Fe3O4@Au纳米星颗粒作为循环SERS基底用于农药残留物的检测

本文首先采用共沉淀的方法制备了Fe3O4纳米颗粒,随后经柠檬酸钠和对苯二酚还原氯金酸的方法在Fe3O4纳米颗粒的表面生成刺状Au纳米结构,进而获得Fe3O4@Au纳米星颗粒。该Fe3O4@Au纳米星颗粒作为SERS基底,用作农药残留物福美双和敌瘟磷的检测。由于高密度的Au纳米结构的尖端效应,该基底显示出高敏感的SERS活性。最后利用Fe3O4纳米颗粒的磁性,将其用于循环SERS测试,研究了其循环使用特性。     

SERS结合快速前处理检测绿茶中毒死蜱农药残留

茶叶是中国的主要经济作物之一,而在茶叶种植过程中存在农药不合理使用及滥用等行为,导致茶叶中存在严重农药残留问题。茶叶中农药残留检测主要采用经典化学实验室方法,存在前处理复杂、耗时长、成本高等缺陷,急需研究茶叶中农药残留的快速检测方法,以监管茶叶市场的质量安全。本论文采用纳米竹炭(NBC)为净化剂快速去除绿茶的色素等基质影响,使用表面增强拉曼光谱(SERS)方法分析绿茶中毒死蜱农药残留,建立绿茶中毒死蜱农药残留的SERS快速检测方法。采用不同NBC用量(0,15,20,25和30 mg)去除茶叶基质,比较不同NBC用量去除基质的净化效果和SERS谱图,得出最优NBC用量,并对前处理方法进行回收率实验,验证前处理方法的可靠性。结果表明,使用20 mg NBC能较好地净化绿茶中的色素等基质影响,前处理方法回收率实验表明,该净化剂用于绿茶中毒死蜱农药残留基质净化是可行的。采用密度泛函理论模拟毒死蜱分子理论拉曼光谱,对比毒死蜱分子理论拉曼光谱和实验拉曼光谱,对其官能团进行谱峰归属,得到定性定量分析绿茶中毒死蜱农药残留的5个特征峰:526,560,674,760和1096 cm-1。在0.28~11.11 mg·kg-1浓度范围内,以1096 cm-1的峰强度建立绿茶中毒死蜱农药残留线性分析方程y=0.0175x+0.9092,决定系数为R 2=0.9863,表明毒死蜱农药浓度与其特征峰强度之间具有良好的线性关系,方法的平均回收率在96.71%~105.24%之间,相对标准偏差(RSD)为2.36%~3.65%。该方法检测绿茶中毒死蜱农药的最低检出浓度约为0.56 mg·kg-1,单个样本检测时间在15 min内完成。研究表明,表面增强拉曼光谱技术结合净化剂前处理方法能快速检测绿茶中的农药残留。     

计算机辅助对农药杀虫剂质谱信息的分类预测

对农药质谱信息的研究有助于辅助完成农药残留的鉴别和农药前体化合物的筛选。根据GB 4839-1998,选出4类杀虫剂,其常见化学结构有有机氯类、有机磷类、氨基甲酸酯类和拟除虫菊酯类农药。从NIST2.0质谱数据库中提取针对这4类结构的质谱数据,经过数学变换以及遗传算法和偏最小二乘回归相结合(GA-PLS)特征选择后,确定最优的质谱特征集,最后使用K最邻近法(KNN),支持向量机(SVM),助推法与分类回归树(AdaBoost-CART)构建预测模型。实验表明,SVM和AdaBoost-CART使用仅含有少量的特征组成的最优特征集,可以得到较好的预测结果。     

固相微萃取/气相色谱-质谱检测纺织品中有机磷农药残留

采用PDMS萃取纤维一次吸附富集纺织品中马拉硫磷、甲基对硫磷、敌敌畏、三唑磷、对硫磷、喹硫磷、二嗪磷7种有机磷农药,在气相色谱-质谱(GC-MS)进样口热解吸后进行定性定量检测。筛选了几种商品化的萃取纤维,并优化了萃取时间、萃取温度、吸附时间、盐浓度以及pH值等萃取条件。本方法操作简单、快速、环保,检出限低,可适用于生态纺织品中物质的快速检测。     

便携式农药残留毒性快速测试仪--水果和蔬菜农药残留动力学速测方法

研制了一种新型的化学动力学测试仪器,适用于水果和蔬菜农药残留毒性的测试。阐述了根据农药的毒理学机制所进行的仪器设计原理,了满足设计要求的关键技术和测试方法,该仪器测定速度快,试剂费用低廉,其灵敏度的敌敌畏≤０．３ｍｇ／Ｌ,甲胺磷≤１．５ｍｇ／Ｌ。     

分散固相萃取净化茶叶中20种农药残留量的GC-μECD测定

建立了改进的分散固相萃取(DSPE)提取净化、GC-ECD检测茶叶中六六六、敌敌涕、硫丹、拟除虫菊酯、乙草胺、氟虫腈、溴虫腈等茶叶国际贸易中较为关注的20种农药残留量的方法.前处理过程:(1)以2 mL乙腈提取0.5g茶叶样品,涡旋振荡2 min,离心5 min(5000 r/min);(2)取1mL上清液与PSA(2...     

Cholinesterases in Biorecognition and Biosensors Construction: A Review

Acetylcholinesterase and butyrylcholinesterase are the only two known cholinesterases. Acetylcholinesterase plays an important part in cholinergic system. It terminates neurotransmission by hydrolysis of transmitter acetylcholine. The role of butyrylcholinesterase is not well understood. It is able to detoxify several compounds such as cocaine, succinylcholine, and so forth. The current review is focused on the application of cholinesterases in biorecognition. Cholinesterases are important markers in the body. Butyrylcholinesterase activity in plasma can serve as a liver function test or specific marker for sensitivity to myorelaxants or liver carcinoma. Both cholinesterases can serve as markers of poisoning by some neurotoxic compounds. Nerve agents (sarin, soman, tabun, VX), some Alzheimer disease drugs (galantamine, huperzine, donepezil, rivastigmine), pesticides (carbofuran, trichlorfon, paraoxon, malaoxon), and natural toxins (aflatoxin, pyridostigmine) can act as inhibitors of butyrylcholinesterase and/or acetylcholinesterase. Devices filled with immobilized cholinesterases can be used for the assay of the aforementioned toxins. In this review, methods for examination of cholinesterases activity in the body and in analytical devices are described. Applications, types of diagnosis, and assays are described as well.     

Residue determination of cyromazine and its metabolite melamine in chard samples by ion-pair liquid chromatography coupled to electrospray tandem mass spectrometry

A method has been developed for the sensitive and selective determination of cyromazine and its metabolite melamine in chard samples. Both compounds are small polar basic molecules, making their determination at residue levels complicated. The method involves an extraction procedure with phosphate buffer and methanol using high-speed blender, the addition of tridecafluoroheptanoic acid (TFHA) as ion-pair reagent and the injection of the five-fold diluted extract on liquid chromatography coupled to electrospray tandem mass spectrometry (LC–ESI–MS/MS). The method has been validated for chard samples, spiked at 0.05 and 0.5 mg kg⁻¹. Quantification was carried out by using matrix-matched standards calibration and recoveries were satisfactory, with mean values for cyromazine of 103% and 93%, and relative standard deviations lower than 7%. In the case of melamine, recoveries were 89% and 86%, with relative standard deviations lower than 13%. A limit of quantification of 0.05 mg kg⁻¹ was obtained for both compounds, with the limit of detection below 0.01 mg kg⁻¹. The method, with very little sample handling and good sensitivity, was applied to the rapid determination of low residue levels of these compounds in chards from field residue trials. All the quality controls included during the analysis were satisfactory with average recoveries of 92% and 78% for cyromazine and melamine, respectively.     

Determination of pesticide residues in olives and olive oil by matrix solid-phase dispersion followed by gas chromatography/mass spectrometry and liquid chromatography/tandem mass spectrometry

A novel analytical approach has been developed and evaluated for the quantitative analysis of a selected group of widely used pesticides (dimethoate, simazine, atrazine, diuron, terbuthylazine, methyl-parathion, methyl-pirimiphos, endosulfan I, endosulfan II, endosulfan sulphate, cypermethrin and deltamethrin), which can be found at trace levels in olive oil and olives. The proposed methodology is based on matrix solid-phase dispersion (MSPD), (with a preliminary liquid-liquid extraction in olive oil samples) using aminopropyl as sorbent material with a clean-up performed in the elution step with Florisil, followed by mass spectrometric identification and quantitation of the selected pesticides using both gas chromatography-mass spectrometry (GC-MS) in selected ion monitoring (SIM) mode and liquid chromatography tandem mass spectrometry (LC-MS-MS) in positive ionization mode. The recoveries obtained (with mean values between 85 and 115% (obtained at different fortification levels) with RSD values below 10% in most cases, confirm the usefulness of the proposed methodology for the analyses of these kind of complex samples with a high fat content. Moreover, the obtained detection limits, which were below 5 microg kg(-1) by LC-MS analyses and ranged from 10 to 60 microg kg(-1) by GC-MS meet the requirements established by the olive oil pesticide regulatory programs. The method was satisfactorily applied to different olives and olive oil samples.     

Determination of N-Methylcarbamate Pesticides in Vegetables by Solid-phase Extraction and Pressurized Capillary Electrochromatography

Introduction Capillary electrochromatography(CEC) is a hybrid technique that couples the good selectivity of high-performance liquid chromatography(HPLC) and the high separation efficiency of capillary electrophoresis(CE).Both charged and uncharged compou…