Preliminary study of the thermally stimulated blue luminescence of ulexite

In this paper, novel results on the blue thermally stimulated luminescence (TSL) emission of ulexite (NaCaB₅O₆(OH)₆·5H₂O) have been studied. The four maxima appearing at 60, 110, 200 and 240°C on the TSL glow curves of this borate could be respectively associated to: (i) the first dehydration (NaCaB₅O₆(OH)₆·5H₂O→NaCaB₅O₆(OH)₆·3H₂O), (ii) the creation-annihilation of the three-hydrated phase, (iii) the Na-coordinated chains dehydroxylation and the starting point of the alkali self-diffusion through the lattice and (iv) the amorphisation of the lattice. These results are fairly well correlated with the differential thermal analyses (DTA), in situ thermal observations under environmental scanning electron microscope (TESEM) and thermal X-ray diffraction (TXRD) techniques.     

First measurement of the ϱ spectral function in nuclear collisions

The NA60 experiment at the CERN SPS has studied low-mass muon pairs in 158 A GeV In–In collisions. A strong excess of pairs is observed above the yield expected from neutral meson decays. The unprecedented sample size close to 400000 events and the good mass resolution of about 2% made it possible to isolate the excess by subtraction of the decay sources. The shape of the resulting mass spectrum shows some non-trivial centrality dependence, but is largely consistent with a dominant contribution from π⁺π^-→ϱ→μ⁺μ^- annihilation. The associated ϱ spectral function exhibits considerable broadening, but essentially no shift in mass. The p_T-differential mass spectra show the excess to be much stronger at low p_T than at high p_T. The results are compared to theoretical model predictions; they tend to rule out models linking hadron masses directly to the chiral condensate. PACS 25.75.-q; 12.38.Mh; 13.85.Qk     

Hochselektive differentialpulspolarographische Spurenbestimmung von Uran (katalytische Nitratreduktion) nach Extraktionsabtrennung

Zusammenfassung Die polarographische Spurenbestimmung von Uran durch katalytische Reduktion des NO ₃ ^– ist eine sehr empfindliche Analysenmethode. Sie kann aber nur unter Ausschluß einer Reihe von störenden Kationen und Anionen durchgeführt werden und erfordert eine genau zusammengesetzte Grundlösung. Darum wurde für das Uran eine einfache und rasche Extraktionsabtrennungsmethode mit Triphenylarsinoxid in CHCl₃ ausgearbeitet. Die Rückextraktion aus der organischen Phase mit 0,02 N Na₂CO₃ und anschließendes definiertes Ansäuern mit HNO₃ ermöglichen die Überführung des Urans in eine für die differentialpulspolarographische Bestimmung geeignete, reproduzierbare Grundlösung. Über 60 untersuchte Kationen und 20 Anionen stören die Bestimmung in weiten Grenzen nicht, was eine vielseitige Anwendung erlaubt. Die Nachweisgrenze liegt bei 1 ppb Uran in wäßriger Lösung. Die relative Standardabweichung beträgt für 100 ppb Uran ±2%.

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Highly selective trace determination of uranium by differential pulse polarography (catalytic nitrate reduction), following extraction separation

Summary The trace determination of uranium by differential pulse polarography, using the catalytic reduction of nitrate is known to be very sensitive, if certain interfering ions are excluded and if the composition of the base solution remains constant. In order to fulfil these conditions a simple and selective method for extracting uranium with triphenylarsine oxide in chloroform was developed. Back extraction with 0,02 N Na₂CO₃ and addition of HNO₃ lead to an appropriate base solution for the determination of uranium by differential pulse polarography. The influence of 60 cations and 20 anions was found to be negligible in a wide range. The limit of detection is about 1 ppb U and the standard deviation with 100 ppb U is ±2%.

Für die Überprüfung des Manuskripts möchte ich den Herren Dr. P. Baertschi und O. Antonsen herzlich danken.     

Hyphenation of capillary high-performance liquid chromatography with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry for nano-scale screening of single-bead combinatorial libraries

This paper focuses on the technical aspects of chemical screening from 384-well plate nano-scale single-bead combinatorial libraries. The analytical technique utilized is a combination of capillary liquid chromatography with ultraviolet detection and matrix-assisted laser desorption/ionization (MALDI) mass spectrometry. The HPLC/MALDI-MS hyphenation is achieved by means of a micro-fraction collector with a peak detection system that automatically collects the peaks onto the MALDI targets for subsequent characterization. Several experimental parameters such as type of 384-well plate, well-plate sealing foils, and a column-switching procedure were investigated using a small test library of nine components. Additionally, the influence of different MALDI matrices, different MALDI targets and sample-spotting techniques on the MALDI detection sensitivity as well as the ruggedness and sample throughput capacity of this technique were studied. Optimum results for the analytes investigated were obtained with 2,5-dihydroxybenzoic acid using on-line mixing of HPLC effluent and matrix solution. To demonstrate the potential of this capillary HPLC/MALDI-TOFMS method, its application to several single-bead libraries was investigated. The instrumental method allowed for the rapid identification and purity assessment of combinatorial libraries with detection limits down to the higher femtomole level using both UV detection and MALDI mass spectrometry.     

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.     

Jodometrische Titration von Perbromat (Bestimmung von BrO 4 − und BrO 3 − nebeneinander)

Perbromate is reduced to bromate by iodide in weakly alkaline solution (pH 7–9) at 100° C. The formation of iodine in the hot solution is prevented by addition of an excess of arsenite, which is finally titrated with a I₂-solution for the determination of BrO ₄ ^? . The total BrO ₃ ^? content is then determinated by titration of the acidified solution with thiosulphate. From both titrations the initial content of BrO ₃ ^? is obtained. Both methods are simple and accurate. A direct method for the determination of BrO ₃ ^? in solutions containing BrO ₄ ^? is also described.