Anomalous temperature dependence of the magnetic hyperfine field of99Ru in gadolinium

The magnetic hyperfine field at dilute⁹⁹Ru impurities in ferromagnetic Gd has been investigated as a function of temperature by time differential perturbed angular correlation (TDPAC) measurements. The saturation field at 11 K is H_hf(Ru Gd)=51(2) KOe. This value fits well into the systematics of 4d impurity hyperfine fields in Gd. The magnetic hyperfine field of RuGd does not follow the magnetization of the host (T_c=290 K) but vanishes abruptly at about 70 K. A similar behaviour has previously been observed for the 5d impurity Os in Gd. From first TDPAC measurements of the hyperfine interactions in the intermetallic phases of the Ru-Sc system it can not be completely ruled out that the observed collapse of the hyperfine field at 70 K is due to the formation of the intermetallic compound RuGd₃.This work has been supported by the Minister für Wissenschaft und Forschung des Landes Nordrhein-Westfalen     

Rapid detection and identification of <Emphasis Type="Italic">N</Emphasis>-acetyl-<Emphasis Type="Italic">L</Emphasis>-cysteine thioethers using constant neutral loss and theoretical multiple reaction monitoring combined with enhanced product-ion scans on a linear ion trap mass spectrometer

A sensitive and specific liquid chromatography-mass spectrometry (LC-MS) method based on the combination of constant neutral loss scans (CNL) with product ion scans was developed on a linear ion trap. The method is applicable for the detection and identification of analytes with identical chemical substructures (such as conjugates of xenobiotics formed in biological systems) which give common CNLs. A specific CNL was observed for thioethers of N-acetyl-L-cysteine (mercapturic acids, MA) by LC-MS/MS. MS and HPLC parameters were optimized with 16 MAs available as reference compounds. All of these provided a CNL of 129 Da in the negative-ion mode. To assess sensitivity, a multiple reaction monitoring (MRM) mode with 251 theoretical transitions using the CNL of 129 Da combined with a product ion scan (IDA thMRM) was compared with CNL combined with a product ion scan (IDA CNL). An information-dependent acquisition (IDA) uses a survey scan such as MRM (multiple reaction monitoring) to generate "informations" and starting a second acquisition experiment such as a product ion scan using these "informations." Th-MRM means calculated transitions and not transitions generated from an available standard in the tuning mode. The product ion spectra provide additional information on the chemical structure of the unknown analytes. All MA standards were spiked in low concentrations to rat urines and were detected with both methods with LODs ranging from 60 pmol/mL to 1.63 nmol/mL with IDA thMRM. The expected product ion spectra were observed in urine. Application of this screening method to biological samples indicated the presence of a number of MAs in urine of unexposed rats, and resulted in the identification of 1,4-dihydroxynonene mercapturic acid as one of these MAs by negative and positive product ion spectra. These results show that the developed methods have a high potential to serve as both a prescreen to detect unknown MAs and to identify these analytes in complex matrix.     

Karl Fischer-Reagentien ohne Pyridin

Zusammenfassung Karl Fischer-Reagentien, die SO₂ und Amin im üblichen Molverhältnis 12 enthalten, können nur mit Pyridin hergestellt werden. Stark basische Amine bewirken eine rasche Zersetzung der Reagenslösung und einen instabilen Endpunkt. Erhöht man den SO₂-Anteil soweit, daß das Molverhältnis SO₂Amin mindestens 11 ist, geben auch stark basische Amine hervorragende KF-Reagentien. Sie zeichnen sich durch stabile Endpunkte und hohe Reaktionsgeschwindigkeit aus. Besonders vorteilhaft ist die Anwendung als Zweikomponentenreagens, da beide Komponenten absolut lagerstabil und titerkonstant sind.

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Karl Fischer Reagents without pyridine

Summary Karl Fischer-Reagents containing SO₂ and amine in the normally applied molar ratio of 12 can be prepared only by using pyridine. Strong basic amines lead to a rapid decomposition of the reagent solution and to an instable endpoint. By raising the SO₂-content to a molar ratio SO₂amine of 11, even strong basic amines can be applied yielding KF-reagents of superior quality. They are characterized by stable endpoints and a high speed of reaction. Application as a two-solution reagent gives an additional advantage, because the single components are absolutely stable for storage and the titre remains constant.

     

Coulomb and nuclear excitation in the sequential break-up of6Li

The dissociation of⁶Li in the field of²⁰⁸Pb has been measured above the Coulomb barrier along with the elastic scattering. The inelastic angular distributions showing typical Coulomb nuclear interference structure can be very well reproduced by refined optical model calculations.     

Abrasive stripping voltammetry — the electrochemical spectroscopy for solid state: application for mineral analysis

Summary Abrasive stripping voltammetry possesses several features of a spectroscopy. It allows the qualitative and quantitative analysis of electroactive solid materials. This work is focussed on the application for the unambiguous identification of minerals (sulphides, sulfo-salt minerals, fahlores). g-amounts of a mineral are sufficient to perform a series of measurements. Three different voltammetric modes were used to study the electrochemical behaviour of the minerals.

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Abrasive Stripping Voltammetry — eine elektrochemische Spektroskopie für Festkörper: Anwendung auf Mineralidentifizierungen

     

Kernspektroskopische Untersuchungen am Zerfall des115m Cd

The energy levels in¹¹⁵In at 934, 1133, 1291, and 1419 keV weakly populated by β^?-decay from^115m Cd have been studied by angular correlation measurements using NaJ(Tl)-detectors. The previously measured angular correlations of the (485–934) keV cascade—which is practically isotropic—and the (158–1133) keV cascade were remeasured with higher accuracy. A 286 keV transition between the 1419 and the 1133 keV energy levels was observed and the highly anisotropic angular correlation of the (286–1133) keV cascade was also measured.     

Neue Synthesemethoden 2 Milde Einphasenoxidation von Aldehyden zu Carbonsäuren Kurze Mitteilung

The mild oxidation of aldehydes to carboxylic acids with benzyltriethylammoniumpermanganate in organic solvents at roomtemperature is presented.

     

Wasserbestimmung in Phenolen durch Karl-Fischer-Titration

Summary Karl Fischer titration can be applied to many phenols without any interference, though some are oxidized during titration. One-component reagents are to be preferred because they are less sensitive to interferences. Only pyrogallol and aminophenols are oxidized in this case. With two-component reagents dihydroxybenzenes and naphthols are oxidized, too. With coulometric titration interferences are more frequent. The oxidation rate depends on the pH and can be suppressed or minimised by adding salicylic acid to the Karl Fischer reagent.     

HX · MX3 molecules: heterodimer vapour ph ase complexes (M = B, Al; X = F, Cl) with halogen bridges An ab initio molecular orbital study

The equilibrium structures of HX · MX₃ vapour phase complexes are examined at the Hartree-Fock level using the DZP basis set. The complexes are found to be weak electron pair donor-acceptor adducts with long and weak intermolecular halogen bridges and with the hydrogens interacting with one of the halogen atoms of MX₃ in a cyclic arrangement. The energies of complex formation are calculated with and without correction for the basis set superposition error.