Neutron activation analysis of extractable organohalogens in milk from China

Instrumental neutron activation analysis (INAA) has been used for the determination of extractable organohalogens (EOX) in milk. The detection limits are 50 ng, 8 ng and 3.5 ng for Cl, Br and I, respectively. The EOX concentrations in milk samples from various regions of China were determined. Meanwhile, organochlorine pesticides residues were detected by gas chromatography. The concentrations of the EOX in the milk samples are decreasing in the order of EOCl >> EOBr > EOI, and EOCl accounts for 95% of the total EOX. The average concentration of EOCl in milk is 4.44 ·g/g expressed as fat weight basis, with the highest value of 17.6 ·g/g from South China. The mean concentrations of total HCH and DDT are 0.038 ·g/g and 0.046 ·g/g, respectively. Organochlorine pesticides account only for 1.6% of the EOCl, indicating the very high proportion of the unknown EOCl in the milk sample. This revised version was published online in August 2006 with corrections to the Cover Date.     

N8H8链状异构体结构与稳定性的理论研究

采用密度泛函理论(DFT), 在B3LYP/6-311＋＋G(d,p)基组上计算得到了21种N₈H₈链状异构体, 并研究了这些异构体间可能的互变异构情况. 为了得到更为精确的能量信息, 计算了QCISD(T)/6-311G(d,p)基组水平上各物质的能量. 所得的21种异构体分为4类(4种类型链状化合物): A为直链, B有一个支链, C有2个支链, D有3个支链; D类只有一种, A类稳定构型2种, B类稳定构型12种, C类稳定构型6种; 相对稳定的分别为: B2-1构型, B2-3构型和C23-2构型. 我们研究发现N₈H₈链状异构体中含有明显N＝N双键特征有利于化合物稳定性的提高.     

Two new megastigmane O-glucopyranosides from the leaves of Broussonetia papyrifera

Two new megastigmane O-glucopyranosides,named (2R,3R,5R,6S,9R)-3-hydroxy-5,6-epoxy-β-ionol-2-O-β-D-glucopyrano- side(1) and (2R,3R,5R,6S,9R)-3-hydroxyl-5,6-epoxy-acety-β-ionol-2-O-β-D-glucopyranoside(2) together with six known mega- stigmanes,were isolated from the leaves of Broussonetia papyrifera (Linn.) Vent.Their structures were established by chemical methods and spectroscopic techniques including 2D NMR.     

BaFeO3-x与Cu-ZSM-5耦合催化剂的NOx储存还原性能

为替代传统的贵金属基NO_x储存还原（NSR）催化剂,本文设计并制备了不含贵金属的BaFeO_3-x+Cu-ZSM-5 耦合催化剂,用于催化消除稀燃发动机尾气中的NO_x. 在稀燃阶段,NO在BaFeO_3-x催化剂上发生了氧化和储存反应;在富燃阶段,从BaFeO_3-x催化剂中脱附出来未能消除的NO_x被置于其后的Cu-ZSM-5催化剂进一步催化消除. 实验结果表明,BaFeO_3-x+Cu-ZSM-5 耦合催化剂的工作温度窗口被拓宽到250-400 ℃,同时NO_x消除性能得到了显著提高：NO_x转化率最高可达98%,N₂选择性接近100%.     

不同嵌段比的PEG-b-PDMAEMA共聚物在水溶液中的自聚集行为

采用氢核磁共振(¹H-NMR)、动态光散射(DLS)及透射电子显微镜(TEM)对聚乙二醇-嵌段-聚甲基丙烯酸N,N-二甲氨基乙酯(PEG-b-PDMAEMA)三种具有不同PEG/PDMAEMA嵌段比的PEG-b-PDMAEMA共聚物在水溶液中的自聚集行为进行了研究. 研究表明, 两嵌段比例是影响聚合物胶束化过程的关键因素: 只有当其中聚乙二醇含量较低(质量分数低于33%)时, 聚合物才具有其pH/温度敏感胶束化特性. 此外, 共聚物溶液随温度胶束化过程与共聚物嵌段比大小密切相关. PEG-b-PDMAEMA这种不同于传统双亲性嵌段共聚物(DHBCs)在选择性溶剂中独特的胶束化行为, 是由聚合物溶液体系中各种基团之间的氢键作用决定的.     

噁二唑肟醚取代的均三唑水杨醛席夫碱衍生物的合成及抗菌活性

均-三唑;噁二唑;肟醚;席夫碱;合成;抗菌活性     

Monte Carlo simulation of adsorption of binary and quaternary alkane isomers mixtures in zeolites: Effect of pore size and structure

Grand canonical Monte Carlo and configurational bias Monte Carlo techniques were employed to simulate the adsorption of binary mixtures of butane isomers and quaternary mixtures in nine zeolites at 300 K. For binary mixtures the results show there is a critical pore size, which is 10-membered-ring about 5.6 Å. The channel sizes of BEA, ISV, MOR and CFI are larger than this critical pore size, they prefer i-butane than n-butane, whereas TON with smaller channel size than critical pore size prefers n-butane than i-butane, but its selectivity decreases with pressure increasing. MFI, MEL and TER prefer i-butane than n-butane at low pressure, but with pressure increasing, the selectivity is reversed. BOG prefers i-butane than n-butane but the selectivity decreased with pressure increasing. It demonstrates that the adsorption and selectivity are controlled by both pore size and pore structure. The n-butane–i-butane–n-pentane–2-methylbutane quaternary mixtures adsorbed in these nine zeolites were studied, and the results show alkane chain length dependence at low pressure, but the adsorption is controlled by pore size and structure with pressure increasing in all the zeolites except for TON and BOG.     

野生与种植青海川西獐牙菜中微量元素的测定

为了对比野生与种植青海川西獐牙菜中微量元素的变化,分别采集野生川西獐牙菜与种植青海川西獐牙菜种子采收前后的全植株,采用原子吸收光谱仪测定了其铜、锌、铁、锰、钴等微量元素含量。结果表明,野生川西獐牙菜较种植青海川西獐牙菜中微量元素含量高,种植川西獐牙菜在成熟种子采收后较采收前(花果期)铁、锰、钴、锌等元素含量高。     

Bola型阴离子表面活性剂与溴化十二烷基三乙铵混合体系的表面性质与聚集行为

研究了具有简单结构的bola型阴离子表面活性剂二十酸二钠（C_(20)Na_2)与 阳离子型普通表面活性剂溴化十二烷基三乙铵（C_(12)Et_3）混合体系的表面性质 ，发现混合体系的cmc和γ_(cmc)比C_(12)Et_3单一体系未有显著降低。以负染色 ，FF-TEM，动态光散射（DLS）及粘度方法研究了混合体系的聚集行为，发现混合 体系中同时形成球形囊泡和管状聚集体，提出了产生这种聚集行为的机制。     

Novel spectrofluorimetric method for the determination of sulfite with rhodamine B hydrazide in a micellar medium

A novel spectrofluorimetric method for the determination of sulfite using rhodamine B hydrazide as fluorogenic reagent in the presence of polyoxyethylene sorbitan monooleate (Tween 80) surfactant micelles is described. The method is based on the mixture of sulfite with rhodamine B hydrazide, a colorless, non-fluorescent substance in Tween 80 surfactant micelles which gives rhodamine B-like fluorescence emission. The fluorescence intensity increase is linearly related to the concentration of sulfite in the range 5-800 ng ml⁻¹ with a detection limit of 1.4 ng ml⁻¹ (3σ). The optimal conditions for the detection of sulfite are evaluated and the possible detection mechanism is also discussed. The method has been successfully applied to the determination of total sulfite in wines and compares well with the standard iodimetric method.