Composition and morphology of stack emissions from coal and oil fuelled boilers

Instrumental neutron activation analysis (INAA) together with scanning electron microscopy (SEM) have been used in the study of fly ash from large electric power and heating plants. Two basic kinds of fly ash originating either from brown coal or heavy-oil combustion can be characterized both by morphology and trace element composition. INAA technique used consisted of both short (1 min) and long (2 h) activations to ensure the determination of 30–40 elements in each fly ash sample. The average composition and determination limits obtained by INAA for coal fly ash produced in several electric power plants burning two kinds of brown coal have been compared with those obtained for fly ash originating from heating plants burning heavy-oil. Coal fly ash showed much higher concentrations of many elements especially of Sc. La, Th, Cs, Ce, Sm, Rb and Al in comparison with oil fly ash. On the other hand, the latter contained relatively high concentrations of V and Ni. The results of INAA of fly ash samples can be used for the projection of efficient separating devices and for the evaluation and prediction of contamination levels in the vicinity of large emission sources.     

Radio-high-performance liquid chromatography for ecotoxicity assessment of insect growth regulators

The described radiochromatographic method permits fast and high-sensitivity monitoring of soil biodegradation products of an insect growth regulator for its environmental risk assessment. We analyzed and compared two diastereoisomers of ethyl N-(2-(4-[(2-hydroxycyclohexyl) methyl]phenoxy)ethyl)carbamate, namely its cis-(1S,2S) isomer JN-W330 and a trans-(1R,2S) isomer JN-W331. Microbial conversion of the cis-isomer to the trans-isomer was proved by mass spectrometry analyzer. Among the chromatographic columns tested, the best separation was found with a 125 mm x 4 mm i.d. column packed with Supersphere 100 RP-C18, 5 microm and an acetonitrile-water gradient. The detection limit for the both isomers was in the range of 120-250 Bq (0.3-0.8 ng) at a concentration of 2 ng/ml with radiometric detection. The calibration curves for standard solutions were linear in the range of 150Bq-150kBq (r = 0.996). The method enabled us to compare the analyzed juvenoids with biologically active oostatic peptides in terms of their environmental safety.     

Photoinduced metalation of nonactivated C-Cl bonds with samarium diiodide: synthesis of alkenes with high (Z)-selectivity through beta-elimination reactions

[reaction: see text] The photoinduced metalation of nonactivated C-Cl bonds of O-acetyl chlorohydrins is promoted by samarium diiodide. As a result of this, beta-elimination of O-acetyl chlorohydrins is achieved, affording the corresponding (Z)-alkenes with total or high stereoselectivity.     

The first fluorogenic assay for detecting a Baeyer-Villigerase activity in microbial cells

The first fluorogenic assay allowing for detection of microbial enzymes able to perform Baeyer-Villiger oxidation is described. This is based on the use of 4-oxopentyl umbelliferyl ether 1 as a fluorogenic substrate. When Baeyer-Villigerases active against this test ketone are present in the selected whole cells, 1 is transformed into 3-hydroxypropyl umbelliferyl ether 3, which, in a subsequent step, releases the fluorescent product umbelliferone. Different microorganisms, known to be endowed with Baeyer-Villigerase activity, were assayed.     

Investigation on the chemistry of berbans—VII: Synthesis of 10,11-dimethoxy(depyrrolo)raunescine stereoisomers

Acyloxy-ketone rearrangement, proceeding by the action of base, has been observed in the case of ketone 2. By the reduction of ketones 2 and 3 with sodium boron hydride, new 10, 11-dimethoxy(depyrrolo)raunescine stereoisomers (5a–7a) have been prepared. Previously known alcohols with alloberban skeleton (12,13) have been similarly converted into tetracyclic raunescine stereoisomers (8a,9) by the oxido-reductive method. The stereochemistry of these compounds has been investigated by physical (¹H NMR, IR) and by chemical methods.     

Potentiometric studies of dithiooxamide with a sulphide-selective membrane electrode

The sulphide-selective electrode is applicable to the determination of dithiooxamide by titration with silver nitrate. The effect of the alkali content of the solutions on the reaction has been studied. The reaction products are silver sulphide, oxalic acid, and nitric acid. If the alkali concentration of the solution is lower than that equivalent to the acid formed during the titration, the amount of sulphide produced by hydrolysis decreases and the equilibrium potential is established more slowly.The determination is rapid and accurate in the presence of 1 M sodium hydroxide.     

Synthesis of benzopyran derivatives,XV Preparation of arylsulfonyloxy-2,2-dimethyl-2H-chromenes

Summary Arylsulfonyloxy-2,2-dimethyl-2H-chromenes (26–35) have been synthesized by reduction of arylsulfonyloxy-2,2-dimethyl-4-chromanones (6–15) followed by dehydration.

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Synthese von Benzopyranderviaten. 15. Mitt.: Darstellung von Arylsulfonyloxy-2,2-dimethyl-2H-chromenen

Zusammenfassung Reduktion von Arylsulfonyloxy-2,2-dimethyl-4-chromanonen (6–15) und anschließende Dehydratisierung liefert Arylsulfonyloxy-2,2-dimethyl-2H-chromene (26–35).

     

Effect of water-soluble cross-linker on the growth and properties of ethyl acrylate–methacrylic acid emulsion opolymer particles

Model ethyl acrylate–methacrylic acid copolymer latices and latices of particles cross-linked by copolymerizing small amounts of water-soluble N,N′-methylenebisacrylamide were prepared by nonseeded semicontinuous emulsion copolymerization. Dynamic and static light scattering measurements indicated a slightly higher degree of polydispersity in the case of cross-linked particles, especially in the initial stages of polymerization. The hydrodynamic volume of the alkalinized particles controlling the viscosity properties of the dispersions decreased with the time of polymerization and in the case of cross-linked copolymer almost reached a constant value at about 1 h. The different character of the particle structure was confirmed by differences in particle disintegration after alkali addition or in the presence of methanol. Received: 2 February 1999/Accepted: 28 June 2000     

Determination of Low Contents of Fenpiverine Bromide by Extraction Spectrophotometry

An ion-pair extraction spectrophotometry method was developed for the determination of fenpiverine bromide in tablets. To determine this substance it was necessary to find experimental conditions that would allow eliminating the influence of other components of the tablets. Attention was paid to the fact that a suitable pH of water phase was necessary to achieve high selectivity.Received December 11, 2002; accepted April 24, 2003 Published online July 28, 2003