微波消解-石墨炉原子吸收光谱法测定污水厂污泥和进、出水中的镉、铅

建立了微波消解–石墨炉原子吸收光谱法测定污水处理厂进出水和污泥中重金属Cd,Pb的方法。分别向污水样品中加入5.0 mL硝酸,污泥样品中加入4.0 mL硝酸和2.0 mL双氧水,放入微波消解炉中进行消解。消解好的样品用1%NH_4H_2PO_4作为基体改进剂,在0.5%HNO_3介质中采用塞曼扣除背景,石墨炉程序升温方式进行Cd,Pb的原子化,用石墨炉原子吸收光谱法测定Cd,Pb的含量。Cd,Pb的质量浓度分别在0~2.00μg/L,0~40.0μg/L范围内与其吸收峰高呈良好的线性关系,线性相关系数分别为0.999 1,0.999 6。Cd,Pb检出限分别为0.104 9,0.394 5μg/L,测定结果的相对标准偏差分别为1.34%~3.61%,2.12%~2.80%(n=11),加标回收率分别为98.2%~102.6%,94.0%~100.4%。该方法简单,高效,结果准确度高,重现性好,适用于污水处理厂的进出水和污泥中重金属铅和镉的检测。     

微波消解-GFAAS测定浅水湖泊底泥中重金属元素

探讨了采用微波消解作为底泥样品的前处理方法,运用石墨炉原子吸收法测定浅水湖泊底泥中Cu,Pb,Zn,Cd,Cr含量的实验条件.方法的RSD为2.0％～4.1％,平均回收率为97.4％～101.5％,Cu,Pb,Zn,Cd,Cr的检出限分别为0.4,5,2.8,0.25,2.5ng.该法适合于浅水湖泊底泥中重金属含量的测定.     

固体进样-石墨炉原子吸收光谱法测定土壤中重金属

采用直接固体进样-石墨炉原子吸收分析技术,研究了基体改性剂、灰化温度和原子化温度对土壤中As,Cd,Zn,Sn,Hg,Pb,Cr,Cu和Mn 9种重金属含量分析的影响。当As,Cd,Zn,Sn和Hg等元素使用Pd(NO3)2+M g(NO3)2作为基体改进剂时有利于吸光度的增加,而NH4H2PO4作为基体改进剂有利于Pb,Cr,Cu和M n吸光度的增加。方法应用于国家标准物质,结果与推荐值相吻合,方法 RSD优于7.0%,各种重金属方法检出限均低于0.1223 ng。     

微波消解-高分辨连续光源原子吸收光谱法测定锁阳和韭菜籽中的重金属元素含量

利用微波消解-高分辨连续光源原子吸收光谱法测定锁阳、韭菜籽两种中药材中铜(Cu)、铅(Pb)、镉(Cd)、铬(Cr)、砷(As)和汞(Hg)的含量.采用微波消解进行样品前处理,火焰原子吸收法测定其中的Cu含量,石墨炉原子吸收法测定Pb、Cd和Cr含量,氢化物发生原子吸收法测定As、Hg含量.方法线性关系良好,相关系数R^2大于0.999,加标回收率为95.61%~100.1%,RSD为0.8%~3.3%,测得锁阳和韭菜籽中Cu、Pb、Cd、Cr、As和Hg的含量值均低于《药用植物及制剂进口绿色行业标准》和食品安全国家标准《食品中污染物限量》(GB2762-2012)中规定的限量指标.方法分析速率快、干扰少、精密度高,适用于中药材中重金属含量的测定.     

原子吸收光谱法测定烟叶中的重金属总量及形态分析

采用火焰原子吸收光谱法测定烟叶中Mn,Cu,Zn元素,石墨炉原子吸收光谱法测定Cd,Cr,Pb元素,以HNO3-H2O2微波消解法获取烟叶中的重金属总量,以超声水提取法获取水溶态重金属进行初级形态分析,以Tessier逐级提取法获取5种形态的重金属进行次级形态分析。实验结果表明,原子吸收光谱法检测6种重金属线性良好,相关系数(r2)不低于0.998 8,检出限为0.16~3.1μg·L-1。烟叶样品中Mn,Cu,Zn,Cd元素主要以可交换态和碳酸盐结合态的形式存在;Cr主要以残渣态的形式存在;而Pb主要以碳酸盐结合态和残渣态的形式存在。     

浊点萃取-石墨炉原子吸收光谱法同时测定生物样品中痕量铅和镉

提出了石墨炉原子吸收光谱法同时测定小鼠肝中痕量Pb和Cd的方法。以8-羟基喹啉为络合剂,在pH 9.0时,用Triton X-100浊点萃取富集样品中的Pb和Cd。用NH4H2PO4作为基体改进剂测定Pb和Cd,Pb和Cd的检出限(3s/k)分别为0.103μg/L和0.0136μg/L,相对标准差(n=6)分别为1.4%,0.73%。对于10 mL样品溶液的富集倍数分别为7.1,9.3。利用该法分别测定了小鼠肝中的Pb和Cd的含量,加标回收率分别为96.4%～97.1%和101.3%～103.2%。     

半密闭酸溶-电感耦合等离子体质谱（ICP-MS)）法测定化探样品中的铬镍铜锌镉铅6种重金属

采用半密闭酸溶消解法处理样品，选择离线校正的方式校正了Sn对Cd的同量异位素的干扰，增加积分时间和读数次数提高了Cd的准确度和精密度，建立了电感耦合等离子体质谱仪（ICP-MS）测定化探样品中Cr、Ni、Cu、Zn、Cd、Pb六种重金属元素的方法。对前处理方法和仪器的参数条件进行了优化，结果表明，半密闭体系可达到回流的目的，样品分解完全且无污染现象，在最优的实验条件下，标准曲线的相关系数均不小于0.9997，检出限为0.019~1.65 μg/g ，测定下限为0.057~4.95 μg/g 。按照实验方法对岩石、水系沉积物和土壤国家标准物质中Cr、Ni、Cu、Zn、Cd、Pb平行测定12次，各元素的测定结果与认定值基本一致，相对偏差均不大于3.55%，相对误差均不大于 10.34% 。采用实验方法对土壤样品进行分析，测定结果与四酸溶解-ICP-OES测定Cr、Ni、Cu、Zn、Pb，火焰-石墨炉原子吸收法测定Cd的结果基本吻合。     

塞曼石墨炉原子吸收光谱法测定茶叶中镉

建立了石墨炉原子吸收光谱法测定茶叶中镉含量的分析方法。以1%磷酸二氢铵 1%硝酸镁的混合液为基体改进剂测定了茶叶中的镉,方法的回收率96.0%~103.0%,检出限为0.076ng/mL,测定结果令人满意。     

原子吸收光谱法测定人参中15个微量元素

本文研究了火焰原子吸收,石墨炉原子吸收,结合基体改进剂和平台技术,测定了人参中Pb、Ca、Co、Ni、Cr、Ba、K、Na、Cd、Mg、Fe、Cu、Zu、Mn、Sr等十五个微量元素,结果满意。     

石墨炉原子吸收法测定土壤中铅、镉、钴、锑、铍

建立石墨炉原子吸收法测定土壤中铅、镉、钴、锑、铍含量的方法。优化了石墨炉原子吸收光谱法测定条件,在最佳实验条件下,采用硝酸-盐酸-氢氟酸-双氧水混合酸体系微波消解土壤样品,选用抗坏血酸-硝酸镁混合溶液为基体改进剂。铅、镉、钴、锑、铍的质量浓度在各自的范围内与吸光度成良好的线性关系,相关系数均大于0.999,各元素的检出限为0.008~0.06 μg/g。样品加标回收率为90.5%~104.0%,测定结果的相对标准偏差均小于2.5%(n=6)。该方法样品前处理简便,灵敏度高,检出限低,测定结果准确、可靠,可用于土壤中铅、镉、钴、锑、铍的测定。     

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.