流动注射法同时测定海水中氨氮和磷酸盐

采用流动注射法同时测定海水中氨氮和磷酸盐的含量。在优化的试验条件下,氨氮和磷酸盐的线性范围分别为0.25 mg·L-1和0.30 mg·L-1以内,检出限(3S/N)分别为0.42μg·L-1和0.56μg·L-1。氨氮和磷酸盐加标回收率分别在85.0%~103%和86.7%~103%之间,测定值的相对标准偏差(n=6)分别在0.43%~5.3%和0~4.1%之间。方法用于分析标准物质,测定结果与分光光度法的结果一致。     

顶空-气相色谱-质谱法测定地表水和废水中55种挥发性有机物含量

采用顶空-气相色谱-质谱法测定地表水和废水中55种挥发性有机物的含量。选择顶空平衡温度和时间分别为65℃和50min。在气相色谱分离中用DB-624色谱柱为固定相,在质谱分析中采用全扫描和选择离子监测模式。以氟苯和1,2-二氯苯-D4为内标物。55种挥发性有机物的线性范围均为10.0~400μg·L-1。全扫描模式下,检出限在0.8~6.8μg·L-1之间,加标回收率在81.3%~116%之间,测定值的相对标准偏差(n=6)在0.40%~15%之间。在选择离子监测模式下,检出限在0.2~1.1μg·L-1之间,加标回收率在81.0%~117%之间,测定值的相对标准偏差(n=6)在0.40%~6.5%之间。     

气相色谱-串联质谱法测定烟草中97种农药残留量

利用气相色谱-串联质谱法(GC-MS/MS)检测烟草中97种农药残留。样品以乙腈为溶剂经加速溶剂萃取(ASE),提取液用Carbon-NH2固相萃取小柱净化后,采用VF-5MS色谱柱分离,用电子轰击离子源-多反应监测模式(EI-MRM)检测。97种农药的质量浓度在20~1 000μg·L-1范围内与其峰面积呈线性关系,方法的测定下限(10S/N)在0.02~22.4μg·kg-1之间;在50,100,500μg·kg-1的加标水平下,测得回收率在67.4%~116%之间,测定值的相对标准偏差(n=6)在1.9%~14%之间。     

亲水作用色谱分离-高效液相色谱法测定烟草不同部位中烟碱的含量

提出了亲水作用-高效液相色谱法测定不同烟草部位中烟碱含量的方法。采用Atlantis HILIC色谱柱(150mm×4.6mm,5μm)分离,以乙腈、10mmol·L-1乙酸铵溶液和冰乙酸以体积比72比28比2组成的混合液为流动相,在检测波长260nm处进行测定。烟碱的质量浓度在0.001~0.1g·L-1范围内与峰面积呈线性关系,方法检出限(3S/N)为0.17mg·L-1。进行3个浓度水平的加标回收试验,测得回收率在98.2%~98.9%之间,相对标准偏差(n=6)小于2.0%。从烟草的不同部位取样,按本法分析,结果表明:其烟碱含量从烟叶的上部、中部、下部至烟梗逐渐减少。     

原子荧光光谱法测定新疆薰衣草中的铅、砷和汞

采用原子荧光光谱法对新疆不同产地薰衣草样品中的铅、砷和汞3种重金属元素的含量进行了测定。结果表明,测定薰衣草中的铅、砷和汞元素的线性范围分别在0.1~20μg·L-1、0.5~50μg·L-1和0.1~10μg·L-1之间,检出限分别为0.05μg·L-1、0.03μg·L-1和0.05μg·L-1,相对标准偏差(RSD)≤3.03%(n=6),各元素的加标回收率在97.0%~103.0%之间。该方法快速、简便、数据准确可靠。     

改进的重铬酸盐法测定水和废水中化学需氧量

对重铬酸盐法测定水和废水中化学需氧量的国家标准方法作了改进。改进方法较原方法的取样量由20.00mL减少为10.00mL,氯离子掩蔽剂硫酸汞由固体改为溶液;改进方法受氯离子干扰的程度与国标方法相似,当氯离子质量浓度小于1 000mg·L-1时对测定结果无影响。改进方法的检出限为3 mg·L-1,对标准物质和标准溶液进行测定,测定结果的相对误差在0.96%~2.70%之间,标准偏差在0.80~5.6 mg·L-1之间,相对标准偏差(n=6)在0.80%~5.9%之间。方法应用于水样的测定,测定值与国标法测定值相符,测定值的标准偏差在0.94~20.5mg·L-1之间,相对标准偏差(n=6)在0.53%~11%之间。     

气相色谱-质谱法测定酒中16种邻苯二甲酸酯

应用气相色谱-质谱法测定酒中16种邻苯二甲酸酯的含量。样品经乙酸乙酯提取,所得提取液用DB-5MS UI色谱柱分离,在全扫描/选择离子监测共用模式下测定。16种邻苯二甲酸酯的质量浓度均在0.5~10.0mg·L-1范围内与其峰面积呈线性关系,方法的检出限(3S/N)在0.01~0.10mg·L-1之间。日间加标回收率在83.7%~114%之间,日间相对标准偏差(n=6)在3.4%~9.8%之间;日内加标回收率在81.9%~113%之间,日内相对标准偏差(n=6)在1.5%~6.7%之间。     

气相色谱-硫化学发光检测器法测定车用汽油中6种硫醚

采用气相色谱测定车用汽油中6种硫醚的含量。用DB-1毛细管色谱柱(60 m×0.32mm,0.50μm)分离和硫化学发光检测器检测。6种硫醚的质量浓度均在0.5~150mg·L-1范围内与其峰面积呈线性关系,方法的检出限(3S/N)在0.03~0.26mg·kg-1之间。方法用于车用汽油的分析,加标回收率在76.6%~120%之间,测定值的相对标准偏差(n=7)在0.50%~6.4%之间。     

动态反应池-电感耦合等离子体质谱法测定烟草中的砷

建立了一种测定烟草中痕量砷的电感耦合等离子体质谱(ICP-MS)分析方法。样品用硝酸-过氧化氢经微波消解前处理后,采用ICP-MS动态反应池模式,以氧气为反应气,通过测定75 As16 O+对砷进行定量。砷的质量浓度在20μg·L-1范围内呈线性,方法的检出限(3S/N)为39ng·L-1。方法用于烟叶样品分析,加标回收率在95.3%~105%之间,测定值的相对标准偏差(n=7)小于5.0%。     

离子色谱法同时测定不同时段酸雨中17种离子

应用离子色谱法同时测定不同时段酸雨中17种离子的含量。样品经离心沉淀后,经0.45μm滤膜过滤,滤液供离子色谱分析。阴离子分离时用Shodex SI-52 4E阴离子色谱柱,并用3.6mmol·L-1碳酸钠-0.6 mmol·L-1碳酸氢钠缓冲溶液作为淋洗液;阳离子分离时用TSKGEL阳离子色谱柱,并用2mmol·L-1硝酸溶液作为淋洗液,采用电导检测器进行检测。17种离子均在一定的质量浓度范围内与其峰面积呈线性关系,方法的检出限(3S/N)在1.4~18.7μg·L-1之间。回收率在95.0%~105%之间,测定值的相对标准偏差(n=6)在1.7%~7.2%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%.     

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.     

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.     

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.     

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.     

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.