ansa-Metallocene derivatives: VIII. Syntheses and crystal structures of ethylene-bridged titanocene and zirconocene derivatives with permethylated ring ligands

Ethylene-bridged titanocene and zirconocene derivatives with permethylated ring ligands, C₂H₄(C₅(CH₃)₄)₂TiCl₂ and C₂H₄(C₅(CH₃)₄)₂ZrCl₂, have been synthesized and their crystal structures determined.     

Zur Bestimmung von Ammoniak in Lebensmitteln

Zusammenfassung In einer Vakuumapparatur mit modifizierter Destilliervorlage wurden die für ein schonendes Verfahren optimalen Destillationsbedingungen zur quantitativen Freisetzung geringer Ammoniakmengen ermittelt, wobei sich z.B. eine Alkalisierung auf mindestens pH 9 ergab.Die Anwendung dieser Methode auf proteinhaltige Lebensmittel liefert ebenfalls — wenn auch nur in geringem Maße — Ammoniakabspaltungen, die wieder von der Art der Substanzen, der Alkalität der Lösung und der Destillationsdauer abhängig sind. Veränderungen im Verhältnis von Einwaagemenge zu Alkalisierungsmittel liefern daher über Alkalitätsverschiebungen auch jeweils etwas unterschiedliche Ammoniakausbeuten.Diese Vakuumdestillation im Makromaßstab ist bei Ammoniakbestimmungen in Substanzgemischen mit empfindlichen organischen Stickstoffverbindungen der Wasserdampfdestillation bei Normaldruck zwar überlegen, sie kann jedoch nicht als zuverlässige Methode empfohlen werden.

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Determination of ammonia in foodII. Examination of the vacuum distillation

In a vacuum apparatus with modified receiver the optimum conditions for a careful procedure for the quantitative liberation of small amounts of ammonia were tested. An alkalinity of at least pH 9 was necessary.Using this method with foods containing protein, ammonia was released too, though only in small amounts. These are depending not only on the type of substances, but also on the alkalinity of solution and the duration of distillation. Therefore, variations in the relationship between the amount of sample and the solution for alkalisation effect a change of alkalinity and thereby different yields of ammonia.For determinations of ammonia in mixtures of substances with instable nitrogen compounds the macrovacuum-apparatus is superior to the steam distillation applying normal pressure, but cannot be recommended as an reliable method.

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I. Mitteilung: diese Z. 244, 379 (1969).

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Auszug aus der Dissertation W. Sturm: Zur Bestimmung von Ammoniak in Getreidemehlen und Backwaren. Techn. Univ. Braunschweig 1967.     

On the spin relaxation of57Fe(III) species produced through EC-decay in diamagnetic57Co-labelled Co(III) compounds

Absorption Mössbauer spectra of high-spin⁵⁷Fe(acac)₃ incorporated in diamagnetic Co(acac)₃ and in paramagnetic Mn(acac)₃ and of the γ-ray irradiated (⁵⁷Fe, Co) (acac)₃ and (⁵⁷Fe, Mn) (acac)₃ were compared with emission spectra of⁵⁷Co-labelled Co(acac)₃. Magnetic hfs is found in the spectra of (⁵⁷Fe, Co) (acac)₃ at 78 to 195 K, whereas such hfs is observed neither for the spectrum of⁵⁷Co-labelled Co(acac)₃ nor for that of γ-ray irradiated (⁵⁷Fe, Co) (acac)₃). The absence of magnetic hfs in the spectrum of diamagnetic⁵⁷Co-labelled cobalt(III) compounds was ascribed to the spin-spin interaction due to the radicals produced in the vicinity of the decayed atom.     

Brominated flame retardants in laboratory air

During the development of a method for determination of brominated flame retardants in human plasma and serum using solid-phase extraction, several brominated flame retardants were found in the procedural blanks. The contaminants originated most probably from the laboratory air. The brominated flame retardants were found to be adsorbed on glass surfaces and to be acquired using solid-phase sampling. 2,4,6-Tribromophenol, 2,2',4,4'-tetrabromodiphenyl ether (BDE-47) and 2,2',4,4',5-pentabromodiphenyl ether (BDE-99) were the most abundant brominated flame retardants in our laboratory air, however, large differences in contamination with respect to sampling time and place were observed.     

Thermodynamique des melanges binaires LiPO3-Pb(PO3)2: Diagramme de phases et étude thermodynamique du liquide

Study of solid-liquid phase diagram of LiPO₃-Pb(PO₃)₂ binary system, in certain calcination conditions, shows the existence of several metastable phasis. When heated at a temperature of 723 K the binary mixtures lead uncompletely to a defined compound Pb₂Li(PO₃). On heating these ternary solid mixtures, three eutectic reactions have been observed: LiPO₃+Pb(PO₃)₂→Liquid at a temperature of 793 K(1) LiPO₃+Pb₂Li(PO₃)₅→Liquid at a temperature of 843 K (2) Pb₂Li(PO₃)₅+Pb(PO₃)₂→Liquid at a temperature of 891 K (3) The metastable liquid phase appears in the system at temperature of 793 K. DTA experiments performed on the binary LiPO₃-Pb(PO₃)₂ mixtures, show a superposition of two diagrams. The first one is metastable and the second represents the stable equilibrium phase diagram. Measurements of liquid enthalpy of binary LiPO₃-Pb(PO₃)₂ system at temperature of 979.65 K were reported. The corresponding values were very small and so the binary system can be considered as athermal. Assuming an ideal behaviour, the liquidus curves in the metastable diagram were calculated and the eutectic reaction (LiPO₃-Pb(PO₃)₂→Liquid) was confirmed at 793 K. This revised version was published online in August 2006 with corrections to the Cover Date.     

Immobilization of Mercuric reductase from aPseudomonas putida strain on different activated carriers

Mercuric reductase was isolated fromPseudomonas putida KT2442::mer-73 and immobilized on Chromatographic carriers activated by various methods. The immobilization methods for covalent coupling were compared with regard to preservation of enzymatic activity and coupling yields. Highest yields were obtained with carriers bearing the most reactive functional groups. Best results were achieved with tresyl chloride-activated carriers. The optimum binding conditions were found at pH 8. Application of the immobilized mercuric reductase for continuous treatment of Hg(II)-containing water was examined in a fixed bed reactor. Space-time yields up to 510 nmol/min-mL were attained. The kinetics of immobilized enzyme systems were not diffusion-controlled.     

Enumeration of total yeasts and molds in foods by the SimPlate Yeast and Mold-Color Indicator method and conventional culture methods: collaborative study

The relative effectiveness of the SimPlate Yeast and Mold-Color Indicator method (Y&M-CI) was compared to the U.S. Food and Drug Administration's (FDA) Bacteriological Analytical Manual (BAM) method and the proposed International Organization for Standardization (ISO) method, ISO/CD 21527, for enumerating yeasts and molds in foods. Test portions were prepared and incubated according to the conditions stated in both the BAM and ISO methods. Six food types were analyzed: frozen corn dogs, nut meats, frozen fruits, cake mix, cereal, and fresh cheese. Nut meats, frozen fruits, and fresh cheese were naturally contaminated. All other foods were artificially contaminated with either a yeast or mold. Seventeen laboratories throughout North America and Europe participated in the study. Three method comparisons were conducted. In general, there was <0.3 mean log count difference in recovery between the SimPlate method and the 2 corresponding reference methods. Moreover, mean log counts between the 2 reference methods were also very similar. The repeatability (Sr) and reproducibility (SR) standard deviations were comparable between the 3 method comparisons. These results indicate that the BAM method and the SimPlate method are equivalent for enumerating yeast and mold populations in foods. Similarly, the SimPlate method is comparable to the proposed ISO method when test portions are prepared and incubated as defined in the proposed ISO method.     

Reactivity of monolayer-protected gold nanoclusters at dye-sensitized liquid/liquid interfaces

Hexanethiolate monolayer-protected gold nanoclusters (MPCs) were used as redox quenchers at the polarizable water/1,2-dichloroethane (DCE) interface. Photocurrent responses originating from the heterogeneous quenching of photoexcited water soluble porphyrin complexes by MPCs dissolved in the DCE phase were observed. As MPCs can function as both electron acceptors and donors, the photocurrent results from the superposition of two simultaneous processes, which correspond to the oxidation and reduction of MPCs. The magnitude of the net photocurrent is essentially determined by the balance of the kinetics of these two processes, which can be controlled by tuning the Galvani potential difference between the two phases. We show that, within the available potential window, the apparent electron-transfer rate constants follow classical Butler-Volmer dependence on the applied potential difference.