Investigation and Analysis of Pesticide Residues in Four Common Vegetables and Risk Assessment of Dietary Exposure in Ceramic Capital, China.

In order to understand the basic situation of pesticide residues in vegetables in China's porcelain capital, four kinds of common vegetables on the market were selected in this study for detection and analysis of pesticide residues. The pesticide residues in vegetables were analyzed through sample selection, optimization of instrument and equipment conditions, and comparison of detection pass rates. The sampling locations were common vegetables purchasing places such as large and medium-sized supermarkets. QuEChERS method was used as the sample pretreatment, and gas chromatography (GC-MS/MS) was used for quantitative analysis. Finally, the exposure risk of pesticides was assessed according to the test results. The results showed that all the pesticides were detected in four kinds of vegetables, but the detected pesticides did not exceed the national standard (GB 2763-2014, China). Moreover, the target risk coefficient (THQ) and risk index (HI) values of four vegetables were less than one, indicating that the combined and toxic effect of pesticide residual mixed contamination was smaller in four vegetables. Therefore, there was no significant harm from people using these vegetables.

Degradation of a Novel Pesticide Antiviral Agent Vanisulfane in Aqueous Solution: Kinetics, Identification of Photolysis Products, and Pathway.

Hydrolysis degradation kinetics of vanisulfane in water was investigated in detail under exogenous substances conditions. The experimental results indicated that the degradation rate of vanisulfane in aqueous solution increases with the increase of concentration of Cu2+. The degradation of vanisulfane did not change significantly in Ni2+, Zn2+, Pb2+, and Fe3+ aqueous solutions. Surfactants have no significant effect on the degradation of vanisulfane, and the degradation rate of vanisulfane increases with increasing concentration of fulvic acid. In addition, the photolysis products were identified by ultra-high-performance liquid chromatography coupled with Orbitrap high-resolution mass spectrometry. Five photolysis products were identified, and the degradation reaction pathway and the mechanism of vanisulfane were proposed, which mainly involved cleavage of thioether, back into aldehyde, cleavage of ether bond, demethylation, and intramolecular dehydration processes. This research on vanisulfane can be helpful for its security evaluation and increased understanding of vanisulfane in water environments.

Qualitative and Quantitative Analysis of the New Sulfone Bactericide 2-(4-Fluorophenyl)-5-(Methylsulfonyl)-1,3,4-Oxadiazole and Identification of Its Degradation Pathways in Paddy Water.

Rapid and simple methods for the determination of Jiahuangxianjunzuo (JHXJZ) in paddy water, brown rice, soil and rice straw was developed and validated. This method involved the use of ultrahigh-performance liquid chromatography equipped with photodiode array detector. The most important factor was chromatographic conditions, as identified through an orthogonal experimental design. This method showed good recoveries and precisions, thereby indicating its suitability for monitoring of JHXJZ residues in paddy water, brown rice, soil and rice straw. Furthermore, hydrolysis experiment was conducted in the laboratory under pH = 7 buffer solutions, and its degradation product was identified as 2-(4-fluorophenyl)-5-methoxy-1,3,4-oxadiazole by high-resolution mass spectrometry. JHXJZ has a major degradation pathway in the water which the OH- nucleophilic attack the C5 of 1,3,4-oxadiazole ring. Then it leaves mesyl to form intermediate 5-(4-fluorophenyl)-1,3,4-oxadiazol-2-ol and the intermediate combined with methanol formed the degradation product 2-(4-fluorophenyl)-5-methoxy-1,3,4-oxadiazole by the loss of one H2O.The degradation pathways of JHXJZ under the present indoor simulation conditions were proposed.

Determination, risk assessment and processing factors for pyridaben in field-incurred kiwifruit samples.

Field trials in six agricultural sites were carried out to investigate the dissipation and residue levels of pyridaben in kiwifruit. Each sample was extracted with acetonitrile, purified with octadecylsilane and analyzed with high-performance liquid chromatography-tandem mass spectrometry. The method had good linearity (R2 > 0.99), accuracy (recoveries of 78.53-98.00%) and precision (relative standard deviation of 0.86-6.11%). The dissipation of pyrdaben in kiwifruit followed first-order kinetics with a half-life < 8 d, and terminal residues in kiwifruit were lower than 0.5 mg/kg after 14 d of application. Risk assessment indicated that both chronic and acute dietary intake risk values were far below 100%, suggesting that pyridaben residues in kiwifruit were relatively safe to humans. Moreover, the effects of traditional household processes on kiwifruit were investigated. The processing factors (PFs) indicated that peeling and peeling-juicing processes could remove pyridaben residues from kiwifruit, and the former was more effective than the latter (PF at 0.15 vs. 0.51). Nevertheless, drying kiwifruit with an oven increased the amount of pyridaben (PF at 1.05). These results could provide guidance for the safe and reasonable use of pyridaben in agriculture and may be helpful for the Chinese government to determine maximum residue limit of pyridaben in kiwifruit.

Effects of mineral oil spray additives on the distribution and dissipation kinetics of pyraclostrobin and azoxystrobin in banana leaves, fruits, and soil.

Using LC-MS/MS, a rapid and sensitive method for the simultaneous determination of pyraclostrobin and azoxystrobin residues in banana matrices (leaf and whole banana) and soil was established. The samples were extracted using acetonitrile and purified through C18 dispersive solid-phase extraction. The average recovery of the analytes in various matrices was in the range of 77.3%-103.9% with an RSD range of 0.9%-9.5%. The initial deposition amounts of pyraclostrobin and azoxystrobin at 2 h in the banana leaves of the mineral oil group were 1.43 and 1.31 times in Guangxi, and 2.10 and 1.81 times in Hainan for the water group, whereas those in the soil of the water group were 3.45 and 3.03 times in Guangxi, and 2.14 and 3.48 times in Hainan for the mineral oil group. The half-lives in the leaves and soil of the mineral oil group were not remarkably different from those of the water group. The terminal residue of the analytes on the whole banana was <0.02 mg/kg at 14 days after application from the two sites. The results of this work may indicate and promote the safety of using pyraclostrobin and azoxystrobin in banana production, especially with mineral oil spray adjuvants.