Simultaneous determination of trace lead and cadmium in water samples by adsorptive stripping voltammetry using gallic acid as a selective chelating agent

This work describes a procedure for the simultaneous determination of cadmium and lead in some food and water samples using an adsorptive stripping voltammetric method. The method is based on the adsorptive accumulation of 2,3,4-trihydroxybenzoic acid (gallic acid (GA)) complexes of these elements onto a hanging mercury drop electrode, followed by the reduction of the adsorbed species. Optimal analytical conditions were found to be 0.10 M borate buffer (pH 6.2), 2.5 × 10⁻⁵ M GA, an accumulation potential of – 0.1 V (Versus SCE), an accumulation time of 80 s and a scan rate of 60 mV/s. The peak current is proportional to the concentration of lead and cadmium over the range of 0.50–70.00 ng mL⁻¹ and 0.20–35.00 ng mL⁻¹, respectively, and the detection limit is 0.014 ng mL⁻¹ and 0.011 ng mL⁻¹ for lead and cadmium, respectively, for a 80 s adsorption time. The propose method was applied to the determination of lead and cadmium in water and food samples with satisfactory results.