*4.1. Samples, Chemicals, and Reagents*

In total, 52 fish samples (20 tilapia, 16 milkfish, and 16 perch samples) were collected from Taiwanese aquafarms in major production areas located in Yunlin, Chiayi, Tainan, Kaohsiung, and Pingtung over June 2018 to October 2019 (Figure S3). As surveyed in 2018 by Fisheries Agency of Taiwan, these fish were bred on a large scale in Taiwan [3]. From the obtained fish samples (each weighing ~1200 g and comprising 2 fish), fish muscles were extracted, followed homogenization and storage at −20 ◦C until analysis. In the analyses executed in this study, three replicates were extracted from each composite sample to determine each tested compound's average concentration.

Sigma-Aldrich (St. Louis, MO, USA) was the source of the analytical compound standards of the 12 sulfonamides used in this study, namely sulfamethazine, sulfathiazole, sulfamethoxazole, sulfamethoxypyridazine, sulfadoxine, sulfamerazine, sulfaethoxypyridazine, sulfameter, sulfamonomethoxine, sulfadimethoxine, sulfapyridine, and sulfadiazine (all >95.0% purity). Moreover, those of organophosphorus insecticide, namely chlorfenvinphos, chlorpyrifos, diazinon, fenitrothion, fenthion, malathion, methacrifos, methamidophos, methidathion, phoxim, profenophos, pyrazophos, and trichlorfon (all >97.0% purity) were from Dr. Ehrenstorfer GmbH (Augsburg, Germany). In addition, fenamiphos (99.5% purity) were obtained from Bayer CropScience AG (Monheim, Germany), formothion (96.0% purity) from Sandoz India (Mumbai, India), iprobenfos (99.6% purity) from Sigma-Aldrich, and prothiofos (95.5% purity) and triazophos (99.5% purity) from ChemService (West Chester, PA, USA). Merck (Darmstadt, Germany) was the source of

chromatography-grade acetone, anhydrous sodium sulfate (ASS), methanol (MeOH), formic acid (FA), ethyl acetate, n-pentane, n-hexane, and acetonitrile (ACN). We also purchased, from Agilent Technologies (Wilmington, DE, USA), 15-mL QuEChERS cleanup tubes (Agilent SampliQ QuEChERS EN fatty dispersive-SPE kit, p/n 5982-5156) and a QuEChERS extraction salt packet (Agilent SampliQ QuEChERS EN Extraction kit, p/n 5982-5650; mixture constituents: 1 g sodium citrate, 1 g NaCl, 0.5 g citric acid disodium salt, and 4 g anhydrous magnesium sulfate).
