Functional films of maleic anhydride copolymers under physiological conditions

Reactivity and swelling of nanometer films of alternating maleic anhydride copolymers were investigated in dependence on the kind of comonomer and molar mass of copolymer in aqueous solution at pH 7.4 and pH 3.0 in order to reveal their characteristics under physiological conditions. Fully hydrolyzed (maleic acid) chains of the copolymers with styrene, propene, and ethylene comonomers covalently bound to SiO2 substrates showed a "mushroom" swelling behavior at pH 7.4 with a layer thickness scaling of N3/5. Decreasing the environmental pH was found to induce a comonomer-dependent shrinking or collapse of the immobilized polymers due to the change in ionization. From the swelling kinetics of non-hydrolyzed chains, the time constants and characteristics of swelling and anhydride hydrolysis were determined and found to depend on the type of comonomer. The short- and long-term swelling kinetics [l approximately t and approximately ln(t)1/2] were found to be in agreement with theoretical models of polymer swelling, while at intermediate time scales enhanced swelling was observed due to hydrolysis reaction of maleic anhydride groups. The findings elucidate the variety of properties of maleic anhydride copolymer films under physiological conditions, which can advantageously be applied for biofunctionalization of different templates.     

Determination of urinary prostanoids by capillary gas chromatography/high-resolution mass spectrometry

A stable isotope-dilution gas-chromatography/high-resolution mass spectrometry method for the determination of prostaglandin E₂ (PGE₂) and 6-keto-prostaglandin F_1α (6-keto-PGF_1α) in urine as their methoxime/t-butyldimethylsilyl ether/t-butyl-dimethylsilyl ester derivatives is described. The derivatives are prepared by a novel derivatization scheme in which the pentafluorobenzyl esters are formed prior to the silylation step in which the t-butyldimethylsilyl esters are formed in an apparent exchange reaction. Recoveries through the entire extraction and derivatization procedure are 70.6% for PGE₂ and 64.4% for 6-keto-PGF_1α. Quantitation at mass resolutions approaching 10 000 eliminated all interferences in the PGE₂ chromatograms while lower resolutions were sufficient for 6-keto-PGF_1α. Limits of detection of 50 pg ml^?1 for each prostanoid were obtained. For PGE₂, a lower limit of detection was obtained at a mass resolution of 10 000 (50 pg ml^?1) than was obtained at a mass resolution of 1000 (80 pg ml^?1), illustrating the selectivity of detection.     

Quantitative Analyse von Alkylzinnverbindungen

Zusammenfassung Es wird ein Verfahren zur Analyse von OctylzinnVerbindungen und der darin als Verunreinigung vorkommenden niederen Alkylzinnverbindungen (hauptsächlich Butylzinnverbindungen) beschrieben. Die Trennung erfolgt dünnschicht-chromatographisch mit einem Fließmittel aus n-Butanol, Eisessig und Wasser, die Anfärbung mit Dithizon. Die Bestimmung erfolgt spektralphotometrisch ebenfalls mit Dithizon. Man kommt hierbei mit einer einzigen Eichkurve aus, da die Farbintensität der verschiedenen Alkylzinnverbindungen (mit Ausnahme der Monoalkylverbindungen) dem betreffenden Zinnanteil proportional ist. Der Gehalt an Monoalkylzinnverbindungen wird volumetrisch mit ÄDTA bestimmt. Alkylzinnthioglykolsäureester erfordern eine Vorbehandlung mit Jod.

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Quantitative analysis of alkyl-tin compounds

A method is described for the analysis of octyl-tin compounds and lower alkyl-tin compounds (mainly butyl-tin compounds) occurring therein as impurities. Separation is achieved by thin-layer chromatography employing n-butanol/glacial acetic acid/water as solvent and dithizone for detection. The determination is carried out by spectrophotometry using also dithizone. A single calibration curve is sufficient as the colour intensity of the different alkyl-tin compounds (except monoalkyl compounds) is proportional to the tin content. Monoalkyl-tin compounds are determined volumetrically with EDTA. Alkyl-tin thioglycolates require a pre-treatment with iodine.

     

Palladium- and copper-catalyzed 1,4-additions of organozinc compounds to conjugated aldehydes

Conjugated aldehydes undergo smooth Pd(OAc)2.PPh3- or Me2CuCNLi2-catalyzed 1,4-addition of dialkylzinc reagents. [reaction: see text].     

Structure-specific magnetic field inhomogeneities and its effect on the correlation time

We describe the relationship between the correlation time and microscopic spatial inhomogeneities in the static magnetic field. The theory takes into account diffusion of nuclear spins in the inhomogeneous field created by magnetized objects. A simple general expression for the correlation time is obtained. It is shown that the correlation time is dependent on a characteristic length, the diffusion coefficient of surrounding medium, the permeability of the surface and the volume fraction of the magnetized objects. For specific geometries (spheres and cylinders), exact analytical expressions for the correlation time are given. The theory can be applied to contrast agents (magnetically labeled cells), capillary network, BOLD effect and so forth.     

Nachweis und Bestimmung des Eisens, sowie seine Trennung von anderen Elementen

Ohne Zusammenfassung