Determination Of 57 Pesticide Residues In Cucumber By Optimized QuEChERS-UPLC-MS/MS

Cucumber(Cucumis sativus L.)is an annual herbaceous plant of Cucurbitaceae.It is native to northern India and widely cultivated in the province of Hebei,Shandong,Henan,Anhui,and Hubei province of China.In recent years,with the development of planting techniques,the cultivation mode of cucumber has gradually developed from open field cultivation to early spring greenhouses,autumn extension greenhouses,solar greenhouses,and winter warm greenhouses,which allows people to eat fresh and delicious cucumber all year round.At present,there are more than 100 kinds of cucumber pests and diseases are founded in cucumber.The most serious plant disease and insect pests are downy mildew,powdery mildew,bacterial angular spot,target spot,aphids,whitefly,Liriomyza sativae,thrips and meloidogyne incognita.With the advancement of specialized planting models,the problem of continuous cropping resulting that the more serious diseases and insect pests were occuerd in sheds.In order to ensure the quality and yield of cucumbers,farmers often increase the amount and frequency of pesticides,resulting the problem of pesticide residues on cucumbers was more serious.In addition,cucumber can be used as fruis,which lacked of high-temperature cooking process and increased the risk of exposure to pesticide residues on cucumbers.Food safety has received more and more attention from people.And it was necessary to find a rapid,simple and accurate method to monitor the multi-residue of pesticides in cucumber.Based on the traditional QuEChERS pretreatment method combined with ultra performance liquid chromatography-tandem mass spectrometry(UPLC-MS/MS),this study established a pesticide residue analysis method for 57 kinds of pesticides on cucumbers and monitored the residue on cucumbers in major supermarkets and farmers'markets in Tai'an city.The details are as follows:1.The pretreatment method of QuEChERS using PSA and GCB as purifying agents,optimizing their dosage and combined with ultra performance liquid chromatography-tandem mass spectrometry(UPLC-MS/MS).An ESI ion source,positive ion mode and multi-reaction monitoring(MRM)method was established in combination with ultra-high performance liquid chromatography-tandem mass spectrometry(UPLC-MS/MS)to detect 57 pesticide residues in cucumber at the same time.2.The results showed that 57 pesticides had good linearity in the concentration range of5~100?g/L.The linear correlation coefficient(R~2)is greater than 0.995.In the cucumber matrix,the average recovery was between 72.7%and 106.4%,and the RSD was between1.2%and 11.1%at the addition level of 0.01,0.1 and 1 mg/kg,which was consistent with the residue detection standard.In this study,the method has good sensitivity,accuracy and precision,and has the advantages of good linearity,high efficiency,high throughput,.It can be applied to the detection of pesticide residues in cucumber.3.The method was used to monitor the residue in major supermarkets and farmers'markets in Tai'an,the results showed that the pesticides with higher detection rate are pyraclostrobin,Kresoxim-methyl,thiamethoxam,dimethomorph,imidacloprid,metalaxyl,chlorpyrifos,fenpropathrin,cymoxanil,thiazolyl.The highest rate of over-standard is pyraclostrobin,followed by dimethomorph,chlorpyrifos,thiamethoxam,thiazolyl.4.The highest of detection and over-standard is concentrated in July,August and September5.Cucumbers samples with higher detection and exceeding the standard rate were concentrated in the farmers'market and cucumber samples collected by major supermarkets were significantly lower.