Study On Detection Of Chlorothalonil And Its Degradation Products In Pakchoi By MISPE-HPLC

With the development of human society and the improvement of people's living standards,food safety issues have received more and more attention and pesticide residues are particularly prominent in food safety issues.Pesticide residues in vegetables are more serious,and food safety problems caused by unreasonable use of pesticides occur frequently.Organochlorine pesticide chlorothalonil(CHT)is often used to control fungal diseases of vegetables.The use of CHT brings enormous benefits to agricultural production,and the toxicity of its maternal residues and degradation products has attracted wide attention.A method for rapid simultaneously separating and detecting CHT and its degradation products in vegetables needs to be established.This thesis aims to prepare molecularly imprinted polymers(MIPs)which can simultaneously adsorb CHT and its four degradation products(trichloro-1,3-isophthalonitrile,dichloro-1,3-isophthalonitrile,mono-chloro-1,3-isophthalonitrile and 4-hydroxy chlorothalonil)by using CHT as a template molecule,and optimize the conditions for preparing polymeric materials.Molecularly imprinted solid phase extraction column(MISPE)was prepared by using this polymer as a filling material.Combined with high performance liquid chromatography(HPLC),CHT molecular imprinted solid phase extraction-high performance liquid chromatography(MSPE-HPLC)was established.Providing efficient and innovative sample preparation and detection techniques for the simultaneous detection of CHT and its degradation products.The specific research contents are as follows:1.Preparation and evaluation of chlorothalonil molecularly imprinted polymer(CHT MIPs)In this paper,molecularly imprinted polymers were prepared by bulk polymerization.Using chlorothalonil(CHT)as template molecule,acetonitrile as solvent,acrylamide(AM)as functional monomer,ethylene glycol dimethacrylate(EDMA)and azobisisobutyronitrile(AIBN)as cross-linking molecularly imprinted polymers were prepared as initiators and initiators.The CHT:MA:EDMA:AIBN molar ratio is 1:7:40:0.6;the elution time is 30 h,the adsorption solvent is 30%acetonitrile-water solution,and the adsorption temperature is 30?.The morphology of chlorothalonil molecularly imprinted polymer was characterized by scanning electron microscopy(SEM).Adsorption kinetics,static adsorption equilibrium experiments and substrate selectivity experiments were performed to evaluate the adsorption properties of CHT MIPs.2.Preparation of chlorothalonil molecularly imprinted solid phase extraction column(CHT MISPE)Put the MIPs and diatomaceous earth into the solid phase extraction column according to a certain mass ratio.The mass ratio of MIPs and diatomaceous earth,the type and amount of eluent and eluant,and the number of uses were used to influence CHT MISPE.Final determination of diatomaceous earth:mass ratio of MIPs is 1:1;5%methanol-water as eluent;acetone as eluant;eluant is added in 6 times,each dosage is 1.0 mL;the usage limit is 5.3.Establishment of simultaneous separation and detection of chlorothalonil and its degradation products by high performance liquid chromatography(HPLC)Establish HPLC and simultaneously separate and detect CHT and its degradation products,study the UV detection wavelength,mobile phase type and ratio,flow rate and other factors to determine the best separation detection conditions:the detection wavelength is 220nm,236nm,the mobile phase is acetonitrile and water,the mobile phase is gradient eluted,the injection volume is 20 ?L,the column temperature is 25?,the flow rate is 1mL/min,and the method can complete 5 kinds in 30min.Rapid separation of matter.The five drugs have a good linear relationship in the range of 1 mg/L to 100 mg/L,the correlation coefficient(R2)is 0.9961?1.0000,and the relative standard deviation of the peak area RSD(n=6)is 1.05%-4.78%.The RSD(n=6)is between 0.37%and 0.64%,and the LOD(S/N=3)of the method is 0.005 to 0.015 mg/kg.4.Application of chlorothalonil molecularly imprinted solid phase extraction column coupled with high performance liquid chromatography(CHT MISPE-HPLC)in pakchoi samplesThe prepared CHT MISPE was used in the pretreatment of pakchoi samples and analyzed by HPLC.The results showed that the recoveries of CHT and its four degradation products were 80.1%-91.4%,RSD(n=6).It is 1.70%to 7.15%.