DMA80直接汞分析仪测定净水剂中汞

提出了DMA80直接汞分析仪测定净水剂中汞的方法。对仪器的工作条件干燥温度和时间、分解温度和时间、等待时间以及汞齐化时间进行了研究。在优化的试验条件下,吸光度与汞的的质量分数在300μg.L-1以内和300~5 000μg.L-1之间呈线性关系,检出限(3s)为0.029 ng,测定下限(10s)为0.095 ng。按此方法分析了净水剂样品,汞的回收率在90%~100%之间,相对标准偏差(n=6)为0.8%~1.1%。     

氢化物发生-原子荧光光谱法同时测定陈皮中砷和汞

采用微波消解法消解陈皮样品,利用氢化物发生-原子荧光光谱法同时测定陈皮中砷和汞.研究并优化了硼氢化钾的用量、消解介质的酸度、共存离子的干扰和消除等试验条件.荧光强度与砷及汞的质量浓度在20.0μg·L-1及2.00 μg·L-1以内呈线性关系,方法的检出限为0.084μg·L-1(砷)和0.022 μg·L-1(汞).应用此法分析了6个陈皮试样,测定值的相对标准偏差均小于7.0%,以标准加入法做回收率试验,平均回收率分别为93.6%(砷)和90.7%(汞).     

热解吸收-冷原子荧光光谱法测定水泥中痕量汞

将热解吸收技术应用于冷原子荧光光谱法测定水泥样品中痕量汞含量。采用自制的石英管加热550℃处理样品,用0.01mol·L-1高锰酸钾溶液作为吸收液吸收释放出的汞蒸气,用盐酸羟胺还原过量的高锰酸钾后直接进样测定。试验中优化了仪器的工作参数和试验条件。分析中采用载气及屏蔽气的流量依次为400mL.min-1及1 000mL.min-1。荧光强度与汞的质量浓度在2μg·L-1以内呈线性关系,方法的检出限(3σ)为0.020μg·L-1。应用此法分析土壤标准样品(GBW 07405),测定值(0.30μg.g-1)与证书值(0.29±0.03μg.g-1)相符;方法用于测定水泥中汞含量,加标回收率在97.0%～107.0%之间,相对标准偏差(n=5)在0.7%～4.1%之间。     

氢化物发生-冷原子荧光光谱法测定铜精矿中汞

用氢化物发生-冷原子荧光光谱法测定铜精矿中汞的含量。考察了仪器的工作条件原子化温度、原子化器高度、灯电流、负高压、载气和屏蔽气流量对测定的影响。采用主量元素匹配法消除基体干扰,优化了反应体系的介质与酸度、还原剂的浓度等条件。荧光强度与汞的质量浓度在2.0μg.L-1以内呈线性关系,检出限(3s/k)为0.0108μg.L-1,相对标准偏差(n=11)小于2%。此法用于铜精矿样品中汞含量的测定,加标回收率为92.0%～111.7%。     

微波消解原子荧光光谱法测定生物样品中砷汞

采用微波消解样品预处理技术和原子荧光光谱法,测定了生物样品中砷和汞的含量。确定了微波消解样品的条件,优化了仪器的最佳工作参数。砷和汞的含量分别在0~20μg.L-1和0~16μg.L-1范围内线性良好。砷和汞的回收率分别为100.5%和98.6%。砷和汞的检出限分别为0.21和0.06μg.L-1。试验表明,该法快速简便、准确灵敏,应用于生物样品中砷、汞的测定,结果满意。     

原子荧光光谱法测定食品添加剂碳酸钙中汞

采用盐酸(5+95)溶液溶解食品添加剂碳酸钙样品,利用原子荧光光谱法测定碳酸钙试样中汞的含量。优化了灯电流、负高压、原子化器高度、载气及屏蔽气体的流量、载流介质的浓度、硼氢化钾的浓度、共存离子的干扰和消除等试验条件。荧光强度与汞的质量浓度在1.0μg.L-1范围以内呈线性关系,方法的检出限(3s/k)为0.8 ng.L-1,对5.0μg.L-1汞标准溶液进行11次测定的相对标准偏差为0.95%。应用此方法分析了两个碳酸钙试样,以标准加入法做回收试验,平均回收率为103.5%。     

氢化物发生-原子荧光光谱法同时测定水中砷和汞

采用氢化物发生-原子荧光光谱法同时测定水中砷和汞.对仪器的工作条件负高压、灯电流、载气和屏蔽气流量作了详述,还就各种对测定有影响的因素,包括酸的种类及其浓度、硼氢化钾的加入量、硫脲.抗坏血酸混合液的浓度及共存离子的干扰等也作了研究并予以优化选择.荧光强度与砷及汞的质量浓度在0.20～100.00μg·L-1及0.01～80.00μg·L-1范围内呈线性关系,方法的检出限(3S/N)依次为0.06μg·L-1和0.006μg·L-1,精密度试验求得其相对标准偏差(n=11)均小于5%.应用此法对自来水和景观用水进行分析,并以此两样品为基体做回收试验,测得砷和汞的回收率分别为100.2%,104.9%和98.0%,101.0%.     

微波消解氢化物发生-原子荧光光谱法测定罐头食品中汞和锡

建立了一种微波消解、氢化物发生-原子荧光光谱法同时测定罐头食品中汞和锡的方法。研究了测定汞、锡时介质的酸度和硼氢化钾的用量对汞、锡测定的影响。优化了样品消解和测定的条件,采用硫脲-抗坏血酸为掩蔽剂,以酒石酸为载流,消除了影响锡测定的干扰因素。汞和锡的检出限、相对标准偏差、回收率分别为:0.005μg.L-1和0.20μg.L-1;5.0%~6.5%和4.0%~7.3%;93.0%~101.0%和92.5%~94.0%。     

原子荧光光谱法测定玉米中汞

采用微波消解法消解玉米样品,利用氢化物发生-原子荧光光谱法测定玉米中汞.研究并优化了载气及屏蔽气体的流量、硼氢化钾的浓度、灯电流、共存离子的干扰和消除等试验条件.荧光强度与汞的质量浓度在20μg·L-1范围以内呈线性关系,方法的检出限(3S/N)为0.02μg·L-1.应用此法分析了5份玉米试样,以标准加入法做回收率试验,回收率在90.O%～102.5%之间,相对标准偏差(n=10)小于4%.     

冷原子荧光光谱法测定饮用水中痕量汞

针对测定痕量汞的目标,对AFS-930原子荧光光度计的操作条件作了优化试验;特别在PMT的负高压及原子化温均选用了有利于痕量测定的低值,即依次为270 V及200℃。此外,试样测试溶液的硝酸酸度也用了低值即0.16~0.48 mol.L-1硝酸,试验证明在此酸度条件下,可使测定有良好稳定性和精密度。在最佳工作条件下,汞浓度在0~1.0μg.L-1范围内保持线性关系,相关系数达0.999 9。对三种浓度水平的汞进行精密度试验,测定值的RSD均小于2.14%。此方法的检出限为0.002 0μg.L-1,回收率试验的结果在95.8%至104.4%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.