Pendimethalin determination in natural water, baby food and river sediment samples using electroanalytical methods

This work describes the electroanalytical determination of pendimethalin herbicide levels in natural waters, river sediment and baby food samples, based on the electro-reduction of herbicide on the hanging mercury drop electrode using square wave voltammetry (SWV). A number of experimental and voltammetric conditions were evaluated and the best responses were achieved in Britton-Robinson buffer solutions at pH 8.0, using a frequency of 500 s^− 1, a scan increment of 10 mV and a square wave amplitude of 50 mV. Under these conditions, the pendimethalin is reduced in an irreversible process, with two reduction peaks at − 0.60 V and − 0.71 V, using a Ag/AgCl reference system. Analytical curves were constructed and the detection limit values were calculated to be 7.79 μg L^− 1 and 4.88 μg L^− 1, for peak 1 and peak 2, respectively. The precision and accuracy were determinate as a function of experimental repeatability and reproducibility, which showed standard relative deviation values that were lower than 2% for both voltammetric peaks. The applicability of the proposed methodology was evaluated in natural water, river sediments and baby food samples. The calculated recovery efficiencies demonstrate that the proposed methodology is suitable for determining any contamination by pendimethalin in these samples. Additionally, adsorption isotherms were used to evaluate information about the behavior of pendimethalin in river sediment samples.     

微分脉冲溶出伏安法测定除草通

提出了苹果、土豆、西红柿中除草通残留量的电分析化学测定方法,研究了除草通在汞电极上的电化学行为,探讨了其电极反应机理。结果表明,除草通在汞电极上具有吸附性质,其电极反应为不可逆的还原过程。本方法的测量线性范围为0．01～0．16mg/L,检出限为9．1μg/L.     

γ-环糊精对二甲戊灵的包合作用

以γ-环糊精(γ-CD)为主体, 采用饱和水溶液法对客体二甲戊灵进行包合. 采用紫外光谱以等摩尔连续变化法确定包合物的包合比为1∶1; 红外光谱证明二甲戊灵的部分苯环结构可能进入了γ-CD的空腔; 热分析结果证明包合作用提升了二甲戊灵的熔点; 粉末X射线衍射谱图中新衍射峰的出现说明形成了新物相; 扫描电镜则直观展现了包合物的外观. 以上结果均表明形成了γ-CD-二甲戊灵包合物, 其包合平衡常数K=1123.99 L/mol. 包合作用使二甲戊灵的熔点从54 ℃升至75 ℃, 溶解度提高了约11.5倍, 包合物热贮稳定性达标, 为进一步将其加工成其它水基化农药剂型提供了可能.     

HPLC法测定除草剂二甲戊乐灵中亚硝胺

介绍用高效液相色谱外标法测定除草剂二甲戊乐灵中 N- ( 1 -乙基丙基 ) - N-亚硝基 - 3,4-二甲基 - 2 ,6-二硝基苯胺含量的方法。用 C8反相柱 ,水∶乙腈 =35∶ 65为流动相 ,在 2～ 30 μg·ml-1内线性良好 ,其线性回归方程为 Ai× 1 0 -6=1 .2 354× 1 0 4 Wi+ 0 .0 2 0 9,相关系数为 0 .9988,RSD为 0 .0 2 % ,加标回收率为 99.81 %～ 1 0 0 .2 9% ,最低检出量为 65ng     

基质固相分散-反相液相色谱法测定蔬菜中二甲戊乐灵农药残留

应用基质固相分散-反相液相色谱技术建立了提取、检测蔬菜中二甲戊乐灵农药残留的分析方法。研究了提取及测定条件对检测二甲戊乐灵的影响,确定了最佳提取条件:萃取吸附剂为弗罗里硅土,样品与弗罗里硅土吸附剂的比例为1∶4,洗脱剂为20 mL乙酸乙酯。二甲戊乐灵的测定线性范围为0.02~2.0 mg/L、r0.999。应用此方法测定了某些蔬菜样品中二甲戊乐灵农药残留,测定相对标准偏差为2.2%~5.2%。在几种蔬菜中的加标回收率为85%~93%,当样品为0.5 g时,方法检出限在5.5~10 ng范围内。     

γ-环糊精对二甲戊灵的包合作用

以γ-环糊精(γ-CD)为主体,采用饱和水溶液法对客体二甲戊灵进行包合.采用紫外光谱以等摩尔连续变化法确定包合物的包合比为1∶1;红外光谱证明二甲戊灵的部分苯环结构可能进入了γ-CD的空腔;热分析结果证明包合作用提升了二甲戊灵的熔点;粉末X射线衍射谱图中新衍射峰的出现说明形成了新物相;扫描电镜则直观展现了包合物的外观.以上结果均表明形成了γ-CD-二甲戊灵包合物,其包合平衡常数K=1123.99 L/mol.包合作用使二甲戊灵的熔点从54℃升至75℃,溶解度提高了约11.5倍,包合物热贮稳定性达标,为进一步将其加工成其它水基化农药剂型提供了可能.     

Loss of Pendimethalin in Surface Runoff from Plots Untilled and Tilled with Tobacco

Abstract

The loss of pendimethalin (N-(ethylpropyl)-2,6-dinitro-3,4-xylidine), a selective herbicide in runoff water was determined on sandy-clay-loam soil plots cultivated with tobacco in relation with the use of ammonium nitrate limestone as fertelizer, for a period of two years, 1990 and 1991. The surface slope of plots was 11% and the use of fertilizer decreased the soil erosion from a value 617 g/m²to 320 g/m². The runoff of surface waters were between 16-24% of the rainfall amounts. Reduction in pendimethalin in waterways results from water loss by infiltration, sediment loss, and by attachment adsorption on vegetative and organic matter. Surface runoff levels were highest for the first runoff event after herbicide application, 1.5 g/10 m² and initial concentrations were related to the time lapse between herbicide application and the date of the first run-off event. Maximum concentrations were 5.95 and 8.54 μg/L in 1990 and 1991 respectively. Persistence studies showed that pendimethalin concentration in runoff of 0.5 cm soil layer decreased by 88.2%, from 2.46 to 0.29 μg/g within 233 days, in 1990 and by 87.6%, from 2.42 to 0.30 μg/g within 235 days in 1991. After 310 day the concentration of pendimethalin was only 0.1 μg/g.     

Determination of the pesticides considered as endocrine-disrupting compounds (EDCs) by solid-phase extraction followed by gas chromatography with electron capture and mass spectrometric detection

An SPE method followed by GC-electron capture detection (ECD) with confirmation by MS for the trace determination of four pesticides considered as endocrine-disrupting compounds (EDCs) in natural waters and sediments has been developed. Target analytes, fenarimol, fenvalerate, pendimethalin, and vinclozolin, belong to different chemical groups and are used mainly in agriculture. In the present study, analysis employs an offline SPE step for the extraction of the target analytes from natural waters. Sonication and subsequent SPE clean-up was used for extraction and purification of the sediment samples which were finally treated with activated copper powder. The type of SPE disk, eluents as well as solution parameters including pH value, and concentrations of salts and humic substances were examined for the efficiency of the method. The recoveries of all pesticides were in relatively high levels, ranging from 75 to 97% for waters and 71 to 84% for sediment samples. Both methods were applied to real water and sediment samples and the presence of the tested compounds was investigated.     

Determination of volatilization (dissipation) and secondary deposition of pesticides in a field study using passive dosimeters

The volatilization and secondary deposition of the herbicides prosulfocarb and pendimethalin were measured using passive dosimeters with Chinese cabbage and soil as collective material. Passive dosimeters were placed in the field before spraying and at three distances downwind after spraying. The volatilization of prosulfocarb and pendimethalin determined as dissipation was 80 and 60% of the applied amount from the cabbage surface, while no significant loss was measured from soil surfaces after 48?h. The secondary deposition of prosulfocarb and pendimethalin 25?m from the spray zone was 2 and 4% on the leaf surface as well as on the soil surface. At 5?m distance, 6 and 10% of the field dose of prosulfocarb and pendimethalin could be determined on dosimeters with leaves, and 4 and 8% of the field dose could be determined on soil surfaces.     

Catalytic Activity of Bimetallic (Ruthenium/Palladium) Nano‐alloy Decorated Porous Carbons Toward Reduction of Toxic Compounds

Chicken feather‐derived high‐surface‐area porous activated carbon (CFAC) material was prepared using chemical activation. A new composite composed of Ru‐Pd nanoparticles supported on CFAC (Ru‐Pd@CFAC) has been prepared by microwave‐thermal reduction in the presence of the support. Characterization by XRD, Raman, BET, FE‐SEM/TEM, FT‐IR, TGA, XPS, HAADF‐STEM‐EDS, H₂‐chemisorption, H₂‐TPR, and ICP‐AES was used to analyze the catalyst. This catalyst is found to be efficient for the reduction of hexavalent chromium (Cr^VI), potassium ferricyanide (K₃[Fe(CN)₆]), 4‐nitrophenol (4‐NP), and pendimethalin (PDM), at room temperature, and remains stable, even after several repeated runs. Moreover, it showed excellent catalytic activity compared with the monometallic counterparts.