Detection Of 2,4-D Residue In Milk Based On Surface-Enhance Raman Spectroscopy Technology

Recently,the milk industry has been greatly enhanced owing to the high content of essential nutrients and steps to ensure the quality meets the human needs.The per capita consumption of milk has greatly increased;therefore,considerable interest has been oriented to monitor its quality and safety of milk has also attracted much attention.Food chain and bioaccumulation effect are the main causes of pesticide residues in milk,and the problem of pesticide contamination in milk has raised awareness and concerns among the public.At present,the conventional methods for detecting agricultural residues can achieve sensitive detection,but most of these methods require professional training of operating experimenters and expensive detection instruments,which increases the cost of detection.Therefore,simple,low-cost,fast and sensitive strategies for the detection of toxic trace substances in milk are highly desired.In recent years,surface enhanced Raman spectroscopy?SERS?has been widely used in life sciences,food safety,environmental detection and national security due to the associated advantages such as simple sample pretreatment steps,fast and sensitivity detection,rich spectral information.Hence,in order to develop new methods for the detection of pesticide residues in milk,the main modes and basic principles of SERS were exploited.On this basis,a series of SERS methods were designed for the rapid and sensitive detection of trace pesticide residues in milk.The details are as follows:1.SERS detection system for 2,4-D in milk based on hollow Au@Ag NFs and magnetic separation.Here,Au@AgNFs was synthesized by galvanic replacement.The SERS signal probe?Au@AgNFs@MBA?was produced by modifying 4-MBA on the surface of Au@AgNFs.Then,Fe₃O₄NPs as SERS signal enrichment nano-probe was synyhesized.The 2,4-D antigen was conjugated to Au@AgNFs@MBA,and 2,4-D antibody was conjugated to Fe₃O₄NPs respectively,to develop Au@AgNFs@MBA-antigen/antibody-Fe₃O₄NPs system.The results showed that the obtained linear detection ranged from 0.001-100?g/mL with a lower limit of detection 0.11 ng/mL and good specificity.The proposed system was validated by the standard HPLC method in terms of student's t-and F-test at 95%confidence.The study demonstrated the developed detection system offer a reliable,sensitive and reproducible platform for the quantitative detection of 2,4-D in milk.2.SERS detection system for 2,4-D in milk based on gold-magnetic nanoparticles MIP technology.Magnetic nanomolecularly imprinted polymers?MNPs@MIP?were prepared by using aminated MNPs nanoparticles as carriers,2,4-D as templates,acrylamide as functional monomers,ethylene glycol dimethyl acrylate?EGDMA?as crosslinking agent and azodiisobutyronitrile?AIBN?as the initiator.The synthesized MNPs@MIP combined with AuNPs were used to adsorb 2,4-D at different concentrations.The SERS spectra of gold nanoparticles were collected.The results show that 2,4-D linear detection ranged from 0.1 to10⁶ ng/mL with detection limit of 0.00147 ng/mL.The proposed strategy was validated by the standard HPLC method in terms of student's t-and F-test at 95%confidence.The results show that the established detection system can be used for the quantitative detection of pesticide residues in milk.3.SERS detection system for 2,4-D in milk based on AuMFS label-free sensor coupled with chemometrics.AuMFS was synthesized as a SERS sensor through self-assembly.Thereafter,the SERS spectrum of different concentrations of 2,4-D extracted from milk was collected and analyzed by variable selection algorithms-genetic algorithm-PLS?GA-PLS?,competitive-adaptive reweighted sampling-PLS?CARS-PLS?and ant colony optimization-PLS?ACO-PLS?to develop quantitative models for 2,4-D prediction.Based on the results,CARS-PLS was established and identified as the optimum model with an obtained LOD of 0.01ng/mL in the linear range 10^-22 to 10^-66 ng/mL and realized a determination coefficient in the prediction set of?R_P?=0.9836.The applicability of the sensor was validated by the standard HPLC method in terms of student's t-and F-test at 95%confidence.AuMFS SERS sensor combined with CARS-PLS could be employed for rapid quantification of 2,4-D extract from milk,thereby ensuring a robust and accurate platform for its quality and safety monitoring.