Crystallite Nanosize Effect on the Structural Transitions of WO3 Studied by Raman Spectroscopy

Nanocrystallites of tungsten oxide samples of 2, 4, 16, 35 and 60 nm of diameter were prepared by cryosol and pyrosol techniques. The pressure- and temperature-induced phase transitions of these samples were monitored by Raman spectrometry from 0.1 MPa to 34 GPa and from 77 to 1200 K. The tetragonal (α)-orthorhombic (β)-monoclinic (γ) transitions in these nanometric samples are strongly downshifted in temperature by comparison with the bulk WO₃. For instance, the tetragonal phase which exists above 1171 K for the bulk tungsten oxide can be stabilized at 700 K for the 35 nm sample. In the same way, the monoclinic P2₁/n-monoclinic P2₁/c high-pressure-induced transition is slightly shifted from 0.1 GPa to a higher pressure (1.5 GPa). The discussion of these transition-line shifts is based on thermodynamic considerations in which the surface energy of crystallites plays an important role.     

基质固相分散气相色谱电子捕获检测器测定葡萄酒中5种农药残留

采用基质固相分散的样品前处理方法,替代传统的液-液萃取、固相萃取,从葡萄酒中提取、净化5种农药,气相色谱电子捕获检测器分析测定,基质匹配标准校正方法补偿基质效应。添加3水平(0.01-0.10mg/L)的回收率为85.7%-104.6%;相对标准偏差为3.6%-8.5%;检出限达到0.1-0.8μg/kg。本方法可用于葡萄酒样品中农药残留的测定。     

First access to the spin-labelled β-amino acid POAC in an enantiopure state by resolution through its binaphthyl esters

Resolution of trans 3-(9-fluorenylmethyloxycarbonylamino)-1-oxyl-2,2,5,5-tetramethylpyrrolidine-4-carboxylic acid (Fmoc-POAC-OH) was quickly achieved upon esterification with (aR)-1,1′-binaphthyl-2,2′-diol, chromatographic separation of the obtained diastereomers, and facile saponification of the aryl ester function with removal of the chiral auxiliary.     

双胺型键合固定相的制备及评价

首次将一种新型硅烷偶联剂β－（3，4－环氧环己基）乙基三甲氧基硅烷（β－ECTS）与己二胺反应，然后再键合到硅胶上，最后与辛酰氯反应得到双胺型键合固定相，并用元素分析、^13C固体核磁、红外光谱进行了表征，用中性、酸性和碱性有机化合物为探测因子对其进行色谱评价。结果表明：该固定相对含氮有机化合物的分离涉及疏水作用和离子排斥双重机理。     

β-胺基丙烯酸酯衍生物的不对称催化氢化反应研究进展

综述了近年来β-胺基丙烯酸酯衍生物的不对称催化氢化反应的研究工作, 并讨论了影响氢化反应活性与对映选择性的各种因素.     

Synthesis and applications of C2-symmetric guanidine bases

The preparation of the tetracyclic C₂-symmetric guanidinium salts 5 and 11-13 is reported together with their application to enantioselective transformations.     

Starburst dendrimer-supported pseudostationary phases for electrokinetic chromatography

Pseudo-stationary phases for electrokinetic chromatography were prepared by the alkylation of starburst dendrimers (SBDs). The SBD-supported pseudo-stationary phase with dodecyl groups showed higher efficiency than short-akyl derivatives, and maintained the hydrophobic property inthe presence of methanol. The dodecyl-modified SBD provided wide migration time windows ar high methanol content to effect the separation of sixteen aromatic hydrocarbons, the priority pollutants designated by EPA, in 65% methanol. The selectivity of polymer-supported pseudo-stationary phase can be varied simply by changing the length of the alkyl groups. The dodecyl SBD showed relatively similar selectivity as sodium dodecyl culfate micelle, whereas short alkyl derivatives showed preference towards rigid and planar compounds based on the rigid and planar compounds based on the rigid polymer backbones. The selectivity of SBD-supported pseudo-stationary phases was dominated by the chain length of the alkyl groups, with the minor effect of the structure of the core and the generation of SBD where alkyl groups were attached.     

碳十八键合锆胶固定相的制备与色谱性能评价

用诱导聚合胶体凝聚法（PICA）制得的二氧化锆微球与碳十八三乙氧基硅烷反应制备了碳十八键合锆胶固定相（ODZ），评价了该柱填料的色谱性能，并用此固定相分离了中性和碱性化合物。