生物、土壤中痕量铜的催化分析

一、概述本世纪五十年代发展起来的动力分析法,特别是催化分析,已在生物化学、临床化学和其他方面得到广泛应用。近年关于微量铜的催化分析作了不少研究。其中有:Cu(Ⅱ)对Fe(Ⅲ)-硫脲反应或Fe(Ⅲ)-甲基硫脲反应,Cu(Ⅱ)对过氧化氢氧化氢醒或氧化靛胭脂以及Cu(Ⅱ)对Fe(CN)_6~(3-)-CN~-氧化还原反应的催化作用等。在多数情况下,干扰(如Hg(Ⅱ))难以排除,有的终点观测困难。本文提出的方法是根据Cu(Ⅱ)对反应的催化作用。为了能准确观测反应终点,我们在Fe~(3+)-S_2O_3~(2-)体系     

金属离子在液相氧化中的催化作用——Ⅷ.在丙酸氧化反应中Mn(Ⅲ)-Co(Ⅲ)催化体系不同离子的功能

本文仔细地研究了Mn(Ⅲ)-Co(Ⅲ)催化体系中不同离子在丙酸氧化中的功能:Mn(Ⅲ)离子首先与丙酸作用并被还原成Mn(Ⅱ)离子;Co(Ⅲ)离子可在反应体系中将Mn(Ⅱ)再氧化,而还原了的Co(Ⅱ)离子可为氧再生.这样建立起的氧化还原体系形成了催化循环.     

人工神经网络阻抑动力学光度法同时测定邻苯二酚和间苯二胺

在硫酸性介质中,Fe(Ⅲ)能够催化H2O2氧化中性红褪色反应,邻苯二酚和间苯二胺都能阻抑该催化氧化褪色反应的速度,研究发现：两者对Fe(Ⅲ)催化H2O2氧化中性红褪色反应阻抑作用不具有加和性,根据这一现象,用人工神经网络处理非线性体系的优势进行数据处理,从而建立了一种新的测定邻苯二酚和间苯二胺混合物的人工神经网络阻抑动力学光度法。对5组混合样品进行测定,回收率均在95%-105%之间。     

人工神经网络阻抑动力学光度法同时测定对苯二胺和间苯二胺

在硫酸性介质中,Fe(Ⅲ)能够催化H2O2氧化甲基红褪色反应,对苯二胺和间苯二胺都能阻抑该催化氧化褪色反应的速度,两者对Fe(Ⅲ)催化H2O2氧化甲基红褪色反应阻抑作用不具有加和性,根据这一现象,用人工神经网络处理非线性体系的优势进行数据处理,从而建立了一种新的测定对苯二胺和间苯二胺混合物的人工神经网络阻抑动力学光度法。对6组混合样品进行测定,回收率均在95%～105%之间。该方法运用于实验室水样的分析。     

《分析科学学报》第20卷总目次

研　究　报　告NDA柱前衍生毛细管电泳高灵敏安培检测组胺张丽瑶 ,黄卫华 ,王宗礼 ,程介克　 1(1)…………………………………铝对多巴胺和左旋多巴氧化的化学催化作用的电化学和光谱学研究章福平 ,毕树平 ,刘　剑 ,顾晓东 ,马鹏举 ,朱　杰　 1(5 )………………………………………………………………………冠醚壳聚糖多孔微球选择性富集 石墨炉原子吸收法测定雨水中痕量铅的研究陈水平 ,汪玉庭　 1(9)…………………色谱法测定手性四面体金属簇合物对映体过量值韩小茜 ,祝馨怡 ,张维强 ,李文智 ,李永民 ,陈立仁　 1(13)………………聚N …     

萃取动力学光度法测定活化剂铝——铝(Ⅲ)-过氧化氢-铜(Ⅱ)-邻氨基酚/氯仿体系

研究了在pH 5.5的弱酸性介质中, 利用Al(Ⅲ)对Cu(Ⅱ)催化H2O2氧化邻氨基酚显色的指示反应的活化作用.用萃取平衡控制反应时间、水相中邻氨基酚的浓度和反应进行的程度.通过在424 nm下测量有机相的吸光度,建立了萃取催化光度法测定活化剂铝的新方法.方法的线性范围为0.004～0.25 mg/L,检出限为1.6×10 -6 g/L.用于水样和茶叶中铝含量的测定,结果满意.     

催化氧化靛蓝胭脂红褪色反应动力学测定痕量铝(Ⅲ)的研究

在H2SOr介质中,痕量铝（Ⅲ）能灵敏地催化KBrO3氧化靛蓝胭脂红使其褪色,据此,建立了测定痕量铝（Ⅲ）的催化动力学新方法。研究了该催化褪色反应的最佳动力学条件并求得有关参数。方法的检出限为1．13ng／mL,线性范围为0．004～0．2μg／mL,将其用于水样（湖水、池塘水、自来水）中痕量铝（Ⅲ）的测定,获得了满意的结果。     

纳米金/石墨烯修饰电极的制备及其对多巴胺的测定

利用电化学还原方法制备纳米金/石墨烯修饰玻碳电极,研究了多巴胺(DA)在该修饰电极上的电化学行为,建立了电化学测定多巴胺的新方法。结果表明,在磷酸盐缓冲溶液中,此修饰电极对多巴胺的电化学响应具有很好的催化作用。利用差示脉冲伏安技术对多巴胺的电化学氧化进行定量分析,多巴胺的氧化峰电流与其浓度在1.0×10-7～1.0×10-5mol/L范围内呈良好的线性关系,检测限低至4.0×10-8mol/L。该修饰电极适于多巴胺的分析检测。     

锰(Ⅲ)Corrole配合物催化DNA氧化断裂

报道了这类单羟基Corrole锰(Ⅲ)配合物对DNA的催化氧化断裂作用.     

催化动力学荧光法测定痕量铝

研究了新型荧光试剂3-(4′-碘基苯基)-5-(2′-羧基苯偶氮)若丹宁的荧光性能。实验发现,在pH 5.2的邻苯二甲酸氢钾-氢氧化钠缓冲溶液中,痕量铝(Ⅲ)对H2O2氧化3-(4′-碘基苯基)-5-(2′-羧基苯偶氮)若丹宁具有强烈的催化作用,据此建立了催化动力学荧光法测定痕量铝(Ⅲ)的新方法。本法检出限为6.46×10-9g.mL-1,线性范围为0~0.015μg.mL-1。方法用于发酵粉和沸水中铝含量的测定,结果满意。     

Studies on the chemical syntheses and on the characteristics of polyaniline derivatives

Syntheses of parent polyaniline and methyl, methoxy, and ethoxy ortho-substituted polyanilines were performed using the conventional chemical methodology and monitored using the new open-circuit-potential (V_oc) profile technique. The intermediate pernigraniline oxidation state was identified and isolated at the V_oc maximum (A) during the conventional chemical synthesis of poly(o-methoxyaniline) in the emeraldine oxidation state. The introduction of the substituent on the aniline ring leads to longer polymerization times and lower V_oc values. Syntheses in the presence of two different monomers in solution were also investigated and showed preferential polymerization of the monomer with the lowest V_oc potential. All polymers produced were characterized by elemental analysis, gel permeation chromatography, UV-VIS spectroscopy, and cyclic voltammetry. The influence of the substituent on the V_oc profile and on the polymer characteristics are rationalized in terms of steric and electronic effects. © 1995 John Wiley & Sons, Inc.     

Study on the stability of the serotonin and on the determination of its acidity constants

The present work aimed at describing the spectral behaviour of the serotonin and to evaluate its acidity constants using three different methods, using two spectrophotometry titrations and a third method that involved point-by-point analysis, which permitted to monitor closely and determine the evolution of the serotonin species in solution as a function of time. The three methods allowed estimation of three acidity constants associated to the same number of functional groups that form part of the molecule. The results given by the point-by-point analysis were: log(beta1) = 24.95 +/- 0.12; log(beta2) = 20.20 +/- 0.10; log(beta3) = 10.89 +/- 0.018.     

Effect of ortho-Substituents on the Free-Radical Polymerization of N-Phenylmethacrylamides and on the Thermal Stability of the Polymers

Ceiling temperatures (T_c) and reactivities of N-phenylmethacrylamide (PMAm) and o-substituted PMAm's in free-radical polymerization and the thermal stability of the polymers obtained were investigated. Although PMAm and o-substituted analogs gave the same T_c, 123°C at 0.64 mol/L in N,N-dimethylformamide, that of 2,6-dimethyl-PMAm was found to be as low as 65°C. These findings are interpreted in terms of steric hindrance as a consequence of the bulkiness of the 2- and 6-substituents and of the rigid and planar structure expected for the polymers. In copolymerization with styrene, the o-monosubstituted PMAm's were estimated to be more reactive than PMAm by a factor of about 3 except for o-phenyl-PMAm. The enhanced reactivity of the PMAm with a relatively small o-substituent is explained by ground-state strain of the monomer tending toward a planar structure. 2,6-Dimethyl-PMAm and o-phenyl-PMAm showed lower and slightly higher reactivities than PMAm, respectively, probably due to the blocking effect of these substituents against the approaching polymer radical. Enhancement of thermal degradation owing to the substitution was confirmed by means of thermogravimetric analyses of the polymers. The polymers from the 2,6-dimethyl-substituted and the o-monosubstituted PMAm' exhibited similar maximum-degradation-rate temperatures.     

线粒体和亚线粒体体外代谢及漆酶影响的微量热研究

首次将微量热用于亚细胞层次的研究，测定了鲤鱼肝脏线粒体和亚线粒体代谢的热谱及其漆树漆酶的影响，并用ＭＴＤ方程和演化计算技术对它们的代谢热动力学参数进行了全局优化。     

Influence of phenylenediamine additions on the morphology and on the catalytic effect of polyaniline

The influence of para‐, ortho‐, and meta‐phenylenediamine (p‐, o‐, and m‐PDA) additions on the electrochemical synthesis of polyaniline has been investigated by the use of cyclic voltametry. It has been found that small additions (1 and 5 mmol L^?1) of PDA monomers influence significantly the polymerization rate. Whereas p‐PDA increases the polymerization rate, the addition of o‐ or m‐PDA slows it down. Therefore, a different number of potential cycling is necessary to obtain similar thickness of layers. The layers exhibit very different morphology, which changes from “spaghetti‐like” for polyaniline to “sponge‐like” for p‐PDA, to “pebble‐like” for o‐PDA and to “cauliflower‐like” for m‐PDA additions, respectively. The catalytic effect of the synthesized polymer layers has been tested. It has been found that all the layers exhibit catalytic effect in lowering the redox potential of hydroquinone/quinone tested reaction, but the rate of the electrocatalytic reaction varies depending on the PDA monomer added. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1599–1608, 2004     

Study on the stability of noradrenaline and on the determination of its acidity constants

Noradrenaline is a catecholamine which has been largely recognised to play a very important role in biological systems. In view of the neurotransmitter's alleged importance, this work aimed at showing the influence of time on its spectral behaviour using different analytical methods and determining its acidity constants through spectrophotometric titration and by the so-called point-by-point analysis, where the samples are freshly prepared for each pH value investigated at the instant required. Because the catecholamines are light-sensitive and likely to react with the oxygen in the surrounding air, both methods used preclude its incidence onto the samples being analysed under the presence of a nitrogen atmosphere maintained over the solutions. The constants obtained through point-by-point analysis were log beta1 = 30.71+/-0.16, log beta2 = 22.00+/-0.15 and log beta3 = 11.69+/-0.16.     

Reflections on the mechanism of the Barton-McCombie Deoxygenation and on its consequences2

The Barton-McCombie deoxygenation is a landmark reaction in organic chemistry. Its efficiency in generating carbon radicals from alcohols is unmatched, despite the passage of more than 40 years since its discovery. Its mechanism, far from being straightforward, is in fact quite subtle and conceptually part of a much larger family of very powerful thiocarbonyl controlled radical reactions. This general mechanistic manifold encompasses the degenerate transfer of xanthates and related thiocarbonylthio congeners, a process that also subtends the now popular RAFT/MADIX polymerization technology, the remarkably versatile Barton decarboxylation via thiohydroxamate esters, the generation of nitrogen-centered radicals from oxime xanthates and thiosemicarbazones and thiosemicarbazides, and certainly other transformations that will emerge in the coming years. The present overview retraces the history of the Barton-McCombie reaction, the evolution of the mechanistic aspects and the resulting consequences in terms of new transformations and synthetic applications.     

Influence of the heating rate on the temperature profiles and on the conversion rate of powdery cellulose and pine sawdust

An experimental study of the thermal decomposition of powdered cellulose and pine sawdust has been performed. The influence of the heating rate on the temperature profiles in the sample and on the solid conversion rate has been studied. A mathematical model without adjustable parameters has been used to calculate the temperature at different points in the solid bed and the average total solid conversion. The experimental results have been compared with those calculated by the model. A good agreement has been obtained for sawdust. Some differences are observed for cellulose at high heating rates, and the influence of the thermal conductivity and the reaction heat on the results has been analysed.