Comparative study on conventional and low-flow nebulizers for arsenic speciation by means of microbore liquid chromatography with inductively coupled plasma mass spectrometry

The performance of conventional and low-flow nebulizer systems with liquid chromatography in differentiating four arsenic species in urine was evaluated. Two low-flow (DIN and MCN) chamber assemblies and a conventional (CFN) nebulizer-spray chamber assembly were compared in the hyphenation of anion-exchange microbore liquid chromatography with inductively coupled plasma mass spectrometry. Under optimal analytical conditions, the detection limits of the four arsenic species were 0.2-0.6 ng ml(-1) for all the nebulizer systems tested. The chromatographic resolution was best in the case of DIN due to its minimal off-column dead volume and superior transport efficiency. Four arsenic species were determined in the certified reference materials NIST SRM 2670E and 2670N.     

Analysis of double-stranded DNA by microchip capillary electrophoresis using polymer solutions containing gold nanoparticles

The impact of gold nanoparticles (GNPs) on the microchip electrophoretic separation of double-stranded (ds) DNA using poly(ethylene oxide) (PEO) is described. Coating of the 75-microm separation channel on a poly(methyl methacrylate) (PMMA) plate in sequence with poly(vinyl pyrrolidone), PEO, and 13-nm GNPs is effective to improve reproducibility and resolution. In this study, we have also found that adding 13-nm GNPs to 1.5% PEO is extremely important to achieve high resolution and reproducibility for DNA separation. In terms of the stability of the GNPs, 100 mM glycine-citrate buffer at pH 9.2 is a good buffer system for preparing 1.5% PEO. The separation of DNA markers V and VI ranging in size from 8 to 2176 base pairs has been demonstrated using the three-layer-coated PMMA microdevice filled with 1.5% PEO containing the GNPs. Using these conditions, the analysis of the polymerase chain reaction products of UGT1A7 was complete in 7 min, with the relative standard deviation values of the peak heights and migration times less than 2.3% and 2.0%, respectively. In conjunction with stepwise changes of the concentrations of ethidium bromide (0.5 and 5 microg/ml), this method allows improved resolution and sensitivity for DNA markers V and VI.     

Tetra(μ3-hydroxo)hexa(μ2-carboxylato-O,O′)-bridged tetranuclear terbium(III) cubane complex

A novel tetranuclear terbium(III) complex [Tb₄(OH)₄(pybet)₆(H₂O)₈][Tb₄(OH)₄(pybet)₆(H₂O)₇ (NO₃)](ClO₄)₁₄·6H₂O has been synthesized and shown by X-ray crystallography to have a cubane-like Tb₄(μ₃-OH)₄(μ₂-carboxylato-O,O′)₆ core. The ligand pybet is pyridinoacetate, C₅H₅⁺N-CH₂CO₂⁻. Magnetic susceptibility data were measured for this Tb₄ complex in the range of 2.0–320 K and in fields of 1.0 G to 50.0 kG. It is concluded that either there is very weak antiferromagnetic exchange interaction (J = −0.015 cm⁻¹) or there is a small crystal-field splitting of the ⁷F₆ Tb^III ground state.     

铁改性的Mo/ZSM-5催化剂上NO的选择性催化还原反应

采用浸渍法制备了Mo/ZSM-5, Fe/ZSM-5和不同Fe和Mo摩尔比的Fe-Mo/ZSM-5样品, 并以氨为还原剂对其NO选择性催化还原活性以及反应条件对催化性能的影响进行了研究. 结果表明, Fe-Mo/ZSM-5样品的NOx转化率明显比单独的Mo/ZSM-5和Fe/ZSM-5的高. 当n(Fe):n(Mo)为1.5时, Fe-Mo/ZSM-5样品具有最佳催化性能, 其NOx转化率在430 ℃时达到了96%, 并且能在高空速和不同O2气浓度的条件下保持高的催化活性. 同时采用XRD和XPS技术分别对催化剂的体相结构和表面性质进行了研究, 结果表明, 当n(Fe):n(Mo)=1.5时, Fe和Mo元素之间以及与载体HZSM-5之间存在较强的相互作用, 并且其表面的Mo3d的含量最高. 这可能与其高的催化活性有关. 另外还发现, 在反应过程中Fe-Mo/ZSM-5催化剂表面的氮氧物种主要是吸附态NO, 因此可以推测NO的催化还原反应机理是, 在催化剂表面上, 吸附态NO与吸附NH3物种直接反应生成氮气, 而非经过氧化为NO2的途径.     

奎宁修饰的纳米铑簇合物催化丙酮酸乙酯对映选择性加氢反应研究

研究了奎宁作手性修饰剂修饰的负载型纳米铑簇合物催化剂 (Rh/ PVP-γ-Al2 O3)催化丙酮酸乙酯不对称氢化反应 ,在该反应中手性修饰剂奎宁不仅具有手性诱导作用 ,而且还有明显加速反应的作用 ;载体γ-Al2 O3在促进提高催化剂活性和对映选择性方面也有很重要的影响 .在优化的反应条件 [2 0℃ ,7.0 MPaH2 ,c(奎宁 ) =3 .86× 1 0 - 3mol/ L,四氢呋喃作溶剂 ]下 ,丙酮酸乙酯不对称加氢的转化频率 (TOF)为871 h- 1 ,对映选择性达到了 5 4.7% ;反应温度降低到 3℃时 ,对映选择性达到 5 9.2 % .     

Synthesis and Magnetic Properties of Fe（Ⅱ） and Nd（Ⅲ） Complexes of Poly（N-2-thiazolylacrylamide）

N-2-Thiazolylacrylamide （NTA） was polymerized by a radical route to obtain the polymer in good yield. The polymer with a pendent heterocyclic group is soluble in common organic solvents, which allow to prepare the corresponding metal complexes with higher loads easily. FTIR, ^1H NMR, elemental analysis, and energy-dispersive X-Ray spectroscopy （EDX） were applied to characterize these materials. The magnetic behavior of Fe（Ⅱ） and Nd（Ⅲ） complexes of poly（N-2-thiazolylacrylamide） was examined by a PPMS-9T magnetometer, exhibiting the characteristics of a soft ferromagnet. It is found that the Nd（Ⅲ） complex has an extremely high relative saturation magnetization of 35 emu/g.     

N-trifluoroacetyl sialyl phosphite donors for the synthesis of alpha(2 --> 9) oligosialic acids

[reaction: see text] A new method for the synthesis of alpha(2 --> 9) oligosialic acids is developed using phosphite sialyl donors that are protected with a C-5 N-trifluoroacetyl (NHTFA) substituent. Compared with conventional donors, these donors gave a higher degree of alpha-anomeric selectivity during glycosidic bond formation and better yields during iterative sialylation in the synthesis of oligosialic acids.     

Distinction between supercoiled and linear DNA in transverse agarose pore gradient gel electrophoresis.

Four species of linear DNA and the first four members of a linking series, generated by treatment of plasmid DNA (PUC19, 2.7 kb) with mitochondrial topoisomerase I, were differentiated by transverse agarose pore gradient gel electrophoresis. The experimental curves of migration distance vs. agarose concentration (Ferguson curves) of supercoiled DNA exhibit a steeper trajectory than those of linear DNA of the same size range. As a consequence, the four supercoiled species exhibit an increase in apparent size (relative to linear DNA standards) with increasing agarose concentration. Both the crossing of the Ferguson curves with those of linear standards as well as the apparent size increase with agarose concentration can serve to detect supercoiled plasmid-sized DNA in mixtures with linear DNA.     

3,4—亚甲二氧基苯甲酸锡酯的合成及表征

３，４－亚甲二氧基苯甲酸及其取代物与三苯基氢氧化锡或二丁基化锡反应合成了５个锡酯，通过元素分析，ＩＲ和＾１ＨＮＭＲ对其进行了表征。     

银络合物在催化核上的还原反应

研究了尿嘧啶银络合物在胶态金属及其硫化物核上被对苯二酚还原的反应，并以Ａｇ和Ｐｔ电极代替催化核与对苯二酚显影剂和银络合物组成原电池作为电化学模型，分别测定该络合物阴极反应和对苯二酚阳极反应的电流。结果表明，原电池的电流大小与反应速度成正比关系，从而为物理显影电极理论提供实验依据。