Spectrophotometric determination of molybdenum with phenylfluorone

Spectrophotometric studies on the reaction between molybdenum as molybdate (MoO₄^2?) and phenylfluorone are presented. The reaction conditions are optimized to develop an intense color (molar absorptivity is 3.8 × 10³) selective and sensitive for the Spectrophotometric determination of molybdenum. The absorbance is measured at 560 nm, at a pH of 1.5–3. The colored complex is stable for up to 24 hr, Beer's law is obeyed, over the concentration range of 1 to 4 μg/25 ml. The relative standard deviation is 2% and the sensitivity of the method is 1.60 × 10^?4 mg/ml.     

Dynamic equilibrium of ion exchange in the system lead-cation exchanger at different temperatures

Summary The relationship between the ion-exchange reaction in a column and temperature was examined in the system lead-ion exchanger resin Lewatit S 1080. Lead binding was performed with 0.01 mol/l HNO₃ and elution with 4.0 mol/l HCl. The working temperature was gradually increased from 273 to 333 K. Thermostat columns were of own construction. The results were statistically analysed and graphically presented and the parameters obtained for elution curves were related to temperature. The elution curves were found to be temperature specific. The parameters such as elution band width, distribution factor, maximal volume of the eluate, maximal lead concentration in the eluate, confirmed this fact. At higher temperatures, larger volumes of elution solution were required for the elution of the same quantity of lead.

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Ionenaustausch im System Blei-Kationischer Austauscher bei verschiedenen Temperaturen

     

Microcalorimetric investigation of the growth of the <Emphasis Type="Italic">Escherichia coli</Emphasis> DH5α in different antibiotics

The effects of Amoxicillin Sodium and Cefuroxime Sodium on the growth of E. coli DH5α were investigated by microcalorimetry. The metabolic power-time curves of E. coli DH5α growth were determined by using a TAM air isothermal microcalorimeter at 37°C. By evaluation of the obtained parameters, such as growth rate constants (k), inhibitory ratio (I), the maximum heat power (P _m) and the time of the maximum heat power (t _m), one found that the inhibitory activity of Amoxicillin Sodium vs. E. coli DH5α is enhanced with the increasing of the Amoxicillin Sodium concentration, and the Cefuroxime Sodium has a stimulatory effect on the E. coli DH5α growth when the concentration is about 1 μg mL⁻¹. The IC₅₀ for the Amoxicillin Sodium and the Cefuroxime Sodium are 1.6 and 2.0 μg mL⁻¹, respectively, it implicates that the E. coli DH5α is more sensitive to Amoxicillin Sodium than Cefuroxime Sodium.     

The effect of UV-irradiation on composting of polyethylene modified by cellulose

LDPE and its blend with cellulose, obtained by extrusion, were UV-irradiated with different doses or biodegraded in soil up to 1 year. Simultaneously, the same samples were 1 year biodegraded after 20 h UV pre-irradiation in the same conditions. The course of photo- and biodegradation was monitored by estimation of average molecular weights and polydispersity, gel amount, changes of PE crystallinity and mechanical properties. Moreover, the biodegradation degree was calculated on the basis of carbon dioxide evolved and surface morphological changes were observed by SEM. It was found that biodegradation of PE + cellulose is hampered by intermolecular crosslinking of both components. Although, the rate of decomposition of PE + cellulose blends is low it is enough for disintegration of such materials in the natural environment.     

Treatment of coke plant wastewater by A/O fixed biofilm system

The long-term environmental impacts of wastewa-ter from coke plant can be very high, especially due to the discharge of large amounts of wastewater. The composition of coke plant wastewater is complicated and varies from one factory to another, depending …     

Current mass spectrometry strategies for selenium speciation in dietary sources of high-selenium

This document reviews the most relevant mass spectrometry approaches to selenium (Se) speciation in high-Se food supplements in terms of qualitative and quantitative Se speciation and Se-containing species identification, with special reference to high-Se yeast, garlic, onions and Brazil nuts. Important topics such as complexity of Se speciation in these materials and the importance of combining Se-specific detection and molecule-specific determination of the particular species of this element in parallel with chromatography, to understand their nutritional role and cancer preventive properties are critically discussed throughout. The versatility and potential of mass spectrometric detection in this field are clearly demonstrated. Although great advances have been achieved, further developments are required, especially if speciatedcertified reference materials (CRMs) are to be produced for validation of measurements of target Se-containing species in Se-food supplements.     

Electrochemical and structural investigations of oxide films anodically formed on ruthenium-plated titanium electrodes in sulfuric acid

The electrochemical characteristics of ruthenium oxides, formed on Ru-plated Ti electrodes in 0.5 M H₂SO₄ by potential cycling with different CV upper potential limits (E _SU), were systematically compared. The repeated potential cycling between 0.2 and 0.75 V activated the formation/reduction of surface Ru oxides with hysteretic behavior. This application of repeated CVs also modified the ability of Ru deposits for hydrogen adsorption/desorption. An irreducible Ru oxide accumulated on the electrode at potentials more positive than ca. 0.95 V, whose capacitive characteristics are applicable for electrochemical supercapacitors. This irreducible oxide was composed of an aggregate consisting of Ru in various oxidation states, bridged oxygen, OH and water in a 3D-like structure with a relatively ordered and compact nature, from the X-ray photoelectron spectroscopic and voltammetric results. The surface reconstruction of the Ru deposits induced by the repeated potential cycling with E _SU≥0.75 V was clearly observed from the SEM photographs. From the X-ray diffraction patterns, all the anodically formed Ru oxides showed an amorphous nature.     

An in situ STM study on the long-range surface restructuring of Au(1 1 1) in a non-chloroaluminumated ionic liquid

We report an in situ STM study of a potential-dependent long-range surface restructuring of Au(1 1 1) electrode in neat 1-butyl-3-methylimidazolium tetrafluoroborates (BMIBF₄) ionic liquid. Au(1 1 1) undergoes a significant long-range surface restructuring upon cathodic excursion to −1.0 V vs. Pt quasi-reference. The restructuring involves the formation of tiny pits, which then develops into a stable worm-like network with an average width of the network grids 2 nm. Electrochemical annealing occurs at the cathodic limit with the presence of a reduction product of cation BMI⁺. A smooth surface is recovered with the appearance of the typical (√3 × 22) reconstruction of Au(1 1 1). The surface restructuring is reestablished upon anodic excursion to −1.3 V after the adsorbed reduction product is oxidized. The long-range surface restructuring phenomenon is tentatively explained as a result of partial charge transfer to the weakly adsorbed BMI⁺, which reduces the metal–metal cohesive energy. In addition, the synergetic effect of the counter anion BF₄⁻ may also be involved. The results provide a knowledge of Au(1 1 1) electrode behavior in the neat ionic liquid and are beneficial to understanding in situ STM results involving surface morphological changes in such a media.     

H-quadrupolar coupling-based analysis of stereochemical and regiochemical memory in the Pd-catalysed allylic alkylation of iso-cinnamyl type substrates employing the chiral monophosphine ligands ‘MOP’ and ‘MAP’

The reaction of iso-cinnamyl acetate with NaC(Me)(CO₂Me)₂, catalysed by Pd-‘MOP’ (MOP=2-methoxy-2′-diphenylphosphino-1,1′-binaphthalene) is known to proceed with a regiochemical memory effect that results in the predominant generation of the branched alkylation product. The analogous reaction employing ‘MAP’ as ligand (MAP=2-N,N-dimethylamino-2′-diphenylphosphino-1,1′-binaphthalene) proceeds with ‘normal’ regioselectivity to generate predominantly the linear isomer of product. A ²H-NMR based analysis, employing quadrupolar coupling in a chiral liquid crystal matrix, has been developed to facilitate the simultaneous study of the regiochemical and stereochemical outcome of the reaction of both enantiomers of iso-cinnamyl ester substrates in ²H-labelled but racemic samples. The analysis allows the comparison of relative rates of two competing isomerisation processes occurring in the π-allyl intermediates in the Pd-catalysed reaction, one of which facilitates asymmetric induction, the other resulting in loss of regiochemical memory. It is demonstrated that the two processes are partially coupled and that this then limits the attainment of high global enantiomeric excess in the branched product to reactions that proceed with low regiochemical retention. A key factor for the observation of high regiochemical memory is found to be the nucleophilicity of the malonate anion and the electrophilicity of the Pd-π-allyl intermediate with reduction in the reactivity of either partner resulting in the onset of substantial loss of memory.     

Synthesis and some properties of phosphorus-substituted azomethines

A series of phosphorus(iii)-substituted azomethines and enamines were synthesized by the reaction of lithium salts of aldimines and ketimines with derivatives of phosphorus(iii) acids. Some properties of the compounds synthesized were studied. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 339–346, February, 1998.