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

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.

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).

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 1125 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.

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.