Electrochemical micro-extraction of lead (II) at a hydroxylapatite modified platinum electrode

A simple approach for increasing the sensitivity and selectivity for the detection of lead (II) species in water is presented. The technique is based on two steps: (1) micro-extraction (uptake step) of lead (II) by simply incubating HAP modified platinum electrode, at open-circuit potential conditions, into a solution containing the heavy metal for 30 min; (2) the electrode is transferred from the analyte solution to an electrochemical cell (release step) for successive voltammetric determinations. Surprisingly, cyclic voltammetric measurements showed an anodic peak characteristic of oxidation of metallic lead to form lead (II) at −0.075 V. The reversed scan, showed a cathodic peak at −0.35 V, differential pulse measurements performed on the HAP electrode showed that the anodic peak exhibit a good linear concentration dependence in the range 7 × 10−7–5.6 × 10−6 M. The detection limit was estimated to be 5 × 10−7 M. The analytical performances of the extraction method has been explored by studying the incubating time, and effect of interferences due to other ions. On the other hand, EDAX and Electrochemical Impedance Spectroscopy (EIS) measurements performed on HAP films confirmed the adsorption of the heavy metal on the polymeric film due to the extraction process.