Application Of Functional Magnetic Composites In On-line Magnetic Solid Phase Extraction Of Organic Pesticide

Agriculture is an important part of China's production process.Modern agriculture uses pesticides to solve problems such as pests and weeds.However,pesticide residues in the environment can affect human health and cause mild or chronic diseases.In recent years,China has introduced restrictions on the application of pesticides.Therefore,it is important to detect pesticide residues in the environment.On-line magnetic solid phase extraction is a sample pretreatment method which is developed in recent years.Compared with the traditional off-line pretreatment method,it has the characteristics of automation and high precision.In this paper,an online magnetic solid phase extraction device was developed.Two types of functionalized magnetic particles were prepared to enrich the pesticide residues in environmental water samples and quantitative analysis by high performance liquid chromatography.An on-line magnetic solid phase extraction(Online-MSPE)device was that use a peristaltic pump to provide pressure and a six-way valve to switch between injection and elution process.A magnetic particle with a stearyltrimethylammonium-bromide(STAB)modified surface was prepared as an adsorbent by a sol-gel method and used for extraction and preconcentration of two sulfonylurea herbicides(SUHs)(chlorsulfuron and bensulfuron-methyl)in water samples prior to high-performance liquid chromatography.On-line MSPE parameters were optimized,including desorption conditions,adsorbent dose,pH of the sample solution,and injection flow rate.Under the optimum conditions,satisfactory linearity was obtained(correlation coefficients>0.9997).The limits of detection(LODs)of chlorsulfuron and bensulfuron-methyl were 0.32 and 1.12 ?g/L,respectively.The method was successfully applied to determine two sulfonylurea herbicides in three types of environmental water samples.The recoveries of sulfonylurea herbicides were in the range of 70.0%-113.4%.The results confirmed that this method is efficient and simple and has a wide application potential in separation and enrichment of sulfonylurea herbicides in environmental water samples.The magnetic composite particles coated with MIL-53(Fe)were prepared,and on the basis of the on-line pretreatment device established in this paper,the method of detecting four pyrethroid esters in water samples was further explored.Under the optimized condition of on-line magnetic solid phase extraction,the linear correlation coefficient of four target substances is good,r?0.9911,and the detection limit is between 0.31-0.88?g/L.Pyrethroids were not detected in the water samples.In the spiked recovery experiment,the recovery was between 78.8%and 115.8%,and the RSDs were ?6.1%.The method is applicable to different kinds of magnetic composite materials,and thus has certain potential value in practical applications.