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Sample preparation methods for Multiresidue Analysis of pesticides by GC/MS in vegetables

Sample preparation is one of critical steps in Multiresidue Analysis of Pesticides. In this paper, the sample preparation methods for Multiresidue Analysis of Pesticides in vegetables were studied by using cucumber and leek was used as materials. Results show that the optimum sample preparation conditions for normal vegetables were as follows: The ratio of acetonitrile to water was 3∶1 during C18 solid-phase extraction. The pH values prior to homogenization and liquid extraction were 7 and 5, respectively. The matrix interference was complex when the samples as chinese chive were prepared by using normal method. Treatment of adding small amount of phosphoric acid before homogenizing could effectively abate matrix interference, which lead to the recovery of more than 90% pesticides among 76 different type of pesticides detected range from 70% to 120%.