微波消解–电感耦合等离子体质谱法测定铀合金中铌、钼、锆

建立微波消解–电感耦合等离子体质谱法测定铀合金中铌、钼、锆。铀铌钼锆合金样品经8 mL HNO_3 (1+1)和2 mL HF微波消解并稀释处理后,利用电感耦合等离子体质谱法测定合金样品中铌、钼、锆含量,研究了铀浓度在0～30 μg/L时对铌、钼、锆元素直接测定的影响。铌、钼、锆的质量浓度在各自的范围内与其质谱响应值线性关系良好,相关系数大于0.999。铌、钼、锆的加标回收率为96.10%～105.00%,测定结果的标准偏差为0.74%～2.71%(n=6)。该方法流程简单,无需分离基体元素,可实现铀合金中铌、钼、锆元素的快速测定。     

电感耦合等离子体原子发射光谱法测定核级锆合金中铁、镍、铌、锡

采用基体匹配法,建立了电感耦合等离子体原子发射光谱测定锆合金中铁、镍、铌、锡4种常量元素的分析方法。通过用高纯海绵锆进行基体匹配和样品最佳溶解试验,准确测定了核级锆合金中常量元素铁、镍、铌、锡,两个元素含量不同样品的加标回收率分别为98.5%～99.5%和102%～104%,相对标准偏差均小于2%(n=10),满足西屋认证标准要求。铁、镍质量浓度在0～10 mg/L,铌、锡质量浓度在0～100 mg/L内线性良好,相关系数均为0.999 9。铁、镍、铌、锡的检出限分别为2.29、1.21、1.83、58.7μg/g,测量下限分别为7.62、4.04、6.11、196μg/g。     

氯代磺酚 S 光度法测定矿石中锆(铪)

我们在试验氯代磺酚S光度法测定铌的条件时,锆(铪)有正干扰。因此,我们探讨了用该试剂测定锆(铪)的适宜条件、干扰离子及消除方法。进而拟定了测定矿石中锆(铪)的光度法。本法的优点是选择性较好、灵敏度较高,可在常温下显色。能允许较大量钍、铀、稀土和钛的存在。当同时存在铌时,     

高分辨率分光系统-连续光源原子吸收光谱法测定铀铌铅矿重选流程样品中铅的含量北大核心CSCD

采用盐酸(15mL)-硝酸(5mL)-氢氟酸(10mL)-高氯酸(2mL)体系溶解铀铌铅矿样品(0.030 0～0.200 0g),盐酸(1+9)溶液作为分散介质,选择Pb 283.306nm作为分析谱线,提出了高分辨率分光系统-连续光源原子吸收光谱法(HR-CS AAS)测定铀铌铅矿重选流程样品中铅的方法。结果表明:检出限(3s)为0.021mg·L-1。按标准加入法对铀铌铅矿样品中的铅进行回收试验,回收率为97.8%～103%,测定值的相对标准偏差(n=9)均小于5.0%,满足国家地质矿产行业标准DZ/T 0130-2006的要求。     

氯化型N235-苯-盐酸混合体系萃取铀(Ⅵ)-偶氮氯膦Ⅲ-N235三元离子缔合物光度法测定微量铀

利用溶剂萃取,使铀同干扰离子分离,可提高测定铀的选择性。但是往往稀土、钍、钙、钒、铌、钽、锆、铪及钛等仍有严重干扰。T(?)Yamamoto等报导了用三正辛胺-苯-乙醇-盐酸体系萃取铀(Ⅵ),以偶氮氯膦Ⅲ(CPAⅢ)作显示剂测定海水中微量铀。我们在此基础上研究了国产N235(叔胺类萃取剂)-苯-盐酸体系中铀的萃取。发现在4N以上盐酸介质中能定量萃取铀,在4.5～6.5N盐酸介质中,能使铀有效地同稀土、钍、锆、铌、钽及钛等离子分离。然后在氯化型N235-苯-乙醇-盐酸体系中,加入CPAⅢ形成蓝绿色的铀(Ⅵ)-CPAⅢ-N235     

标准加入法测定铀铌陶瓷材料中微量钽的研究

采用标准加入-ICP/AES法对铀铌陶瓷材料中微量钽的测定进行了研究.当试液中铌的质量浓度为1.0 mg/mL,钽的测定范围是50～500 μg/g,回收率为106%～99.6%,相对标准偏差（RSD）为6.6%～3.1%.     

铀铌合金中微量碳的测定

研究了用碳硫分析仪测定铀铌合金中的微量碳的影响因素。钨粒加铁片是铀铌中碳释放的良好助熔剂;用硝酸（1＋1）可有效去除铀铌试样表面上的吸附碳;在空气条件下清洗铀铌试样,其表面对碳的吸附不显著;不同的试样加工方式对铀铌试样中碳量的测定有一定的影响。本方法适用于碳量为40－1000μg/g的铀铌试样中碳的测定。相对标准偏差10％。     

电感耦合等离子体原子发射光谱法测定锆铀合金中微量铪

应用电感耦合等离子体原子发射光谱法(ICP-AES),采用标准加入法对锆铀合金中微量铪进行了测定.当锆的共存量为8 g·L-1时,铪的测定范围是50～400 μg·g-1.在Zr-U合金的基础上分别加入铪50μg·g-1及400 μg·g-1作回收试验,测得回收率依次为106%及101%,相应的相对标准偏差为5.8%和3.7%.     

不同类型协萃剂与PMBP协同萃取铀和稀土元素的研究及其应用

PMBP(1-苯基3-甲基-4-苯甲酰基吡唑酮-5)是萃取稀土、钛、锆、铀和钍等金属离子的优良萃取剂,国内外已有报导。为使PMBP能直接从含有易水解的铌、钽、钛和锆等溶液中萃取分离出稀土、铀和钍,我们曾研究在酒石酸等络合剂存在下用PMBP萃取铌、钽、钛、锆、钨、钼、铁、铀和稀土     

电感耦合等离子体原子发射光谱法测定核纯海绵锆中微量铪

应用标准加入-电感耦合等离子体原子发射光谱法(ICP-AES)对核纯海绵锆中微量铪进行测定.当试样中锆的质量浓度为10 g·L-1时,铪的测定范围为50～400μg·g-1,回收率为103%～110%,相对标准偏差(n=6)为4.2%～6.5%.     

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.