Preparation Of Composites Based On ZIF-8 And Their Applications In The Analysis Of Pesticide Residues

Due to the long-term use of pesticides,the pesticide residues caused by the pesticides has huge harm to food safety and ecosystem.Development of reliable,efficient and sensitive pesticide residue determination methods is of great significance for controlling the quality and safety of agricultural products.Sample pretreatment is the key to pesticide residues determination,and the adsorption materials plays a vital role in the sample pretreatment process.ZIF-8 is a kind of metal organic framework material,which has the advantages of permanent porosity,high chemical stability and thermal stability,low cost and easy to obtain in theory,and is widely used in the field of pesticides adsorption and separation.In the paper,based on the ZIF-8 material,three kinds of composite materials were prepared by means of different modification methods and three sets of pretreatment techniques were established.Finally the prepared composites were applied to the determination of pesticides in different samples.The details and results are as follows:1.A magnetic ZIF-8 composite has been prepared by co-precipitation method as a cleaning agent of the QuEChERS.The results of the optimization of pretreatment conditions show that,when the amount of magnetic ZIF-8 was 20 mg,the recovery rate comparable to that of C18 or PSA in different sample matrices.The result of validation show that this method has a good linearity(R²?0.9934,among them,the linear range of sulfathion is 5-500?g L^-1,the linear range of methyl parathion and fenvalerate is 1-500?g L^-1,and the linear range of the other 15 pesticides is 0.5-500?g L^-1),good reproducibility?Intra-day RSD?5.4%,inter-day RSD?7.7%?,and the range of LOQ was 1-50?g L^-1.Finally,the method has been successfully applied to the determination of 18 pesticide residues in five kinds of fruit?vegetable?beverages.The results shows that at two marking levels,the average recovery rate of 18 kinds of pesticides was84.4%-97.3%and the RSD was 0.4%-15.7%.2.A type deep eutectic solvent?1-methyl-3-octyl imidazolium chloride-undecanol?-modified magnetic ZIFs?M-ZIF-8@DES?Imidazolium-type??was prepared and employed as an adsorbent for MSPE.The results show that the M-ZIF-8has large surface area?96.83 m2/g?and pore size?0.292 mL/g?,excellent magnetic properties?61.3 emu/g?and can be successfully applied to MSPE of pyrethroid pesticides.The method has wide linear range(1-400?g L^-1,R²?0.9912),low LOD(0.05-0.21?g L^-1)and good precision?Intra-day RSD?7.9%,inter-day RSD?9.4%?.The method was successfully applied to the determination of pyrethroid pesticides in real environmental water samples and the results show that the recovery rate of target pesticides was between 81.1%and 97.6%,and RSD was less than 8.2%.3.In order to expand pesticide quantity and application of ZIF-8 in complex matrix samples,a new type deep eutectic solvent?tetrabutyl ammonium chloride-dodecanol?-modified magnetic MWCNTs-ZIF-8?M/M-ZIF-8@DES?Quaternary ammonium salt-type??was prepared and employed as an adsorbent for MSPE.The materials characterization results show that M/M-ZIF-8@DES?Quaternary ammonium salt-type?has high superparamagnetism?51.3 emu/g?,large specific surface area?133.68 m²/g?and pore volume?0.574 mL/g?,which can meet the MSPE requirements of pyrethroid pesticides.The results of optimization experiment show that DES which consisted of tetrabutyl ammonium chloride and 1-dodecanol was selected as best one for the next experiment and the adsorption properties of M/M-ZIF-8@DES?Quaternary ammonium salt-type?were higher than those of M-MWCNTs-ZIF-8 and M-MWCNTs.The validation results show that the method has wide linear range(0.5-400?g L^-1,R²?0.9905),low LOD(0.08-0.33?g L^-1)and good precision?Intra-day RSD?5.6%,inter-day RSD?8.6%?.The method has been successfully applied to the determination of pyrethroid pesticides in three tea drink samples and the results show that the recovery rate was between 70.4%and 96.4%,and RSD was less than 10.0%.