Porous ceramic bed supports for fused silica packed capillary columns used in liquid chromatography

Porous ceramic bed supports for fused silica packed capillary columns utilized in liquid chromatography were prepared by polymerizing solutions containing potassium silicate in-situ within a column to create a mechanically stable, rugged, and easily constructed termination. The effect of the bed support length on efficiency, and comparisons to glass wool bed supports, were considered in terms of column efficiencies and hydrodynamic variables. Results obtained indicate better performance for the ceramic bed support.     

Note on the ab initio PUHF treatment of open-shell systems

Ab initio projected-unrestricted Hartree-Fock calculations have been carried out on a number of excited and ionic states of the water molecule. Results have been compared with large-scale CI calculations, with IVO calculations, and with those of Mrozek and Golebiewski obtained by the 2 × 2 rotation method applied to orbitals. It is concluded that the PUHF method may provide the most useful alternative to large-scale CI for calculating properties of open-shell systems. But it will not be generally useful for calculating spectral transition energies.     

AlSiP3, a compound with a novel wurtzite-pyrite intergrowth structure

AlSiP₃ is formed by heating aluminum and silicon powder with red phosphorus and adding small amounts of iodine or AlCl₃. Small, black crystals with metallic lustre grow at 1200°K. The compound crystallizes in the orthorhombic space group Pmnb (No. 62) with a = 987.2 pm, b = 586.1 pm, c = 608.8 pm and four formula units. In the structure isolated P atoms as well as P₂ pairs are present (PP = 218.2 pm). Silicon is tetrahedrally bonded (SiP = 224.2 ? 228.2 pm) whereas aluminum has octahedral coordination (AlP = 244.2 – 260.8 pm). The structure can be described as an intergrowth structure of wurtzite and pyrite type.     

Untersuchung einer Methode zur Bestimmung von Blei, Cadmium, Quecksilber, Arsen und Tellur in Lebensmitteln mit Hilfe der R?ntgenfluorescenzanalyse

Zusammenfassung Der Aufschluß von Nahrungsmitteln tierischen Ursprungs mit Salpetersäure-Schwefelsäure in einer Polyäthylenflasche bei 60° C und mit Salpetersäure in einem Bombengefäß bei 150° C wurde untersucht. Beide Verfahren liefern befriedigende Ergebnisse. Im zweiten Fall besteht wegen kleinerer Reagensmengen jedoch eine geringere Gefahr des Einschleppens von Blindwerten. Blei, Cadmium und Quecksilber können aus der Aufschlußlösung durch Adsorption an dem Austauscherharz Chelex 100 oder durch Fällung mit Ammonium-pyrrolidindithiocarbamat unter Zusatz von Kupfer als Träger abgetrennt werden. Arsen und Tellur lassen sich anschließend zusammen mit Kupferträger durch Schwefelwasserstoff ausfällen. Die Ausbeuten für Aufschluß und Abtrennung liegen bei 90% oder darüber. — Die quantitative Bestimmung wurde mit Hilfe der energiedispersiven Röntgenfluorescenzanalyse durchgeführt, wobei ¹⁰⁹Cd bzw. ²⁴¹Am oder eine Röntgenröhre mit Zirkon oder Molybdän als Sekundärstrahler zur Anregung verwendet wurden. Beim Blei und Quecksilber konnten noch 1 g, beim Arsen und Tellur noch 0,5 g quantitativ bestimmt werden.

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Investigation of a method for the determination of lead, cadmium, mercury, arsenic and tellurium in food by means of X-ray fluorescence analysis

The decomposition of food of animal origin with a mixture of nitric acid and sulphuric acid in a polyethylene flask at 60° C and with nitric acid in a steel vessel at 150° C was investigated. Both procedures give satisfactory results. The advantage of the second procedure lies in the small amounts of reagents needed, thus keeping blank values low. Lead, cadmium and mercury can be separated from the decomposition solution by the chelating resin Chelex 100 or by precipitation with ammonium pyrrolidine dithiocarbamate, using copper as carrier. Arsenic and tellurium may be precipitated in the filtrate by hydrogen sulphide, using copper as carrier. The overall yields are about 90% or more. — The quantitative determination was performed by means of the energy dispersive X-ray fluorescence analysis, using ¹⁰⁹Cd or ²⁴¹Am sources or an X-ray tube with zirconium or molybdenum as secondary target for the excitation. 1 g of lead and mercury and 0.5 g of arsenic and tellurium could still be determined.

     

Stereochemistry of planarchiral compounds,part X

2,7-Dibromo-1,6-methano[10]anulene (3) and 2,9-Dibromo-syn-1,6:8,13-diimino[14]anulene (9) were quantitatively separated into their enantiomers by chromatography on triacetylcellulose (TAC) in ethanol. X-ray structure analysis (Bijvoet technique) established the chiralities (+)(R)-3 and (+)(S)-9 for the dextrorotatory enantiomers.Comparison of the CD spectra allowed the configurational assignment to further optically active [10] and [14] anulenes which were also accessible by chromatography onTAC. Conversion of (+)(R)-2-bromo-1,6-methano[10]anulene (2) into the corresponding methylester (–)-4 confirmed its previously proposed chirality (–)(R).2,7-Dibromo-1,6-oxido[10]anulene (7) and 2,9-dibromo-syn-diimino[14]anulene (9) are in contrast to the 2,9-dibromo-syn-dioxido[14]anulene (10) optically stable until 250°C. Consequently their inversion barriers are higher than 42 kcal (176 kJ) mol^–1.The CD spectra of mono and disubstituted anulenes (with C₁ and C₂ symmetry, resp.) are compared: For the [10]anulenes theCotton effect around 330 nm seems to be specific for their configuration with a positive effect indicating (S)-chirality and vice versa. Some regularities concerning the chromatographic resolutions are discussed.

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Stereochemie planar chialer Verbindungen, 10. Mitt.: Röntgenkristallstruktur und absolute Chiralität überbrückter [10]- und [14] Anulene

Zusammenfassung 2,7-Dibrom-1,6-methano[10]anulen (3) und 2,9-Dibrom-syn-1,6:8,13-diimino[14]anulen (9) wurden durch Chromatographie an Triacetylcellulose (TAC) in Ethanol quantitativ in ihre Enantiomeren getrennt. Röntgenstruktur-analyse (Bijvoet-Technik) bewies für die rechtsdrehenden Enantiomeren die Chiralität (+)(R)-3 bzw. (+)(S)-9.Ein Vergleich der CD-Spektren ermöglichte die Konfigurationszuordnung weiterer optisch aktiver [10]- und [14]Anulene, die gleichfalls durch Chromato-graphie anTAC erhalten worden waren. Umwandlung von (+)(R)-2-Brom-1,6-methano[10]anulen (2) in den entsprechenden Methylester (–)-4 bestätigte dessen schon früher vorgeschlagene Chiralität (–)(R).Dibrom-1,6-oxido[10]anulen (7) und Dibrom-diimino[14]anulen (9) sind im Gegensatz zum Dioxido[14]anulen (10) bis 250°C optisch stabil. Ihre Inver-sionsbarrieren liegen somit über 42 kcal (176kJ) mol^–1.Die CD-Spektren von mono- und disubstituierten Anulenen (mit C₁ bzw. C₂-Symmetrie) werden verglichen: Für die [10]Anulene scheint derCottoneffekt um 330 nm konfigurationsspezifisch zu sein, wobei ein positiver Effekt (S)-Chiralität anzeigt — und vice versa. Einige Regelmäßigkeiten bezüglich der chromatographischen Enantiomerentrennung werden diskutiert.

     

微波辅助溶剂热合成In-Si共改性TiO2的增强光催化性能

利用微波辅助溶剂热法合成了In-Si 共改性的TiO₂ 光催化剂. 粉末X 射线衍射（XRD）、激光拉曼（Raman）光谱、N₂吸脱附（BET）、X射线光电子能谱（XPS）、光致发光（PL）光谱和紫外-可见漫反射光谱（UV-VisDRS）等实验表明,尽管掺杂和改性后TiO₂结晶度略有降低,但不影响光催化剂锐钛相的形成. Si 掺杂入TiO₂晶格使颗粒变小,比表面积变大. In 不能进入TiO₂晶格,在TiO₂表面形成了In₂O₃. 罗丹明B（RhB）降解实验显示,In-Si 共改性TiO₂表现出很高的紫外和可见光催化活性,Si：In：Ti 的摩尔比为0.03：0.02：1 的样品（IST-2）光催化活性最高,紫外光下3 min 即可将RhB降解完全,可见光下120 min RhB降解率为97%,这是由材料的高表面积,In₂O₃-TiO₂复合半导体之间高效电荷转移及染料敏化等共同作用所致. 对于苯酚,光催化降解则相对缓慢,700 min内尚不能降解完全.     

C60离子束撞击固体表面的坍塌与沉积(II)扫描隧道显微研究

Mass-selected C60 beam produced by laser ablation was accelerated and bombarded the (0001) surface of highly oriented pyrolitic graphite and (111) surface of gold single crystal. The samples were characterized by STM. The STM images showed that, the deposited species collapsed and formed planar structure on the solid surface, but the collapsed species were not dissociated and well oriented on the surface. Both positive and negative C60 ions were observed in the desorption mass spectra, confirming that the species collapsed on the solid surface are still the C60 clusters.     

Hydroacridines XXV [1]. First Synthesis of (4aα,8aα,9aβ,10aβ)-Tetradecahydroacridine and New Syntheses of (4aα,8aα,9aα,10aβ)- and (4aα,8aβ,9aα,10aβ)-Tetradecahydroacridine

Summary. On heating in dry DMSO, in the presence of potassium t-butoxide, the N-nitrosamine of (4aα,8aβ,9aβ,10aα)-tetradecahydroacridine is completely converted into the N-nitrosamine of (4aα,8aα,9aα,10aβ)-tetradecahydroacridine. Under similar conditions, the N-nitrosamine of (4aα,8aα,9aβ,10aα)-tetradecahydroacridine yields a ternary equilibrium mixture containing itself (19%), and the N-nitrosamines of (4aα,8aβ,9aα,10aβ)-tetradecahydroacridine (46%) and the so far unknown (4aα,8aα,9aβ,10aβ)-tetradecahydroacridine (35%). The resulting N-nitrosamines can be smoothly denitrosated to the corresponding secondary amines.     

Raman spectra and structure of multicomponent oxide planar waveguides prepared by sol-gel

This work was aimed at understanding the structure of SiO₂–MO₂ (M = Ti, Zr, Hf) and SiO₂–HfO₂–MO₂ (M = Ti, Zr) materials, used as mixed oxide glass hosts for Er³⁺ ions in the fabrication of optical planar waveguides by sol-gel processing. This structural study was performed by Waveguide Raman Spectroscopy (WRS), complemented with X-ray diffraction (XRD). The admixture of TiO₂ to HfO₂, SiO₂–HfO₂ and HfO₂–ZrO₂ compositions was found to cause precipitation of nanocrystals of tetragonal HfO₂ or ZrO₂, or the formation of hafnia-titania mixed crystals, depending on the HfO₂/TiO₂ molar ratio.