酪氨酸作试剂荧光光度法测定亚硝酸根

亚硝酸盐广泛存在于土壤、食品及天然水中 ,是水体中氮循环的重要中间物。亚硝酸盐可引起急性中毒 ,还可以与仲胺和酰胺等结合成致癌的亚硝胺化合物 ,是造成环境污染的主要原因之一。因此 ,亚硝酸盐的含量是环境监测和食品分析的重要指标。荧光法测定亚硝酸根常用的试剂是 2 ,3 二氨基萘[1] ,但需用有机溶剂萃取 ,操作繁琐 ,而且由于试剂本身有毒 ,易造成二次污染。近年来有人报道了荧光猝灭法测定亚硝酸根[2 ,3] 。本文以亚硝酸根与酪氨酸反应产物在碱性介质中呈现强的荧光 ,其激发波长和发射波长分别为 31 8.0ｎｍ和 398.4ｎｍ ,建立了水样中亚硝酸根的荧光测定法。考察了反应条件对荧光强度的影响 ,ＮＯ2-在 1 0～ 2 0 0μｇ Ｌ范围内与△Ｆ成线性关系 ,除铁外常见的共存离子不干扰其测定 ,本法已用于水样中ＮＯ2-的测定。1　实验部分1 .1　主要仪器及试剂ＲＦ 5 0 0 0荧光分光光度计 (日本岛津 )。ＮＯ2-标准储备液 :1 .0ｇ Ｌ ,使用前稀释为1 0 0ｍｇ Ｌ工作液 ;酪氨酸 (生化试剂 ) :5 .0ｇ Ｌ ,称取 0 .5ｇ酪氨酸于烧杯中先加入少量水 ,再加入 2ｍＬ 5ｍｏ...

焙烧温度对CeO2改性Pd/Al2O3甲醇分解催化剂性能的影响

中国科学院山西煤炭化学研究所

Preparation and characterization of ordered yttrium arachidate multilayer

The behavior of arachidic acid on the surface of YCI3 aqueous subphase was studied by LB and Brewster angle microscopy techniques. The results showed that the pre-compressing time and the pH of the subphase played an important role in the forming of the monolayer. The monolayer on the subphase surface was irreversible. If the monolayer was compressed into wrinkles, the monolayer could not become uniform again. The optimum transferring conditions were selected and the ordered yttrium arachidate multilayer with a long spacing of 4.96 nm and a tilt angle of 28.5degrees of the three alkyl chains from the surface normal was fabricated and characterized.

后过渡金属烯烃聚合催化剂研究进展

烯烃在催化剂的作用下形成聚合物 .改变催化剂的结构 ,可以得到特定分子结构和特定性能的聚烯烃产物 ,因而催化剂的研究开发是聚烯烃升级换代的核心 .烯烃聚合催化剂的发展大致经历了 3个阶段 :Ziegler- Natta催化剂 -茂金属催化剂 -后过渡金属催化剂 .Ziegler[1]和 Natta[2 ]发现了用于各种 α-烯烃聚合的催化剂 ,并已作为主导技术应用于工业化大生产 . 2 0世纪 80年代初 ,Kaminsky等 [3～ 5] 发现 ,二氯二茂锆与烷基铝氧烷组成的体系(茂金属催化剂 )是一种高催化活性、高立体选择性、长寿命的催化剂 .茂金属催化剂的设计、合成和应用 ,促进了聚烯烃化学的革命 ,目前对于茂金属用于烯烃聚合 ,正从基础研究向实用化、工业化阶段发展 .后过渡金属催化剂是指后过渡金属镍、钯、铁、钴等的配位化合物 .由于后过渡金属有较强的β- H消除倾向 ,因而大多数后过渡金属催化剂只适用于烯烃二聚或齐聚 ,得不到高分子量的烯烃聚合物 [6～ 8] .人们曾尝试用后过渡金属催化烯烃聚合 ,但没有表现出如 和 族体系那样高的活性 ,它们主要用于烯烃的齐聚和双烯烃的聚合反应 ,最近几年来这...

组合化学在功能材料合成方面的应用

组合化学方法是当今材料科学和化学领域的研究热点.组合化学方法首先在新药的合成领域得到应用,很快就以其合成周期短、合成的样品数量大、节约经费等诸多优点而拓展到功能材料的合成等其它领域.组合化学的方法有许多种,按照反应相的不同可以分为液相中的组合合成法和固相中的组合合成法,固相组合合成又可以根据所选用的掩模方式的不同而分为二分阴影掩模法、四分阴影掩模法、可移动百叶窗式掩模法等几种,可以根据材料合成的实际需求加以选择.

Tuning the aggregation of polyimide thin films by modification of their molecular interactions

Thin films of an organo-soluble polyimide based on 1,4-(3,4-dicarboxyphenoxy)benzene dianhydride (HQDPA) and 2,2'-dimethyl-4,4'-methylene dianiline (DMMDA) have been studied. A prism coupler was used to measure the refractive indices. The average refractive indices of thin films prepared by annealing at different temperatures and times were chosen to characterize the condensation states of thin films. Thin films annealed at 200 degrees C show irreversible changes in physical properties, eg solubility. FTIR spectroscopy showed that the chain structures of the above thin films remained unchanged. It is proposed that specific molecular interactions induce the irreversible changes revealed by fluorescence spectroscopy. (C) 2000 Society of Chemical Industry.

Probability distribution of the four-phase structure invariants of isomorphously related structure factors and its applications

The probability distribution of the four-phase structure invariants (4PSIs) involving four pairs of structure factors is derived by integrating the direct methods with isomorphous replacement (IR). A simple expression of the reliability parameter for 16 types of invariant is given in the case of a native protein and a heavy-atom derivative. Test calculations on a protein and its heavy-atom derivative using experimental diffraction data show that the reliability for 4PSI estimates is comparable with that for the three-phase structure invariants (3PSIs), and that a large-modulus invariants method can be used to improve the accuracy.

Chemical environment code and measure of molecular similarity

A new scheme for the code of chemical environments of compounds is described in this paper, and three molecular similarity methods have been used to select nearest neighbors from four different types of probe compounds. One of the methods is based on the C-13 NMR spectra. The second method is based on the code of chemical environments and molecular topological index A(x). The third approach, i.e. the Tanimoto coefficient, is also based on the code of chemical environments, but not to use the topological index. Five nearest neighbors for each probe compound using these three molecular similarity methods were determined and taken from the database of 7309 structures. The results indicate that the scheme of the chemical environment code and the method for similarity measure of intermolecules suggested in this study are reasonable. (C) 1998 Published by Elsevier Science Ltd. All rights reserved.

Bilayer formation of two chiral ferroelectric liquid crystal molecules at the air-water interface

The bilayer formation behavior of two chiral ferroelectric liquid crystal molecules at the air-water interface was studied.

A study of ion kinetic energy spectrometry of o(-), m(-), and p(-) diol benzene doubly charged ions and singly charged ions in gas phase

With Mass Analyzed Ion Kinetic Energy Spectrometry (MIKES), Collisional Induced Dissociation(CID), and Electron Capture Induced Decomposition(ECID) technigues, the doubly charged ions and singly charged ions from o(-), m(-), and p(-) diol benzene in the EI source have been studied. In terms of the values of the kinetic energy releases(T) of the charge separation reactions of the doubly charged ions and the estimated intercharge distances(R) of the exploding doubly charged ions the transition structures were proposed. Some structural information about the transition states was also obtained. It is of interest that the MIKES/CID spectra of singly charged ions [C6H6O2](+) from the three isomers are of significant differences.

苯二酚异构体双电荷离子和单电荷离子的动能谱研究

本文利用质量分析离子动能谱(MIKES)、碰撞诱导解离(CID)技术和电子捕获诱导解离(ECID)技术,研究了邻、间、对苯二酚分子在电子轰击质谱(EIMS)中产生的双电荷离子[C_6H_6O_2]~(2+),[C_6H_4O]~(2+)和单电荷离子[C_6H_6O_2]~+.根据测定的电荷分离反应动能释放值T和由此计算出的两电荷间距R,推测出过渡态的结构.有趣的是,可利用单电荷离子[C_6H_6O_2]~(+)的MIKES/CID谱区分苯二酚异构体.

稀土富勒烯提取液的激光解吸飞行时间质谱研究

采用激光解吸飞行时间质谱对含镧(La)、铈(Ce)、镨(Pr)、钕(Nd)、钐(Sm)、铕(Eu)、钆(Gd).铽(Tb)、镝(Dy)、钬(Ho)、铒(Er)、铥(Tm)、镱(Yb)等13种稀土富勒烯的提取液进行了研究.考察了正负谱、激光强度、底物以及质量歧视对分析结果的影响,并由此确定了最佳分析条件.结果表明,提取液中除了空心富勒烯外,还存在较多量的稀土富勒烯.通过对它们谱峰相对强度之间的比较,探讨了不同稀土元素嵌入富勒烯球笼的结构稳定性及溶解性能的差别以及产生这种差别的可能原因.

非均匀化稀土6063变形铝合金电解着色的研究

非均匀化稀土６０６３变形铝合金电解着色的研究王冰（中国科学院长春应用化学研究所，长春１３００２２）关键词：稀土均匀化６０６３变形铝合金电解着色１前言近年来关于稀土铝合金中细化组织、提高机械性能和加工性能的研究引起了人们广泛的关注。稀土在铝合金中的良好...

高温高压下立方氮化硼晶体的生长机制

在４．５～５．０ＧＰａ，１５００～１８００℃范围内，对在Ｌｉ基复合氮化物或氮硼化物的催化体系中以及其中添加Ｌｉ８ＳｉＮ４后合成ｃＢＮ进行了研究，探讨了ｃＢＮ晶体的表面构造和生长机制，研究了由六方氨化硼向立方氮化硼转变过程中硅的存在行为．本实验中合成的立方氮化硼为具有光泽的棕色透明单晶．

分子量对酞侧基聚芳醚酮熔体流变行为的影响

用锥权流变仪及ＤＳＣ的方法研究了５种不同分子量的酞侧基聚芳醚酮（ＰＥＫ—Ｃ）在低剪切速率区（１０－２－１０ｓ－１）的流变行为及其分子量与玻璃化转变温度（Ｔｇ）的关系．结果表明，样品的粘流活化能随分子量的增加而增大，Ｔｇ随分子量的变化是二个线性区，其交点值与所求的样品的临界分子量（Ｍｃ）值相对应．利用测得的零剪切粘度值（η０）首次求得了ＰＥＫ—Ｃ的临界分子量（Ｍｃ）值．同时也讨论了Ｍｃ与温度及η０和Ｔｇ与分子量的关系．