密闭溶样两次金泵齐冷原子吸收光谱法测定煤中微量汞

建立了密闭溶样两次金汞齐冷原子吸收光谱法测定煤样中微量汞的方法，该法具有试剂空白低的特点，适合于测定煤样中的微量汞。研究表明，该法最低检出限为２．５×１０＾－９，精密度为７．３％，回收率平均为９９．８１％。     

冷原子吸收法测定锌精矿中的汞

采用冷原子吸收法测定出口锌精矿中汞,完善了国家标准锌精矿化学分析方法没有汞的测定方法之不足,该法测定范围为０．０５－０．３０μｇ／ｍｌ,回收率为９９．６％－１０６．５％,变异系数为１．８１％－３．０２％,能满足微量汞测定要求。     

微量汞分析的探讨

应用原子吸收分光光度法对微量汞分析进行了探讨，在灯电流为６或７ｍＡ检测波长为２３５．７ｍ样品浓度在０．１～５．０μｇ范围内线性关系良好，ｒ＝０．９９９９５，平均回收率９８．９３％，ＲＳＤ＝０．４７％，证明本法测定微量汞准确度高，稳定性好，值得推广使用。     

冷原子荧光法测定甲壳素中的痕量汞

研究了冷原子荧光法测定甲壳素中痕量汞的工作条件。样品风干后在2mol／L HNO3-4mol／L HCl体系中以V2O5为催化剂消解1h，上清液中的汞被SnCl2还原后于253．7nm用冷原子荧光法测定。在以10％SnCl2为还原剂时，线性范围0～2．0ng/mL，r=0．9997，检出限为0．05ng/mL，相对标准偏差2．5％，平均回收率在86．3％～110．0％，该法简便、快速、准确。     

冷蒸汽原子吸收光谱法测定四种中成药中汞含量

利用测汞仪测汞具有操作简便、灵敏度高、准确性较好等优点,测定了乌鸡白凤丸、增长乐、健儿三宝冲剂、龙牡壮骨冲剂四种中成药中的汞。若参照许多国家和地区药中汞限定小于０５×１０－６标准,增长乐汞含量超标,其他三种含量都较低。此测定方法适用于各种中成药中微量汞的测定。     

氧瓶燃烧—冷原子吸收法测煤样中痕量汞

采用氧瓶燃烧－针筒注射－冷原子吸收法测煤样中痕量汞，并对测定条件进行研究。方法简便、快速、干扰少，汞含量在０￣１０．０ｎｇ／５０ｍｌ时遵守比耳定律。用于样品的测定，结果令人满意。     

石墨炉原子吸收法测定聚苯乙烯泡沫塑料中的汞

本文提出的在聚苯乙烯泡沫塑料中测定汞的方法是将样品溶解在苯中，以Ｎａ２Ｓ２Ｏ３溶液反洗出汞，利用反洗液中Ｎａ２Ｓ２Ｏ３作基体改进剂，石墨炉原子吸收法测定汞，方法简便，快速，特征量为８０ｐｇ／０．００４４Ａ。本法分析样品与冷原子荧光法的结果一致，相对标准偏差≤８％，回收率９２％－１０２％。     

分光光度法测定水中微量汞

以巯基棉分离富集、用分光光度法测定水中微量汞。汞与溴化钠和罗丹明B形成水溶性离子缔合物,该缔合物在532nm处有最大吸收。汞浓度在0～0.16mg/L范围内符合比尔定律,摩尔吸光系数为8.76×10~5L/(mol·cm),该方法的回收率为99％～102％。     

固体进样一直接测汞仪法测定金精矿粉中微量汞

将金精矿粉样品直接置于石英舟中,在高纯氧气氛中燃烧,释放出汞,与齐化管中的金形成金汞齐,于900℃热释放出汞蒸汽,用直接测汞仪法测定汞的含量。测定结果的相对标准偏差为0．28％～1．57％（n=6）,方法检出限为1．0pg／kg,加标回收率为95．7％～117．4％。用该法对4种土壤标准样品进行了测定,测定结果与标准值相符。该方法适合于金精矿粉中微量汞的测定。     

冷原子荧光法测定鲨鱼肝脏中的痕量汞

研究了冷原子荧光法测定鲨鱼肝脏中痕量汞的工作条件。样品风干后在2mol/L HNO3-4mol/L HCI体系中以V2O5为催化剂消解1h,上清液中的汞被SnCl2还原后于253.7nm用冷原子荧光法测定,在以10％SnCl2为还原剂时,线性范围0～0.2ng/mL,r=0.9997,检出限为0.05ng/mL,相对标准偏差2.5％,平均回收率94.0％～109.5％,该法简便、快速、准确。     

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.