*2.5. Instrumental Conditions for HPLC-MS/MS Analysis*

A Shimadzu Nexera HPLC coupled to a Shimadzu LCMS-8045 triple quadrupole mass spectrometer (Shimadzu Corp., Kyoto, Japan) was used for the analysis of fluopyram in soil and scallion samples. The chromatographic separation was achieved using a Cadenza C18 column (150 mm × 2.0 mm, 3 μm, Imtakt, Portland, OR, USA) at 40 ◦C with a 0.3 mL/min flow rate. The mobile phase was composed of water (Solvent A) and methanol (Solvent B), containing 0.1% formic acid and 10 mM ammonium formate, respectively. The gradient system of the mobile phase was programmed at a 0.3 mL/min flow rate as follows: 0–2 min, 20% B; 2–5 min, 20–80% B; 5–10 min, 80% B; 10–13 min, 80–20% B; 13–17 min, 20% B. The injection volume was 5 μL. MS/MS detection was achieved in positive ion mode with electrospray ionization (ESI). The source parameters were optimized as follows: desolvation line temperature, 250 ◦C; interface temperature, 300 ◦C; heat block temperature, 400 ◦C; nebulizing gas, 3 L/min; heating gas (air), 10 L/min; drying gas (N2), 10 L/min. In positive ion mode, *m*/*z* 396.8 was detected as the precursor ion, and *m*/*z* 173.0 and 144.9 were selected as the quantifier and qualifier at 30 and 50 V of collision energies, respectively. Instrument control, data acquisition, and processing were performed by the Shimadzu LabSolutions software package (ver. 5.97, Shimadzu Corp., Kyoto, Japan).
