Residue level, persistence and safety of spirodiclofen-pyridaben mixture in citrus fruits

A sample pretreatment method was established to analyze the residues of spirodiclofen-pyridaben mixture in citrus fruits using ultra-performance liquid chromatography coupled with tandem mass spectrometry (UPLC-MS/MS). A mixed formulation of 27% spirodiclofen-pyridaben suspension concentrates was sprayed on citrus in field conditions at 1- or 1.5-fold recommended dose. The dissipation of spirodiclofen-pyridaben mixture in whole citrus follows the first-order dynamic equation with half-lives of 4.56-13.1 d at three locations. Residues of spirodiclofen-pyridaben mixture are mainly distributed in peel, followed by whole citrus and pulp. Risk assessment showed that spirodiclofen exerts much higher chronic risk than acute risk, while pyridaben exerts relatively lower chronic risk than acute risk. However, both chronic and acute risks of this mixed pesticide in citrus fruits are relatively low to humans irrespective of dosages, frequency of applications, and pre-harvest intervals. The residue dynamics information will support label-claim for use of this mixed pesticide in citrus fruits. (C) 2015 Elsevier Ltd. All rights reserved.