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 -0.39 V, -0.50 V and -0.66 V (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 x 10(-4) M catechol with an accumulation period of 300 s are 1.0 mu g L(-1) and 0.5 mu g L(-1) for lead and tin respectively. The linear concentration range for lead and tin in the presence of 20 mu g L(-1) of either element are 0-4 mg L(-1) and 0-34 mu g L 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.