Solid Phase Microextraction Based Magnetic Relaxation Switch For Pesticide Residues Sensing

Pesticide residues in fruits and vegetables have always been a hot issue concerned by the whole society,and it is also a major obstacle to the further development of fruit and vegetable enterprises in China.In view of the food safety problems caused by pesticide residues in fruits and vegetables,the development of rapid and highly sensitive detection methods is an important means to solve this problem.Sample pretreatment is one of the key factors restricting the speed and accuracy of pesticide residue analysis in fruits and vegetables.Solid phase microextraction(SPME)is an efficient method for sample pretreatment.Compared with traditional sample extraction methods,the biggest advantage of this method is that it can be used for in-situ extraction of pesticide residues in fruits and vegetables,which greatly simplifies the sample pretreatment steps.At the same time,the low-field nuclear magnetic MRS immunosensor has strong anti-interference ability and high signal-to-noise ratio,so it is a promising analysis method.The contents of the full text are summarized as follows:1.Solid phase microextraction technology based on PDMS.Solid phase microextraction is a pretreatment method which integrates extraction,enrichment and purification,in which the key link is the fixed phase of fiber coating.Sol-gel chemistry can adulterate organic compounds into inorganic polymer materials with compact structure and high loading rate of stationary phase.Polydimethylsiloxane(PDMS)is not easily disturbed by matrix components,so it is suitable for the analysis of pesticide residues in complex sample matrix.As a non-polar material,after the fiber coating is prepared by sol-gel method,more kinds of targets can be extracted.The SPME device can be easily combined with GC,and the extraction effect of general fruit and vegetable samples is good.2.Detection of acetamiprid in fruits and vegetables by double enzyme-induced Fe²⁺/Fe³⁺conversion MRS biosensor.Acetamiprid belongs to cholinesterase inhibitor,and a large part of pesticides have this enzyme inhibition.Based on this characteristic,a double enzyme-mediated Fe²⁺/Fe³⁺magnetic relaxation switch sensor was constructed.The"one-step mixing"without washing step was realized,and acetamiprid was determined by using the advantages of enzyme inhibition method and paramagnetic ion signal,with good reproducibility(CV<10%)and high accuracy(RSD=3.8%).Importantly,the enzyme display strategy can detect other pesticide residues by simply replacing the enzyme.3.Detection of Chlorpyrifos by immune MRS Sensor.Based on the previous work and considering the need to further determine the types of pesticides,a new immune MRS sensing method was constructed by combining paramagnetic ion signal output with antigen-antibody recognition by HRP enzyme and amplifying the signal by biotin-streptavidin system.This method makes up for the lack of specificity of Fe²⁺-T₂.Any target can be detected by simply replacing the corresponding antigen antibody group.It has been preliminarily proved to be feasible in combination with SPME extraction,but the specific binding mode still needs to be improved.