动态液相微萃取-气相色谱法测定水样中有机磷农药残留

建立了水样中敌敌畏、二嗪农、毒死蜱、甲基对硫磷和对硫磷等5种有机磷农药的动态液相微萃取-气相色谱检测方法。实验表明甲苯是良好的萃取溶剂，甲苯体积为2μL时达到最佳萃取效果。液相微萃取是一种非平衡萃取过程，随着萃取次数的增加，萃取效率不断提高，本研究选择萃取次数为25次。在优化的实验条件下，各目标物的萃取富集倍数为21-60；回收率0．85％-2．38％之间；方法的检出限为0．1-0．3μg／L；基体加标检测的相对标准偏差(RSD)为4．9％-8．0％。本方法可用于水体中痕量有机磷农药的富集检测。     

食品基质有机磷农药残留的前处理新方法研究进展

有机磷农药残留是食品安全的重要问题之一,对食品中的有机磷农药进行检测十分迫切必要。然而,食品是一种成分复杂的基质,检测之前必须通过前处理步骤提取和纯化。该文总结了有机磷农药仪器分析的前处理方法,包括固相萃取、液-液微萃取、超声萃取、微波辅助萃取、免疫亲和层析、纳米材料富集等方法,并介绍了这些方法的原理、优缺点以及应用,以期为相关研究提供参考。     

超声辅助固相萃取/离子阱气相色谱-质谱联用测定蔬菜中有机磷农药残留

通过超声辅助固相萃取提取并富集蔬菜中残留的乐果和氧化乐果等9种有机磷农药,采用离子阱二级质谱定性并定量检测其含量,建立了气相色谱-质谱联用测定蔬菜中有机磷农药残留的分析方法.结果表明,所建立的方法简单,快速,灵敏度高.9种有机磷农药的检出限为0.02～0.04 μg/mL,添加回收率为75.07％～99.47％.     

高分子多孔微球富集－HPLC法测定水体中的有机磷

本文提出应用国产高分子多孔微球－ＧＤＸ系列富集－反相高效液相色谱法测定废水中久效磷、乐果、甲基对硫磷三种有机磷农药分析方法。三种不同型号色谱固定相（ＧＤＸ－１０２，ＧＤＸ－３０１和ＧＤＸ－５０１）对水体中ｎｇ／ｍＬ级久效磷、乐果和甲基对硫磷的富集效率分别达到８５％、８２％和９３％以上。采用μ－ＢｏｎｄａｐａｋＣ１８作固定相，以６０％甲醇水溶液作流动相，对三种有机磷农药的分离度可达到１．２以上。本法用于分析水体中有机磷农药，结果令人满意。     

分散液相微萃取-气相色谱联用分析水样中菊酯类农药残留

将分散液-液微萃取(DLLME)与气相色谱-电子俘获检测(GC-ECD)技术相结合,建立了高灵敏度测定水样中7种菊酯类农药残留的新方法。对影响萃取富集效率的因素进行优化,萃取条件选定为:在5.0mL样品溶液中加入10.0μL氯苯和1.0mL丙酮,分散混匀后,以5000r/min离心5min,吸出萃取溶剂氯苯直接进样分析。在优化条件下7种菊酯类农药的富集倍数高达708～1087倍。以α-六六六为内标,7种菊酯类农药在0.8～600μg/L范围内具有良好的线性关系,线性相关系数在0.9990～0.9999之间;检出限为0.04～0.10μg/L(S/N=3)。本方法已应用于自来水、井水及河水等实际水样的分析,平均加标回收率在76.0%～116.0%之间;相对标准偏差在3.1%～7.2%之间。方法具有操作简单、富集效率高和灵敏度高等特点,可满足水样中菊酯类农药残留的检测要求。     

聚合离子液体固载石墨烯复合物的制备及固相萃取有机磷农药的研究

利用1-乙烯基-3-己基咪唑溴盐与氧化石墨烯之间的静电吸引力,将其附着于氧化石墨烯表面,然后经聚合、还原,制备了聚合离子液体-石墨烯复合材料,用SEM、FT-IR、UV-vis等对复合材料进行了表征.将聚合离子液体-石墨烯复合材料用于固相萃取(Solid-phase extraction,SPE)的吸附剂,结合高效液相色谱,研究了此吸附剂对环境水样中4种有机磷农药的萃取性能.对影响SPE效率的参数(吸附剂量、上样体积、上样流速、洗脱剂和洗脱剂体积)进行了优化.在优化条件下,杀螟松、对硫磷、倍硫磷和辛硫磷在5～200 μg/L有良好的线性关系,相关系数(R2)为0.9908～0.9995.将本方法用于环境水样中有机磷农药的测定,加标回收率在80.0％～ 110.0％之间,RSD＜4.5％ (n=3).结果表明,与石墨烯相比,聚合离子液体-石墨烯复合材料作为SPE吸附剂,能降低萃取过程中的团聚现象,对目标物的萃取效能更高;本方法可用于环境水样中有机磷农药残留的测定.     

高分子多孔微球富集—HPLC法测定水体中的有机磷

本文提出应用国产高分子多孔微球－ＧＤＸ系列富集－反相高效液相色谱法测定废水中久效磷、乐果、甲基对硫磷三种有机磷农药分析方法。三种不同型号色谱固定相（ＧＤＸ－１０２，ＧＤＸ－３０１和ＧＤＸ－５０１）对水体中ｎｇ／ｍＬ级久效磷、乐果和甲基以硫磷的富集效率分别达到８５％、８２％和９３％以上，采用μ－Ｂｏｎｄａｐａｋ Ｃ１８作固定相，以６０％甲醇水溶液作流动相，对三种有机磷农药的分离度可达到１．２以上。本     

固相萃取-超高效液相色谱-串联质谱法测定水中16种有机磷农药残留

本研究建立了固相萃取-超高效液相色谱-串联质谱(SPE-UPLC-MS/MS)测定水中16种有机磷农药残留的分析方法.考察了C18柱和HLB柱分别串联活性炭AC固相萃取柱的萃取效果,以及单一和混合溶剂的洗脱效果.水样用0.45 μm滤膜过滤后用HC1调节pH至4,经HLB-活性炭AC串联小柱富集净化后,分别用丙酮-二氯...     

磁性固相萃取吸附剂用于富集环境和食品中残留农药的研究进展

残留农药在体内积累会影响人的健康。种类多样的残留农药广泛存在于环境和食品中,建立高效的样品前处理技术对痕量残留农药进行富集尤为重要。磁性固相萃取技术因其简单、易操作和吸附剂回收方便等优点,被广泛用于富集残留农药。本文介绍了近年来多种材料参与构建的磁性固相吸附剂在残留农药检测中的应用,并对磁性固相吸附剂的发展趋势进行了展望。     

果汁中有机磷农药残留的动态液相微萃取/气相色谱法检测

应用动态液相微萃取与气相色谱联用技术建立了果汁中3种有机磷农药(敌敌畏、甲基对硫磷、对硫磷)的快速分析方法.考察了萃取溶剂、溶剂体积、萃取次数、水样pH值以及离子强度对液相微萃取的影响.3种有机磷农药的线性范围均为40 ～400 μg·L-1,富集倍数22.3 ～51.5,回收率80% ～120%,相对标准偏差2.0% ～8.1%,检出限12.2 ～20.6 μg·L-1.     

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.     

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.     

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.     

Microwave-assisted copper-catalyzed stereoselective ring expansion of three-membered heterocycles with α-diazo-β-dicarbonyl compounds

Microwave-assisted copper-catalyzed ring expansions of three-membered heterocycles with α-diazo-β-dicarbonyl compounds were investigated. Thiiranes generated 3-acyl-5,6-dihydro-1,4-oxathiines in the presence of copper sulfate and trans-3-acyl-5,6-dihydro-1,4-oxathiines as stereospecific products for 1,2-disubstituted cis-thiiranes through an intramolecular S_N2 process. Oxiranes gave rise to 2-acyl-5,6-dihydro-1,4-dioxines under the catalysis of copper hexafluoroacetylacetonate and cis-3-acyl-5,6-dihydro-1,4-dioxines as stereospecific products for 1,2-disubstituted cis-oxiranes via an intimate ion-pair mechanism. The current method provides a direct and simple strategy in efficient preparation of 3-acyl-5,6-dihydro-1,4-oxathiines and 2-acyl-5,6-dihydro-1,4-dioxines, important agents in medicinal and agricultural chemistry, from readily available thiiranes and oxiranes, respectively.     

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.     

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.