A 5.0 mL working solution of Fe3+ (40 lgL1) was placed into a
10 mL centrifuge tubes and mixed with 1.0 mL of 5.0 103 mol L1 ascorbic acid. After Fe3+ ions are completely reduced, the solution containing with 0.5 mL of 5.0 104 mol L1 5-Br-PADAP and 2.0 mL acetate buffer solution (pH 5.5) were added and diluted to 10.0 mL.