*2.4. Extraction and Purification of Fluopyram*

The residual analysis of fluopyram in soil and scallion samples was carried out based on the QuEChERS EN method for rapid analysis. Soil (5 g) or scallion samples were weighted and placed into 50 mL conical tubes. Thereafter, 20 mL of acetonitrile was added for extraction and samples were shaken at 1300 rpm for 3 min using a high-speed shaker (2010/Grinder, SPEX® Sample Prep, Metuchen, NJ, USA). Subsequently, QuEChERS extract pouches (4 g of MgSO4, 1 g of NaCl, 1 g of sodium citrate dehydrate, and 0.5 g of sodium hydrogencitrate sesquihydrate) were added, followed by shaking at 1300 rpm for 90 s. After centrifugation at 4000 rpm for 5 min (Combo-408, Hanil Science Inc., Gimpo, Republic of Korea), a 1 mL aliquot of the supernatant was transferred into a d-SPE tube containing 150 mg of MgSO4 and 25 mg of PSA for purification. After shaking at 1300 rpm for 90 s and centrifugation at 13,000 rpm for 3 min, the supernatant was filtered through a 0.2 μm syringe filter. Thereafter, the filtrate (800 μL) was mixed with acetonitrile (200 μL). A 5 μL aliquot of the mixture was injected into a high-performance liquid chromatography-tandem mass spectrometer (HPLC-MS/MS).
