湿法快速消解-原子荧光光谱法测定农产品中汞含量

建立了湿法快速消解-原子荧光光谱仪测定农产品中汞含量的方法。选取大米和芹菜作为实验样品,对消解酸体系(硝酸、硝酸-过氧化氢、硝酸-高氯酸)、消解温度(100、110、120、130、140℃)和消解时间(30、45、60、90 min)等条件进行探讨,确定最佳实验条件,并与常规微波消解效果进行对比。结果表明,优化后的硝酸-高氯酸体系条件下120℃消解30 min,方法在0~2μg/L范围内线性关系良好,相关系数为0.9996,方法检出限为0.001 mg/kg,精密度为2.4%~3.9%。两种消解方法对于大米和芹菜质控样的测定值基本一致,均在质控样范围。相较于常规微波前处理方法,简化了样品前处理流程,提高了工作效率,可为农产品汞含量检测提供可靠的方法支撑。     

湿法快速消解-原子荧光光谱法测定农产品中汞

建立了湿法快速消解-原子荧光光谱仪测定农产品中汞含量的方法。选取大米和芹菜作为实验样品,对消解酸体系(硝酸、硝酸-过氧化氢、硝酸-高氯酸)、消解温度(100、110、120、130、140℃)和消解时间(30、45、60、90 min)等条件进行探讨,确定最佳实验条件,并与常规微波消解效果进行对比。结果表明,优化后的硝酸-高氯酸体系条件下120℃消解30 min,方法在0～2μg/L范围内线性关系良好,相关系数为0.999 6,方法检出限为0.001 mg/kg,精密度为2.4%～3.9%。两种消解方法对于大米和芹菜质控样的测定值基本一致,均在质控样范围。相较于常规微波前处理方法,简化了样品前处理流程,提高了工作效率,可为农产品汞含量检测提供可靠的方法支撑。     

微波消解-电感耦合等离子体发射光谱法测定固体生物质燃料中8种元素

建立电感耦合等离子体发射光谱法同时测定固体生物质燃料中钾、钠、钙、镁、砷、铜、铁、锰8种元素的含量。样品采用5 mL硝酸溶液和2 mL过氧化氢溶液进行微波消解,在选定的仪器工作条件下进行测定。钠、钙、镁、砷、铜、铁、锰的质量浓度在0～5.0 mg/L,钾的质量浓度在0～50.0 mg/L范围内与光谱强度具有良好的线性关系,相关系数均大于0.999,方法检出限为0.002～0.022 mg/L。样品的加标回收率为91.9%～108.2%,测定结果的相对标准偏差为2.1%～6.8%(n=6)。该方法简便、快速、高效且准确,适用于固体生物质燃料中钾、钠、钙、镁、砷、铜、铁、锰的测定。     

电感耦合等离子体发射光谱法测定REACH法规涉及产品中铅、铬、钴、砷、锡、铝、锆、钼和硼

采用电感耦合等离子体原子发射光谱法对REACH法规涉及产品中铅、铬、钴、砷、锡、铝、锆、钼和硼的含量进行测定。0.2g样品经微波消解处理,聚合物材质试样以8mL硝酸和2mL过氧化氢为消解试剂;无机非金属材质试样以6mL硝酸、2mL过氧化氢和2mL氢氟酸为消解试剂。各元素的方法检出限均低于15mg·kg-1。方法的加标回收率在82.4%～108%之间,测定值的相对标准偏差(n=7)在3%～6%之间。     

氢化物发生-原子荧光光谱测定反应香精中的砷和汞

建立了用氢化物发生-原子荧光光谱法连续测定反应香精中的汞和砷.考察了样品前处理方法和仪器参数对实验结果的影响.实验确定反应香精样品的微波消解试剂为硝酸:过氧化氢=6:2(V/V)、最高消解温度为210℃、消解时间为25 min为最佳前处理条件;原子荧光的还原剂为20 g/L硼氢化钾,载流液为5%盐酸.方法测定汞的回收率为99.2%～110.O%,砷的回收率为96.5%～113.1%.在最优化的条件下对9种反应香精样品进行测定,其中砷和汞的含量均未超过国家标准.     

微波消解-原子荧光法测定山茶油中痕量砷

微波消解优化-原子荧光光谱法测定了山茶油中痕量砷;在多组实验研究的基础上,研究了不同消解酸配比条件下,微波消解方法对测定结果的影响.试验结果表明：微波消解0.3g茶叶对照品和0.3g山茶油样品过程中,消解酸为6mL硝酸+4mL过氧化氢的平行性和回收率最好.山茶油样品回收率为92%-102%;RSD为5.06% 。该法适用于山茶油中痕量砷的测定。     

电感耦合等离子体质谱法测定包装材料中10种有毒元素

建立电感耦合等离子体质谱法测定包装材料中铬,镍,铜,锌、砷、硒、钼、镉、汞、铅10种有毒元素的方法。以硝酸和过氧化氢为消解试剂,采用微波消解法消解样品,在选定的仪器工作条件下进行测定。汞的质量浓度在1～10μg/L范围内,其它9种元素的质量浓度在1～100μg/L范围内与质谱响应值具有良好的线性关系,相关系数均不小于0.999 7,方法检出限为0.000 3～0.027 6 mg/kg。塑料和纸质包装材料样品中10种元素测定结果的相对标准偏差为1.10%～4.44%(n=7),样品加标回收率为85.17%～106.16%。该方法适用于包装材料中多种元素的同时测定。     

虾粉中总砷测定方法的探讨

用氢化物原子荧光光度法测定虾粉中总砷含量时,对干法灰化、湿法消解、微波消解3种样品处理方法对虾粉中砷元素测定结果的影响进行了比较。通过试验确定了最佳消解条件。砷元素浓度在0~10μg/L的范围内与荧光强度呈线性关系,线性相关系数r=0.999 6,检出限为0.2μg/L。比对结果表明,干法灰化适合于测定虾粉中总砷的含量,湿法消解测定总砷的含量偏低,微波消解不适合测定虾粉中总砷的含量。采用干法灰化-氢化物原子荧光光度法测定虾粉中总砷含量,加标回收率为76.2%~106.0%。     

微波消解样品-电感耦合等离子体原子发射光谱法测定固体生物质燃料中的砷含量

提出了电感耦合等离子体原子发射光谱法(ICP-AES)测定固体生物质燃料中砷含量的方法。取样品0.100 0~0.200 0g,加入硝酸5mL和过氧化氢2mL,微波消解并加适量水稀释至一定体积,用此溶液直接进行电感耦合等离子体原子发射光谱法测定其中砷的含量。选择分析谱线为189.042nm,须作背景扣除校正。砷的线性范围为5.0 mg·L-1以内,检出限(3s)为0.006mg·kg-1。按此方法分析了3个标准物质(GBW 10015,GBW 10024,GBW 07602),测定值与认定值相符,测定值的相对标准偏差(n=6)均小于5%。应用此方法分析了5种实样,并用原子荧光光谱法作分析比对,结果表明两方法的测定结果相符。     

微波消解-石墨炉原子吸收光谱法测定印钞油墨中砷

采用石墨炉原子吸收光谱法测定印钞油墨中总砷的含量。样品经硝酸-过氧化氢混合溶液微波消解,以硝酸镍作为基体改进剂,在优化的仪器工作参数下,砷的质量浓度在20μg.L-1以内与其吸光度呈线性关系,检出限(3s/k)为0.84μg.L-1,方法的回收率在92.5%～104.3%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.