian peaks were recorded in the range < 1.0 p. p. m. Ga. These peaks which apparently are manifest only at high ionic strengths could serve as a convenient monitor of tissue-sequestered gallium.     

Activation analysis of mercury in high purity bismuth

A neutron activation method was developed for the determination of traces of mercury in high purity bismuth. After neutron irradiation at a flux of approx. 4.10¹¹ n/cm²/sec, mercury was separated from the matrix by displacement on metallic copper and subsequent distillation and amalgamation on silver foil. The γ-activity of the ¹⁹⁷Hg was counted in the 68–77 ke V region. The accuracy of the procedure was tested by an addition method of analysis. Bismuth samples with a mercury content in the 10 p.p.b. region were analysed.     

Speciation of Mercury in two Dimictic Lakes of North-East Germany During a Period of 600 Days

Abstract

The speciation of mercury was studied with respect to (a) dissolved atomic mercury, (b) dissolved ionic mercury, and (c) total mercury in two dimictic lakes of North-East Germany. Differential pulse anodic stripping voltammetry was used for the analyses. The results show that biological processes dominate the speciation. They are responsible for high concentrations of atomic mercury and also organomercury compounds. The oxidation of atomic mercury under environmental conditions in lake water is very slow, so that the equilibrium between Hg_aq° and Hg_aq and Hg_aq ²⁺ can only be established during long periods of decreased bioactivity, as in wintertime. The sedimentation of the detritus during summer leads to a very pronounced decrease of the overall mercury in the entire water body of the lakes.     

Determination of traces of antimony and tin in copper by anodic stripping voltammetry

The determination of antimony and tin impurities in copper by anodic stripping voltammetry on a hanging mercury drop electrode is described. Antimony and tin were previously separated from copper by distillation with hydrobromic acid or a mixture of hydrobromic acid and hydrochloric acid. The method was applied to the analysis of various high-purity copper samples, commercially available, showing satisfactory sensitivity and precision. The determination limit was about 1.4· 10^-9M for antimony and 7·10^-10M for tin in solution, for pre-electrolysis times of respectively 15 and 25 min; this corresponds to 0.8 p.p.b. of antimony and 0.3 p.p.b. of tin for a 2-g sample and a final volume of 10 ml after separation.     

Implications for Mercury Toxicity from the Structure of An Oxacalix[3]arene-HgCl 2 Complex?

t -Butyloxacalix[3]arene tris (diethylacetamide), known to mimic the cellular sodium ion selectivity filter, has been shown to bind HgCl 2 . The dimeric complex crystallises in the triclinic space group P 1 with a =17.3019(6) Å, b =18.7821(4) Å, c =19.9025(5) Å, ! =67.3010(10), # =77.664(2); % =77.238(2) and D c =1.370 g cm m 3 for Z =4. Refinement based on 37,818 observed reflections gave a final R value of 0.0483. Implications for routes of mercury uptake are discussed.     

Vertical Distribution of Particulate Mercury as Measured on a Meteorological Observation Tower (213m)

Abstract

The concentration of mercury in airborne particles was determined in samples collected at heights of 1m and at 175m up the Meteorological Observation Tower (213m) at the Meteorological Research Institute, Tsukuba between August 1985 and April 1986. The concentrations of particulate mercury at the two heights were compared with gaseous mercury levels at a height of 10m and with other chemical components in the particles. The concentrations of particulate mercury at both heights showed no positive correlation with those of gaseous mercury, total suspended particles, sulfate, chloride, sodium or calcium. However, there was some positive correlation between particulate mercury and nitrate concentrations especially at 175m; the concentrations of these components were found to be high when the wind direction was southwesterly. These results suggest that these components were transported from the Tokyo Metropolitan area.     

Simultaneous Determination of Copper (II) and Mercury (II) by Using a Zero-Crossing Method

Abstract

The application of a zero-crossing method to the simultaneous determination of copper (II) and mercury (II) with methylethylenediaminetetraacetic acid (MEDTA) is described. The procedure does not require equations to be solved, and it is suitable for concentrations of 0.008–0.036 mg ml^?1 of copper and 0.025–0.300 mg ml^?1 of mercury. The main interferences, both anionic and cationic, were easily eliminated. The method was applied to different aqueous matrices. It was compared with an atomic absorption spectrophotometry method (AA) and good results were obtained.     

Investigation of mercury metallothionein complexes in tissues of rat after oral intake of HgCl2

Mercury, a highly toxic metal found widely throughout the environment, is a potent inducer of metallothionein (MT) expression. The role of MTs in the detoxification of mercury after its oral intake in mammals is studied. After feeding rats with mercuric chloride by gastric gavage, the distribution of heavy metals in rat tissues was investigated by inductively coupled plasma mass spectrometry (ICP‐MS). Extensive accumulation of mercury, copper and zinc in kidney and liver is observed. A homemade preparative size‐exclusion chromatography (SEC) column (30 cm × 1.9 cm) packed with Sephadex G‐75 (40–120 µm particle size) gel (Pharmacia) was used for the purification of MT fractions in rat tissues. Preliminary results from SEC indicate that the mercury‐binding MT levels in liver were much lower than in kidney. The MT fractions were collected, desalted, and then separated by reversed‐phase high‐performance liquid chromatography (HPLC) with UV–Vis spectrometry, ICP‐MS and electrospray ionization MS detection. One major and several minor peaks were observed in the HPLC chromatograms of the MT fraction for the kidney sample. UV absorption spectra indicate that MTs were found to bind with mercury. There were no significant mercury‐binding MTs detected in the liver sample using UV detection. ICP‐MS detection showed that mercury‐binding MTs in kidney contained large amounts of mercury and copper but little zinc. Further characterization with ESI‐MS showed that the major peak found in kidney contained Hg₆Cu, Hg₅Cu₂‐MT‐2c and Hg₆‐MT‐2β, Hg₆Cu‐MT‐1γ, Hg₇‐MT‐2α. However, distinction between copper and zinc could not be made based on current mass spectrometric analysis because of instrumental resolution limitations. Copyright © 2005 John Wiley & Sons, Ltd.     

TRANSITION METAL COMPLEXES OF OLIGOTHIOETHER QUINOLYLOXY TERMINATED PODANDS: PART 2. CRYSTAL AND MOLECULAR STRUCTURE OF (1,8-BIS(QUINOLYLOXY)-3,6-DITHIAOCTANE)-COPPER(II) DIPERCHLORATE TRIHYDRATE

Abstract

The synthesis of the new ligand 1,8-bis(quinolyloxy)-3,6-dithiaoctane (1) and the corresponding Cu(II), Cu(I) and Co(II) complexes is reported. The crystal and molecular structure of the copper(II) complex, [Cu(1)](ClO₄)₂.3H₂O, has been determined by X-ray diffraction methods. The complex crystallizes in the orthorhombic space group Fddd, with cell data Z = 16, a = 20.326(2), b = 20.879(3) and c = 28.308(4)Å. The structure consists of discrete [Cu(1)]^?2+ cations separated by (structurally disordered) perchlorate anions and three lattice water molecules per cation. The coordination geometry about the copper atom is pseudo-octahedral with the quinoline nitrogen and thioether sulfur atoms at the equatorial positions and the ether oxygen atoms at the axial positions. ¹H NMR line-broadening experiments indicate that electron-transfer self-exchange reactions between the copper(I) and copper(II) complexes of (1) is immeasurably slow on the NMR time-scale. The coordination chemistry of (1) is compared with its oxygen analogue, 1,8-bis(quinolyloxy)-3,6-dioxaoctane.     

Determining Trace Concentrations of Copper in Water by Cathodic Film Stripping Voltammetry with Adsorptive Collection

Abstract

A technique is presented for the determination of trace concentrations of copper (II) in natural water samples by cathodic stripping voltammetry of a film of copper-catechol complex ions adsorbed on the hanging mercury drop electrode. The peak height of the copper-catechol reduction peak is linearly dependent upon the copper (II) concentration between 10^?10 and 10^?7 M. The detection limit of the technique is below 10^?10 M copper (II) for a collection time of 3 minutes, but the sensitivity can be further increased four-fold by collecting for 15 minutes. The sensitivity is reduced by high concentrations of competing trace metals and of surfactants, which necessitate the use of standard additions to the sample.     

Determination of copper in sea water by cathodic stripping voltammetry of complexes with catechol

A reduction current is obtained when an aqueous solution of copper and catechol is subjected to differential-pulse cathodic stripping voltammetry (d.p.c.s.v.) because of the reduction of copper(II)—catechol complex ions which adsorb onto the hanging mercury drop electrode (HMDE). The most likely form of the adsorbed complex ions is CuL^2?₂ (L being catechol). A.c. polarographic measurements showed that these complex ions adsorb more strongly onto the drop than free catechol ions. Monolayer adsorption density is obtained at 2.1 × 10^?10 molecules/cm², equivalent to a surface area of 78 A² complex ion, which agrees well with the molecular surface area calculated from the bond lengths. Analytically useful currents are obtained at very low metal concentrations, such as in uncontaminated sea water. The possible interference by other trace metals, major cations, and organic complexing ligands is investigated. Competition for copper ions by natural organic complexing ligands is evident at low concentrations of catechol. Analysis of the dissolved copper concentration in sea water by d.p.c.s.v. at the HMDE (at neutral pH) compares favourably with the d.p.a.s.v. technique at a rotating disk electrode (at low pH) because of the shorter collection period and greater sensitivity.     

Peak Polarogmphy and Electroreduction Mechanism of a Ferriheme Dimer

Abstract

The electroreduction of aqueous ferriheme was investigated at Kemula's hanging mercury drop electrode. Peak voltammograms were obtained at 9 < pH < 11 using linear potential sweep rates in a range between 0.01 and 10 volt per second. Reduction of ferriheme to ferroheme proceeded via a novel “mixed ferrous-ferric” intermediate whose disproportionation regenerated the initial ferriheme dimer yielding simultaneously equimolar amounts of the ultimate ferroheme dimer product.     

Synthesis of Azo-Sulfa Drugs Based on 2-Pyridinone and 2-Pyridinethione

Some new azo sulfa drugs 3-cyano-4,6-diphenyl-1-[4-(N-substituted)sulfamyl]phenylazo-2-pyridinone dyes (1-6) and 3-cyano-4,6-diphenyl-1-[4-(N-substituted)sulfamyl]phenylazo-2-pyridinethione dyes (1′-6′) were synthesized by coupling of 4-(N-substituted)sulfamylbenzene diazonium salts with 3-cyano-4,6-diphenyl-2-pyridinone and/or with 3-cyano-4,6-diphenyl-2-pyridin-ethione. The corresponding iron (1a-6a, 1′a-6′a), copper (1b-6b, 1′b-6′b) and mercury (1c-6c, 1′c-6′c) chelates wvere also prepared. All synthesized compounds were screened in vitro for antibacterial and antifungal activities.     

Stripping Potentiometry of Lead,Cadmium and Copper at a Nafion Coated Glassy Carbon Electrode with Encapsulated Mercury Acetate

Abstract

The stripping potentiometric determination of lead, cadmium and copper with mercury film glassy-carbon electrodes coated with a Nafion membrane was investigated. The mercury film was plated using either mercury(II) acetate encapsulated within the Nafion membrane or a mercury(II) solution. Dissolved dioxygen was used as the stripping agent. The electrodes showed promising properties, particularly robustness and response repeatability. A linear dependence of the stripping time on concentration was found in the μg l^?1 concentration range (s.d. of intercept ≤ 0.3 μg l^?1, r.s.d. of slope ≤ 1%, for both lead and cadmium).     

Voltammetric Behavior of Osmium‐Labeled DNA at Mercury Meniscus‐Modified Solid Amalgam Electrodes. Detecting DNA Hybridization

The complex of osmium tetroxide with 2,2′‐bipyridine has been utilized as a probe of DNA structure and an electroactive marker of DNA in DNA hybridization sensors. It produces several voltammetric signals, the most negative of them has been observed only at mercury electrodes. This signal is of catalytic nature affording a high sensitivity of DNA determination. The catalytic current due to evolution of hydrogen in voltammetry of DNA modified by complex of osmium tetroxide with 2,2′‐bipyridine (DNA‐Os,bipy) was studied. Solid amalgam electrodes (modified with mercury menisci) of silver (m‐AgSAE), copper (m‐CuSAE), gold, and of combined bismuth and silver, were used as possible substitutes for mercury electrodes. Besides the hanging mercury drop electrode (HMDE), the catalytic current was observed only on m‐AgSAE and m‐CuSAE. Electrodes of gold and bismuth amalgams did not give the catalytic current. The detection limit of DNA‐Os,bipy on HMDE was 0.1 ng mL^?1 (RSD=2.3 %, N=11), and on m‐AgSAE 0.2 ng mL^?1 (RSD=3.1%, N=11). The m‐AgSAE was successfully applied as a detection electrode in double‐surface DNA hybridization experiments offering highly specific discrimination between complementary (target) and nonspecific DNAs, as well as determination of the length of a repetitive DNA sequence. The m‐AgSAE has proved a convenient alternative to the HMDE or carbon electrodes used for similar purposes in previous work.     

Analytical Determination of N-(2-Mercapto Propionyl)Glycine (Tiopronin) by Voltammetric Methods

Abstract

The anodic processes which occur at the mercury electrode in N-(2-mercaptopropinyl)glycine (tiopronin) solutions are studied by polarographic techniques (d.c., d.p. and a.c₁.), controlled potential coulometry and cathodic stripping voltammetry. According to the observed electrochemical behaviour the overall electrode process is the formation of a mercury(II)-mercaptide. Adsorption on the electrode of both the mercaptide and the free thiol is present. The d.p.p. peak at -0.58 V or the voltammetric stripping peak at -0.56 V are used for the analytical determination of N-(2-mercaptopropionyl)glycine within the concentration ranges 7.0 10^?5 - 6.8 10^?6 mol 1^?1 or 3.0 10^?7 - 1.0 10^?9 mol I^?1, respectively. Calibration functions are reported in both cases. The interference of several organic compounds is described.     

Spectrophotometric determination of copper with tiron

The reagent Tiron forms a soluble greenish-yellow complex with cupper. The sensitivity of the colour reaction is 0.24 mμ of copper/cm₂. The colour system at a pH of 6.1 to 6.9 is stable for over 24 h and shows a maximum absorption at 375 mμ. It obeys Beer's law at the latter wave length within a copper concentration of 10 to 160 p.p.m. The optimum range, however, is from 50 to 160 p.p.m. of copper, where the percent relative analysis error per 1% absolute photometric error is 2.94. JOB's method of continuous variation and the molar ratio method of YOE et al.² indicate that in solution the complex contains the metal and the reagent in a ratio of l : 2, with a dissociation constant on the order of 5.3 ? 10^-6.     

Azothia- and Azoxythiacrown Ethers as Ion Carriers. Part II. Anionic Response of Membrane Electrodes

Ion-selective electrodes with plasticized poly(vinyl chloride) membranes containing 13-membered azothia- and azoxythiacrown ether complexes with silver, mercury or copper ions have been investigated. The potentiometric response towards various anions was studied. For membranes based on azothiacrown ether (B) complexes the following selectivity patterns were found:I^- > SCN^-, Br^- > Cl^- ClO₄ ^- > salicylate, NO₃ ^- (complex B with silver), I^- > ClO₄ ^- > SCN^-, Br^- > salicylate > Cl^-, NO₃ ^- (complex B with mercury) and SCN^- > I^- > Br^- > ClO₄ ^- > Cl^- > salicylate > NO₃ ^- (complex B with copper). For azoxythiacrown ether (A) only membranes containing its complex with mercury exhibited pronounced anion response and the selectivity pattern was similar to that observed for complex B with mercury. The origin of the anion response has been discussed.     

Determination of metals at trace levels via pre-column derivatization and nonpolar stationary-phase high-performance liquid chromatography with n-butyl-2-naphthylmethyldithiocarbamate complexes

A new, very stable dithiocarbamate, bis(n-butyl-2-naphthylmethyldithiocarbamate) zinc(II), has been synthesized and its use in trace metal determination by high-performance liquid chromatography (h.p.l.c.) has been investigated. Metal complexes of this ligand are thermodynamically stable and kinetically inert at the 1 × 10^-8 M level. Various metal complexes including nickel(II), iron(III), copper(II), mercury(II), and cobalt(II) have been “baseline” separated by nonpolar stationary-phase h.p.l.c. The detection limits are about 1–2 ng with a variable-wavelength absorbance detector.     

Amplified Fluorescence Turn‐On Assay for Mercury(II) Detection and Quantification based on Conjugated Polymer and Silica Nanoparticles

An amplified fluorescence turn‐on assay for mercury(II) detection and quantification was developed. This method makes use of specific thymine/mercury(II)/thymine coordination to capture Fl‐labeled DNA onto NP surface. Addition of a cationic conjugated polymer leads to an amplified Fl signal in solution. A sigmoidal Hg²⁺ working curve is obtained at fixed [NP] with a detection limit of 0.1 × 10⁻⁶ M . However, by reducing [Hg²⁺] and [NP] simultaneously, while maintaining [Hg²⁺]:[DNA duplex] = 3:1, a linear calibration curve is observed with a detection limit of 5 × 10⁻⁹ M . The CCP‐assisted mercury(II) assay shows potential applications in environmental mercury detection and for industrial process control.