Theoretical and experimental study of the biamperometry for irreversible redox couple in flow system

The biamperometry for the direct determination of irreversible redox analytes in flow system has been proposed based on coupling two independent and irreversible couples to form the biamperometric detection scheme. In this work, the method is studied both theoretically and experimentally. Equations describing the current–voltage characteristics and the current–concentration relationship are presented. The influence of the applied potential difference (ΔE) and the half-wave potential difference (ΔE_1/2) between two irreversible couples on the method are discussed. It shows that small ΔE_1/2 is favorable to construct the biamperometric detection system and to achieve high sensitivity and selectivity. Increasing ΔE leads to an increase in sensitivity. This is, however, accompanied by a decrease in selectivity and signal-to-noise ratio. To construct the biamperometric scheme for the irreversible systems with large ΔE_1/2, two approaches, adjusting acidity of supporting electroyte or adding new irreversible couple, are proposed by taking uric acid/platinum oxide and phenol/permanganate systems as examples. Uric acid and phenol are, respectively, detected in a flow injection system with a biamperometric detector.     

含锆层柱蒙脱石对1,2,4三甲基苯歧化反应的催化作用

用离子共聚法合成了硅锆层柱蒙脱石（ＳｉＺｒＰＩＬＭ）和铁锆层柱蒙脱石（ＦｅＺｒＰＩＬＭ），考察了它们对１，２，４三甲基苯（１，２，４ＴｒＭＢ）歧化反应的催化性能．１，２，４ＴｒＭＢ在催化剂样品上可发生歧化反应和异构化反应，歧化反应选择性达８０％以上．随着催化剂预处理温度的提高，１，２，４ＴｒＭＢ转化率下降，歧化反应选择性和四甲基苯（ＴｅＭＢ）中１，２，４，５ＴｅＭＢ含量则升高．催化剂对１，２，４ＴｒＭＢ歧化反应有择形催化作用，１，２，４，５ＴｅＭＢ和间二甲苯、邻二甲苯为主要产物，并且其含量偏离其热力学平衡组成，ＴｅＭＢ中１，２，４，５ＴｅＭＢ的含量在８５％以上．     

硫酸氢铵分解动力学及其分解机理的研究

为了筛选适合的化学贮能系统,Wentworth等人曾提出了十项筛选标准。照此标准衡量,硫酸氢铵的分解-合成反应是一个十分理想的贮能系统: NH_4HSO_4(l)?NH_3(g)+H_2(g)+SO_3(g)Prengle也曾就此反应应用于太阳能电站贮能系统的可行性作过理论上的探讨.但是,有关该反应的基础研究进行的还很不够,特别有关分解动力学和分解机理的研究文献尚未见报导。本文用等温热重法和程序升温热重法对硫酸氢铵的热分解动力学进行了研究,并确定了分解机理,为贮能系统的实际应用提供了基础数据。     

New catalytic effect of thiourea on the oxidative cyanation of N-aryltetrahydroisoquinolines

Thiourea itself has been introduced as a mild and efficient organocatalyst for the oxidative α -cyanation of N-aryltetrahydroisoquinolines (THIQs) with trimethylsilyl cyanide (TMSCN), giving the corresponding products in good to excellent yields. Experimental investigations demonstrated that thiourea acts as a radical initiator by abstracting hydroxyl radical (OH) from tert-butyl hydroperoxide (TBHP) directly instead of non-covalent hydrogen bondings (H-bondings) activation. The use of thiourea as a radical initiator offers a new avenue for innovative chemical transformations in organocatalyzed radical chemistry.     

Quantitative study on selective stacking of zwitterions in large-volume sample matrix by moving reaction boundary in capillary electrophoresis

The paper advanced the theoretical procedures for quantitative design on selective stacking of zwitterions in full capillary sample matrix by a cathodic-direction moving reaction boundary (MRB) in capillary electrophoresis (CE) under control of electroosmotic flow (EOF). With the procedures, we conducted the theoretical computations on the selective stacking of two test analytes of L-histidine (His) and L-tryptophan (Trp) by the MRB created with 30 mM pH 3.0 formic acid-NaOH buffer and 2-80 mM sodium formate. The results revealed the following three predictions. At first, the MRB cannot stack His and Trp plugs if less than 12.5 mM sodium formate is used to form the MRB and prepare the sample matrix. Second, the MRB can stack His and/or Trp sample plugs completely if higher than 50 mM sodium formate is chosen to form the MRB. Third, the MRB can only focus His plug completely, but stack Trp plug partially if 20-50 mM sodium formate is used; this implied the complete MRB-induced selective stacking to His rather than Trp. All the three predictions were quantitatively proved by the experiments. With great dilution of sample matrix and control of EOF, controllable, simultaneous and MRB-induced selective stacking and separation of zwitterions were achieved. The theoretical results hold evident significances to the quantitative design of selective stacking conditions and the increase of detection sensitivity of zwitterions in CE. In addition, the control of EOF by cetyltrimethylammonium bromide (CTAB) can evidently improve the stacking efficiency to both His and Trp.     

Electronic stopping powers of Ni, Gd and Pd metals for 19F ions at low energy

Summary Electronic stopping power of ¹⁹F in Ni, Pd and Gd was measured and compared to Mstar and SRIM calculation as well as experimental results published in literature. It turns out that the present electronic stopping power agrees reasonably well with them.     

毛细管电泳中高盐样品在线富集的研究进展

在毛细管电泳分析过程中，简便高效的高盐样品处理技术对血清、尿液、海水和工业废水等样品的富集分析具有重要的意义。综述了在CE中高盐样品在线富集的若干种方法，包括乙腈法、瞬间等速电泳法、pH修饰法、动态pH联接法、胶束反应法和瞬间移动化学反应界面法，并简要地介绍它们的应用和研究进展。     

奋乃静和氟奋乃静的毛细管电泳柱端喷壁式安培检测

应用自组装毛细管电泳．安培检测装置，建立了同时分离检测抗精神病药奋乃静与氟奋乃静的新方法。在1050mV(vs．Ag／AgCl)检测电位下，奋乃静与氟奋乃静的检出限分别达0．060mg／L与0．075mg／L。在最佳检测条件下，两组分的响应电流与浓度之间有着良好的线性关系，线性范围为0．75～75mg／L。将方法用于药物片剂以及模拟尿样和血清样品中奋乃静和氟奋乃静的测定，结果令人满意。     

关于meso—四苯基卟啉在冰醋酸中的存在形式

前言卟啉在生物化学、分析化学、药物化学等领域有着广泛研究和重要应用［１～３］。近年来虽然对卟啉类化合物的研究报道很多［４～６］，但对卟啉在酸性介质中的研究很少。较早期的研究工作认为卟啉类化合物在酸性介质中仅以其二酸形式存在［７］。本文实验结果显示ｍｅ...