Sodium tetrakis [3,5-bis(trifluoromethyl)phenyl] borate (NaTFPB), 2-nitrophenyl octyl ether (NPOE), high-molecular-weight poly (vinyl chloride) (PVC), tetrahydrofuran (THF), calcium ionophore IV, 4-aminoantipyrine, perfluorinated resin solution (Nafion 1100 W-5 wt%) and ethyl alcohol (anhydrous) were purchased from Sigma-Aldrich. Silica was purchased from Cabot. N-methyl-2-pyrrolidone (NMP) and iron nitrate were obtained from Macklin. All aqueous solutions were prepared with ultrapure water (>18.2 MΩ cm).
The original soil samples were collected from five different locations near Guangzhou Higher Education Mega Center. The collected 10 g soil samples were mixed with 70 mL ultrapure water and ultrasonicated for 1 h. The resulting mixture was centrifuged (10 min at 10,000 rpm) to collect the solution. Finally, the obtained solution was stored at 4 °C in a refrigerator for use. In addition, five different brands of mineral water were randomly purchased from the market for testing.
The original soil samples were collected from five different locations near Guangzhou Higher Education Mega Center. The collected 10 g soil samples were mixed with 70 mL ultrapure water and ultrasonicated for 1 h. The resulting mixture was centrifuged (10 min at 10,000 rpm) to collect the solution. Finally, the obtained solution was stored at 4 °C in a refrigerator for use. In addition, five different brands of mineral water were randomly purchased from the market for testing.