Feasibility study for the preparation of certified reference materials part I – mineral oil contaminated soils

The international joint project HYCREF (Contract No. G6RD-CT-2002-00854), funded by the European Commission in the 5th Framework programme, aimed to develop methods to prepare homogeneous and stable reference materials of water, soil, and waste contaminated with mineral oil hydrocarbons and to certify the mineral oil content by gas chromatographic methods. The results of a feasibility study for the preparation of three soil reference materials are discussed in this paper, and for the preparation of three waste reference materials in the second part (Koch et al., Accred Qual Assur submitted for publication). The soil materials were selected to represent different soil types and contamination levels. The project plan set three requirements for these reference materials: uncertainty in the mineral oil content resulting from the certification exercise <5%, a sample inhomogeneity of <3% and a minimum long-term stability of 5 years. For the most part, these requirements were met within this project.     

REALISIS: a medicinal chemistry-oriented reagent selection, library design, and profiling platform

REALISIS is a software system for reagent selection, library design, and profiling, developed to fit the workflow of bench chemists and medicinal chemists. Designed to be portable, the software offers a comprehensive graphical user interface and rapid, integrated functionalities required for reagent retrieval and filtering, product enumeration, and library profiling. REALISIS is component-based, consisting of four main modules: reagent searching; reagent filtering; library enumeration; and library profiling. Each module allows the chemist to access specific functionalities and diverse filtering and profiling mechanisms. By implementing the entire process of reagent selection, library design, and profiling and by integrating all the necessary functionalities for this process, REALISIS cuts the time required to design combinatorial and noncombinatorial libraries from several days to a few hours.     

On the limiting law solution of the cylindrical Poisson-Boltzmann equation for polyelectrolytes

Upper and lower bounds are given for the behaviour of the Poisson-Boltzmann potential of a highly charged, cylindrical polyelectrolyte in excess salt solution as the salt correntration or cylinder radius tends to zero. The exact singular behaviour of the potential very close to the cylinder is given in terms of a delta function.     

Spherical molecularly imprinted polymer particles: a promising tool for molecular recognition in capillary electrokinetic separations

Spherical molecularly imprinted polymer particles obtained via precipitation polymerization, were introduced as a pseudostationary phase in capillary electrophoresis (CE) to study molecular recognition. Analyses were performed via a partial filling technique using (+)-ephedrine-imprinted microspheres (100-200 nm) which were polymerized from methacrylic acid and 1,1,1-Tris(hydroxymethyl)propanetrimethacrylate using acetonitrile as the solvent. The influence of pH and the modifier content on the separation was investigated. A 0.1% w/v suspension in an aqueous 10 mM phosphate buffer (pH 2.5 with 40% acetonitrile) was hydrodynamically injected into the CE system (80% of the effective capillary length) and led to full baseline separation of racemic ephedrine within 10 min.     

Low-valent cobalt complexes with three different pi acceptor ligands: experimental and DFT studies of the reduced and the low-lying excited states of (R-DAB)Co(NO)(CO), R-DAB = substituted 1,4-diaza-1,4-butadiene

The complexes (RN=CH-CH=NR)Co(NO)(CO) with R = isopropyl, 2,6-diisopropylphenyl, or p-tolyl are chemically and electrochemically reducible to radical anions at potentials which strongly depend on R. The DFT calculated structure for the neutral compound with R = iPr agrees with the experiment, and the computed structure of the anion radical reveals changes according to a reduction of the R-DAB ligand. EPR results confirm an (R-DAB)-based singly occupied molecular orbital in [(RNCHCHNR)Co(NO)(CO)](.-), with minor but detectable contributions from NO as supported by IR spectroelectrochemistry and as quantified by DFT spin density calculations. The calculations indicate increasingly stabilized CO, NO, and RNCHCHNR pi* acceptor orbitals, in that order. On the basis of TD-DFT (time-dependent density functional theory) calculations, the lowest-lying excited states are assigned to metal-to-(R-DAB) charge transfer transitions while bands due to the metal-to-nitrosyl charge transfer occur at higher energies but still in the visible region. Resonance Raman studies were used to probe these assignments.     

Molecular assembly in synthesised hydrotalcites of formula Cu(x)Zn(6 - x)Al2(OH)16(CO3) x 4H2O--a vibrational spectroscopic study

Infrared and Raman spectroscopy have been used to characterise synthetic hydrotalcites of formula Cu(x)Zn(6 - x)Al2(OH)16(CO3) x 4H2O. The spectra have been used to assess the molecular assembly of the cations in the hydrotalcite structure. The spectra may be conveniently subdivided into spectral features based (a) upon the carbonate anion (b) the hydroxyl units (c) water units. The Raman spectra of the hydroxyl-stretching region enable bands to be assigned to the CuOH, ZnOH and AlOH units. It is proposed that in the hydrotalcites with minimal cationic replacement that the cations are arranged in a regular array. For the Cu(x)Zn(6 - x)Al2(OH)16(CO3) x 4H2O hydrotalcites, spectroscopic evidence suggests that 'islands' of cations are formed in the structure. In a similar fashion, the bands assigned to the interlayer water suggest that the water molecules are also in a regular well-structured arrangement. Bands are assigned to the hydroxyl stretching vibrations of water. Three types of water are identified (a) water hydrogen bonded to the interlayer carbonate ion (b) water hydrogen bonded to the hydrotalcite hydroxyl surface and (c) interlamellar water. It is proposed that the water is highly structured in the hydrotalcite as it is hydrogen bonded to both the carbonate anion and the hydroxyl surface.     

Kiesels?urebestimmung durch Destillation von H2SiF6 in einer Silberapparatur

Znsammenfassung Die Arbeit behandelt die Abtrennung der Kieselsäure von TiO₂, Al₂O₃, V₂O₅ und ZrO₂ durch Verflüchtigung von H₂SiF₆ in einer Silberapparatur. Die anschließende photometrische SiO₂-Bestimmung erfolgt nach der Silicomolybdänblaumethode. Es ergibt sich außerdem die Möglichkeit, Kieselsäure von Metallsalzen und von weiteren Oxyden zu trennen, die Fluß- und Schwefelsäure nicht in stärkerem Maße binden.II. Teil der Dissertation von Th. Keil, Gießen 1958. — I. Teil: diese Z. 165, 188, (1959).Wir danken der Titangesellschaft m.b.H., Leverkusen, für das Überlassen der Silberapparatur und überhaupt für das große Interesse, das sie dieser Arbeit entgegengebracht hat.     

Size effect on surface tension of small droplets

We discuss the influence of the effect of droplet size on the surface tension γ and develop a self-consistent method to derive a relation between γ and the droplet radius r. Referring our expression for γ(r) to the surface of tension we recover Tolman's result.     

Synthesis of 3-nitro- and 3-aminoquinoline-2,4-diones. An unexpected route to 3-hydroxyquinoline-2,4-diones

Nitration of 3-substituted-4-hydroxy-2(1H)-quinolones 1 with nitric acid leads either to 3-nitro- 2 or 3-hydroxyquinolinediones 3 , depending on the reaction conditions. 3-Substituted-3-hydroxyquinolinediones 3 are also obtained by oxidative hydroxylation with peracetic acid. Amination of 3-substituted-3-chloroquinolinediones 4 with ammonium hydroxide predominantly leads again to 3-substituted-3-hydroxyquinolinediones 3 , only in one case the 3-aminoquinolinedione 5 could be isolated. With morpholine or pyridine as amines the expected 3-aminoquinolinediones 6 and 7 were obtained.