| In modern agriculture,pesticides can increase agricultural production by reducing the risk of pests and diseases.however,due to its bioaccumulation,pesticides will lead to excessive pesticide residues in crops and the environment,and even causeharm tohumanhealth.In order to ensure the standardized use of pesticides,Chinahas established 4,140 limit standards for 433 pesticides in different sample substrates in GB2763-2016.At present,the determination methods of pesticide residues in vegetables generally have many difficulties such as low detection efficiency,low concentration of substances to be tested,complex sample matrix,and many interfering substances.Therefore,it is essential to establish a rapid andhigh-throughput method for detecting a variety of pesticide residues in vegetables.This thesis mainly uses ultra performance liquid chromatography-mass spectrometry,ultra performance liquid chromatography-tandem mass spectrometry and ultra performance liquid chromatography-time of flight mass spectrometry to establish a rapidhigh-throughput method for the determination of various pesticides in vegetables.The effect of adsorbents and storage conditions on the final results during the detection and analysis of vegetables was also proposed.The idea of establishing a pesticide detection method by low-resolution mass spectrometry combined withhigh-resolution mass spectrometry was also proposed.The main research contents are as follows:1.A method for rapid determination of 15 carbamate pesticide residues in Chinese cabbage and pakchoi by QuEChERS-UHPLC-QDa mass spectrometry was established.Acetonitrile is an extraction solvent,and the laboratory’s self-developed new purification device multi-purpose needle filter purifies the liquid phase with the column CORTECS(?)T3(3.0×150 mm,2.7 μm)and passes the UHPLC-QDa mass spectrometry single-particle scanning mode.Perform a quick assay.The results showed that 15 kinds of carbamate pesticides in cabbage and pakchoi had a good linear relationship(R2≥0.99)at a concentration of 1～100 μg/kg,and the levels were increased at three concentrations of low,medium and high(10,50,200 μg/Kg)The average recovery rate was 68.2%～120.1%,the relative standard deviation was less than 10.6%(n=3),and the method detection limit ranged from 1 μg/kg to 3.5 μg/kg,15 kinds of carbamate pesticides.The limit of quantitation is less than 10 μg/kg.The method is accurate,fast,stable,and suitable for the actual detection of the base layer.2.A method for the determination of 69 pesticides and metabolites in pakchoi by UHPLC-MS/MS was established.The effect of the amount of acetic acid added on the extraction solution was studied.The adsorption of four adsorption materials,such as EMR and ZrO2,was investigated.ability.Finally,the sample was extracted with 15ml 0.1%acetic acid-acetonitrile solution,150mg MgSO4+50mg C1 8+50 mg Zr02+5 mg GCB,and finally 69 kinds of typical pesticides and metabolism of pakchoi and Chinese cabbage by UHPLC-MS/MS.The results showed that the recoveries of 64 typical pesticides in pakchoi and 64 typical pesticides in Chinese cabbage ranged from 70.6%to 125.5%and 69.8%to 116.8%,and the RSD was lower than 1 9.4%and 29.8,respectively.%.Experiments show that the method is fast,efficient,stable and accurate.3.The method of UHPLC-MS/MS detection of 69 typical pesticides was transplanted onto UHPLC-QTOF-MS,and the detection method of 50 kinds of typical pesticides and metabolites in pakchoi was established by UHPLC-QTOF-MS.The results showed that 50 pesticides and metabolites showed good linearity(R>0.99)in the concentration range of 5～200μg/kg,and the recoveries ranged from 65.97%to 129.08 at low,medium and high concentrations,and the RSD was lower than 20%.(n=3).Compared with tandem mass spectrometry,high-resolution mass spectrometry is more suitable for non-targeted screening and characterization of pesticide residues in samples,while tandem mass spectrometry is more suitable for targeted quantitative analysis.Finally,combining the advantages of both,a high-resolution mass spectrometry combined with low-resolution mass spectrometry was proposed to establish a rapid screening method for multiple pesticide residues in vegetables.The method comprehensively scores four parameters including the retention time,accurate mass,isotope abundance ratio and secondary ion fragment mass spectrum of the target.The comprehensive score is greater than 60,which is regarded as a suspicious target.The positive samples were detected by multi-reaction monitoring(MRM)scanning mode of low-resolution mass spectrometry,and the target was confirmed and quantified.4.The variance and regression analysis were carried out by adding the method to prepare the liquid on the substrate at three temperatures with time(96h).The results showed that there were significant changes in 57 metabolites such as 3-hydroxy carbofuran,difenoconazole,imidacloprid and profenofos in the solvent;the recovery rate of the liquid on the substrate began to change from 12h onwards.It was found that the three storage temperature conditions had different effects on different drugs.Among them,the analysis results of 12 kinds of pesticides such as 3-hydroxy carbofuran,aldicarb and aldicarb were significantly different at three different temperatures.There were 4 kinds of machine fluids on the substrate at-20℃,4℃and 25℃,respectively,and 6 and 6 pesticides showed significant linear changes(P<0.05). |
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