微波消解——冷原子只收法定量测定人参中汞的研究

应用微波消解仪的原子吸收光谱仪,采用氢化物－冷原子吸收光谱法对人参中的汞的定量测定方法进行了研究。对微波消解仪的消解条件、氢化物－冷原子吸收方法的测定条件进行了探讨。在本法选择的条件下,回收率为90．98％－108．96％,相对标准偏差为8．04％－15．77％。与国家标准方法的对比实验证明,两者无显著差异。     

控温消解-冷原子吸收方法测定水果蔬菜中微量汞

应用程序控温－湿法消解－氢化物发生－冷原子吸收光谱法对水果蔬菜中的汞的定量方法进行了研究和探讨。对程序控温消解仪的消解条件、氢化物－冷原子吸收的测定条件进行了探讨。在本文选择的条件下，回收率为86．99％－108．00％，相对偏差为4．6％－10．8％。该方法与国家标准方法相对照，无明显差异。     

微波消解-冷原子吸收法定量测定人参中汞的研究

应用微波消解仪和原子吸收光谱仪 ,采用氢化物 冷原子吸收光谱法对人参中的汞的定量测定方法进行了研究。对微波消解仪的消解条件、氢化物 冷原子吸收方法的测定条件进行了探讨。在本法选择的条件下 ,回收率为 90 98%～ 1 0 8 96 % ,相对标准偏差为 8 0 4 %～ 1 5 77%。与国家标准方法的对比实验证明 ,两者无显著差异。     

微波消解—原子荧光光谱法定量测定山梨糖醇液中的砷

应用微波消解技术和原子荧光光谱仪以氢化物发生原子荧光光谱法测定了山梨糖醇液中砷的研究。对微波消解条件以及氢化物发生条件进行了探讨。在选定的最佳条件下方法的检出限为0．22ng/mL,线性范围为0－80ng/mL。10次测定的相对标准偏差为0．49％－2．16％,回收率为94．8％－102．2％。该结果与国际推荐的湿法消解分析结果相对照,无显著性差异。     

化妆品中Hg、As和Pb的微波消解—氢化物发生ICP—AES法测定

采用微波消解－氢化物发生ICP－AES法测定化妆品中Hg、As和Pb,加入L－半胱氨酸消除了过渡金属离子的干扰,考察了微波消解、氢化物发生的最佳条件。建立的方法简便快速,测定Hg、As和Pb的RSD分别为0．59％、1．2％、2．4％（n=10),样品加标回收率分别为98．5％、99．3％和100．1％。该法已应用于化妆品的常规测定,得到满意的结果。     

微波消解-火焰原子吸收法测定土壤中的钴

建立了微波消解一火焰原子吸收法测定土壤中钴的方法：用微波消解土壤、电热板加热驱酸的方法对土壤样品进行前处理,优化了微波消解条件。方法的加标回收率为93．0％～106．0％,检出限为3．0μg/g,测定结果的相对标准偏差为2．1％～4．9％（n=6）。     

微波消解-FAAS法测定元胡中的镁

采用微波消解法溶解样品,火焰原子吸收分光光度法（FAAS）测定了元胡中的镁,探讨了微波消解预处理的条件,优化了FAAS测定参数。结果表明,该法具有良好的准确度和精密度,加标回收率在93．25％-96．25％范围内,相对标准偏差（RSD）1．16％,线性范围在0．5～3．5μg·mL^-1之间,为研究金属元素在元胡中的功能提供了有用的数据。     

微波消解-冷原子吸收光谱法测定烤鳗中的总汞

本文采用密封微波消解技术处理样品,对烤鳗样品一次性进行微波消化,然后用氢化物发生-冷原子吸收光谱法测定烤鳗中的总汞,回收率均在80％～95％之间。方法简便、快速、准确,用于烤鳗样品中汞含量的测定,结果满意。     

微波消解-火焰原子吸收法测定猪肝脏中的铅

采用微波消解—火焰原子吸收法对猪肝脏(鲜)中的痕量铅进行了测定,建立了一种微波消解样品、火焰原子吸收法测定猪肝脏(鲜)中痕量铅含量的方法.研究结果表明,在取样量为0.8g左右、HNO3(65％)∶H2O2(30％)=1∶1(体积比)、中等微波功率消解3 min的条件下,检测到猪肝脏中铅的含量为0.173 μ g/g.该...     

微波消解样品-冷原子吸收光谱法测定鱼粉中微量汞

以微波溶样技术消解样品,采用正交试验设计优化冷原子吸收光谱法测定汞的试验条件,并对微波消解条件和共存离子的干扰进行了试验。试验表明：汞含量在30μg·L^-1范围内服从比耳定律,方法的检出限为0．13μg·L^-1,相对标准偏差为2．6％,回收率为97．6％～106．8％。     

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.     

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.     

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.     

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.