基质固相分散-超高效液相色谱-串联质谱法检测蔬菜中残留的苯甲酰脲类和双酰肼类杀虫剂

建立了基质固相分散技术结合超高效液相色谱-串联质谱(UPLC-MS/MS)测定蔬菜中苯甲酰脲类杀虫剂(除虫脲、灭幼脲、杀铃脲、氟苯脲、氟虫脲、氟啶脲、氟铃脲)和双酰肼类杀虫剂(甲氧虫酰肼、虫酰肼)的方法。蔬菜样品经中性氧化铝和石墨化炭黑研磨,乙酸乙酯淋洗,洗脱液浓缩定容后,经超高效液相色谱分离,分别在正、负离子多反应监测(MRM)模式下用电喷雾电离串联质谱测定,外标法定量。结果表明,9种杀虫剂在1～100 μg/L质量浓度范围内有良好的线性关系(R2≥0.99);在1、5、10、100 μg/kg 4个加标水平上的回收率为78.5%～112.8%;相对标准偏差为2.3%～10.2%,检出限为0.5～1.0 μg/kg。该方法操作简便快速,样品和溶剂用量少,检出限低,可满足蔬菜中苯甲酰脲类和双酰肼类杀虫剂同时检测的要求。     

小白菜中残留虫酰肼的超临界流体萃取条件的研究

将超临界流体萃取(supercritical fluid extraction,SFE)技术与高效液相色谱分析相结合,建立了特异性杀虫剂虫酰肼的萃取分离方法。SFE对虫酰肼的萃取条件:压力48.3 MPa(7000 psi),温度60 ℃,静态萃取时间20 min,CO2体积10 mL,改性剂甲醇添加量0.04 mL/g,丙酮为收集溶剂。在此条件下,SFE对虫酰肼的萃取率为100.75%,所得样品可直接用于高效液相色谱分析。色谱条件：紫外-二极管阵列检测器(检测波长为245 nm),C18键合色谱柱,乙腈     

高效液相色谱-串联质谱法测定葱中5种双酰肼农药残留

建立了同时分析葱中5种双酰肼农药的高效液相色谱-串联质谱方法。样品经乙腈高速匀浆提取,盐析后浓缩,弗罗里硅土柱色谱净化,采用液相色谱-串联质谱分析5种化合物。质谱分析采用电喷雾电离,正离子扫描,多反应监测模式。对双酰肼农药主要碎片的裂解方式进行了剖析。实验证明,柱净化后无明显的基质效应,样品中添加0.002～0.2 mg/kg的5种双酰肼,其回收率为72.6%～95.5%,相对标准偏差(n=5)小于15%;检出限为0.5 μg/kg,定量限为2 μg/kg。该方法提取效果好,具有良好的灵敏度、回收率和重复性。     

QuEChERS-高效液相色谱法检测蔬菜中的吡虫啉、虫酰肼、阿维菌素和噻螨酮

将一种新的QuEChERS样品处理方法进行了提取及净化的改进,结合HPLC对蔬菜中吡虫啉、虫酰肼、阿维菌素和噻螨酮4种农药进行同时检测,取得了满意结果。以乙腈-水为流动相,梯度洗脱,269、240 nm双波长检测,流速1.0 mL/min。检出限分别为:吡虫啉0.02 mg/kg、虫酰肼0.02 mg/kg、阿维菌素0.10 mg/kg、噻螨酮0.05 mg/kg。在添加浓度为0.05~1.0 mg/kg范围内,4种化合物回收率在80%~100%之间,相对标准偏差1%~10%。方法适用于蔬菜中吡虫啉、虫酰肼、阿维菌素和噻螨酮4种农药残留量的同时检测。     

马铃薯中马来酰肼的高效液相色谱法测定

建立了马铃薯中马来酰肼的高效液相色谱(HPLC)检测方法.马铃薯样品经酸化甲醇提取,高速离心沉淀分离后,以甲醇-去离子水(体积比1:9,pH 2.7)为流动相,采用ZORBAX SB C18柱(250 mm×4.6 mm×5 μm)分离,在UV 205 nm检测,外标法定量.结果表明,马来酰肼提取液的线性范围为0.2 ～16.0 mg/L,回收率为82% ～94%,RSD均小于2%,马铃薯中马来酰肼的定量下限为1.0 mg/kg.     

液相色谱-串联质谱法测定柑橘中虫酰肼残留量

提出了液相色谱-串联质谱法测定柑橘中虫酰肼残留量的方法。样品用1%(体积分数,下同)乙酸-乙腈溶液先后提取2次,提取液定容为25mL。分取8.0mL经N-丙基乙二胺(PSA)和十八烷基硅烷(ODS)键合相净化,取所得净化液5.00mL,在60℃氮气吹至近干后供液相色谱-串联质谱分析。0.1%乙酸-乙腈溶液定容至1mL。以ACQUITY UPLC BEH C18色谱柱为分离柱,以不同体积比混合的0.1%乙酸溶液和乙腈为流动相梯度洗脱,采用电喷雾正离子源模式多反应监测检测。方法的测定下限(10S/N)为0.005mg.kg-1。以空白柑橘样品为基体进行加标回收试验,所得回收率在77.1%～90.1%之间,相对标准偏差(n=5)均小于13%。     

高效液相色谱-串联质谱法测定大豆与玉米中的苯甲酰脲类农药残留

建立了大豆和玉米中苯甲酰脲类农药的反相高效液相色谱-电喷雾串联质谱(LC-ESIMS/MS)检测方法。样品经含0.1%乙酸的乙腈提取、浓缩,阳离子固相萃取柱净化,液相色谱串联质谱测定。9种苯甲酰脲类农药在5.0～200μg/L范围内线性关系良好(r20.995)。在大豆和玉米基质中的检出限均为3.0μg/kg,定量下限均为10.0μg/kg。在10.0、20.0、50.0μg/kg 3个加标水平下,9种苯甲酰脲类农药的回收率为46%～92%,精密度(RSD)小于14%。方法准确、灵敏、简单,适用于大豆和玉米中9种苯甲酰脲类农药残留的同时测定。     

亲水作用液相色谱-串联质谱测定烟叶中马来酰肼及其糖苷

建立了一种基于亲水作用液相色谱-串联质谱的烟叶中马来酰肼及其糖苷的定量分析方法。方法采用乙腈-甲基叔丁基醚-水（7：10：13,体积比）超声波辅助提取烟叶中的马来酰肼及其糖苷,提取液经离心分相和溶剂置换后进行亲水作用液相色谱-串联质谱分析。马来酰肼及马来酰肼-O-β-D-葡萄糖苷的基质添加标准曲线的线性范围为5~150 mg/kg,相关系数（r²）为0.9971及0.9972,检出限分别为0.5 mg/kg和0.3 mg/kg,定量限分别为1.0 mg/kg和0.8 mg/kg。马来酰肼及马来酰肼-O-β-D-葡萄糖苷在10、40、80 mg/kg 3个加标水平下的回收率为83.1%~112.3%,在40 mg/kg加标水平下的日内重复性分别为2.7%和3.8%,日间重复性分别为8.3%和7.1%。应用该方法分析喷洒马来酰肼28天后烟叶中马来酰肼的分布情况,发现马来酰肼含量减少了80.8%,其中仅有7.6%转化成了马来酰肼糖苷,其他马来酰肼的去向有待进一步研究。     

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。     

丹磺酰肼衍生-高效液相色谱-荧光检测法测定包装纸中的甲醛和乙醛

建立了丹磺酰肼(DNSH)衍生-高效液相色谱-荧光检测测定包装纸中甲醛和乙醛的分析方法,并与2,4-二硝基苯肼(DNPH)衍生法进行了比较。纸张样品经衍生化试剂振荡萃取30 min,衍生化反应24 h,萃取液经PSA/C18净化管净化处理后,以Diamonsil~ C18(2)色谱柱(150 mm×4.6 mm,5μm)为固定相,用醋酸水溶液(pH2.55)-乙腈为流动相进行梯度洗脱。采用荧光检测器检测,激发波长为330 nm,发射波长为484 nm。结果表明,衍生剂、甲醛-DNSH和乙醛-DNSH在20 min内可完全分离,方法的加标回收率为81.64%~106.78%,相对标准偏差(RSD)为2.02%~5.53%(n=5),甲醛和乙醛的检出限分别为19.2μg/kg和20.7μg/kg,定量限分别为63.9μg/kg和69.1μg/kg。该法操作简单,灵敏度高,比常规方法具有更低的检出限,能很好地应用到实际样品检测中,为低含量醛类化合物的检测提供了一种新思路。     

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.     

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.     

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.     

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.