Facile synthesis and characterization of monocrystalline cubic ZrO2 nanoparticles

Crystalline ZrO₂ nanoparticles were prepared from zirconium isopropoxide by slow hydrolysis and subsequent hydrothermal treatment of solutions containing various amounts of sodium hydroxide at 180 °C. Whereas moderately basic solutions lead to the formation of nanoparticles of monoclinic ZrO₂ with plate-like morphology, and nanoparticles of the cubic ZrO₂ high-temperature polymorph with diameters of approx. 5 nm were obtained from strongly basic solutions. The morphology, structure and properties of as-synthesized nanoparticles were characterized using HRTEM, XRD, Raman spectroscopy, UV–vis, PL spectroscopy and BET measurements. The formation of both, the monoclinic and the cubic polymorph, was confirmed by electron microscopy and Raman spectroscopy. The crystallinity and morphology of the resulting ZrO₂ nanoparticles can be adjusted by the choice of the reaction conditions. The cubic ZrO₂ nanoparticles have a high surface area (300 m²/g) and exhibit a strong photoluminescence in the UV region.     

Determination of purines including 2,8-dihydroxyadenine in urine using capillary electrophoresis

For the purpose of rapid drug monitoring, methods have been developed for the determination of 2,8-dihydroxyadenine, allopurinol, oxypurinol, adenine, hypoxanthine, hippuric acid and xanthine in urine with and without sodium dodecyl sulfate as additive in sodium tetraborate running buffer. No sample preparation is necessary. 6-methylmercaptopurine and etofylline have been used as the internal standards. The limit of detection is 5 microM and the range of quantification stretches from 20 to 2000 microM. The capillary electrophoresis methods are simple, fast and robust.     

High-resolution analysis of polyprenols by supercritical fluid chromatography

A high-resolution analysis of polyprenol mixtures was achieved by supercritical fluid chromatography (SFC). The separation of polyprenols was examined on an octadecylsilane-packed column with liquid carbon dioxide as the mobile phase and ethanol as modifier. Using this chromatography system, the resolution of separation (Rs) between octadecaprenol (prenol 18) and nonadecaprenol (prenol 19) was two times higher than that using conventional reversed-phase high-performance liquid chromatography. Our SFC technique allows the advantage of baseline separation of polyprenol samples containing hydrophobic components such as terpenes or fatty acids that are unfavorable for good separation. This method is very useful for the analysis of structurally close polyprenol analogues of rubber plant metabolites.     

[Cl3PNPCl3][MoNCl4], eine Verbindung mit strangartig assoziierten Anionen

[Cl₃PNPCl₃][MoNCl₄], a Compound having Columns of Stacked Anions The title compound is formed by the reaction of [Cl₃PNPCl₃]Cl with MoNCl₃ in CH₂Cl₂ and subsequent precipitation with CCl₄ in from of orange-red crystals. According to the ³¹P-NMR spectrum, the compound exists as its isomer phosphaneiminate [Cl₅Mo(NPCl₂NPCl₃)] in CD₂Cl₂/CH₃CN solution. The crystal structure of [Cl₃PNPCl₃][MoNCl₄] is isotypic with that of [Cl₃PNPCl₃][MoOCl₄] and shows the same kind of two-dimensional disorder. X-ray diffraction patterns show planes of diffuse scattering as well as Bragg reflexions. The latter correspond to an averaged structure with a = 1590.0, b = 1141.6, c = 418.0 pm, space group Pba2, Z = 2. In the averaged structure (606 reflexions, R = 0.071) the atom sites have fractional occupation. The real structure consists of square-pyramidal [MoNCl₄]^? ions stacked to form columns with alternating MoN distances of 175 and 243 pm. The packing of the columns is disordered in that the [MoNCl₄]^? pyramids point either in the +c or ?c direction. The [Cl₃PNPCl₃]⁺ ions are stacked in the c direction and show two types of disorder, namely a displacement parallel to c and a rotation by 120° about the P? P axis.     

Benefits of high resolution IC-ICP-MS for the routine analysis of inorganic and organic arsenic species in food products of marine and terrestrial origin

A recently developed and validated method for simultaneous determination of 17 inorganic and organic arsenic compounds in marine biota has been successfully applied to routine analysis of different food products, including fish, shellfish, edible algae, rice, and other types of grain. During one year, approximately 250 food samples were analyzed, mostly fish and rice. Long-term stability and robustness of the system was observed and reproducible results for certified reference materials were ensured by means of control charts. The separation was performed by ion-pair chromatography on an anion-exchange column to separate anionic, neutral, and cationic arsenic species in one chromatographic run. Hyphenation to ICP–MS allowed element-specific and sensitive detection of the different arsenic species with a detection limit as low as 8 ng As L^–1 in the sample extract, which is equivalent to 2 ng As g^–1 in the original sample. Special emphasis was laid on the analysis of marine algae and rice samples. These food types can contain elevated levels of the very toxic inorganic arsenic species (up to 90% in rice) and therefore are the focus of interest in the food industry. In marine algae, inorganic arsenic was mainly present as arsenate whereas in rice arsenite predominated.     

Orientation reversing involutions and the first betti number for finite coverings of 3-manifolds

LetMS ³,P ³ be a closed, orientable irreducible 3-manifold which admits an orientation reversing involution :MM. If dim(Fix )=0, suppose ₁ (M) has a subgroup of even index. We show thatM has finite coverMMM} with ₁(M<0). As an application we show that the hyperbolic dodecahedral space has a finite cover with positive 1st betti number.     

Synthesis of Chiral 12-Phenyl(2H)dodecanoic Acids: Useful metabolic probes for the biosynthesis of 1-alkenes from fatty acids

The synthesis of chiral 12-phenyi(²H)dodecanoic acids as metabolic probes for the evaluation of the stereo-chemical course of the biosynthesis of 1-alkerses from fatty acids in plants and insects is described. The diastereoisomeric (2R, 3R)- or (2S, 3S)-12-phenyl(2,3?²H₂)dodecanoic acids 11 are obtained in high chemical and optical yield (>97% e.e.) from the readily available (E)-12-phenyl(2,3-²H₂)dodec-2-enoic acid ( 10 ) or (E)-12-phenyldodec-2-enoic acid ( 10a ) by microbial reduction with wet packed cells of Clostridium tyrobutyricum in either ²H₂O or H₂O buffer. (2R)- and (2S)-12-phenyl(2?²H)dodecanoic acids 9 (>97% e.e.) are accessible from the allylic alcohol 6 via Sharpless epoxidation with (+)-L- or (?)-D-diethyl tartrate, Synthetic routes to the (E)- and (Z)-11-phenyl(1?²H) undec-1-enes 16 and 16a as reference compounds are also included.     

P840-Reaction Centers from Chlorobium tepidum–Quinone Analysis and Functional Reconstitution into Lipid Vesicles

Membranes of Chlorobium tepidum contain about 35, 45 and2–10 molecules of menaquinone-7, chlorobium quinone (1′-oxo-menaquinone-7) and of the polar menaquinone (probably 1′-OH-menaquinone-7) per reaction center, respectively. None of these quinones was retained during the isolation of P840-reaction centers beyond the detection limit of about 0.2 quinones per reaction center, neither in the core complex nor in functionally intact reaction center preparations. The latter is shown to catalyze the formation of an electrochemical proton gradient in the presence of ascorbate and phenazinium methosulfate, when it is incorporated into lipid vesicles.