Research On Detection Of Pesticide Residues Based On Molecular Imprinting-surface Enhanced Raman Scattering

Surface-enhanced Raman scattering?SERS?has been widely used in environmental chemistry,explosives detection,food safety,biomolecules and forensic medicine owing to its fast,convenient,high sensitivity and on-site detection.SERS has shown some advantages in the detection of pollutants such as pesticide residues,but many studies are limited to simple substrates.And,SERS still faces great difficulties in the analysis of pollutants in complex matrices.Meanwhile,SERS signals of some pollutants are weak,the sensitivity can not meet the requirement of maximum residue limit.Therefore,the study had developed some methods for SERS detection of pesticide residues combining the specific recognition performance of molecularly imprinted polymers?MIPs?and the advantages of SERS signal amplification probes to provided new ideas for food safety detection technology.The main contents and conclusions of this research are as follows:?1?To solve the problem that SERS is seriously affected by matrix interference,the MIPs that specifically recognized prometryn and simetryn was designed and synthesized.The polymer had high selectivity for,and the imprinting factor?IF?was as high as 5.3 and 4.2 respectively.The Scatchard equation and the kinetic model showed that MIPs had two kinds of binding sites for two pesticides and the dynamic recognition mechanism was second-order kinetic model.Gold nanoparticles?Au NPs?SERS-enhanced substrate with good stability and high enhancement performance was prepared.The effects of Au NPs with different particle sizes and different coagulants on SERS"hot spots"were analyzed.The 974 cm^-1 and 1074 cm^-1 were comfirmed as the quantitative peaks in the high specificity fingerprint of pesticides.We studied the the effects of different matrices on SERS signal.The high-efficiency purification pretreatment technology of QuEChERS intergrated with MIPs was screened out for rice and wheat.The SERS method for the detection of prometryn and simetryn residues in wheat and rice samples was established.The methodological evaluation showed that the method had a good linear correlation in the range of 0.05-1 mg/L for both pesticides,the limits of detection?LOD?were0.02 mg/L,and the recoveries?%?of three spiked levels were 72.7-90.2%.the relative standard deviation?RSD?was 1.7-7.8%,and the results were in good consistency with HPLC-MS/MS,and could be used for the simultaneous determination of prometryn and simetryn in real samples.?2?To solve the problem that the SERS signals of some pesticides are weak and the signals are difficult enhanced,a biomimetic mimic enzyme-linked colorimetric/SERS rapid detection method for triazophos was established.The method integrated the molecular imprinted array membrane as the identification element,the mimetic enzyme signal amplification complex probe and the Au NPs@MIL-101 SERS substrate.The triazophos molecular imprinted array membrane was synthesized by“grafting to”method.The membrane was more uniform and environmental-friendly than in-situ polymerization.The Au NPs@MIL-101 SERS substrate was synthesized by in-situ reduction method to enhance the stability of Au NPs.The mimetic enzyme platinum nanoparticles?Pt NPs?were prepared by sodium citrate reduction method.Bovine serum albumin?BSA?was as a"linkage bridge"to combine the Pt NPs@BSA-triazophos hapten for forming mimetic enzyme signal amplification complex probe.The competitive response mechanism of the composite probe was explored.Under the optimal conditions,methodological evaluation showed the LOD,IC₁₀ and IC₅₀ values of colorimetric were 1,8.1,112?g/L respectively,and the linear range was 5-1000?g/L,while the LOD of the SERS method was 1?g/L,and the linear range was 1-10000?g/L;interference study showed that MIPs and the probe achieved double selectivity for triazophos detection,which could be successfully applied to the determination of triazophos in water and pear samples.The recoveries?%?were 65.6-110.7%with the RSD of 7.8-15.2%.?3?Based on the theory of surface plasmon resonance?SPR?signal enhancement technology and structural analog labeled probe competition identification technology,a dual-mode synchronous detection technique combing SPR specific recognition with SERS signal amplification was explored.The correlation between Au NPs particle size and SERS signal of reporter was studied,and 4,4?-bipyridyl was selected as the best SERS reporter,and the key mechanism of pH on different carrier protein,SERS reporter and complex labeld probe was analyzed.The characteristic peaks of the synthetic Au NPs/4,4?-bipyridine/BSA-target hapten complex labled probe at pH 4.4 of Au NPs and0.004 mol/L concentration of 4,4?-bipyridine showed highest signal with the best stability.The molecularly imprinted SPR chip prepared by electrochemical deposition method and“grafting to”method was fabricated.The recognition performance of the chip on pesticide molecules and complex labled probe was verified.The complex labled probe not only had the SERS signal,but also enhanced the response signal of SPR.The optimal buffer system and sample dissolution system of SPR-SERS were screened and optimized.As a result,when the concentration of triazophos was 100 mg/L,the of refractive indexof SPR was 1RU,and the for the complex labled probe was 23 RU.After competing with the pesticide?1 mg/L?,D-value reduced to 4.5,and the characteristic peak of the SERS reporter appeared at 1612 cm^-1.The above results laid the foundation for further research on SPR-SERS combined technology for pesticide residue detection.