Volume 60, Issue 1

A new volumetric method for monitoring the oscillating Belousov—Zhabotinsky reaction with oxalic acid is described. While an oscillatory behavior in the potential of the Pt redox electrode at slow stirring without inert gas bubbling can be observed, a monotonous, nonoscillatory course was found both at the slow and rapid stirring rates for the carbon dioxide evolution. Possible reasons for such observations are discussed.

The dissociation constants of 3-methyl-1-phenyl-{p-[N-(pyrimidin-2-yl)sulfamoyl]phenylazo}-2-pyrazolin-5-one and metal-ligand stability constants of its complexes with some transition metal ions have been determined potentiometrically in 0.1 M-KCl and ethanol—water mixture (30 vol. %). The order of the stability constants of the formed complexes increases in the sequence Mn2+, Co2+, Ni2+, Cu2+, La3+, Hf3+, UO22+, Zr4+. The effect of temperature was studied and the corresponding thermodynamic parameters (ΔG, ΔH, and ΔS) were derived and discussed. The dissociation process is nonspontaneous, endothermic, and entropically unfavourable. The formation of the metal complexes was found to be spontaneous, exothermic, and entropically favourable.

The tetranuclear Cu4OBrnCl(6-n)L4 complexes, where L = 3-methylpyridine (3-Mepy), 4-methylpyridine (4-Mepy) and n=0–6 with trigonal bipyramidal coordination of copper(II) were prepared and their infrared and electronic absorption spectra as well as cyclic voltammograms in nitromethane solutions were measured. The polyhedra in Cu4OBrnCl(6−n) (3-Mepy)4 molecules are less distorted comparing with those of 4-Mepy analogues as indicated by infrared Cu4O absorptions, far infrared Cu—Br, Cu—Cl, and Cu—N absorptions, d—d bands in electronic spectra and potentials, measured by cyclic voltammetry. The 3-Mepy complexes exhibit strong single infrared Cu4O absorptions, while for related 4-Mepy complexes doubly split Cu4O bands were observed. Two strongly overlapped d—d bands in electronic absorption spectra of the 3-and 4-Mepy complexes in nitromethane were resolved by Gaussian fitting. The 4-Mepy ligand produces slightly stronger ligand field than its 3-Mepy analogue. The maxima of high-energy d—d bands are in a linear correlation with the number of bromide ligands. The correlations for corresponding low-energy bands are considerably deviated from linearity. The halfwave potentials of the complexes in nitromethane correlate with both the number of bromides and the data of electronic absorption spectra suggesting that the reducing electron at the electrode process enters the half-filled d z 2 orbital of the copper(II) atom. The origin of a difference between the 3-and 4-Mepy complexes in their spectral and electrochemical properties is also discussed.

Two single-step extraction procedures validated by BCR, extraction with 0.43 mol dm−3 acetic acid and 0.05 mol dm−3 EDTA, are used for assessing bioavailable species of Pb and Cd in soils. After an extensive study of interferences of humic substances and using standard additions procedures, the extractable contents of Pb and Cd have been determined by DPASV directly in soil extracts with a good reproducibility (RSD varied from 1.0 to 7.9 %). Pb(II) and Cd(II) were released from complex in EDTA extracts by pH adjustment to 1 with 1 mol dm−3 HCl. The results were compared with those obtained with atomic absorption spectrometry and indicated reasonable agreement of both methods. Exchangeable forms represented 0.2 to 3.3 % and 13.0 to 63.6 % of total content of Pb and Cd in soils, respectively. EDTA extraction released from soils 7.9 to 29.9 % and 33.5 to 59.6 % of total content of Pb and Cd, respectively.

A reliable procedure for the electrothermal atomic absorption spectrometry (ETAAS) determination of gold and silver in waters at trace level is described. The method is based on prior separation and preconcentration of the metals using a chelating sorbent SPHERON® Thiol 1000 after acidification of water samples (pH < 3) with nitric acid. Optimization of analytical variables during enrichment and ETAAS determination of the metals are discussed. The accuracy of the method is verified by analysis of certified reference materials. The limits of determinations based on 10 σ definition were 0.005 ng cm−3 for Au and 0.02 ng cm−3 for Ag. Precision of studied elements determination expressed by relative standard deviation varied in the range from 2.9 % to 16.4 %.

Synthesis of N-and C-substituted derivatives of benzo[h][1,6]naphthyridine, bearing 2-hydroxyethyl group has been made by quaternization reaction and by condensation of corresponding methylbenzonaphthyridines with formaldehyde. For six derivatives of isomeric benzo[c][1,5]-, benzo[h][1,6]-, and benzo[f][1,7]naphthyridines the 13C NMR spectra are discussed. For ten compounds the geometry was optimized with the AM1 and, in one case also with the ab initio 6–31G method; their effective charge values have also been calculated.

The phenylcarbamic acid derivatives with N-phenylpiperazine moiety in the molecule have been prepared. The structure has been confirmed by elemental analysis, IR, 1H NMR, and mass spectral data. For the prepared set of the compounds the lipophilicity parameters have been determined. The experimentally obtained lipophilicity parameters have been correlated with theoretical entries obtained by different computer programs based on the neural network and fragmental methods.

Nine potential AChE reactivators were synthesized using modification of currently known synthetic pathways. Their potency to reactivate AChE inhibited by cyclosarin nerve agent was tested in vitro. According to the previous results, 1,4-bis(2-hydroxyiminomethylpyridinium)butane dibromide seems to be the most potent AChE reactivator. The reactivation potency of these compounds depends on structural factors such as presence of quaternary nitrogens, length of the linking chain between both pyridinium rings, and position of the oxime moiety at the pyridinium ring.

Condensation of quaternary 2-methylbenzothiazolium bromides with 5-(dialkylamino)furan-2-carbaldehydes afforded a series of new thiacyanine analogs. The compounds exhibit significant activities against several bacterial, yeast, and mould strains. Derivatives with dipropylamino substituents showed higher inhibitory effects than those with cyclic secondary amino groups. Hence, the biological activity may have been influenced by the lipophilicity of the compounds. The effect on growth and on the plastid system of the unicellular flagellate Euglena gracilis was also studied.

The aminothiadiazole (II) on treatment with aromatic aldehydes yielded Schiff bases, which cyclized to thiazolidinone derivatives by reaction with thioglycolic acid. Reaction of II with phenyl isocyanate and phenyl isothiocyanate afforded the carbamide and carbothiamide derivatives, respectively, which on reaction with malonic acid in acetyl chloride gave barbituric and thiobarbituric acid derivatives. However, reaction of carbon disulfide and methyl iodide with II gave dithiocarbamidate derivative which on treatment with ethylenediamine or o-phenylenediamine gave the condensed N-imidazolylthiadiazolylamine derivatives.

Medroxyprogesterone acetate (MPA), relative molecular mass is only 344.5 and it has no immunogenecity. The methods of the carbodiimides and the mixed anhydride were both adopted to couple MPA with bovine serum albumin, the carrier protein. The coupling rates of conjugate using the above methods were estimated to be 14 and 20 by ultraviolet spectrophotometry. The coupling was successful according to the analysis of SDS-PAGE illustration. New Zealand white rabbits were immunized with the conjugate the coupling rate of which was 14, and blood was collected after five periods of immunities. Then the titre of antiserum was tested to be 2.6 × 105 by indirect ELISA, which further identified the success of coupling.

The synthesis of a new epoxy resin of oligosalicylaldehyde by the reaction with epichlorohydrin is reported. New resin’s epoxy value and chlorine content were determined and found to be 25% and 1%, respectively. The characterization of the new resin was instrumented by FTIR, 1H NMR, scanning electron microscopy, and thermal gravimetric analyses. TGA results showed that the cured epoxy resin has a good resistance to thermal decomposition. The mass losses of cured epoxy resin were found to be 5%, 10%, 50% at 175°C, 240°C, and 400°C, respectively. On the curing procedure the resin was cured with polyethylenepolyamine at 25 °C for 8 h and 100°C for 1.5 h. The FTIR spectrum of new epoxy resin gave the peak of oxirane ring at ṽ = 918 cm−1.

Heterogeneous extracellular polysaccharide galactoxylomannan has been isolated from the culture medium of the acapsulated mutant Cryptococcus laurentii 17-3-6 as the main extracellular polysaccharide (90%). Size-exclusion chromatography of precipitated polysaccharides afforded two molecular fractions with molecular mass 75 kDa and 20 kDa. Mannose, galactose, glucose, and xylose ratios were 1.00: 1.16: 0.04: 0.88 and 1.00: 0.25: 0.07: 0.24, respectively.

A novel liquid chromatographic procedure is presented. It is based on differences in the transport velocities of the fast-moving, pore-excluded macromolecules and slow-progressing, pore-permeating small molecules of an auxiliary liquid. A barrier of small molecules selectively decelerates certain kind of macromolecules while other kind remains unhindered. As a result, polymers of different nature are efficiently separated. In this new approach, the barrier is formed by a zone of a non-solvent injected immediately before the sample solution. The resulting method is denoted liquid chromatography under limiting conditions of insolubility.

Particle horizontal transport and vertical entrainment of widely different materials (silica sand, alumina, ceramsite, dry sludge, and wood shreds) are explored by experimental measurements. Experiments have been performed with two very narrow fractions of solids (0.315–0.50 mm and 1.4–1.6 mm) on a laboratory setup. Simple empirical correlations are proposed in terms of the Reynolds and Archimedes criteria for the commencement of the horizontal conveying as well as the vertical entrainment of particles in pipelines.

EU energy and environmental policy in waste management leads to increasing interest in developing methods for waste disposal with minimum emissions of greenhouse gases and minimum environmental impacts. From the point of view of nitrous oxide (N2O) emissions, waste incineration and waste co-combustion is very acceptable method of waste disposal. Two factors are important for attaining very low N2O emissions from waste incineration, particularly for waste with higher nitrogen content (e.g. sewage sludge, leather, etc.): temperature of incineration over 900°C and avoiding selective noncatalytic reduction (SNCR) de-NOx method based on urea. For reduction of N2O emissions retrofitting such plants to ammonia-based SNCR is recommendable. The modern selective catalytic reduction facilities for de-NOx at waste incineration plants are only negligible source of N2O.