ET-AAS determination of traces of As, Sb and Sn in pure gold after matrix separation with hydrazine

Summary The possibilities of ET-AAS using the graphite furnace or the tungsten coil atomizer were compared by the trace As, Sb and Sn determination in the chloride-containing solution resulting after gold reduction with hydrazine. It was found that the tungsten coil atomizer tolerates higher concentrations of chloride ions than the conventional graphite furnace.     

Beschreibung des inneren Spannungszustandes von Polyester-Faserstoffen durch Messung der Gleichgewichtsschrumpfkraft

Zusammenfassung Es wird eine modifizierte Schrumpfkraft-Meßmethode, die sog. Gleichgewichtsschrumpfkraft-Messung, vorgestellt, die sich besonders informativ und schnell zur vollständigen Beschreibung des inneren Spannungszustandes von Fasern und Garnen eignet. An zwei praktischen Beispielen aus dem Bereich der Struktur-Eigenschafts-Beziehungen von PES-Fasern werden einige mit dieser neuen Meßtechnik gewonnene Versuchsergebnisse diskutiert.Eine Automatisierung des Meßablaufes ist durchaus möglich, was z. Z. realisiert wird.

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Summary The properties of textiles from PET fibres are decisively depending on the stresses set within the material. According to the thermal stability of molecular interactions these stresses can be released by thermal treatments at different temperatures. As a consequence of stress release the material shrinks. Informations on the stresses built in can be achieved by following up the development of contraction force (shrinkage force) as a function of temperature when heating the fibres under constant length. By variation of heating rates retarded stress development and stress relaxation are observed. In this case the real set tensions due to prior treatments are not recorded.A new modified technique of measuring shrinkage forces provides in certain intervals of temperature an alteration of the clamped lengths by a minute stretching or shrinking of the fibres in a manner resulting a zero force deviation. So at each temperature we have an equilibrium of the released inherent stresses of the fibres and the recorded ones. These socalled equilibrium-shrinkage-force-curves are capable of describing the state of order of PET-fibres in a better way than other methods do. It will be shown that the formerly developed parameters of a heat treatment effective temperature and effective tension (8) can be derived from these curves as well as those tensions which had been set up in the fibres during cooling and processing or relaxed during storage.

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Herrn Prof. Dr.G. Rehage zum 60. Geburtstag gewidmet.

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Mit 9 Abbildungen     

Determination of traces of sulphur by electrothermal evaporation and non-thermal excitation of S-containing species in a hollow cathode discharge (FANES/MONES) and in a microwave induced plasma (MIP)

Summary The determination of sulphur by emission of S-atoms, S⁺ ions, S₂ and CS molecules using sulphate and other ions was investigated in such non-thermal excitation sources as the normal atmospheric argon-MIP and glow discharge in FANES/MONES (Furnace Nonthermal Excitation Spectrometry/Molecular Nonthermal Excitation Spectrometry). In both cases electrothermal evaporation (ETE) of the sample is applied. In the MIP technique (ETE-MIP) electrothermal evaporation from a new tungsten coil system is used and in the FANES samples are brought in the furnace. The thermal, electrical, chemical and pressure conditions were optimized and the emission spectra recorded. Detection limits are 90 ng for the ETE-MIP technique using the S 469.413 nm atom line. With the tungsten tube-FANES/MONES detection limits of 17 ng are obtained with S₂ molecular band at 383.73 nm. With FANES/MONES in a carbon tube and measurements on CS molecular bands a detection limit of 2 ng is obtained.Dedicated to Prof. Dr. G. Tölg on the occasion of his 60th birthday     

Signal summation for the improvement of the detection performance and indirect increase of the sample quantity in direct AAS of solids

Summary Time-resolved AAS signals of several, individually-weighed, solid samples were stored and later summed by the personal computer. This summation yields a signal covering all the individual samples, with a signal-to-noise ratio which is improved according to the law familiar from other replicate determination techniques. This makes it possible to determine concentrations in samples at levels where it would otherwise be necessary to resort, for instance, to a preliminary chemical concentration step. The technique has been applied to the determination of traces of Pb and Cd in malt and yeast.     

Structural characterization of chelator-terminated dendrimers and their synthetic intermediates by mass spectrometry

Herein, we report the structural analysis of a novel family of iron-chelating dendrimers and their synthetic intermediates utilizing matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) and electrospray ionization ion trap (ESI IT) MS. These dendrimers share a benzene tricarbonyl core moiety attached to three tripodal branching units, each linking to three terminal groups, ranging from carboxyl, catechol and 3-hydroxy-6-methyl-pyran-4-one moieties and their protected analogs. In order to monitor the progression of dendrimer synthesis, all intermediates and final products were mass analyzed by conventional MALDI-TOF MS with and without alkali metal spiking. For structural characterization, interpretable post-source decay (PSD) and electrospray ionization ion trap MS/MS spectra were obtained from proton, sodium and potassium adducts of the dendrimers. One major route of dendrimer fragmentation was at or adjacent to the amide bonds either of the terminal chelating groups or near the core moiety. Fragmentation in the latter case was primarily at the N-terminal side of the amide bond and was directed by the proximity of a tertiary carbon of the branching unit. Furthermore, it was found that terminal ester, ether and amide linkages to the protecting and chelating groups could be sequentially broken in a single MS/MS spectrum through multiple cleavages resulting in product ions of decreasing intensity. Moreover, such cleavages could also be induced in a stepwise manner in a multistage ion trap MS(n) experiment.     

Indirect nuclear spin-spin coupling constants in 1,2-diboretane-3-ylidene, a homoaromatic system with pi and sigma 3c/2e bonds. Comparison of experimental data with calculations using density functional theory (DFT)

The non-classical 1,2-diboretane-3-ylidene 1a was studied by 13C and 29Si NMR spectroscopy in order to obtain coupling constants 1J(13C,11B) and 1J(29Si,13C). The magnitudes of 1J(13C,11B) were deduced from linewidth measurements in low-temperature 13C and 11B NMR spectra. Calculation of the coupling constants for model compounds related to 1a, using DFT methods based on optimized geometries [B3LYP/6-311+G(d,p)], gave data in agreement with the experiments. Furthermore, the calculations predict for the first time a negative sign of 1J(13C,11B) which mirrors the bonding situation in 1 as described by theory.     

Die Acetalgruppe, 1. Mitt. Acetale von Halogenmethyl-arylcarbinolen

Several halomethyl-arylcarbinols were prepared, and the influence of substituents on enantiomer selectivity in the acetalisation reaction with [2S-(2,3a,4,7,7a)]-octahydro-7,8,8-trimethyl-4,7-methanobenzofuran-2-ol was examined.

Unserem sehr verehrten Lehrer, Herrn Prof. Dr.Otto Hromatka, mit den besten Wünschen zum 80. Geburtstag gewidmet.