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 adsorptivedifferential pulse stripping method for the determination of lead is proposed. The procedureinvolves an adsorptive accumulation of lead on a hanging mercury drop electrode (HMDE) inthe presence of xylenol orange, followed by reduction of adsorbed lead by voltammetric scanusing differential pulse modulation. The optimum experimental conditions are: xylenol orangeconcentration 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 currentis proportional to the concentration of lead over range of 0.03-0.65 μg mL-1, and the detectionlimit 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 watersamples with satisfactory results.