Determination of trace amounts of lead by adsorptive cathodic stripping voltammetry in the presence of xylenol orange

Lead forms the complexes with xylenol orange in the basic solution. An adsorptive differential pulse stripping method for the determination of lead is proposed. The procedure involves an adsorptive accumulation of lead on a hanging mercury drop electrode (HMDE) in the presence of xylenol orange, followed by reduction of adsorbed lead by voltammetric scan using differential pulse modulation. The optimum experimental conditions are: xylenol orange concentration of 0.20 μg mL-1, pH 10.5, accumulation potential of -900 mV versus Ag/AgCl, accumulation time of 200 s, scan rate of 10 mV s-1 and pulse height of 100 mV. The peak current is proportional to the concentration of lead over range of 0.03-0.65 μg mL-1, and the detection limit is 0.01 μg mL-1. The relative standard deviations (n=3) for 0.10 μg mL-1 lead is 0.86%, respectively. The proposed method was applied to the determination of lead in hair and water samples with satisfactory results.