毛细管气相色谱法测定沉香中20种有机氯农药残留量

应用毛细管气相色谱法测定沉香中20种有机氯农药的残留量。样品以乙酸乙酯提取,提取液用凝胶色谱-固相萃取(GPC-SEP)进行净化。采用DB-1701P石英毛细管色谱柱(30m×0.25mm,0.25μm)分离样品,电子捕获检测器进行检测。20种有机氯农药的线性范围均为1~50μg·L-1,检出限均为0.1μg·kg-1。方法用于沉香样品分析,加标回收率在95.8%~114%之间,测定值的相对标准偏差(n=6)在0.3%~3.8%之间。     

加速溶剂提取-气相色谱法测定土壤中3种有机磷和9种有机氯农药

提出了气相色谱法测定土壤中3种有机磷和9种有机氯农药含量的方法。样品经粉碎后用正己烷-丙酮(1+1)混合溶剂经加速溶剂萃取仪在60℃静态萃取10min。采用Rtx-1701色谱柱分离,火焰光度检测器测定3种有机磷农药;采用Rtx-CLPⅡ色谱柱分离,电子捕获检测器测定9种有机氯农药。12种有机农药的质量浓度均在5.0～80μg·L-1范围内呈线性,方法的检出限(3s)在0.02～0.40μg·kg-1之间。以空白石英砂样品为基体,进行加标回收试验,回收率在78.5%～108%之间,相对标准偏差(n=7)在4.2%～9.9%之间。     

毛细管气相色谱法测定三九胃泰中20种有机氯农药残留量

提出了毛细管气相色谱法测定"三九胃泰"中20种有机氯残留量的方法。样品经正己烷提取,所得提取液经硫酸磺化。采用DB-1701P色谱柱(30m×0.25mm,0.5μm),在100℃～250℃温度区间采用程序升温方式进行分离,用电子捕获检测器测定。20种有机氯农药的检出限(3S/N)均为10μg·kg-1。用标准加入法测得回收率在70.2%～117%之间,相对标准偏差(n=6)在1.0%～1.8%之间。     

气相色谱法测定土壤中21种有机氯农药和4种有机磷农药

应用气相色谱法测定土壤中21种有机氯农药和4种有机磷农药(OCP′s及OPP′s)的含量。土壤样品(10g)以丙酮-正己烷(1+1)混合液(200mL)在65℃用索氏提取7h。提取液蒸缩至约2mL,用经固相萃取小柱净化。用上述混合液6mL分3次从柱上洗脱,洗脱液浓缩至1mL供气相色谱分析。测定OCP′s时用CLPⅡ型毛细管色谱柱分离,电子捕获检测器检测;测定OPP′s时用1701型毛细管色谱柱分离,火焰光度检测器检测。21种OCP′s和4种OPP′s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0.14~0.38μg·kg-1之间。加标回收率在68.0%~125%之间,测定值的相对标准偏差(n=10)在2.8%~5.9%之间。     

气相色谱法测定黄芪饮片中有机氯类农药残留

采用气相色谱电子捕获检测器(ECD)测定黄芪饮片中9种有机氯类农药残留。黄芪饮片样品以丙酮、二氯甲烷提取,浓硫酸磺化,采用HP–5(30 m×0.32 mm,0.25μm)色谱柱,气化室温度为250℃,检测器温度为300℃。以标准曲线法计算农药含量,加标回收率为94.5%~104.4%,测定结果的相对标准偏差为1.7%~2.7%,检出限为0.061~0.175 ng/m L。该方法简单、快速、稳定、可靠,可用于黄芪饮片中9种有机氯类农药残留的测定。     

加速溶剂萃取-气相色谱法测定土壤中三种有机磷农药和除草剂莠去津

提出了气相色谱法测定土壤中莠去津和3种有机磷农药敌敌畏、甲拌磷和乐果的含量的方法。样品经粉碎后用丙酮-二氯甲烷(1+1)混合溶剂经加速溶剂萃取仪在60℃静态萃取10min。采用Rtx-1701色谱柱分离,火焰光度检测器测定3种有机磷农药;采用Rtx-CLP II色谱柱分离,电子捕获检测器测定莠去津。结果表明:加速溶剂萃取比超声提取法处理样品的回收率高。敌敌畏、甲拌磷、乐果和莠去津的检出限(3S/N)分别为0.08,0.07,0.09,0.40μg.kg-1。以空白土壤样品为基体,进行加标回收试验,回收率在82.0%～106.0%之间,相对标准偏差(n=7)在10.5%～16.9%之间。     

气相色谱法快速测定茶浓缩汁中10种有机膦农药的残留量

用二氯甲烷提取样品中残留的10种有机膦农药(OPhP's),所得萃取液用无水硫酸钠脱水后,在35℃和0.006 MPa的条件下经旋转蒸发至干,用二氯甲烷2.00 mL溶解残渣,此溶液毋需净化直接进样用气相色谱法进行测定.测定中采用DB-1701、RTX-5双毛细管色谱柱和双火焰光度检测器,10种农药的检出限(3S/N)在3～10μg·L-1之间.用标准加入法在3个浓度水平上对方法的回收率及精密度作了试验,求得其回收率在83.3%～112.6%之间,相对标准偏差(n=8)在3.4%～6.9%之间.     

气相色谱法测定胰酶中的丙酮溶剂残留量

采用气相色谱测定了胰酶中残留的丙酮溶剂,并通过外标法定量分析其含量。气相色谱条件为:氢火焰离子化检测器(FID),DMF作为溶剂,DM-WAX色谱柱(30 m×0.53 mm×1μm),载气为氮气,进样口温度为200℃,检测器温度为300℃,柱温采取程序升温。气相色谱法检测丙酮的加标回收率为92.5%～98.0%,检出限(3S/D)为0.05μg/mL。     

顶空固相微萃取-气相色谱-质谱法测定蔬菜及水果中15种农药残留量

应用顶空固相微萃取-气相色谱-质谱法测定蔬菜及水果中15种农药的残留量。样品用顶空-固相微萃取进行前处理。经优化的试验条件:1采用100μm聚二甲基硅氧烷萃取头;2离子浓度:样品匀浆液中含(w)30%氯化钠;3萃取温度为70℃±1℃;4萃取时间为30min。在气相色谱分离中用HP-5MS色谱柱,在质谱分析中采用全扫描和选择离子监测模式。15种农药的质量浓度均在0.05~1.0mg·L-1范围内与其峰面积呈线性关系,方法的检出限(3S/N)在0.02~0.10μg·kg-1之间。以2种果品作基体,在0.05,0.2,0.5mg·kg-1 3个浓度水平进行加标回收试验,测得回收率在71.0%~96.0%之间,测定值的相对标准偏差(n=5)在0.5%~9.8%之间。     

气相色谱-串联质谱法测定生姜中25种农药残留量

采用气相色谱-串联质谱法测定生姜中25种农药的残留量。样品用乙腈提取,过NH2/Carbon固相萃取柱净化,将淋出液浓缩后用正己烷-丙酮(9+1)溶液定容。通过VF-5MS色谱柱分离,串联质谱测定。25种农药的质量浓度在0.020～0.500mg.L-1范围内与其峰面积均呈线性关系,检出限(3S/N)在0.2～10.0μg.kg-1之间。加入两个浓度水平的农药标准溶液进行了回收试验,多数农药的回收率在77%～130%之间,相对标准偏差(n=5)均小于20%。     

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.