Mercurimetrische Bestimmung von organisch gebundenem Chlor und Brom im Dezimilligrammbereich

Zusammenfassung Zur Bestimmung von Chlor und Brom in organischen Verbindungen im Dezimilligrammbereich werden Substanzmengen von 0,2 bis 2 mg im Sauerstoffstrom in einem mit Quarzkörnern gefüllten Verbrennungsrohr bei 1000° verbrannt und die Oxydationsprodukte in einem kleinen Perlenrohr mit Wasserstoffperoxydlösung absorbiert. Nach Ausspülen des Perlenrohres mit Isopropanol erfolgt die Endbestimmung durch Titration mit 0,01-n bzw. 0,1-n Quecksilberperchloratlösung.

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Summary To determine chlorine and bromine in organic compounds in the decimilligram range, samples weighing from 0.2 to 2 mg were burned at 1000° in a stream of oxygen in a combustion tube filled with quartz grains. The oxidation products were absorbed in a solution of hydrogen peroxide in a small bead tube. After the latter was rinsed out with isopropanol, the final determination was made by titration with 0.01 or 0.1N mercury perchlorate solution.

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Résumé Afin de doser le chlore et le brome dans les composés organiques, dans le domaine du décimilligramme, on a brûlé dans un courant d'oxygène à 1000° des quantités de substance de 0,2 à 2 mg, dans un tube à combustion rempli de grains de quartz et l'on a absorbé les produits d'oxydation dans l'eau oxygénée d'un petit tube à perles. Après lavage du tube à perles par l'isopropanol, on effectue le dosage final en titrant par une solution de perchlorate de mercure 0,01 ou 0,1N.

     

Lipophilic Diamides as Ionophores for Alkali and Alkaline Earth Metal Cations

A series of lipophilic N, N, N′,N′-tetrasubstituted diamides were prepared and their selectivity in solvent polymeric membranes was studied, cis-N, N, N′, N′-Tetraisobutylcyclohexane-1,2-dicarboxamide induces a selectivity in membranes for Li⁺over alkaline earth metal cations and other alkali metal cations by a factor of about 1000 and 100 respectively. The ionophore N, N′-diheptyl-N,N′-dimethylethylmalonamide is an attractive candidate for the use in microelectrodes for the determination of intracellular Mg²⁺-activities.     

An Improved Method for Site‐Specific End Modification of Zeolite L for the Formation of Zeolite L and Gold Nanoparticle Self‐Assembled Structures

The ability to site‐selectively modify micro‐ and nanosized particles has allowed for directed self‐assembly in two and three dimensions. Site‐selective modification of particles can be a complicated task requiring the pre‐organization of particles or enhanced particle fabrication methods. The aluminum silicate, zeolite L has been reported to undergo site‐specific modification at the zeolite channel entrances, post‐fabrication in a solution‐based method. The process by which the channel entrances are site selectively modified is explored here. The preliminary step of charging the zeolite channels with aqueous acid allows for catalysis of covalent bond formation at the channel entrances. Three new end‐specific modification reagents are described based on silanol and silyl ether functional groups. These reagents are purified by column chromatography and characterized by¹H NMR spectroscopy and high resolution mass spectrometry (HRMS); they provide for reliable end modification of zeolites L. Preferential reactivity at the channel entrances is also observed. The utility of the approach is demonstrated by modifying zeolite L with adamantane at the channel entrances. Site‐specific self‐assembly with β‐cyclodextrin coated gold nanoparticles can be triggered with a chemical stimulus. The resulting multivalent host‐guest interactions give gold clustered nanoparticles at the ends of the micrometer‐sized zeolites.     

Lipophilic Di- and Triamides as Ionophores for Alkaline Earth Metal Cations

Different electrically neutral lipophilic di- and triamides were prepared and their ion selectivity in membranes studied. In membranes the ionophore N, N′-diheptyl-N, N′-dimethyl-succinamide prefers Ca²⁺ over Mg²⁺ by a factor of 20 but rejects Na⁺ and K⁺ in respect to Mg²⁺ by a factor of 100 and 10, respectively. This selectivity suffices to perform useful intracellular Mg²⁺ activity studies.     

Quantitative organische Elementaranalyse im Dezimilligrammbereich. III

Zusammenfassung Es wird eine Methode zur Bestimmung des Schwefels und zur Bestimmung von Schwefel und Chlor (Brom) ineiner Einwaage beschrieben. Substanzmengen zwischen 0,1 und 1,5 mg werden im Sauerstoffstrom bei zirka 1000° in einem mit Quarzperlen gefüllten Verbrennungsrohr verbrannt und die Verbrennungsprodukte in einem mit Wasserstoffperoxydlösung benetzten Mikro-Perlenrohr absorbiert. Die Titration des entstandenen Sulfates erfolgt mit 0,02-n Bariumperchlorat und Thorin als Indikator. Im Anschluß kann vorhandenes Chlorid (Bromid) mercurimetrisch titriert werden.Die erzielte Genauigkeit entspricht den Anforderungen der Elementaranalyse.

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Summary A method is described for determining sulfur and also sulfur and chlorine (bromine) in a single sample. Amounts of the substance between 0.1 and 1.5 mg are burned in a stream of oxygen at around 1000° C in a combustion tube charged with quartz granules, and the combustion products are absorbed in a micro-bead tube moistened with a solution of hydrogen peroxide. The sulfate formed is titrated with 0.02N barium perchlorate with thorine as indicator. Any chloride (bromide) present can then be titrated mercurimetrically.The precision attained meets the demands of ultimate analysis.

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Résumé On décrit une méthode pour le dosage du soufre et pour le dosage du soufre et du chlore (ou du brome) surune seule prise d'essai. On réalise la combustion de quantités de substances comprises entre 0,1 et 0,5 mg dans un courant d'oxygène, à environ 1000°, dans un tube à combustion rempli de grains de quartz et l'absorption des produits de combustion s'effectue au moyen d'un micro-tube à perles mouillées par une solution d'eau oxygénée. On réalise le titrage du sulfate formé par le perchlorate de baryum 0,02N et le thorin comme indicateur. Pour finir, on peut titrer le chlorure (ou le bromure) présent, par mercurimétrie.L'exactitude obtenue correspond aux exigences de l'analyse élémentaire.

     

Lipophilic Synthetic Monoamides of Dicarboxylic Acids as Ionophores for Alkaline Earth Metal Cations

N, N-Dioctadecyl-substituted lipophilic monoamides of certain dicarboxylic acids have been prepared. It is shown that they induce a transport of alkaline earth metal cations through solvent polymeric membranes coupled to a counter transport of hydrogen ions or K⁺. They proved to be suitable components for ion-selective electrodes.     

Anwendung der Kolbenverbrennung auf die Mikrobestimmung des Phosphors in organischen Substanzen

Zusammenfassung Die Anwendung der Schöniger-Verbrennung auf die Mikrobestimmung des Phosphors in organischen Substanzen wurde untersucht. Es konnte festgestellt werden, daß beim Zurückbleiben von Aufschlußkohle auf dem Platinnetz immer Phosphorverluste auftreten, wobei wahrscheinlich Phosphorkohle unbekannter Konstitution gebildet wird. Dies ist für viele Substanzen bei Verbrennung in einem300-ml- Kolben der Fall. Bei Verwendung eines500- ml- Aufschlußkolbens und dem Zusatz von Ammoniumpersulfat zur Analysensubstanz wird für die meisten Substanzen ein quantitativer Aufschluß erzielt.

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Summary The use of the Schöniger combustion in the microdetermination of phosphorus in organic materials was studied. It was found that loss of phosphorus always accompanied the retention of decomposition carbon on the platinum gauze, probably due to the formation of phosphorus carbon of unknown composition. This occurs in the combustion of many materials in a 300-ml flask. If a 500-ml decomposition flask is used and if ammonium persulfate is added to the sample, a quantitative decomposition is achieved with most materials.

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Résumé On a étudié l'application de la méthode de combustion de Schöniger au microdosage du phosphore dans les substances organiques. On a pu établir que dans le résidu de l'attaque au charbon sur la toile de platine, il se produit toujours des pertes en phosphore, à cause de la formation probable de «carbure de phosphore» de constitution inconnue. C'est le cas pour de nombreuses substances si l'on fait la combustion dans une fiole de 300 ml. Par emploi d'une fiole d'attaque de 500 ml et par addition de persulfate d'ammonium à l'échantillon, on réalise une attaque quantitative pour la plupart des substances.

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Gewidmet zur 100. Wiederkehr des Geburtstages vonFriedrich Emich.     

Membrane Structure of Substance P. II. Secondary Structure of Substance P, [9-Leucine]substance P,and Shorter Segments in 2,2,2-Trifluoroethanol,Methanol, and on Liposomes Studied by Circular Dichroism

Comparative CD studies with substance P ( 1 ), [Leu⁹]substance P ([Leu⁹]- 1 ), and their shorter peptide segments supported the membrane structures predicted for substance P and [Leu⁹]substance P. They indicated that the C-terminal segments (from residue 3 or 4 onward) can adopt α-helical conformations in hydrophobic environments and on lipid membranes. The N-terminal segment, (residues 1–4) had a poly(proline)-like conformation in aqueous and hydrophobic surroundings. Residues 3 and 4 (Lys-Pro) appeared to belong to both domains and bring about the transition between the two. The estimated free energies of transfer for 1 and [Leu⁹]- 1 from their random conformations in H₂O to their partially helical conformations on an aqueous-hydrophobic interface are too small to allow detectable interaction with neutral lipid membranes at low concentrations. The two peptides should, however, interact detectably with anionic membranes because of favourable Boltzmann distribution factors. This prediction was shown to be correct for liposomes prepared from 1,2-dioleoyl-sn-glycero-3-phosphocholine (neutral) and phosphatidylserine (anionic).