火焰原子吸收光谱法测定碳酸钙试剂中痕量铅

分离和富集是痕量分析中的一个重要手段,以巯基为功能基团的巯基棉、巯基树脂等分离富集剂近十多年得到广泛应用,本文则根据巯基能定量吸附某些重金属离子而大量碱金屑、碱土金属离子不干扰其吸附的特点,采用近几年发展起来的巯基-活性炭新型富集剂(以下简称富集剂)为分离富集技术,建立了大量钙中痕量铅的测定方法,并测定了碳酸钙试剂中的痕量铅,其结果的准确度和精密度令人满意。     

萃取色层富集原子吸收光谱法测定环境水中痕量铜

利用固定有１－（２－吡啶偶氮）－２－萘酚（ＰＡＮ）的活性硅胶萃取色层法富集环境水中痕量铜,０．１ｍｏｌ．Ｌ＾－１盐酸－５０ｇ．Ｌ＾－１硫脲体系作为洗脱剂,火焰原子吸收史谱法测定。研究了富集剂的吸附容量,最佳吸附条件,洗脱条件,试验表明,该富集剂使用寿命长达１５次,富集倍数达２００倍。     

聚丙烯酰胺肟-羧酸螯合纤维对多种微量元素富集性能及机理的研究

近年来,利用巯基及它种螯合基纤维素富集测定多种微量元素的研究报导较多,但将螯合基团接在合成纤维上作为富集剂的报导尚少。我们曾用腈纶为原料合成聚丙烯酰胺肟-羧酸螯合纤维富集测定过数种微量元素。本文较系统地研究了该螯合纤维对30余种微量元素的定量富集酸度、吸附速度、洗脱酸度、饱和吸附量和共存离子的干扰,讨论了螯合纤维的稳定性、耐酸碱性、再生使用和富集机理,并进行了低浓度元素的富集和样品分析。实验表明,该螯合纤维是一种良好的高分子富集剂,它可以定量富集多种微量元素,具     

萃取色层富集原子吸收光谱法测定环境水中痕量铜

利用固定有双硫腙的活性硅胶萃取色层法富集环境水中痕量铜,0.1mol·L-1盐酸-50g·L-1硫脲作为洗脱剂,火焰原子吸收尤谱法测定。研究了富集剂的吸附容量,最佳吸附条件和洗脱条件。试验表明,该富集剂的使用寿命长远20次,富集倍数高达200倍;对于同浓度水样平行测定6次,其相对标准偏差为3.2％;应用于实际水样分析,加标回收率在95％～110％之间。     

原子吸收光度法测定水中六价铬的新探索

研究用巯基棉为吸附富集剂,定量测定水中六价铬的新方法。     

巯基活性碳富集剂对重金属离子的吸附特性

从热力学、动力学及XPS3个方面讨论了巯基活性碳富集剂对重金属离子的吸附机理。结果表明富集剂的吸附过程以化学吸附为主。外表面,内表面对Cu~(2+)的吸附率分别为19%,81%;Pb~(2+)为6%,94%,对Zn~(2+)为17%,83%,而吸附Cd~(2+)完全由内扩散所控制。被吸附的Cu~(2+)还将进一步还原为Cu~o。     

聚酰胺富集吸光光度法测定银

聚乙内酰胺作为Ａｇ的富集剂，从稀ＨＮＯ３溶液中富集Ａｇ具有吸附速度快，解脱容易，吸附容量大且可重复使用等优点。在选择条件下，最大吸附容量达５０ｍＬ／ｍｉｎ，并作１８种元素干扰实验确定允许量。     

聚酰胺作为金的新富集剂

聚酰胺作为金的富集剂,从稀王水或盐酸介质中富集微量金,具有吸附速度快、容易洗脱、吸收容量大等优点。在选择的色层条件下,除贵金属和铊(Ⅰ)外,普通金属离子不被吸附。实验表明,聚酰胺可用于分离、富集各类矿物中的微量金。     

用X射线光电子能谱(XPS)研究巯基棉对于水溶液中CH_3Hg~+和Hg~(2+),Se~(4+)和Se~(6+) 及Cr~(3+)和Cr~(6+)的吸附作用

巯基棉作为一种富集水溶液中重金属离子的吸附剂,已有文献记载。但将其作为一种吸附还原富集剂,报导还甚少。本文用XPS测定了已饱和吸附CH_3Hg~+和Hg~(2+),Se~(4+)和Se~(6+)及Cr~(8+)和Cr~(6+)的各种巯基棉。结果表明,巯基棉在吸附CH_3Hg~+和Hg~(2+)时仅起了一个吸附剂的作用,但在吸附Se~(4+)和Se~(6+)及Cr~(6+)时,除吸附外还产生了强还原作用,并能将前二者均还原为Se~0,后者还原为Cr~0。     

微型吸附树脂柱快速富集水中痕量有机物的研究

本文用GDX系列吸附树脂柱对水中痕量酚类和多环芳烃的富集作了研究。探讨了树脂极性、洗脱剂种类、水样酸度、离子强度、吸附与解吸速度等对回收率的影响。结果表明,极性化合物用GDX—502,非极性化合物用GDX—102为吸附剂,以甲醇或乙腈为洗脱剂能获满意的结果。本法适用于色谱法和比色法等的低浓度试样的富集。     

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%.     

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.     

Selective syntheses of 2H-1,3-oxazines and 1H-pyrrol-3(2H)-ones via temperature-dependent Rh(II)-carbenoid-mediated 2H-azirine-ring expansion

The Rh(II)-catalyzed reaction of 2-carbonyl-substituted 2H-azirines with ethyl 2-cyano-2-diazoacetate or 2-diazo-3,3,3-trifluoropropionate provides an easy access to 2H-1,3-oxazines and 1H-pyrrol-3(2H)-ones. These compounds can be selectively prepared from the same starting material using temperature as the only varied parameter. The 2-azabuta-1,3-diene intermediate, a common precursor for both heterocyclic products, isomerizes into 2H-1,3-oxazine under kinetic control, while 1H-pyrrol-3(2H)-one is the sole product of the reaction at elevated temperatures. According to DFT-calculations a one-atom oxazine ring contraction involving ring-opening to a 2-azabuta-1,3-diene intermediate, followed by a 1,5- and 1,2-prototropic shift leads to the consecutive formation of imidoylketene and azomethine ylide, which then further undergo cyclization to the pyrrole derivative.     

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.