Spektroskopische Untersuchungen der Metallkomplexe des 2,5-Dibenzoyl-3,4-dihydroxyselenophens

Zusammenfassung Eine Reihe von Metallkomplexen des 2,5-Dibenzoyl-3,4-dihydroxy-selenophens wurden spektroskopisch untersucht. Das Verhalten des Wismutkomplexes und die Möglichkeiten einer spektrophotometrischen Wismutbestimmung auf diesem Wege wurden eingehend studiert.

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Summary A spectroscopic examination was made of a series of metal complexes of 2,5-dibenzoyl-3,4-dihydroxyselenophen. The behavior of the bismuth complex and the possibilities of a spectrophotometric method of determining bismuth in this manner were studied thoroughly.

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Herrn Univ.-Prof. Dr.Hans Lieb zum 80. Geburtstag gewidmet.     

Investigation of the Flavonoids in Croatian Propolis by Thin-Layer Chromatography

JPC – Journal of Planar Chromatography – Modern TLC - Flavonoids and phenolic acids with a variety of biological activity are considered to be the main compounds in propolis–a...     

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     

Correlation of unified retention indices for OV-101 and squalane

Summary Gas chromatographic unified retention indices for 43 hydrocarbons (alkanes and cycloalkanes) are given for squalane and OV-101. Comparison of these values and unified retention index increments are presented as linear regression equations with high correlation coefficients and acceptable standard deviations.     

Solvent extraction and radiometric determination of3H-stobadine in biological material

A simple and rapid radiochemical method for the efficient and selective isolation of³H-stobadine from plasma, urine and organ homogenates has been developed. The method comprises the extraction of³H-stobadine from the biological matrix containing 2M Na₂CO₃ into n-hexane followed by scrubbing of partly coextracted metabolites into an equal volume of 2M Na₂CO₃. The specificity of the procedure presented is demonstrated by TLC and the comparison of distribution coefficients of authentic and apparent (isolated) substances.     

Air/polymer distribution coefficients for polycyclic aromatic hydrocarbons by solid-phase microextraction sampling

Two methods to estimate distribution coefficients (K) between air and poly(dimethylsiloxane) (PDMS) coating of solid-phase microextraction (SPME) fibers for eight low molecular polycyclic aromatic hydrocarbons (PAHs) there are presented. The PDMS phases were used for determination of the coefficients according to equilibrium theory with help of a developed static calibration system (SCS). Another way to estimate the coefficients is based on the use of a linear relationship between the logarithm of the coefficients (log K) and linear temperature-programmed retention indexes (LTPRI) of the compounds without necessity to calibrate. The log K values for both of methods ranged from 5.2 (naphthalene) to 8.9 (pyrene) at 22 degrees C. Relative standard deviation (R.S.D.) of log K for each compound determined by static calibration was no more than 5.3%. R.S.D. of retention times for LTPRI indices did not exceed 0.28% for repeated injection. All experiments were implemented on a GC-MS system.     

Preparation and practical application of spinel pigment Co0.46Zn0.55(Ti0.064Cr0.91)2O4

Synthesis of the green spinel pigment Co_0.46Zn_0.55(Ti_0.064Cr_0.91)₂O₄ by a novel two-step method of preparation have been investigated. Inorganic pigments are almost always prepared by a solid state reaction. It is classical ceramic method which used oxides, hydroxides or carbonates as precursors. The reaction is performed at temperature higher than 1300°C and an agent of mineralization is usually present. The presented novel method of preparation decreases the calcining temperature necessary for reaching of bright and clear hue of the pigments prepared. Main attention was focused on the influence of two types of titanium raw materials on the temperature region of the spinel structure formation and on the colour properties of the pigments. The mixture of precursors with TiO₂ gives a one-phase system when calcining at 1100°C but the colour properties are more interesting at 1150°C. Thermal stability of this pigment is limited by temperature 1300°C. This temperature is connected with partial oxidation of Cr(III) to Cr(VI). Thermal analysis provided the first information about the temperature region of the pigment formation and determined the thermal stability of pigment.     

A test for monitoring traces of cholinesterase inhibitors in surface waters

Summary The inhibitory effect on cholinesterase activity is the only common attribute of organophosphorus pesticides and carbamates. Therefore a screening test based on cholinesterase assay is suitable for detection of total pesticides in the pollution control of surface waters. The reaction-rate cholinesterase assay in which acetylthiocholine iodide is used as substrate and 5,5-dithio-bis (2-nitrobenzoic acid) (Ellman's reagent) as indicator, with spectrophotometric monitoring at 412 nm for 2 min is applied. The detection limits for various pesticides in aqueous solutions have been determined. The results are comparable to those of gas Chromatographic analyses and for carbamates are even better. The sensitivity can be improved by two orders of magnitude by preconcentration on Amberlite XAD-4 column. The collection efficiency of about 80% for all the pesticides tested has been confirmed by gas chromatography. A rapid and simple field test is based on the same assay system. The reaction is stopped by complete inhibition of the enzyme and the colour is compared visually with that of standards prepared by dilution of the initial enzyme solution, and the comparison is facilitated by use of a red filter (_max 555 nm). A relative standard deviation of 5.5% was obtained for 3 series of sample covering the range 0–100% inhibition, 9 experiments done by 6 persons.

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Nachweis von Spuren Cholinesterase hemmender Faktoren in Oberflächenwässern

Zusammenfassung Der hemmende Effekt gegenüber Cholinesterase ist das einzige gemeinsame Kennzeichen phosphor-organischer Pestizide und Carbamate. Der Nachweis mit Cholinesterase eignet sich daher für den Nachweis von Pestiziden bei der Reinheitskontrolle von Oberflächengewässern. Der Nachweis mit Acetylthiocholinjodid als Substrat und 5,5-Dithio-bis(2-nitrobenzoe-säure) (Ellmans Reagens) als Indikator durch spektrophotometrische Bestimmung bei 412 nm wurde angewendet. Die Erfassungsgrenzen für verschiedene Pestizide in wäßriger Lösung wurden bestimmt. Die Ergebnisse sind mit denen gaschromatographischer Analysen vergleichbar, für Carbamate sogar besser. Die Empfindlichkeit kann durch Anreicherung mit Amberlit XAD-4 um zwei Größenordnungen verbessert werden. Die Anreicherung um ungefähr 80% wurde gaschromatographisch für alle untersuchten Pestizide bestätigt. Ein schneller und einfacher Feldversuch beruht auf demselben Reaktionsvorgang. Die Reaktion wird durch vollständige Hemmung des Enzyms abgebrochen und die Farbe visuell verglichen mit verdünnten Standardlösungen der ursprünglichen Enzymlösung. Dieser Vergleich wird durch ein Rotfilter (_max 555 nm) erleichtert. Eine relative Standardabweichung von 5,5% wurde für 3 Probenreihen mit einem Hemmungseffekt von 0–100% erhalten, wobei 6 Personen 9 Versuche durchführten.

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Presented at the 8th International Microchemical Symposium, Graz, August 25–30, 1980.     

Thermal Analysis of the System Na3AlF6–NaVO3

Summary. The phase diagram of the system Na₃AlF₆–NaVO₃ was determined by means of thermal analysis. The system is a simple binary eutectic one. The eutectic point was estimated at x(NaVO₃) = 0.975 and t _eut = 617°C. The XRD patterns of samples after thermal analysis revealed the presence of cryolite and NaVO₃ only supporting the above assumption of a simple eutectic binary system.     

Book review

S. E. J_rgensen and Yu. M. Svirezhev Towards a Thermodynamic Theory for Ecological Systems Elsevier, Amsterdam 2004, Price: paperback 85€; hardbound 140€, 350 (A4 size) pages