Simultaneous determination of lead and tin in biological and environmental materials by differential pulse cathodic voltammetry on a glassy carbon mercury film electrode

A method involving a nonelectrolytic accumulation of a tin(IV)–catechol complex, followed by differential pulse cathodic voltammetric reduction of the tin‐catechol complex and the direct reduction of lead(II) ions, is described for the simultaneous determination of trace amounts of tin and lead on a glassy carbon mercury film electrode. The selective reaction of tin with catechol enables adequate resolution of its peak from the lead response. The resulting peaks which appeared at −0.39V, −0.50V and −0.66V (vs. Ag/AgCl), correspond to the reduction of Sn^IV, Pb^II and Sn^II, respectively. The lowest detectable concentrations in 0.10 M acetate buffer electrolyte (pH between 4.2 and 4.7) containing 5 × 10⁻⁴M catechol with an accumulation period of 300s are l.0μg L⁻¹ and 0.5 μg L⁻¹ for lead and tin, respectively. The linear concentration range for lead and tin in the presence of 20 μ L⁻¹ of either element are 0–4 mg L⁻¹ and 0‐34 μg L⁻¹, respectively. The simultaneous determination of both elements was accomplished in solutions containing up to 4000‐fold more lead than tin. The method is successfully demonstrated for the reliable simultaneous determination of lead and tin in some biological and environmental materials.