*2.6. Analytical Methods*

SAs were extracted twice from the samples with an extraction solution of 10:3:1 water (containing 0.1% formic acid): acetonitrile:methanol. The extracts were analyzed using an Agilent 1260 HPLC system equipped with a 4.6 × 250 mm column (Zorbax Eclipse Plus C18, Agilent, Santa Clara, CA, USA) with photodiode array detector monitoring at 270 nm. The mobile phase was 30%:70% acetonitrile:water (containing 0.1% formic acid). TCs were extracted twice from the samples with an extraction solution of 4:1 water (containing 0.1% HCl): acetonitrile. The mobile phase consisted of acetonitrile and water (containing 0.1% HCl); AMO was extracted twice from the samples with methanol. TCs, and AMO were quantified with an Agilent 1260 HPLC equipped with a 4.6 × 100 mm column (Poroshell 120 EC-C18, Agilent) with a photodiode array detector monitoring at 270 nm and 229 nm. The recovery percentages for TC, OTC, CTC, SDM, SMX, SMZ, and AMO were 91.2%, 95.5%, 89.3%, 94.7%, 93.4%, 90.3% and 92.6%, respectively. The detection limit was 0.1 mg/L in all cases. The remaining percentage and removal percentage were computed using the following formula: remaining percentage [%] = (residue concentration/initial concentration) × 100; removal percentage [%] = [1 − (residue concentration/initial concentration) × 100]. The degradation data collected in this study fit well with first-order kinetics (i.e., *t* = −ln(*C*/*C*0)/*k*, where *C*<sup>0</sup> is the initial concentration, *C* is the concentration, *t* is the time period, *t*1/<sup>2</sup> is the half-life, and *k* is the degradation rate constant). The coefficient of determinations (*R*2) ranged from 0.923 to 0.982.
