Semi-micro ion chromatography of iodide in seawater

Large sample volume injections including both on-column analyte focusing and on-column matrix elimination techniques were examined for semi-micro ion chromatography of trace iodide (I⁻) in seawater. A semi-microcolumn (35×1 mm I.D.) packed with styrene–divinylbenzene copolymer with high anion-exchange capacity and a mobile phase of 0.03 M NaClO₄+0.5 M NaCl+5 mM sodium phosphate buffer, pH 6.0, was used. Iodide in seawater was effectively concentrated on the column by both electrostatic and hydrophobic interactions and was eluted without peak broadening. ClO₄⁻ (NaClO₄) in the mobile phase was effective for the elution of iodide and Cl⁻ (NaCl) for both the concentration of iodide (I⁻) with hydrophobicity and the removal of interference by the major anions. An excess of major anions in seawater did not disturb the detection of iodide at UV 226 nm. The relative standard deviations for successive injections of 5 and 1 μg/l I⁻ (2 ml of 35‰ artificial seawater) were 1.5 and 5.8% (n=5, each), respectively. The slope of calibration curve (by peak area) using the semi-microcolumn was ∼2.8-times higher than that for a conventional column with the same resin (150×4.6 mm I.D.) The present method had a detection limit of 0.2 μg/l I⁻ for 2 ml of 35‰ artificial seawater and was successfully applied to seawater samples.     

A Ferritin Reactor for Entrapping Various Heavy Metal Ions in Flowing Seawater

Recent studies showed that the ferritins had three tunnels across the protein shell with 0.7~0.9 nm diameter for iron metabolism^[1-2]. However, very little was known the mechanism(s) that the ferritin reactor entrapped various heavy metal ions (M²⁺) and other small organic molecules in the flowing seawater directly.     

Glycosidases of turnip leaf tissues

Four myrosinase (β-thioglucosidase EC. 3.2.3.1) and seven disaccharase (β-fructofuranosidase, EC. 3.2.1.26) isoenzymes were isolated from turnip leaves. The most active enzymes were isolated in pure form. Myrosinase and disaccharase mol wt was 62.0 × 10³ and 69.5 × 10³ dalton, respectively, on the basis of gel filtration on Sephadex G-200. Myrosinase pH profile showed high activity between pH 5 and 7 with the optimum at pH 5.5. The purified enzyme was heat-stable for 60 min at 30°C with only loss of 24% of activity. Its activity is strongly inhibited (100%) by Pb²⁺, Ba²⁺, Cu²⁺ and Ca²⁺ ions, and activated (70%) by EDTA at 0.04M. The pure enzyme failed to hydrolyze amylose, glycogen, lactose, maltose, and sucrose. TheK _m andV _max values of myrosinase using sinigrin as specific substrate was 0.045 mM and 2.5 U, respectively. The maximal activity of disaccharase enzyme was obtained at pH 4–5 and 35–37°C. The enzyme was heat-stable at 30°C for 30 min with only 10% loss of its activity. Its activity is strongly activated (70–240%) by Ca²⁺, Ba²⁺, Cu²⁺, and EDTA at 0.01M. The enzyme activity is specific to the disaccharide sucrose and failed to hydrolyze other disaccharides (maltose and lactose). TheK _m andV _max of disaccharase were 0.123 mM and 3.33 U, respectively.     

Effect of copper and manganese ions on activities of laccase and peroxidases in three Pleurotus species grown on agricultural wastes

Copper (Cu²⁺) and manganese (Mn²⁺) ions influenced laccase (Lac) and peroxidase production in Pleurotus eryngii, Pleurotus ostreatus, and Pleurotus pulmonarius. In P. eryngii, the optimum Cu²⁺ concentration for Lac production was 1 mM and for peroxidases 10mM, and Mn²⁺ concentration of 5mM led to peaks of Lac and peroxidase activity. In P. ostreatus HAI 493, the highest level of Lac activity was at Cu²⁺ concentrations of 1 and 10 mM and Mn²⁺ concentration of 1mM, respectively. The absence of Cu²⁺ and Mn²⁺ caused the highest levels of peroxidase production. In P. ostreatus HAI 494, the highest level of Lac activity was at a Cu²⁺ concentration of 5 mM and at Mn²⁺ concentration of 1 mM, respectively. High levels of peroxidase activity were found in the medium without and with 1mM Cu²⁺, and at 1 and 5 mM Mn²⁺, respectively. In P. pulmonarius, the highest Lac activity was found in the presence of 5 mM Cu²⁺ and 5 mM Mn²⁺, respectively. The absence of Cu²⁺ and Mn²⁺ as well as their presence at a concentration of 1 mM led to the peaks of peroxidase activities.     

Influence of ligand type and solution pH on heavy metal ion complexation in cellulosic fibre: model calculations and experimental results

Complexation of heavy metal ions such as Cu²⁺, Zn²⁺ and Co²⁺ by cellulosic fibres cotton, lyocell and viscose was studied in the pH range from pH 7–13. Glycine and sodium D-gluconate complexes were studied. Complex formation in the cellulose matrix depends on ligand, solution pH, complex species formed and type of cellulosic fibre. Species distribution in solution was calculated using the program SPE and literature data for formation constants of M²⁺-glycine and M²⁺-gluconate complexes. The calculated data permit explanation of the experimental heavy metal uptake in the cellulose matrix. In presence of GLY lower heavy metal concentrations were observed. Heavy metal complexation decreases with increasing pH between 7 and 11. For Cu²⁺ and Zn²⁺ a strong increase in metal binding capacity in the fibres was observed at pH 13 for Cu²⁺ and pH 11–12 for Zn²⁺ respectively. Low Zn²⁺ content is analysed at pH 13 due to zincate formation. Member of EPNOE, European Network of Excellence “Polysaccharides” .     

Self-assembly of pyrene boronic acid-based chemodosimeters for highly efficient mercury(II) ion detection

A new chemodosimeter consisting of pyrene and boronic acid (1) for the detection of Hg²⁺ ions is described. The amphiphilic nature of 1 leads to self-assembly in aqueous solution and the high electron density throughout the aggregated pyrene units provides an outstanding platform for energy and electron transport. Self-assembled 1 exhibits a selective and sensitive fluorescence response to Hg²⁺ ions, where the Hg²⁺ ion allows a fast transmetallation of 1, which drastically reduces its fluorescence. The Stern-Volmer (SV) quenching constant for the fluorescence quenching of self-assembled 1 by Hg²⁺ ions is approximately 1.8 × 10⁶ M^?1, and Hg²⁺ ions can be sensed with a detection limit of 6.6 × 10^?9 M. In addition, self-assembled 1 exhibits excellent sensing performance at nano-molar concentration levels for Hg²⁺ ion contamination of tap water, fresh water, and seawater.     

Flow-injection determination of sulphite and assay of sulphite oxidase

Sulphite (1–80 × 10^?5 M) in formaldehyde-stabilized solutions is determined by injection into a flowing stream of pH 8.5 phosphate buffer, passing through a mini-column of sulphite oxidase immobilized on controlled-pore glass, with amperometric detection of the hydrogen peroxide produced. Sulphite oxidase (5–100 U l^?) is determined by injection into a flowing stream of formaldehyde-stabilized 2 × 10^?3 M sodium sulphite in pH 8.0 phosphate buffer; hydrogen peroxide is again monitored.     

An indicator displacement system for fluorescent detection of phosphate oxyanions under physiological conditions

A fluorogenic chemosensing system is described and shown to selectively detect pyrophosphate under physiological conditions. In the best case, pyrophosphate and hydrogen phosphate are capable of displacing a fluorescent coumarin-derived indicator from a bis Zn²⁺-dipicolylamine coordination compound with association constants of 10⁷ and 10⁵ M⁻¹, respectively.     

Sorption of uranyl ions on silica: Effects of contact time, pH, ionic strength, concentration and phosphate

The sorption of UO₂ ²⁺ and phosphate on silica were simultaneously studied. The effect of contact time between the solid phase and aqueous solution, pH and ionic strength on the UO₂ ²⁺ sorption in the absence and the presence of phosphate was investigated. The effect of contact time between the solid phase and aqueous solution, pH and ionic strength on the phosphate sorption was investigated too. The isotherms of UO₂ ²⁺ and phosphate sorption at different pH values were determined. It was found that as compared with the sorption in the absence of phosphate, the sorption of UO₂ ²⁺ on silica in the presence of phosphate is increased at low pH and decreased at high pH; the abruptly increased with increasing pH in the pH range 3-6; the sorption is gradually decreased with increasing pH in the pH range 2-12; the sorption insensitive and the sorption of phosphate is sensitive to ionic strength.     

Determination of tetramethylthiuram disulfide (thiram) for residual analysis in food using spectrophotometry coupled with a solid-phase reactor (SPR) in a flow system

An analytical method was developed for quantification of the fungicide thiram (tetramethylthiuram disulfide), based on its capacity to complex Cu²⁺ ions. A solid-phase reactor (SPR) was coupled in a flow system containing a spectrophotometer as detector. The SPR consisted of a tube filled with finely ground resin, in which copper(II) phosphate was immobilised prior to polymerisation. Contact of thiram with the Cu²⁺ ions immobilised in the resin resulted in the formation of a strongly coloured Cu²⁺/thiram complex. Maximum absorbance of the Cu²⁺/thiram complex was obtained at a wavelength of 439 nm. The usefulness of the methodology has been evidenced by the determination of thiram residues in corn and bean grains. Previously, a variety of transition metal cations which would form coloured complexes with tetramethylthiuram disulfide were tested.     

Differential pulse polarographic behaviors of p-nitrosodimethylaniline: Application for microdetermination of NADH

The differential pulse polarographic behavior of p-nitrosodimethylaniline has been investigated in Britton-Robinson buffer and phosphate buffer. The peak obtained at pH 8.0 is recommended for the trace determination of this compound, with an experimental detection limit of 18 ppb (1.2 × 10^?7M) in simple aqueous solution. The method is also applied for the indirect microdetermination of NADH. The experimental detection limit of NADH is shown to be 1.05 × 10^?6M.     

Biosorption of metal ions with Penicillium chrysogenum

Biosorption of metal ions with Penicillium chrysogenum mycelium is described in this article. Alkaline pretreatment was used to remove proteins and nucleic acids from cells, and this treatment increased the adsorption capacities, for Cr³⁺ from 18.6 mg g⁻¹ to 27.2 mg g⁻¹, for Ni²⁺ from 13.2 mg g⁻¹ to 19.2 mg g⁻¹, for Zn²⁺ from 6.8 mg g⁻¹ to 24.5 mg g⁻¹. The adsorption of metal ions was strongly pH dependent. The mycelium could beused for large-scale removal of Cr³⁺ from tannery wastewater. The results show that this inexpensive mycelium adsorbent has potential in industry because of its high adsorption capacity. The main chelating sites are amino groups (−NH₂) of chitosan in the mycelium. A new model is established, which describes the relation of adsorption of metal ions on pH according to amino group chelating with metal ions and H⁺. The relative errors of simulation for Cu²⁺, Ni²⁺, Zn²⁺, and Cr³⁺ are 4.66%, 5.45%, 11.55%, and 1.69%, respectively.     

Author index for volume 31

The solid state reactions of MMoO₄ (M = Mg²⁺, Fe²⁺, and Ni²⁺) and orthorhombic TeO₂ were investigated. A new metal telluromolybdate MgTeMoO₆ was obtained in the case of Mg; its structure belongs to the orthorhombic system with unit-cell dimensions a = 5.262Å, b = 5.028 Å, c = 8.880 Å. Fe₂(MoO₄)₃ and a new compound were formed in the case of Fe. The new compound is made up with Fe³⁺ ions and its chemical formula cannot be recognized as FeTeMoO₆. In the case of Ni a complex reaction mixture is obtained. An explanation is given of the ability of M²⁺ ions to form the metal telluromolybdates. The catalytic properties of MgTeMoO₆ are discussed and compared to those of the other metal telluromolybdates.     

Positive/negative liquid secondary ion mass spectrometry ofLn-EDTA (1:1) complexes. Formation of molecular ion adducts with neutral species of the matrix orLn-EDTA

Summary The mass spectra of 1:1 complexes ofEDTA with lanthanide cations (Ln=Sm, Eu, Gd, Tb or Dy) upon positive/negative LSIMS are presented. In glycerol used as a matrix, adduct-ions such as [M+H]⁺, [M+H+nGly]⁺, [2M+H]⁺, [2M+H+Gly]⁺ (positive LSIMS) or [M-H]^–, [M-H+nGly]^–, [2M-H]^–, [2M-H+Gly]^– (negative LSIMS), wheren=1–3, are formed. Reactions leading to the formation of adduct-ions are suggested.

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Positive/negative Liquid-Sekundärionen-Massenspektrometrie vonLn-EDTA-(1:1)-Komplexen. Bildung von molekularen Ionenaddukten mit neutralen Spezies aus der Matrix oderLn-EDTA

Zusammenfassung Die Massenspektren von 1:1-Komplexen vonEDTA mit Lanthanidenkationen (Ln=Sm, Eu, Gd, Tb oder Dy) mittels positiver/negativer LSIMS werden präsentiert. In Glycerin als Matrix bilden sich Adduktionen wie [M+H]⁺, [M+H+nGly]⁺, [2M+H]⁺, [2M+H+Gly]⁺ (positive LSIMS) oder [M-H]^–, [M-H+nGly]^–, [2M-H]^–, [2M-H+Gly]^– (negative LSIMS), wobein=1–3. Es werden Reaktionen vorgeschlagen, die zur Bildung von Adduktionen führen.

     

Sorption of Cs<Superscript>+</Superscript> and Sr<Superscript>2+</Superscript> by ion exchanger based on titanium phosphate

Sorption capacity of a composite ion exchanger based on titanium phosphate for Cs⁺ and Sr²⁺ cations was studied. The effect of pH and concentration of salts and, in particular, sodium chloride in solution on the sorption efficiency and distribution coefficient was analyzed. The diffusion coefficients were calculated for the Cs⁺ and Sr²⁺ cations and the time of half-exchange of the Na⁺ cation for the Cs⁺ and Sr²⁺ cations was found.     

Pressure versus Temperature Effects on Intramolecular Electron Transfer in Mixed‐Valence Complexes

Mixed‐valence trinuclear carboxylates, [M₃O(O₂CR)₆L₃] (M=metal, L=terminal ligand), have small differences in potential energy between the configurations M^IIM^IIIM^III?? M^IIIM^IIM^III??M^IIIM^IIIM^II, which means that small external changes can have large structural effects, owing to the differences in coordination geometry between M²⁺ and M³⁺ sites (e.g., about 0.2 Å for Fe? O bond lengths). It is well‐established that the electron transfer (ET) between the metal sites in these mixed‐valence molecules is strongly dependent on temperature and on the specific crystal environment; however, herein, for the first time, we examine the effect of pressure on the electron transfer. Based on single‐crystal X‐ray diffraction data that were measured at 15, 90, 100, 110, 130, 160, and 298 K on three different crystals, we first unexpectedly found that our batch of Fe₃O (O₂CC(CH₃)₃)₆(C₅H₅N)₃ ( 1 ) exhibited a different temperature dependence of the ET process than previous studies of compound 1 have shown. We observed a phase transition at around 130 K that was related to complete valence trapping and Hirshfeld surface analysis revealed that this phase transition was governed by a subtle competition between C? H???π and π???π intermolecular interactions. Subsequent high‐pressure single‐crystal X‐ray diffraction at pressures of 0.15, 0.35, 0.45, 0.74, and 0.96 GPa revealed that it was not possible to trigger the phase transition (i.e., valence trapping) by a reduction of the unit‐cell volume, owing to this external pressure. We conclude that modulation of the ET process requires anisotropic changes in the intermolecular interactions, which occur when various directional chemical bonds are affected differently by changes in temperature, but not by the application of pressure.     

Advanced oxidation processes for decolorization of aqueous solution containing acid red G azo dye

Some investigations concerning the decolorization of Acid Red G azo dye by photooxidation with hydrogen peroxide were performed. The influences of pH, oxidant concentration, and the presence of Fe²⁺ or other metal ions (Co²⁺, Cu²⁺, Ni²⁺, Mn²⁺) as potential catalysts, were investigated. The best results were obtained in the presence of ferrous ions in acid and neutral media. The other ions are not as effective as Fe²⁺ for dye decolorization. Co²⁺ and Cu²⁺ ions have a catalytic action, at low concentration, within a wide range of pH. Ni²⁺ and Mn²⁺ ions have no catalytic effect in photooxidation with hydrogen peroxide at acid Ni²⁺ and Mn²⁺ ions have no catalytic effect in photooxidation with hydrogen peroxide at acid pH values, but show a weak action in alkaline media.     

Cd2Cu(PO4)2

During an investigation of the insufficiently known system M1O–M2O–X₂O₅–H₂O (M1 = Cd²⁺, Sr²⁺ and Ba²⁺; M2 = Cu²⁺, Ni²⁺, Co²⁺, Zn²⁺ and Mg²⁺; X = P⁵⁺, As⁵⁺ and V⁵⁺), single crystals of the novel compound dicadmium copper(II) bis[phosphate(V)], Cd₂Cu(PO₄)₂, were obtained. This compound belongs to a small group of compounds adopting a Cu₃(PO₄)₂‐type structure and having the general formula M1₂M2(XO₄)₂ (M1/M2 = Cd²⁺, Cu²⁺, Mg²⁺ and Zn²⁺; X = As⁵⁺, P⁵⁺ and V⁵⁺). The crystal structure is characterized by the interconnection of infinite [Cu(PO₄)₂]_n chains and [Cd₂O₁₀]_n double chains, both extending along the a axis. Exceptional characteristics of this structure are its novel chemical composition and the occurrence of double chains of CdO₆ polyhedra that were not found in related structures. In contrast to the isomorphous compounds, where the M1 cations are coordinated by five O atoms, the Cd atom is coordinated by six. The dissimilarity in the geometry of M1 coordination between Cd₂Cu(PO₄)₂ and the isomorphous compounds is mostly due to the larger ionic radius of the Cd cation in comparison with the Cu, Mg and Zn cations. Sharing a common edge, two CdO₆ polyhedra form Cd₂O₁₀ dimers. Each such dimer is bonded to another dimer sharing common vertices, forming [Cd₂O₁₀]_n double chains in the [100] direction. The Cu atoms, located on an inversion centre (site symmetry ), form isolated CuO₄ squares interconnected by PO₄ tetrahedra, forming [Cu(PO₄)₂]_n chains similar to those found in related structures. Conversely, the [Cd₂O₁₀]_n double chains, which were not found in related structures, are an exclusive feature of this structure.     

Chromatographic Characterization of Molecularly Imprinted Microspheres Synthesized by Aqueous Microsuspension Polymerization：Influences of pH,Kinds and Concentration of Buffer on Capacity Factors

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The kinetics of the reaction between magnesium and EBT

The kinetics of the reaction between Mg²⁺ and Eriochrome-Black-T (EBT) has been investigated in the pH range between 7.05 and 9.0, in the presence of 12% ethanol. The reaction is found to consist of two parallel paths, one involving the tervalent unprotonated ligand, and one its monoprotonated form. The rate constant for the unprotonated ligand has a “normal” value, whereas that for the protonated form is much lower. The numerical value of the rate constant for the unprotonated ligand obtained from results at a magnesium concentration of 10^?3M and a pH up to 9.0 is, however, inconsistent with that obtained from results at [Mg²⁺] = (1 to 4) × 10^?3M and pH up to 8.1. This can be explained, at least partially, if we assume the intermediate MgHD to lose its proton not only to H₂O, but also to other bases present in the solution.