Abstract:

To establish an analytical method for the residue of fenpyroximate in wolfberry and to study the residue behavior of fenpyroximate in wolfberry，the samples were extracted with acetonitrile，detected by ultra-performance liquid chromatography-tandem mass spectrometry，and quantified by the matrix-matched external standard method. The results showed that good linearity was achieved in the range of 0.000 2-0.040 0 mg·L^-1. At the spiked levels of 0.01，0.50 and 2.00 mg·kg^-1，the average recoveries of fenpyroximate in dried and fresh wolfberry ranged from 78% to 105%，with a maximum relative standard deviation of 9.4%，and the limits of quantification was 0.010 mg·kg^-1. The degradation test indicated that fenpyroximate degraded rapidly in fresh wolfberry at all test sites，and the degradation curves could not be fitted，while the half-lives in dried wolfberry were 3.9 and 4.3 d，respectively，in Yinchuan of Ningxia and Taiyuan of Shanxi， indicating that fenpyroximate is an easily degradable pesticide. Under the recommended application conditions，the residues of fenpyroximate in fresh wolfberry and dried wolfberry samples with a harvest interval of 7 d were <0.010 mg·kg^-1 and <0.010-0.045 mg·kg^-1，respectively. The maximum residue levels were all below the maximum residue limits established in China. Therefore，a pre-harvest interval of 7 d is recommended.

Key words: wolfberry, fenpyroximate, residue, degradation dynamics