Optimization of experimental parameters. (a) pH of acetate buffer, preconcentration (b) potential and (c) time, square wave (d) period, (e) amplitude and (f) increment. ASV performed in 10 μM Pb acetate buffer (0.2 M). The optimal parameters we selected are as follows: pH 5.5 acetate buffer, −0.8 V and 5 min for preconcentration, and 50 ms, 50 mV and 8 mV for period, amplitude and increment, respectively.