Distribution of pesticide residues in soil and uncertainty of sampling

Pesticide residues were determined in about 120 soil cores taken randomly from the top 15 cm layer of two sunflower fields about 30 days after preemergence herbicide treatments. Samples were extracted with acetone-ethyl acetate mixture and the residues were determined with GC-TSD. Residues of dimethenamid, pendimethalin, and prometryn ranged from 0.005 to 2.97 mg/kg. Their relative standard deviations (CV) were between 0.66 and 1.13. The relative frequency distributions of residues in soil cores were very similar to those observed in root and tuber vegetables grown in pesticide treated soils. Based on all available information, a typical CV of 1.00 was estimated for pesticide residues in primary soil samples (soil cores). The corresponding expectable relative uncertainty of sampling is 20% when composite samples of size 25 are taken. To obtain a reliable estimate of the average residues in the top 15 cm layer of soil of a field up to 8 independent replicate random samples should be taken. To obtain better estimate of the actual residue level of the sampled filed would be marginal if larger number of samples were taken.     

Optimization and characterization of the formation of oil-in-water diazinon nanoemulsions: Modeling and influence of the oil phase,surfactant and sonication

Nanoemulsions are particularly suitable as a platform in the development of delivery systems for lipophilic functional agents. Current research describes the formation of oil-in-water (O/W) diazinon nanoemulsions using synthetic and natural additives by adopting a high-energy (ultrasound) emulsification method. The diazinon nanoemulsions were spontaneously formed by adding dropwise a mixture of diazinon, solvent and co-solvent in an aqueous solution containing a surfactant (tween or lecithin) with continuous stirring. The nanoemulsions were then formed by ultra-sonication. The effects of three levels of active ingredient, solvent, co-solvent, surfactant, sonication time and sonication cycle and power were performed by Minitab software to design the experiment. Effects of these factors on droplet size, polydispersity index (PDI), viscosity and pH of nanoemulsions were investigated. The results of the modeling showed that the experimental data could be adequately adapted in a second-order polynomial model with a multiple regression coefficient r² of 0.821 for the prediction of particle size, PDI and viscosity. The long-term and thermodynamic stability of the prepared nanoemulsions were tested. The droplet size and morphology of the nanoemulsions were measured by dynamic light scattering (DLS) and transmission electron microscopy (TEM). On this basis, a water-insoluble insecticide diazinon was incorporated into 26 optimized nanoemulsion systems to demonstrate potential applications in pest control. The results of DLS and TEM measurements showed that most of prepared nanoemulsions had an almost monodisperse droplet size distribution (PDI < 200 nm). Incorporation of diazinon had no significant effect on the size and stability of the nanoemulsions and the formulated nanoemulsion remained stable after four months of storage.     

复合柱净化法分析生物试样中残留的有机氯农药

用复合柱净化法分析生物试样中残留的有机氯农药,采用复合柱将少量硫酸含量较低的硅胶放在适量的硫酸含量较高的硅胶上,并将去活化硅胶复合在同一根柱子内,有效地避免了浓缩后的提取液与硫酸含量较高的硅胶直接接触时发生的板结现象。该方法对生物试样中8种有机氯农药六六六和滴滴涕的净化效果较好,当农药六六六和滴滴涕的标准加入量为200μg／kg和50μg／kg时,各目标物的平均回收率为63．9％～79．8％,相对标准偏差为5．6％-12．8％,检出限为0．001-0．040μg/kg。     

High-performance liquid chromatography (HPLC) as a tool for monitoring the fate of fluazinam in soil

Fluazinam is a widely used pesticide employed against the fungal disease late blight in potato cultivation. A specific, repeatable, and rapid high-performance liquid chromatography (HPLC) method utilizing a diode array detector (DAD) was developed to determine the presence of fluazinam in soil. The method consists of acetonitrile (ACN) extraction, clean-up with solid-phase extraction (SPE), and separation using a mobile phase consisting of 70% ACN and 30% water (v/v), including 0.02% acetic acid. HPLC was performed with a C18 column and the detection wavelength was 240 nm. The method was successfully applied to an incubation experiment and to soil samples taken from potato fields where fluazinam had been applied two to three times during the on-going growing season. In the 90-day incubation experiment, analytical standard fluazinam and the commercial fungicide Shirlan^® were added to soil samples that had never been treated with fluazinam, and were then extracted with ACN and 0.01 M calcium chloride (CaCl₂). Fluazinam was not extractable with CaCl₂, indicating that it does not leach to watercourses in the dissolved form. Recovery with ACN extraction for sandy soils was 72–95% immediately after application and 53–73% after 90 days of incubation. Out of the eight potato field soil samples, fluazinam was found in two samples at concentrations of 2.1 mg kg^?1 and 1.9 mg kg^?1, well above the limit of quantification (0.1 mg kg^?1).     

Behavior of dialifor,dimethoate, and methidathion in artificially fortified grape juice processed into wine

Abstract

Dialifor and methidathion were added to diluted “Zinfandel”; grape concentrate at 25 ppm and dimethoate at 1.0 and 25 ppm prior to fermentation with Saccharomyces cerevisiae. The finished wine 56 days later contained 10% (2.5 ppm) of the dialifor, 46% (12 ppm) of the methidathion and 85% (21 and 0.98 ppm) of the dimethoate added to the grape must. Residues in wine stored at 24°C dissipated by hydrolysis; half‐lives in wine were 7 days for dialifor and methidathion and 30 days for dimethoate. Residues were unchanged in wine in frozen storage for one year. Analysis of seven commercial wines for dimethoate indicated less than 0.03 ppm dimethoate was present; identity could not be confirmed by thin‐layer chromatography at this level.     

Secretory expression of organophosphorus hydrolase OPHC2 in Yarrowia lipolytica Polg

In the present study, recombinant organophosphorus hydrolase OPHC2 was successfully produced by Yarrowia lipolytica and purified. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and western blot analyses showed a major polypeptide band of 36 kDa. The purified enzyme was optimally active at 65°C and pH 8.5 and also displayed good thermal and pH stability using methyl parathion (O,O-dimethyl-O-4-p-nitrophenyl phosphorothioate) as a substrate. Moreover, as Y. lipolytica is a non-pathogenic, generally regarded as safe (GRAS) yeast, the cell culture supernatant can be used directly on vegetables and fruits that are contaminated by organophosphorus pesticides.     

Review of advances in the thin layer chromatography of pesticides: 2012–2014

Publications reporting techniques and applications of thin layer chromatography (planar chromatography) for the separation, detection, qualitative, and quantitative determination, and preparative isolation of pesticides and their metabolites are reviewed for the period from November 1, 2012 to November 1, 2014. Analyses are described for a variety of sample types and pesticide classes. In addition to references on residue analysis, studies such as pesticide structure – retention relationships, identification and characterization of natural and synthesized pesticides, metabolism, bioactivity, degradation, soil mobility, and lipophilicity are covered.     

Evaluation of pressurized liquid extraction for the analysis of four pesticides in unpolished rice

The aim of to evaluate efficiency of this study was extraction pressurized liquid extraction (PLE) for the analysis of four pesticides, fthalide, etofenprox, fenitrothion, and isoprothiolane, in unpolished rice by comparing with homogenization as a reference technique. The concentrations of four selected pesticides obtained by PLE with acetonitrile at 130°C for 10 min × 2 cycles were comparable to those by homogenization with water-soaking. The repeatability of the analysis, represented as relative standard deviations (RSDs), were 1.4–3.6% (n = 3) for PLE at 130°C and 1.2–3.8% (n = 3) for homogenization with water-soaking. Recovery yields of surrogates were 75–88% and 87–109% for PLE at 130°C and homogenization with water-soaking, respectively, and these were satisfactory according to the method of positive list. This study suggested that PLE can be applied for the analysis of selected four pesticides in unpolished rice as well as homogenization with water-soaking.     

强化微电解法预处理难降解农药废水

为了更好地发挥微电解法预处理难降解农药废水的效能,对其进行强化研究。针对某难降解农药废水,考察了Cu/Fe双金属体系、Ni/Fe双金属体系、添加MnO2催化剂及超声波、电解与铁炭分别结合这5种强化途径去除COD的效果。结果表明,这5种强化途径对污染物的去除率分别为72.3%、68.0%、67.8%、70.0%和76.8%,相比于单独微电解,COD去除率均有较大提高。结合经济成本的考虑,镀Cu双金属微电解体系能够实现经济高效地预处理农药废水。     

Effect of triazophos,fipronil and their mixture on miRNA expression in adult zebrafish

MicroRNA (miRNA) plays a crucial role in gene expression regulation. However, no data are available on change of miRNA expression of zebrafish (Danio rerio) after treatment with pesticides. We evaluated the effect of fipronil (5-amino-1-[2, 6-dichloro-4-(trifluoromethyl) phenyl]-4-[(trifluoromethyl) sulfinyl]-1H-pyrazole-3-carbonitrile) and triazophos (3-(O, O-diethyl)-1-phenyl thiophosphoryl-1, 2, 4-triazol) and their mixture on miRNA expression in zebrafish. MiRNA expression profiles in zebrafish were altered after treatment with these chemicals. An association between these chemicals and the expression of 21 miRNAs was found 96 h after treatment. Among them, 14 miRNAs were differentially expressed due to the treatments with fipronil, triazophos and their mixture; 5 miRNAs showed altered expression level after treatment with formulations of these chemicals; miR-29b and miR-738 were differentially expressed after treatment with adjuvants. MiRNAs might present a novel toxicological response that could be used as a toxicological biomarker and have a different direction for future investigations of their association with miRNAs involved in chemical related diseases.