析相微萃取-石墨炉原子吸收法测定生物样品中痕量镉

本文以双硫腙为络合剂,乙酸乙酯为萃取剂,建立了析相微萃取-石墨炉原子吸收光谱法测定环境生物样品中痕量镉的分析方法.考察了析相规律及影响萃取的酸度条件及络合剂用量等因素,方法线性范围为0.005～0.20μg/L,相对标准偏差(RSD)为4.0%(n=7),与未经析相微萃取方法测定相比,灵敏度提高了20倍.所建立的方法用于测定国家标准物质杨树叶、灌木枝叶、人发中镉的含量,结果与参考值具有良好的一致性.     

非螯合物浊点萃取-石墨炉原子吸收法测定水中痕量铊(Ⅲ)

建立不需形成螯合物的浊点萃取-石墨炉原子吸收法测定水中铊Ⅲ的新方法。用浊点萃取技术富集水中铊Ⅲ,石墨炉原子吸收法测定。经考察,浊点萃取环境水体中铊Ⅲ的最优条件为pH12,90℃水浴2h,Triton X-114浓度2.0g/L;在优化后实验条件下,方法测定铊Ⅲ的检出限为0.018μg/L;相对标准偏差为8.89%~13.7%(C=0.1μg/L及1.0μg/L,n=7);加标回收率为98.0%~101%。本法适于水中痕量铊Ⅲ的测定。     

分散液相微萃取-连续光源-石墨炉原子吸收光谱法测定水样中痕量铬(Ⅵ)

采用分散液相微萃取-连续光源石墨炉原子吸收光谱法,以吡咯烷基二硫代氨基甲酸铵(APDC)为螯合剂,CCl4为萃取溶剂,乙醇为分散剂测定环境水样中痕量Cr(VI),并考察了pH、萃取时间、温度和盐度等影响因素。结果表明,DLLME萃取5 mL水样的最佳条件为:pH 2.0,温度为35℃,螯合剂0.012 g/L,萃取溶剂30μL,分散剂0.5 mL。在此条件下,水样中铬(VI)的检出限为0.005μg/L,线性范围为0.05~2.00μg/L,对0.20μg/L,1.00μg/L Cr(VI)标准液分别测定10次的相对标准偏差为0.3%和2.4%。     

磁性固相萃取-石墨炉原子吸收光谱法联用分析水样中痕量镍

建立了磁性固相萃取联用石墨炉原子吸收光谱仪检测水中痕量Ni的方法。通过共沉淀法制备磁性碳纳米材料,用以富集了水样中的Ni2+,并使用石墨炉原子吸收光谱法进行检测。对影响萃取效率的主要因素,包括溶液pH、样品流速、样品体积、洗脱液浓度和体积等条件进行了优化。在最优实验条件下,Ni在0.01~5μg/L内呈良好线性,RSD为3.6%(1.0μg/L,n=11),检出限低至1.8 ng/L,富集因子可达到80。方法已用于标准物质和实际样品中Ni的快速检测。     

石墨炉原子吸收光谱法测定蚕蛹中Cr、Se量

建立了石墨炉原子吸收光谱法测定蚕蛹中Cr、Se的方法,为蚕蛹新资源食品的开发及明确其营养价值提供科学数据。利用石墨炉原子吸收光谱法,偏振塞曼效应扣除背景,石墨炉程序升温方式进行Cr、Se的原子化,检测峰值吸收。加入硝酸镍、吐温X-100为基体改进剂,在体积分数0.5%HNO3介质中对桑蚕蛹中Cr、Se进行测定。方法的精密度:4.0%(Cr),3.1%(Se)。加标回收率:96.8%~105.3%(Cr),92.1%~108.8%(Se)。Cr、Se的线性范围和检出限分别为:0~10μg/L(Cr),0~40μg/L(Se);LOD=1.22μg/L(Cr),1.86μg/L(Se)。建立的分析方法适用于蚕蛹中Cr、Se的测定。     

共萃取辅助浊点萃取-石墨炉原子吸收法测定水中铅

建立了共萃取辅助浊点萃取-石墨炉原子吸收法测定水样中Pb的方法。将茜素黄R作为络合剂,通过加入Ca Cl2建立共萃取体系,将Pb转化为疏水性络合物,从而被萃取到Triton X-114表面活性剂中,经离心与水相分开。最后用1%HNO_3-甲醇溶液稀释以降低表面活性剂粘度,石墨炉原子吸收法测定。在优化的实验条件下,Pb质量浓度在0.40~4.8μg/L的范围内,与吸光度成良好的线性关系,检测限为29 ng/L。对于10 mL的样品溶液,富集倍数为16.3倍。方法已用于水样中痕量Pb的测定,加标回收率为98.0%~103.6%。     

甲基异丁基甲酮萃取石墨炉原子吸收光谱法测定地质样品中的痕量银

建立了石墨炉原子吸收光谱法测定痕量银的方法。研究了仪器工作参数、分离条件及共存离子的干扰,确定了最佳测定条件。结果表明:地质样品经焙烧,用氢氟酸–盐酸–硝酸–高氯酸溶矿,在5%的盐酸介质中加入0.5m L 200 g/L的抗坏血酸溶液及0.25 m L 300 g/L的碘化钾溶液,并以2.0 m L 50 g/L的EDTA溶液掩蔽Cu2+,Pb2+,用2.0 m L甲基异丁基甲酮萃取分离银,在灰化温度500℃、原子化温度2 200℃条件下进行有机相测定。方法检出限为0.084μg/L,测定结果的相对标准偏差为1.89~3.91%(n=6),对国家一级标准物质测定,结果与标准值相符合。     

浊点萃取-石墨炉原子吸收光谱法测定水样中痕量铝

提出了浊点萃取石墨炉原子吸收光谱法测定痕量铝的新方法。探讨了溶液pH、试剂浓度等实验条件对浊点萃取及测定灵敏度的影响。在最佳条件下,富集40 mL样品溶液,用石墨炉原子吸收光谱法测定,铝的检出限为0.045μg/L,铝的富集倍率为78.5倍。方法适用于自来水、河水及海水中痕量铝的测定。     

石墨炉原子光谱法测定工业废渣中痕量元素砷、铅、铬、钡、银

建立了石墨炉原子吸收光谱法测定检测工业废渣中痕量元素砷、铅、铬、钡、银的方法。采用悬浮进样,硝酸-硫酸混合酸溶解样品。10g/L Mg(NO3)2作基体改进剂,提高了砷的灰化温度,加入10g/L CaCO3防止钡在石墨炉中形成不易挥发的碳化钡,增加了钡的灵敏度。回收率为98%～112%,测定结果的相对标准偏差为2.22%～4.46%。As的线性范围2～80μg/L,Pb的线性范围1～60μg/L,Cr的线性范围0.5～20μg/L,Ba的线性范围5～150μg/L,Ag的线性范围1～100μg/L。     

溶剂萃取-石墨炉原子吸收光谱法测定水样中的痕量铅

本文采用2-(5-溴-2-吡啶偶氮)-5-二乙氨基苯酚(5-Br-PADAP)为络合剂,辛醇为提取剂,提出了有机溶剂萃取-石墨炉原子吸收光谱测定水样中痕量铅的分析方法。对萃取和石墨炉升温条件进行了优化。在本实验条件下,方法的线性范围在0.5~5.0μg/L之间,检出限为0.067μg/L,相对标准偏差(RSD)为3.9%(n=7),回收率在89%~97%范围。本法与未经溶剂萃取的方法相比,线性斜率提高了约20倍。本法已用于环境水样中痕量Pb的测定,测定结果与ICP-MS的分析结果具有良好的一致性。     

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.