Testing the photocatalytic activity of cyanogen-and thiocyanogen-based inorganic polymers

The photocatalytic properties of some cyanogen-and thiocyanogen-based inorganic polymers, such as paracyanogens containing different metals (Hg, Ag, Cu), polythiocyanogens of different iodine contents, polycyanogen and poly (cyanogenthiocyanate), have been tested in two systems. Cu-containing paracyanogen and the iodine-poor polythiocyanogens catalyze the photoreduction of methylviologen under visible light, furthermore the Cu-containing paracyanogen catalyzes the photoreduction of water to hydrogen under UV irradiation.

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Preparation and sedimentation behavior in magnetic fields of magnetite-covered clay particles

This work is devoted to the preparation of magnetite-covered clay particles in aqueous medium. For this purpose, magnetite nanoparticles were synthesized by a coprecipitation method. These magnetic particles are adhered to sodium montmorillonite (NaMt) particles in aqueous suspensions of both materials, by appropriate control of the electrolyte concentrations. The best condition to produce such heteroaggregation corresponds to acid pH and approximately 1 mol/L ionic strength, when the electrokinetic potentials (zeta-potential) of both NaMt and Fe3O4 particles have high enough and opposite sign, as demonstrated from electrophoresis measurements. When a layer of magnetite re-covers the clay particles, the application of an external magnetic field induces a magnetic moment in clay-magnetite particles parallel to the external magnetic flux density. The sedimentation behavior of such magnetic particles is studied in the absence or presence of an external magnetic field in a vertical direction. The whole sedimentation behavior is also strongly affected by the formation of big flocculi in the suspensions under the action of internal colloidal interactions. van der Waals and dipole-dipole magnetic attractions between magnetite-covered clay particles dominate the flocculation processes. The different relative orientation of the clay-magnetite particles (edge-to-edge, face-to-edge, and face-to-face) are discussed in order to predict the most favored flocculi configuration.     

High-performance liquid chromatographic determination of glycogen in sea urchin gonads with refractive index detection

A high-performance liquid chromatographic method using refractive index detection for the determination of glycogen in sea urchin (Paracentrotus lividus) gonads is developed. After alkaline digestion with sodium carbonate, samples are adjusted to pH 4.6 with citric acid and incubated with amyloglucosidase to hydrolyze the glycogen. The resulting glucose is determined using a Spherisorb NH2 column as the stationary phase and an acetonitrile-water mixture (80:20, v/v) as the mobile phase. The relative standard deviation (%) was 3.57, the limit of detection was 40.1 microg/mL, and the recovery percentage was 97.2%.     

On the extraction with long-chain amines

The extraction of tracer mercury(II) from aqueous HCl-solutions by TLA (trilaurylamine) dissolved in benzene can simply be described by the reaction (1) $$TLAHCl \cdot H_2 O(org) + HgCl_2 (aq) \rightleftharpoons TLAHCl \cdot HgCl_2 (org) + H_2 O(aq)$$ Using the chloride ion activity coefficient function recently introduced by HÖGFELDT (2) $$\lg y_{Cl^ - } = - 0.5115 \sqrt I /(1 + 1.176 \sqrt I ) - \lg C_{corr} $$ together with the model for excess acid extraction developed by AGUILAR and HÖGFELDT, the only unknown quantity is the equilibrium constant for the reaction above since the stability constants for the formation of the Hg(II)-CT-complexes are also well known. Using distribution data for HgCl₂ (tracer) between HCl-solutions and benzene Eq. (2) gets further support as being a useful expression for the activity coefficient of Cl^? in solutions more concentrated than ≈0.6M. Some scouting experiments about the extraction of HgCl₂ from NaCl brines containing 270 g NaCl/l showed that in the pH-range 1–13 the best extraction was obtained at about pH 1–2 irrespective if the diluent was benzene, o-xylene or a mixture of kerosene and benzene.     

High-Performance Liquid Chromatographic Analysis of Amino Acids in Edible Seaweeds after Derivatization with Phenyl Isothiocyanate

Summary A reversed-phase high-performance liquid-chromatographic method has been used for analysis of the amino acids in edible seaweed. Sample proteins were hydrolysed with hydrochloric acid and the amino acids produced were derivatized with phenyl isothiocyanate. The resulting phenylthiocarbamyl amino acids were chromatographed on an ODS2 column with UV detection at 254 nm. The mobile phase was a mixture of 0.14 M ammonium acetate buffer, pH 6.4, containing 0.05% triethylamine (A) and 60:40 (v/v) acetonitrile–water (B), at a flow rate of 1.1 mL min^–1; the elution gradient (min:A%) was: 0:90, 8:90, 10:70, 12:70, 18:52, 20:0, 25:0, 28:90, 35:90. Method precision for the different amino acids was between 1.33 and 3.88% (relative standard deviation); detection limits were between 6.9 and 14.3 ng mL^–1. The amino acid content of the algae analysed ranged from 22.4 ± 1.9 to 138.0 ± 5.6 mg g^–1 d.w. The amino acids present at highest concentrations were glutamic acid, alanine, and phenylalanine.     

Direct versus resonances mediated F+OH collisions on a new 3A" potential energy surface

A theoretical study of the F(2P) + OH(2Pi) --> HF(1Sigma+) + O(3P) reactive collisions is carried out on a new global potential energy surface (PES) of the ground 3A" adiabatic electronic state. The ab initio calculations are based on multireference configuration interaction calculations, using the aug-cc-pVTZ extended basis sets of Dunning et al. A functional representation of the PES shows no nominal barrier to reaction, contrary to previous results by others. Wave packet and quasiclassical trajectory calculations have been performed for this PES to study the F + OH(v = 0,j) reactive collision. The comparison was performed at fixed and constant values of the total angular momentum from 0 to 110 and relative translational energy up to 0.8 eV. The reaction presents a dynamical barrier, essentially due to the zero-point energy for the bending vibration near the saddle point. This determines two different reaction mechanisms. At energies higher than approximately 0.125 eV the reaction is direct, while below that value it is indirect and mediated by heavy-light-heavy resonances. Such resonances, also found in the simulations of the photodetachment spectrum of the triatomic anion, manifest themselves in the quasiclassical simulations, too, where they are associated to periodic orbits.     

Radiotracer method for the study of the radiolysis of aqueous solutions of pyruvic acid

The purpose of this work is to study the radiolytic behavior of aqueous solutions of¹⁴C-pyruvic acid (oxygen-free). Several parameters were varied such as radiation dose, pH, etc. Gas chromatography, mass spectrometry and high performance liquid chromatography were used extensively for the analysis of radiolytic products. The more abundant product was dimethyltartaric acid. Other products identified were acetic, lactic, succinic, malonic and tricarballylic acids, acetaldehyde, carbon dioxide, and hydrogen. The yields of these products were influenced by the irradiation dose, concentration of the target compound and pH of the solution.