Determination, residue analysis, risk assessment and processing factor of pymetrozine and its metabolites in Chinese kale under field conditions.

A simple determination method for pymetrozine and its metabolites in Chinese kale was developed using liquid chromatography with tandem mass spectrometry. The method had good linearity (R2  > 0.99), accuracy (recoveries of 73.2-94.1%) and precision (relative standard deviation of 2.5-9.8%). Field results showed that half-lives of pymetrozine were 3.0-4.1 d in Chinese kale, and terminal residue concentrations were all below the United States Environmental Protection Agency's maximum residue limit (250 μg/kg) at harvest. Owing to risk quotient <100%, pymetrozine is unlikely to give rise to vital health concerns to humans following the recommended application guidelines. Moreover, effects of home processing on pymetrozine residues in Chinese kale were monitored. The processing factor values of four processes were between 0.19 and 0.60, which indicated that the used processes could remove pymetrozine residues from Chinese kale, especially pickling after washing process. The data could provide guidance to safe and reasonable use of pymetrozine and help Chinese governments establish a maximum residue limit for pymetrozine in Chinese kale.