Study of the thermal decomposition of cellulose-hyphan and its complexes with some transition and indium metal ions

The studied complexes formed by the chelating ion exchanger were characterized by reflectance and infrared spectrometry. The thermal degradation of pure cellulose-hyphan (CH) and its complexes with Hg²⁺, In³⁺, Cr³⁺, Mo⁴⁺ and Mn²⁺ under an atmosphere of air has been studied using thermal gravimetry (TG) and differential thermal analysis (DTG). The results showed that four different stages are accompanying the decomposition of (CH) and its complexes with the studied metals. These stages were found to be affected by the presence of the investigated metal ions. On the bases of the applicability of a non-isothermal kinetic equation it was found to be a first-order reaction with the rate of degradation,k, ranging from 8.3·10^?5 to 6.2·10^?3 for (CH) and from 1.7·10^?5 to 6.6·10^?3 s^?1 for its complexes. The activation energy,E _a, the entropy change, ΔS°, the enthalpy change, ΔH° and Gibbs free energy, ΔG° are calculated by applying the rate theory of the first-order reaction. The effect of the different central metal ions on the calculated thermodynamic parameters is discussed.     

Kinetic determination of ascorbic acid by the 2,6-dichlorophenolindophenol reaction with a stopped-flow technique.

The reaction of ascorbic acid with 2.6-dichlorophenolindophenol is applied for the kinetic determination of ascorbic acid in 0.05M oxalic acid. Stopped-flow techniques are used; the concentrations of the reactants of the second-order reaction can be adjusted so that the transmittance signal remains nearly invariant for a wide range of voltage. Theoretical and experimental results are in very good agreement. Analytical working curves are presented for the determination of ascorbic acid in the ranges 5.0·10^-4–1.0·10^-2M and 5.0·10^-5–1.0-·10^-3M with errors of 1.0% and 2.2%. respectively. The method is simple, fast and sensitive.     

Application of INAA for investigation of magnesium and aluminium oxide materials

The paper presents investigations of changes in optical absorption and photo luminescence spectra of magnesium oxide, and natural and synthetic magnesium aluminium spinel related with the content of transition metal ions (Cr, Fe, Mn) and the irradiation with fast neutrons. Six synthetic single magnesium aluminium spinel crystals with different stoichiometry (MgO·nAl₂O₃), five natural crystals from Ural and Pamir deposits, and seven MgO crystals were studied. Micro impurities (Cr, Fe, and Mn) and macro component (Mg, Al) quantities have been determined using the instrumental neutron activation analysis technique. Concentrations of impurities in different spinels were found in following ranges: for Cr—1 × 10^?4 to 8 × 10^?2 %, for Mn—2 × 10^?5 to 23 %, for Fe—1 × 10^?4 to 1.2 %. Three ranges of luminescence: 380–460, 650–850 and 850–1,050 nm, were established in the most part of the investigated MgO samples. Analysis shows that the intensity of emission in each of these regions is strongly dependent on the concentration of transition metal ions. Great deviation from the stoichiometry of the irradiated MgO·2.8Al₂O₃ crystal leads to the local structure of α-Al₂O₃ formation around Cr³⁺ ions. The orange emission is attributed to Mn²⁺ in octahedral coordination, it can be assumed that the band at 570 nm is belonging to the complex centre “Mn²⁺–F⁺ (or F centre)”.     

Production of doubly charged clusters (H2O)n · Ba2+ and (H2O)n · Ca2+ under low temperature fast atom bombardment conditions

Production of doubly charged ions of alkaline earth metals Ba²⁺ and Ca²⁺ and their doubly charged clusters with water molecules (H₂O)_n · Ba²⁺, (H₂O)_n · Ca²⁺ (n = 1, 2, 3) by means of low temperature fast atom bombardment technique is observed in the case of crystalline hydrates of BaCl₂ and CaCl₂ salts, formed during freezing of water-salt solutions. Reasons for a possibility of production of the doubly charged species in the case of the two indicated salts and their absence in the case of chlorides of some other divalent metals (Mg, Mn, Co, Cu, Zn) are discussed. As to singly charged secondary ions Me⁺, MeCl⁺, MeOH⁺, [(H₂O)_n · MeCl]⁺, [(H₂O)_n · MeOH]⁺ (where Me is metal), high efficiency of their production from crystalline hydrates was observed and possible explanation of the phenomenon is suggested.     

Fe2+ and Cu2+ Increase the Production of Hyaluronic Acid by Lactobacilli via Affecting Different Stages of the Pentose Phosphate Pathway

This study aimed at optimizing the production of hyaluronic acid by Lactobacillus acidophilus FTDC 1231 using response surface methodology and evaluating the effects of divalent metal ions along the production pathway using molecular docking. Among different divalent metal ions that were screened, only iron (II) sulphate and copper (II) sulphate significantly (P?<?0.05) affected the production of hyaluronic acid. Subsequent optimization yielded hyaluronic acid at concentration of 0.6152?mg/mL in the presence of 1.24 mol L^?1 iron (II) sulphate and 0.16 mol L^?1 of copper (II) sulphate (103 % increase compared to absence of divalent metal ions). Data from molecular docking showed Fe²⁺ improved the binding affinity of UDP-pyrophophorylase towards glucose-1-phosphate, while Cu²⁺ contributed towards the interaction between UDP-glucose dehydrogenase and UDP-glucose. We have demonstrated that lactobacilli could produce hyaluronic acid at increased concentration upon facilitation by specific divalent metal ions, via specific targets of enzymes and substrates along pentose phosphate pathway.     

Thermodynamic studies on complexation of divalent transition metal ions with some zwitterionic buffers for biochemical and physiological research

The interaction between the zwitterionic buffers (3-[N-bis(2-hydroxyethyl)amino]-2-hydroxy propane sulfonic acid, N-(2-actamido)-2-aminoethane sulfonic acid, and 3-[(1,1-dimethyl-2-hydroxyethyl)amino]-2-hydroxy propane sulfonic acid) with some divalent transition metal ions (Cu^II, Ni^II, Co^II, Zn^II, and Mn^II) were studied at different temperatures (298.15 to 328.15) K at ionic strength I = 0.1 mol · dm⁻³ NaNO₃ and in the presence of 10%, 30%, and 50% (w/w) dioxene by using potentiometry. The thermodynamic stability constants were calculated as well as the free energy change for the 1:1 binary complexation. The protonation constants of the zwitterionic buffers were also determined potentiometrically under the above conditions.     

Removal of zinc and mercury ions from aqueous solution by hydrous ceric oxide

The present work deals with study of uptake behavior of zinc and mercury ions by hydrous ceric oxide applying a radiotracer technique. The influence of various parameters such as concentration, temperature and pH have been examined. It was observed that the amount of zinc and mercury ions adsorbed at equilibrium increases with increase of adsorptive concentration (1.0·10⁻⁷ to 1.0·10⁻²M), temperature (303–333K) and pH (ca. 3–10). Concentration dependence data agree well with the classical Freundlich isotherm. The radiation stability of hydrous ceric oxide was also investigated by exposing it to a 11.1 GBq (Ra−Be) source associated with γ-dose of 1.72 Gy·h⁻¹ and also using a⁶⁰Co source (4.66 kGy·h⁻¹). Adsorption of these metal ions in the presence of some monovalent and divalent cations and complexing agents has also been included in the study.     

Collisional de-excitation of the metastableD-states of Ba+ by He,Ne, N2 and H2

The rate constants 〈σ · υ〉 for collisional de-excitation of the metastable 5D states of Ba⁺ ions have been determined in an ion trap experiment. TheD-states are selectively populated by pulsed laser excitation of the 6P _1/2 or 6P _3/2 state and the decay at different background pressures is monitored by the change in fluorescence intensity of the excited ions. From the pressure dependence of the decay constants we calculate the de-excitation rate constants for different collision partners, averaged over the velocity distribution of the trapped ion cloud. For He, Ne, H₂ and N₂ we obtain in the c.m. energy range of 0.1–0.5 eV: 〈σ·υ〉 (He)=3.0±0.2·10^?13cm³/s, 〈σ·υ〉 (Ne)=5.1±0.4·10^?13cm³/s, 〈σ·υ〉 (H₂)=3.7±0.3·10^?11cm³/s, 〈σ·υ〉 (N₂)=4.4±0.3·10^?11cm³/s. The results can be understood qualitatively by a consideration of the ion-atom and ion-molecules interaction potential.     

A high-spin cyanide-bridged Mo6Mn9 cluster: crystal structure and magnetism

A cyanide-bridged bimetallic octacyanomolybdate(V)-based polynuclear cluster, {Mn ₉ ^II [Mo^V(CN)₈]₆(EtOH)₂₄} · 6EtOH · 3i-C₃H₇OH · 3H₂O (1), has been prepared by self-assembling of [Mo(CN)₈]^3? and Mn²⁺ ions. The compound crystallized in the trigonal system with space group R-3 and cell dimensions of a = b = 26.182(15), c = 25.586(14) Å, γ = 120°, and Z = 18. The structure of the complex consists of neutral cluster of 15 metal ions, in which all metal ions are linked by cyanide bridged ligands. Magnetic susceptibilities and magnetization measurements of the complex indicate that the cluster has an S = 39/2 ground state. The intracluster ferrimagnetic interaction has been characterized as well.     

Diphenyl diselenide grafted onto a Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>-chitosan composite as a new nanosorbent for separation of metal ions by effervescent salt-assisted dispersive magnetic micro solid-phase extraction

Diphenyl diselenide was immobilized on chitosan loaded with magnetite (Fe₃O₄) nanoparticles to give an efficient and cost-effective nanosorbent for the preconcentration of Pb(II), Cd(II), Ni(II) and Cu(II) ions by using effervescent salt-assisted dispersive magnetic micro solid-phase extraction (EA-DM-μSPE). The metal ions were desorbed from the sorbent with 3M nitric acid and then quantified via microflame AAS. The main parameters affecting the extraction were optimized using a one-at-a-time method. Under optimum condition, the limits of detection, linear dynamic ranges, and relative standard deviations (for n?=?3) are as following: Pb(II): 2.0 ng·mL^?1; 6.3–900 ng·mL^?1; 1.5%. Cd(II): 0.15 ng·mL^?1; 0.7–85 ng·mL^?1, 3.2%; Ni(II): 1.6 ng·mL^?1,.6.0–600. ng·mL^?1, 4.1%; Cu(II): 1.2 ng·mL^?1, 3.0–300 ng·mL^?1, 2.2%. The nanosorbent can be reused at least 4 times.

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Graphical abstract Fe₃O₄-chitosan composite was modified with diphenyl diselenide as a sorbent for separation of metal ions by effervescent salt-assisted dispersive magnetic micro solid-phase extraction.

     

The oscillopolarographic determination of uranium and thorium in supporting electrolytes containing cupferron

Uranium(VI and IV) and thorium(IV) give cathodic indentations in supporting electrolytes prepared from 0.1M perchloric acid, 0.5 M ammonium thiocyanate and 5·10^-3M cupferron (solution A) or from 0.1 M succinic-succinate buffer pH 4, 0.1 M sodium chloride, 10^-3M cupferron and 0.05% gelatine (solution B). The uranium indentation on the dE/dt = f(E) curve (Q=0.75 and 0.73) permits its detection at the 3·10^-7M level. The thorium indentation (Q=0.78) permits its detection at the 4·10^-7M level in solution B. Methods for the elimination of interfering ions for the uranium determination are described. In the determination of thorium, Ga(III), Fe(III), Ti(IV) and U(VI) interfere.     

Solution Equilibria and Thermodynamic Studies of Complexation of Divalent Transition Metal Ions with Some Triazoles and Biologically Important Aliphatic Dicarboxylic Acids in Aqueous Media

The formation of binary and ternary complexes of the divalent transition metal ions Cu^II, Ni^II, Zn^II, and Co^II with some triazoles [1,2,4-triazole (TRZ), 3-mercapto-1,2,4-triazole, and 3-amino-1,2,4-triazole], and the biologically important aliphatic dicarboxylic acids adipic, succinic, malic, malonic, maleic, tartaric, and oxalic acid, was investigated in aqueous solutions using the potentiometric technique at 25 °C and I = 0.10 mol·dm^?3 NaNO₃. The formation of 1:1 and 1:2 binary complexes and 1:1:1 ternary complexes was inferred from the corresponding titration curves. The formation of ternary complexes occurs in a stepwise manner with the carboxylic acids acting as primary ligands. The ionization constants (pK _a) of the investigated ligands were redetermined and used for determining the stability constants of the binary and ternary complexes formed in solution. The order of stability of the ternary complexes was investigated in terms of the nature of the triazole, carboxylic acid and metal ion used. The ?log₁₀ K values, percent relative stabilization, and log₁₀ X for the ternary complexes have been evaluated and discussed. The concentration distributions of the various species formed in solution were evaluated. The ionization constants of TRZ and malic acid and stability constants of their binary and ternary complexes with Cu^II, Ni^II, and Co^II metal ions were studied at four different temperatures (15, 25, 35, and 45 °C) and the corresponding thermodynamic parameters have been evaluated and discussed. The complexation behavior of ternary complexes was ascertained using conductivity measurements. In addition, the formation of ternary complexes in solution has been confirmed by using UV–visible spectrophotometry.     

Isodimorphism of the salts 2RbCl · MIICl2 · 2H2O (MII = Mn,Fe, Co,Cu)

The three-component systems RbClMnCl₂H₂O, 2RbCl · CoCl₂ · 2H₂O2RbCl · CuCl₂ · 2H₂OH₂O, 2RbCl · CoCl₂ · 2H₂O2RbCl · MnCl₂ · 2H₂OH₂O have been studied at 25°C. In the 2RbCl · CoCl₂ · 2H₂O2RbCl · CuCl₂ · 2H₂OH₂O system, a discontinuous series of mixed crystals is formed and in the 2RbCl · CoCl₂ · 2H₂O2RbCl · MnCl₂ · 2H₂OH₂O system, a continuous series is present.The unit cell parameters of the 2RbCl · CoCl₂ · 2H₂O double salt were determined: a = 5.586(2) Å, b = 6.469(3) Å, c = 6.988(2) Å, α = 65.31(3)°, β = 87.69(3)°, γ = 84.65(4)°, volume 228.4 ų, Z = 1.The results obtained and discussed in conjunction with the crystal structure data suggest that for 2M^ICl · M^IICl₂ · 2H₂O type salts the triclinic structure is stable only when the large rubidium and cesium ions participate in combinations with non-Jahn-Teller metal(II) ions. In the cases of Jahn-Teller metal(II) ions or with potassium or ammonium ions a tetragonal structure is always stable.     

铝(Ⅲ)与脱铁伴清蛋白结合的紫外差光谱研究

在 pH7.4、 0.1mol· L~(－1)N-2-羟乙基哌嗪- N′-2-乙磺酸（ Hepes）及室温条件下,使用紫外吸收差光谱进行了铝(Ⅲ)对脱铁伴清蛋白的滴定。结果表明铝(Ⅲ)与脱铁伴清蛋白结合后其紫外差光谱在 238nm和 291nm处出现吸收峰。在 238nm处铝(Ⅲ)-脱铁伴清蛋白配合物的摩尔吸光系数是 (1.52± 0.04)× 10~4cm~(－1)· mol~(－1)· L。铝(Ⅲ)可占据脱铁伴清蛋白的两个金属离子结合部位,条件稳定常数是 lgK_N=11.21± 0.12,lgKC=9.53± 0.24。 N-端单铁伴清蛋白的紫外差光谱滴定表明,铝 ?优先占据脱铁伴清蛋白的 N端结合部位。     

Development of Fluorescent Film Sensors Based on Electropolymerization for Iron(III) Ion Detection

Two electroactive materials, M1 and M2 , are synthesized and their fluorescent electropolymerized (EP) films are prepared and used to detect metal ions. From the tested metal ions, M1 and M2 are demonstrated to be sensitive and selective for Fe³⁺ ions. In particular, M2 exhibits higher sensitivity towards Fe³⁺ ions. The fluorescent detection ranges from 10^?5 M to 4×10^?4 M . The excellent performance of the EP fluorescent films is mainly due to the strong metal‐chelated properties of M2 and the intrinsic porous cross‐linked‐network microstructure of the EP films. This study, thus, provides a promising Fe³⁺ sensing candidate and a potential preparation method for fluorescent sensing films.     

A new lawsone azo-dye for optical sensing of Fe3+ and Cu2+ and their DFT study

A new lawsone-based azo-dye 2-hydroxy-3-((pyridin-2-ylmethyl)diazenyl)naphthalene-1,4-dione (1) was synthesized and applied for sensing of metal ions. Receptor 1 showed selective fluorescent and colorimetric response for the detection of Cu²⁺ and Fe³⁺ over other tested metal ions. The fluorescence intensity of 1 was significantly quenched allowing detection of Fe³⁺ and Cu²⁺ down to 0.61 and 6.06 μM, respectively. The binding has been established by fluorescence spectroscopic method. Receptor 1 provided a 1?:?1 binding scaffold for recognition of Fe³⁺ and Cu²⁺ ions with the association constant of 3.33 × 10⁶ and 3.33 × 10⁵ M^?1, respectively. The B3LYP/6-31G/LANL2DZ method was employed for the optimization of 1 and 1·Fe³⁺ and 1·Cu²⁺.     

Trifluoroacetate ion-selective electrode

The trifluoroacetate ion-selective electrode was prepared by using the organic solvent solution of trifluoroacetate salt of crystal violet or tris(bathophenanthroline) iron(II) chelate.The response is linear over the activity range 10^?1 to 3 × 10^?5M, with a Nernstian slope 60 mV/activity decade at 29 °C. The interferences of divalent ions, chloride, fluoride and acetate ions are extremely low. Iodide interferes greatly.     

Drop-scale chronopotentiometry

Chronopotentiometry has been successfully carried out on one drop of solution. A simple arrangement enabled determinations to be performed in one to two minutes. A potential holdup was clearly indicated for the oxidation of iodide ions on electrolyzing 0.07 ml of a 5·10^-6M potassium iodide solution 1M in sulfuric acid, a total of 3.5·10^-10 equivalents of iodide ions.     

Substituted 2-thiophenealdehyde-2-benzothiazolyl-hydrazones as analytical reagents for copper

The analytical properties of 5-chloro-, 5-bromo- and 5-methyl-2-thiophenealdehyde-2-benzothiazolylhydrazone (CTBH, BTBH and MTBH, respectively), are compared with those of 2-thiophenealdehyde-2-benzothiazolylhydrazone (TBH). The acid dissociation constants have been determined, and the 5-substituent effect is discussed. The complex formation of the reagents with several metal ions has been examined spectrophotometrically. Extraction—spectrophotometric determinations of traces of copper are proposed. The copper complexes can be extracted quantitatively into benzene over wide pH ranges (from weakly acidic to alkaline medium) and the molar absorptivities are high (4–5· 10⁴ l mol^-1 cm^-1). The complexes formed are 1:2 (copper:ligand) in all cases. There are few interferences from common ions except silver(I), mercury(II), thiocyanate and citrate.     

Spectrophotometric study and extraction of niobium(V) complexes with catechol and its derivatives as ion-pairs with quaternary ammonium ions: Application to the separation of niobium from other refractory metal ions

The reactions of niobium(V) with catechol and several substituted derivatives were studied. Optimal conditions for colour development in the niobium(V)-catechol system are: pH 6.7–8.0, and heating at 85° for at least 6 min; the wavelength of maximal absorption is 365 nm, and the molar absorptivity is 1.02·10⁴. Catechol derivatives require lower temperatures and develop colours with niobium(V) in neutral or slightly acidic solutions. The best of the derivatives studied were 3-methyl-catechol and 4-chlorocatechol. Extraction of the ion-pairs formed between niobium-(V)-catechol and different quaternary ammonium ions, was studied with representative solvents. Similar studies were made on other refractory metal ions, i.e., Ti(IV), V(V), Mo(VI) and W(VI), under the optimal conditions for the reaction with niobium(V). Separations of binary (1:1) mixtures of niobium(V) with Ti(IV), V(V), Mo(VI) or W(VI) at the 5·10^-5M level were shown to be possible under the predicted conditions.