横向加热石墨炉原子吸收光谱法测定茶叶中铅和镉

研究了横向加热石墨炉原子吸收光谱法测定茶叶中铅和镉,用磷酸二氢铵和硝酸镁作混合基体改进剂,消除基体干扰,铅和镉的检出限分别为0.0078和0.0015μg·g~(-1);相对标准偏差为:铅小于9.1％、镉小于5.0％;回收率为95％～114％。

铬Ⅵ-过氧化氢-鲁米诺化学发光法测定痕量抗坏血酸

基于抗坏血酸与铬 的还原反应产生的铬 催化鲁米诺 过氧化氢发光体系的研究 ,建立了一种快速测定痕量抗坏血酸的新方法。该方法线性范围为 8.0× 1 0 - 9～ 1 .6× 1 0 - 4mol L ,检出限为 8.0× 1 0 - 9mol L ,对 1 .0×1 0 - 6 mol L抗坏血酸 1 1次平行测定的RSD为 0 .9%。用于医用维生素C片剂中抗坏血酸含量的测定 ,结果令人满意。

稀土基汽车尾气催化剂的研究Ⅰ:催化剂老化和SO_2添加对催化活性的影响

制备了低Pt、Rh担载量的稀土基催化剂体系 ,研究了贵金属担载量、催化剂高温老化、抗硫水热老化和SO2 对催化活性的影响。结果表明 :随着贵金属质量分数从 0 2 5 %降低到0 1% ,CO、碳氢化合物 (HC)和NO的起燃温度分别平均提高 2 0℃ ;随着m(Pt)∶m(Rh)从 5∶1提高到 9∶1,CO、HC和NO的起燃温度分别提高 17、2 0和 5 3℃ ;当在反应体系中添加SO2 ,随SO2 体积分数从 0 0 0 2 %增加到 0 0 1% ,CO和NO的起燃温度和完全转化温度分别平均提高2 0℃ ,而对于HC ,催化活性几乎保持不变 ;催化剂在水热含硫条件下连续老化 4 0 0h ,CO、NO和HC的起燃温度分别为 2 5 2、2 6 7和 30 3℃ ,仍具有良好的反应活性。表明该稀土基催化剂在一定条件下 ,能满足汽车实际工况的要求

烯丙基取代的铁系“茂后”烯烃聚合催化剂的合成及其催化乙烯聚合的研究

合成了烯丙基取代的含氮中性配体 [( p-C3H5) C12 H16]2 N3C9H9,然后与 Fe Cl2 反应合成含烯丙基取代的三齿“茂后”烯烃聚合催化剂 [( p-C3H5) ( C12 H16) ]2 N3C9H9Fe Cl2 ,通过 IR,1H NHR,EI-MS对化合物进行了表征 .研究了它催化乙烯聚合的能力 ,这种催化剂与 MAO组成的催化体系可在常压下催化乙烯聚合 ,活性最高达 1 .9× 1 0 6g PE/ ( mol Fe· h) .所得聚乙烯粘均分子量在 5× 1 0 4 ～ 2 .6× 1 0 5之间

有机/无机纳米杂化材料载体化钛催化剂的聚合研究 Ⅱ.间同聚苯乙烯制备

以苯乙烯 -马来酸酐无规共聚物 ( SMA)为有机组分 ,以正硅酸乙酯 ( TEOS)为无机组分 ,利用 sol-gel方法制得纳米杂化材料 .以此为载体合成了载体化钛系催化剂 ,进行了苯乙烯聚合的研究 .聚合结果表明在50℃左右聚苯乙烯的间规度达到最大 ;随着反应温度的提高 ,分子量出现了下降现象 ,但反应活性提高 ,在70℃时 ,可达最高 1 .4 9× 1 0 6 g/( mol·h) ;并且分子量分布与文献结果相比也较宽 .

拉米呋定合成研究进展

综述了拉米呋定 ( Lamivudine)全合成研究进展。

Phase identification in a series of liquid crystalline TPP polyethers and copolyethers having highly ordered mesophase structures. 7. Phase structures in a series of copolyethers containing odd and even numbers of methylene units of different compositions

A series of liquid crystalline copolyethers have been synthesized from 1-(4-hydroxy-4'-biphenyl)-2-(4-hydroxyphenyl)propane with 1,7-dibromoheptane and 1,12-dibromododecene [coTPPs(7/12)], which represents copolyethers containing both odd and even numbers of methylene units. The molar ratio of odd to even methylene units in this series ranges from 1/9 to 9/1. The coTPPs(7/12) exhibit multiple phase transitions during cooling and heating in differential scanning calorimetry experiments. For all these thermal transitions, a small undercooling and superheating dependence is observed upon cooling and heating at different rates. Three types of phase behaviors can be classified in coTPPs(7/12) on the basis of the structural analyses by wide-angle X-ray diffraction on powder and fiber samples and by electron diffraction experiments in transmission electron microscopy. At room temperature, highly ordered smectic and smectic crystal (SC) phases are identified in coTPPs(7/12: 1/9 and 2/8), which is similar to the homopolymer TPP(m = 12). The coTPPs(7/12: 3/7, 4/6, and 5/5) possess a hexagonal columnar (Phi(H)) phase in which the molecular and columnar axes are parallel to the fiber direction and perpendicular to the hexagonal lateral packing. The coTPPs(7/12: 6/4, 7/3, and 8/2) possess a tilted hexagonal columnar (Phi(TH)) phase with a single tilt angle which increases with the increasing composition of the seven-numbered methylene units. However, in coTPP(7/12: 9/1), a Phi(TH) phase with multiple tilt angles is found. Upon heating, phase structures in most coTPPs(7/12) involving the columnar phases enter directly into the nematic (N) phase, while the coTPP(7/12: 1/9) exhibits a highly ordered smectic F (S-F) phase before it reaches the N phase. One exception is found in coTPP(7/12: 2/8), wherein the transformation from the S-F to Phi(H) occurs prior to the N phase. Combining the copolymer phase behaviors observed with the corresponding homopolymers TPP(n = 7) and TPP(m = 12), a phase diagram describing transition temperatures with respect to the composition can be constructed.