A new approach to intermolecular forces in non-bonding regions

A new method to compute intermolecular energies in non-bonding regions is presented. It is based on the assumption that in such regions molecules can be reviewed as the sum of distorted, possibly overlapping, and electron exchanging atoms. The intermolecular energy change at a given distance is due to the sum of the atomic energy changes caused by these distortions. The energy change of any particular atom is computed in a Hartree—Fock model in which the effect of the other atom is represented by an effective potential. This potential in turn is computed from a calculation at a slightly larger intermolecular distance of the potential seen by an external electron in the field of the “other” atom. This potential computed in the RPA approximation and involves the distorted Hartree—Fock orbitals of the other atom (computed in a similar manner to the above) and the RPA response function of the other distorted atom.     

Projection between basis sets: A means of defining the electronic structure of functional subunits

The general problem of the transfer of the representation of a set of orthonormal functions from one basis to a different, nonequivalent one is considered and specialized to a matrix formulation convenient for use in molecular electronic structure calculations. A procedure is suggested for treating problems where the transfer of representation breaks into a subset of most interest and one of less interest as for example the occupied and virtual orbitals of a Hartree-Fock SCF calculation. These techniques are then applied to obtain a representation of a methyl group from an SCF wave function for methane.     

Zur Existenz von zwei Kristallmodifikationen der Mellitsäure

Zusammenfassung Es wurde röntgenorgraphisch und mit Hilfe derDTA, festgestellt, daß die Mellitsäure nur in einer Modifikation, der orthorhombischen¹, vorliegt. Die Darstellung der Mellitsäure^2,3 wurde in Einzelheiten modifiziert. Die Reinheit der Präparate wurde spektroskopisch, im IR- bzw. UV-Gebiet, und mit Hilfe der Papierchromatographie geprüft.

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by means of X-ray analysis and DTA it was found that mellitic acid exists only in the orthorhombic modification. The preparation of mellitic acid was modified in part. The purity ot the samples obtained was checked by IR-and UV-spectroscopy and by paper chromatography.

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Zur Kenntnis von Salzen einiger aromatischer Polycarbonsäuren, 3. Mitt.; 2. Mitt.:B. Hájek, E. Kálalová undF. Petr, Z. Chem.5, 230 (1965).

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Gewidmet dem Andenken an Professor Dr.Hans Meyer meinen Lehrer an der ehemaligen Deutschen Universität in Prag. Prof.Meyer geboren am 31. März 1871 in Wien, gestorben am 28. November 1942 in Theresienstadt, beschäftigte sich eingehend (mitH. Raudnitz u. a.) mit der Darstellung und Untersuchung der Mellitsäure und ihrer Derivate.     

Zur Automatisierung der Auswertung bei der quantitativen Spektralanalyse

Zusammenfassung Die Eigenschaften der photoelektrischen und photographischen Registrierung von Spektren werden besprochen und die Bedeutung der photographischen Registrierung für die Verfahrensentwicklung und Routineanalyse von Proben wechselnder Zusammensetzung hervorgehoben. Das Programmsystem für den elektronischen Digitalrechner und verschiedene Möglichkeiten der Datenerfassung werden beschrieben. Durch diese Automatisierung der Auswertung wird gegenüber dem herkömmlichen Rechenbrettverfahren eine Beschleunigung um den Faktor 200 erreicht.

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Summary The characteristics of the photoelectric and photographic registration of spectra are discussed and the importance of the photographic registration for the development of methods and the routine analysis of samples of changing composition is emphasized. The program system for the electronic digitalcomputer and different possibilities of data collecting are described. Automating the evaluation has resulted in a speeding-up factor of 200 compared with the traditional computing board method.

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Die obige Arbeit wurde erwähnt von Herrn Dr. Pohl am 6. 10. 1964 in Düsseldorf in seinem Vortrag Erfassen und Verwerten von chemischen Daten. [Diese Z. 209, 19 (1965).]

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Außerdem wurde uns die Arbeit von Tunnicliff und Weaver, Analytical Chemistry 36, 2318 (1964), erst nach Abschluß unserer Arbeit bekannt. Die Autoren befassen sich mit einer ähnlichen Aufgabe, wobei allerdings das Problem der Linienauswahl eingehender behandelt wird als bei uns.     

Determination of the quaternary compound ciclotropium in human biological material after hydrolysis and derivatization with the fluorophor flunoxaprofen chloride

The quantitative determination of the quaternary spasmolytic compound ciclotropium and its metabolite N-isopropyltropinium is described for human plasma and urine. The analytical procedure consists of ion-pair extraction from biological material, alkaline hydrolysis, subsequent derivatization with the fluorophor flunoxaprofen chloride and separation by high-performance liquid chromatography on a reversed-phase column with fluorimetric monitoring. The detection limits of 0.5 ng/ml in plasma and 10 ng/ml in urine at signal-to-noise ratios higher than 3 permit the determination of pharmacokinetic parameters after therapeutic doses.     

Immunochemical detection of aminoglycosides in milk and kidney

In 1996, the European Union established provisional maximum residue limits (MRL) for gentamicin, neomycin, streptomycin and dihydrostreptomycin in milk and tissue (0.1-5 mg kg-1). For the detection of these four aminoglycosides, three enzyme linked immunosorbent assays (ELISA) for applications in milk and kidney were developed. The screening of defatted and diluted milk resulted in limits of determination (LDM) of < 0.01 mg l-1. Kidney samples were deproteinized with a trichloroacetic acid solution (3%) and after filtration and the addition of buffer, aliquots were used in the ELISA. The LDM of the four aminoglycosides in kidney were < 0.05 mg kg-1. The ELISA were found suitable for the semi-quantitative screening of milk and kidney for the presence of the four aminoglycosides far below the MRL levels. In randomly taken milk samples (n = 776) and in kidneys derived from healthy pigs (n = 124), the aminoglycoside residues found were far below their established MRL. In eight out of the 94 kidney samples obtained from diseased animals after emergency slaughter, aminoglycoside residues were above the MRL.     

Oxidation of organic substances by compounds of trivalent manganese : XXV. Determination of benzene polyhydroxy and aminohydroxy derivatives with a standard solution of the fluoride complex of trivalent manganese

The redox potential of the Mn(III)/Mn(II) system in a medium of potassium fluoride and sulfuric acid was measured and its dependence on the concentration of both substances was found. Furthermore, the influence of the concentration of potassium fluoride and sulfuric acid on the visible absorption spectrum of trivalent manganese was studied.     

Sequence distribution and intramolecular excimer formation in styrene-acrylonitrile copolymers

Styrene-acrylonitrile copolymers, like many other copolymers containing styrene, exhibit both normal and excimer fluorescence. We have shown that the ratio of the excimer to monomer fluorescence intensities in random styrene-acrylonitrile copolymers is linearly dependent upon the concentration of styrene-styrene bonds in the copolymer. This observation is consistent with a photophysical model which allows the energy absorbed by styrene units to migrate freely along the copolymer chain. Some of the energy is emitted in the form of normal fluorescence; some of the energy, trapped by neighbouring styrene-styrene pairs suitably oriented to allow excimer formation, is emitted as excimer fluorescence. The fluorescence characteristics of acrylonitrile-styrene copolymers are contrasted with those of methyl methacrylate-styrene copolymers, in which the methylmethacrylate sequences are believed to present partial barriers to energy migration along the copolymer chains.     

Determination of phthalic acid, mono-(2-ethylhexyl) phthalate and di-(2-ethylhexyl) phthalate in human plasma and in blood products

Pretreatment for the determination of phthalic acid, mono-(2-ethylhexyl) phthalate (MEHP) and di-(2-ethylhexyl) phthalate (DEHP) in human serum or plasma, and the determination of these compounds in blood products by high-performance liquid chromatography was studied. The amount of phthalic acid, MEHP and DEHP, migrated into blood products from a flexible bag, was studied. About 0.1% of DEHP in a flexible bag was found to have migrated into human platelet plasma. Most of the MEHP and phthalic acid detected in human platelet plasma was not derived from the flexible bag but was produced by enzymatic hydrolysis of the migrated DEHP. The amount of DEHP eluted into blood products from the flexible bag differed, depending upon storage time, storage temperature, etc.     

Collisional depolarization of NO2 fluorescence as studied by Hanle effect measurements

We report on collisional depolarization of NO₂ fluorescence with use of Hanle effect (zero magnetic field level crossing) experiments. Single fine structure levels of NO₂ in several regions of the visible absorption spectrum predominantly near 593 nm and 514 nm are prepared by selective optical excitation and the depolarization of the fluorescence light versus a magnetic field is investigated. We find that the Hanle signal is in general a superposition of two Lorentzian shaped signals, each with a characteristic dependence on light intensity and NO₂ pressure. For NO₂ pressures >1 µ bar the collisional depolarization follows simple Stern-Volmer kinetics. However, an unusual pressure dependence is observed at NO₂ pressures <1 µ bar. In the same pressure range (<1 µ bar) we see also an unexpected resonance with significantly different properties as the Hanle signal.