Measuring the Residual Levels of Fenpyroximate and Its Z-Isomer in Citrus Using Ultra-High-Performance Liquid Chromatography-Tandem Mass Spectrometry and Assessing the Related Dietary Intake Risks.

Fenpyroximate is an efficient, broad-spectrum phenoxypyrazole acaricide which is used for controlling various mites. In this study, we measured the levels of terminal fenpyroximate residues in citrus fruits, and estimated the dietary intake risks posed by fenpyroximate. To this end, a QuEChERS analytical method was used in combination with ultra-high-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) to determine the residual levels of fenpyroximate and its Z-isomer (Z-fenpyroximate) in citrus fruits collected from 12 fields under good agricultural practices (GAPs). The average recoveries of fenpyroximate in whole fruits and citrus flesh were 104-110% and 92-109%, respectively, with corresponding RSDs of 1-4% and 1-3%. The average recoveries of Z-fenpyroximate were 104-113% and 90-91%, respectively, with RSDs of 1-2% in both cases. Each limit of quantification (LOQ) was 0.01 mg kg. Fifteen days after application with 56 mg kg, the terminal residues of fenpyroximate in whole fruits and citrus flesh were <0.010-0.18 mg kg and <0.010-0.063 mg kg, respectively; the corresponding values for total fenpyroximate (the sum of fenpyroximate and Z-fenpyroximate) were <0.020-0.19 and <0.020-0.053 mg kg. The levels of terminal fenpyroximate residues in citrus fruit were less than the maximum residue limits (MRLs) specified in all the existing international standards. In addition, the risk quotients RQ and RQ were both less than 100%, indicating that the long-term and short-term dietary intake risks posed to Chinese consumers by fenpyroximate in citrus fruit are both acceptable after a 15-day harvest interval.