Residual Behavior and Dietary Risk Assessment of Fluopicolide, Its Metabolite and Propamocard on Three Leafy Vegetables

Purpose: Field trials were conducted in 10 provinces to assess the safety of applying fluopicolide + propamocarb hydrochloride to three leafy vegetables, Lactuca sativa, pakchoi and crown daisy. The residual dynamics of fluopicolide, its metabolite 2,6-dichlorobenzamide and propamocard on the vegetables was investigated, and dietary risk assessment of the three compounds was conducted. Methods: Samples were extracted with acetonitrile and purified by solid phase extraction (SPE), and the analytes were detected by ultra-high performance liquid chromatography-tandem mass spectrometry (GC-MS/MS). Results: The average recovery rates of fluopicolide, 2,6-dichlorobenzamide and propamocard were 82%–109%, 74%–103% and 76%–115%, with relative standard deviation (RSD) of 2%–13%, 1%–13% and 2%–8% in the three leafy vegetables at three spiked levels (0.01, 0.5, 30 and 70 mg/kg), respectively, and the limit of quantification was 0.01 mg/kg for all three compounds. The dissipation of fluopicolide and propamocard in L. sativa, pakchoi and crown daisy followed a first-order kinetics model. The degradation half-lives of fluopicolide on the three leafy vegetables was 3.0–3.4, 2.2–5.4, and 6.3–6.5 days, respectively, while those of propamocard were 3.3–5.5, 1.8–5.1, and 7.1 days, respectively. Fluopicolide + propamocarb hydrochloride (687.5 g/L) was sprayed three times on three leafy vegetables with a spraying interval of 7 days and safety interval of 5 days at the recommended dosage of 1 125 mL/hm2. The final residues of fluopicolide, 2,6-dichlorobenzamide and propamocard were as follows: 1.03–4.21, 0.01–0.03, and 6.71–15.10 mg/kg in L. sativa; 0.66–2.90, 0.01–0.02, and 3.49–13.80 mg/kg in pakchoi; 1.30–8.93, 0.01–0.04, and 5.18–29.80 mg/kg in crown daisy, respectively. All residue levels were lower than the maximum residue limit (MRL). The risk assessment results showed that the acute and chronic dietary risk of fluopicolide, 2,6-dichlorobenzamide and propamocard were all lower than 100% for populations of different ages and genders, indicating an acceptable level. Conclusion: This study provides the technical basis for understanding the dissipation pattern and dietary risk assessment of fluopicolide, 2,6-dichlorobenzamide and propamocard on L. sativa, pakchoi and crown daisy and offers scientific guidance for safe application of fluopicolide and propamocard to leafy vegetables.