气相色谱-串联质谱同位素内标法测定中草药中124种农药及其代谢物残留

建立测定中草药中124种农药及其代谢物残留的气相色谱-串联质谱(GC-MS-MS)方法。采用同位素内标法,样品经乙腈提取,采用混合型固相分散萃取剂净化,加入分析保护剂校正基质效应。色谱柱为DB-5MS(30 m×0.25 mm×0.25μm),程序升温,GC-MS-MS测定。124种农药残留在0.005~0.40μg/m L内呈线性关系,在0.06~0.3 mg/kg内的平均回收率为84.8%~108.7%,RSD为2.1%~12%,方法检出限(LOD)为0.005~0.013 mg/kg。该方法适合于中草药中农药多残留的同时检测。     

改良的QuEChERS-气相色谱-质谱联用法测定茶叶中多种农药残留

建立了以QuEChERS作为前处理方法,气相色谱/质谱联用法同时测定茶叶中33种农药残留的检测方法。样品经改进的QuEChERS法进行提取净化,采用DB-5MS(30m×0.25mm×0.25μm)毛细管色谱柱分离,选择离子模式下同时测定,外标法定量。33种农药残留在0.01~3.00mg/L范围内线性关系良好,相关系数均大于0.999。方法的检出限为4.0~35μg/kg,样品平均添加回收率为82.7%~103.8%,相对标准偏差为0.73%~6.8%。方法适用于茶叶中毒死蜱、联苯菊酯等33种不同类型农药残留的同时检测。     

气相色谱-火焰光度法测定土壤中有机磷农药残留

建立了气相色谱-火焰光度(GC-FPD)分析土壤中敌敌畏、氧化乐果、二嗪农、乐果、甲基对硫磷、马拉硫磷、对硫磷、水胺硫磷、喹硫磷等9种有机磷农药残留量的方法。样品用丙酮-二氯甲烷(1:3)提取,浓缩、定容后用Hp-5MS(30m×0.25 mm×0.25μm)毛细管柱分离,FPD检测器检测。方法回收率在68.71%～110.39%之间;RSD在5.5%～11%之间;检出限在0.397～1.60μg/mL之间,方法可用于环境土壤样品中有机磷农药残留的测定。     

固相萃取-毛细管柱-气相色谱法测定水中11种有机磷农药

提出了固相萃取分离-毛细管柱-气相色谱法测定水中11种有机磷农药的方法。水样经Waters oasis HLB固相萃取小柱分离并净化,甲醇-丙酮(70+30)混合液洗脱。用Varian cp-sil24CB色谱柱(30m×0.25mm,0.25μm)分离,脉冲火焰光度检测器检测。11种有机磷农药的质量浓度均在5.00μg·L-1以内与其峰面积呈线性关系,测定下限(10S/N)在0.03~0.05μg·L-1之间。方法用于地表水样和饮用水样分析,加标回收率在65.7%~124%之间,测定值的相对标准偏差(n=6)在1.8%~9.9%之间。     

气相色谱-质谱法测定纺织品中22种农药残留

提出了气相色谱-质谱法测定纺织品中22种农药残留量的方法。样品以正己烷-丙酮(1+1)混合溶液为提取剂,经加速溶剂萃取仪提取后,在40℃旋转蒸发仪中浓缩、氮气吹干后,用正己烷-丙酮(1+1)混合溶液溶解定容至2.0 mL,通过Agilent HP-5MS石英毛细管色谱柱(30m×0.25mm,0.25μm)分离,采用电子轰击离子源选择离子监测模式进行质谱测定。22种农药的检出限(3S/N)在0.003～0.03mg·kg-1之间。以空白棉布样品为基体,加入标准溶液进行回收试验,测得回收率在80.1%～95.9%之间,相对标准偏差(n=6)均小于13%。     

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。     

土壤中多种有机磷及氨基甲酸酯类农药残留量的气相色谱-质谱法测定

建立了气相色谱-质谱法测定土壤中12种有机磷和氨基甲酸酯类农药残留分析方法。以丙酮-石油醚(4∶1,V/V)为提取剂,采用超声波提取土壤中农药残留,经弗罗里土层析柱净化,气相色谱-质谱(选择离子模式)法同时测定了土壤中多种有机磷和氨基甲酸酯类农药。该法对0.1μg/mL和0.5μg/mL两个浓度添加水平的回收率分别为70.1%~119.0%和78.1%~119.1%,相对标准偏差分别为6.30%~9.80%和5.20%~8.23%。     

悬浮固化-分散液液微萃取-气相色谱法测定野木瓜中9种有机氯农药残留量

建立了悬浮固化-分散液液微萃取-气相色谱法测定野木瓜中9种有机氯农药残留量的方法。样品经石油醚提取、浓硫酸净化、悬浮固化-分散液液微萃取法浓缩后,用气相色谱-电子捕获检测器(GC-ECD)检测,外标法定量。结果表明,9种农药含量在1~100μg/L范围内线性关系良好,相关系数R2在0.99以上,方法检出限(S/N=3)为0.01~0.07μg/kg。9种有机氯农药在1.75,7.00,28.0μg/kg 3个水平添加下,平均回收率范围为83.3%~116.7%,相对标准偏差(RSD)范围为1.5%~14%,方法已用于野木瓜中9种有机氯农药残留的测定。     

分散液液微萃取-气相色谱-质谱法测定鱼塘水中24种农药

采用分散液液微萃取结合气相色谱-质谱法同时快速测定鱼塘水中24种常见农药。在水样5.00mL中快速加入乙醇1.0mL、四氯乙烯30μL,形成乳浊液,静置5min后,以4 000r·min~(-1)转速离心5min,有机相在VF-5MS毛细管色谱柱上分离,质谱分析中选择电子轰击离子源和选择离子监测模式。24种农药的质量浓度在一定范围内与峰面积呈线性关系,检出限(3S/N)在0.33~7.45μg·L~(-1)之间。加标回收率在72.4%~103%之间,测定值的相对标准偏差(n=6)在1.7%~13%之间。该方法成功应用于鱼塘投毒案件中硫丹α、硫丹β和甲氰菊酯的检测。     

液液萃取分离-气相色谱-串联质谱法同时测定水中12种有机氯农药

采用液液萃取分离-气相色谱-串联质谱法同时测定水中12种有机氯农药的含量。样品经正己烷提取,在气相色谱分离中用DB-5MS色谱柱为固定相,在质谱分析中采用多反应监测模式。12种有机氯农药在一定的质量浓度范围内与其峰面积呈线性关系,方法的检出限在0.002~0.032μg·L~(-1)之间,测定下限在0.008~0.128μg·L~(-1)之间。以空白样品为基体进行加标回收试验,所得回收率在99.1%~126%之间,测定值的相对标准偏差(n=7)在2.3%~9.3%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%.     

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.