| As an important oil and economic crop in China,peanut is well received by consumers for it could be eaten fresh,used to extract oil,and also be processed into peanut products.As a kind of edible oil,peanut oil is an important oil source for people.In cooking,it can also make food more flavorful and nutritious.In recent years,as a result of abuse of pesticide,the quality and safety risks of peanuts have become an increasingly important issue.Gas chromatography-tandem mass spectrometry(GC-MS/MS)combined with automatic QuEChERS pre-treatment equipment is an effective method for the detection of multi-pesticide residues.Thus,a rapid method for simultaneous determination in peanut and peanut oil by gas chromatography-tandem mass spectrometry was established.For peanuts,the detection method of 297 pesticides was established.The pretreatment parameters was optimized by comparing the spiked recovery obtained from different acidity of extract solvents,different volumes of extract solvents,different buffer saltsand different purification combinations.In the optimized conditions,2 g samples were soaked with 2 m L ultrapure water,the pesticides in the peanuts were extracted using acetonitrile containing 1% acetic acid,salted out using 4 g anhydrous magnesium sulfate and 1 g sodium acetate.Then the solution was purified using 100 mg PSA+200 mg C18+100 mg Z-Sep+ by automatic QuEChERS pre-treatment device combined vortex vibration with centrifuge device through a purification tube.The tube includes inner tube,outer tube and a filtration membrane.Pesticides were separated on an HP-5MS UI capillary column using temperature programming,determined by GC-MS/MS with positive ion multiple mode and quantified by external standard method.Matrix effects were evaluated for the established method,the results of the matrix effects showed that 25.25% of pesticides exhibited enhancement matrix effects,2.02% of pesticides exhibited inhibition matrix effects and 72.72% of pesticides exhibited weak matrix effects.Matrix-matched standard curve was used to reduce the matrix effect on pesticide residues detection.Methodological verifications were evaluated for the established method,the results showed that all the pesticides have a good linearity in the corresponding range,with the correlation coefficients(R2)greater than 0.995.The limits of detection(LOD)were in the range of 1-5 μg/kg and the limits of quantitation(LOQ)were 2-10 μg/kg.At the four spiked levels of 10,20,50 and 100 μg/kg,the recoveries of 297 pesticides were 72.7-116.0%,71.9-117.1%,73.2-111.5% and 71.5-119.7%,respectively.The relative standard deviations(RSDs)were 0.9-14.9%,0.7-15.4%,0.6-14.4% and 0.4-14.7%,respectively.For peanut oil,the detection method of 172 pesticides was established.The optimized conditions were 2 g samples soaked with 3 m L ultrapure water,then extracted using acetonitrile,salted out using 4 g sodium acetate.Then the solution was purified using 200 mg PSA+200 mg C18 by automatic QuEChERS pre-treatment device.Pesticides were separated on an HP-5MS UI capillary column using temperature programming,determined by GC-MS/MS with positive ion multiple mode and quantified by external standard method.Matrix effects were evaluated for the established method,the results of the matrix effects showed that 74.42% of pesticides exhibited enhancement matrix effects,5.23% of pesticides exhibited inhibition matrix effects and 20.35% of pesticides exhibited weak matrix effects.Matrix-matched standard curve was used to reduce the matrix effect on pesticide residues detection.The results showed that the limits of detection(LOD)were in the range of 1-5 μg/kg and the limits of quantitation(LOQ)were 2-10 μg/kg.At the three spiked levels of 10,50 and 100 μg/kg,the average recoveries of 172 pesticides were 70.1-112.8%,72.6-114.3%,and 71.8-114.9%,respectively.The relative standard deviations(RSDs)were less than 15%.The proposed method was applied to the detection of 8 batches of peanut samples purchased from local supermarket.The results demonstrated that 6 batches of peanut samples were detected with pesticide residues and 17 pesticides were detected in total.The concentration of dicrotophos was the highest among all pesticides reaching 34.67 μg/kg.At the same time,the established method was applied to the detection of 10 batches of peanut oil samples.The results showed that 4 batches were detected with pesticide residues,15 pesticides were detected in all samples.In a word,the developed method was simple,rapid,sensitive and automatic,and suitable for the rapid detection of pesticide residues in peanuts and peanut oil. |
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