Detection Of Mixed Contaminants In Meat Based On LC-MS And Single Molecule Fiuorescence

Among a variety of animal source foods,meat products occupy an important position.Mixed contaminants accumulate during the production,storage,and transportation of meat products,and then threaten human health via food chain enrichment.The development of rapid and reliable screening methods for mixed contaminants has important implications for agricultural development and food safety.In this experiment,a technique based on QuEChERs pretreatment method was developed and LC-Q-TOF/MS was used to detect 126 pesticide residues in chicken.The main steps of this experiment are as follows:(a)Extraction:Acetonitrile was used as the extraction solvent,and the chicken sample is first homogenized and then shaken with the extraction solvent.(b)Decontamination:The purification efficiency of dispersive solid-phase extraction(d-SPE)was assessed by comparing different adsorbent combinations(EMR-Lipid,PSA,C18,PSA + C18,PSA + C18 + GCB).(c)Chromatography mass spectrometry:Use liquid chromatography mass spectrometry with reversed phase chromatography and quantify with external standard method.The final results showed that EMR-Lipid was the most suitable adsorbent,and that more than 90%of the analytes reached a minimum limit of quantification(LOQs)below 10 μg/kg.The recoveries and relative standard deviations(RSDs)were evaluated at three concentrations of 0.05,0.10,and 0.20 mg/kg.At the addition of 0.20 mg/kg,the spike recovery was in the range of 70-120%,and the RSD of most pesticides was less than 15%.The correlation coefficient of the standard curve in this method ranged from 0.9843(fluroxonone)to 0.9999(cyprofen).The detection method has the advantages of rapidness,high throughput and high precision,and can be widely applied to the detection of various pesticide residues in chicken meat.In addition,this experiment establishes a technique for the detection of PCB-77 residues in pork samples based on single molecule fluorescence.The main steps of this experiment are as follows:(a)Modification of the slide:biotin and streptavidin were modified on the surface of the slide to immobilize the nucleic acid probe.(b)Design of the reaction system:biotin-labeled capture probes can be attached to the surface of the decorated slide.The aptamer used to block the capture probe can specifically bind to PCB-77.When PCB-77 is present in the reaction system,the aptamer will detach from the capture probe.At this point,the fluorescent probe can bind unstably to the exposed capture probe,resulting in a change in the fluorescence state.(c)Detection of PCB-77:Using a total internal reflection microscope to observe fluorescence changes at single molecular sites,a standard curve was drawn based on the number of single-molecule sites and the concentration of PCB-77 in the system to achieve the quantification of PCB-77.The final results showed that the experimental results were most satisfactory when a 10 nt fluorescent probe was used in a 2×PBS buffer solution.Nucleic acid aptamers are inexpensive and have good specificity.Under the optimized conditions,PCB-77 was added to the actual pork samples for recovery testing.The final recoveries ranged from 76.58%to 103.63%.The detection method can effectively eliminate background interference and reduce the detection limit of the method.