Testing the Uncertainty and 25 Kinds of Pesticide Residue Stability in Ambient and Cryogenic Processing of Lettuce Sample

Taken chlorpyrifos as internal standard,the uncertainty during the ambient and cryogenic processing of lettuce matrix was estimated,and t-test was applied to compare the stability of 25 kinds of pesticide during two sample processing methods,and then QuEChERS method was used in which acetonitrile was as extraction solvent,primary secondary amine (PSA) as sorbent,and pesticides were detected by gas chromatography-mass spectrometer (GC-MS).The results showed that the uncertainty was not significant different between two methods (5.2% in ambient processing and 5.4% in cryogenic milling).When the samples were processed in cryogenic milling by adding dry ice,the decomposing of pesticides could be minimized.It was found that the stability of carbaryl and propoxur would be obviously increased when the sample was processed in cryogenic milling,however,the decomposition of dichlorvos and chlorothalonil occurred was during both methods.It needs further research to investigate the factors which affect the stability of the pesticides,such as pesticide property,matrix type,and processing conditions.