Neue Germanide mit geordneter Ce3Pt4Ge6‐Struktur – Die Verbindungen Ln3Pt4Ge6 (Ln: Pr–Dy)

New Germanides with an Ordered Variant of the Ce₃Pt₄Ge₆ Type of Structure – The Compounds Ln₃Pt₄Ge₆ (Ln: Pr–Dy) Six new germanides Ln₃Pt₄Ge₆ with Ln = Pr–Dy were synthesized by heating mixtures of the elements at 900 °C, annealing the inhomogeneous powders at 1050‐1100 °C for six days and then cooling down from 700 °C in the course of two months. The crystal structures of Pr₃Pt₄Ge₆ (a = 26.131(5), b = 4.399(1), c = 8.820(2) Å), Sm₃Pt₄Ge₆ (a = 25.974(3), b = 4.356(1), c = 8.748(1) Å), and Dy₃Pt₄Ge₆ (a = 26.079(5), b = 4.311(1), c = 8.729(2) Å) were determined by single crystal X‐ray methods. The compounds are isotypic (Pnma, Z = 4) and crystallize with an ordered variant of the Ce₃Pt₄Ge₆ type of structure (Cmcm, Z = 2) consisting of CaBe₂Ge₂‐ and YIrGe₂‐analogous units. The platinum atoms are located in distorted square pyramids of germanium atoms and build up with them a three‐dimensional network. The coordination polyhedra of the platinum and germanium atoms around the rare‐earth metal atoms are pentagonal and hexagonal prisms. These are completed by some additional atoms resulting in coordination numbers of 14 and 15 respectively. The other germanides were investigated by powder methods resulting in the following lattice constants: a = 26.067(6), b = 4.388(1), c = 8.800(2) Å for Ln = Nd; a = 25.955(7), b = 4.337(1), c = 8.728(2) Å for Ln = Gd; a = 25.944(5), b = 4.322(1), c = 8.698(2) Å for Ln = Tb. The atomic arrangement of Ln₃Pt₄Ge₆ is compared with the well‐known monoclinic structure of Y₃Pt₄Ge₆.     

Analysis of Chlormequat residues in grain using liquid chromatography-mass spectrometry (LC-MS/MS)

A fast, sensitive and specific method for routine determination of residues from Chlormequat (CAS no. 7003-89-6) is described. The method is based on a simple clean-up using an SPE-C₁₈ cartridge, high-performance liquid chromatography on a standard C₁₈ column (Spherisorb S5 ODS1) and specific detection and quantification by electrospray mass spectrometry (LC-MS/MS). ¹³C-Chlormequat was synthesised for use as internal standard. Samples were extracted with methanol – water – acetic acid. Internal standard and ammonium acetate were added before C₁₈-cartridge clean up and residues eluted with methanol – water – acetic acid, containing 50 mM ammonium acetate. Chromatographic separation was achieved using a solvent composed of acetonitrile – methanol – water – acetic acid (53:21:25:1 by volume), containing 50 mM ammonium acetate. Electrospray ionisation mass spectrometry was employed using m/z 58 (daughter ion of the Chlormequat quaternary ammonium ion, m/z 122) and m/z 61 (daughter ion of the ¹³C-Chlormequat quaternary ammonium ion, m/z 125) for quantification. The LC analysis time was 15 min and the limit of detection of the analytical method was 9 μg/kg. The performance of the method was demonstrated analysing grain material from an inter-comparison study. In Denmark the primary use of Chlormequat chloride (CCC, cycocel, or chlorocholin chloride, CAS no. 999-81-5) is for winter cereals and 11 such winter wheat samples from the Danish National Pesticide Survey were analysed. Residue contents were from below 0.01 up to 0.45 mg/kg, and thus below the EU maximum residue level of 2.0 mg/kg for wheat. Received: 22 December 1997 / Revised: 29 January 1998 / Accepted: 31 January 1998     

Atomic force microscopy on human trabecular bone from an old woman with osteoporotic fractures

AFM images were taken of the exterior surface of a single trabecula, extracted from a human femoral head removed during surgery for a hip fracture in an old women with former fractures. The images showed a dense structure of bundled collagen fibrils banded with 67 nm periodicity. Bundles were seen to run in parallel in layers confirming the collagen structure seen by other techniques. Single collagen fibrils were seen to cross the bundles, thus forming cross-links between neighboring bundles of collagen fibrils. Some of these crossing fibrils did not have the 67 nm band pattern and their dimensions were about half compared to the neighboring collagen fibrils. Very little mineral was found on the surface of the trabecula. An AFM image of a fracture plane was also displayed. The trabecula was extracted from a region close to the hip fracture. However, there were in this case no obvious features in the images that could be linked directly to osteoporosis, but altered collagen banding and collagen protrusions may alter mechanical competence. A path to extensive studies of the nanometer scale structure of bone was demonstrated.     

Cu-ZSM-5/堇青石整体式催化剂上NO的吸附态及分解反应机理

 用傅里叶变换漫反射红外光谱法研究了原位合成的不同硅铝比的Cu－ZSM－5／堇青石整体式催化剂上一氧化氮的吸附态,以及温度和一氧化氮浓度对吸附态的影响．结果表明,铜在整体式催化剂中主要以二价铜离子的形式存在,未发现一氧化氮在一价铜离子上的特征吸收峰;由二价铜的一氧化氮吸附物种衍生的Cu2＋（O）（NO）是与活性密切相关的物种．探讨了NO分解可能的反应机理．