固相萃取/液质联用测定竹笋中丁烯氟虫腈农药残留研究

建立了高效液相色谱-串联质谱(HPLC-MS/MS)测定竹笋中丁烯氟虫腈残留的分析方法。样品采用乙腈提取,经PSA固相萃取小柱净化后,采用Waters Atlantis T3色谱柱(2.1 mm×150 mm×5μm),以含5mmol/L乙酸铵的0.1%甲酸水溶液和乙腈为流动相梯度洗脱,电喷雾离子源负离子模式多反应监测(MRM)模式定性分析,以氟虫腈为内标物质内标法消除基质效应定量测定丁烯氟虫腈。该方法在5.0～100.0μg/L范围内具有良好的线性关系,相关系数大于0.994 8;4、8、32μg/kg 3个加标水平下的平均回收率为76%～103%,相对标准偏差(RSDs)为3.2%～9.9%;方法的检出限(信噪比S/N=3)和定量下限(S/N=10)分别为0.21μg/kg和0.69μg/kg。该方法较气相色谱法和气相色谱质谱联用法具有更高的准确性和灵敏度,且更加简单快速,可满足竹笋中丁烯氟虫腈农药残留的检测要求。     

气相色谱-三重四级杆质谱法测定禽蛋及蛋制品中氟虫腈残留量

建立固相萃取(SPE)–气相色谱–三重四级杆质谱(GC–MS–MS)法检测禽蛋及蛋制品中氟虫腈残留量的分析方法。样品采用乙腈提取,经固相萃取小柱净化,GC–MS–MS检测,基质匹配外标法定量。氟虫腈的质量浓度在0.01～0.10 mg/L范围内与色谱峰面积呈良好的线性关系,相关系数r大于0.999,方法的定量限(10S/N)为0.001 mg/kg。在0.01,0.02,0.10 mg/kg 3种浓度添加水平下,平均回收率为86.7%～109.8%,测定结果的相对标准偏差为4.8%～9.9%(n=6)。该方法准确、灵敏、简单、高效,适合禽蛋及蛋制品中氟虫腈残留的定性定量分析。     

小麦中多种农药的快速残留分析

建立了同时测定小麦中12种农药(灭线磷、甲拌磷、甲基毒死蜱、八氯二丙醚、马拉硫磷、毒死蜱、氟虫腈、杀扑磷、溴虫腈、三唑磷、联苯菊酯和甲氰菊酯)残留的快速分析方法.样品采用改进的QuEChERS进行前处理,用1%乙酸乙腈提取,C18和中性氧化铝双重净化后,结合GC-MS/SIM对小麦中的12种农药进行检测.结果表明,小麦中12种农药的加标水平为0.025 ～1.0 mg/kg时,平均回收率为76% ～108%,相对标准偏差为0.4% ～10.5%;方法的定量下限(S/N=10)为0.5 ～9.8 μg/kg,低于欧盟设定的MRLs值.     

气相色谱-三重四极杆质谱法测定鸡蛋中氟虫氰及其代谢残留

建立了QuEChERS快速提取和净化样品,气相色谱-三重四级杆质谱联用法测定鸡蛋中氟虫腈及其代谢物氟甲腈、氟虫腈砜、氟虫腈亚砜的方法。水和乙腈萃取、C_(18)和PSA净化样品,气相色谱分离,多反应离子监测模式测定。氟虫腈及其3种代谢物在5~400μg/L范围内线性关系良好,方法的检出限为1.0~2.5μg/kg;定量限为3.0~7.5μg/kg。在两个浓度水平进行加标,上述4种测定物的回收率为72.5%~95.3%,相对标准偏差为3.7%~7.5%。本方法可满足鸡蛋中氟虫腈及其代谢物氟甲腈、氟虫腈砜、氟虫腈亚砜残留检测的实际需要。     

气相色谱法测定水果和蔬菜中5种有机含磷农药的残留量

提出了用气相色谱-火焰光度检测器测定水果和蔬菜中甲基异柳磷、苯线磷、内吸磷、硫环磷和蝇毒磷等5种有机含磷农药残留量的方法。采用乙腈匀质提取样品中残留的有机含磷农药,提取液经石墨化炭黑粉末净化。用SPB-608毛细管色谱柱分离,气相色谱-火焰光度检测器法测定。方法的检出限(3S/N)在0.01～0.05mg·L-1之间。所测5种有机含磷农药的标准加入回收率在91.3%～110.0%之间,相对标准偏差(n=6)在1.5%～4.6%之间。     

QuEChERS-超高效液相色谱-串联质谱法测定动物源性食品中氟虫腈及其代谢物残留

建立了禽蛋、动物肌肉、内脏和蛋制品中氟虫腈及其代谢物氟甲腈、氟虫腈砜、氟虫腈亚砜的超高效液相色谱-串联质谱(UPLC-MS/MS)检测方法。在QuEChERS方法基础上,针对目标物化学性质和样品杂质情况,对提取溶液的种类、提取次数、净化材料等参数进行了优化。最终样品经乙腈提取,NaCl、无水MgSO_4盐析分层,提取液经PSA结合C_(18)进行分散固相萃取净化,以UPLC-MS/MS进行测定,基质外标法进行定量分析。结果表明,动物源性食品中氟虫腈、氟甲腈、氟虫腈砜、氟虫腈亚的平均加标回收率在75.7%~104.5%之间,相对标准偏差在1.3%~10.4%之间,检出限在0.5~1.6μg/kg之间,定量限为5.0μg/kg。此方法快速、简便、灵敏度高、准确,可用于禽蛋、动物肌肉、内脏和蛋制品中氟虫腈及其3种代谢物残留的同时测定。     

QuEChERS/GC-MS/MS测定人参中41种农药残留

建立了QuEChERS结合气相色谱-串联质谱(GC-MS/MS)测定人参中41种农药残留的分析方法,采用选择反应监测(SRM)模式,外标法定量,并考察了Original、Acetate和Citrate 3种QuEChERS前处理方法对人参基质中目标农药的提取效率和净化效果。结果表明,采用Original QuEChERS前处理方法时,41种农药在一定浓度范围内的线性良好,相关系数(r)大于0.995,方法的检出限(LOD,S/N=3)为2.0～6.0μg/kg,定量下限(LOQ,S/N=10)为5.0～20.0μg/kg。在10、20、100、200μg/kg 4个加标水平下的回收率为86.7%～115%,相对标准偏差(RSD)均小于15%。该方法样品前处理简单、高效、准确、灵敏,适用于人参中多农药残留的筛选与测定。     

固相萃取-液相色谱-四极杆飞行时间质谱法快速筛查禽蛋及蛋制品中氟虫腈及其代谢物

建立了液相色谱-四极杆飞行时间质谱(LC-QTOF MS)测定禽蛋及蛋制品中氟虫腈及其代谢物的快速筛查方法。样品经酸性乙腈提取,PRiME HLB SPE柱净化,Poroshell 120 EC C18色谱柱(150 mm×3 mm,2.7μm)分离,以水-乙腈为流动相,梯度洗脱,负离子模式下测定,以乙虫腈为内标定量。实验中建立了一级精确质量和二级碎片离子质谱数据库,并且对4种禽蛋及蛋制品的基质效应进行了考察。结果表明,氟虫腈及其代谢物在0.1~5μg/L范围内线性关系良好,相关系数(r2)均大于0.99。方法的检出限(LOD,S/N3)和定量限(LOQ,S/N10)分别为0.2μg/kg和1μg/kg。在不同基质中,氟虫腈及其代谢物在1、2和5μg/kg的添加水平下平均加标回收率为82.6%~98.1%,相对标准偏差为3.8%~9.9%(n=6)。该方法有效消除了液相色谱-四极杆飞行时间质谱检测过程中的离子化抑制效应,灵敏度和准确度高,适用于鸡蛋、鸡蛋面、蛋糕和蛋黄酱中氟虫腈、氟虫腈砜、氟虫腈亚砜和氟甲腈的快速筛查。     

微波辅助萃取-气相色谱法测定茶叶中的有机磷农药

建立了微波辅助萃取–气相色谱法测定茶叶中甲胺磷、乐果、毒死蜱、水胺硫磷、三唑磷5种有机磷农药残留量的分析方法。样品用乙酸乙酯微波辅助提取,提取液经分散固相萃取法(DSPE)净化,用气相色谱配FPD检测器测定,外标法定量。结果表明农药混合标准溶液在0.01～0.5μg/mL范围内线性良好(r>0.999),方法的检出限为0.005～0.01 mg/L,在0.05,0.125,0.5μg/mL 3个水平添加平均回收率为63.3%～99.9%,测定结果的相对标准偏差为5.1%～8.2%(n=6)。该方法适合于茶叶中多种有机磷农药残留量的同时检测。     

毛细管气相色谱法测定韭菜中13种有机磷农药残留的研究

建立了毛细管气相色谱法测定韭菜中敌敌畏、甲胺磷、乙酰甲胺磷、甲拌磷、氧化乐果、久效磷、乐果、毒死蜱、甲基对硫磷、马拉硫磷、杀螟硫磷、对硫磷和喹硫磷等13种有机磷农药残留的新方法.考察了进样口压力和程序升温速率对色谱分离的影响.试样用乙腈提取,经毛细管气相色谱柱DB-1701(30 m×0.32 mm×0.25 μm)分离,FPD检测器测定.当进样口压力为68.9 kPa,程序升温速率为5 ℃/min时,13种有机磷农药与韭菜基质在30 min内获得有效分离.添标水平为0.05、0.2 mg/kg时的平均回收率为78% ～115%,相对标准偏差为2.6% ～10.7%,方法检出限(S/N=3)为0.01 ～0.03 mg/kg,符合农药多残留定性、定量分析技术的要求.     

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%.     

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.     

α-Amino acid derived enaminones and their application in the synthesis of N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates and other heterocycles

A new and simple synthesis of novel N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates, which exist in equilibrium with their 4-oxo tautomers, has been developed in two steps starting from N-protected α-amino acids. The key intermediates are enaminones, which can also be isolated, characterized, and used for the construction of other functionalized heterocycles, before they spontaneously decompose to pyrrole products. 4-Hydroxypyrroles are prone to partial aerial oxidation but can be efficiently alkylated or reduced to stable polysubstituted pyrrolidine derivatives.     

Specific intramolecular aromatic CH insertion of diazosulfonamides

The chemoselectivity in the intramolecular CH insertion of various diazosulfonamides has been experimentally studied. The results reveal that the aliphatic 1,4-, 1,5-, or 1,6-C(sp³)?H insertions of diazosulfonamides are not accessible, while the aromatic 1,5-C(sp²)?H insertion can be realized specifically by adjusting the diazo-adjacent group. In addition, the general chemoselectivities in the intramolecular CH insertions of diazosulfonyl compounds are summarized. Generally, diazosulfones undergo both aromatic 1,5-C(sp²)?H and aliphatic 1,5- and 1,6-C(sp³)?H insertions, while diazosulfonates undergo aliphatic 1,5- and 1,6-C(sp³)?H insertions. However, diazosulfonamides only undergo aromatic 1,5-C(sp²)?H insertion.     

A general and convenient synthesis of 4-(tosylmethyl)semicarbazones and their use in amidoalkylation of hydrogen,heteroatom, and carbon nucleophiles

A general synthesis of previously unknown semicarbazone-based α-amidoalkylating reagents, 4-(tosylmethyl)semicarbazones, has been developed. The synthesis involved three-component condensation of semicarbazones of aliphatic or aromatic aldehydes with the same or other aldehydes and p-toluenesulfinic acid. The scope and limitations of this reaction were investigated. The compounds obtained were demonstrated to be an efficient α-(4-semicarbazono)alkylating agents. They were reacted with H- (sodium borohydride), O- (sodium methylate), S- (sodium phenylthiolate), N- (pyrrolidine, sodium succinimide), P- (trialkyl phosphites), and C-nucleophiles (sodium diethyl malonate) to give the corresponding products of the tosyl group substitution, 4-substituted semicarbazones, including analogues of nitrofurazone. Among the prepared compounds tested in vitro for antibacterial and antifungal activity, three nitrofuryl-containing semicarbazones exhibited high biological activities with minimum inhibitory concentration (MIC) values of 8–32 μg/mL.     

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.     

Synthesis of novel chiral bidentate hydroxyalkyl-N-heterocyclic carbene ligands and their application in palladium-catalyzed Mizoroki–Heck couplings and asymmetric addition of diethylzinc to benzaldehyde

A small library of new chiral bidentate hydroxyalkyl-imidazolium salts 1 is conveniently synthesized on multi-gram scale from inexpensive and commercially available chiral pool amino acids. The corresponding carbenes, generated by deprotonation of imidazolium salts 1, in combination with palladium(II) chloride were tested in the Mizoroki–Heck coupling reaction. The most significant results in terms of yields and reactivities were achieved with low catalyst loading. The catalytic activities of these imidazolium salts were also investigated in the asymmetric addition of diethylzinc to benzaldehyde. The use of MgO nanoparticles as an additive in conjunction with these ligands played a crucial role in increasing the efficiency of these reactions.     

N-Heterocyclic carbene-palladacyclic complexes: synthesis,characterization and their applications in the C-N coupling and α-arylation of ketones using aryl chlorides

N-Heterocyclic carbene-palladacyclic complexes 3 were successfully achieved in a one-pot procedure under mild conditions. The structure of 3a was unambiguously confirmed by X-ray single crystal diffraction and it was an active catalyst in the Buchwald-Hartwig amination and α-arylation of ketones even at very low catalyst loadings (0.01?mol%).     

Iodine-mediated oxidative Pictet-Spengler reaction using terminal alkyne as the 2-oxoaldehyde surrogate for the synthesis of 1-aroyl-β-carbolines and fused-nitrogen heterocycles

An efficient iodine-mediated oxidative Pictet-Spengler reaction in dimethyl sulphoxide (DMSO) using terminal alkynes as the 2-oxoaldehyde surrogate for the synthesis of aryl (9H-pyrido[3,4-b]indol-1-yl)methanones is described. The scope of the protocol includes the total synthesis of Fascaplysin, Eudistomins Y₁ and Y₂. The methodology is extended for preparing pyrrolo[1,2-a]-quinoxaline and indolo[1,5-a]quinoxaline derivatives. The utility of 1-aroyl-β-carbolines was demonstrated by performing palladium-catalyzed β-carboline directed ortho-C(sp2)-H functionalization of the phenyl ring with thiomethyl (SMe) group using DMSO as source and for accessing 4-aryl-canthin-6-ones.     

Facile synthesis of bicyclic 1-arylpyrazol-5-ones

In this Letter, we described a facile method for constructing fused bicyclic 1-arylpyrazol-5-one ring system. We employed various methylene-containing carboxylic acids as the substrates and proved that the pyrazolone ring closure requires activated methylene group in intermediate II. Accordingly, a series of structurally diversified, fused bicyclic 1-arylpyrazol-5-ones was prepared in moderate to high yields using the requisite substrates.