Interaction of Metamitron and Fenhexamid with Ca2+-Montmorillonite Clay Surfaces: A Density Functional Theory Molecular Dynamics Study

Metamitron (Meta), an herbicide, and fenhexamid (Fen), a fungicide, are authorized by the European Union to be used in agriculture. This article reports theoretical calculations about Meta and Fen in interaction with a clay surface: a Ca-montmorillonite (Mont). Conformational searches have been performed thanks to Car–Parrinello molecular dynamics simulations from which geometries have been extracted. Interaction and adsorption energies have been calculated for isomers of Meta or Fen in interaction with Mont to understand the relative stability of various kinds of complexation. Substantial adsorption energies are comparable for Meta and Fen: around −40 kcal/mol. For Fen-Mont, the CO monodentate family is surprisingly the lowest in energy. Moreover, the 10 lowest-energy isomers involve complexation on Fen carbonyl oxygens. The Meta-Mont lowest-energy family, N-N, does not involve π delocalization breaking within Meta. At the same time, the stronger the interaction energy is, the larger the structural modifications within Mont are, particularly concerning the interacting cation distance to the surface. The non-negligible charge transfer and the magnitude of the adsorption energy speak in favor of the chemisorption of the pesticide on the surface. © 2019 Wiley Periodicals, Inc.     

Magnetic solid-phase extraction of organophosphorus pesticides from apple juice and environmental water samples using magnetic graphene oxide coated with poly(2-aminoterephthalic acid-co-aniline) nanocomposite as a sorbent

An effective magnetic solid-phase extraction method was proposed using magnetic graphene oxide coated with poly(2-aminoterephthalic acid-co-aniline) as a sorbent for preconcentration and extraction of organophosphorus pesticides from environmental water and apple juice samples, and determined using the gas chromatography-mass spectrometry analysis. To approve the successful synthesis of the magnetic nanocomposite, the prepared sorbent was characterized by field emission scanning electron microscopy, X-ray diffraction, vibrating sample magnetometer, and Fourier transforms infrared techniques. The main parameters affecting the extraction efficiency were considered and studied to afford an optimized procedure. Systematic method validation verified its suitable recoveries (89.4–107.3%), and precision (relative standard deviations < 6.8%). The method showed a wide linear dynamic range (0.04–700 ng/mL) with low limits of detection (0.01–0.06 ng/mL) and quantification (0.04–0.21 ng/mL). This method presented good potential and great sensitivity for the pesticides determination.     

Monitoring pesticide residues in dates marketed in Al‐Qassim,Saudi Arabia using a QuEChERS methodology and liquid chromatography–tandem mass spectrometry

A sensitive, simple and rapid QuEChERS extraction method and liquid chromatography equipped with triple quadrupole mass spectrometry (LC‐MS/MS) were used to determine 42 pesticides in dates. Acidified acetonitrile and citrate buffer salts were used to extract re‐hydrated samples. Acceptable validation performances were achieved, i.e. recovery range of 70−120% and RSD values ≤20% for 42 analytes at three different concentrations:100, 50 and 10 μg/kg. This method was used to analyse 200 date fruit samples (var. Sukkari) collected from different large markets in the Al‐Qassim region in Saudi Arabia. Pesticide residues were detected in 36 (18%) of the date fruits samples, and 15 samples (7.5%) exceeded the maximum residue levels. The ruggedness test results showed that this method is robust and suitable for the determination of pesticide residues in dates. Additionally, the results showed that the monitored dates did not have a health impact on consumers in Saudi Arabia during the study period.     

Liquid Chromatography-Tandem Mass Spectrometry for the Simultaneous Analysis of 353 Pesticides in the Edible Insect Tenebrio molitor Larvae (Mealworms)

Tenebrio molitor larvae (mealworm) is an edible insect and is considered a future food. Using liquid chromatography-tandem mass spectrometry (LC-MS/MS), a novel method for simultaneous analysis of 353 target analytes was developed and validated. Various sample preparation steps including “quick, easy, cheap, effective, rugged, and safe” (QuEChERS) extraction conditions, number of acetonitrile-hexane partitions, and dispersive-solid phase extraction (dSPE) sorbents were compared, and the optimal conditions were determined. In the established method, 5 g of homogenized mealworms was extracted with acetonitrile and treated with QuEChERS EN 15662 salts. The crude extract was subjected to three rounds of acetonitrile-hexane partitioning, and the acetonitrile layer was cleaned with C18 dSPE. The final solution was matrix-matched and injected into LC-MS/MS (2 μL). For target analytes, the limits of quantitation (LOQs) were ≤10 μg/kg, and the correlation coefficient (r²) of calibration was >0.990. In recovery tests, more than 90% of the pesticides showed an excellent recovery range (70–120%) with relative standard deviation (RSD) ≤20%. For more than 94% of pesticides, a negligible matrix effect (within ±20%) was observed. The analytical method was successfully applied and used for the detection of three urea pesticides in 4 of 11 mealworm samples.     

陈皮中农药残留分析及风险评估研究

通过分析中药陈皮的农药残留问题开展风险评估研究。采用气相色谱-串联质谱(GC-MS/MS)和高效液相色谱-串联质谱(HPLC-MS/MS)对198批陈皮中的117种农药进行检测;采用点评估方式计算陈皮中农药残留的急性和慢性摄入风险;采用英国兽药残留委员会提出的兽药残留风险排序矩阵计算各农药的风险得分;采用危害指数(HI)法计算有机磷农药的慢性累积风险。198批陈皮中共检出30种农药(含13种禁用农药),总检出率为98.5%,农药检出量为0.001~11.7 mg/kg。检出农药的慢性膳食摄入风险(%ADI)为0.003%~3.142%,急性膳食摄入风险(%ARfD)为0.022%~26.667%,风险均远低于100%,表明陈皮中农药的膳食暴露风险处于较低水平。6种有机磷农药的慢性累积暴露危害指数为0.942,略小于1,表明风险虽可控但需要关注。风险排序结果表明,陈皮中有16种为中高风险农药,应在生产和安全监管中重点关注。     

基于通过型固相萃取-超高效液相色谱-高分辨质谱同时测定杨梅中29种农药残留

建立了基于PRiME HLB通过型固相萃取净化-超高效液相色谱-高分辨质谱法(UPLC-HRMS)快速准确测定杨梅中29种常见农药残留的检测方法。杨梅样品经乙腈涡旋提取、盐析和PRiME HLB固相萃取净化后,以5 mmol/L乙酸铵水溶液和乙腈溶液作为流动相在Waters ACQUITY UPLC HSS T₃色谱柱(100 mm×2.1 mm, 1.8 μm)上进行色谱分离,采用正离子电喷雾离子化模式(ESI⁺)和一级全扫描-数据依赖二级质谱扫描模式(Full mass-ddMS²),基质匹配外标法定量分析。该研究首先优化了液相色谱条件,重点考察了Waters ACQUITY UPLC HSS T₃色谱柱和Waters ACQUITY UPLC BEH C₁₈色谱柱对29种农药色谱行为的影响,结果表明Waters ACQUITY UPLC HSS T₃色谱柱相比后者具有更强的色谱保留能力;流动相优化结果显示,相比于乙腈-甲酸水溶液体系和乙腈-甲酸-乙酸铵水溶液体系,乙腈-乙酸铵水溶液体系作为流动相时29种农药普遍具有更佳的色谱保留,部分农药的质谱响应有了显著的提高。此外,该研究通过考察3种不同净化方法的基质效应以优化杨梅中29种农药残留检测,实验结果表明,相比于GCB SPE和QuEChERS法两种净化方式,PRiME HLB法对于杨梅提取液具有较好的基质净化能力。在最佳实验条件下,29种农药在1.0~200.0 μg/L范围内呈现良好的线性关系(线性相关系数R²>0.999),方法检出限为2.0 μg/kg;低(6 μg/kg)、中(200 μg/kg)、高(400 μg/kg)3个加标水平下,29种农药的加标回收率为69.2%~135.6%,相对标准偏差为0.7%~14.6%。该方法具有快速、简便、灵敏和准确等优点,适用于理化实验室大批量样品的日常监测。     

气相色谱法测定坚果中8种拟除虫菊酯农药残留

建立了东盟进口坚果夏威夷果、开心果、杏仁中8种拟除虫菊酯农药残留的检测方法。样品采用乙腈作萃取溶剂超声波提取,经中性氧化铝串联弗罗里硅土小柱净化,组分经不同极性的两根毛细管柱进行分离,采用气相色谱法以ECD检测器检测坚果中8种拟除虫菊酯农药。该方法在0.01~1.0μg/m L浓度范围内具有良好的线性关系,相关系数为0.999 2~0.999 9;在农药添加浓度为10,20,50μg/kg时,回收率为71%~115%,相对标准偏差为4.5%~9.8%,检出限(LOD,S/N=3)为0.014~0.28μg/kg,定量下限(LOQ,S/N=10)为0.047~0.94μg/kg。该方法分离效果好,准确可靠,回收率高,方便快速,可用于坚果中农药残留的日常检测。     

热解析低温等离子体电离源用于糯高粱中农药残留的快速筛查

本研究设计并搭建了一套热解析低温等离子体电离源(TD-LTP),与质谱联用实现了糯高粱中农药残留的快速和高灵敏检测.TD-LTP由热解析装置和低温等离子体放电源两部分组成,农药残留样品首先在热解析进样器内汽化,再由载气载带进入等离子体区域被电离.热解析进样器使LTP产生的气相等离子体与样品之间的气-固或气-液相互作用转变为气-气相互作用,大大提高了难挥发样品(如农药)的电离效率;电离源与质谱进样口之间采用同轴连接,提高了离子的利用率和传输效率.与传统的LTP电离源相比,TD-LTP电离源的灵敏度提高了8倍以上,稳定性提高了4倍.本研究对热解析低温等离子体电离源的各参数进行了优化,并与自制的矩形离子阱质谱相结合,研究了12种农药在该电离源下的特征离子.最后,将此电离源与商品化的三重四极杆质谱仪联用,对糯高粱样品中的12种农药残留进行了快速筛查,结果表明,本方法灵敏度高,可以满足食品安全国家标准规定的谷物中农药残留最大限量检测要求.     

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.     

量子点传感器在有机磷农药残留检测中的应用

有机磷农药作为一种神经毒剂,在过量使用后会造成许多潜在危害,如污染作物、环境以及使人畜中毒等。因此,建立高灵敏、高特异的有机磷农药残留检测方法对于保障食品安全与人体健康具有重要意义。基于量子点的传感器分析检测方法因其具有灵敏度高、特异性强、响应速度快、操作简单等优势,在有机磷农药残留检测方面成为研究热点与发展趋势。本文对国内外近年来量子点传感器在作物、环境以及生物样品中有机磷农药残留检测的应用进展进行了综述,并对该领域的前景进行了展望。