TLC Separation and Identification of Heavy Metals Present in Cotton Material

JPC – Journal of Planar Chromatography – Modern TLC - Optimization of the separation and identification of heavy metals present in cotton material has been performed by...     

The Influence of Cobalt (II) in Carboxymethyl Cellulose Processing

Controlling the reduction in molecular weight of the cellulose chains is essential in the production of carboxymethyl cellulose (CMC). Such a reduction can be achieved by the addition of cobalt during the process of cobalt(II) ions, which act as a catalyst for oxidative cleavage, and the influence thereof has been studied under a variety of conditions. This study has resulted in a model that summarises the effects of the added amount of cobalt, the time for the cobalt reaction, the temperature in the mercerisation stage of the CMC-manufacturing process and finally the effect of the temperature in the etherification stage. It is shown that it is important for cobalt to be present during the mercerisation stage in order to achieve the desired viscosity.     

Influence of boric acid on the determination of iron in reactor coolant water by graphite furnace atomic absorption spectrometry

Summary The matric effect of boric acid was investigated in the determination of iron in the primary circuit coolant water of nuclear power plants by furnace atomic absorption spectrometry. The effect of boric acid was of particular interest. The method was applied during refuelling and maintenance periods and the results were used to interpret the chemical changes in the water.

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Einfluß von Borsäure auf die Bestimmung von Eisen in Reaktorkühlwasser durch GF-AAS

     

A Chiral Coordination Polymer of Silver(I) with Saccharinate and Pyridine: Synthesis,Spectral, Thermal,and Structural Characterization of [Ag(sac)(py)]<Subscript><Emphasis Type="Italic">n</Emphasis></Subscript>

The first silver(I) complex of saccharinate (sac) with pyridine (py), [Ag(sac)(py)]_n has been synthesized and characterized by elemental analysis, IR spectroscopy and single crystal X-ray diffractometry. The complex crystallizes in chiral, trigonal space group P3₁21 (No. 152) with unit cell parameters of a = 11.2605(2) Å, c = 17.3300(4) Å, V = 1903.02(6) ų and Z = 6. [Ag(sac)(py)]_n contains monomeric [Ag(sac)(py)] units linked into infinite helices by way of Ag⋅sAg interactions [d(Ag⋅sAg) = 2.909(2) and 2.985(1) Å]. The distorted square-planar environment of Ag is completed by an N-bonded sac [Ag—N = 2.084(2) Å] and a py molecule [Ag—N = 2.116(2) Å]. The N_sac—Ag—N_py angle is 173.85(10)^∘. The one-dimensional chains are crosslinked by C—H⋅sO interactions involving the carbonyl and sulfonyl O atoms of sac and aromatic-ring hydrogen atoms of both sac and py. The thermal stability of the title complex was investigated using thermogravimetry and differential thermal analysis in a static atmosphere of air. The first decomposition stage between 90 and 160^∘C corresponds to removal of the py molecule in a single stage, while the degradation of the sac moiety occurs at two stages in the temperature range 370–515^∘C, giving an end product of metallic Ag.     

Time-resolved enzymatic determination of glucose using a fluorescent europium probe for hydrogen peroxide

An enzymatic assay for glucose based on the use of the fluorescent probe for hydrogen peroxide, europium(III) tetracycline (EuTc), is described. The weakly fluorescent EuTc and enzymatically generated H₂O₂ form a strongly fluorescent complex (EuTc–H₂O₂) whose fluorescence decay profile is significantly different. Since the decay time of EuTc–H₂O₂ is in the microseconds time domain, fluorescence can be detected in the time-resolved mode, thus enabling substantial reduction of background fluorescence. The scheme represents the first H₂O₂-based time-resolved fluorescence assay for glucose not requiring the presence of a peroxidase. The time-resolved assay (with a delay time of 60 s and using endpoint detection) enables glucose to be determined at levels as low as 2.2 mol L^–1, with a dynamic range of 2.2–100 mol L^–1. The method also was adapted to a kinetic assay in order to cover higher glucose levels (mmol L^–1 range). The latter was validated by analyzing spiked serum samples and gave a good linear relationship for glucose levels from 2.5 to 55.5 mmol L^–1. Noteworthy features of the assay include easy accessibility of the probe, large Stokes shift, a line-like fluorescence peaking at 616 nm, stability towards oxygen, a working pH of approximately 7, and its suitability for both kinetic and endpoint determination.     

Interactions of Some Amino Acids with Aqueous Tetraethylammonium Bromide at 298.15 K: A Volumetric Approach

The apparent molar volumes, V_,2, of glycine, L-alanine, DL--amino-n-butyric acid, L-valine, and L-leucine have been determined in aqueous 0.25, 0.75, 1.0, and 1.5 mol-dm^–3 tetraethylammonium bromide (TEAB) solutions by density measurements at 298.15 K. These data have been used to calculate the infinite dilution apparent molar volumes, V_2,m, for the amino acids in aqueous tetraethylammonium bromide and the standard partial molar volumes of transfer (_tr V_2,m) of the amino acids from water to the aqueous salt solutions. The linear correlation of V_2,m for a homologous series of amino acids has been utilized to calculate the contribution of the charged end groups (NH₃⁺, COO^–), CH₂ group, and other alkyl chains of the amino acids to V_2,m. The results of the standard partial molar volumes of transfer from water to aqueous tetraethylammonium bromide have been interpreted in terms of ion–ion, ion–polar, and hydrophobic–hydrophobic group interactions. The volume of transfer data suggest that ion–ion or ion–hydrophilic interactions are predominant in the case of glycine and alanine, and hydrophobic–hydrophobic group interactions are predominant in the case of DL--amino butyric acid, L-valine, and L-leucine.     

Five-coordinate Cobalt(II), Nickel(II) and Zinc(II) Complexes Derived from 2-pyridine-2-yl-3-(pyridine-2-carboxylideneamino)-1,2-dihydroquinazolin-4(3H)-one. The Crystal Structure of the Cobalt(II) Complex

The synthesis of cobalt(II), nickel(II) and zinc(II) complexes of 2-pyridine-2-yl-3(pyridine-2-carboxylideneamino)-1,2-dihydroquinazolin-4(3H)-one is described. The ligand and metal complexes were characterized by elemental analysis, conductivity measurements, spectral (u.v.–vis., i.r., 1D n.m.r., 2D hetcor and mass) and thermal studies. The cobalt(II) complex crystallizes as pink crystals in the monoclinic crystal system, space group P21/n with a = 10.066(6) Å, b = 15.929(9) Å, c = 12.624(7) Å, α = 90.00(9)°, β = 110.850 (8)°, γ = 90.00, V = 1891.5 (18) ų and Z = 4. The geometry around the cobalt atom is distorted trigonal bipyramidal with τ = 0.83 [structural parameter, τ = (β − α)/60; where α and β are the two basal angles in a five coordinate complex].     

Limiting Partial Molar Volumes of Electrolytes in 2-Methyl-2-Butanol <Emphasis Type="Bold">+</Emphasis> Water Mixtures at 298.15 K

Partial molar volumes at infinite dilution, V⁰₂, of alkali–metal halides (LiCl, NaCl KCl RbCl CsCl, NaBr, KBr, KI), tetra-n-alkylammonium bromides, R₄NBr (R=Me, Et, n-Pr, n-Bu, n-Pen), NaBPh₄, and Ph₄PCl have been determined in binary solvent mixtures of water with 2-methyl-2-butanol covering the water-rich region and the alcohol-rich region at 298.15 K. V⁰₂ for alkali–metal halides show relatively little dependence on the solvent composition. However, in the case of hydrophobic electrolytes the observed effects are more pronounced. A good linear dependence between V⁰₂(R₄NBr) and the molecular weight of the tetra-n-alkylammonium cation is found. Limiting single-ion volumes have been obtained using the assumption that V⁰(Ph₄P⁺)–V⁰(BPh^–₄)=2.0 cm³-mol^–1. The trends in the single-ion volumes are discussed in both solvent regions.     

Three-dimensional structural features and the toxicity of aminobenzenes and phenols

There are many organic pollutants in the environment, such as polychlorinated biphenyl, polycyclic aromatic hydrocarbons, dichlorodiphenyl-trichloroethane (DDT), and polychlorinated naphthalene. These organic pollutants are persistent,liposoluble and easily cumulated in organism; consequently, the potential toxicity will be high. Risk assessment of industrial chemicals is currently carried out using scanty experimental data, because many of these chemicals have very little or no test data. S…