The added paragraph is as follows: Potassium permanganate, H2SO4, potassium sodium tartrate tetrahydrate, Nessler’s reagent and NaOH were purchased from a commercial company and certified as AR purity (Guangzhou Chemical Reagent Factory, Guangzhou, China), while PPCP standards were provided by three companies. Sulfamethoxazole (SMX), Sulfadoxine (SD), Sulfachloropyridazine (SCP), Sulfamethoxypyridazine (SMP), Sulfaquinoxaline (SQX), Sulfathiazole (STZ), Doxycycline (DOX), Erythromycin (EM), Anhydroerythromycin (EA), Roxithromycin (ROX), Penicillin-G (PEN G), Clarithromycin (CAM), Norfloxacin (NOR), Oxociprofloxacin (OFL), Enrofloxacin (EFL), Flumequine (FQ), Acetaminophen (APAP), Diclofenac sodium (DCF), Naproxen (NAP), Indomethacine (IND), Metoprolol (METO), Propranolol (), Atenolol (ATL), Primidone (PRM), Carbamazepine (CMZ), and Sulpiride (SP) were obtained from the Dr. Ehrenstorfer Company in Germany. Furthermore, Sulfadimidine (SM2), Sulfadiazine (SDZ), Sulfapyridine (SP), Sulfamonomethoxine (SMM), Tetracycline (TC), Ofloxacin (OFL), Amoxicillin (AM), Dimetridazole (DMZ), Trimethoprim (TMP) were bought from the National Institute of Metrology in China, whereas Oxytetracycline (OTC), Caffeine (CF), and Diethyltoluamide (DEET) were acquired from the Toronto Research Chemicals Company in Canada.
Please add chemical reagents section and stated all chemical with brand specifications.