Simultaneous determination of amino acids and carbohydrates by anion-exchange chromatography with integrated pulsed amperometric detection

A direct, sensitive, simple and practical method for simultaneous determination of amino acids and carbohydrates by anion-exchange chromatography with integrated pulsed amperometric detection was developed. The retention behavior of amino acids and carbohydrates on the anion-exchange column and the detection of amino acids and carbohydrates at different integrated pulsed amperometric detection waveforms were investigated. The optimized gradient eluent conditions for analysis of 17 amino acids and nine carbohydrates were obtained. Separation time was 100 min. Detection limits for amino acids and carbohydrates were 5.2-207.1 nM under injection volume of 25 microl. The RSDs of peak area were 1.2-3.3%. The calibration graphs of peak area for the analytes were linear over about three orders of magnitude with a correlation coefficient of 0.9950-0.9999. The method was applied to determine amino acids and carbohydrates in a liquid condiment with satisfactory results.     

Catalytic Asymmetric Assembly of Octahydroindolones: Divergent Synthesis of Lycorine‐type Amaryllidaceae Alkaloids (+)‐α‐Lycorane and (+)‐Lycorine

We report the first catalytic asymmetric approach to octahydroindolones and a divergent enantioselective synthesis of perhydroindole alkaloids, as exemplified by lycorine‐type Amaryllidaceae alkaloids (+)‐α‐lycorane and (+)‐lycorine, from a common intermediate by using a highly concise route. The assembly of octahydroindolones employs a catalytic enantioselective 1,4‐conjugate addition of nitro dienynes, followed by a TsOH‐catalyzed cascade synthesis of highly functionalized enones, and a diastereoselective intramolecular Michael addition.     

Retention behavior of transition metals on a bifunctional ion-exchange column with oxalic acid as eluent

The common eluents used with a bifunctional ion-exchange column (IonPac CS5A) for separating transition metals are pyridine-2,6-dicarboxylic acid and oxalic acid (Ox). When Ox is used, cadmium and manganese co-elute. Although much research has been done to overcome the Cd²⁺–Mn²⁺ co-elution problem, the role of lithium hydroxide in separating the transition metals has received little attention. In this study, it is found that when the Ox concentration is higher than 35 mM, Cu²⁺ elutes after Pb²⁺ and Ox plays a predominant role in the retention behavior of the seven metals. When Ox concentration is lower than 35 mM especially when its concentration (25 mM) is half of the usually used standard concentration (50 mM), Cu²⁺ elutes before Pb²⁺, and at the same time, Mn²⁺and Cd²⁺ can also be baseline separated. Lithium hydroxide plays a predominant role in the separation of the metals separated by cation exchange. So, lithium hydroxide is used to adjust the pH of the eluent. The use of an isocratic elution (25 mM Ox/LiOH/2 mM Na₂SO₄, pH 3.88) allows the separation of seven metals (Cu²⁺, Pb²⁺, Co²⁺, Mn²⁺, Cd²⁺, Zn²⁺ and Ni²⁺) in a single run. The effects of inorganic modifiers such as NaNO₃, Na₂SO₄ and Na₄P₂O₇ on retention behavior of the metals are also investigated.     

新同位素175Er

简介首次合成新核素１７5Ｅｒ及对其衰变纲图测定的实验方法和实验结果． the synthesis and γ decay scheme of new isotope175Er is reported for the first time.The related experimental process and main results are represented briefly also.     

超声介导微泡基因传递体系的研究

超声波能够在不损害人体正常组织的条件下,有效到达人体组织深处。超声造影剂（微泡）,能够显著提高血液和组织的背向散射强度,广泛应用于心血管疾病的检测中。超声微泡介导基因转染技术是指通过微泡的空化作用,实现超声波能量在靶向组织处的富集和释放,进而促进此处组织细胞对基因药物的内化,达到高效转染的目的。由于具有无创、高效安全的特点,超声微泡介导在基因治疗中具有很大的优势和潜力。利用微泡的超声成像功能实现对病变组织诊断成像,利用靶向组织处的超声实现时间空间可控的目的基因的释放,利用微泡在超声作用下的“声孔效应”,实现基因对多种生物膜的跨膜传递,达到基因药物的可视化传递与高效可控释放的目的。本文主要从超声造影剂的种类、超声微泡介导基因转染的机理、微泡基因传递体系的构建等方面,详细综述了这一领域最新的研究进展,并对超声微泡介导基因转染的发展进行了展望。     

Highly Selective Electrochemical Reduction of CO2 to Alcohols on an FeP Nanoarray

Electrochemical reduction of CO₂ into various chemicals and fuels provides an attractive pathway for environmental and energy sustainability. It is now shown that a FeP nanoarray on Ti mesh (FeP NA/TM) acts as an efficient 3D catalyst electrode for the CO₂ reduction reaction to convert CO₂ into alcohols with high selectivity. In 0.5 m KHCO₃, such FeP NA/TM is capable of achieving a high Faradaic efficiency (FE ) up to 80.2 %, with a total FE of 94.3 % at ?0.20 V vs. reversible hydrogen electrode. Density functional theory calculations reveal that the FeP(211) surface significantly promotes the adsorption and reduction of CO₂ toward CH₃OH owing to the synergistic effect of two adjacent Fe atoms, and the potential‐determining step is the hydrogenation process of *CO.     

Facile construction of the stable layer on the surface of Si/C electrode assisted by SWCNT coating

Journal of Solid State Electrochemistry - Silicon as one of the most promising anode materials suffers from its low electronic conductivity and large volume changes during the...     

1,3-丁二烯选择性加氢催化剂的设计策略以及构效关系

催化裂化是石油化工的核心单元之一.从催化裂化尾气中分离出来的碳四馏分富含许多的不饱和烯烃,如1-丁烯、顺、反式-2-丁烯以及少量的1,3-丁二烯,这些不饱和烯烃可以通过后续聚合反应,生成合成橡胶和工程塑料的重要原料,具有重要的应用价值.上述工艺过程对原料中1,3-丁二烯的含量(<100~200 ppm)有严苛的要求.采用选择性加氢技术对碳四馏分中的1,3-丁二烯进行选择性加氢,将其转化为更高附加值的单烯烃是一个理想的解决方案.然而,1,3-丁二烯加氢反应得到的单烯烃可能发生深度加氢得到副产物丁烷.因此,开发高效选择性加氢催化剂对碳四资源的利用具有重要的现实意义.另一方面,1,3-丁二烯加氢反应可以作为模型反应,用来考察选择性加氢催化剂的性能.基于此,该反应无论在工业界还是学术界均受到广泛关注.尽管如此,有关1,3-丁二烯加氢催化剂研究进展方面的综述极少.仅有关于1,3-丁二烯加氢作为模型反应的综述报道.本文对过去半个世纪以来1,3-丁二烯加氢反应中不同催化剂的发展历程进行系统综述,特别是包括Pd,Pt和Au等的单一贵金属催化剂.重点介绍以下内容:(1)固体催化剂构效关系,包括活性金属尺寸效应、晶面和形貌效应以及载体效应(晶相、孔道和酸碱性);(2)高性能催化剂的设计新策略,如单原子催化剂、核壳结构催化剂、金属-离子液复合催化体系以及载体的形貌调控;(3)催化剂的反应机理和失活机理.提出了1,3-丁二烯选择性加氢高性能催化剂开发面临的挑战,并对潜在的发展方向进行了展望.本文认为随着纳米技术和金属纳米材料合成方法的快速发展,对贵金属活性组分进行原子层面上的调控(包括形貌、尺寸以及单原子配位环境等)已成为可能.这将有助于研制出一类新型高性能选择性加氢催化材料,从而实现高转化率条件下高附加值单烯烃的定向转化.此外,载体的酸碱性和孔道结构的调控有助于进一步调节催化剂的抗积炭性能,也是未来发展的一个重要方向.     

Carbene‐Catalyzed Dynamic Kinetic Resolution and Asymmetric Acylation of Hydroxyphthalides and Related Natural Products

A catalytic dynamic kinetic resolution and asymmetric acylation reaction of hydroxyphthalides is developed. The reaction involves formation of a carbene catalyst derived chiral acyl azolium intermediate that effectively differentiates the two enantiomers of racemic hydroxyphthalides. The method allows quick access to enantiomerically enriched phthalidyl esters with proven applications in medicine. It also enables asymmetric modification of natural products and other functional molecules that contain acetal/ketal groups, such as corollosporine and fimbricalyxlactone C.     

纳米Pd粉的热稳定性研究

采用化学液相合成法制备了纳米Pd,热稳定性研究表明，温度在773～523K内，样品的平均粒径与退火温度T之间服从Arrhenius关系，且平均粒径与退火时间t之间满足经验公式=ktn。纳米Pd的热稳定范围T≤250℃。计算得到纳米Pd颗粒生长的表观激活能为0.15eV,远比纳米复合材料的生长激活能小（约为1eV）。故纳米Pd颗粒-极易长大，热稳定范围非常窄。