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。     

Rapid determination of residual pesticides in tobacco by the quick,easy, cheap,effective, rugged,and safe sample pretreatment method coupled with LC–MS

A quick, easy, cheap, effective, rugged, and safe (QuEChERS) sample pretreatment method coupled with LC–MS was developed for the determination of 11 pesticides in tobacco. Sample pretreatment parameters and instrumental parameters of LC–MS were investigated, and the optimal conditions were selected. Under the optimized conditions, the 11 pesticides were detected simultaneously with a good linear relationship (r² = 0.9993–0.9999) and high precisions (less than 5% of the RSD of peak areas). The LODs were in the range of 0.1–5.0 μg/L. Compared with SPE clean‐up, QuEChERS greatly simplified the sample pretreatment with simple solvent extraction system. After QuEChERS pretreatment, no serious matrix effects were observed. Used for the analysis of real samples, metalaxyl was found in cigarette and tobacco samples at 63.47 and 132.27 ng/g, respectively. The recoveries for 11 pesticides were in the range of 70.03–118.69%, and RSDs were less than 10%. The proposed method is simple, low cost, and has good reproducibility.     

Use of chiral derivatization for the determination of dichlorprop in tea samples by ultra performance LC with fluorescence detection

Dichlorprop is available for agricultural use as a chiral pesticide. In this study, the stereoselective determination of dichlorprop enantiomers in tea samples such as green, black, jasmine, and oolong was developed by ultra performance LC with fluorescence spectrometry after covalent chiral derivatization. The separation was achieved on an Acquity BEH C18 column with the mobile phase consisting of 0.1% formic acid in acetonitrile/water at a flow rate of 0.4 mL/min. In the covalent chiral derivatization using (S)‐(+)‐4‐(N,N‐dimethylaminosulfonyl)‐7‐(3‐aminopyrrolidin‐1‐yl)‐2,1,3‐benzoxadiazole, the peak resolution between the S and R‐dichlorprop enantiomers was 2.6. LODs and LOQs values were 10 and 50 ng/mL standard solution. The linearity of the calibration curves yielded the coefficients (r² > 0.99, ranging from 0.05 to 5 μg/mL) of determination of each of the dichlorprop enantiomers. SPE extraction was used for the sample preparation of dichlorprop in various tea samples. Recoveries were in the range of 82.4–97.6% with associated precision values (within‐day: 82.4–95.8%, n = 6, and between‐day: 83.7–97.6% for 3 days) for repeatability and reproducibility. Based on this result, our method has been proven to be highly efficient and suitable for the routine assay of dichlorprop enantiomers in various tea samples. We propose that the ultra performance LC assay after covalent chiral derivatization would be the renewed tools in the era of chiral stationary platform for chiral pesticide residues in foods.     

农药残留检测中表面增强拉曼光谱的研究进展

农药直接污染环境和食物,最终被人体吸收。其残留物具有高毒性,对人体健康造成严重影响。色谱法、气液色谱串联质谱法等在农药残留检测中应用较为广泛,但存在预处理步骤复杂、费时耗力等缺点。表面增强拉曼光谱（SERS）技术因具备灵敏度高、特异性好、提供全面指纹信息且对样品无损等优点被视为一种新型农残检测方法,可通过简单提取实现液体或固体样品中痕量农药残留的高效检测。在这篇综述中,主要从SERS的增强基底制备、检测方法以及光谱智能解析三个方面对农药残留SERS检测技术及方法的研究进展进行综述,以期为农药残留检测方法提供新的参考。首先,针对SERS增强基底制备,单一的贵金属溶胶纳米颗粒因其“热点”随机、不可控等因素导致稳定性和灵敏性较差,已不能满足痕量农药残留检测。为提高SERS基底的吸附能力使待测物在其表面富集且信号不发生显著变化,对单一贵金属溶胶纳米颗粒进行组装,或加入化学物质、惰性材料等进行修饰制备均一性高的SERS复合基底,保证SERS信号有良好的重现性和灵敏性。其次,为了实现特异性和高灵敏检测,SERS检测方法不再只以单纯的金、银纳米颗粒作为增强基底,而是逐渐趋向于优化样本前处理技术、化学修饰法制备特异性SERS探针、基底物理结构突破以及动态SERS（D-SERS）检测等方向发展。在获得物质的拉曼光谱后,有效拉曼特征区通常在较短的波数范围内,而光谱数据高达上千维,冗余较多,导致后续分析复杂度增加。SERS光谱智能分析则采用化学计量学方法对原始光谱进行预处理、特征提取和模型构建,实现数据降维和主要信息提取,进而实现农残的定性与定量。综上,SERS作为一种快速检测农药残留的方法具有很好的发展前景,可为今后的分析检测领域提供新的借鉴。     

气相色谱-串联质谱法测定烟草中97种农药残留量

利用气相色谱-串联质谱法(GC-MS/MS)检测烟草中97种农药残留。样品以乙腈为溶剂经加速溶剂萃取(ASE),提取液用Carbon-NH2固相萃取小柱净化后,采用VF-5MS色谱柱分离,用电子轰击离子源-多反应监测模式(EI-MRM)检测。97种农药的质量浓度在20~1 000μg·L-1范围内与其峰面积呈线性关系,方法的测定下限(10S/N)在0.02~22.4μg·kg-1之间;在50,100,500μg·kg-1的加标水平下,测得回收率在67.4%~116%之间,测定值的相对标准偏差(n=6)在1.9%~14%之间。     

Synthesis and surface engineering of magnetic nanoparticles for environmental cleanup and pesticide residue analysis: A review

In recent years, water pollution and pesticide accumulation in the food chain have become a serious environmental and health hazard problem. Direct determination of these contaminants is a difficult task due to their low concentration level and the matrix interferences. Therefore, an efficient separation and preconcentration procedure is often required prior to the analysis. With the advancement in nanotechnology, various types of magnetic core–shell nanoparticles have successfully been synthesized and received considerable attention as sorbents for decontamination of diverse matrices. Magnetic core–shell nanoparticles with surface modifications have the advantages of large surface‐area‐to‐volume ratio, high number of surface active sites, no secondary pollutant, and high magnetic properties. Due to their physicochemical properties, surface‐modified magnetic core–shell nanoparticles exhibit high adsorption efficiency, high rate of removal of contaminants, and easy as well as rapid separation of adsorbent from solution via external magnetic field. Such facile separation is essential to improve the operation efficiency. In addition, reuse of nanoparticles would substantially reduce the treatment cost. In this review article, we have attempted to summarize recent studies that address the preconcentration methods of pesticide residue analysis and removal of toxic contaminants from aquatic systems using magnetic core–shell nanoparticles as adsorbents.     

Assessment of uncertainty in pesticide multiresidue analytical methods: main sources and estimation

The estimation of the uncertainty associated to analytical methods is necessary in order to establish the comparability of results. Multiresidue analytical methods lack very often of information about uncertainty of results with likely implications when results are compared with maximum residue levels (MRL) established by regulations. An adequate identification and estimation of each uncertainty source allows to laboratories to establish the accuracy of results and to balance with time-consuming and costs.     

Development of a portable biosensor for screening neurotoxic agents in water samples

A high sensitive portable biosensor system capable of determining the presence of neurotoxic agents in water has been developed. The system consists of (i) a screen-printed electrode with acetylcholinesterase (AChE) immobilized on it, (ii) a self-developed portable potentiostat with an analog to digital (A/D) converter and a serial interface for transferring data to a portable PC and (iii) an own designed software, developed with Lab-Windows CVI, used to record and process the measurements. The system has been developed to perform high precision amperometrical measurements with low drifts, low noise and a good reproducibility. In the configuration depicted, the percentage of AChE inhibition is proportional to the content of neurotoxic agents in a sample. This type of measurement is performed by the steady-state method from the first steady current (by a phosphate buffer solution) and the second steady current (by an enzymatic reaction produced by the addition of acetylthiocholine chloride to the solution). Validation was performed by analyzing spiked water samples containing pesticides. The design is specially suited for screening purposes, does not need sample preconcentration, is totally autonomous and suitable for the field detection of neurotoxic agents in water.     

Multifunctional sorbents for the extraction of pesticide multiresidues from natural waters

In this work multifunctional sorbents, based on surfactant-coated mineral oxides, are assessed for the simultaneous extraction/preconcentration of pesticide multiresidues from aqueous environmental samples. Seventeen pesticides, representative of all the common groups (triazines, phenylureas, carbamates, azols, anilides, chloroacetanilides, organophosphorous, phenoxyacids, aryloxy acids and phenols), are selected for this study. The sorbents assessed are pure sodium dodecyl sulphate (SDS) and mixed tetrabutylammonium (TBA)-SDS hemimicelles and/or admicelles adsorbed onto alumina. Because of their multifunctional character, these sorbents provide different retention mechanisms (i.e. hydrophobic, ionic and/or π-cation interactions), which highly contribute to the efficient retention of pesticides with different polarities and acidities (bases, neutrals and acids). In addition, the low volume of eluent required for complete elution of analytes (typically 1-2 mL) avoided the need of using time-consuming and tedious evaporation steps that generally are needed when cross-linked polymeric resins or carbon materials are used as sorbents. The performance of two sorbents, i.e. SDS and TBA-SDS mixed hemimicelles/admicelles, for the admicellar solid-phase extraction (ASPE) of pesticide multiresidue was comparatively investigated. The latter was selected on the basis of the higher breakthrough volumes permitted, the lower volume of eluent required and the higher sample and eluent flow rates allowed. The proposed ASPE/LC/UV approach provided detection limits lower than 100 ng L⁻¹ for the determination of the 17 pesticides tested. Recoveries from spiked (at the ng L⁻¹ level) river and underground water samples was quantitative for most of the pesticides tested.