A New QuEChERS Method For Determination Of Pesticide Residues In Cabbage Matrix

For the stable production of crops in modern agriculture,the use of pesticides is indispensable.However,the excessive application of pesticides may leave harmful residues in the soil,water,plants,and various foodstuffs,which are causing serious detrimental effects on human health and other non-target living organisms.The maximum residue limits for pesticides have been regulated by many countries and organizations to protect human health.Because cabbage is one of the most consumed vegetables in Asia,monitoring these compounds in cabbage is extremely important to ensure that only permitted levels of pesticide are consumed.However,there was no report about imidaclothiz and cycloxaprid determination method in cabbage,and few reports have focused on the pesticide residues in dehydrated vegetables.As one of the most common sample preparation methods for pesticides,QuEChERS(quick,easy,cheap,effective,rugged,and safe)can be highlighted owing to its inherent properties,including few steps,low organic solvent consumption,suitability for multi-pesticide residue analysis,and so forth.The objective of the study was to develop a modified QuEChERS method for determining neonicotinoid and carbamate pesticides in cabbage.The main research results were as follows:1.A modified QuEChERS method was developed and combined with ultra-performance liquid chromatography-tandem mass spectrometry(UPLC-MS/MS)to analyze 8 neonicotinoid insecticides in Chinese cabbage.Herein,acetonitrile served as the extraction solvent.Anhydrous sodium sulfate replaced the traditional anhydrous magnesium sulfate in the phase partition process to eliminate the influence of salt caking and heat release.Primary secondary amine(PSA)and graphitized carbon black(GCB)were selected as dispersive-solid phase extraction sorbents according to the cleanup efficiency evaluated by post-column infusion.The method showed good sensitivity with the limits of quantification(LOQs)below 1.0 μg/kg for 8 analytes.The average recoveries ranged from 79.0～108.4% for three fortification levels,and the matrix effect could be ignored.For the tested samples,six neonicotinoids were detected,while cycloxaprid and imidaclothiz were not.The developed analytical method provided a powerful tool for monitoring neonicotinoid insecticide residues in Chinese cabbage.2.This research developed and validated a modified QuEChERS method combined with u UPLC-MS/MS to determine 19 kinds of neonicotinoid and carbamate pesticides in freeze-dried cabbage.Herein,acetonitrile/water(v/v =2:1)was selected in the extraction step.Meanwhile,4.0 g anhydrous magnesium sulfate and 1.0 g sodium chloride were applied to the partitioning step.Dispersive solid-phase extraction sorbents were selected,and liquid chromatography conditions were further optimized for dealing with the matrix effect.The limits of quantification ranged from 1.0 to 10.0 μg/kg.The validation results were acceptable,with average recoveries of 78.7～114.0% and relative standard deviations(RSDs)below 14.2%.The research found that the method recoveries were closely related to the volume proportion of water in the extractant.Finally,the developed method was applied to real freeze-dried cabbages and four pesticides(propamocarb,imidacloprid,acetamiprid,and thiacloprid)were detected in 6 batches of samples.