流动注射-火焰原子吸收光度法测定矿泉水中的锶

用流动注射离子交换系统于酸性条件下在线富集饮用天然矿泉水中的锶,火焰原子吸收光度法测定,共存成分无干扰,方法简便快速,富集倍数可随意调节。在 60 h～(-1)的进样频率下,灵敏度提高 17倍。用于矿泉水中锶的测定,当含量为 60～250 ng/ml时,相对标准偏差为 0.68％～0.94％。回收率为 94.4％～110.3％,检测限为 15ng/ml。     

火焰原子吸收光谱法测定饮用水中铜和锶的研究

实验的主要目的是对火焰原子吸收光谱法测定饮用水中铜和锶的方法进行研究。其中对火焰原子吸收光谱法测定锶的两种方法均进行了研究。在选定的最佳仪器条件下,测定铜、锶(方法 1)和锶(方法 2)RSD分别为0.65%、2.67%、1.01%。饮用水中铜、锶(方法 1)和锶(方法2)的回收率分别为95.00%、95.00%、91.00%。实验表明,该法操作简单、测试快速、结果准确稳定。     

电感耦合等离子体原子发射光谱法结合干扰元素校正测定茶叶中的重金属

用微波消解法处理茶叶样品,采用电感耦合等离子体原子发射光谱法测定其中的钡、钴、铬、铜、镍、铅、锶和钒。通过光谱干扰校正技术消除元素干扰。钡、钴、铬、铜、镍、铅、锶和钒的检出限(3s/k)分别为0.17,1.1,3.2,2.6,2.0,5.1,0.17,0.78μg·L-1。方法用于测定GBW10052标准物质中的重金属元素,测定值与认定值相吻合,相对标准偏差(n=6)在0.41%~1.6%之间。     

电感耦合等离子体原子发射光谱法(ICP-AES)测定无定形硼粉中的镁

提出了使用电感耦合等离子体原子发射光谱法(ICP-AES)测定Mg元素的方法。采用硝酸、盐酸溶解样品,用硝酸和盐酸的混合酸作为测定介质,在选定的仪器条件下直接测定Mg元素的检出限为0.0044μg/mL,相对标准偏差RSD(n=6)为0.49%～0.60%,样品加标回收率在94.0%～102.0%之间。经对比试验证明,电感耦合等离子体原子发射光谱法(ICP-AES)测定无定形硼粉中Mg的测定值与美国军用标准重量法测定值一致。     

电感耦合等离子体质谱法测定吉祥草根茎中多种金属元素含量

吉祥草根茎样品经微波消解处理,采用电感耦合等离子体质谱法测定样品溶液中27种金属元素的含量。使用碰撞反应池技术消除了多原子离子对锂、铍、硼、镁、铝、钴、镍、镓、铷、锶、碲、钡、铋和铀等14种元素的干扰。方法的检出限(3s)在0.003～9.79μg.L-1之间。方法用于吉祥草根茎样品的分析,回收率在92.0%～106%之间,相对标准偏差(n=8)在0.06%～4.4%之间。     

微波消解样品-电感耦合等离子体原子发射光谱法测定竹叶中9种必需微量元素

竹叶样品置于聚四氟乙烯罐中,加入硝酸及过氧化氢后在微波消解仪中按设定程序加热消解。所得样品溶液定容至25mL后用电感耦合等离子体原子发射光谱法测定其中铬、锌、镍、钴、铁、硼、锰、铜和锶等9种元素的含量。9种元素的质量浓度在0.05～2.00mg.L-1范围内与其发射强度呈线性关系,方法的检出限(3s)在0.04～0.50μg.g-1之间。方法应用于分析了一种杨树叶标准物质(GBW 07604),所得9种元素的测定结果与证书值相符。方法的回收率在87.0%～107.6%之间。     

电感耦合等离子体原子发射光谱法测定铸造铝合金中磷含量

提出了电感耦合等离子体原子发射光谱法测定铸造铝合金中磷含量的方法。铸造铝合金称样0.500 0g,用硝酸(1+1)溶液12mL和氢氟酸4mL溶解。选择波长为213.618nm谱线作为测定磷的分析线。磷的质量浓度在4.00mg·L-1以内与其发射强度呈线性关系,方法的检出限(3s/k)为0.020mg·L-1。方法用于分析5个铸造铝合金标准物质,测定值与认定值相符,相对标准偏差(n=6)在0.43%～2.2%之间,回收率在94.0%～109%之间。     

碳酸钙共沉淀原子吸收法测定天然水中锶

采用CaCO3共沉淀富集天然水中痕量锶后，再用空气-乙缺焰原子吸收法测定，使方法灵敏度提高一个数量级。本法简便，准确，最低检出限达0.0012mg/L。对0.10mg/L的锶水样，十次测定的标准偏差为0.0082，相对标准偏差为8.2%。     

三磁场塞曼背景校正技术用于石墨炉原子吸收光谱法测定水中铝

在石墨炉原子吸收光谱法测定水样中铝时,采用三磁场塞曼背景校正技术。铝的质量浓度在0.4mg.L-1以内与吸光度呈线性关系,方法的检出限(3s)为0.04μg。方法用于实验室能力验证标准溶液(NIL PT-0130)中铝的测定,测定结果与电感耦合等离子体质谱法测定值相符。取3个浓度水平的铝标准溶液进行精密度试验,平行测定6次,测定值的相对标准偏差在2.7%～4.3%之间。     

火焰原子吸收光谱法测定氯化物型卤水中微量铷

对火焰原子吸收光谱法测定氯化物型卤水中微量铷时共存离子,包括钾、钠、钙、镁等的干扰作了试验,并根据试验结果对文献报道的火焰原子吸收光谱法测定简单卤水中铷的条件作了改进.试验表明:当在制作标准曲线时加入与试样中含量相近的上述离子,可抵消其干扰.按此条件,毋需任何预处理,即可直接测定铷.应用此方法分析了两件已知样品中铷量,所得结果与已知值相符.以此样品为基础加入铷标准溶液作回收试验,测得回收率在92%～108%之间.     

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.