Abstract: This study established a multi-residue analytical method for the simultaneous determination of penthiopyrad (including its metabolite PAM) and triflumizole (including its metabolite FM-6-1) in cucumber using a quick, easy, cheap, effective, rugged, and safe (QuEChERS) pretreatment method coupled with ultra-high performance liquid chromatography-triple quadrupole tandem mass spectrometry (UPLC-MS/MS). The method demonstrated excellent linearity (R² > 0.999) within the concentration range of 0.1–100 ng/mL, with limit of quantification (LOQ) of 0.01 mg/kg for all target compounds. At three spiked concentration levels of 0.01, 0.2, and 1.0 mg/kg, both the mean recovery rates and relative standard deviations (RSDs) for penthiopyrad, triflumizole and their metabolites met the requirements of pesticide residue analysis. Standardized field trials were conducted from 2023 to 2024 across 12 major cucumber production regions in China (6 greenhouses and 6 open-field sites). The 28% penthiopyrad-triflumizole emulsion in water (EW) was applied three times at 84 g a.i./hm² with 7-day intervals during the initial occurrence period of cucumber powdery mildew. In samples collected 2–3 days after application, penthiopyrad and triflumizole residues ranged from 0.03 to 0.04 mg/kg and from 0.02 to 0.03 mg/kg, respectively. The dissipation of penthiopyrad and triflumizole followed first-order kinetics with half-lives of 1.1–1.5 and 1.1–1.9 days, respectively. Dietary risk assessment based on Chinese dietary patterns and pesticide registration data revealed that the national estimated daily intake (NEDI) for penthiopyrad and triflumizole were 0.228 7 and 0.109 7 mg with risk quotient (RQ) of 3.6% and 4.4%, respectively, both significantly below the safety threshold of 100%. The residue levels of penthiopyrad and triflumizole in cucumber under current usage conditions pose negligible health risks to consumers. This study provides scientific evidence supporting the safe use and dietary risk assessment of penthiopyrad and triflumizole.

Key words: cucumbers; penthiopyrad; triflumizole; metabolites; pesticide residues; dietary risk