涂钼石墨管石墨炉原子吸收法测定镓,铟和铊热蒸发行为的探讨

本文从热力学和化学动力学的角度对消除干扰及提高吸收灵敏度的机理进行了探讨，认为在涂钼石墨管中，镓，铟和铊主要以Ｇａ２Ｏ，Ｔｌ２Ｏ和ＩｎＯｘ形式与ＭｏＯ３形成稳定的烧结物，使初始挥发温度大大提高，减少了干燥，灰化前处理过程被测物的分子挥发逸失，由于钼元素参与镓，铟和铊的原子化反应，从而改变了原子化，提高了原子化效率。     

涂钼石墨管石墨炉原子吸收法测定镓、铟和铊热蒸发行为的探讨

本文从热力学和化学动力学的角度对消除干扰及提高吸收灵敏度的机理进行了探讨。认为在涂钼石墨管中,镓、铟和铊主要以Ga_2O、Tl_2O和InOx形式与MoO_3形成稳定的烧结物,使初始挥发温度大大提高,减少了干燥、灰化前处理过程被测物的分子挥发逸失。由于钼元素参与镓、铟和铊的原子化反应,从而改变了原子化机理,提高了原子化效率。     

氢化物发生石墨炉原子吸收进展

在氢化物发生原子吸收光谱中,石英管是使用较为广泛的原子化器,但由于其气相干扰比较严重,石英管表面性质对分析灵敏度影响较大,因而又发展了石墨炉原子化器。自提出涂钯石墨管原位富集氢化物以后,氢化物发生石墨炉原子吸收受到人们的重视。现将氢化物发生石墨炉原于吸收的主要方法分述如下: 1 石墨炉在线原子化法 所谓石墨炉在线原子化法,是将生成的氢化物直接通入已经达到原子化温度的石墨管里的方法。氢化物可以从石墨炉内气路通入石墨管,也可以从石墨管进样孔进入石墨管。由于石墨炉原子化的温度较高,因而能大大减小可以形成氢化物元素的气相干扰。文献[1]比较了石英管和石墨管两种原子化器的抗干扰能力,其中有关砷和硒的干扰情况见表1。     

反应液温度对氢化物生成过程的影响及氢化物稳定性的考察

自1969年Holak把氢化物发生技术用于原子吸收光谱分析以来,在各个领域均已得到广泛应用。在此期间,一些工作者对影响氢化物生成的条件,原子化机理,干扰及其消除等方面做了研究,但有关反应液温度对氢化物生成过程的影响及氢化物稳定性方面的报导甚少。本文对此进行了系统考察,并对实验结果进行了探讨。实验 1.仪器与装置:岛津AA-610s原子吸收分光光度计;自制的手动注射式氢化物发生     

氢化物发生石墨炉原位富集直接测定高温镍基合金中碲

通过选择碲的氢化物发生条件，克服了高含量镍对碲的干扰，把氢化物富集在涂钯石墨管里，然后再原子化，成功地测定了高温镍基合金中碲。     

氢化物原子吸收机理的研究——Ⅱ.石英原子化器表面在原子化过程中的作用

本文研究了氢化物原子吸收中电热石英管原子化器表面在氢化物原子化中的作用,实验证实一些元素氢化物的原子化包含有表面过程,并不是单纯的气相原子化过程。     

氢化锗在电热石英管中的行为

氢化物原子吸收法已经得到广泛应用,但有关氢化物原子化机理一直存在争议,且多集中在AsH_3和seH_2方面,本文对GeH_4在电热石英管中的行为进行了研究。     

探针原子化-石墨炉原子吸收法直接测定地质样品中铟的研究

本文应用自动采样探针原子化-石墨炉原子吸收法测定地质样品中的铟,对探针原子化的实验条件,精密度和检出限,以及原子化机理进行了研究,并比较了几个常见元素在管壁法和探针法中的干扰效应。发现探针法抗干扰能力优于管壁法,基本上消除了基体干扰,不用灰化阶段,直接进行测定。探针法灵敏度比管壁法有较大提高,精密度良好。     

H-3型半自动火焰原子吸收氢化物发生器——1.结构和以空气-乙炔火焰原子化的测定性能

自从1969年开始研究和应用氢化物-原子吸收法以来,出现了种种不同的氢化物发生器,近几年市售的和已发表的氢化物发生器向两方向发展,一是利用微处理机等新技术使操作全自动化的发生器,另一是手动或白动化程度较低、费用较少的发生器。我们设计的H-3型氢化物发生器属于后一类。各种氢化物-原子吸收装置所用原子化器可分为火焰与非火焰二类。对火焰原子化,往往选用火焰本     

连续氢化物发生—电加热石英管—原子吸收光谱法实验系统

报道了连续氢化物发生－电加热石英管原子吸收光谱法实验系统。并以铅烷（ＰｂＨ４）发生为代表对氢化物发生器构型，残留液体积、原子化温度、石英管电加热区域长度、载气流速、测量波长选择泵速、进样管长度等诸多影响因素作了试验。     

二氧化碳和丙烯直接合成甲基丙烯酸的NiPMo/TiO2催化剂的研究

用溶胶-凝胶法以磷钼酸(MPA)的镍盐溶液水解钛酸四丁酯制备了NiPMo/TiO2催化剂.使用ICP、 XRD、 TG-DTA、 IR、 TPD-MS和微反应技术研究了催化剂的化学组成、热稳定性、化学吸附性质和催化反应性能.杂多钼酸盐与TiO2通过O2-在TiO2表面发生了键合.在623 K下,杂多阴离子仍保持原有的Keggin结构.CO2在Lewis酸位Ni(Ⅱ)和Lewis碱位Ni-O-Mo的桥氧协同作用下生成CO2卧式吸附态Ni(Ⅱ)←O-(CO)←(O--Ni).丙烯有多种吸附态在催化剂上吸附.在563 K、 1 MPa和空速1500 h-1的反应条件下,丙烯的摩尔转化率为3.2%,产物MAA选择性为95%.     

Synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives

Different approaches for the synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives from simple amino acids have been investigated. A library of 33 precursors for the preparation of N-hydroxy pyrazinones was obtained in moderate to good yields.     

Toward new camptothecins. Part 6: Synthesis of crucial ketones and their use in Friedländer reaction

In the context of the preparation of camptothecin and luotonin A analogs, the synthesis of some key keto-precursors and their use in Friedländer condensation are described. This paper also focuses on the stability of these keto intermediates and emphasizes the major differences between indolizinones and pyrroloquinazolinones series. Noteworthy is also the report of some original structures isolated as by-products of some experiments.     

CoFe2O4自形成磁性液体场致结构化对磁化的影响

The Langevin paramagnetic theory can’t describe the relation between magnetization of ferrofluids and applied magnetic field. The structuralization of ferrofluids, which is considered the main influence factor of the magnetization, is regarded. The part of magnetization works is deposited when the structure is forming. This action influences the magnetization of ferrofluids directly or indirectly. On the base of the “compressing” model, the Langevin function that usually describes the magnetization of ferrofluid is modified, and a well-fitted curve is obtained. An equation of the relation between the equivalent volume fraction after being “compressed” and the intensity of magnetic field is discovered, which approximately describes the process of magnetization. The relation between the approximate initial susceptibility and the volume fraction can be obtained from modified formula.     

Highly regioselective Buchwald–Hartwig amination at C-2 of 2,4-dichloropyridine enabling a novel approach to 2,4-bisanilinopyridine (BAPyd) libraries

The highly regioselective Buchwald–Hartwig amination at C-2 of the cheap and readily accessible reagent, 2,4-dichloropyridine with a range of anilines and heterocyclic amines is described. This new methodology is robust and provides a facile access to 4-chloro-N-phenylpyridin-2-amines on 0.25 mol scale. These intermediates undergo a further Buchwald–Hartwig amination at higher temperature to enable rapid exploration of the chemical space at C-4 and to provide a library of 2,4-bisaminopyridines.     

KMnO4-mediated oxidative CN bond cleavage of tertiary amines: Synthesis of amides and sulfonamides

KMnO₄-mediated oxidative CN bond cleavage of tertiary amines producing secondary amine was introduced, which was trapped by electrophiles (acyl chloride and sulfonyl chloride) to form amides and sulfonamides. The reaction could take place at mild condition, tolerating a wide range of function groups and affording products in moderate to excellent yields.     

Chemistry of heterocyclic compounds at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences, over 50 years (Review)

The review contains a concise historical account and information on the most significant researches undertaken by the staff at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences on the Chemistry of Heterocyclic Compounds. Dedicated to Academician of the Russian Academy of Sciences B. A. Trofimov on his 70th jubilee. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1443–1502, October, 2008.     

Sulfur-directed metal-free and regiospecific methyl C(sp3)–H imidation of thioanisoles

Regiospecific and direct imidation of the methyl C(sp³)–H bond of thioanisoles is realized under mild and metal-free conditions with N-fluorobis(benzenesulfonyl)imide as an oxidant and nitrogen source. Proposed mechanism suggests that thionium ion intermediates and a Pummerer-type reaction are involved. The imidation has advantages such as high step-economy, excellent functionality tolerance, and regiospecificity, giving structurally diverse imidation products.     

A general and convenient synthesis of 4-(tosylmethyl)semicarbazones and their use in amidoalkylation of hydrogen,heteroatom, and carbon nucleophiles

A general synthesis of previously unknown semicarbazone-based α-amidoalkylating reagents, 4-(tosylmethyl)semicarbazones, has been developed. The synthesis involved three-component condensation of semicarbazones of aliphatic or aromatic aldehydes with the same or other aldehydes and p-toluenesulfinic acid. The scope and limitations of this reaction were investigated. The compounds obtained were demonstrated to be an efficient α-(4-semicarbazono)alkylating agents. They were reacted with H- (sodium borohydride), O- (sodium methylate), S- (sodium phenylthiolate), N- (pyrrolidine, sodium succinimide), P- (trialkyl phosphites), and C-nucleophiles (sodium diethyl malonate) to give the corresponding products of the tosyl group substitution, 4-substituted semicarbazones, including analogues of nitrofurazone. Among the prepared compounds tested in vitro for antibacterial and antifungal activity, three nitrofuryl-containing semicarbazones exhibited high biological activities with minimum inhibitory concentration (MIC) values of 8–32 μg/mL.     

Synthesis of novel chiral bidentate hydroxyalkyl-N-heterocyclic carbene ligands and their application in palladium-catalyzed Mizoroki–Heck couplings and asymmetric addition of diethylzinc to benzaldehyde

A small library of new chiral bidentate hydroxyalkyl-imidazolium salts 1 is conveniently synthesized on multi-gram scale from inexpensive and commercially available chiral pool amino acids. The corresponding carbenes, generated by deprotonation of imidazolium salts 1, in combination with palladium(II) chloride were tested in the Mizoroki–Heck coupling reaction. The most significant results in terms of yields and reactivities were achieved with low catalyst loading. The catalytic activities of these imidazolium salts were also investigated in the asymmetric addition of diethylzinc to benzaldehyde. The use of MgO nanoparticles as an additive in conjunction with these ligands played a crucial role in increasing the efficiency of these reactions.