Dissipation kinetics, residues and risk assessment of propiconazole and azoxystrobin in ginseng and soil

摘要

The combinational fungicide suspension (11.7% propiconazole + 7% azoxystrobin), developed by Syngenta Co., Ltd., is very effective for the control of Alternaria black spot on ginseng. A simple and effective method was developed for determining propiconazole and azoxystrobin residues by high-performance liquid chromatography coupled with tandem mass spectrometry (HPLC-MS/MS). The recoveries of propiconazole ranged from 81.0% to 98.0% with relative standard deviations (RSDs) of 1.23-8.46%, while the recoveries of azoxystrobin ranged from 83.2% to 98.8% with RSDs of 3.29-9.50%. For the dissipation kinetics, the combinational fungicide was sprayed with dosage of 225g a.i.ha(-1) (1.5 times of recommended dosage) in ginseng and soil at two different locations. The dissipation kinetics followed the first-order kinetics with half-lives of 6.66-13.33days for propiconazole and 4.92-9.12days for azoxystrobin. Based on the terminal residues data, the preharvest interval (PHI) could be 35days at recommended dosage in ginseng. The dietary exposure risk was estimated by risk quotient (RQ). The result showed that the RQ value was obviously lower than RQ=1, indicating that spraying propiconazole and azoxystrobin in ginseng at recommended dosage was safe for human beings.