Preparation Of Composite Nanoparticles/Nanosheets And Its Application In The Detection Of Pesticide And Veterinary Drug Residues

Pesticides and veterinary drugs can increase the yield and quality of agricultural products.Irregular use of pesticides can cause problems with pesticide residues.When these residues enter the body through the food chain,they can have adverse effects on health.In order to control and detect the residual contaminants in food,some countries have established maximum residue limit standards for these targets to guide analytical testing.Testing methods used in the laboratory are characterized by high throughput,high selectivity,and high sensitivity.However,there are also disadvantages such as complex pretreatment methods,large and expensive instruments and professional operators,and the use of large numbers of toxic reagents.Regarding above the issue,this research,with pesticides and veterinary drugs as the research goals,using gas chromatography-tandem mass spectrometry,liquid chromatography,and fluorescence spectrophotometry as detection instruments,combined with nanomaterials,developed modified magnetic solid-phase extraction to detect pesticide residues,established a new dispersive solid-phase extraction method for?-lactam antibiotic residues,and builted a method to detect methyl parathion residues by enzymatic hydrolysis fluorescence sensor.In laboratory testing,these methods for maximum residue limits for pesticide and veterinary drugs were achieved by reducing pretreatment time,using small and commonly used testing equipment,and fast and inexpensive optical detection methods.It provides a reference for the detection of pesticide and veterinary drug residues.The experimental results are as follows:1.Based on using the prepared Fe₃O₄@SiO₂-PAAA as adsorbent,a modified QuEChERS method was established to detect multiresidues of 7 pesticides with different properties in fruits and vegetables by GC-MS/MS.Magnetic nanomaterials were characterized by transmission electron microscopy?TEM?,Fourier infrared spectroscopy?FI-IR?,X-ray photoelectron spectroscopy?XPS?,and zeta potential.The interference after co-extraction purification were compared by total ion chromatogram and the effect of purification of different adsorbents were investigated by spiking recovery experiment;the amount of purification agent and purification time were optimized,and the best analysis method was established;and was validated and the real samples were deteced.The results show that the linear range of the method is 0.007-1.0 mg kg^-1;the limit of detection is 0.002-0.005 mg kg^-1;and the limit of quantification is 0.007-0.017mg kg^-1.This method can be successfully applied to the detection of pesticide residues in food.2.Based on using the prepared C₁₈/3A-SiO₂ as adsorbent,a method was established to detect 8?-lactam antibiotic residues in milk by liquid chromatography-diode array detector?LC-DAD?.Functionalized silica nanoparticles were characterized by scanning electron microscopy?SEM?and FI-IR.The research compared the effect of purification of functionalized materials with different proportions,optimized the number of extractions,the amount of purification materials,and compared the chromatographic performance of different reconstitution solvents;and validated the method and analyzed the real samples.The limit of detection of the method is 0.5-5?g kg^-1;the limit of quantification is 1.65-16.5?g kg^-1;the linear range is 6.6-1000?g kg^-1.This method can replace the detection method for the analysis of?-lactam antibiotics by LC-MS/MS.3.A simple chemical oxidation,thermal oxidation etching and ultrasonic exfoliation method were used to prepare two-dimensional ultra-thin graphite carbon nitride nanosheets?g-C₃N₄ NNs?.The prepared g-C₃N₄ NNs have strong fluorescence and excellent salt resistance.Based on the p-nitrophenol,hydrolysis product of organophosphorus,which can quench the fluorescence of g-C₃N₄ NNs,a fluorescent switch sensor was designed to detect methyl parathion.The concentration range for methyl parathion is 0.2-10?M,and the limit of detection is 0.2?M.The method has been applied to detect methyl parathion in fruits and vegetables with satisfactory results.