On column injection-dual channel analysis of essential oils

A system to analyze a complex mixture simultaneously on two different columns after one single on-column injection is described. The splitting device, the possibilities of component identification by searching in a data base for Kovats indices on two different polarity stationary phases, and a practical example of an essential oil analysis are presented.     

The Chemistry of Coumarin Derivatives. Part 5. Unusual course of the reaction of 4-hydroxycoumarin and aliphatic aldehydes

The reaction of 4-hydroxycoumarin and certain aliphatic aldehydes affords 1:1 or complex 2:2 adducts besides (or in place) of the expected 2:1 bis(coumarin) adducts. Reaction with heptanal, cyclohexanecarbaldehyde, and pivalaldehyde are reported as representative. The structure of the reaction products was established by spectroscopical techniques, including X-ray analysis, and their formation was mechanistically rationalized. Some of the 1:1 adducts are synthetically useful for the preparation of 3-alkyl-4-hydroxycoumarins.     

Diketene-based neat four-component synthesis of the dihydropyrimidinones and dihydropyridine backbones using silica sulfuric acid(SSA)

Heterocyclic skeleton building blocks to afford dihydropyrimidinones and dihydropyridines based on neat adducts of diketene,alcohols and aldehydes via silica sulfuric acid(SSA) catalyzed ring opening of diketene in four-component Biginelli-type and Hantzsch-type reactions are presented.     

Chemical equilibrium controlled synthesis of polyoxymethylene dimethyl ethers over sulfated titania

The chemical equilibrium and reaction kinetic behavior in the synthesis of polyoxymethylene dimethyl ethers(DMMn) were investigated over sulfated titania in order to reveal the decisive factor controlling the reaction. The results showed that the molar ratio of adjacent DMMn products in equilibrium solution had the same value, which depended absolutely on the reaction temperature. Meanwhile, the reactions had the same DMMn products distributions under varied reaction conditions. The equilibrium constants of the related step-wise reactions for DMMn formation were equal, which were calculated based on the bulk compositions of the reaction solution. And thus, the selectivity to DMMn was mainly controlled by the chemical equilibrium, i.e., thermodynamic control. In brief, the present results provide some guidance for future synthesis of DMMn.     

The Suzuki homocoupling reaction under high-intensity ultrasound

The Pd-catalysed Suzuki homocoupling of boronic acids was successfully carried out in water under high-intensity ultrasound (HIU). Heterogeneous catalysis with Pd/C, facilitating work up and purification, could be used without adding phosphine ligands. Reaction rates and yields were strongly influenced by the oxidant employed; excellent results were obtained using either molecular oxygen or 3-bromo-4-hydroxycoumarin. 3-Arylation of the latter with the Suzuki procedure had failed, exclusively affording the homocoupling products, symmetric biaryls. Besides offering a number of operational advantages, the use of HIU broadens the field of application for the Suzuki reaction.     

SYNTHESIS AND CHARACTERIZATION OF SURFACE-HYPERBRANCHED MAGNETITE NANOPARTICLE FOR BOVINE SERUM ALBUMIN IMMOBILIZATION

A hyperbranched polyamidoamine polymer was synthesized on the surface of magnetite nanoparticles to enhance bovine serum albumin (BSA) immobilization efficiency. The amount of immobilized bovine serum albumin (BSA) on the surface-hyperbranched magnetite nanoparticle was up to 2.5 times as much as that of magnetite nanoparticle modified with only amino silane.     

Application of surface complexation modeling to the reactivity of iron(II) with nitroaromatic and oxime carbamate contaminants in aqueous TiO2 suspensions

This study reports on the application of surface complexation modeling to interpret observed kinetic trends for Fe(II) redox reactions with model nitroaromatic (4-chloronitrobenzene) and oxime carbamate (oxamyl) contaminants in aqueous TiO(2(s)) suspensions. Pseudo-first-order rate constants for reduction of the two probe contaminants (k(red), s(-1)) vary by several orders of magnitude with changing conditions (100-500 microM Fe(II), 0-15 g L(-1) TiO(2(s)), pH 2-9), but the relationship between reaction rates and Fe(II) speciation differs considerably for the two contaminants. For oxamyl, k(red) measurements are most strongly correlated with the volumetric total adsorbed Fe(II) concentration (moles Fe(II) adsorbed per liter of TiO(2(s)) suspension), whereas k(red) measurements for 4-chloronitrobenzene are proportional to the concentration of the hydrolyzed Fe(II) surface complex (equivalent TiOFe(II)OH(0)). The differing trends demonstrate that Fe(II) redox reactivity at the aqueous/TiO(2(s)) interface is influenced, in part, by specific molecular interactions with the target oxidant. Results are also geochemically relevant in that they demonstrate unambiguously that mononuclear Fe(II)-metal (hydr)oxide surface complexes are sufficiently reactive species to reduce nitroaromatic contaminants, an issue that remained open following earlier studies in Fe(III) (hydr)oxide suspensions because structural Fe(II) species are simultaneously present in such systems because of interfacial Fe(II)-to-Fe(III) electron transfer processes that occur on Fe(II) adsorption.     

多孔氧化铝模板制备ZnS纳米线阵列及其光致发光谱

利用阳极氧化铝（AAO）模板,采用电化学沉积方法制备出了ZnS纳米线阵列。扫描电子显微镜（SEM）结果显示,AAO模板孔洞分布均匀,孔径基本一致（约50nm）,孔口呈六边形。TEM结果显示硫化锌纳米线的直径约50nm（与AAM模板孔径一致）,长度约为20μm（与AAM模板厚度一致）。电子衍射结果表明ZnS纳米线为多晶结构。比较了AAO模板组装ZnS纳米线阵列前后的光致发光谱,所得光谱显示,组装了ZnS纳米线阵列的模板的光致发光谱比没有组装的空模板相比多出两个发射峰,分别位于409,430nm,且其发光强度随激发波长的增长而增强。解谱分析表明,这即为ZnS纳米线阵列的发光光谱的两个发射峰,是由导带与受主能级间的跃迁发光和施主与受主能级间的复合跃迁发光共同作用所致。发现由于纳米线尺寸的单一性,发射峰窄化明显,半峰全宽较小,这种现象在其他文献中未曾报道过。     

Statistical mixture design development of digestion methods for Oyster tissue using inductively coupled plasma optical emission spectrometry for the determination of metallic ions

The quantitative determination of chemical elements in organic or biological samples is an important analytical problem. Normally the elements to be determined in the organic matrix must be transformed into a simple inorganic form. A digestion method by heating on a block digestor has been developed for the determination of Al, As, Ba, Ca, Cd, Co, Cu, Fe, Mg, Mn, V and Zn in Oyster tissue by ICP OES. A simplex centroid statistical mixture design has been used to study the effects of changing HNO₃, HCl and H₂O₂ reagent proportions on the digestion of these samples. Response surface and principal component analyses show that the species Ca, Cd, Cu, Fe, Mg, Mn and Zn have very similar analytical tendencies under this experiment. By means of mixture modeling maximum recoveries for these ions were predicted using 19%, 18% and 63% of the HCl, HNO₃ and H₂O₂ pseudocomponent mixtures, respectively. This corresponds to 21.4%, 30.8% and 47.8% of the HCl, HNO₃ and H₂O₂ commercial solutions. Furthermore the As, Co and V ions present large recoveries for these mixtures as well. The Al and Ba ion recoveries are seen to be independent of the mixture proportions. The analysis of Oyster tissue reference material (SRM 1566b - NIST) under optimized conditions at the selected wavelengths resulted in ion recoveries between 90% and 100%.