钐同位素丰度的绝对测量

建立了钐同位素丰度高精度的质谱测量法。对样品形态选择、离子转换效率、离子传输效率和离子接收效率进行研究,消除了浓缩同位素测量时强峰拖尾对弱峰的干扰及同量异位素干扰。用已知化学纯度的^152Sm、^154Sm两种浓缩同位素,通过化学计量配制人工合成校正样品,测量质谱计的系统误差校正系数,对用该仪器测量的来自不同地域矿物和试剂样品中钐元素天然同位素的丰度比数据进行校正,准确求得钐同位素的丰度。     

电感耦合等离子体质谱法测定硼同位素丰度

以硼同位素标准物质NIST SRM 951配制标准溶液,在优化的仪器操作条件下对电感耦合等离子体质谱(ICP-MS)测定的硼同位素质量进行校正,求出校正因子,确定了样品的线性浓度范围,选定样品浓度为1.1 mg/L。在同样的仪器条件下首先测定了硼标准物质的硼同位素丰度比,测量误差为0.2%,然后测定了硼同位素浓缩过程中硼样品的硼同位素丰度比,测定结果的相对标准偏差为1.1%。此外考察了仪器的稳定性。实验结果表明本方法“记忆效应”小,结果可靠,测量精度高。     

地质样品中Mo同位素测定的前处理方法研究

通过对地质样品中Mo同位素测试前的处理方法的比较,对传统的阴、阳离子树脂交换法进行了改进研究.经改进后的方法实用范围较宽,Mo的回收率达到97.49%±0.27%,Mo同位素质谱分析过程中可能的同重干扰元素Zr、Fe、Mn等的去除效果理想,其它金属元素的去除效果也较理想,且在阴离子交换柱洗脱Mo的过程中总计约需的提取液(盐酸和硝酸)体积只有75mL,只需文献报道用量的45%,从而减少了试剂对样品,特别是对低含量地质样品可能带来的潜在污染.     

碰撞池-多接收电感耦合等离子体质谱测定硒同位素的质量偏移效应

通过改变雾化气流量、RF射频发生器功率、矩管位置和碰撞气流量等仪器参数,研究了碰撞池-多接收电感耦合等离子体质谱(Collision Cell-MC-ICP-MS)中的质量偏移效应。实验结果表明,雾化气流量、RF发生器功率和矩管位置等是质量偏移效应的主要来源,而碰撞气流量的影响很小。在此基础上,建立了MC-ICP-MS分析硒同位素丰度的最优化测量条件,同位素比R82/76的测量精度达到0.0043%。采用化学计量方法配制了两个系列硒同位素丰度校正样品,通过不同的同位素丰度比的质量偏移校正因子β和与其对应的同位素对的质量平均值成线性的关系,分析了样品GBW(E)080215和SRM3149中硒的同位素丰度组成。与样品SRM3149中82Se/76Se的比值相比,样品GBW(E)080215中的硒同位素分馏系数δ82/76为-4.78‰。     

绝对质谱法测量钐同位素丰度

使用高浓缩同位素的^152Sm和^154Sm配制不同丰度的Sm基准溶液,对多接收电感耦合等离子体质谱（MC-ICPMS）的系统偏差进行校准,求出^154Sm／^152Sm的平均校准系数。采用指数函数式推算出其它同位素比的校准系数。对天然样品的测量结果进行校正,并与表面热电离质谱的测量结果进行了比较,主同位素对的丰度比误差小于0．03％。实验结果表明,MC-ICPMS测量的影响因素多,系统偏差较大,但是通过校正可以获得与表面热电离质谱一致的测量结果。通过实验,建立了MC-ICPMS的同位素丰度绝对测量方法。     

离子色谱-电感耦合等离子体质谱联用研究尿中碘和钼形态

建立离子色谱-电感耦合等离子体质谱(IC-ICP-MS)联用测定人尿中碘和钼形态的方法,该方法对IO3-和I-检出限分别为0.1 ng/mL和0.2 ng/mL,对MoO42-(以Mo计)的检出限为0.4 ng/mL,IO3-(以I计)、I-和MoO42-(以Mo计)线性回归系数r均大于0.999。检测实际尿样中I-和MoO42-(以Mo计)相对标准偏差RSD均小于5%,实际尿样中未发现IO3-。尿样中I-和MoO42-(以Mo计)的加标回收试验表明其回收率在91%～102%之间。本文利用尺寸排阻色谱-电感耦合等离子体质谱(SEC-ICP-MS)联用首次直接证明人尿中还存在至少3种形态有机碘以及1种形态有机钼。     

红酒中的~(87)Sr/~(86)Sr同位素比测定

研究了多接收电感耦合等离子体质谱(MC-ICP-MS)测定红酒样品中87Sr/86Sr同位素比的分析方法,并用建立的分离测定方法参加了欧洲参考物质与测量研究所(IRMM)组织的CCQM-P105国际比对,即红酒中87Sr/86Sr同位素比的分析比对.红酒样品经微波消解后,采用Dowex 50W×8树脂分离纯化锶,用MC-ICP-MS精确测定锶组分中的87Sr/86Sr同位素比,同时对测量结果的不确定度进行了分析和评定.     

电感耦合等离子体质谱法测定碳化硼中的硼同位素丰度

以碳酸钙为熔剂高温分解,硝酸浸取、硫酸沉淀的方法处理碳化硼样品,稀释后直接进行多接收电感耦合等离子体质谱分析,对碳化硼中的硼同位素丰度进行测定。扫描电镜分析结果表明,碳化硼颗粒形状不规则,尺寸小于50μm。利用建立的方法处理样品,可实现碳化硼样品的完全溶解,回收率接近100%。对样品中10B丰度进行分析,相对标准偏差为0.023%~0.035%(n=6),测量结果与参考值在不确定度范围内保持一致,证明实验方法可行。所建立的碳化硼样品测量方法样品处理步骤简便,分析速度快,测量精度高,可作为碳化硼中硼同位素丰度的常规分析方法。     

电感耦合等离子体质谱(ICP-MS)法测定云南富源耕地土壤中有效钼

有效钼是土壤质量评价不可缺少的指标,为准确高效测定土壤中的有效钼,样品采用Tamm溶液进行浸提,浸提液用硝酸(5%)稀释10倍,确定了分析元素钼的同位素⁹⁵Mo,¹⁰³Rh为内标,校正基体干扰和信号漂移,优化了仪器分析参数,利用电感耦合等离子体质谱仪(ICP-MS)碰撞模式(KED模式)进行有效钼的测定,建立的标准曲线相关系数为1.00,方法的检出限(3σ)为0.002μg/L,对3个国家一级标准物质样品进行土壤中有效钼含量的平行测定,相对误差小于2%,相对标准偏差(RSD)小于5%,对200余件实际样品进行不同方法外检比对,合格率为98%。方法具有操作简单、方便快捷,经济适用等特点,适合于各生产实验室各种类型土壤样品有效钼的大批量分析。     

铈同位素丰度的精确测定研究

通过用高浓缩同位素１４２Ｃｅ和１４０Ｃｅ配制９种混合样品，精确测定质谱计的系统误差校正系数，来校正用该仪器测定的天然铈的同位素丰度比，从而建立了准确测定铈同位素丰度的质谱分析方法，用这种绝对质谱法测定的铈相对原子质量是１４０１１５７±００００８。该数值已于１９９５年为国际理论与应用化学联合会（ＩＵＰＡＣ）的原子量与同位素丰度委员会所采纳     

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.