Development of a quick leaching test for monolithic materials by using factorial design

A quick leaching test procedure for monolithic waste materials has been developed by a Nordic expert group using experimental factorial design. The Dutch quick leaching test proposal in which the wetting time of the test specimen is reduced by applying vacuum was chosen as a starting point. The influence of the following parameters were studied: vacuum, stirring, open or closed vessel, water renewal frequency, leachant quality and laboratory or batch differences. The study was performed with test specimens prepared from a cement stabilised soil containing As, Cr and Cu. The test specimens were immersed in water and the water was renewed at certain time intervals. The study clearly showed that the use of vacuum had a strong effect on the release rate and that the open vessel lowered the pH-values of the eluates due to uptake of carbon dioxide in the water. The results also indicate higher emissions when stirring was applied. The following test conditions are recommended: application of vacuum prior to testing, use of closed test vessel, use of stirring, a test time of 3 days with four water renewals after 15 min vacuum steps, and then after e.g. 2 h, 23 h and 3.2 days, use of demineralised water as leachant. The amount of water must be selected according to the size of the test specimen. A liquid to surface (L/A) ratio of 5-10 ml cm(-2) is recommended. All four eluates collected are filtered and analysed.     

Implementation of traceability – needs and perspective of the in-vitro-diagnosticum industry

Manufacturers support the concept of traceability. However, only a small number of the medically relevant measurands can be traced to the highest metrological order. In many cases, the measured substances are heterogeneous mixtures where traceability can be established only to either an international conventional reference measurement procedure or to a manufacturers own in-house reference system. The traceability concept needs to be seen in the context that the results of medical laboratories are not an aim per se, but are meant to provide useful medical information to clinicians, and that pre- and post-analytical steps may also contribute significantly to errors. There is a need for the further development of suitable reference measurement systems, but in view of the multitude of tasks and limited resources, priorities need to be set.Presented at BERM-9 – 9^th International Symposium on Biological and Environmental Reference Materials, 15–19 June 2003, Berlin, Germany     

Dynamic microwave-assisted extraction coupled on-line with solid-phase extraction: determination of polycyclic aromatic hydrocarbons in sediment and soil

This paper describes a new extraction tool for the determination of polycyclic aromatic hydrocarbons (PAHs) in soil and sediment samples, using dynamic microwave-assisted extraction combined with solid-phase extraction (DMAE-SPE). The critical variables for DMAE-SPE are investigated and optimized in an experimental design. The technique proved to be fast, accurate and able to yield quantitative extraction of PAHs from naturally contaminated sediment and soil samples. The set-up is fully automated and features monitored extraction, which facilitates rapid optimization of the method. In addition, only small quantities of solvent and sample are required.     

The simplest coronoids: Hollow hexagons

Hollow hexagons form a subclass of primitive coronoid systems. The macrocyclic aromatic hydrocarbon kekulene corresponds to a hollow hexagon. The hollow hexagons for given numbers of hexagonal units (h) were enumerated by computer aid, but also an analytical solution for the numbers of hollow hexagons was achieved. For the Kekulé structure counts (k) of a hollow hexagon a general formula is reported. Also the maximum and minimumK numbers are considered.This article is Part VI of the series Enumeration and Classification of Coronoid Hydrocarbons. For Part V, see ref. [36].     

Regiospecific synthesis of mono-N-substituted indolopyrrolocarbazoles

[reactions: see text] Two complementary and efficient strategies have been developed for the regiospecific synthesis of unsymmetrical indolopyrrolocarbazoles (IPCs) mono-N-substituted with a pentacycle. A halogen in position 2 of the intermediate bisindolylmaleimides 3a-e allows a selective Mitsunobu coupling by exploiting the increased acidity of the 2-chloro-substituted indole nitrogen. It also promotes an easier cyclization of bisindolylmaleimides 4a-e and 7b-e to IPCs. Alkylation of the 2-unsubstituted indole-3-carboxamides 2a,b and further processing to the corresponding IPCs gives access to the opposite regioisomers.     

A recycling technique for the chromatographic separation of enantiomers and diastereomers on triacetylcellulose

A simple and inexpensive equipment for the optical resolution of enantiomers (and separation of diastereomers) on triacetylcellulose in ethanol at elevated pressure is described. It involves a closed circuit of solvent (pump—column—detector—pump) allowing a continuous chromatography up to 16 cycles without stopping the flow or handling fractions.This useful and versatile method permitting also the determination of enantiomeric purities is illustrated by several examples of centro-, axial- and planarchiral arenes and metallocenes.Herrn Prof. Dr.U. Schmidt, Stuttgart, zum 60. Geburtstag gewidmet.     

Hyperfine structure of the 625 nm band in the a 3Πu ← X 1 Σg transitions of Na2

Hyperfine structures of transitions in the a ³Π_u ← X¹Σ_g system of Na₂ have been accurately measured by Doppler-free laser excitation spectroscopy in a collimated molecular beam. The hyperfine patterns are quantitatively explained and the reduced matrix elements of the magnetic dipole hf interaction determined from a least-squares fit to the measured line positions.     

Chemical fourling on the unit cell level as a structure-building operation in the solid state

Chemical fourling on the unit-cell level is introduced as a structure-building operation in the solid state. A chemical fourling structure is achieved when two twin planes are perpendicular to each other. Each fourling unit has infinite extension in only one direction and can be related to a well-known structure type or packing of atoms. The structures of the tetragonal tungsten bronzes M_xWO₃ and Pd(NH₃)₄Cl · H₂O are presented as examples of chemical fourlings of cubic close packing. The structures of SeO₂, Mn₂Hg₅, and Zr₂F₇O are shown to be a sequence of chemical fourlings of primitive cubic packing. Chemical fourling units of hexagonal close packing are found in the structures of tetragonal Ti₃Sb, α-V₃S and Sb₆O₇(SO₄)₂. The structures of CuAl₂, SeTl, NbTe₄, Ti₃Sb, and MnU₆ all have the same chemical fourling unit. Cr₂₃C₆ is described as a bounded chemical fourling of cubic close packing.     

Analyse von Rutil-Anatas-Gemischen mittels diffuser Reflexionsmessungen

Zusammenfassung Pulvergemische von zwei verschiedenen Modifikationen eines Stoffes oder von zwei Pigmenten lassen sich mit Hilfe diffuser Reflexionsmessungen quantitativ analysieren, wenn die Reflexionsspektren sich in einem zugänglichen Spektralgebiet genügend stark unterscheiden. Die Methode wird am Beispiel der Titandioxyde Rutil und Anatas im einzelnen beschrieben.

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Summary Mixtures of two modifications of solid powdered material can be quantitatively analyzed by diffuse reflectance measurements, if the reflectance spectra are sufficiently different in some wavelength range. The method is described with the example of the titanium dioxides rutile and anatase.

     

Resonant electron transfer andL-shell excitation at 3.6 MeV/u62Sm q+ → Xe collisions,q=34−52

For 3.6 MeV/u Sm ^q+ projectiles a hump in the projectile (L _l +L _α) x-ray emission cross section is seen as a function of charge stateq for highq with 46≦q≦52 (closed incomingL shell). This hump is attributed to the Resonant electron Transfer from the Xe target atom with simultaneous Excitation of anL ₃-shell electron to theM shell. The cross section for thisL ₃-shell RTE process has values up to 2·10^?19 cm², which is seen in single spectra already. To verify the existence of theL-shell RTE process for the studied collision system, extensive calculations have been carried out. Especially theL ₃-shell fluorescence yield for the radiative stabilization process in the highly-charged projectile has been considered. Our calculatedq-dependent cross sections for the RTE process support the given interpretation.