基于超疏水高黏附结构的痕量农药分子现场检测SERS基底研究

多种农药,包括孔雀石绿（MG）作为禁用兽药,存在食用致癌的风险。由于MG低廉的价格和极好的药效,在渔业养殖中一直被不法商贩非法使用,使得鱼类生鲜中时有MG残留检出。针对MG分子痕量残留的检测,目前一般是抽取少量养殖水样,再利用高效液相色谱柱、液相色谱-光谱等方法来评估其是否超标。这类传统的检测方法一般需要依赖价格昂贵的大型设备,且检测过程操作繁琐复杂,单次检测耗时长、价格高,因而与农贸市场中商品流通量大、速度快、价格需亲民低廉等特点和要求不相符合。近年来,表面增强拉曼散射（SERS）检测技术以及便携式拉曼光谱仪的出现,有望实现对痕量农药分子的现场快速检测,进而很好地解决这一问题。SERS检测技术利用金属纳米结构的表面等离激元效应感应位于其结构表面附近的分子,得到分子种类和浓度信息。为了降低可检测的浓度极限,一般会在SERS基底上利用咖啡环效应或其他手段将待测分子蒸发富集,以获得足够高的信号强度。针对亲水基底,液滴与基底相接触后,会在基底表面摊开,使其分布面积扩大,导致其咖啡环周长变长,分子分布浓度随之降低。而当采用疏水基底富集时,由于常规的疏水基底表面黏附性小,液滴在其表面处于随处滚动无法抓取的状态,极大增加了操作的难度。以MG分子痕量残留的检测为例,由于农贸市场人员众多、无专业实验平台,磕碰撞击时有发生,在此环境下采用疏水SERS基底对农药分子进行检测显然是不可取的。该研究提出一种基于超疏水高黏附纳米森林结构的SERS基底用于痕量MG分子的快速现场检测。相比于超疏水SERS基底,所提出的超疏水高黏附基底利用其高黏附性可牢固抓取待测液滴,解决了以往超疏水基底在实际现场检测中存在液滴滚动无法操作的问题。此外,与亲水基底相比,超疏水高黏附基底由于接触角大,可将咖啡环面积缩小5.73倍,继而使分子的富集浓度提高5.73倍,最终使检测极限浓度降低了至少两个数量级。研究所提出的超疏水高黏附SERS基底有望在痕量农药分子快速现场检测中得到应用。     

Vibrational Spectrometry Strategies for Quality Control of Procymidone in Pesticide Formulations

Abstract

Two vibrational spectrometry–based methodologies were developed for procymidone determination in wettable powdered pesticide formulations. The Fourier‐transform infrared (FTIR) procedure was based on the selective extraction of procymidone by chloroform and determination by peak area measurement between 1451 and 1441 cm^?1, using a baseline correction established between 1490 and 1410 cm^?1, and a precision of 0.4% and a limit of detection of 0.01% w/w procymidone for a sample mass of 25 mg were obtained. For FT‐Raman determination, the selected conditions were peak area measurement between 1005 and 995 cm^?1 Raman shift, with a baseline correction fixed between 1030 and 947 cm^?1, and a relative standard deviation of 1% and a limit of detection of 0.8% procymidone in the original sample were obtained. The sample frequency for FTIR determination was 30 hr^?1, lower than that for Raman with 40 hr^?1. FT‐Raman reduces to the minimum the reagent consumption and waste generation, also avoiding the sample handling and contact of the operator with the pesticide. It can be concluded that the proposed methods are appropriate for quality control in commercial pesticide formulations.     

基于QuEChERS净化-气相色谱法同时测定蔬菜中6种有机磷类农药残留

建立了QuEChERS（Quick,Easy,Cheap,Effective,Rugged and Safe）法-气相色谱法测定蔬菜中6种有机磷农药残留量的检测方法.样品用1%乙酸乙腈提取,经N-丙基乙二胺（PSA）和无水硫酸镁分散固相萃取净化,气相色谱火焰光度检测器测定.考察了QuEChERS法在两种不同体系（氯化钠盐析和乙酸盐缓冲体系）的提取净化效果.试验结果表明,在乙酸盐缓冲体系中,有机磷农药残留更加稳定,回收率更高.6种有机磷农药残留在0.2~10.0 mg/L之间线性关系良好,相关系数（R²）均大于0.999,检出限在0.003 5~0.015 mg/L之间.低、中、高3个添加水平的回收率在78.5%~106.3%之间,相对标准偏差在1.4%~6.3%之间.方法简单、快捷,准确可靠,适合大批量样品农残检测.     

Spreading of Oil Droplets Containing Surfactants and Pesticides on Water Surface Based on the Marangoni Effect

Oil droplets containing surfactants and pesticides are expected to spread on a water surface, under the Marangoni effect, depending on the surfactant. Pesticides are transported into water through this phenomenon. A high-speed video camera was used to measure the movement of Marangoni ridges. Gas chromatography with an electron capture detector was used to analyze the concentration of the pesticide in water at different times. Oil droplets containing the surfactant and pesticide spread quickly on the water surface by Marangoni flow, forming an oil film and promoting emulsification of the oil–water interface, which enabled even transport of the pesticide into water, where it was then absorbed by weeds. Surfactants can decrease the surface tension of the water subphase after deposition, thereby enhancing the Marangoni effect in pesticide-containing oil droplets. The time and labor required for applying pesticides in rice fields can be greatly reduced by using the Marangoni effect to transport pesticides to the target.     

Optimization of profenofos organophosphorus pesticide degradation by zero-valent bimetallic nanoparticles using response surface methodology

This study synthesized bimetallic Fe/Ni nanoparticles and used them for catalytic degradation of profenofos, an organophosphorus pesticide. This novel bimetallic catalyst (Fe/Ni) was characterized by scanning electron microscopy (SEM), energy-dispersive X-ray analysis spectroscopy (EDAX) and X-ray diffraction (XRD). The bimetallic nano-catalyst was prepared at diameters of 20–50 nm and was shown to effectively degrade profenofos. A three-factor central composite design combined with response surface methodology was used to maximize profenofos removal using the bimetallic system. A quadratic model was built to predict degradation efficiency. ANOVA was used to determine the significance of the variables and interactions between them. Good correlation between the experimental and predicted values was confirmed by the high F-value (16.38), very low P-value (<0.0001), non-significant lack of fit, an appropriate coefficient of determination (R² = 0.936) and adequate precision (14.75). The highest removal rate attained was 94.51%.     

Method validation,residue analysis and dietary risk assessment of trifloxystrobin and trifloxystrobin acid in milk,eggs and pork

Trifloxystrobin (TFS) is a widely used strobilurin fungicide and its residues accumulating in animal-derived food could result in potential harm to consumers. By optimization of extraction solvents and cleanup sorbents, a residue analysis method for TFS and its metabolite trifloxystrobin acid (TFSA) was established in milk, eggs and pork based on QuEChERS sample preparation and LC–MS/MS. The calibration curves exhibited good linearity with determination coefficients (R²) >0.9930 over the range of 0.5–250 ng/ml for both TFS and TFSA. The recoveries of the two analytes were 81–100% with RSD 3–10% and 76–96% with RSD 2–13%, respectively. The limit of quantification (LOQ) was 1 ng/g for both analytes. The milk, egg and pork samples, 30 each, were collected from the 30 main producing regions in China, and residues of TFS and TFSA were analyzed. The concentrations of both analytes were lower than the corresponding LOQs and maximum residue limits. Long-term dietary risk assessment showed that the hazard quotients were 0.001–0.003%, indicating an absence of unacceptable risks in milk, eggs and pork to the health of common consumers in China.     

Application of image analysis technique for the determination of thiophanate methyl by thin-layer chromatography

A simple and convenient thin-layer chromatography (TLC) method combined with image analysis technique was developed to determine thiophanate methyl. The detection of pesticide was based on iodine–azide reaction. Digital images of TLC plate chromatograms were analysed using TLSee software, and quantitative analysis was conducted. The linearity (0.3–3.0 µg per spot), sensitivity, accuracy and precision of the system were investigated.     

Evaluation and improvement of QSAR predictions of skin sensitization for pesticides

In vivo skin sensitization assays have to be provided by applicants to the competent authorities in the European Union for the approval of active substances (AS) in pesticides. This study aimed to test the practicability of in silico predictions for AS by freely available (Q)SAR tools to evaluate their use as a time- and cost-effective alternative to animal testing in the context of the 3R concept. Predictions of skin sensitization for 48 selected sensitizing and non-sensitizing AS by the software programs CAESAR, Toxtree, OECD (Q)SAR Toolbox, CASE Ultra, Leadscope and SciQSAR were collected and compared. Different data evaluation methodologies (score definition, mean, weighted mean, threshold score definition) were applied to optimize the predictions. The calculation methods were internally cross-validated and further validated with an additional validation set of 80 AS. Although the presented calculation methodologies are not suitable as a stand-alone method, this study has shown weaknesses and strengths of some prominent (Q)SAR programs and diverse combinatorial options in the prediction of skin sensitization by pesticidal AS. The present study will help to foster discussions on in silico alternatives to animal testing in the pesticide area.     

凝胶渗透色谱-气相色谱-离子阱质谱法测定桔梗原药和当归提取物中101种农药残留

建立了凝胶渗透色谱（GPC）-气相色谱-离子阱质谱同时检测桔梗原药和当归提取物中101种农药残留的分析方法。方法采用乙腈超声辅助提取桔梗原药和当归提取物,浓缩提取液至近干后用乙酸乙酯-环己烷（1∶1, v/v）复溶,采用凝胶渗透色谱法（选取40 cm长、内径20 mm的凝胶渗透色谱柱）对样品进行净化,弃去前段含脂类、色素等杂质的流出液,收集17~30 min洗脱液并旋转蒸发浓缩至近干,甲苯1 mL定容上机。选用DB-5MS毛细管色谱柱分离待测物,通过离子阱质谱实现对101种农药残留的高效检测。方法通过优化前处理条件和离子阱二级质谱参数,有效降低了复杂中药基质对待测化合物的干扰,最大限度提高了样品中农药的定量准确性和回收率,101种农药3水平添加的平均回收率为58.3%~108.9%,每个添加水平10次独立重复测定的相对标准偏差为0.4%~16.5%,检出限（LOD）范围为0.2~40.0 μg/kg,可满足当前韩国、日本、欧洲规定的最大残留限量（maximum residue limits, MRLs）要求。方法具有操作简单快速、灵敏度高、重复性好等特点,凝胶渗透色谱技术的应用克服了固相萃取小柱净化容量不足的弊端,离子阱技术的应用可以进一步排除共流出基体杂质的干扰,提高定量和定性的准确性,检测效果优于常用的气相色谱-质谱法,是对中药中同时分析多种农药残留检测方法的有益补充。     

Multiresidue method for the analysis of more than 140 pesticide residues in fruits and vegetables by gas chromatography coupled to triple quadrupole mass spectrometry

A new multiresidue method has been developed and validated for the determination of more than 140 pesticide residues in cucumber and orange by gas chromatography coupled to triple quadrupole mass spectrometry (GC-QqQ-MS/MS) in a single run of 25.50 min. The triple quadrupole (QqQ) analyzer simultaneously operated in the selected reaction monitoring (SRM) and selected ion monitoring (SIM) modes, acquiring two or three transitions per compound. Samples were extracted by the application of a single-phase extraction of 10 g of sample with acetonitrile containing 1% of acetic acid, followed by a liquid-liquid partition formed by the addition of 4 g of MgSO(4) and 1 g of NaOAc. A dispersive solid-phase extraction (D-SPE) with primary secondary amine (PSA) was applied to clean up the extracts. A final concentration step was included in order to increase sensitivity in the instrumental analysis. The method was properly validated in each matrix in a wide dynamic range (10-400 microg kg(-1)): this work relies on a new quantification strategy by the use of two calibration curves to increase the dynamic range, which permitted reduction of sample dilutions and increase in sample throughput. Recovery was studied at three concentration levels (11.5, 50.0, and 150.0 microg kg(-1)), yielding values in the range 70-110% with precision values, expressed as relative standard deviation (RSD), lower than 20 and 25% for the intraday and interday precision, respectively. Limits of quantification (LOQs) were established at 10 microg kg(-1), the lowest maximum residue level (MRL) value set by the European Union in vegetables. The method was successfully applied to the analysis of pesticide residues in real samples from the southeastern Spain. Copyright (c) 2008 John Wiley & Sons, Ltd.