微波消解样品-氢化物发生-原子荧光光谱法测定海贝中硒

海贝样品经硝酸和过氧化氢微波加热消解,用氢化物发生-原子荧光光谱法测定其中硒的含量。使用溶于5g·L~（-1）氢氧化钾溶液中的10g·L~（-1）硼氢化钾溶液与溶液中硒离子反应生成氢化物。试样溶液中加入抗坏血酸消除硝酸的干扰。在优化的试验条件下,硒的质量浓度在600μg·L~（-1）以内与其荧光强度呈线性关系;方法检出...     

密闭消解-氢化物发生-原子荧光光谱法测定植物中硒

采用密闭消解-氢化物发生-原子荧光光谱法测定植物中硒的含量。植物样品采用硝酸-过氧化氢(2+1)混合液于130℃密闭消解4h,以10g·L~(-1)硼氢化钠溶液作为还原剂。硒的质量浓度在2~10μg·L~(-1)内与其对应的荧光强度呈线性关系,检出限(3s/k)为0.18μg·L~(-1)。对10μg·L~(-1)的硒标准溶液连续测定6次,测定值的相对标准偏差为0.63%。以圆白菜标准物质(GBW 10014)为基体进行加标回收试验,所得回收率为102%。     

微波消解样品-原子荧光光谱法测定酸菜中砷

称取一定量已切碎、捣碎并混匀的酸菜样品用硝酸及过氧化氢先在90℃水浴中消解约20min,然后将溶液冷却,移入微波消解仪中消解。消解完毕后将溶液冷至室温,移入25mL容量瓶中,加入50g·L~(-1)硫脲-50g·L~(-1)抗坏血酸混合溶液5 mL,加水定容。在所选定的仪器条件下用14g·L~(-1)硼氢化钾溶液作还原剂生成砷的氢化物进行测定。砷的质量浓度在10.00μg·L~(-1)以内与相应的荧光强度值呈线性关系。方法的检出限(3s/k)为0.064μg·L~(-1),测得方法的回收率在89.0%～102.5%之间,测定值的相对标准偏差(n=6)为1.7%。     

顺序注射-氢化物发生-原子荧光光谱法测定海产品中无机硒和有机硒

海产品样品(2.500 0g)采用盐酸(1+1)溶液25mL于60℃提取18h,经脱脂棉过滤,滤液经环己烷5mL萃取后分层;取水相4.00mL采用顺序注射-氢化物发生-原子荧光光谱法测定其中无机硒的含量。另取样按微波消解-原子荧光光谱法测定此样品中的总硒量。采用差减法计算有机硒的含量。无机硒的质量浓度在1.00~20.0μg·L~(-1)范围内与其荧光强度呈线性关系,检出限(3s)为0.113μg·L~(-1)。在0.100,1.00,2.00mg·kg~(-1)等3个浓度水平进行加标回收试验和精密度试验,回收率在84.8%~93.5%之间,测定值的相对标准偏差(n=6)在1.6%~2.5%之间。     

氢化物发生-原子荧光光谱法测定低合金钢中微量砷

采用氢化物发生-原子荧光光谱法测定低合金钢中砷的含量。样品经盐酸-硝酸混合酸消解,以盐酸(5+95)溶液为反应介质,15g·L~(-1)硼氢化钾-2g·L~(-1)氢氧化钾的混合溶液为还原剂,采用柠檬酸作为掩蔽剂。砷的质量浓度在60.0μg·L~(-1)以内与荧光强度呈线性关系,方法的检出限(3s/k)为0.023μg·L~(-1)。应用此法对标准钢样进行了分析,测定结果与认定值相符合,可满足钢铁中微量砷(质量分数0.001%～0.04%)的测定要求。     

氢化物发生-原子荧光光谱法测定大蒜中砷和硒

采用氢化物发生-原子荧光光谱法测定大蒜中砷和硒。样品经硝酸和高氯酸消解,在盐酸(5+95)溶液中,加入溶于50g·L~(-1)氢氧化钠溶液的20g·L~(-1)硼氢化钾溶液,使其与溶液中砷及硒离子反应生成氢化物。分析中采用载气流量依次为800mL·min~(-1),600mL·min~(-1),屏蔽气的流量均为1000mL·min~(-1)。试样溶液中加入硫脲-抗坏血酸混合溶液作为还原剂。于仪器中引入试样溶液0.5mL,按选定的工作条件操作。砷及硒的质量浓度分别在0.04～0.40,1.00～10.0μg·L~(-1)范围内与其荧光强度呈线性关系,方法的检出限(3s/k)砷为0.017μg·L~(-1),硒为0.314μg·L~(-1)。分别加入两元素的标准溶液作回收试验,测得砷和硒的回收率分别在95.3%～104.4%和94.7%～105.2%之间。     

稀酸酸解-电感耦合等离子体质谱法测定土壤中14种无机元素的含量

先用3~4mol·L~(-1)过氧化氢溶液6mL将样品(0.100 0~0.200 0g)预消解2h,再按程序升温微波消解,冷却,加入7mol·L~(-1)硝酸溶液2mL,按程序升温重复消解一次,用水定重至10.0g,离心后取上清液,用电感耦合等离子体质谱法测定14种无机元素的含量。各元素的检出限(3s)在0.002 0~0.63mg·kg~(-1)之间。按此方法分析了土壤标准样品,测得结果与认定值一致。用主成分分析法得出镍、钒、锌和镉等为土壤的特征性元素,其规律性可作为土壤样品的指纹图谱。特征元素与样品中有机质含量的相关性分析表明,二者关联性不大。     

微波消解-电感耦合等离子体质谱法测定石墨烯粉末材料中19种痕量元素

石墨烯粉末材料样品采用硝酸-氢氟酸-过氧化氢混合液进行微波消解,冷却后,用水稀释至100.0mL,采用电感耦合等离子体质谱法测定其中砷、钡、铋、钴、铬、铜、钾、镁、钼、镍、铅、锑、锡、钛、钒、锌、镉、镧、铈等19种痕量元素的含量。以103 Rh和45Sc为内标,采用同位素克服质谱干扰。19种痕量元素的质量浓度均在500μg·L~(-1)以内与其对应的发射强度呈线性关系,检出限为0.01～3.9μg·L~(-1)。加标回收率为82.2%～123%,测定值的相对标准偏差(n=8)为2.6%～8.5%。     

微波消解-电感耦合等离子体质谱法同时测定铝土矿中11种金属元素

建立了微波消解-电感耦合等离子体质谱法(ICP-MS)同时测定铝土矿中锂、铬、铜、铁、钛、钾、钠、钙、镁、铅、锌等11种金属元素含量的方法。将铝土矿粉碎、研磨和干燥后,取0.1 g样品,加入3 mL硫酸、1 mL硝酸、2 mL氢氟酸和3 mL盐酸,按升温程序微波消解样品,加40 g·L~(-1)硼酸溶液10 mL,继续在120℃下消解10 min,使消解液变澄清。冷却后取出,180℃加热至近干,用1%(体积分数)硝酸溶液稀释,按照ICP-MS条件测定。通过用10 g·L~(-1)铝基体溶液配制混合标准溶液系列并加入内标元素Sc、Ge、Bi的方法来消除基体干扰,选择合适的待测元素同位素的方法来消除谱线重叠干扰。结果显示:11种元素的质量浓度均在一定范围内与其对应的响应值与内标元素响应值的比值呈线性关系,检出限(3s)为0.011～1.400 mg·kg~(-1)。对实际样品进行加标回收试验,测定值为0.13～72.21 mg·L~(-1),测定值的相对标准偏差(n=6)为0.69%～2.6%,回收率为94.0%～106%;此方法用于分析3种铝土矿成分分析标准物质GBW 07177、GBW 07179、GBW 07180,所得测定值均在认定值要求的范围内。     

吹扫捕集-气相色谱-质谱法同时测定水中11种醚类化合物

采用已加入4g质量比为3∶1的碳酸钠和氯化钠的混合物(盐析剂)的40mL棕色硼硅玻璃瓶采集水样,使水样充满样品瓶。采用吹扫捕集-气相色谱-质谱法同时测定水样中11种醚类化合物的含量。在气相色谱分离中采用HP-VOC色谱柱(90m×0.32mm,1.8μm),在质谱分析中采用选择离子监测模式。以氟苯为内标,环氧乙烷、环氧丙烷、四氢呋喃的线性范围均为5.0～100μg·L~(-1),其他8种醚类化合物的线性范围均为0.50～50μg·L~(-1),检出限为0.113～2.62μg·L~(-1)。以空白管网末梢水样品为基体进行加标回收试验,所得回收率为85.3%～115%,测定值的相对标准偏差(n=6)为3.0%～9.4%。     

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.