Determination of Pb in pond water. (a) ASV of pond water directly diluted 1× by acetate buffer (0.2 M, pH 5.5), with additional 0–50 ppb Pb. (b) Standard addition curve for Pb in pond water. (c) ASV of pond water spiked with 50 ppb Pb and diluted 1× by acetate buffer (0.2 M, pH 5.5). (d) Standard addition curve for pond water spiked with 50 ppb Pb. Preconcentration potential −0.8 V, time 300 s, amplitude 50 mV, period 50 ms, increment 8 mV.