Residue Profiling Of Metrafenone In Grapes Through LC-MS/MS Analysis

Abstract

Grapes (Vitis vinifera L.) are highly vulnerable to fungal infections, necessitating extensive fungicide use, which raises concerns regarding pesticide residues, food safety, and export compliance. Metrafenone, a fungicide widely used to manage powdery mildew, was evaluated for its residue behavior and dissipation kinetics in grapes using a validated LC-MS/MS method. Field experiments were conducted on Thompson Seedless grapes at the ICAR-NRC for Grapes, Pune, with single (100 mL/acre) and double (125 mL/acre) dose applications under randomized block design. Grape samples were collected at multiple intervals post-application and analyzed following ethyl acetate-based extraction and LC-MS/MS quantification. Method validation demonstrated excellent linearity (R² > 0.99), recoveries within 85–90%, and acceptable LOD (3 ng/g) and LOQ (10 ng/g). Residue dissipation followed first-order kinetics with strong model fit (R² = 0.992 for single dose; R² = 0.991 for double dose). The half-life (DT₅₀) of metrafenone was 13 days at the single dose and 17 days at the double dose. Residue concentrations declined from 11.33 mg/kg and 14.93 mg/kg (initial deposits) to 0.03 mg/kg and 0.09 mg/kg, respectively, within 60 days. Importantly, residues dropped below the EU Maximum Residue Limit (7 mg/kg) within 19 days, aligning with the Pre-Harvest Interval (PHI) stipulated in Grape Annexure 5 (2024). The study highlights that while metrafenone dissipates effectively in grapes, persistence is dose-dependent. Adherence to recommended application rates and PHIs is essential to ensure compliance with international MRLs, safeguard consumer health, and maintain export suitability. These findings provide valuable insights for integrated residue management strategies supporting sustainable viticulture.