Determination of zearalenone and ochratoxin A in soil

Mycotoxins are secondary metabolites, formed by the action of fungi on agricultural crops in the field or during storage. These metabolites are highly toxic to animals and humans and high levels have been measured in agricultural crops. In order to evaluate human risks due to ingestion of mycotoxin-contaminated food different methods have been developed for analysis of mycotoxins in cereals and maize. In this project the focus was on mycotoxins in agricultural soil and the fate of these toxins in the soil-water-plant system. Two different mycotoxins were selected in the study: zearalenone (ZON) produced by species of Fusariumor Aspergillusand ochratoxin A (OTA) produced by species of Penicillium. We developed a method for analysis of these toxins in soil. Soil samples were extracted with methanol-water (9:1) and purified by solid-phase extraction (SPE, C8-columns). The final extract was analysed using high-pressure liquid chromatography (HPLC) with fluorescence detection. A Phenyl Hexyl column was used to separate the toxins. The detection limits obtained were 0.1 and 1.0 microg kg(-1) dry weight (dw) for OTA and ZON, respectively. The developed method has been used for analysis of different soils in connection with growth chamber experiments. The soil types used in the growth chamber experiments were a sandy soil, a sandy clay soil, and a soil with high content of organic matter. The recovery was determined as 85.8 and 93.4% and the repeatability to 5.1 and 12.8% for OTA and ZON, respectively. The reproducibility obtained was 8.5 and 15.0% for soil samples, representing concentration levels from 0.2-30 microg kg(-1) dw (OTA) and from 1.0-100 microg kg(-1) dw (ZON).     

Excess partial molar enthalpies,entropies, Gibbs energies,and volumes in aqueous dimethylsulfoxide

The excess partial molar enthalpies, the vapor pressures, and the densities of dimethylsulfoxide (DMSO)–H₂O mixtures were measured and the excess partial molar Gibbs energies and the partial molar volumes were calculated for DMSO and for H₂O. The values of the excess partial molar Gibbs energies for both DMSO and H₂O are negative over the entire composition range. The results for the water-rich region indicated that the presence of DMSO enhances the hydrogen bond network of H₂O. Unlike monohydric alcohols, however, the solute-solute interaction is repulsive in terms of the Gibbs energy. This was a result of the fact that the repulsion among solutes in terms of enthalpy surpassed the attraction in terms of entropy. The data in the DMSO-rich region suggest that DMSO molecules form clusters which protect H₂O molecules from exposure to the nonpolar alkyl groups of DMSO.     

The crystal structure of Sc2Ru5B4

The crystal structure of Sc₂Ru₅B₄ has been determined by single-crystal X-ray analysis. Sc₂Ru₅B₄ crystallizes in the primitive monoclinic space group $\text{P2}\text{m}$ with a = 9.983(6), b = 8.486(4), c = 3.0001(3)Å, γ = 90.01(7)°, Z = 2. Deviations from the orthorhombic space group Pbam-D⁹_2h are small but significant. Intensity measurements were obtained from a four-circle diffractometer. The structure was solved by Patterson methods and refined by full matrix least-squares calculation. $\text{R =}\text{∑|ΔF|}\text{∑|F}{}_0\text{|}\text{= 0.036}$ for an asymmetric set of 863 independent reflections (|F₀|>2σ(F₀)). The crystal structure is characterized by two different types of boron atoms: (a) isolated borons B(1) and B(3) in distorted trigonal Ru-prisms with tetrakaidekahedral metal coordination: 6Ru + 3Sc, and (b) boron atoms B(2) and B(4) with a pronounced tendency to form boron pairs (B(2)-B(2) = 1.86 Å, B(4)-B(4) = 1.89 Å); the metal coordination of these boron atoms is 6Ru + 2Sc. Sc atoms have a coordination number of 17 consisting of 10Ru + 2Sc + 5B. The crystal structure of Sc₂Ru₅B₄ is a pentagon layer structure (Ru, B atoms) with a 4.3.4.3²-secondary layer of Sc atoms. The structure is furthermore related to the structure types of Ti₃Co₅B₂ and CeCo₃B₂. From powder photographs Sc₂Os₅B₄ is isotypic. No superconductivity was observed for Sc₂(Ru, Os)₅B₄ down to 1.5 K.     

Cloud point extraction of napropamide and thiabendazole from water and soil

The micellar extraction and enrichment of napropamide and thiabendazole using Genapol X 80 is described. Combined with their quantification by fluorescence, detection limits below 0.2 g/l with recovery rates of up to 95% were achieved. The recovery could be improved by lowering the extraction temperature and purificaton of the surfactants. This extraction method has been applied to the isolation and preconcentration of napropamide from standard soils. Experimental parameters affecting the recovery rates were examined.     

Neue K-Boride und verwandte Phasen (Re3B-Typ,aufgefüllt)

Zusammenfassung Mit Hilfe vonWeissenberg-Aufnahmen wird die Kristall-struktur der K(Kappa)-Hf–Mo–B-Phase verfeinert. Die Punktlage 2 a) in P6₃/mmc ist durch Mo-Atome (nicht Boratome) aufgefüllt. Damit entsteht praktisch Strukturgleichheit mit Co₂Al₅ bzw. Mn₃Al₁₀. Die analogen K-Boride Zr₉Mo₄B (mit Hf₉Mo₄B lückenlos mischbar) und Zr₉W₄B bestehen ebenfalls. In Hf₉Mo₄B werden bis 14 At% Al (1400°C) aufgenommen.In den Systemen Zr–Mo–{Fe, Co, Ni} und Hf–Mo(W)–{Fe, Co, Ni} werden weitere Vertreter mit obigem Strukturtyp (K-Phasen) aufgefunden; die Eisenmetall-Atome treten an Stelle von Bor.Phasen vom Typ Zr₃{Fe, Co, Ni} (N, O) _x entstehen beim Sintern in mäßigem Vakuum und gehören zur aufgefüllten Re₃B-Struktur.

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New K-Borides and related phases (filled up Re₃B-phases)

The crystal structure of the K(Kappa)-Hf–Mo–B-phase has been refined by means ofWeissenberg-photographs; the position 2 a) (P6₃/mmc) is occupied by Mo-atoms (not boron atoms). Thus structural identity with Co₂Al₅ and Mn₃Al₁₀ resp. is obvious. The isotypic K-borides Zr₉Mo₄B (it forms complete solid solutions with Hf₉Mo₄B) and Zr₉W₄B also exist. Hf₉Mo₄B dissolves aluminum up to 14 at% (1400°C).Further compounds with the abovementioned structure type (K-phases) have been detected within the systems Zr–Mo–{Fe, Co, Ni} and Hf–Mo(W)–{Fe, Co, Ni}; the iron metal atoms occupy the boron positions.Phases with composition Zr₃{Fe, Co, Ni} (N, O) _x , obtained by sintering, belong to the filled up Re₃B-type structure.

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Mit 3 Abbildungen

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Herrn Professor Dr.E. Ziegler zum 60. Geburtstag gewidmet.     

Komplexboride mit ReB2-Struktur

Ohne Zusammenfassung

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Complex borides with anReB ₂ structure

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Mit 1 Abbildung     

C-c bond formation through oxidatively induced elimination of platinum complexes--a novel approach towards conjugated macrocycles

A novel and effective method for the synthesis of conjugated macrocycles is described. By the self-assembly of conveniently accessible building blocks to a metalla-macrocycle, and subsequent C-C bond formation through elimination of transition metal units, the strained cyclodimeric terthiophene-diyne 4 -as a precursor for cyclo[8]thiophene 5- was synthesized in a good overall yield.     

Binuclear wirelike dimers based on ruthenium(II)-bipyridine units linked by ethynylene-oligothiophene-ethynylene bridges

The syntheses, structural characteristics, electrochemical behavior, ground-state spectra, photophysical properties, and transient absorption (TA) spectra in CH(3)CN solvent are reported for binuclear [(bpy)(2)Ru(bpy-E(T)(n)()E-bpy)Ru(bpy)(2)](4+) complexes, Ru(bpyT(n)bpy)Ru, where the Ru-based units are connected by alternating 3,4-dibutylthiophene (DBT')/thiophene (T') fragments linked via ethynyl groups (E) to bpy ligands at the 5-position (bpy is 2,2'-bipyridine). The ligand bpyT(3)bpy represents a module containing DBT'/T'/DBT' subunits, and bpyT(5)bpy accounts for a DBT'/T'/DBT'/T'/DBT' pattern. The syntheses and electrochemical and spectroscopic (emission and TA) properties in CH(2)Cl(2) solvent of the bpyT(n)()bpy ligands are likewise reported. The behavior of the Ru(bpyT(n)bpy)Ru dimers has been compared to that of the bpyT(n)bpy ligands and to that of a related mononuclear complex, [(bpy)(2)Ru(bpy-E-DBT')](2+), Ru(bpyDBT'). For the dimeric complexes, the electrochemical results show that the first reduction step takes place at the bpy ligand(s) bearing an ethynylene group, the first oxidation step is thiophene-centered, and further oxidation involves the metal centers, which are only weakly interacting. The photophysical and TA results for the Ru(bpyT(n)bpy)Ru dimers account for the presence of low-lying oligothiophene-centered (3)pi,pi levels, while higher-lying metal-ligand charge transfer ((3)MLCT) levels are thermally accessible only for the case of Ru(bpyT(3)bpy)Ru; the possible role of charge separation (CS) levels (from oxidation at the thiophene bridge and reduction at one of the coordinated bpy's) is also discussed.