分子印迹固相萃取-液相色谱质谱联用对4种磺酰脲类除草剂残留的测定

采用苄嘧磺隆分子印迹固相萃取柱(MISPE)对加标大米中的苄嘧磺隆、甲磺隆、苯磺隆和烟嘧磺隆4种磺酰脲类除草剂进行净化和富集预处理,并采用LC-MS方法进行定量分析.质谱条件为:正离子检测模式(M+H),检测质量范围为m/z 200 ～800 ,毛细管电压3.93 kV,锥孔电压20 V,脱溶剂温度250 ℃,辅助气流速4 L/min.4种磺酰脲类除草剂在0.01 ～0.70 mg·L~(-1)范围内线性良好.回收率为68% ～100%,表明样品液中的烟嘧磺隆、甲磺隆、苯磺隆和苄嘧磺隆能直接被分子印迹固相萃取柱中的印迹位点保留,而杂质几乎不被保留.分子印迹固相萃取柱对磺酰脲类除草剂表现出良好的识别性能.     

Determination of four sulfonylurea herbicides in tea by matrix solid‐phase dispersion cleanup followed by dispersive liquid–liquid microextraction

Matrix solid‐phase dispersion combined with dispersive liquid–liquid microextraction has been developed as a new sample pretreatment method for the determination of four sulfonylurea herbicides (chlorsulfuron, bensulfuron‐methyl, chlorimuron‐ethyl, and pyrazosulfuron) in tea by high‐performance liquid chromatography with diode array detection. The extraction and cleanup by matrix solid‐phase dispersion was carried out by using CN‐silica as dispersant and carbon nanotubes as cleanup sorbent eluted with acidified dichloromethane. The eluent of matrix solid‐phase dispersion was evaporated and redissolved in 0.5 mL methanol, and used as the dispersive solvent of the following dispersive liquid–liquid microextraction procedure for further purification and enrichment of the target analytes before high‐performance liquid chromatography analysis. Under the optimum conditions, the method yielded a linear calibration curve in the concentration range from 5.0 to 10 000 ng/g for target analytes with a correlation coefficients (r²) ranging from 0.9959 to 0.9998. The limits of detection for the analytes were in the range of 1.31–2.81 ng/g. Recoveries of the four sulfonylurea herbicides at two fortification levels were between 72.8 and 110.6% with relative standard deviations lower than 6.95%. The method was successfully applied to the analysis of four sulfonylurea herbicides in several tea samples.     

Pseudilins: Halogenated,Allosteric Inhibitors of the Non‐Mevalonate Pathway Enzyme IspD

The enzymes of the non‐mevalonate pathway for isoprenoid biosynthesis have been identified as attractive targets with novel modes of action for the development of herbicides for crop protection and agents against infectious diseases. This pathway is present in many pathogenic organisms and plants, but absent in mammals. By using high‐throughput screening, we identified highly halogenated marine natural products, the pseudilins, to be inhibitors of the third enzyme, IspD, in the pathway. Their activity against the IspD enzymes from Arabidopsis thaliana and Plasmodium vivax was determined in photometric and NMR‐based assays. Cocrystal structures revealed that pseudilins bind to an allosteric pocket by using both divalent metal ion coordination and halogen bonding. The allosteric mode of action for preventing cosubstrate (CTP) binding at the active site was elucidated. Pseudilins show herbicidal activity in plant assays and antiplasmodial activity in cell‐based assays.     

Synthesis of N-Substituted -Alkoxy-3-aryl-4-methyl-2,5-dihydro-2-pyrrolones

5-Alkoxy-1-aralkyl-3-aryl-4-methyl-2,5-dihydro-2-pyrrolones and the corresponding alkylthio derivatives were synthesized for the first time through the intermediate formation of unsymmetrical maleimides. The possibility of wide variation of the substituents at positions 1, 3, and 5 of the 2-pyrrolones was demonstrated.     

Development of an Ion-Pairing Liquid Chromatography Method for the Determination of Phenoxyacetic Herbicides and Their Main Metabolites: Application to the Analysis of Soil Samples

A modified ion-pairing liquid chromatography method is developed for the analysis of 2,4-dichlorophenoxyacetic acid (2,4-D), 4-chloro-2-methylphenoxyacetic acid (MCPA) and their phenolic metabolites in water and soil samples. The separation and determination of all compounds of interest can be performed with a mobile phase containing 30% acetonitrile and 10 mM tetrabutylammonium hydroxide as the ion-pairing reagent. Separation of the two phenoxyacids is strongly affected by the pH of the mobile phase, which has to be buffered to pH 7.2 with phosphoric acid. The increase in the hydrophobicity of the sample solvent results in wider peaks for the two phenoxyacids, which reduces the resolution in their separation. The evaluation of different methanol:water solvent mixtures shows that no baseline separation for the two phenoxyacids is obtained when the methanol content in the mixture is higher than 60%.     

固相萃取/高效液相色谱法测定地表水中磺酰脲类农药的研究

建立了固相萃取/高效液相色谱法(SPE/HPLC)同时测定地表水中五种磺酰脲类农药的方法。研究了固相萃取提取、净化方法,优化了高效液相色谱条件并用二极管阵列检测器进行定量分析。五种磺酰脲类农药在0.1~10.0μg/mL范围内线性良好,相关系数在0.9992~0.9998之间,相对标准偏差在1.8%~4.1%之间,平均回收率为72.8%~103%。本方法中五种磺酰脲类农药的检出限在0.02~0.22 ng/mL范围。用该法分析了某水域地表水,取得满意结果,表明本方法具有一定的实用性。     

New dispersive solid phase extraction sorbent of graphitic carbon nitride for field evaluation and dissipation kinetics of pesticides in wheat ecosystem by liquid chromatography tandem mass spectrometry

Nanosheets of graphitic carbon nitride (GCN) were used as the dispersive solid-phase extraction (d-SPE) sorbent for the first time. GCN successfully purified complex matrices of soil, wheat, and wheat straw utilising a simple QuEChERS (quick, easy, cheap, effective, rugged, and safe) method with liquid chromatography tandem mass spectrometry. Pesticides recoveries in the range of 80–110%, small matrix effect, and decreased amounts guaranteed and distinguished this new sorbent. The application of a real formulation of pesticides under field conditions during 2015 in the wheat ecosystem illustrated the clean-up effect and application potential of GCN. It is a valuable and potential substitute for C18 according to the results comparison between two sorbents, including recoveries, matrix-matched calibration, and dissipation kinetics of pesticides. The new use of GCN also enriched the knowledge of d-SPE and sample preparation furthermore.     

Bioisosterism between Sulfonyl Group and Phosphoryl Group-The Synthesis of New ALS Inhibitors N-(Arylamino Hydroxyl Phosphoryl)-N'-(4,6-Dimethoxypyrimidine-2-yl)ureas

Sulfonylureaherbicidesisanewclassofherbicidesdiscoveredinthemid-l97O's',whosemodeofactionhasbeenestablishedastheinhibitionofacetolactatesynthase(ALS,alsoreferredasacetohydroxyacidsynthase)'-Muchattentionhasbeenfocussedonthiskindofcompound,sincetheyhaveunprecedenteduserates,ahighdegreeofselectivity,andexcellentenvironmentalsafety'.NumerousmodificationsofthestrUctureofthisclassofherbicideshavebeenreported'.Wehavetakenattentiontothesimi1alltybetweenthesulfonylgroup(-SO2-)andphosphoryIgroup[-P…     

Enzyme Sensor for the Detection of Herbicides Inhibiting Acetolactate Synthase

Abstract

An enzyme sensor for the detection of sulfonylurea herbicides inhibiting acetolactate synthase II (ALS) was developed using an oxygen electrode. ALS, which has an oxygen consumption side reaction, was entrapped in the matrix of PVA-SbQ polymer, and the enzyme membrane was attached to the electrode. The inhibition of side oxygen reaction of ALS II is measured as decreased consumption of O₂ monitored by an oxygen electrode. Preliminary results show that 10^?6 M herbicide concentration can be determined by this method.