Use of blotting-paper collectors for the separation and X-ray fluorescent determination of traces of heavy metals (Cu, Hg, Ag) in water and waste water

Summary Traces of Hg, Ag and Cu were separated in the range of 0.5–500 g with blotting-paper collectors and were subsequently determined directly with energy dispersive X-ray fluorescence. For comparison, spectrophotometric determinations were carried out as well. The results were in good agreement. The collectors contained 0.2 mM ZnS, in case of Ag a thioureide collector was also employed. Limits of detection were 0.2 g Hg, 0.4 g Cu and 0.15 g Ag for the ZnS collector and 0.13 g Ag for the thioureide collector.

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Verwendung von Flie\papier-Kollektoren zur Abtrennung und röntgenfluorescenzspektrometrischen Bestimmung von Schwermetallspuren (Cu, Hg, Ag) in Wasser und Abwasser

Zusammenfassung Hg, Ag und Cu im Bereich von 0,5–500 g wurden auf Flie\papier-Kollektoren abgetrennt und direkt durch energiedispersive Röntgenfluorescenzanalyse bestimmt. Die Ergebnisse wurden durch Spektralphotometrie überprüft. Die Kollektoren enthielten 0,2 mM ZnS, für Ag statt dessen auch Thioureid. Alle Ergebnisse waren in guter übereinstimmung. Die Nachweisgrenzen für den ZnS-Kollektor betrugen 0,2 g Hg, 0,4 g Cu, 0,15 g Ag; für den Thioureid-Kollektor 0,13 g Ag.

     

Graphite multi-micro-disc based mercury film electrode: Comparison of experimental and theoretical anodic stripping results

an ensemble of properly distanced micro mercury film electrodes (MMFE) was used in cyclic and anodic stripping voltammetry. the experimental results were compared with the anodic stripping theory, and the agreement was found to be satisfactory. The MMFE peaks (calculated per unit area) were higher, thinner and shifted towards more negative potentials compared with the large area mercury film electrode (LAMFE) peaks.The initial graphite electrode consisted of 65 independent micro-discs forming a circle, and was prepared from carbon fibres 4.66 μm in radius. The graphite multi-micro-disc electrode was quantitatively checked in a Fe(CN)₆^3? solution under both chronoamperometric and voltammetric conditions. The deposition and oxidation of mercury is discussed also.     

An idea of half-space thermal mirror

The paper describes a theoretical discussion of the optical reflecting properties of an isotropic thermoelastic half-space subjected to an instantaneous heat pulse at a point of its surface (such a system is called the half-space thermal mirror). The fundamental optical properties of the mirror so obtained (i.e.—its aberration characteristic, including optical power and focal length), and their time evolution are derived in the paper. The half-space thermal mirror represents an optical device suffering rather high aberrations; the paraxial optics approximation, and criteria of its applicability for such a mirror are given. Possibilities of an application of the thermal mirror for determining the temperature conductivity of a material are considered.     

Structures of Four Crystal Forms of Decaplanin

The glycopeptide antibiotic decaplanin ( 1 ; formerly known as MM 47761 and M86‐1410) crystallizes in two P2₁ and two P6₁22 crystal forms, each with four monomers in the asymmetric unit, with solvent contents varying from 48 to 69%. Although with ca. 600 unique atoms, the structures are larger than typical small molecules, one was solved by direct methods. The other three were solved by typical macromolecular methods: single‐wavelength anomalous diffraction (SAD) of the Cl‐atoms present naturally in the structure, multiple‐wavelength anomalous diffraction (MAD) at the Br absorption edge for a crystal soaked in NaBr solution, and molecular replacement. There is evidence of appreciable radiation damage with loss of 20–30% of the covalent and ionic halogens affecting the synchrotron datasets that may even have unintentionally facilitated the MAD structure solution. The structures contain the dimer units typical of antibiotics related to vancomycin, but, in addition, there are a variety of further intermolecular interactions responsible for the polymorphy leading to intertwined 6₁‐helices in two of the crystal forms. Except for the sugars and some sidechains, the conformations of the 16 independent monomers are very similar.     

Canonical models for a class of polynomially convex hulls

We use holomorphic motions and Beltrami equation to study a class of polynomially convex hulls in ℂ ² with Jordan fibers over the disc D. It is shown that every such hull is biholomorphically equivalent to a unique (up to suitable normalisation) canonical model. These models are the hulls whose complements in D×ℂmacr; are biholomorphic to a bidisc and are further characterized in terms of capacity of the fibers, Green’s function, pseudoconcavity and approximability by (very) special analytic polyhedra. Received: 11 September 1995 / Revised version: 11 March 1996