石墨炉原子吸收法测定中药中的微量砷

以硝酸镍作基体改进剂，研究了砷的最佳灰化温度和原子化温度，建立了用石墨护原子吸收法直接测定中药中砷含量的方法。结果表明，砷含量在0～400×10-9范围内与吸光度呈良好的线性关系（γ＝0．9993），对鱼腥草平行测定了6次，相对标准偏差为4．2％，样品中常共存的9种阳离子及酸在实验条件下不干扰测定，回收率在93％～97％之间，结果令人满意。     

乙酰丙酮在低温电热蒸发ICP-AES中的化学改进作用机理研究

近年来 ,低温蒸发技术的研究和应用引起了人们的重视 [1～ 3 ] .我们 [4]曾报道应用乙酰丙酮试剂作化学改进剂 ,于石墨管中低温 (～ 75 0℃ )蒸发铍的乙酰丙酮螯合物的 ETV-ICP-AES法 ,并用于人发中痕量铍的测定 .本文从机理上探讨了待测物 (铍或铬 )在石墨管中的蒸发及传输形式 ;研究了相应的乙酰丙酮螯合物的生成条件及主要影响因素 ;在此基础上得出在低温蒸发条件下相应的规律 .1　实验部分1.1　仪器装置　所用的 ICP-AES仪器、电热蒸发装置及它们之间的连接与文献 [1,4]相同 .紫外 -可见分光光度计 (日本岛津 UV-2 0 0 0 ) ,仪器…     

石墨炉原子吸收光谱法测定饮料中的锗及基体干扰的研究

本实验以硝酸镍为基体改进剂，用塞曼石墨炉原子吸收法测定样品中的微量锗，研究了溶液介质与共存元素对测定的影响。方法简便，准确快速，灵敏度高。     

石墨炉原子吸收法测定铬钢中微量锡

钢中锡为有害元素,会引起钢的性质变差,降低铬铝钒钢的持久强度.其量每增加0.01%,断裂时间缩短10%.原因是锡易在晶界上偏析,造成回火时钢材脆化.所以对钢中锡的测定结果是否正确是至关重要的.微量锡的测定,通常应用化学法、氢化发生-原子吸收法、ICP-MAS法等.化学湿法操作繁琐,试剂耗用多,试剂空白不易掌握;ICP-MAS法仪器昂贵,难以普及.石墨炉原子吸收法作为多种金属元素测定最灵敏技术,为国际标准化组织(ISO)推荐用于碳钢中微量锡的测定.文献[1]报道在测定时,可加入如硝酸镍、硝酸镁、硝酸铰、抗坏血酸和镉等基体改进剂.本文则在前人的基础上,建立了以抗坏血酸作基体改进剂的石墨炉原子吸收法测定铬钢中微量锡,方法简便快速、准确可靠.     

石墨炉原子吸收光谱分析中钯基体改进剂对微量镉测定的影响

对石墨炉原子吸收法和钯基体改进剂测定微量镉的实验方法进行了研究,讨论了钯用量对镉测定灵敏度的影响,根据实验结果及Ｘ光电子谱分析,提出了钯存在下镉在石墨管内的原子化过程是一个以物理作用为主,同时伴有钯的催化还原作用的复杂的物理－化学过程的观点。     

用ETV-ICP-MS研究Cr、Ni、Zr、Nb、Yb在石墨炉中的蒸发/原子化机理

本文以电热蒸发电感耦合等离子体质谱（ETV-ICP-MS）为手段,探讨了Cr、Ni、Zr、Nb和Yb在石墨炉中的蒸发/原子化机理;比较了不同化学改进剂存在条件下,Cr、Ni、Zr、Nb和Yb的蒸发行为和在石墨炉原子吸收（GFAAS）中的原子化行为;考察了石墨炉温度和ICP功率等实验参数对上述元素发射强度及轮廓的影响.结果表明,Pd和Mg化合物的存在对Cr、Ni、Zr、Nb和Yb的蒸发/原子化行为没有明显的化学改进作用;然而,以聚四氟乙烯（PTFE）为化学改进剂时,可显著改善Cr、Ni、Zr、Nb和Yb的蒸发行为,避免难熔碳化物的形成,降低待测物的蒸发温度;对Cr和Ni的GFAAS信号强度略有增强;但是,由于Yb、Nb和Zr氟化物的离解键能很高,难以离解/原子化,PTFE的存在反而降低了Yb、Nb和Zr在GFAAS中的信号强度.     

持久性化学改进剂铱用于石墨炉原子吸收光谱法测定粮食中痕量铅

提出了石墨炉原子吸收光谱法测定粮食中痕量铅量时采用铱作为持久性化学改进剂。用1.000 g.L-1铱(Ⅲ)溶液50μL涂于石墨平台上并按规定步骤处理。结果表明:经铱溶液处理后的平台经至少400次使用仍能保持较好的灵敏度和再现性。使用此平台时,最佳的灰化和原子化温度和时间分别为900℃,10 s和1 800℃,3 s。与磷酸二氢铵-硝酸镁、氯化钯常规改进剂比较,采用铱作持久性化学改进剂,石墨炉原子吸收光谱法测定粮食中铅,灵敏度高且背景信号值低。方法的检出限(3S/N)为8 pg,特征质量为30 pg。试样加标回收率在93.2%~104.5%之间,相对标准偏差(n=7)小于3.5%。     

石墨炉原子吸收法测定黑花生中的硒

该文以转基因食品黑花生为研究对象,针对硒易挥发的特点,建立了高压密闭消解-石墨炉原子吸收光谱法测定黑花生中总硒含量的测定方法.研究表明,HNO3-H2O2可使样品达到最佳消解,以Pd(NO3)2+Mg(NO3)2为基体改进剂,最佳灰化温度和原子化温度分别为500 ℃和2 000 ℃.在优化实验条件下,该方法测定硒的线性...     

微波消解-石墨炉原子吸收法测定食品中的砷

微波消解,采用硝酸镍氯化钯作为基体改进剂石墨炉原子吸收法测定食品中的砷。结果表明,与现行国标中的测砷的方法比较没有显著性差别。具有快速、简便、准确的特点,而且灵敏度高,能满足食品中砷的卫生标准要求。     

硝酸镍作基体改进剂用于石墨炉原子吸收法测定阳极泥中碲

Hamner用无火焰原子吸收法测定金属铬中银、铋、砷、锑、硒和碲时,用硝酸镍作基体改进剂,以避免被测元素在灰化阶段损失。本文在选定的条件下,考察了阳极泥试样中几种主要成分对碲的干扰,选用硝酸镍作基体改进剂,消除了4000倍量铅和1000倍量锡的干扰。试样分解后用标准加入法测定。仪器及工作条件使用配有HGA-400型石墨炉、AS-40型自动进样器和056型记录仪及PRS-10型打印机的P-E703型原子吸收分光光度计;标准石墨管和碲无极放电灯。波长214.3nm;灯用功率9瓦;分光带宽0.2nm;灰化温度1000℃,时间20秒;原子化温度2700℃.时间5秒;净化温度2700℃,时间3秒。干扰试验考察常见阳极泥试样中三种主成份铜、铅和锡对碲的影响表明,4000倍铜不影响碲的测     

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%.     

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.     

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.     

A general and convenient synthesis of 4-(tosylmethyl)semicarbazones and their use in amidoalkylation of hydrogen,heteroatom, and carbon nucleophiles

A general synthesis of previously unknown semicarbazone-based α-amidoalkylating reagents, 4-(tosylmethyl)semicarbazones, has been developed. The synthesis involved three-component condensation of semicarbazones of aliphatic or aromatic aldehydes with the same or other aldehydes and p-toluenesulfinic acid. The scope and limitations of this reaction were investigated. The compounds obtained were demonstrated to be an efficient α-(4-semicarbazono)alkylating agents. They were reacted with H- (sodium borohydride), O- (sodium methylate), S- (sodium phenylthiolate), N- (pyrrolidine, sodium succinimide), P- (trialkyl phosphites), and C-nucleophiles (sodium diethyl malonate) to give the corresponding products of the tosyl group substitution, 4-substituted semicarbazones, including analogues of nitrofurazone. Among the prepared compounds tested in vitro for antibacterial and antifungal activity, three nitrofuryl-containing semicarbazones exhibited high biological activities with minimum inhibitory concentration (MIC) values of 8–32 μg/mL.     

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.     

Synthesis of novel chiral bidentate hydroxyalkyl-N-heterocyclic carbene ligands and their application in palladium-catalyzed Mizoroki–Heck couplings and asymmetric addition of diethylzinc to benzaldehyde

A small library of new chiral bidentate hydroxyalkyl-imidazolium salts 1 is conveniently synthesized on multi-gram scale from inexpensive and commercially available chiral pool amino acids. The corresponding carbenes, generated by deprotonation of imidazolium salts 1, in combination with palladium(II) chloride were tested in the Mizoroki–Heck coupling reaction. The most significant results in terms of yields and reactivities were achieved with low catalyst loading. The catalytic activities of these imidazolium salts were also investigated in the asymmetric addition of diethylzinc to benzaldehyde. The use of MgO nanoparticles as an additive in conjunction with these ligands played a crucial role in increasing the efficiency of these reactions.