气相色谱法同时测定花生中12种有机磷农药残留量

建立了气相色谱法同时测定花生中12种有机磷农药残留量的方法.花生中有机磷农药残留通过乙腈提取,经液-液分配后有机相浓缩以丙酮定容,应用氮磷检测器(NPD)检测.除敌百虫和杀扑磷的检测限分别为20、50 μg/kg以外,其余10种有机磷农药检测限均为10 μg/kg.加标回收率为68.70%～108.45%,测定结果的相对标准偏差为3.05%～19.10%(n=5).该法与单独测定这12种有机磷农药的加标回收率和相对标准偏差基本符合.     

白菜中有机磷农药的电纺纳米纤维固相萃取-高效液相色谱法测定

以聚苯乙烯电纺纳米纤维为固相萃取介质填装固相萃取小柱,对白菜中的5种有机磷农药(杀扑磷、马拉硫磷、辛硫磷、丙溴磷、毒死蜱)富集净化,甲醇洗脱吸附在小柱上的农药后,用高效液相色谱-紫外检测器进行检测.对萃取次数、白菜样品提取液、洗脱液、pH值进行了优化,杀扑磷、马拉硫磷、辛硫磷、丙溴磷、毒死蜱在固相萃取小柱上的最大吸附量分别为2.9、3.5、5.6、3.7、7.8 mg/g,5种有机磷农药的平均加标回收率为68% ～97%,相对标准偏差为1.6% ～4.7%.测定喷洒5种农药后的白菜样品的萃取回收率为65% ～93%,相对标准偏差为1.6% ～4.0%,5种农药的检出限为0.02 ～0.1 mg/kg.该方法操作简单、价廉,能够用于白菜中有机磷农药的测定.     

GC-NPD同时测定中草药中有机磷和氨基甲酸酯农药残留量

建立了中草药中有机磷和氨基甲酸酯类农药残留量同时检测的气相色谱分析方法.中药材试样依据正交实验的优化条件,用V(C6H14):V(丙酮)=1:1混合提取剂进行超声波提取,经弗罗里硅土和中性氧化铝层析柱净化后,采用HP-5毛细管柱分离,氮磷检测器同时检测中草药中15种有机磷和7种氨基甲酸酯类农药残留量.22种农药在0.015～1.0 mg/L范围内线性良好,线性相关系数为0.9950～1.000,在0.05、0.1 mg/kg两个添加水平的平均回收率分别为70.6%～128.6%和69.5%～116.1%,相对标准偏差分别为0.98%～18%和0.37%～15%.各种农药的检出限为0.002～0.015 mg/L.方法已用于中草药中有机磷和氨基甲酸酯类农药残留量的同时检测.     

固相萃取-气质联用法测定啤酒中9种有机磷农药残留

建立啤酒中9种有机磷农药的固相萃取-气质联用分析方法.采用C18固相萃取小柱对啤酒中的有机磷农药进行提取、净化,用乙酸乙酯洗脱后供气相色谱-质谱分析,用基质匹配标准校正方法补偿基质效应.当添加浓度为50 μg/kg和100μg/kg时,平均回收率为80.3%～95.0%;测量结果的相对标准偏差为1.97%～8.28%(n=6);方法的检出限为1.20～15.3μg/kg.该方法可用于啤酒中痕量有机磷农药残留的测定.     

气相色谱-质谱法分析烟草中有机磷农药残留量及其烟支转移率研究

建立了一种用加速溶剂萃取,自动固相萃取净化,气相色谱/质谱联用检测烟草中29种有机磷农药残留量的方法.考察了加速溶剂萃取仪的萃取温度、溶剂、加热时间和循环次数对回收率的影响,对固相萃取的洗脱溶液及其体积和流速进行了优化,利用保留时间和定性离子定性,以灭蚁灵为内标进行定量,29种有机磷农药的平均回收率在61.4%～128%之间,相对标准偏差在12%以下,符合烟草中农药多残留检测的要求.通过对烟支进行加标,探讨了有机磷农药向主流烟气和烟蒂的转移情况,其向主流烟气的平均转移率为小于6.3%,相对标准偏差为8.0%～18.5%,而烟蒂平均截留率为0.3%～15.0%,相对标准偏差为6.5%～21.3%,表明有机磷农药有较小的转移,为卷烟安全性评价提供了可靠的数据.     

气相色谱-离子阱质谱法测定蔬菜中9种有机磷农药的残留量

建立气相色谱-离子阱质谱法测定蔬菜中9种有机磷农药残留的方法.样品经乙酸乙酯提取、无水硫酸钠脱水、活性炭小柱净化,浓缩后通过气相色谱-离子阱质谱进行测定.9种有机磷农药的浓度在0.05～1.0μg/mL范围内与其对应的色谱峰面积具有良好的线性关系(r＞0.999).在3个不同添加浓度下的平均回收率为76.5%～101.2%,测定结果的相对标准偏差为3.9%～9.4%(n=7).该方法快速、准确、操作简便,能满足蔬菜中有机磷农药残留的检测要求.     

微波辅助提取-气相色谱法同时测定中草药中有机磷和氨基甲酸酯农药残留

建立了中草药中有机磷和氨基甲酸酯类农药同时检测的气相色谱分析新方法.中药材试样依据正交实验的优化条件,用正己烷-丙酮(1∶4,V∶V)混合提取剂进行微波辅助提取,经弗罗里硅土和中性氧化铝混合层析柱净化后,采用HP-5毛细管柱分离,氮磷检测器同时检测中草药中15种有机磷和6种氨基甲酸酯类农药残留量.21种农药在0.01～1.0 mg/L的浓度范围内线性良好,线性相关系数为0.9950～1.000,检出限为0.002～0.01 mg/L.在0.05、0.2、0.5 mg/kg三个添加水平的平均回收率分别为75.11%～128.57%、75.85%～120.71%和76.43%～117.25%,相对标准偏差分别为 3.10%～10.58%、5.27%～9.94%和4.03%～9.03%.方法用于中草药中有机磷和氨基甲酸酯类农药残留的同时检测,结果良好.     

气相色谱-串联质谱法同时测定白芍中10种有机磷农药残留

建立了同时测定中药白芍中10种有机磷农药残留含量的气相色谱–串联质谱方法。样品用乙腈超声提取,提取液经凝胶渗透色谱净化后,以VF–5毛细管色谱柱(30 mm×0.25 mm,0.25μm)分离,串联四极杆质谱仪为检测器进行定性、定量分析。10种有机磷农药残留的检出限为0.02～4.0 mg/kg,实际样品的加标回收率为75%～105%,相对标准偏差为4%～10%。该方法能够满足白芍中有机磷农药残留的定性、定量检测要求。     

固相萃取-气相色谱法检测茶叶中的有机磷农药残留量

建立了茶叶中22种有机磷农药的残留量的气相色谱分析方法. 样品用V(乙腈)∶V(丙酮)＝4∶1提取, 经Envi-Carb固相小柱净化, 以V(乙腈)∶V(甲苯)＝3∶1洗脱, GC-FPD检测, 外标法定量. 在添加0.05～1.0 mg/kg的水平, 22种有机磷的平均回收率在81.3%～107.9%之间, 相对标准偏差在1.1%～8.9%, 该方法的检出限为0.01～0.04 mg/kg. 该方法的灵敏度、准确度和精密度均符合农药残留量测定的技术要求.     

气相色谱-负离子化学电离质谱法分析测定蔬菜水果中有机磷农药的残留

将气相色谱-负离子化学电离质谱法(GC-NCI-MS)应用于蔬菜水果中9种有机磷农药残留的分析测定,初步解析了这些农药的NCI-MS特征阴离子结构和断裂机理,并初步探讨了GC-NCI-MS分析蔬菜水果中有机磷农药残留时基体效应的影响。采用空白样品基体匹配校准曲线法(MC)进行定量分析,有效地降低了基体效应的影响。蔬菜水果样品用乙酸乙酯超声提取,以乙硫磷为内标物,采用GC-NCI-MS的选择离子监测方式(SIM)进行定性和定量分析。9种有机磷农药的方法检测限为0.12～1.0 μg/kg。在方法的检测限与1000 μg/kg范围内,线性相关系数都大于0.9993。当空白蔬菜水果(西红柿）样品的加标水平为100,400,800 μg/kg时,平均加标回收率为78%～126%,相对标准偏差为0.58%～14.7%。     

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.