Fabrication of Au nanorod‐coated Fe3O4 microspheres as SERS substrate for pesticide analysis by near‐infrared excitation

Au nanorods coated Fe3O4 (Fe₃O₄@NRs) microspheres were designed as functional surface‐enhanced Raman scattering substrate with a feature of magnetic property and used for detection of pesticide residues that are annually used in agriculture by near‐infrared (NIR) excitation. With this strategy, the Fe₃O₄ microspheres were synthesized by hydrothermal method and surface functionalized with polyethylenimine, and then coated with Au nanorods densely. The Raman spectra were carried out by NIR excitation and 4‐ATP was chosen as the probe molecule. The results showed a good SERS activity of the Fe₃O₄@NRs microspheres. Moreover, this substrate could be used for pesticide analysis by portable Raman spectrometer with NIR excitation. Especially, the microspheres could be transferred from pesticides contaminated fruits peel to specially cleaned glass slide with the aid of the external magnetic field, by which the strong fluorescence of the apple components can be avoided while performing the pesticide analysis of fruits peel. Copyright © 2015 John Wiley & Sons, Ltd.     

Dynamic Microwave-assisted Extraction Online Coupled with QuEChERS for the Determination of Organophosphorus Pesticides in Cereals by Gas Chromatography

A rapid analytical method was first developed to detect organophosphorus pesticides(OPPs) in cereals, which used dynamic microwave assisted extraction(DMAE) coupled online with a modified quick, easy, cheap, effective, rugged, and safe(QuEChERS) method. Cereals samples were mixed with a certain amount of quartz, C₁₈ and the primary second amine(PSA), and extracted successively with the acetonitrile-water solution(80%, V/V) under microwave irradiation. The obtained eluate was directly introduced into a collection tube containing NaCl and MgSO₄. Finally, the supernate was evaporated and reconstructed, and determined by gas chromatographic spectrometry. Some factors affecting the experimental results were studied and optimized. The extraction and purification processes were carried out coinstantaneously and 12 samples could be treated in one step in 4 min. Low limits of detection(0.43-1.31 μg/kg) for OPPs were obtained in cereals. The relative standard deviations(RSDs) were 2.1%-9.3%. The recoveries of OPPs ranged from 76.1% to 100.2%. By combining the advantages of DMAE with QuEChERS, the sample pretreatment process was simple to operate, with little amount of organic solvent. The whole extraction process was completed in a closed environment, therefore it was very appropriate for daily analysis of OPPs in cereals.     

茶叶浸出液中农药残留表面拉曼光谱检测与初步定量分析

选取甲基对硫磷和水胺硫磷为研究对象,改良了传统的QuEChERS前处理工艺,以自制纳米金溶胶为增强基底,利用表面增强拉曼光谱(SERS)技术,对茶叶浸出液中的农药残留进行检测。通过比对两种有机磷农药的拉曼特征峰进行定性分析。同时,选取570,1034,1107和1202 cm^-1等拉曼位移附近的特征峰光谱数据,利用微分等数学手段,结合偏最小二乘法(PLSR)建立回归方程,预测样品中农药残留含量。所得预测数值与气相色谱-质谱联用(GC-MS)法检测值对比,验证本方法的可行性与可信度。结果表明:基于SERS技术对上述两种有机磷农药的检出限可达0.05 mg/L;通过数学模型分析建立回归方程,其线性相关系数范围为0.9077~0.9824,预测均方根误差(RMSEP)范围为0.77%~2.68%;利用回归方程得到的预测值与GC-MS检测结果基本接近,相对误差范围-5.16%~9.03%,回收率为81.4%~115.1%,说明可以用SERS技术对茶叶浸出液中的有机磷农药残留进行定性和初步定量分析。     

Mercury meniscus on solid silver amalgam electrode as a sensitive electrochemical sensor for tetrachlorvinphos

The in-house prepared mercury meniscus modified solid silver amalgam electrode (m-AgSAE) was successfully applied for the detection of organophosphate pesticide tetrachlorvinphos in pH 7 buffer solution. The electrochemical performance of m-AgSAE for the reduction of tetrachlorvinphos was evaluated using cyclic voltammetry (CV), differential pulse voltammetry (DPV), and square wave voltammetry (SWV), respectively. The surface morphology of solid silver electrode (AgE), as-amalgamated solid silver amalgam electrode (AgSAE), and polished solid silver amalgam electrode (p-AgSAE) was examined by field emission scanning electron microscopy (FESEM). Among the applied techniques, DPV and SWV analysis showed a remarkable increase in the reduction peak current and provided a simple, fast, and sensitive method for the determination of tetrachlorvinphos. The electrochemical impedance spectroscopy (EIS) was used to correlate the electrocatalytic activity of AgSAE, p-AgSAE and m-AgSAE with their interfacial charge transport capabilities. Under the optimized experimental conditions, the DPV and SWV responses were linear over the 1–9 μM and 10–50 μM concentration ranges with a detection limit of 0.06 μM for DPV and 0.04 for SWV. The estimation of tetrachlorvinphos in the ground and waste water samples with the proposed method was in good agreement with that of the added amount. The proposed electrochemical method not only extends the application of non-toxic m-AgSAE, but also offers new possibilities for fast and sensitive analysis of tetrachlorvinphos and its structural analogs in environmental samples.     

Constraining the Teratogenicity of Pesticide Pollution by a Synthetic Nanoreceptor

The teratogenicity of the pesticide nereistoxin (NTX) and its derivative thiocyclam (THI) towards aquatic life was dramatically constrained by a synthetic nanoreceptor, cucurbit[7]uril, through selective encapsulation of the pesticides (K_CB[7]‐NTX of 3.24(±0.31)×10⁶ m ^?1 and K_CB[7]‐THI of 7.46(±0.10)×10⁵ m ^?1), as evidenced by the rate of hatchability, morphology development, and tyrosinase activity of zebrafish larvae incubated with the pesticides (3–300 μm ) in the absence and in the presence of 300 μm cucurbit[7]uril, demonstrating the significant potential of the nanoreceptor in managing ecological pollution of these pesticides.     

农药荧光寿命测试系统的原理与设计

介绍荧光的产生、荧光寿命的产生机理以及荧光寿命测量的基本原理。设计了一种利用直接记录法(光子计数法)测量农药荧光寿命的测试系统。该系统针对待测样品的特性，选用了相应的脉冲光源、光学元件和半导体探测器等器件，优化了各器件的工作参数，进行了简易而又科学的模块化设计，并对西维因农药的荧光寿命在无激励光干扰情况下进行了实际测试，测得了西维因溶液在500μg／L浓度时的荧光衰减曲线和荧光寿命(0.30～0.40ns)。结果表明，该系统具有结构简易、操作方便的优点，能测量100ps级的荧光寿命，适合于对能发荧光的农药进行荧光寿命的定量测量。     

固相萃取/气相色谱法测定新会陈皮及其制品中8种有机磷农药

建立了固相萃取/气相色谱同时测定新会陈皮及其制品中8种有机磷农药的分析方法,并对影响提取、净化、检测效率的因素进行优化。样品用乙酸乙酯提取,自制改性多壁碳纳米管和N-丙基乙二胺2种填料分层填装的双层固相萃取小柱净化,Shimadzu Rtx-1701毛细管色谱柱分离,火焰光度检测器检测,外标法定量。在优化实验条件下,8种有机磷农药在0.020~1.0μg/m L范围内具有良好的线性关系,相关系数为0.997 0~0.999 2,检出限(S/N=3)为3.6~8.8μg/kg。3个加标水平下的平均回收率为72.5%~106%,相对标准偏差为2.8%~8.7%。该法准确、快速、灵敏﹑操作简单,可满足新会陈皮及其制品中多种有机磷农药残留同时测定的要求。且自制柱的成本低,能够大幅度减低使用成本,值得推广应用。     

直接进样–超高效液相色谱串联质谱法同时测定水源水中9种农药

建立直接进样–超高效液相色谱三重四级杆质谱联用(UPLC–MS–MS)快速测定水源水中9种痕量农药残留的方法。水样无需富集,经超高效液相色谱分离,串联三重四级杆质谱检测,在7.5 min内完成9种目标化合物的分析。9种农药的检出限(S/N≥3)在0.01~1.4μg/L之间,在各自的考察浓度范围内线性关系良好(r≥0.995)。在1.0~80μg/L添加水平内,实际样品的平均加标回收率为66.2%~114.0%,测定结果的相对标准偏差为2.3%~20.4%(n=6)。该法操作简便,重现性好,可用于饮用水源水中农药残留的快速测定。     

Voltammetric determination of herbicide molinate in river water and rice samples using solid silver amalgam electrode fabricated with nanoparticles

The evaluation of the voltammetric behaviour and the determination of herbicide molinate were performed for the first time over the surface of solid amalgam electrode fabricated with silver nanoparticles using cyclic voltammetry and square-wave voltammetry techniques. The experimental and instrumental parameters were evaluated to reach the maximum analytical response for molinate. It was achieved when a medium composed of 0.04 mol L^?1 Britton–Robinson buffer at the pH value of 4.0 was used. Under these conditions, molinate showed one pronounced reduction peak at E_p = ?0.37 V (vs. Ag/AgCl 3 mol L^?1) that was characterised as an irreversible system. An analytical curve was constructed at the concentration range from 9.36 to 243.49 µg L^?1 and a limit of detection of 2.34 µg L^?1 was obtained. The amalgam electrode presented good stability during the measurements with relative standard deviation (RSD) values of 2.9% for the repeatability and 5.4% for the reproducibility. The voltammetric method developed here could be conveniently applied for the determination of molinate in river water and rice spiked samples at levels below those established on the legislations of European Union and Brazil with good accuracy (RSD of less than 5% for all samples). Comparison with HPLC technique was carried out and the results indicated satisfactory concordance. According to the results depicted here, the silver nanoparticles solid amalgam electrode showed itself highly sensitive and an interesting alternative for the routine analysis of molinate in water and food samples. Furthermore, it introduces an environmentally acceptable alternative to the mercury electrodes, most commonly used for determination of reducible pesticides.     

Review of thin-layer chromatography in pesticide analysis: 2014–2016

ABSTRACT

Publications reporting techniques and applications of thin-layer chromatography (planar chromatography) for the separation, detection, qualitative and quantitative determination, and preparative isolation of pesticides and their metabolites are reviewed for the period from November 1, 2014 to November 1, 2016. Analyses are described for a variety of sample types and pesticide classes. In addition to references on residue analysis, studies such as pesticide chromatographic retention, identification and characterization of natural pesticides, metabolism, bioactivity, degradation, soil mobility, and lipophilicity are covered. The unique advantages of thin-layer chromatography in presenting results as a stored image on an open stationary phase are addressed.