Capillar-gas-chromatographische Bestimmung von Alkylphenolen in Harn

Zusammenfassung Es wird ein empfindliches und zuverlässiges Verfahren beschrieben, mit dem die 10 wichtigsten phenolischen Metabolite von Benzol, Toluol, den Xylolen und Ethylbenzol im Harn bestimmt werden. Der mit Schwefelsäure angesäuerte Harn wird einer Wasserdampfdestillation unterworfen. Das Destillat wird mit Dichlormethan extrahiert und im Stickstoffstrom eingeengt (Anreicherungsfaktor 10). Die gas-chromatographische Bestimmung erfolgt auf einer 30 m-Quarzcapillare (SE 54) mit FID-Detektion. Zur Kalibrierung werden wäßrige Standards in gleicher Weise aufbereitet. Als innerer Standard wird 3-Ethylphenol zu Beginn der Aufarbeitung zugesetzt. Für die Alkylphenole (Phenol, o- und p-Kresol; dl-1- und 2-Phenylethanol; 3-Methylbenzylalkohol; 2-Ethylphenol; 2,4-, 2,3- und 3,4-Dimethylphenol) wurde die Präzision in der Serie bei jeweils 2 Konzentrationen untersucht (n=10, ¯x=0,9–41,7 mg/l, s=2,3–16,8%). Die Wiederfindungsraten lagen zwischen 89 und 109%. Die Nachweisgrenze betrug 0,3 mg/ l. Die Linearität des Verfahrens wurde bis zu 50 mg/l überprüft.

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Determination of alkylphenols in urine by capillary gas chromatography

Summary A sensitive and reliable procedure is described for the determination of ten most important phenolic metabolites of benzene, toluene, xylenes and ethylbenzene. The urine is acidified with sulphuric acid and simultaneously steam-distilled. The distillate is extracted with dichloromethane. The organic phase is reduced in volume for tenfold enrichment. The gas-chromatographic determination is performed on a fused silica capillary (SE 54; 30 m) by FID. For calibration, aqueous standards are subjected to the same treatment as the urinary samples. 3-Ethylphenol is used for internal standardization. For ten alkylphenols (phenol; o- and p-cresol; dl-1- and 2-phenylethanol; 3-methylbenzyl alcohol; 2-ethylphenol; 2,4-, 2,3- and 3,4-dimethylphenol) within-series imprecision has been evaluated for two concentrations (n=10, ¯x=0.9–41.7 mg/l, s=2.3–16.8%). The recovery rates range between 89 and 109%. The detection limit is 0.3 mg/l. Linearity has been tested up to 50 mg/l.

     

Characterization of a Multicomponent Lithium Lithiate from a Combined X‐Ray Diffraction,NMR Spectroscopy,and Computational Approach

An unusual lithium lithiate [Li(diglyme)₂][(diglyme)Li₂(C₄H₃S)₃], made up from three carbanions, two lithium cations, and a single donor base molecule in the anion and a single lithium cation, coordinated by two donor base molecules, is investigated in a combined study including X‐ray diffraction, NMR spectroscopy and computational approaches in solution and the solid state. While the multicomponent lithiate is the only species present in the solid state, solution NMR spectroscopy and computational methods were employed to identify a second species in solution. The dimer [(diglyme)Li(C₄H₃S)]₂ coexists with the lithiate in solution in a 1:1 ratio, the more the higher the polarity of the solvent is. Only the combination of this multitude of methods provides a firm picture of the whole.     

Soluble molecular compounds with the Mg-O-Al structural motif: a model approach for the fixation of organometallics on a MgO surface

We report a facile route to the molecular compounds with the Mg-O-Al structural motif. The reaction of Mg[N(SiMe3)2]2 (1) with a stoichiometric amount of LAlOH(Me) (2) [L = CH{(CMe)(2,6-iPr2C6H3N)}2] in THF/n-hexane at 0 degrees C results in the formation of the heterobimetallic compound (Me3Si)2NMg(THF)2-O-Al(Me)L (3) in high yield. The similar reaction of 1 equiv of Mg[N(SiMe3)2]2 and 2 equiv of LAlOH(Me) results in the formation of trimetallic compound L(Me)Al-O-Mg(THF)2-O-Al(Me)L (4). Structural analyses of 3 and 4 have been carried out, revealing the presence of the Mg-O-Al motif. A tentative assignment of the Mg-O-Al vibrations has been made and was supported by calculations.     

Synthesis, characterization, and X-ray crystal structure of a gallium monohydroxide and a hetero-bimetallic gallium zirconium oxide

A monomeric hydroxide of gallium, LGa(Me)OH, containing terminal hydroxide and methyl groups was prepared by the hydrolysis of LGa(Me)Cl in the presence of N-heterocyclic carbene and water [L = HC{(CMe)(2,6-i-Pr2C6H3N)}2] in high yield and in a pure form. LGa(Me)OH was used as a synthon to assemble the first hetero-bimetallic compound with a Ga-O-Zr core, [(LGaMe)(Cp2ZrMe)](mu-O).     

Reversible activation of diblock copolymer monolayers at the interface by pH modulation, 1: Lateral chain density and conformation

This study focuses on the design of chemically regulated surfaces that allow for reversible control of the interactions between biological matter (cells and proteins) and planar substrates. As a tunable interlayer, we use a monolayer of a near-monodisperse poly[2-(dimethylamino)ethyl methacrylate-block-methyl methacrylate] (PDMAEMA-PMMA) diblock copolymer. Owing to the relatively large fraction (50%) of the hydrophobic PMMA block, this copolymer forms a stable Langmuir monolayer at the air/water interface. Both in situ and ex situ film balance experiments suggest that the hydrophilic PDMAEMA block adsorbs to the air/water interface in its uncharged state (pH 8.5), but stretches into the subphase in its charged state (pH 5.5). Optimization of the preparation protocols enables us to fabricate stable, homogeneous diblock copolymer films on hydrophobized substrates via Langmuir-Schaefer transfer at well-defined lateral chain densities. Ellipsometry and X-ray reflectivity studies of the transferred films confirm that the film thickness can be systematically regulated by the lateral chain densities. The transferred copolymer films remain stable in water for about a week, suggesting that they are promising materials for the creation of pH-controlled solid substrates for the support of biological matter such as proteins and cells.     

Shape and Structure Formation of Mixed Nonionic–Anionic Surfactant Micelles

Aqueous solutions of a nonionic surfactant (either Tween20 or BrijL23) and an anionic surfactant (sodium dodecyl sulfate, SDS) are investigated, using small-angle neutron scattering (SANS). SANS spectra are analysed by using a core-shell model to describe the form factor of self-assembled surfactant micelles; the intermicellar interactions are modelled by using a hard-sphere Percus–Yevick (HS-PY) or a rescaled mean spherical approximation (RMSA) structure factor. Choosing these specific nonionic surfactants allows for comparison of the effect of branched (Tween20) and linear (BrijL23) surfactant headgroups, both constituted of poly-ethylene oxide (PEO) groups. The nonionic–anionic surfactant mixtures are studied at various concentrations up to highly concentrated samples (ϕ ≲ 0.45) and various mixing ratios, from pure nonionic to pure anionic surfactant solutions. The scattering data reveal the formation of mixed micelles already at concentrations below the critical micelle concentration of SDS. At higher volume fractions, excluded volume effects dominate the intermicellar structuring, even for charged micelles. In consequence, at high volume fractions, the intermicellar structuring is the same for charged and uncharged micelles. At all mixing ratios, almost spherical mixed micelles form. This offers the opportunity to create a system of colloidal particles with a variable surface charge. This excludes only roughly equimolar mixing ratios (X≈ 0.4–0.6) at which the micelles significantly increase in size and ellipticity due to specific sulfate–EO interactions.     

Friedrich Theodor Althoffs Beziehungen zur Chemie

Friedrich Theodor Althoff who operated for more than 25 years as “Vortragender Rat” in “Preußisches Ministerium der Geistlichen, Unterrichts‐ und Medicinalangelegenheiten” (Kultusministerium), died 100 years ago. He effectively influenced matters concerning German universities and there connections with industry, as well as the relationship with international science. His sphere of responsibility consisted of highschools and universities but also care for preservation of libraries, memorials and development of medical science. He was also responsible for appointing personnel within universities and for furtherance and foundation of scientific institutions. He established new kinds of organisation as such as the annual Conference of the administration of german universities (later to become “Kultusministerkonferenzen”) and other provisions. With profounded understanding of human being and extensive communications he enabled the appointment of especially gifted scientists. Highly honoured and selfassured, but otherwise often criticised, he was named “der heimliche Kultusminister”.