Immunological determination of triazine pesticides bound to soil humic acids (bound residues)

An immunological method for the determination of triazine herbicides covalently bound to soil humic acids has been developed. A sandwich-immunoassay has been performed, based on both polyclonal humic acid-antibodies and monoclonal triazineantibodies. A peroxidase-labelled third antibody has been used for the photometric detection. A triazine-humic acid conjugate served as calibration standard. The coupling density for this conjugate has been determined by measuring the difference of free amino groups both with ninhydrin and with the trinitrobenzene sulfonic acid method. In addition, the coupling density has been confirmed by scintillation counting using a (14)C-atrazine derivative. Due to nonspecific interactions between antibody proteins and humic acids, different blocking steps had to be performed. Finally, the assay has been applied to a triazine contaminated soil sample. Humic acids (including bound residues) have been extracted by diluted sodium carbonate solution. Concentrations of bound atrazine residues have been found in the range of 2 mg/kg soil on fields where triazine herbicides has been applied over a period of 21 years. These results are comparable to both the applied amount and the nonextractable fraction.     

Model Compounds for Iron Proteins. Structures and Magnetic, Spectroscopic, and Redox Properties of Fe(III)M(II) and [Co(III)Fe(III)](2)O Complexes with (&mgr;-Carboxylato)bis(&mgr;-phenoxo)dimetalate and (&mgr;-Oxo)diiron(III) Cores

A series of heterobimetallic complexes of the type [Fe(III)M(II)L(&mgr;-OAc)(OAc)(H(2)O)](ClO(4)).nH(2)O (2-5) and [{Fe(III)Co(III)L(&mgr;-OAc)(OAc)}(2)(&mgr;-O)](ClO(4))(2).3H(2)O (6) where H(2)L is a tetraaminodiphenol macrocyclic ligand and M(II) = Zn(2), Ni(3), Co(4), and Mn(5) have been synthesized and characterized. The (1)H NMR spectrum of 6 exhibits all the resonances between 1 and 12 ppm. The IR and UV-vis spectra of 2-5 indicate that in all the cases the metal ions have similar coordination environments. A disordered crystal structure determined for 3 reveals the presence of a (&mgr;-acetate)bis(&mgr;-phenoxide)-Ni(II)Fe(III) core, in which the two metal ions have 6-fold coordination geometry and each have two amino nitrogens and two phenolate oxygens as the in-plane donors; aside from the axial bridging acetate, the sixth coordination site of nickel(II) is occupied by the unidentate acetate and that of iron(III) by a water molecule. The crystal structure determination of 6 shows that the two heterobinuclear Co(III)Fe(III) units are bound by an Fe-O-Fe linkage. 6 crystallizes in the orthorhombic space group Ibca with a = 17.577(4) ?, b = 27.282(7) ?, c = 28.647(6) ?, and Z = 8. The two iron(III) centers in 6 are strongly antiferromagnetically coupled, J = -100 cm(-1) (H = -2JS(1).S(2)), whereas the other two S(1) = S(2) = (5)/(2) systems, viz. [Fe(2)(III)(HL)(2)(&mgr;-OH)(2)](ClO(4))(2) (1) and the Fe(III)Mn(II) complex (5), exhibit weak antiferromagnetic exchange coupling with J = -4.5 cm(-1) (1) and -1.8 cm(-1) (5). The Fe(III)Ni(II) (3) and Fe(III)Co(II) (4) systems, however, exhibit weak ferromagnetic behavior with J = 1.7 cm(-1) (3) and 4.2 cm(-1) (4). The iron(III) center in 2-5 exhibits quasi-reversible redox behavior between -0.44 and -0.48 V vs Ag/AgCl associated with reduction to iron(II). The oxidation of cobalt(II) in 4 occurs quasi-reversibly at 0.74 V, while both nickel(II) and manganese(II) in 3 and 5 undergo irreversible oxidation at 0.85 V. The electrochemical reduction of 6 leads to the generation of 4.     

Ordered nanostructured ceramic–metal composites through multifunctional block copolymer-metal nanoparticle self-assembly

A novel strategy for fabrication of ordered ceramic–metal nanocomposites was demonstrated by multifunctional block copolymer/metal nanoparticle self-assembly. Hybrid organic–inorganic block copolymer poly(3-methacryloxypropyl-T8-heptaisobutyl-polyhedral oligomeric silsesquioxane-block-N,N-dimethylaminoethyl methacrylate) was synthesized and used as a bi-functional structure directing agent for ligand-stabilized platinum nanoparticles to form ordered organic–inorganic nanocomposites with dense loading of inorganic species in both microphase separated domains. Subsequently, thin films of the hybrid material were converted to ordered silica (ceramic)–platinum (metal) nanocomposites via UV-assisted ozonolysis. This is the first time ordered ceramic–metal nanocomposites were achieved through a bottom-up approach, opening up opportunities for the design and synthesis of a broad range of ordered inorganic–inorganic nanocomposites.     

The Oxalato-Titanium-Containing Tungstophosphate(V) Dimers, [Ti8(C2O4)8P2W18O76(H2O)4]18− and [Ti6(C2O4)4P4W32O124]20−

The oxalato-titanium(IV)-containing, dimeric 18-tungsto-2-phosphate [Ti₈(C₂O₄)₈P₂W₁₈O₇₆(H₂O)₄]^18? (1) and the 32-tungsto-4-phosphate [Ti₆(C₂O₄)₄P₄W₃₂O₁₂₄]^20? (2) are formed upon reaction of the oxalato-titanium complex [TiO(C₂O₄)₂]^2? with the trilacunary Keggin precursor [A-α-PW₉O₃₄]^9? and the hexalacunary Wells–Dawson precursor [H₂P₂W₁₂O₄₈]^12?, respectively. Polyanion 1 consists of two {PW₉} units encapsulating eight titanium centers and connected to each other via two Ti–O–Ti bridges, and crystallizes as a mixed potassium-sodium-lithium salt in the triclinic space group $P{\bar{1}}$ . Polyanion 2 comprises two {P₂W₁₆} units containing each two titanium atoms, and the two half-units are connected via two titanium atoms decorated by two oxalate groups each, and crystallizes as a mixed potassium-lithium salt in the rhombohedral space group $R{\bar{3}}c$ . Polyanions 1 and 2 were characterized in the solid state by single-crystal XRD, FT-IR, and TGA, whereas polyanion 2 was also investigated by ³¹P and ¹⁸³W NMR.     

Improved Synthesis,Structure, and Solution Characterization of the Cyclic 48-Tungsto-8-Arsenate(V), [H4As8W48O184]36−

We report on an improved synthesis and structural characterization of the cyclic 48-tungsto–8-arsenate(V) [H₄As₈W₄₈O₁₈₄]^36? (1). The mixed lithium–potassium salt of this polyanion, K_26.5Li_9.5[H₄As₈W₄₈O₁₈₄]·90H₂O (KLi-1), has been studied in the solid state by IR, single-crystal X-ray diffraction, and elemental analysis, and in solution by ¹⁸³W NMR spectroscopy.     

Imaging of the formerly bonded area of individual fibre to fibre joints with SEM and AFM

Besides the determination of the force and the energy needed to break individual fibre to fibre joints, the investigation of the formerly bonded area (FBA) is of essential importance to learn more about the failure mechanisms of fibre–fibre bonds in general. In this study the surfaces of paper fibres and the FBA of fibre–fibre joints after the determination of the breaking force as well as the bonding energy were analysed by means of low voltage scanning electron microscopy and atomic force microscopy. A comparison between the contact zone of fibres broken at different loading rates as well as under cyclic loading showed that there seems to be no significant difference in the appearance of the FBA in these cases. Only minor delamination of the cell wall could be found in the bonding zone, which indicates no mechanical interlocking of fibrils in the bonding zone. Furthermore, it is shown that some glues used for specimen preparation of fibre–fibre bond strength measurement are forming a glue film on the fiber surface and migrate into the bonding region.     

Zwei Tetrachlorothiotantalate: [Na‐15‐Krone‐5][TaSCl4 · Dioxan] und [Na‐15‐Krone‐5]2[(TaSCl4)2Dioxan] · S8

Two Tetrachlorothiotantalates: [Na‐15‐crown‐5][TaSCl₄ · dioxane] and [Na‐15‐crown‐5]₂[(TaSCl₄)₂dioxane] · S₈ During the reaction of Na₂S₄, TaCl₅ and 15‐crown‐5 in dichloromethane the crown ether partly suffers degradation to 1,4‐dioxane. Aside from sulfur, [Na‐15‐crown‐5][TaSCl₄ · dioxane] was the first product obtained. It crystallizes in the monoclinic space group P2₁/n with a = 1066.1, b = 1781.3, c = 1258.3 pm, β = 97.14°, Z = 4. In the [TaSCl₄ · dioxane]^– ion a dioxane molecule is loosely bonded to a square‐pyramidal TaSCl₄^– unit; two chlorine atoms are in contact with an Na⁺ ion. Upon standing with the mother liquor [Na‐15‐crown‐5]₂[(TaSCl₄)₂dioxane] · S₈ was formed. It crystallizes in the monoclinic space group C2/m; a = 1768.5, b = 1084.0, c = 1517.3 pm, β = 118.46°, Z = 4. In this case a dioxane molecule is coordinated with two TaSCl₄^– units. The [(TaSCl₄)₂ · dioxane]^2– ions and S₈ molecules alternate in the stacking direction b.     

Chloroselenate mit zwei- und vierwertigem Selen: 77Se-NMR-Spektren,Synthese und Kristallstrukturen von (PPh4)2SeCl6 · 2 CH2Cl2, (NMe3Ph)2SeCl6, (K-18-Krone-6)2SeCl6 · 2 CH3CN,PPh4Se2Cl9, (NEt4)2Se2Cl10, (PPh4)2Se3Cl8 · CH2Cl2 und (PPh4)2Se4Cl12 · CH2Cl2

Chloroselenates with Di- and Tetravalent Selenium: ⁷⁷Se-NMR-Spectra, Syntheses, and Crystal Structures of (PPh₄)₂SeCl₆ · 2 CH₂Cl₂, (NMe₃Ph)₂SeCl₆, (K-18-crown-6)₂SeCl₆ · 2 CH₃CN, PPh₄Se₂Cl₉, (NEt₄)₂Se₂Cl₁₀, (PPh₄)₂Se₃Cl₈ · CH₂Cl₂, and (PPh₄)₂Se₄Cl₁₂ · CH₂Cl₂ The title compounds were obtained from reactions of selenium and selenium tetrachloride with PPh₄Cl, NEt₄Cl, NMe₃PhCl, or (K-18-crown-6)Cl in dichloromethane or acetonitrile. (PPh₄)₂Se₃Cl₈ · CH₂Cl₂ was also formed from GeSe, PPh₄Cl and chlorine in acetonitrile. The ⁷⁷Se-NMR spectra of the solutions show the presence of dynamical equilibria which, depending on composition, mainly contain SeCl₂, SeCl₄, Se₂Cl₂, SeCl₆^2–, Se₂Cl₆^2–, and/or Se₂Cl₁₀^2–. Solutions of AsCl₃ and (PPh₄)₂Se₄ in acetonitrile upon chlorination with Cl₂ or PPh₄AsCl₆ yielded (PPh₄)₂Se₂Cl₆, while (PPh₄)₂As₂Se₄Cl₁₂ was the product after chlorination with SOCl₂. According to the X-ray crystal structure analyses the ions SeCl₆^2–, Se₂Cl₉^–, and Se₂Cl₁₀^2– have the known structures with octahedral coordination of the Se atoms. The structure of the Se₃Cl₈^2– ion corresponds to that of Se₃Br₈^2– consisting of three SeCl₂ molecules associated via two Cl^– ions. (PPh₄)₂Se₄Cl₁₂ · CH₂Cl₂ is isotypic with the corresponding bromoselenate and contains anions in which three SeCl₂ molecules are attached to a SeCl₆^2– ion; there is a peculiar Se–Se interaction.