溶解性有机物对土壤中农药残留与分布影响的光谱学研究

溶解性有机物(DOM)通过吸附、竞争吸附、增溶、加速降解等作用影响着农药在土壤环境中的行为,对土壤生态系统及地下水环境的污染与风险产生重要影响。目前多数研究集中在高浓度DOM对农药残留的短效影响。因此,对天然土壤中DOM及其组分对农药环境行为的研究具有重要的现实意义。该研究通过对具有较长农药使用年限的污染场地调查,利用三维激发-发射荧光光谱矩阵技术,结合荧光区域积分方法对天然土壤DOM进行定量化表征,在此基础上分析低浓度天然DOM对农药残留的长期影响。结果表明：(1)天然DOM组分对大多数有机氯农药在土壤中的环境行为影响较小,但对γ-HCH、p,p’-DDE等少数农药的影响较为显著。(2)不同DOM组分对不同种类的农药影响机制不同。其中,代表DOM组分中的酪氨酸含量的荧光区域积分与γ-HCH,p,p’-DDE之间均呈显著的负相关性(p<0.05),代表DOM中微生物降解副产物组分的荧光区域积分与七氯以及代表DOM中胡敏酸大分子组分含量的荧光区域积分与环氧七氯之间均呈显著正相关性(p<0.05),表明在土壤中长期作用过程中,DOM不同组分对不同种农药的影响不同。(3)土壤有机质的腐殖化程度对土壤中农药残留的影响较小。本研究首次利用三维荧光谱与区域积分技术研究了土壤中溶解性有机物不同组分对农药的环境行为的影响作用,对研究农药在土壤和地下水环境中的迁移转化机制提供了一种新的研究思路。     

溶胶-凝胶固相微萃取涂层及其在农药残留分析中的应用

利用溶胶-凝胶(sol-gel)技术制备固相微萃取(SPME)涂层材料.通过硅醇盐前驱体与涂层聚合物羟基硅油(OH-TSO)的水解共聚的方法,成功地制备了聚二甲基硅氧烷sol-gel 涂层的SPME 萃取头,并以农药的混合标准水溶液为研究对象,用直接-固相微萃取-气相色谱法(GC)对涂层的性能进行考察,制成的萃取头适用于多种农药残留的萃取分离分析.     

SERS技术用于苹果表面有机磷农药残留的检测

传统农药残留检测方法比较繁琐、耗时、破坏样品,快速、无损、实时在线是农残检测的发展方向。本文利用表面增强拉曼光谱技术,以苹果为载体,有机磷农药甲拌磷和倍硫磷为研究对象,初步探讨了苹果表面甲拌磷和倍硫磷农药的快速无损检测方法。结果表明,运用表面增强拉曼光谱技术,可使两种有机磷农药的特征频率较易识别,并选取甲拌磷的728 cm-1和倍硫磷的1 512 cm-1 处的拉曼信号作为定量分析目标峰,采用内标法建立甲拌磷、倍硫磷的线性回归模型,可以作为定量分析甲拌磷、倍硫磷的参考依据。     

橙汁中多菌灵农药残留吸收光谱特征研究

利用分光光度计,通过对多菌灵及橙汁-多菌灵混合体系的紫外-可见吸收光谱进行研究,得到橙汁中不同农药含量下的吸收光谱特征,分析了吸光度与多菌灵农药含量的关系。研究表明:多菌灵药液在285nm处有较强的特征吸收峰。通过向橙汁中逐量添加0.28mg·mL-1多菌灵标准溶液,与纯多菌灵药液吸收光谱比较,发现峰值位置出现了小幅度蓝移(285~280nm),说明橙汁和多菌灵发生了相互作用,通过对280nm波长处的吸光度与多菌灵药液含量进行最小二乘法线性拟合,建立了橙汁中吸光度与多菌灵农药含量之间的预测模型,发现吸光度与多菌灵药剂含量具有很好的线性关系,其线性函数模型为:I=2.41+9.26x,相关系数为0.996,回收率在81%~102%之间。根据该回归模型,可以得到橙汁中多菌灵农药残留量的准确值,从而验证了利用紫外-可见吸收光谱测定橙汁中多菌灵残留量的方法的可行性。研究表明,利用光谱技术直接对果汁中农药残留检测方法是可行的,能够满足快速分析的需要,本研究为农药残留检测提供了新的途径。     

Removal of pesticide residues from fresh vegetables by the coupled free chlorine/ultrasound process

Pesticide residue in vegetables has been considered as a serious food safety problem across the whole world. This study investigates a novel advanced oxidation process (AOP), namely the coupled free chlorine/ultrasound (FC/US) process for the removal of three typical pesticides from lettuce. The removal efficiencies of dimethoate (DMT), trichlorfon (TCF) and carbofuran (CBF) from lettuce reached 86.7%, 79.8% and 71.3%, respectively by the FC/US process. There existed a synergistic effect in the coupled FC/US process for pesticide removal and the synergistic factors reached 22.3%, 19.0% and 36.4% for DMT, TCF and CBF, respectively. Based on the analysis of mass balance of pesticides, the synergistic effect was probably attributed to the efficient oxidation of pesticides both in vegetables and in water by the generated free radicals and FC. The surface area and surface structure of vegetables strongly affected the removal of pesticides by FC/US. The removal efficiency of DMT increased from 80.9% to 88.1% as solution pH increased from 5.0 to 8.0, and then decreased to 84.1% when solution pH further increased to 9.0. When the ultrasonic frequency changed from 20 to 40 kHz, a remarkable improvement in pesticide removal by FC/US was observed. As the FC concentration increased from 0 to 15 mg L^–l, the removal efficiencies of pesticides increased firstly, and then became stagnant when the FC concentration further increased to 25 mg L^–l. The pesticide degradation pathways based on the identified intermediates were proposed. The total chlorophyll content was reduced by less than 5% after the FC/US process, indicating a negligible damage to the quality of vegetables. It suggests that the FC/US process is a promising AOP for pesticides removal from vegetables.     

Pesticides and degradation products in groundwaters from a vineyard region: Optimization of a multiresidue method based on SPE and GC‐MS

A reliable multiresidue method based on solid phase extraction was developed using GC–MS to determine and quantify 34 pesticides, including herbicides, fungicides, insecticides, and some of their degradation products, in groundwater in a vineyard region of La Rioja (northern Spain). Different parameters were optimized and good recoveries (65–108% range) and precisions (12–19% range) were achieved with spiked water samples for a concentration of 0.1 μg/L. The experimental results showed an excellent linearity (r² > 0.99) over the 0.1–1.5 μg/L range. The detection limits of the proposed method were 1–37 ng/L for most of the compounds studied. The methodology has been successfully applied to the analysis of groundwater samples from vineyard areas in La Rioja and the presence of pesticides, especially fungicides and herbicides, at several concentration levels was revealed. Terbuthylazine, its metabolite desethyl‐terbuthylazine, and fluometuron were the pesticides most frequently detected in higher concentrations. Overall and taking into consideration the European Union maximum residue limit of pesticides in groundwater, 16 of the 34 compounds included in this study were detected in concentrations over that limit in at least one of the samples analyzed.     

LC-MS/MS法同时测定4种中草药中155种农药残留

建立了液相色谱-串联质谱(LC-MS/MS)同时测定4种中草药(甘草、银杏叶、菊花和八角茴香)中155种农药残留方法。样品采用乙腈、无水硫酸镁和乙酸钠分散固相萃取(DSPE),再经Cleanert TPH固相萃取(SPE)柱净化,乙腈/甲苯(8:1,V/V)洗脱,液相色谱串联质谱多反应监测模式下测定,外标法定量。实验结果表明,155种农药的检出限(S/N=3)和定量限(S/N=10)范围分别为0.4～34.1μg/kg和1.3～113.7μg/kg;在1.0～2400.0μg/kg浓度范围内,155种农药中有148种农药在4种中草药中线性相关系数平均值R2≥0.9950;在低、中、高3个添加水平,86.5%～97.4%的农药平均回收率在60%～120%范围,94.2%～100.0%的农药相对标准偏差RSD≤20%(n=5)。该方法适用于中草药中农药多残留检测。     

农药丁吡吗啉与腐殖酸作用机理探讨

探讨农药丁吡吗啉与腐殖酸的作用机理, 可进一步了解农药在土壤中腐殖酸催化下降解的行为过程。将市售腐殖酸进行逐级分离,获得黄腐酸、棕腐酸和黑腐酸的固态或溶液状态,而后分别与农药丁吡吗啉进行作用,利用红外,荧光两种分析方法对其作用机理进行了解释。结果表明,三组分与丁吡吗啉之间广泛存在范德华力、次级键等弱作用力。黄腐酸与丁吡吗啉之间存在氢键和电荷转移吸附等作用力,棕腐酸与丁吡吗啉存在电荷转移吸附等作用力,黑腐酸与丁吡吗啉之间的作用力最弱,即依照黄腐酸、棕腐酸、黑腐酸三组分平均分子量依次递增的顺序,与农药丁吡吗啉之间的作用力依次降低。     

异丙甲草胺农药残留吸收光谱检测方法研究

除草剂可以快速、有效地进行除草，已被广泛应用，但是在除草剂使用同时也会对周围环境和农作物带来一定程度的污染，例如农业生产过程中经常发现由于除草剂使用不当而使果树中毒的现象。异丙甲草胺是一种酰胺类选择性除草剂，被广泛应用于旱地作物、蔬菜和果园、苗圃。根据相关文献报道，基于气相色谱法、气相色谱-质谱联用法和固相萃取等方法可以实现异丙甲草胺残留检测，而基于吸收光谱法对异丙甲草胺的分析未见相关文献报道，提出直接利用吸收光谱及其导数光谱分析法实现异丙甲草胺农药及其在苹果汁中的农药残留检测。首先利用分光光度计对不同浓度异丙甲草胺药液进行吸收光谱实验研究，发现在266 nm处有明显吸收光谱特征峰。对农药吸收光谱进行拟合分析，得到异丙甲草胺药液浓度和吸光度之间预测模型函数方程，函数方程为y=2.147 09x+0.031 98，相关系数为0.998 5。然后利用分光光度计对苹果汁-异丙甲草胺混合溶液进行吸收光谱实验研究，相对于纯苹果汁吸收光谱，在混合溶液吸收光谱中发现266 nm处为异丙甲草胺所对应的特征峰。对苹果汁中药物浓度和吸光度进行建模，模型函数为：y=0.704 9+0.826 8x，其相关系数为0.991 1。可以看出，当苹果汁中异丙甲草胺残留量很低时，其农药吸收光谱特征峰并不明显。为进一步提高检测效果，对混合溶液吸收光谱进行一阶导数处理，得到其一阶导数吸收光谱。与苹果汁吸收导数光谱相比较，苹果汁-农药混合溶液导数光谱有两个明显特征光谱峰，分别位于269和276 nm处。进一步分析苹果汁-异丙甲草胺混合溶液的导数吸收光谱峰值与农药含量之间的关系，对异丙甲草胺含量与导数光谱吸光度进行函数拟合。其中269 nm对应预测模型函数关系式：y=0.005 3-0.090 6x，相关系数r=0.992 5；276 nm对应预测模型函数关系式为y=-0.000 769-0.302 8x，相关系数r=0.990 6。为验证由吸收光谱和其一阶导数光谱所得苹果汁中农药残留预测模型的准确性，另外配置五种浓度苹果汁-异丙甲草胺混合溶液。然后在同等条件下对其进行吸收光谱实验，将266，269和276 nm处的吸光度分别代入对应模型函数可求得浓度预测值，结合已知浓度值可计算其平均回收率，其中吸收光谱266 nm对应平均回收率为104.68%，导数光谱269 nm对应平均回收率为104.59%，276 nm对应平均回收率为105.18%。对苹果汁中异丙甲草胺检测模型进行分析，计算得到检出限(LOD)和定量限(LOQ)参数值，其中原始吸收光谱对应LOD和LOQ分别为0.014 8和0.049 2 mg·mL-1，一阶导数光谱对应LOD和LOQ最小值分别为0.001 5和0.004 9 mg·mL-1。研究结果表明，采用吸收光谱方法对苹果汁中异丙甲草胺进行直接检测与分析是快速和可行有效的，而且对吸收光谱进行导数运算处理后，检测效果更优。     

Immobilization of acetylcholinesterase on functionalized SBA-15 mesoporous molecular sieve for detection of organophosphorus and carbamate pesticide

A novel method for the immobilization of acetylcholinesterase (AChE) on amino modified SBA-15 mesoporous molecular sieves was developed via electrostatic adsorption and glutaraldehyde crosslinking. The immobilized AChE could be exploited as a fast, sensitive and low-cost biocatalyst towards the detection of pesticides residues which could be stored at room temperature for a long time.