| Maize（Zea mays）is the grain crop with the largest planting area and highest average yield per unit area,and is also one of the main feed and food,chemical industry,health care and other vital raw materials for livestock husbandry.A variety of diseases and insect pests will occur during the period from sowing to harvesting of maize.With the implementation of the national"double reduction"policy,the method of seed coating for prevention and control has also attracted much attention.However,there are still some problems in seed coating agent,such as low film-forming efficiency,poor physical and chemical properties,low coating uniformity,high coating shedding rate,poor slow release effect,etc.The most critical part of the inactive components of seed coating agent is film-forming agent,as its stability,slow-release performance,and high efficiency are all determined by the performance of the film-forming agent.In this experiment,four kinds of film-forming agents,YC02-A,YC02-B,YC02-C and D prepared in the laboratory,were taken as the research object.On the basis of evaluating their physicochemical properties and coating performance indexes,the residues of Difenoconazole,Flusilazole and Tebuconazole were determined by high performance liquid chromatography-tandem mass spectrometry（UHPLC-MS/MS）in various parts of maize plants and in soil at different times after coating with four film-forming agents maize seeds.In this way,the effects of different film-forming agents on the slow-release performance of the active ingredients in seed coating agents and the uptake and transport patterns of the three agents in various parts of the maize plant and in the soil were investigated,which can lay the foundation for the subsequent research and development of maize seed coating agents with good slow-release properties,high efficiency and low toxicity.The main research results of this experiment are as follows:1)The results of physical and chemical properties of film-forming agents showed that the solid content,water absorption and swelling rate of film-forming agents YC02-A,YC02-B,YC02-C and D decreased in turn,and the solubility in water increased in turn after72 h.The film forming agents YC02-A,YC02-B,and YC02-C have better film forming performance.After soaking in water for 30 minutes,their dry film can still form uniformly on the glass slide and the film can be completely removed from it.However,the film forming performance of D is poor,and their dry film cannot form uniformly on the glass slide after soaking in water for 30 minutes.The test results showed that the film-forming agent YC02-A had the best physicochemical properties.2)The results of the application performance index of film-forming agents showed that after coating maize seeds with four film-forming agents and three chemicals,the uniformity of film-forming agents YC02-A,YC02-B,YC02-C and D could reach 92%～100%,and the coating shedding rate could be controlled between 2.21%～6.40%,and the average film-forming time was 5.2 min,6.1 min,6.5 min and 7.4 min in order.The average film formation time was 5.2 min,6.1 min,6.5 min and 7.4 min,which was 1.8 min～4 min shorter than the average film formation time of the control（9.2 min）.The film-forming agents YC02-A,YC02-B,YC02-C and D have good initial dry adhesion and the grade is"++".The test results showed that the film-forming agent YC02-A had the best performance and the best combination with tebuconazole for seed coating.3)The confirmatory results of the three residue detection methods showed that the maize seed,whole plant,root,stem,leaf and soil samples could be extracted by acetonitrile.The supernatant was taken after salinization and then detected by UHPLC-MS/MS,and finally quantified by matrix-matched standard external standard method.The average recoveries of diflubenzole in various parts of maize and soil at the spiked levels of 0.05～1mg/kg were 80.72%～105.53%with the relative standard deviations RSDs of 0.5%～8.8%and the correlation coefficients of the standard curves were greater than 0.991.At the addition level of 0.01-2 mg/kg,the average recovery rate of flusilazole in various parts of maize and soil was 93.60%～107.98%,with a relative standard deviation RSDs of 0.5%～6.8%.The correlation coefficient of the standard curve was greater than 0.998;The average recovery rate of tebuconazole in various parts of maize and soil is 79.80%～108.82%,with a relative standard deviation RSDs of 0.5%～8.1%.The correlation coefficient of the standard curve is greater than 0.999.The recoveries and relative standard deviations RSDs of the three agents in the range of spiked levels met the conditions according to the requirements of the detection analysis.The test results showed that the assay can be applied to the determination of the residues of difenoconazole,flusilazole and tebuconazole in maize seeds,plants and soil.4)The results of the determination of the residues of the agents in the samples at different periods showed that the distribution and residues of tebuconazole,flusilazole and tebuconazole in various parts of maize plants and soil at different periods after the application of the film-forming agents YC02-A,YC02-B,YC02-C and D to the seed coating of maize were different between the dosages of 0.8 g/100 g seeds and 1.0 g/100 g seeds.The differences in distribution and residues of the three agents in different parts of the maize plant and in the soil were related to the nature of the agents and the slow-release properties of the film-forming agent.The distribution and residue amounts of the three agents in various parts of maize plants and soil were generally C tebuconazole>C flusilazole>C tebuconazole,and the residue times of tebuconazole,flusilazole and tebuconazole in various parts of maize plants and soil were different,from longest to shortest in order of root>stem≈leaf>soil.The test results showed that the film-forming agent YC02-A had the best slow-release property among the four film-forming agents,and there were differences in the transport ability of the three agents,with tebuconazole,flusilazole and tebuconazole decreasing in upward transport ability,tebuconazole being able to transport upward but also accumulating in the roots,flusilazole accumulating mainly in the roots,and tebuconazole basically not transporting upward and accumulating only in the roots.The above research results show that the film-forming agent YC02-A has better physical and chemical properties and coating performance indexes.It also has better slow-release property,which is very important to improve the effect of seed coating agent.It can achieve the effect of improving the high efficiency and stability of seed coating agents and extending their drug retention period without increasing the dosage. |
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