Nachweis und Bestimmung des Nitrat-Ions

Ohne Zusammenfassung     

Über eine Schnellmethode zur Bestimmung des Carotins

Ohne ZusammenfassungMit 1 Abbildung.     

Refractive index and derived molecular properties of some gases determined by dispersive fourier transform spectroscopy (DFTS) in the visible wave number range

Dispersive Fourier transform spectroscopy (DFTS) is used to determine the dispersion of the real refractive indexn() of the gases CH₄, C₂H₄, C₂H₆, C₃H₈ and cyclo-C₃H₆ in the visible wave number range. Some molecular properties, e.g. oscillator strength sums, are derived from these measurements and compared with available data of literature.     

Shift in Critical Temperature for Random Spatial Permutations with Cycle Weights

We examine a phase transition in a model of random spatial permutations which originates in a study of the interacting Bose gas. Permutations are weighted according to point positions; the low-temperature onset of the appearance of arbitrarily long cycles is connected to the phase transition of Bose-Einstein condensates. In our simplified model, point positions are held fixed on the fully occupied cubic lattice and interactions are expressed as Ewens-type weights on cycle lengths of permutations. The critical temperature of the transition to long cycles depends on an interaction-strength parameter α. For weak interactions, the shift in critical temperature is expected to be linear in α with constant of linearity c. Using Markov chain Monte Carlo methods and finite-size scaling, we find c=0.618±0.086. This finding matches a similar analytical result of Ueltschi and Betz. We also examine the mean longest cycle length as a fraction of the number of sites in long cycles, recovering an earlier result of Shepp and Lloyd for non-spatial permutations.     

Application of on-line HPLC-ICP-MS for the determination of the nuclide abundances of lanthanides produced via spallation reactions in an irradiated tantalum target of a spallation neutron source

An analytical procedure has been developed for the determination of spallation nuclides in an irradiated tantalum target using HPLC coupled on-line to ICP-MS after dissolution and separation of the tantalum matrix. Pieces of tantalum were taken from different locations of the irradiated tantalum target which had been used as the target material in a spallation neutron source. Tantalum was dissolved in a HNO₃/HF mixture and the tantalum matrix was separated by liquid-liquid extraction so that only the spallation nuclides were left in the sample solutions. The major fraction of the spallation nuclides in the tantalum target are lanthanide metals in the μg g^–1 concentration range determined in the present study. Additional reaction products are formed by the irradiation of trace impurities in the original tantalum target. The nuclide abundances of the lanthanide metals measured in the tantalum target differ significantly from the natural isotopic composition so that a lot of isobaric interferences of long-lived radionuclides and stable isotopes in the mass spectrum are to be expected. Therefore, all the lanthanide metals had to be separated chemically prior to their mass spectrometric determination. The separation of all rare earth elements was performed by ion chromatography on-line to ICP-MS. The nuclide abundances of each lanthanide were determined using a sensitive double-focusing sector field inductively coupled plasma mass spectrometer. The nuclide abundances of the lanthanides in the irradiated tantalum target calculated theoretically and the experimental results obtained by on-line HPLC-ICP-MS proved to be in good agreement.     

Dual-detector-post-column reactor system for the detection of isoenzymes separated by high-performance liquid chromatography. II. Evaluation and application to lactate dehydrogenase isoenzymes

We describe the separation of lactate dehydrogenase isoenzymes by high-performance liquid chromatography-anion-exchange columns and their quantitation by a computer-controlled, dual-detector post-column reaction system. The recoveries from the separation column were ca. 90%. The dynamic range of the system was linear over about three orders of magnitude from 3 to 1500 U/l. The coefficient of variation for isoenzyme peak areas was ca. 2%. The method is compared to the classical electrophoresis measurement and shows increased speed, resolution, precision and accuracy.