Residue Dynamics of Dimethomorph in Scallion
CUI Shu-hua1,2, WANG Kai-yun1, QIAN Jia-liang2, ZHANG Li-dong2, LIU Jin-feng2, WU Guang-ming2(1.College of Plant Protection, Shandong Agriculture University, Tai'an 271018, Shandong, China; 2.Inspection and Quarantine Technology Center of Linyi Exit/Entry Inspection and Quarantine Bureau, Linyi 276034, Shandong, China)
Gas chromatography-mass spectrum (GC-MS) was used in the field residue dynamics study and final residues of dimethomorph in scallion in spring. Scallion samples were extracted with acetonitrile and the extracts were cleaned up by SPE column filled with sax tandem psa, followed by determination using gas chromatography-mass spectrum with selected ion monitor (GC/MS/SIM). The fortified recovery at level of 0.01-0.1 mg/kg ranged from 96.2-105.7%, with relative standard deviation of 3.5-5.7%. The limit of detection of dimethomorph by the method was 0.02 ng, and the limit of quantification for dimethomorph in scallion was 0.002 mg/kg. The field residue dynamics study showed that the half-lives of dimethomorph in scallion was 3.5 d. When the scallion was sprayed two to three times with dimethomorph 50% WP of 300 g a.i./ha and 600 g a.i./ha, at the 7th, 14th and 21th day after the last application, the final residues of dimethomorph in scallion were 0.0094-0.681 mg/kg, which were below the MRL in Japan.